Alterations in Immune Responses Are Associated with Dysfunctional Intracellular Signaling in Peripheral Blood Mononuclear Cells of Men and Women with Mild Cognitive Impairment and Alzheimer's disease

Deficits in the neuroendocrine-immune network in the periphery associated with the onset and progression of mild cognitive impairment (MCI) and Alzheimer's disease (AD) have not been extensively studied. The present study correlatively examines the association between cell-mediated immune responses, stress hormones, amyloid precursor protein (APP) expression, peripheral blood mononuclear cells (PBMC), and intracellular signaling molecules in the pathophysiology of MCI and AD compared to adults. Serum APP, lymphocyte proliferation, total cholinesterase (TChE), butyrylcholinesterase (BChE) activities, cytokines (IL-2, IFN-γ, IL-6, and TNF-α), and intracellular signaling molecules (p-ERK, p-CREB, and p-Akt) were measured in the PBMCs of adult, old, MCI, and AD men and women initially and after 3 years in the same population. An age- and disease-associated decline in mini-mental state examination (MMSE) scores and lymphocyte proliferation of MCI and AD men and women were observed. An age- and disease-related increase in serum APP, cortisol levels, and TChE activity were observed in men and women. Enhanced production of Th1 cytokine, IL-2, pro-inflammatory cytokines, and suppressed intracellular transcription factors may promote the inflammatory environment in MCI and AD patients. The expression of CREB and Akt was lower in MCI and AD men, while the expression of p-ERK was higher, and p-CREB was lower in MCI and AD women after 3 years. These results suggest that changes in specific intracellular signaling pathways may influence alterations in cell-mediated immunity to promote disease progression in MCI and AD patients.

Estrogen-receptor status determines differential regulation of α1- and α2-adrenoceptor-mediated cell survival, angiogenesis, and intracellular signaling responses in breast cancer cell lines

Psychosocial stress promotes cancer pathogenesis involving angiogenesis through alterations in neuroendocrine-immune functions that may involve adrenoceptor (AR)-dependent signaling mechanisms in the brain, lymphoid organs, and cancerous cells. Various concentrations of α1- and α2- AR-specific agonists and antagonists were incubated in vitro with estrogen receptor-positive (ER +) MCF-7, and ER (-) MDA MB-231 cells to examine the secretions of VEGF-A, VEGF-C, and nitric oxide (NO), and expression of signaling molecules- p-ERK, p-CREB, and p-Akt on the proliferation of breast cancer cell lines. Cellular proliferation, VEGF-A and NO secretion, expression of p-ERK, p-CREB, and p-Akt were enhanced in MCF-7 cells treated with α1-AR agonist while VEGF-C secretion alone was enhanced in MDA MB-231 cells. Treatment of MCF-7 and MDA MB-231 cells with α2- AR agonist similarly enhanced proliferation and decreased NO production and p-CREB expression while VEGF-C secretion was decreased in MCF-7 cells and p-Akt expression was decreased in MDA MB-231 cells. α1-AR inhibition reversed cellular proliferation and VEGF-A secretion by MCF-7 cells while α2-AR inhibition reversed the proliferation of MCF-7 and MDA MB-231 cells and VEGF-C secretion by MCF-7 cells. Taken together, breast cancer pathogenesis may be influenced by distinct α-AR-mediated signaling mechanisms on angiogenesis and lymphangiogenesis that are dependent on estrogen receptor status.

Novel LIPA-Targeted Therapy for Treating Ovarian Cancer

Ovarian cancer (OCa) is the most lethal form of gynecologic cancer, and the tumor heterogeneities at the molecular, cellular, and tissue levels fuel tumor resistance to standard therapies and pose a substantial clinical challenge. Here, we tested the hypothesis that the heightened basal endoplasmic reticulum stress (ERS) observed in OCa represents an exploitable vulnerability and may overcome tumor heterogeneity. Our recent studies identified LIPA as a novel target to induce ERS in cancer cells using the small molecule ERX-41. However, the role of LIPA and theutility of ERX-41 to treat OCa remain unknown. Expression analysis using the TNMplot web tool, TCGA data sets, and immunohistochemistry analysis using a tumor tissue array showed that LIPA is highly expressed in OCa tissues, compared to normal tissues. ERX-41 treatment significantly reduced the cell viability and colony formation ability and promoted the apoptosis of OCa cells. Mechanistic studies revealed a robust and consistent induction of ERS markers, including CHOP, elF2α, PERK, and ATF4, upon ERX-41 treatment. In xenograft and PDX studies, ERX-41 treatment resulted in a significant reduction in tumor growth. Collectively, our results suggest that ERX-41 is a novel therapeutic agent that targets the LIPA with a unique mechanism of ERS induction, which could be exploited to treat heterogeneity in OCa.

Preclinical Development of Brain Permeable ERβ Agonist for the Treatment of Glioblastoma

Glioblastoma (GBM) is the most prevalent and aggressive type of adult brain tumors with low 5-year overall survival rates. Epidemiologic data suggest that estrogen may decrease brain tumor growth, and estrogen receptor beta (ERβ) has been demonstrated to exert antitumor functions in GBM. The lack of potent, selective, and brain permeable ERβ agonist to promote its antitumor action is limiting the therapeutic promise of ERβ. In this study, we discovered that Indanone and tetralone-keto or hydroxyl oximes are a new class of ERβ agonists. Because of its high activity in ERβ reporter assays, specific binding to ERβ in polar screen assays, and potent growth inhibitory activity in GBM cells, CIDD-0149897 was discovered as a possible hit by screening a library of compounds. CIDD-0149897 is more selective for ERβ than ERα (40-fold). Treatment with CIDD-0149897 markedly reduced GBM cell viability with an IC50 of ∼7 to 15 μmol/L, while having little to no effect on ERβ-KO cells and normal human astrocytes. Further, CIDD-0149897 treatment enhanced expression of known ERβ target genes and promoted apoptosis in established and patient-derived GSC models. Pharmacokinetic studies confirmed that CIDD-0149897 has systemic exposure, and good bioavailability in the brain. Mice tolerated daily intraperitoneal treatment of CIDD-0149897 (50 mg/kg) with a 7-day repeat dosage with no toxicity. In addition, CIDD-0149897 treatment significantly decreased tumor growth in U251 xenograft model and extended the survival of orthotopic GBM tumor-bearing mice. Collectively, these findings pointed to CIDD-0149897 as a new class of ERβ agonist, offering patients with GBM a potential means of improving survival.

Pharmacological inhibition of KDM1A/LSD1 enhances estrogen receptor beta-mediated tumor suppression in ovarian cancer

Ovarian cancer (OCa) is the most lethal gynecologic cancer. Emerging data indicates that estrogen receptor beta (ERβ) functions as a tumor suppressor in OCa. Lysine-specific histone demethylase 1A (KDM1A) is an epigenetic modifier that acts as a coregulator for steroid hormone receptors. However, it remain unknown if KDM1A interacts with ERβ and regulates its expression/functions in OCa. Analysis of TCGA data sets indicated KDM1A and ERβ expression showed an inverse relationship in OCa. Knockout (KO), knockdown (KD), or inhibition of KDM1A increased ERβ isoform 1 expression in established and patient-derived OCa cells. Further, KDM1A interacts with and functions as a corepressor of ERβ, and its inhibition enhances ERβ target gene expression via alterations of histone methylation marks at their promoters. Importantly, KDM1A-KO or -KD enhanced the efficacy of ERβ agonist LY500307, and the combination of KDM1A inhibitor (KDM1Ai) NCD38 with ERβ agonist synergistically reduced the cell viability, colony formation, and invasion of OCa cells. RNA-seq and DIA mass spectrometry analyses showed that KDM1A-KO resulted in enhanced ERβ signaling and that genes altered by KDM1A-KO and ERβ agonist were related to apoptosis, cell cycle, and EMT. Moreover, combination treatment significantly reduced the tumor growth in OCa orthotopic, syngeneic, and patient-derived xenograft models and proliferation in patient-derived explant models. Our results demonstrate that KDM1A regulates ERβ expression/functions, and its inhibition improves ERβ mediated tumor suppression. Overall, our findings suggest that KDM1Ai and ERβ agonist combination therapy is a promising strategy for OCa.

PELP1 inhibition by SMIP34 reduces endometrial cancer progression via attenuation of ribosomal biogenesis

Endometrial carcinoma (ECa) is the fourth most common cancer among women. The oncogene PELP1 is frequently overexpressed in a variety of cancers, including ECa. We recently generated SMIP34, a small-molecule inhibitor of PELP1 that suppresses PELP1 oncogenic signaling. In this study, we assessed the effectiveness of SMIP34 in treating ECa. Treatment of established and primary patient-derived ECa cells with SMIP34 resulted in a significant reduction of cell viability, colony formation ability, and induction of apoptosis. RNA-seq analyses showed that SMIP34-regulated genes were negatively correlated with ribosome biogenesis and eukaryotic translation pathways. Mechanistic studies showed that the Rix complex, which is essential for ribosomal biogenesis, is disrupted upon SMIP34 binding to PELP1. Biochemical assays confirmed that SMIP34 reduced ribosomal biogenesis and new protein synthesis. Further, SMIP34 enhanced the efficacy of mTOR inhibitors in reducing viability of ECa cells. SMIP34 is also effective in reducing cell viability in ECa organoids in vitro and explants ex vivo. Importantly, SMIP34 treatment resulted in a significant reduction of the growth of ECa xenografts. Collectively, these findings underscore the potential of SMIP34 in treating ECa.

Targeting PELP1 oncogenic signaling in TNBC with the small molecule inhibitor SMIP34

PURPOSE

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer. Oncogenic PELP1 is frequently overexpressed in TNBC, and it has been demonstrated that PELP1 signaling is essential for TNBC progression. The therapeutic utility of targeting PELP1 in TNBC, however, remains unknown. In this study, we investigated the effectiveness of SMIP34, a recently developed PELP1 inhibitor for the treatment of TNBC.

METHODS

To ascertain the impact of SMIP34 treatment, we used seven different TNBC models for testing cell viability, colony formation, invasion, apoptosis, and cell cycle analysis. Western blotting and RT-qPCR were used to determine the mechanistic insights of SMIP34 action. Using xenograft and PDX tumors, the ability of SMIP34 in suppressing proliferation was examined both ex vivo and in vivo.

RESULTS

TNBC cells' viability, colony formation, and invasiveness were all decreased by SMIP34 in in vitro cell-based assays, while apoptosis was increased. SMIP34 treatment promoted the degradation of PELP1 through the proteasome pathway. RT-qPCR analyses confirmed that SMIP34 treatment downregulated PELP1 target genes. Further, SMIP34 treatment substantially downregulated PELP1 mediated extranuclear signaling including ERK, mTOR, S6 and 4EBP1. Mechanistic studies confirmed downregulation of PELP1 mediated ribosomal biogenesis functions including downregulation of cMyc and Rix complex proteins LAS1L, TEX-10, and SENP3. The proliferation of TNBC tumor tissues was decreased in explant experiments by SMIP34. Additionally, SMIP34 treatment markedly decreased tumor progression in both TNBC xenograft and PDX models.

CONCLUSIONS

Together, these findings from in vitro, ex vivo, and in vivo models show that SMIP34 may be a useful therapeutic agent for inhibiting PELP1 signaling in TNBC.

Development and Characterization of Inducible Astrocyte-Specific Aromatase Knockout Mice

17β-estradiol (E2) is produced in the brain as a neurosteroid, in addition to being an endocrine signal in the periphery. The current animal models for studying brain-derived E₂ include global and conditional non-inducible knockout mouse models. The aim of this study was to develop a tamoxifen (TMX)-inducible astrocyte-specific aromatase knockout mouse line (GFAP-ARO-iKO mice) to specifically deplete the E₂ synthesis enzymes and aromatase in astrocytes after their development in adult mice. The characterization of the GFAP-ARO-iKO mice revealed a specific and robust depletion in the aromatase expressions of their astrocytes and a significant decrease in their hippocampal E₂ levels after a GCI. The GFAP-ARO-iKO animals were alive and fertile and had a normal general brain anatomy, with a normal astrocyte shape, intensity, and distribution. In the hippocampus, after a GCI, the GFAP-ARO-iKO animals showed a major deficiency in their reactive astrogliosis, a dramatically increased neuronal loss, and increased microglial activation. These findings indicate that astrocyte-derived E₂ (ADE₂) regulates the ischemic induction of reactive astrogliosis and microglial activation and is neuroprotective in the ischemic brain. The GFAP-ARO-iKO mouse models thus provide an important new model to help elucidate the roles and functions of ADE₂ in the brain.

Abstract 3986: Novel LIPA targeted therapy for treating ovarian cancer

BACKGROUND: Ovarian cancer (OCa) is the deadliest of all gynecologic cancers in the United States. Currently approved therapies have improved OCa survival for clinically localized disease, however, the majority (~90%) of patients with high-grade serous OCa (HGSOC) experience relapse with incurable metastases. There is a dire need for new therapeutic approaches. We hypothesized that the high basal endoplasmic reticulum stress (ERS) in OCa represents a critical and targetable vulnerability and may overcome the tumor heterogeneity. The objective of this project is to exploit increased ERS in ovarian cancer cells by engaging the novel target LIPA using the unique compound ERX-41.

METHODS: The utility of ERX-41 as a new therapy was evaluated using MTT and CellTiter-Glo Cell Viability Assays. We used multiple established and patient derived OCa cell lines. The effect of ERX-41 on the Cell viability of patient-derived organoids (PDO) was measured using CellTiter-Glo 3D Assay. Long term effects of ERX-41 on cell survival were measured using colony formation assays. Apoptosis was measured using Annexin V and Caspase-Glo® 3/7 Assays. Cell cycle analysis was analyzed by Flow Cytometry. Mechanistic studies were done using LIPA knockout (KO) cells, RT-qPCR, and western blotting. Status of LIPA in OCa was determined using TNMplot database. In vivo efficacy of ERX-41 was tested using both cell line derived (CDX) and patient derived (PDXs) xenografts.

RESULTS: TNM plot results showed that LIPA is highly expressed in OCa tumors compared to normal tissues and LIPA expression correlated with clinical grade. Kaplan-Meier plotter analyses of TCGA data revealed that LIPA expression is negatively correlated with overall survival in OCa patients. MTT and CellTitre-Glo assay results showed that ERX-41 significantly reduced the cell viability of both established and primary OCa cells, and PDO’s with an IC50 of ~500nM. ERX-41 treatment also significantly reduced the cell survival, increased S-phase arrest, and promoted apoptosis of OCa cells. A time course study revealed a robust and consistent induction of ERS markers (CHOP and sXBP1) in OCa cells by ERX-41 within 4h. Western blotting analyses also confirmed increased expression of ERS markers including CHOP, elF2α, PERK, and ATF4 upon ERX-41 treatment confirming that ERX-41 induces ERS. In xenograft studies, ERX-41 treatment resulted in ~66% reduction of tumor volume measured by Xenogen-IVIS. Further, in studies using PDX tumors, treatment with ERX-41 resulted in a significant reduction (~60%) of tumor volume and tumor weight.

CONCLUSION: Collectively, our results suggest that ERX-41 is a novel therapeutic agent that targets the LIPA with a unique mechanism of action and implicate ERX-41 binding to LIPA induces ER stress, and apoptosis of OCa cells. Further molecular characterization of how ERX-41 binding to LIPA induces ER stress in OCa cells is ongoing.

Citation Format: Alexia B. Collier, Suryavathi Viswanadhapalli, Tae-Kyung Lee, Kara Kassees, Karla Parra, Gaurav Sharma, Tanner Reese, Michael Hsieh, Xihui Liu, Xue Yang, Behnam Ebrahimi, Uday P. Pratap, Rahul Gopalam, Chia Yuan Chen, Scott Terry Elmore, Gangadhara Reddy Sareddy, Edward R. Kost, Jung-Mo Ahn, Ganesh V. Raj, Ratna K. Vadlamudi. Novel LIPA targeted therapy for treating ovarian cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3986.

Abstract 3408: The role of obesity in promoting the LIF/LIFR signaling in triple negative breast cancer

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer (BC) that accounts for a disproportionate amount of BC mortality. The relationship(s) between obesity and the TNBC is crucial because the obesity prevalence in the USA is on the rise. Obese patients are generally diagnosed with large primary tumors, more lymph node metastases, and obesity effects on tumor microenvironment (TME) are suspected to accelerate the development of TNBC, but the exact mechanism(s) by which this occurs remain unknown. The goal of this study is to investigate the hypothesis that obesity enhances leukemia inhibitory factor receptor (LIFR) oncogenic signaling in TNBC and to test the utility of LIFR inhibitor in blocking obesity driven progression of TNBC.

Methods: Established TNBC cell lines were co-cultured with human primary adipocytes, incubated with adipocyte conditioned media, or exposed to high glucose (HG), then treated with the LIFR inhibitor EC359. Cell viability, colony formation, and invasion assays were used to analyze the impact of obesity on TNBC cells and to test utility of EC359. RT-qPCR, Western blotting, reporter gene assays, and RNA-seq analyses were used in the mechanistic studies. Xenografts and patient-derived organoid (PDO) models were used to evaluate the effectiveness of the EC359.

Results: The cell proliferation and invasion of TNBC cells were accelerated by adipocyte conditioned media or when exposed to HG. RNA-seq and RT-qPCR analysis revealed a correlation between elevated LIFR expression and downstream LIFR signaling, including STAT3, as well as the subsequent activation of STAT3 target genes. The cell viability, colony formation, and invasion of TNBC cells under HG and adipose conditions were all markedly decreased after treatment with LIFR inhibitor EC359. Results from Western blotting demonstrated that co-culture with adipocytes or incubation with HG dramatically increased LIFR downstream signaling in TNBC model cells, and that this signaling is effectively suppressed by EC359 therapy. In addition, administration of EC359 prevented organoid proliferation that was mediated by the adipose conditioned media. Importantly, co-implantation of adipocytes greatly increased the growth of the TNBC xenograft tumor; however, therapy with EC359 significantly reduced the growth of TNBC caused by adipocyte co-implantation.

Conclusions: Collectively, these findings suggest that obesity conditions promote the activation of LIF/LIFR pathway, which in turn enhances TNBC cell proliferation. The LIFR inhibitor EC359 may be employed as a new therapeutic drug to treat obesity driven TNBC and LIF/LIFR axis represents a potential therapeutic target for obesity driven TNBC.

Citation Format: Lois Randolph, Alondra Rodriguez Sanchez, Logan Blankenship, Uday P. Pratap, Xue Yang, Durga Meenakshi Panneerdoss, Swapna Konda, Bindu Santhamma, Gangadhara R. Sareddy, Manjeet K. Rao, Edward R. Kost, Rajeshwar R. Tekmal, Hareesh B. Nair, Ratna K. Vadlamudi, Suryavathi Viswanadhapalli. The role of obesity in promoting the LIF/LIFR signaling in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3408.

Abstract 4966: Targeting LIF/LIFR autocrine loops with EC359 in ovarian cancer: A novel LIFR targeted therapy

Background: Of all gynecologic cancers, ovarian cancer (OCa) has the highest mortality rates. Nearly 90% of patients who receive standard surgical and cytotoxic treatment experience disease recurrence. Leukemia inhibitory factor (LIF) and its receptor LIFR are implicated in the progression of several cancers. A knowledge gap exists on whether LIF/LIFR plays a role in the evolution of OCa. We recently developed EC359, a first-in-class LIFR inhibitor. Here, we examined whether autocrine loops of LIF/LIFR contribute to OCa progression and tested the utility of EC359 as a potential targeted therapy.

Methods: Eighteen different OCa model cells, both established and primary, were used to profile the expression of LIF and LIFR. Cell viability, colony formation, apoptosis, and reporter assays were used to assess EC359 impact on OCa cells. Mechanistic studies were carried out using RNA-seq and RT-qPCR analysis. Using cell-based xenografts, syngeneic xenografts, patient derived organoids (PDO), and patient derived xenograft (PDX) models, the effectiveness of LIFR inhibitor EC359 as a targeted therapy was examined.

Results: Kaplan-Meier survival analysis (KMplot) revealed increased expression of LIF and LIFR was linked to poor progression-free survival in OCa patients. The levels of LIF and LIFR were considerably greater in OCa chemotherapy non-responders than responders. We validated the existence of LIF/LIFR autocrine signaling using 18 distinct OCa cells. Treatment with the LIFR inhibitor EC359 dramatically decreased OCa cell viability, cell survival and increased apoptosis, with an IC50 of 5 to 50 nM. The activation of STAT3, mTOR, AKT, and p42/44 MAPKs as well as other downstream LIFR signaling was markedly decreased by EC359 treatment. Treatment with EC359 also decreased the stemness of OCa cells, slowed PDO development, and sensitized chemotherapy-resistant OCa cells to chemotherapy. One of the significant pathways elevated by EC359, according to RNA-seq data, is the regulation of apoptosis. In six different cell-based xenografts and PDX tumors, we demonstrated that the EC359 at 5mg/kg dose significantly reduced the OCa xenograft growth. In comparison to the vehicle control, the tumor volume was significantly reduced by EC359 treatment of murine ID8 xenografts in C57BL6 mice. Our findings indicated that EC359 had both intrinsic and extrinsic effects on tumors. Tumor-associated macrophages (TAMs) with a significant M1 polarity (CD11b+Gr1-CD68high/phosphoSTAT1+/cMAF-) and robust tumor infiltration by (CD45+) leukocytes were enhanced with EC359 therapy of ID8 xenograft tumors. Importantly, normal T, B, and other immune cells in the blood demonstrated that EC359 had no effect on immune cell homeostasis.

Conclusions: Together, our findings support the existence of LIF/LIFR autocrine loops, and EC359 is a viable treatment option for OCa.

Citation Format: Behnam Ebrahimi, Suryavathi Viswanadhapalli, Uday P. Pratap, Rahul Gopalam, Xue Yang, Bindhu Santhamma, Swapna Konda, Xiaonan Li, Hui Yan, Gangadhara R. Sareddy, Zhenming Xu, Edward R. Kost, Rajeshwar R. Tekmal, Hareesh B. Nair, Ratna K. Vadlamudi. Targeting LIF/LIFR autocrine loops with EC359 in ovarian cancer: A novel LIFR targeted therapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4966.

Abstract 3081: KDM1A/LSD1 inhibition enhances estrogen receptor beta mediated tumor suppression in ovarian cancer

Introduction: Ovarian cancer (OCa) is the deadliest of all gynecologic cancers. Recent studies suggest that OCa cells express estrogen receptor beta (ERb), which functions as a tumor suppressor. However, ERb expression decreases during tumor progression and under the selection pressure of chemotherapy; this decrease occurs via epigenetic mechanisms and is inversely correlated with OCa progression. Lysine-specific histone demethylase 1A (KDM1A/LSD1), an epigenetic modifier, is highly overexpressed in OCa. However, it is not known if KDM1A regulates ERb expression and its corresponding tumor suppressor functions. In this study, we explored the hypotheses that KDM1A inhibits ERb expression and function and that ERb-mediated tumor suppression in OCa is enhanced by KDM1A inhibition.

Methods: Transduction of KDM1A-specific shRNA or gRNA was used to generate KDM1A knockdown (KD) or knockout (KO) cells, respectively. Cell viability, survival, apoptosis, and invasion assays were used to determine the impact of KDM1A knockdown or inhibitor therapy on ERb agonist response in established and patient-derived OCa cells. Mechanistic studies were conducted using RNA-seq, discovery proteomics, chromatin immunoprecipitation (ChIP), co-immunoprecipitation (co-IP), proximity ligation, ERE-Luc reporter, RT-qPCR, and western blot analysis. The efficacy of the combination of KDM1A inhibitor and ERb agonist therapy was investigated using patient-derived explant (PDeX) models. In vivo efficacy of KDM1A inhibitor and ERb agonist was determined using orthotopic OCa and patient-derived xenograft (PDX) murine models.

Results: Analysis of TCGA datasets revealed a negative correlation between ERb and KDM1A expression in OCa patients. ChIP experiments showed that KDM1A is enriched at the ERb 0N promoter and that KDM1A KD, KO, or inhibition specifically upregulates the expression of ERb isoform 1. Co-IP and proximity ligation assays demonstrated that KDM1A interacts with ERb. Combining the ERb agonist LY500307 with KDM1A inhibitor NCD38 decreased the cell viability, survival, and invasion of both established and patient-derived primary OCa cells while increasing apoptosis. KDM1A KD- or inhibition potentiated the efficacy of ERb agonist in inducing ERb target gene expression via altered histone methylation marks. RNA-seq and proteomic analysis demonstrated that KDM1A KO and ERb agonist treatment increased the expression of apoptotic genes and downregulated cell cycle, EMT, and DNA repair genes. Importantly, combination therapy significantly reduced OCa cell proliferation in PDeX models and reduced in vivo tumor growth in orthotopic and PDX models.

Conclusions: Our findings demonstrate that KDM1A inhibition enhances ERb expression and tumor suppressive functions, suggesting that combination therapy of a KDM1A inhibitor and ERb agonist may be a promising therapeutic option for treating OCa.

Citation Format: Prabhakar P. Venkata, Sridharan Jayamohan, Yi He, Salvador Alejo, Jessica D. Johnson, Uday P. Pratap, Suryavathi Viswanadhapalli, Susan Weintraub, Rajeshwar R. Tekmal, Ratna K. Vadlamudi, Edward Kost, Gangadhara R. Sareddy. KDM1A/LSD1 inhibition enhances estrogen receptor beta mediated tumor suppression in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3081.

Abstract 4813: ERX-208 as a novel therapeutic for treating ovarian cancer by enhancing endoplasmic reticulum stress

Background: Ovarian cancer (OCa) is the deadliest of all gynecologic cancers in the United States. Despite initial response to chemotherapy, most OCa patients become chemo resistant and progress to metastatic disease. Here, we tested the hypothesis that the high basal level of endoplasmic reticulum stress (ERS) in OCa represents a critical vulnerability and drugs that further aggravate this already engaged system in OCa may exhaust its protective features and contribute to apoptosis induction. The objective of this proposal is to identify a hit compound that enhances ERS in OCa and to conduct mechanistic studies.

Methods: We synthesized a small library of >200 chemically distinct oligobenzamide analogs with maintenance of the chemical backbone but altered R groups of ERX-11. We performed the primary screening of this library to evaluate the induction of mRNA levels of two canonical ERS/UPR (unfolded protein response) genes- sXBP1 and CHOP. Biological activity of ERX-208 was validated using multiple OCa cells. Mechanistic studies were conducted using CRISPR/Cas9 KO, Western blotting, reporter gene assays, IHC and RNA-seq analysis. PK (pharmacokinetics) and toxicity studies were done using C57BL/6 mice. Cell line-derived xenografts (CDXs), patient-derived xenografts (PDXs), patient-derived explants (PDEs), and patient-derived organoids (PDO) were used for preclinical evaluation.

Results: From a screen of a curated ERX-11 derived oligobenzamide library, we identified a hit compound, ERX-208 that potently (IC50~100nM) induces ERS/UPR and apoptosis in multiple OCa cells in vitro. CRISPR KO screen identified the lysosomal acid lipase A (LIPA) protein as the critical target of ERX-208. LIPA KO abrogates response to ERX-208, while reconstitution of LIPA restores ERX-208 response. The time course studies showed a robust and consistent induction (>15-fold CHOP, and >10-fold sXBP1) by ERX-208 treatment within 24h. We confirmed induction of classic UPR components peIF2α, CHOP and LC3B using Western blotting in multiple OCa cells. Functionally, ERX-208 causes growth inhibition of OCa cells, as noted by MTT cell viability assays using 15 OCa cells with an IC50 of ~50-100nM. The activity of ERX-208 is distinct among oligobenzamides as ERX-11 has limited/no activity against OCa cells. RNA-seq analysis confirmed that ERX-208 induces significant ERS, UPR, and apoptosis. Further, ERX-208 reduced the growth of OCa PDO’s in vitro, PDEs ex vivo and CDXs and PDXs in vivo. ERX-208 treatment did not show any signs of toxicity and body weight of mice was not affected. IHC analyses showed increased activation of ERS/UPR markers such as GRP78, p-PERK and decreased proliferation measured by Ki67.

Conclusions: Collectively, our results demonstrated the utility of ERX-208 and will establish a novel therapeutic paradigm in OCa that overcomes tumor heterogeneity by targeting LIPA and enhancing ERS leading to apoptosis.

Citation Format: Suryavathi Viswanadhapalli, Tae-Kyung Lee, Kara Kassees, Gaurav Sharma, Rahul Gopalam, Karla Parra, Tanner Reese, Michael Hsieh, Uday P. Pratap, Xue Yang, Behnam Ebrahimi, Chia Yuan Chen, Scott Terry Elmore, Christian Cervantes, Zhenming Xu, Edward Kost, Gangadhara Reddy Sareddy, Rajeshwar Rao Tekmal, Jung-Mo Ann, Ganesh V. Raj, Ratna K. Vadlamudi. ERX-208 as a novel therapeutic for treating ovarian cancer by enhancing endoplasmic reticulum stress. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4813.

Inhibition of LIFR Blocks Adiposity-Driven Endometrioid Endometrial Cancer Growth

Simple Summary

In this study, we utilized global RNA-seq to elucidate the molecular mechanisms by which obese conditions promote progression of endometrioid endometrial cancer (EEC). Our results suggest that obese conditions upregulate LIF/LIFR signaling, and EEC tumors collected from obese patients have high levels of LIF. Mechanistic studies suggest that LIF/LIFR signaling plays an important role in obesity-driven EEC progression and the LIFR inhibitor, EC359, has the potential to suppress the tumor progression driven by increased adiposity found in obese patients.

Abstract

Endometrial cancer (EC) is the fourth most common cancer in women, and half of the endometrioid EC (EEC) cases are attributable to obesity. However, the underlying mechanism(s) of obesity-driven EEC remain(s) unclear. In this study, we examined whether LIF signaling plays a role in the obesity-driven progression of EEC. RNA-seq analysis of EEC cells stimulated by adipose conditioned medium (ADP-CM) showed upregulation of LIF/LIFR-mediated signaling pathways including JAK/STAT and interleukin pathways. Immunohistochemistry analysis of normal and EEC tissues collected from obese patients revealed that LIF expression is upregulated in EEC tissues compared to the normal endometrium. Treatment of both primary and established EEC cells with ADP-CM increased the expression of LIF and its receptor LIFR and enhanced proliferation of EEC cells. Treatment of EEC cells with the LIFR inhibitor EC359 abolished ADP-CM induced colony formation andcell viability and decreased growth of EEC organoids. Mechanistic studies using Western blotting, RT-qPCR and reporter assays confirmed that ADP-CM activated LIF/LIFR downstream signaling, which can be effectively attenuated by the addition of EC359. In xenograft assays, co-implantation of adipocytes significantly enhanced EEC xenograft tumor growth. Further, treatment with EC359 significantly attenuated adipocyte-induced EEC progression in vivo. Collectively, our data support the premise that LIF/LIFR signaling plays an important role in obesity-driven EEC progression and the LIFR inhibitor EC359 has the potential to suppress adipocyte-driven tumor progression.

A first-in-class inhibitor of ER coregulator PELP1 targets ER+ breast cancer

Most patients with estrogen receptor alpha-positive breast cancers (ER+ BC) initially respond to treatment but eventually develop therapy resistance with disease progression. Overexpression of oncogenic ER coregulators, including proline, glutamic acid, and leucine-rich protein 1 (PELP1), are implicated in BC progression. The lack of small molecules that inhibits PELP1 represents a major knowledge gap. Here, using a yeast-two-hybrid screen, we identified novel peptide inhibitors of PELP1 (PIPs). Biochemical assays demonstrated that one of these peptides, PIP1, directly interacted with PELP1 to block PELP1 oncogenic functions. Computational modeling of PIP1 revealed key residues contributing to its activity and facilitated the development of a small molecule inhibitor of PELP1, SMIP34, and further analyses confirmed that SMIP34 directly bound to PELP1. In BC cells, SMIP34 reduced cell growth in a PELP1-dependent manner. SMIP34 inhibited proliferation of not only wild-type (WT) but also mutant (MT) ER+ and therapy-resistant (TR) BC cells, in part by inducing PELP1 degradation via the proteasome pathway. RNA-seq analyses showed that SMIP34 treatment altered the expression of genes associated with estrogen response, cell cycle, and apoptosis pathways. In cell line-derived and patient-derived xenografts of both WT- and MT- ER+ BC models, SMIP34 reduced proliferation and significantly suppressed tumor progression. Collectively, these results demonstrate SMIP34 as a first-in-class inhibitor of oncogenic PELP1 signaling in advanced BC.

Therapeutic Targeting of Ovarian Cancer Stem Cells Using Estrogen Receptor Beta Agonist

Ovarian cancer (OCa) is the deadliest gynecologic cancer. Emerging studies suggest ovarian cancer stem cells (OCSCs) contribute to chemotherapy resistance and tumor relapse. Recent studies demonstrated estrogen receptor beta (ERβ) exerts tumor suppressor functions in OCa. However, the status of ERβ expression in OCSCs and the therapeutic utility of the ERβ agonist LY500307 for targeting OCSCs remain unknown. OCSCs were enriched from ES2, OV90, SKOV3, OVSAHO, and A2780 cells using ALDEFLUOR kit. RT-qPCR results showed ERβ, particularly ERβ isoform 1, is highly expressed in OCSCs and that ERβ agonist LY500307 significantly reduced the viability of OCSCs. Treatment of OCSCs with LY500307 significantly reduced sphere formation, self-renewal, and invasion, while also promoting apoptosis and G2/M cell cycle arrest. Mechanistic studies using RNA-seq analysis demonstrated that LY500307 treatment resulted in modulation of pathways related to cell cycle and apoptosis. Western blot and RT-qPCR assays demonstrated the upregulation of apoptosis and cell cycle arrest genes such as FDXR, p21/CDKN1A, cleaved PARP, and caspase 3, and the downregulation of stemness markers SOX2, Oct4, and Nanog. Importantly, treatment of LY500307 significantly attenuated the tumor-initiating capacity of OCSCs in orthotopic OCa murine xenograft models. Our results demonstrate that ERβ agonist LY500307 is highly efficacious in reducing the stemness and promoting apoptosis of OCSCs and shows significant promise as a novel therapeutic agent in treating OCa.

Abstract 648: A novel small molecule targeting oncogenic PELP1 demonstrates anti-tumor activity in wild-type and mutant ER-positive breast cancer

A significant proportion of estrogen receptor positive breast cancers (ER+BC) will initially respond to treatment, but many eventually develop therapy resistance (TR-BC), and progress to incurable metastases. Oncogenic ER coregulators overexpressed in BC can contribute to constitutive, ligand-independent and ligand-dependent signaling which drives growth, resistance to therapy and metastasis. Proline-, glutamic acid, and leucine-rich protein 1 (PELP1), is a known coregulator that plays a critical role in ER oncogenic functions. Its expression is deregulated in BC and is a prognostic indicator of poor BC survival. The lack of a small molecule inhibitor that directly targets PELP1 represents a major knowledge gap. Therefore, we conducted a large scale peptide library screening and identified novel Peptide Inhibitor of PELP1 (PIP1). We demonstrated that PIP1 directly interacts with PELP1, promotes its degradation and has the potential to block PELP1 oncogenic functions in vitro. Using innovative peptidomimetic technology, we modeled PIP1 and synthesized several derivatives as Small Molecule Inhibitors of PELP1 (SMIPs). Using MTT assay and multiple BC cell lines, we identified a lead compound, SMIP34 with an IC50 of 5-10µM and with minimal effect on human mammary epithelial cells. SMIP34 in vitro activity was assessed by colony formation and Matrigel invasion assays. Knockdown of PELP1 using shRNA in BC cells significantly reduced SMIP34 activity, indicating target specificity. Further, MST and biotin-SMIP34 pulldown confirmed direct binding of SMIP34 to PELP1. Using ER+WT, mtER (mutant ER), and TR-BC cell lines we demonstrated that SMIP34 exhibits antiproliferative effects and reduces invasiveness. Mechanistic studies using Western blot analysis confirmed that SMIP34 binding to PELP1 contributes to its degradation via the proteasome pathway. Thus MG132 treatment attenuated SMIP34 mediated degradation. RTqPCR analyses confirmed SMIP34 treatment reduced expression of PELP1 target genes. RNAseq analyses showed SMIP34 treatment altered the expression of genes associated with Estrogen response, Cell cycle and Apoptosis pathways. Cell cycle analyses revealed SMIP34 treatment promoted S phase arrest of BC cell lines. Using ER+WT, mtER, and PDX tumor tissues ex vivo, we demonstrated that SMIP34 significantly decreased tumor proliferation as measured by Ki67 staining. Further, SMIP34 (20mg/kg/IP) treatment in vivo significantly reduced tumor progression in mouse models of ER+WT, mtER, and mtER patient-derived xenograft BC. Our results using in vitro, ex vivo, and in vivo models showcase SMIP34 as a first-in-class inhibitor of oncogenic PELP1 signaling and may serve as a potential therapeutic molecule for treating ER+, mtER, and TR-BC. Supported by NIH 1F31CA257298 (KA) and VA I01BX004545 (RV).

Citation Format: Kristin Ann Altwegg, Monica Mann, Dimple Chakravarty, Zexuan Liu, Junhao Liu, Uday P. Pratap, Behnam Ebrahimi, John R. Sanchez, Ben H. Park, Hariprasad Vankayalapati, Gangadhara R. Sareddy, Suryavathi Viswanadhapalli, Ratna K. Vadlamudi. A novel small molecule targeting oncogenic PELP1 demonstrates anti-tumor activity in wild-type and mutant ER-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 648.

Abstract 891: Therapeutic targeting of ovarian cancer stem cells using estrogen receptor beta agonist

Background: Ovarian cancer (OCa) is the deadliest gynecologic cancer. Emerging studies suggest that ovarian cancer stem cells (OCSCs) contribute to tumor relapse and chemotherapy resistance. Recent studies demonstrate that OCa cells express estrogen receptor beta (ERβ), which functions as a tumor suppressor. However, the status of ERβ expression in OCSCs and the therapeutic utility of ERβ agonist LY500307 for targeting OCSCs remain unknown. In this study, we tested the hypothesis that OCSCs express ERβ and that treatment with ERβ agonist reduces stemness and promotes apoptosis of OCSCs.

Methods: We isolated subpopulations of OCSCs from SKOV3, A2780, and patient-derived ascites cells using ALDEFLUOR kit and examined the expression of ERβ in OCSCs using RT-qPCR. The effect of ERβ agonist LY500307 on OCSCs was examined utilizing cell viability, cell cycle, sphere formation, self-renewal, and apoptosis assays. Mechanistic studies were conducted using RNA-seq, RT-qPCR, and Western blot analysis. The efficacy of LY500307 on the tumor-initiating capacity of OCSCs was determined via in vivo limiting dilution assay studies using orthotopic intrabursal xenograft murine models.

Results: RT-qPCR assay showed that ERβ, particularly ERβ isoform 1, is highly expressed in OCSCs compared to non-OCSCs. ERβ agonist LY500307 significantly reduced the viability of OCSCs compared to non-OCSCs. Treatment of OCSCs with LY500307 significantly reduced the sphere formation and self-renewal of OCSCs. Further, LY500307 treatment resulted in G2/M cell cycle arrest and promoted the apoptosis of OCSCs. Mechanistic studies using RNA-seq analysis demonstrated that ERβ agonist treatment resulted in the modulation of pathways related to cell cycle and apoptosis. Western blots and RT-qPCR assays confirmed the upregulation of genes involved in apoptosis and cell cycle arrest, such as FDXR and CDKN1A. Importantly, treatment of LY500307 significantly attenuated the tumor-initiating capacity of OCSCs in orthotopically implanted OCa murine models.

Conclusions: Our results demonstrate that ERβ agonist LY500307 is highly efficacious in reducing the stemness and promoting apoptosis of OCSCs and may serve as a novel therapeutic agent in treating OCa

Citation Format: Yi He, Salvador Alejo, Prabhakar P. Venkata, Jessica D. Johnson, Ilanna Loeffel, Julie Ann Martel, Uday P. Pratap, Suryavathi Viswanadhapalli, Rajeshwar R. Tekmal, Ratna K. Vadlamudi, Edward Kost, Gangadhara R. Sareddy. Therapeutic targeting of ovarian cancer stem cells using estrogen receptor beta agonist [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 891.

Regulation and Role of Neuron-Derived Hemoglobin in the Mouse Hippocampus

Hemoglobin (Hb) is the oxygen transport protein in erythrocytes. In blood, Hb is a tetramer consisting of two Hb-alpha (Hb-α) chains and two Hb-beta (Hb-β) chains. A number of studies have also shown that Hb-α is also expressed in neurons in both the rodent and human brain. In the current study, we examined for age-related regulation of neuronal Hb-α and hypoxia in the hippocampus and cerebral cortex of intact male and female mice. In addition, to confirm the role and functions of neuronal Hb-α, we also utilized lentivirus CRISPR interference-based Hb-α knockdown (Hb-α CRISPRi KD) in the non-ischemic and ischemic mouse hippocampus and examined the effect on neuronal oxygenation, as well as induction of hypoxia-inducible factor-1α (HIF-1α) and its downstream pro-apoptotic factors, PUMA and NOXA, and on neuronal survival and neurodegeneration. The results of the study revealed an age-related decrease in neuronal Hb-α levels and correlated increase in hypoxia in the hippocampus and cortex of intact male and female mice. Sex differences were observed with males having higher neuronal Hb-α levels than females in all brain regions at all ages. In vivo Hb-α CRISPRi KD in the mouse hippocampus resulted in increased hypoxia and elevated levels of HIF-1α, PUMA and NOXA in the non-ischemic and ischemic mouse hippocampus, effects that were correlated with a significant decrease in neuronal survival and increased neurodegeneration. As a whole, these findings indicate that neuronal Hb-α decreases with age in mice and has an important role in regulating neuronal oxygenation and neuroprotection.

SETDB1 interactions with PELP1 contributes to breast cancer endocrine therapy resistance

Background

Methyltransferase SETDB1 is highly expressed in breast cancer (BC), however, the mechanisms by which SETDB1 promotes BC progression to endocrine therapy resistance remains elusive. In this study, we examined the mechanisms by which SETDB1 contribute to BC endocrine therapy resistance.

Methods

We utilized therapy sensitive (MCF7 and ZR75), therapy resistant (MCF7-TamR, MCF7-FR, MCF7-PELP1cyto, MCF7-SETDB1) estrogen receptor alpha positive (ER⁺)BC models and conducted in vitro cell viability, colony formation, 3-dimensional cell growth assays to investigate the role of SETDB1 in endocrine resistance. RNA-seq of parental and SETDB1 knock down ER⁺ BC cells was used to identify unique pathways. SETDB1 interaction with PELP1 was identified by yeast-two hybrid screen and confirmed by immunoprecipitation and GST-pull down assays. Mechanistic studies were conducted using Western blotting, reporter gene assays, RT-qPCR, and in vitro methylation assays. Xenograft assays were used to establish the role of PELP1 in SETDB1 mediated BC progression.

Results

RNA-seq analyses showed that SETDB1 regulates expression of a subset of estrogen receptor (ER) and Akt target genes that contribute to endocrine therapy resistance. Importantly, using yeast-two hybrid screen, we identified ER coregulator PELP1 as a novel interacting protein of SETDB1. Biochemical analyses confirmed SETDB1 and PELP1 interactions in multiple BC cells. Mechanistic studies confirmed that PELP1 is necessary for SETDB1 mediated Akt methylation and phosphorylation. Further, SETDB1 overexpression promotes tamoxifen resistance in BC cells, and PELP1 knockdown abolished these effects. Using xenograft model, we provided genetic evidence that PELP1 is essential for SETDB1 mediated BC progression in vivo. Analyses of TCGA datasets revealed SETDB1 expression is positively correlated with PELP1 expression in ER⁺ BC patients.

Conclusions

This study suggests that the PELP1/SETDB1 axis play an important role in aberrant Akt activation and serves as a novel target for treating endocrine therapy resistance in breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-022-01520-4.

Abstract P5-10-01: Leukemia inhibitory factor receptor inhibition reduces obesity driven progression of triple negative breast cancer

Background: The obesity epidemic is rapidly increasing in the USA and obese women are at a higher likelihood of developing triple negative breast cancer (TNBC). Several studies implicated the importance of the breast microenvironment on the aggressive cancer biology especially obese microenvironment. However, the underlying mechanism(s) by which obesity contributes to the progression of TNBC remains unclear. The objective of this study is to test a novel concept that obesity upregulates leukemia inhibitory factor receptor (LIFR) oncogenic signaling in TNBC and test whether LIFR inhibition blocks TNBC progression. Methods: Established TNBC cell lines were co-cultured with human primary adipocytes or incubated with adipocyte conditioned medium or with high glucose (HG) followed by treatment with LIFR inhibitor EC359. The effect of adiposity on TNBC cells was determined using cell viability, colony formation, and invasion assays. Mechanistic studies were performed using CRISPR/Cas9 KO of LIFR, Western blotting, RT-qPCR, and reporter gene assays. Utility of LIFR inhibitor EC359 was tested using xenografts, and patient derived organoid (PDO) models. Results: Treatment of TNBC cells with adipose conditions or HG increased the proliferation and invasion of TNBC cells. Western blot and RT-qPCR analyses confirmed that increased expression of LIFR correlated with enhanced downstream LIFR signaling such as STAT3 and subsequent activation of STAT3 target genes. CRISPR KO of LIFR or treatment of TNBC cells with EC359 significantly reduced the cell viability, colony formation and invasion under adipose conditions. Western blotting results showed that co-culture with adipocytes significantly enhanced LIFR downstream signaling in TNBC model cells and is effectively blocked by LIFR KO or EC359 treatment. Further, EC359 treatment blocked the adipose environment mediated growth of organoids. Importantly, co-implantation of adipocytes significantly enhanced TNBC xenograft tumor growth, however treatment with EC359 significantly attenuated adipocyte induced TNBC progression. Conclusions: Collectively, these results suggest that adiposity contributes to increased TNBC cell growth via upregulation of the LIF/LIFR pathway. The LIF/LIFR axis represents a potential therapeutic target for adiposity driven TNBC and the LIFR inhibitor EC359 could be used as a new therapeutic agent to treat obesity associated TNBC.

Citation Format: Suryavathi Viswanadhapalli, Uday P Pratap, Behnam Ebrahimi, Logan Blankenship, Jaitri Joshi, Zexuan Liu, Kristin A Altwegg, Xiaonan Li, Gangadhara R Sareddy, Bindu Santhamma, Swapna Konda, Manjeet Rao, Edward Kost, Rajeshwar R Tekmal, Hareesh B Nair, Ratna K Vadlamudi. Leukemia inhibitory factor receptor inhibition reduces obesity driven progression of triple negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-10-01.

Neuron-Derived Estrogen-A Key Neuromodulator in Synaptic Function and Memory

In addition to being a steroid hormone, 17β-estradiol (E₂) is also a neurosteroid produced in neurons in various regions of the brain of many species, including humans. Neuron-derived E₂ (NDE₂) is synthesized from androgen precursors via the action of the biosynthetic enzyme aromatase, which is located at synapses and in presynaptic terminals in neurons in both the male and female brain. In this review, we discuss evidence supporting a key role for NDE₂ as a neuromodulator that regulates synaptic plasticity and memory. Evidence supporting an important neuromodulatory role of NDE₂ in the brain has come from studies using aromatase inhibitors, aromatase overexpression in neurons, global aromatase knockout mice, and the recent development of conditional forebrain neuron-specific knockout mice. Collectively, these studies demonstrate a key role of NDE₂ in the regulation of synapse and spine density, efficacy of excitatory synaptic transmission and long-term potentiation, and regulation of hippocampal-dependent recognition memory, spatial reference memory, and contextual fear memory. NDE₂ is suggested to achieve these effects through estrogen receptor-mediated regulation of rapid kinase signaling and CREB-BDNF signaling pathways, which regulate actin remodeling, as well as transcription, translation, and transport of synaptic proteins critical for synaptic plasticity and function.

Brain-derived estrogen and neural function

Although classically known as an endocrine signal produced by the ovary, 17β-estradiol (E₂) is also a neurosteroid produced in neurons and astrocytes in the brain of many different species. In this review, we provide a comprehensive overview of the localization, regulation, sex differences, and physiological/pathological roles of brain-derived E₂ (BDE₂). Much of what we know regarding the functional roles of BDE₂ has come from studies using specific inhibitors of the E₂ synthesis enzyme, aromatase, as well as the recent development of conditional forebrain neuron-specific and astrocyte-specific aromatase knockout mouse models. The evidence from these studies support a critical role for neuron-derived E₂ (NDE₂) in the regulation of synaptic plasticity, memory, socio-sexual behavior, sexual differentiation, reproduction, injury-induced reactive gliosis, and neuroprotection. Furthermore, we review evidence that astrocyte-derived E₂ (ADE₂) is induced following brain injury/ischemia, and plays a key role in reactive gliosis, neuroprotection, and cognitive preservation. Finally, we conclude by discussing the key controversies and challenges in this area, as well as potential future directions for the field.

LIFR inhibition enhances the therapeutic efficacy of HDAC inhibitors in triple negative breast cancer

Histone deacetylase inhibitors (HDACi) are identified as novel therapeutic agents, however, recent clinical studies suggested that they are marginally effective in treating triple negative breast cancer (TNBC). Here, we show that first-in-class Leukemia Inhibitory Factor Receptor (LIFRα) inhibitor EC359 could enhance the therapeutic efficacy of HDACi against TNBC. We observed that both targeted knockdown of LIFR with CRISPR or treatment with EC359 enhanced the potency of four different HDACi in reducing cell viability, cell survival, and enhanced apoptosis compared to monotherapy in TNBC cells. RNA-seq studies demonstrated oncogenic/survival signaling pathways activated by HDACi were attenuated by the EC359 + HDACi therapy. Importantly, combination therapy potently inhibited the growth of TNBC patient derived explants, cell derived xenografts and patient-derived xenografts in vivo. Collectively, our results suggest that targeted inhibition of LIFR can enhance the therapeutic efficacy of HDACi in TNBC.

LIF/LIFR oncogenic signaling is a novel therapeutic target in endometrial cancer

Endometrial cancer (EC) is the fourth most common cancer in women. Advanced-stage EC has limited treatment options with a poor prognosis. There is an unmet need for the identification of actionable drivers for the development of targeted therapies in EC. Leukemia inhibitory factor receptor (LIFR) and its ligand LIF play a major role in cancer progression, metastasis, stemness, and therapy resistance. However, little is known about the functional significance of the LIF/LIFR axis in EC progression. In this study using endometrial tumor tissue arrays, we identified that expression of LIF, LIFR is upregulated in EC. Knockout of LIFR using CRISPR/Cas9 in two different EC cells resulted in a significant reduction of their cell viability and cell survival. In vivo studies demonstrated that LIFR-KO significantly reduced EC xenograft tumor growth. Treatment of established and primary patient-derived EC cells with a novel LIFR inhibitor, EC359 resulted in the reduction of cell viability with an IC50 in the range of 20-100 nM and induction of apoptosis. Further, treatment with EC359 reduced the spheroid formation of EC cancer stem cells and reduced the levels of cancer stem cell markers SOX2, OCT4, NANOG, and Axin2. Mechanistic studies demonstrated that EC359 treatment attenuated the activation of LIF-LIFR driven pathways, including STAT3 and AKT/mTOR signaling in EC cells. Importantly, EC359 treatment resulted in a significant reduction of the growth of EC patient-derived explants ex vivo, EC cell line-derived xenografts, and patient-derived xenografts in vivo. Collectively, our work revealed the oncogenic potential of the LIF/LIFR axis in EC and support the utility of LIFR inhibitor, EC359, as a novel targeted therapy for EC via the inhibition of LIF/LIFR oncogenic signaling.

Abstract 1253: Therapeutic targeting of endometrial cancer with novel LIFR inhibitor EC359

Background: Endometrial cancer (EC) is the fourth most common cancer in women. Approximately 80% of EC belong to the endometroid-EC subtype and are driven by estrogen signaling. Advanced-stage EC has limited treatment options with poor prognosis. There is an urgent need for the identification of actionable drivers as new targets for treating advance stage EC. Leukemia inhibitory factor receptor (LIFR) and its ligand LIF plays a major role in cancer progression, metastasis, stemness, and therapy resistance. Published and our preliminary data suggest a critical role of the LIF-LIFR signaling axis in EC progression. The objective of this study is to test the utility of targeting the LIF/LIFR axis using a novel LIFR inhibitor, EC359.

Methods: We used multiple established and primary EC cells to test the utility LIFR inhibitor, EC359 in treating EC. CRISPR/Cas9 system was used to generate LIFR KO EC cells. In vitro activity was tested using Cell-Titer Glo, MTT, invasion, and apoptosis assays. Mechanistic studies were conducted using Western blot, reporter gene assays, and RNA-seq analysis. EC cell-derived xenograft (CDX) and patient-derived explant (PDEX) models were used for preclinical evaluation and toxicity.

Results: EC359 treatment of seven EC cells showed anti-proliferative effects in MTT cell viability assays with an IC50 of 25-100 nM. Further, EC359 treatment reduced invasiveness, stemness, and promoted apoptosis of EC cells. The activity of EC359 is dependent on LIF/LIFR expression in EC cells. CRISPR mediated knockout of LIFR significantly abolished EC359 activity. In vivo xenograft studies using Ishikawa-vector or LIFR-KO cells demonstrated that LIFR-KO significantly reduced EC tumor growth, and tumor weights. Further, EC359 treatment attenuated the activation of LIF/LIFR driven pathways, including STAT3, AKT-mTOR signaling. Mechanistic studies using RNA-seq revealed that EC359 significantly upregulated 213 genes and down regulated 126 genes. Pathway analyses of differential genes revealed enrichment in the apoptotic pathways upon EC359 treatment. EC359 (5mg/kg body weight) treatment significantly reduced CDX tumor progression and reduced proliferation in PDEX models.

Conclusions: Collectively, these data support EC359 as a novel targeted therapy for EC by inhibiting LIF/LIFR oncogenic signaling pathway.

Citation Format: Weiwei Tang, Kumaraguruparan Ramasamy, Sureshkumar M. Pillai, Bindu Santhamma, Swapna Konda, Prabhakar P. Vekata, Logan Blankenship, Junhao Liu, Zexuan Liu, Kristin A. Altwegg, Behnam Ebrahimi, Uday P. Pratap, Xiaonan Li, Edward Kost, Gangadhara R. Sareddy, Ratna K. Vadlamudi, Hareesh B. Nair, Rajeshwar R. Tekmal, Suryavathi Viswanadhapalli. Therapeutic targeting of endometrial cancer with novel LIFR inhibitor EC359 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1253.

Abstract 733: Significance of PELP1/SETDB1 axis in endocrine therapy resistance

BACKGROUND: PELP1 is commonly overexpressed in breast cancer (BCa) and is implicated in endocrine therapy resistance. However, the mechanism by which PELP1 contributes to therapy resistance remains elusive. Our ongoing studies using yeast two hybrid screen identified histone methyltransferase SETDB1 as a novel interactor of PELP1. The objective of this study is to determine the significance of PELP1 interaction with SETDB1 in BCa endocrine therapy resistance.

METHODS: We used two ER+ BCa cell lines (MCF7 and ZR75) and three endocrine therapy resistant cell lines (Tamoxifen resistant MCF7-TamR, Fulvestrant resistant MCF7-FR, Tamoxifen resistant MCF7-PELP1-cyto). Additional BCa models with stable overexpression and under expression of SETDB1 and PELP1 (MCF7-SETDB1-PELP1shRNA, ZR75-SETDB1-PELP1shRNA, ZR75-SETDB1, MCF7-SETDB1, MCF7-TamR-SETDB1shRNA, MCF7-FR-SETDB1shRNA) were generated using lentiviral transduction. Functional significance of cross-talk was tested using MTT, soft agar, and colony formation assays. Mechanistic studies were conducted using immunoprecipitation, Western blotting, and RT-qPCR.

RESULTS: Analyses of TCGA databases showed that SETDB1 expression is positively correlated with PELP1 expression in ER+ BCa (r=0.30, p<0.0001). Immunoprecipitation assays using multiple ER+ BCa cell lysates confirmed the interaction of SETDB1 with PELP1. Using ER+ BCa models with overexpression of SETDB1 or knockdown, we provided evidence that SETDB1 plays an important role in the proliferation of BCa cells. PELP1 knockdown attenuated SETDB1 mediated BCa cells proliferation. SETDB1 upregulation contributed to tamoxifen resistance, while PELP1 knockdown re-sensitized cells to tamoxifen therapy. Further, endocrine therapy resistant model cells (MCF7-TamR, MCF7-FR, MCF7-PELP1-cyto) showed increased expression of SETDB1, and its knockdown sensitized them to endocrine therapy. Mechanistic studies revealed that PELP1 is needed for SETDB1 mediated Akt phosphorylation and activation of its downstream targets such as S6, and Cyclin D1.

CONCLUSIONS: The results of study suggest that the PELP1/SETDB1 interactions contribute to endocrine therapy resistance via aberrant activation of Akt signaling. Targeting PELP1/SETDB1 axis could represent a new therapeutic avenue to mitigate endocrine resistance. Supported by VA grant I01BX004545 (R.K. Vadlamudi)

Citation Format: Zexuan Liu, Junhao Liu, Weiwei Tang, Uday P. Pratap, Kristin A. Altwegg, Behnam Ebrahimi, Xiaonan Li, Gangadhara R. Sareddy, Suryavathi Viswanadhapalli, Ratna K. Vadlamudi. Significance of PELP1/SETDB1 axis in endocrine therapy resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 733.

Abstract 1333: Evaluation of a novel PELP1 inhibitor for treatment of triple negative breast cancer

Background: Breast cancer (BC) is composed of distinct molecular subtypes, such as ER+ BC and triple negative BC (TNBC). Development of novel effective therapies for patients with TNBC remains the highest unmet need in patient treatment and survivorship. PELP1 plays an essential role in several pathways including hormonal signaling, cell cycle progression, ribosomal biogenesis, and DNA damage response. PELP1 expression is an independent prognostic predictor of shorter BC-specific survival and an independent prognostic factor for predicting poor survivorship in TNBC patients. Recently, we generated a small molecule inhibitor of PELP1 (SMIP34) that binds and inhibits PELP1 oncogenic signaling. The objective of this study is to test the utility of SMIP34 as a novel therapeutic for treating TNBC.

Methods: We have selected seven TNBC model cell lines (BT549, MDA-MB-453, MDA-MB-231, MDA-MB-468, SUM-159, HCC1806, and HCC1937) and one human mammary epithelial (HMEC) cell line in this study. In vitro activity was assessed using Cell Titer Glo, MTT, colony formation, and matrigel invasion assays. Mechanistic studies were conducted using Western blot, reporter gene assays, and RNA-seq. Xenograft tumor-derived explant (XDEX) assays and patient-derived tumor explant (PDEX) assays were used for preclinical evaluation.

Results: Using a panel of BC model cell lines, we found that SMIP34 treatment reduced cell viability with an IC50 of 3-8µM with no activity in HMEC cells. Knockdown of PELP1 using shRNA in BC cells significantly reduced SMIP34 activity, confirming its target specificity. We confirmed the physical interaction of SMIP34 to PELP1 using biotin-SMIP34 and MST assays. SMIP34 treatment significantly reduced the invasiveness and colony formation of TNBC cell lines. Mechanistic studies using Western blot analysis confirmed that SMIP34 binding to PELP1 contributes to its degradation. Further, RTqPCR analyses confirmed SMIP34 treatment reduced expression of PELP1 target genes. Western analyses confirmed SMIP34 treatment significantly reduced known PELP1 downstream signaling. Mechanistic studies using global RNA-seq identified that SMIP34 treatment alters known PELP1 modulated pathways (ribosomal biogenesis). Using MDA-MB-231 xenograft and PDX tumor tissues in explant assays, we demonstrated that SMIP34 significantly decreased tumor proliferation as measured by Ki67 staining. Accordingly, in xenograft models, SMIP34 (20mg/kg/IP) treatment resulted in a significant reduction in tumor volume compared to vehicle control.

Conclusion: Our results using in vitro, ex vivo, and in vivo studies demonstrated that the PELP1 inhibitor SMIP34 has therapeutic efficacy against TNBC. Supported by CPRIT Predoctoral Fellowship CPRIT RTA; RP170345 (K.A. Altwegg) and VA grant I01BX004545 (R.K.V)

Citation Format: Kristin A. Altwegg, Suryavathi Viswanadhapalli, Junhao Liu, Zexuan Liu, Uday P. Pratap, Hariprasad Vankayalapati, Ratna K. Vadlamudi. Evaluation of a novel PELP1 inhibitor for treatment of triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1333.

Abstract 2026: KDM1A inhibition augment ER stress inducers efficacy to reduce glioblastoma stemness

Background: Glioblastoma (GBM) is the most common malignant brain tumor with a dismal prognosis and median survival of 20 months. Standard therapy consists of surgical resection, external beam radiation therapy, adjuvant chemotherapy with temozolomide, and tumor-treating fields. Despite these therapies, GBM patients inevitably experience tumor progression and eventually succumb to their disease. Glioma stem cells (GSCs) play a central role in GBM development and contribute to treatment resistance. Recently we showed that lysine-specific histone demethylase 1A (KDM1A/LSD1) is essential for GSCs stemness, and inhibition of KDM1A induces unfolded protein response (UPR) in GSCs. In this study, we tested the hypothesis that inhibition of KDM1A sensitizes GSCs to ER stress inducers by inducing UPR.

Methods: KDM1A knockdown (KDM1A-KD) cells were generated using KDM1A specific shRNA. We studied the effect of KDM1A-KD or pharmacological KDM1A inhibitors (NCD38 and NCL-1) in combination with ER stress inducers (thapsigargin and brefeldin A) on GSCs viability using CellTiter-Glo assay. Stemness was determined using extreme limiting dilution analysis (ELDA) and sphere formation assays. Mechanistic studies were conducted using RNA-seq, ChIP, RT-qPCR, and Western blotting analysis. Furthermore, the in vivo efficacy of KDM1A inhibitor and ER stress inducer was studied using orthotopic models of GBM.

Results: Cell viability assays demonstrated that knockdown or inhibition of KDM1A sensitized GSCs to ER stress inducers thapsigargin and brefeldin A. Furthermore, KDM1A-KD, NCD38, or NCL-1, in combination with ER stress inducers, significantly decreased the stemness and sphere-forming ability of GSCs. RNA-seq analysis revealed that UPR was activated after knockdown or inhibition of KDM1A in GSCs. Western blot and RT-qPCR analysis showed that a combination of KDM1A inhibitors and ER stress inducers increased UPR signaling in GSCs. ChIP analysis indicated that KDM1A inhibition enriched the active histone methylation mark (H3K4me2) at the promoter of UPR target genes. In vivo studies showed that KDM1A inhibition activates UPR in tumors and improved overall survival.

Conclusions: Our results support that KDM1A knockdown or inhibition sensitizes GSCs to ER stress inducers and that the use of KDM1A inhibitors in conjunction with ER stress inducers is a potential novel therapy for GBM patients.

Citation Format: Yi He, Prabhakar Pitta Venkata, Salvador Alejo, Yihong Chen, Bridgitte Palacios, Gabrielle Gray, Uday P. Pratap, Suryavathi Viswanadhapalli, Siyuan Zheng, Rajeshwar R. Tekmal, Andrew J. Brenner, Gangadhara R. Sareddy. KDM1A inhibition augment ER stress inducers efficacy to reduce glioblastoma stemness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2026.

Interaction of transcription factor AP-2 gamma with proto-oncogene PELP1 promotes tumorigenesis by enhancing RET signaling

A significant proportion of estrogen receptor-positive (ER+) breast cancer (BC) initially responds to endocrine therapy but eventually evolves into therapy-resistant BC. Transcription factor AP-2 gamma (TFAP2C) is a known regulator of ER activity, and high expression of TFAP2C is associated with a decreased response to endocrine therapies. PELP1 is a nuclear receptor coregulator, commonly overexpressed in BC, and its levels are correlated with poorer survival. In this study, we identified PELP1 as a novel interacting protein of TFAP2C. RNA-seq analysis of PELP1 knockdown BC cells followed by transcription factor motif prediction pointed to TFAP2C being enriched in PELP1-regulated genes. Gene set enrichment analysis (GSEA) revealed that the TFAP2C-PELP1 axis induced a subset of common genes. Reporter gene assays confirmed PELP1 functions as a coactivator of TFAP2C. Mechanistic studies showed that PELP1-mediated changes in histone methylation contributed to increased expression of the TFAP2C target gene RET. Furthermore, the TFAP2C-PELP1 axis promoted the activation of the RET signaling pathway, which contributed to downstream activation of AKT and ERK pathways in ER+ BC cells. Concomitantly, knockdown of PELP1 attenuated these effects mediated by TFAP2C. Overexpression of TFAP2C contributed to increased cell proliferation and therapy resistance in ER+ BC models, while knockdown of PELP1 mitigated these effects. Utilizing ZR75-TFAP2C xenografts with or without PELP1 knockdown, we provided genetic evidence that endogenous PELP1 is essential for TFAP2C-driven BC progression in vivo. Collectively, our studies demonstrated that PELP1 plays a critical role in TFAP2C transcriptional and tumorigenic functions in BC and blocking the PELP1-TFAP2C axis could have utility for treating therapy resistance.

Abstract PS17-34: Proto-oncogene PELP1 interactions with SETDB1 contribute to aberrant activation of AKT1 in breast cancer

BACKGROUND: Hyperactivation of PI3K/Akt signaling is implicated in breast cancer (BCa) progression. SETDB1, a methyltransferase, is also implicated in BCa, however, the mechanism remains elusive. Recent studies have shown SETDB1 can methylate non-histone substrates such as Akt1 and contribute to its aberrant activation, thus leading to tumor progression. PELP1 is a proto-oncogene which is overexpressed in BCa and participates in both the nuclear and extra nuclear functions of various nuclear receptors. In a subset of BCa, PELP1 uniquely localizes in the cytoplasm and contributes to endocrine therapy resistance. The objective of this study is to characterize the significance of PELP1 in SETDB1 mediated Akt signaling in BCa progression.

METHODS: Using yeast two-hybrid screening, we identified PELP1 as a novel interacting protein of SETDB1. Functional significance of cross-talk was tested using MTT, proliferation, stemness and colony formation assays. Mechanistic studies were conducted using immunoprecipitation, RNA-seq, shRNA, overexpression, Western blotting, and RT-qPCR. Biological significance of PELP1 and SETDB1 in endocrine therapy resistance was also examined.

RESULTS: Analyses of TCGA databases showed that SETDB1 is highly expressed in BCa and associated with poor clinical outcome. Further, SETDB1 expression is positively correlated with PELP1 expression in BCa (r=0.30, p<0.0001). Immunoprecipitation assays using multiple BCa cell lysates confirmed the interaction of SETDB1 with PELP1. Using two different shRNAs targeting SETDB1 and multiple BCa model cells, we provided evidence that SETDB1 plays an important role in the proliferation of BCa cells. SETDB1 upregulation is sufficient to accelerate proliferation and PELP1 knockdown attenuated SETDB1 oncogenic functions. SETDB1 overexpression contributed to resistance to tamoxifen treatment, while PELP1 knockdown re-sensitized cells to therapy. RNA-seq identified Akt signaling pathways were activated by SETDB1 in BCa. Mechanistic studies showed that SETDB1 overexpression increased Akt phosphorylation and its downstream signaling, while PELP1 knock down attenuated SETDB1 mediated Akt activation in both MCF7 and ZR75 models. Furthermore, in BCa model cells that uniquely express PELP1 in cytoplasm, knockdown of SETDB1 reduced activation of Akt and its downstream pathways.

CONCLUSIONS: Our study results suggest that the PELP1/SETDB1 interactome plays an important role in aberrant Akt activation. Drugs that target PELP1/SETDB1 axis may be useful in modulating aberrant Akt signaling. Supported by VA grant I01BX004545.

Citation Format: Zexuan Liu, Junhao Liu, Weiwei Tang, Uday P. Pratap, Kristin A. Altwegg, Xiaonan Li, Suryavathi Viswanadhapalli, Ratna Vadlamudi. Proto-oncogene PELP1 interactions with SETDB1 contribute to aberrant activation of AKT1 in breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-34.

Abstract PS17-15: Targeting the PELP1 axis for treating ESR1 mutant driven breast cancer

Background: Mutations in ESR1 genes (30-40% frequency) play an important role in acquired endocrine therapy resistance and metastases. The most commonly observed are two ESR1 LBD mutations, D538G andY537S. These mutant ERα (MT) proteins have high constitutive transcriptional activity leading to therapy resistance. Furthermore, the ability of the constitutively active mutants to interact with coregulators is associated with the promotion of tumor growth. Proline, glutamic acid-, and leucine-rich protein 1 (PELP1), an oncogenic coregulator of ERα, plays a critical role in ERα signaling, and its dysregulated expression is a prognostic indicator for poorer breast cancer (BCa) survival. The objective of this study was to test the utility of Small Molecule Inhibitor of PELP1 (SMIP34) for treating ESR1 mutant (MT-ER) driven BCa. Methods: Four BCa models that express either ESR1 mutation D538G or Y537S and their respective wild-typeERα (WT-ER) controls were used to test the utility of targeting the PELP1 axis using PELP1-specific shRNA orSMIP34. Celltiter Glo, MTT, colony formation, and Boyden chamber invasion assays were used to test the efficacy of SMIP34. Western blot, RNA-Seq, and reporter gene assays were utilized to uncover the mechanistic insights. Pre-clinical evaluation was performed using MT-ER expressing xenograft explant (XDEX) and patient-derived explant (PDEX) assays. Results: BCa model cells expressing MT-ER showed increased cell proliferation, whilst PELP1 knock-down significantly reduced their proliferation. Immunoprecipitation results confirmed that PELP1 constitutively associates with MT-ER. PELP1 knock-down or treatment with PELP1 inhibitor SMIP34 significantly reduced proliferation of the four MT-ER models with an IC50 of 3-5μM. PELP1 knock-down or SMIP34 treatment significantly reduced the constitutive ERE reporter activity observed in MT-ER models. RTqPCR assays confirmed the downregulation of MT-ER target genes in PELP1 knock-down and SMIP34 treated cells. Furthermore, PELP1 knock-down or SMIP34 treatment significantly reduced the invasiveness and colony formation of MT-ER BCa models. Mechanistic studies using Western blot revealed that SMIP34 contributes to PELP1 degradation by its direct binding to PELP1. SMIP34 significantly decreased proliferation of MT-ER BCa cells in XDEX andPDEX assays, as measured by Ki67 staining. Conclusion: Our results suggest that PELP1 associates with MT-ER and targeting the PELP1 axis with SMIP34will have therapeutic utility in treating MT-ER driven BCa. Supported by CPRIT Predoctoral Fellowship CPRIT RTA; RP170345 (K.A. Altwegg) and VA grant I01BX004545(R.K.V)

Citation Format: Kristin A Altwegg, Suryavathi Viswanadhapalli, Junhao Liu, Zexuan Liu, Uday P. Pratap, Benham Ebrahimi, Hariprasad Vankayalapati, Ratna K. Vadlamudi. Targeting the PELP1 axis for treating ESR1 mutant driven breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-15.

Abstract PS17-09: Development of a potent mutant-ESR1 targeted agent, ERX-245, for treating metastatic therapy-resistant breast cancer

Background: ESR1 mutations are acquired following ERα targeted therapies and are a major determinant of therapy-resistance. These ESR1 mutations maintain ESR1 signaling, albeit in a ligand-independent manner. Effective drugs targeting these mutant (MT) ERα proteins represent a significant unmet clinical need. We had previously shown that ERX-11, an ESR1-coregulator binding inhibitor, could block the function of these MT ERα proteins. In this study, we sought to leverage recently published structures of MT ERα to develop more potent analogues of ERX-11. Methods: Virtual screening of >250,000 derivatives of ERX-11 was performed with simulated docking on the MT ERα to identify and design analogues of ERX-11. Several hundred analogues were synthesized and tested in vitro using multiple BC model cells that express wild type (WT) ESR1 or mutant (MT) ESR1 (Y537S or D538G). Mechanistic studies were performed using RNA-Seq, Western blotting, qRT-PCR and reporter gene assays. The in vivo efficacy of the most potent ERX-11 analogue ERX-245 was examined using xenograft, PDX and metastatic models of MT-ER driven BC. Results: From our virtual and functional screen, we identified an ERX-11 analogue, ERX-245 as the most potent hit to target MT-ERα. Docking studies modeled a better fit of ERX-245 into the ligand binding domain of both the Y537S and D538G MT-ERα. ERX-245 potently reduced (IC50 ~250 nM) the cell viability of both WT-ERα and MT-ERα driven BC cells but not ERα negative BC cells. ERX-245 significantly reduced the growth (colony formation, clonogenic and mammosphere assays) of MT-ERα BC cells. ERX-245 exhibited synergistic activity in combination with CDK4/6 inhibitors. In distinction to classic SERDs like fulvestrant (which degrade ERα with in 4h), ERX-245 treatment decreased MT-ERα protein levels over 24 hours. PK studies indicated that ERX-245 is more polar and has better solubility and pharmacokinetic properties than ERX-11. ERX-245 reduced tumor growth of subcutaneous xenograft and PDX models driven by MT-ERα as well as the proliferation of xenograft derived MT-ERα explant models. ERX-245 significantly reduced the invasive capability of MT-ERα BC cells in vitro and inhibited both the metastatic capability and growth of metastatic tumors derived from MT-ERα BC cells injected by intracardiac or intratibial routes. Conclusions: Taken together, these results indicate that ERX-245 is a potent and pharmacologically translatable analog of ERX-11, with activity against both primary and metastatic tumors driven by MT-ERα.

Citation Format: Ganesh V Raj, Suryavathi Viswanadhapalli, Karla Parra, Shihong Ma, Tae-Kyung Lee, Xihui Liu, Kara Kassees, Weiwei Tang, Junhao Liu, Zexuan Liu, Uday P Pratap, Behnam Ebrahimi, Rajeshwar Rao Tekmal, Jung-Mo Ann, Ratna K Vadlamudi. Development of a potent mutant-ESR1 targeted agent, ERX-245, for treating metastatic therapy-resistant breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-09.

Activation of estrogen receptor beta signaling reduces stemness of glioma stem cells

Glioblastoma (GBM) is the most common and deadliest tumor of the central nervous system. GBM has poor prognosis and glioma stem cells (GSCs) are implicated in tumor initiation and therapy resistance. Estrogen receptor β (ERβ) is expressed in GBM and exhibit tumor suppressive function. However, the role of ERβ in GSCs and the therapeutic potential of ERβ agonists on GSCs remain largely unknown. Here, we examined whether ERβ modulates GSCs stemness and tested the utility of two ERβ selective agonists (LY500307 and Liquiritigenin) to reduce the stemness of GSCs. The efficacy of ERβ agonists was examined on GSCs isolated from established and patient derived GBMs. Our results suggested that knockout of ERβ increased the proportion of CD133+ and SSEA+ positive GSCs and overexpression of ERβ reduced the proportion of GSCs in GBM cells. Overexpression of ERβ or treatment with ERβ agonists significantly inhibited the GSCs cell viability, neurosphere formation, self-renewal ability, induced the apoptosis and reduced expression of stemness markers in GSCs. RNA sequencing analysis revealed that ERβ agonist modulate pathways related to stemness, differentiation and apoptosis. Mechanistic studies showed that ERβ overexpression or agonist treatment reduced glutamate receptor signaling pathway and induced apoptotic pathways. In orthotopic models, ERβ overexpression or ERβ agonists treatment significantly reduced the GSCs mediated tumor growth and improved the mice overall survival. Immunohistochemical studies demonstrated that ERβ overexpression decreased SOX2 and GRM3 expression and increased expression of GFAP in tumors. These results suggest that ERβ activation could be a promising therapeutic strategy to eradicate GSCs.

Histone deacetylase inhibitors enhance estrogen receptor beta expression and augment agonist-mediated tumor suppression in glioblastoma

BACKGROUND

Glioblastomas (GBMs) are the most lethal primary brain tumors. Estrogen receptor β (ESR2/ERβ) function as a tumor suppressor in GBM, however, ERβ expression is commonly suppressed during glioma progression. In this study, we examined whether drugs that reverse epigenetic modifications will enhance ERβ expression and augment ERβ agonist-mediated tumor suppression.

METHODS

We tested the utility of epigenetic drugs which act as an inhibitor of histone deacetylases (HDACs), histone methylases, and BET enzymes. Mechanistic studies utilized RT-qPCR, chromatin immunoprecipitation (ChIP), and western blotting. Cell viability, apoptosis, colony formation, and invasion were measured using in vitro assays. An orthotopic GBM model was used to test the efficacy of in vivo.

RESULTS

Of all inhibitors tested, HDACi (panobinostat and romidepsin) showed the potential to increase the expression of ERβ in GBM cells. Treatment with HDACi uniquely upregulated ERβ isoform 1 expression that functions as a tumor suppressor but not ERβ isoform 5 that drives oncogenic functions. Further, combination therapy of HDACi with the ERβ agonist, LY500307, potently reduced cell viability, invasion, colony formation, and enhanced apoptosis. Mechanistic studies showed that HDACi induced ERβ is functional, as it enhanced ERβ reporter activities and ERβ target genes expression. ChIP analysis confirmed alterations in the histone acetylation at the ERβ and its target gene promoters. In orthotopic GBM model, combination therapy of panobinostat and LY500307 enhanced survival of tumor-bearing mice.

CONCLUSIONS

Our results suggest that the combination therapy of HDACi and LY500307 provides therapeutic utility in overcoming the suppression of ERβ expression that commonly occurs in GBM progression.

Abstract 4377: HDAC inhibitors enhance ESR2 expression and augment response to ESR2 agonist therapy

Background: Glioblastomas (GBM) are the most common and lethal primary brain tumors that have dismal survival rates. The estrogen receptor β (ESR2) functions as a tumor suppressor in glioblastoma (GBM). However, ESR2 expression is commonly suppressed during glioma progression with low expression in higher grades. In this study, we explored the hypothesis that aberrant epigenetic changes may contribute to loss of expression of the ESR2 and drugs that reverse these modifications will enhance ESR2 agonist-mediated tumor suppression by upregulating ESR2 expression.

Methods: We tested utility of epigenetic drugs currently in clinical trials which acts as inhibitor of HDAC (Belinostat, Givinostat, panobinostat, romidepsin), DNMT (Decitabine), histone methylases (BIX-01294) and Bet enzymes (I-BET151) in upregulating ESR2 using both established and primary GBM models. The effect of combination therapy of HDAC inhibitors (HDACIs) along ESR2 agonist was evaluated using cell viability, colony formation, Caspase 3/7, TUNEL, and neurosphere formation assays. Mechanistic studies were performed using Western blot, qRT-PCR, ChIP and ERE reporter assays. The efficacy of combination therapy in vivo was examined using orthotopic models of GBM and mouse survival was determined using Kaplan-Meier survival curves.

Results: Of all inhibitors tested, only two HDACis (panobinostat and romidepsin) showed the potential to increase the expression of ESR2 in established GBM model cells (U87 and U251). Upregulation of ESR2 by HDACi was also validated using primary GBM cells. Treatment with panobinostat or romidepsin uniquely upregulated ESR2 isoform-1 expression that functions as a tumor suppressor but not the ERS2 isoform-5 that drives oncogenic functions. Further, combination therapy of panobinostat with ESR2 agonist LY500307 synergistically reduced cell viability, colony formation and enhanced apoptosis. Mechanistic studies showed that panobinostat induced ESR2 is functional, as it enhanced ESR2 mediated ERE-, SP1-, AP1- reporter activities and ESR target genes involved in apoptosis. ChIP analysis confirmed alteration in the histone acetylation in the ESR2 promoter region. In orthotopic GBM models, combination therapy of panobinostat and LY500307 enhanced survival of tumor-bearing mice.

Conclusions: Our results suggest that the combination therapy of HDACIs and LY500307 provides therapeutic utility in overcoming the suppression of ESR2 expression that commonly occurs in GBM progression. Supported by NIH grant CA178499 (RKV)

Citation Format: Uday P. Pratap, Gangadhara R. Sareddy, Suryavathi Viswanadhapalli, Weiwei Tang, Prabhakar Pitta Venkata, Junhao Liu, Rajeshwar R. Tekmal, Andrew Brenner, Ratna K. Vadlamudi. HDAC inhibitors enhance ESR2 expression and augment response to ESR2 agonist therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4377.

Abstract 6403: Characterization of small molecule inhibitors of PELP1 for treating advanced breast cancer

Background: Breast cancer (BC) is the most commonly diagnosed cancer and the second leading cause of cancer death in American women. BC is composed of distinct molecular subtypes, such as ER positive BC (ER+) and triple negative BC (TNBC). Development of novel effective therapies for patients with therapy resistant BC (TR-BC) and TNBC remains the highest unmet need in patient treatment and survivorship. Proline, glutamic acid-, and leucine-rich protein 1 (PELP1) plays a critical role in multiple nuclear receptor functions leading to TR-BC and TNBC progression. PELP1 expression is dysregulated in BC, is a prognostic indicator of poorer BC survival, and its deregulation contributes to TR-BC. The objective of this study is characterization of a small molecule inhibitor of PELP1 (SMIP34) as novel therapeutic for treating advanced BC.

Methods: Yeast two-hybrid screening was used to identify PELP1 Inhibitory Peptide 1 (PIP1). Direct binding of PIP1 to PELP1 was confirmed using biotin pull-down assays and inhibition of BC proliferation confirmed using MTT assays. Hit-Ligand interaction site with PIP1 hot spot residues based on 3D alignment and morphology was used to generate a library of small chemical molecules that function as peptidomimetics of PIP1. In vitro activity was assessed using CellTiter Glo, MTT, colony formation and matrigel invasion assays in multiple BC models. Mechanistic studies were conducted using Western blot, and reporter gene assays. Xenograft and patient derived explant (PDEX) assays were used for preclinical evaluation.

Results: Screening utilizing MTT assays lead to the selection of SMIP34 as an inhibitor of PELP1. SMIP34 treatment reduced cell viability at an IC50 of 3-10µM in a panel of BC cells. Additionally, SMIP34 showed no activity in human mammary epithelial cells. Knockdown of PELP1 in BC cells significantly reduced the SMIP34 activity, confirming target specificity. Furthermore, SMIP34 treatment significantly reduced the invasiveness and colony formation of TR-BC and TNBC cells. Mechanistic studies using Western blot analysis confirmed that SMIP34 binding to PELP1 contributes to its degradation. In combination studies, SMIP34 displayed synergy and enhanced the efficacy of current chemotherapeutics Cisplatin and Paclitaxel. In PDEX assays, SMIP34 significantly decreased tumor proliferation as measured by Ki67 staining. In xenograft models, SMIP34 (10mg/kg/s.c.) treatment resulted in significant reduction in tumor volume compared to vehicle control. Furthermore, overall mouse body weight in both control and SMIP34 treated groups were similar, suggesting no overt signs of toxicity.

Conclusion: We have developed a first-in-class small molecule inhibitor of PELP1 (SMIP34) displaying therapeutic efficacy against TR-BC and TNBC in vitro, ex vivo, and in vivo.

Supported by CPRIT Predoctoral Fellowship CPRIT RTA; RP170345 (K.A. Altwegg) and VA grant I01BX004545 (R.K.V)

Citation Format: Kristin Ann Altwegg, Suryavathi Viswanadhapalli, Monica Mann, Uday P. Pratap, Mengxing Li, Junhao Liu, Yiliao Luo, Gangadhara R. Sareddy, Hariprasad Vankayalapati, Ratna K. Vadlamudi. Characterization of small molecule inhibitors of PELP1 for treating advanced breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6403.

Abstract 562: Novel combination therapy for treating TNBC using LIFR and HDAC Inhibitors

Background: Triple-negative breast cancer (TNBC) lacks targeted therapies and represents a disproportional share of the breast cancer (BC) mortality rate. TNBC exhibits autocrine stimulation of the LIF/LIFR axis and overexpression of LIF is associated with poorer relapse-free survival in BC patients. Histone deacetylase inhibitors (HDACIs) are emerging as promising multifunctional agents in TNBC to elicit cytotoxic actions. Recent studies have shown that cancer cells elicit feedback activation of leukemia inhibitory factor receptor (LIFR) which in turn curtails response to HDACIs. We developed a first-in-class inhibitor of LIFR, EC359 that directly interacts with LIFR and effectively blocks LIFR downstream signaling. The objective of this study is to examine the therapeutic efficacy of combination therapy using preclinical and patient-derived xenograft (PDX) models.

Methods: We tested utility of combination therapy using multiple HDACIs that are currently in clinical trails along with EC359. The effect of combination therapy was evaluated using MTT, invasion, colony formation, and Caspase3/7 assays. Mechanistic studies were performed using Western blotting, qRT-PCR, and STAT3 reporter assays. The efficacy of combination therapy in vivo was examined using xenograft, PDX, and patient-derived explant (PDEx) models.

Results: Immunohistochemical analyses of breast tumors using tissue microarrays revealed significant expression of LIFR in TNBC tissues. Treatment of TNBC model cells with four different HDACIs increased the expression of LIFR. LIFR inhibitor EC359 at nM concentration is additive to HDACIs in reducing cell viability. Knockdown of LIFR or treatment with EC359 significantly enhanced the efficacy of HDACIs in reducing the cell viability, colony formation ability, and invasiveness as well as promoted apoptosis compared to monotherapy in TNBC model cells. On the contrary, treatment with STAT3 inhibitor requires µM concentrations to reduce the cell viability of TNBC cells and is not additive to HDACIs. Mechanistic studies utilizing STAT3 reporter gene assays and biochemical studies using multiple TNBC model cells exhibited activation of the LIFR signaling pathway upon HDACIs treatment but was attenuated by EC359 therapy. Treatment of human TNBC utilizing PDEx assays showed that EC359 enhanced the ability of HDACIs to decrease proliferation (Ki-67 positivity) compared to monotherapy. Using TNBC xenografts and PDX models, we demonstrated that EC359 treatment enhanced the ability of HDACIs to reduce in vivo tumor growth compared to monotherapy.

Conclusions: Our results suggest that the combination therapy of HDACIs and EC359 provides therapeutic utility in overcoming the limitation of feedback activation of LIFR observed in the treatment of HDACIs in treating TNBC. Supported by DOD BCRP grant W81XWH-18-1-0016 (R.K. Vadlamudi; K.J. Nickisch)

Citation Format: Suryavathi Viswanadhapalli, Mengxing Li, Bindu Santhamma, Uday P. Pratap, Yiliao Luo, Junhao Liu, Kristin A. Altwegg, Xiaonan Li, Ahmed Gulzar, Hui Yan, Zhenming Xu, Andrew Brenner, Gangadhara R. Sareddy, Manjeet K. Rao, Rajeshwar R. Tekmal, Hareesh B. Nair, Klaus J. Nickisch, Ratna K. Vadlamudi. Novel combination therapy for treating TNBC using LIFR and HDAC Inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 562.

Abstract 5676: Preclinical evaluation of estrogen receptor coregulator binding inhibitor ERX-245 in breast cancer

Background: Breast cancer (BC) is the most common cancer in American women. Majority of BC (70%) is estrogen receptor alpha (ERα) positive and these tumors initially respond to ER-targeted therapy, however, acquired therapy-resistance limit the utility of ERα-targeted therapy using aromatase inhibitors and antiestrogens. Importantly, both therapy-sensitive and therapy-resistant tumors retain ESR1 signaling, via interaction with critical oncogenic coregulator proteins. We recently developed a small organic molecule, ESR1 coregulator binding inhibitor ERX-11. The objective of this study is to develop better analogues of ERX-11 using medicinal chemistry approaches.

Methods: Virtual screening of a quarter million compounds and medicinal chemistry approaches were used to design new analogues of ERX-11 and identified ERX-245 as potent analogue. Effect of ERX-245 was evaluated in vitro using multiple BC models that express wild type (WT) ERα (MCF-7, ZR-75) and BC models with acquired resistance (MCF-7-Tam, MCF-7-LTLT). Mechanistic studies were performed using RNA-Seq, Western blotting, qRT-PCR and reporter gene assays. The in vivo efficacy of ERX-245 was examined using xenograft, and xenograft-derived explant (XDEx) models.

Results: We initially performed an intensive virtual screening of a quarter million compounds and selected several candidates that showed strong binding energy to ERα. We then designed and developed several analogues of ERX-11 using modeled structural interactions. Using this approach, we identified ERX-245 as a potential lead compound for interaction with ERα. Like the parental ERX-11, ERX-245 significantly reduced the cell viability of both WT and therapy-resistant BC cells with an IC50 of 300-500 nM with minimal activity in ER-negative models such as TNBC cells. In long-term colony formation assays, ERX-245 significantly reduced the colony formation ability of both ER-WT and therapy-resistant BC cells. In ERE reporter assays, ERX-245 significantly reduced the estrogen-mediated reporter activity. ERX-245 significantly reduced the invasion of endocrine-resistant BC cells. RNA sequencing revealed unique pathways blocked by ERX-245. PK studies indicated that ERX-245 is more polar and has better solubility and pharmacokinetic properties compared to ERX-11. Treatment of ERX-245 decreased the proliferation and increased apoptosis (TUNEL staining) in xenograft derived explant (XDEx) models. ERX-245 also showed potent activity against WT-ERα and therapy-resistant xenograft models.

Conclusions: Collectively, these results suggest that the ERX-11 analogue ERX-245 has potential to therapeutically target endocrine therapy resistant BC.

Citation Format: Suryavathi Viswanadhapalli, Shihong Ma, Tae Kyung Lee, Xihui Liu, Kara Kassees, Uday P. Pratap, Junhao Liu, Weiwei Tang, Rajeshwar R. Tekmal, Jung-Mo Ahn, Ganesh V. Raj, Ratna K. Vadlamudi. Preclinical evaluation of estrogen receptor coregulator binding inhibitor ERX-245 in breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5676.

Abstract 4371: PELP1-TFAP2C crosstalk promotes endocrine resistance in breast cancer cells

Background: A significant proportion of estrogen receptor positive (ER+) breast cancer (BC) initially respond to antiestrogens or aromatase inhibitors but become therapy resistant-BC. Development of effective therapies for endocrine therapy resistant BC represent the highest unmet need. PELP1 is a nuclear receptor coregulator, commonly overexpressed in BC, contributes to therapy resistance and correlate with poor survival. TFAP2C (transcription factor AP-2 gamma) is a known regulator of ER activity and high expression of TFAP2C is associated with a decreased response to Fulvestrant. The objective of this study is to examine the significance of PELP1-TFAP2C crosstalk in the development of breast cancer therapy resistance.

Methods: We used yeast two-hybrid screen to identify PELP1 interacting transcription factors. Interaction of PELP1 and TFAP2C was confirmed by immunoprecipitation and GST pull down assays. Functional significance of the cross talk was tested using CellTiter-Glo, MTT and colony formation assays in the presence or absence of endocrine therapy. Mechanistic studies were conducted using shRNA, overexpression, Western blotting, reporter gene assays, RT-qPCR, ChIP-seq and RNA-seq analysis. Biological significance of PELP1 and TFAP2C in endocrine therapy resistance was examined using overexpression and under expression models of PELP1 and TFAP2C in multiple BC models including MCF7 and ZR75.

Results: Yeast based screening of a mammary gland cDNA expression library using PELP1 as the bait identified TFAP2C as a novel interacting protein of PELP1. Immunoprecipitation assays using multiple BC cell lysates confirmed the interaction of PELP1 with TFAP2C. Using various deletions of PELP1, and by using GST pull down assays, we identified N-terminal 400-600aa region of PELP1 as the major interaction site for TFAP2C. Using RNA-seq of PELP1 knockdown BC model cells, we predicted TFAP2C as an enriched transcription factor in PELP1 regulated genes. The GSEA results from RNA-seq showed TFAP2C and PELP1 induce a subset of common genes. Reporter gene assays confirmed that PELP1 functions as a coactivator of TFAP2C. Mechanistic studies showed that TFAP2C activates both AKT and ERK pathways in ER+ cell lines, while knock down of PELP1 attenuated these effects. Overexpression of TFAP2C contributed to increased cell proliferation and endocrine therapy resistance in MCF7 and ZR75 models, while knock down of PELP1 attenuated these effects. Utilizing ZR75-TFAP2C xenograft models with WT PELP1 or PELP1 knock down, we provided genetic evidence that endogenous PELP1 is essential for TFAP2C drive n breast cancer progression in vivo.

Conclusions: Collectively, our studies demonstrated that PELP1 functions as a coactivator of TFAP2C in modulating a set of ER target genes, TFAP2C functions as a transcription factor of PELP1 regulated genes and blocking the PELP1-TFAP2C axis could have therapeutic utility for treating therapy resistance. Supported by VA grant I01BX004545 (R.K. Vadlamudi)

Citation Format: Junhao Liu, Suryavathi Viswanadhapalli, Mengxing Li, Uday P. Pratap, Weiwei Tang, Zexuan Liu, Yiliao Luo, Kristin A. Altwegg, Xiaonan Li, Gangadhara R. Sareddy, Rajeshwar R. Tekmal, Ratna K. Vadlamudi. PELP1-TFAP2C crosstalk promotes endocrine resistance in breast cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4371.

Sex-Based Differences in the Cytokine Production and Intracellular Signaling Pathways in Patients With Rheumatoid Arthritis

Objectives

This study aims to investigate lymphoproliferation, cytokine production, and intracellular signaling molecules in peripheral blood mononuclear cells (PBMCs) isolated from healthy individuals and rheumatoid arthritis (RA) patients to understand the extent of the involvement of these pathways in the pathogenesis of RA.

Patients and methods

The study included 65 participants (29 males, 36 females; mean age 51.8±10.3 years; range, 37 to 71 years) who were categorized into four groups as healthy males (n=22, mean age 49.8±10.6 years; range, 39 to 65 years), male RA patients (n=7, mean age 51.8±13.9 years; range, 37 to 68 years), healthy females (n=20, mean age 53.7±8.8 years; range, 42 to 67 years), and female RA patients (n=16, mean age 52.9±10.4 years; range, 40 to 71 years). PBMCs were collected from the participants and analyzed for Concanavalin A (Con A)-induced lymphoproliferation using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, cytokine production, and phospho-signal transducer and activator of transcription 3 (p-STAT-3), phospho-extracellular-signal-regulated kinase (p-ERK), phospho-cAMP response element binding (p-CREB), and phospho-protein kinase B expressions using enzyme-linked immunosorbent assay. Short form of the Arthritis Impact Measurement Scales 2 and multidimensional health assessment questionnaire were used to measure the level of disability and the quality of life.

Results

In RA patients, production of Con A-induced interleukin (IL)-2 and IL-17 was higher in both sexes while interferon-gamma levels decreased in RA females alone. Expression of p-STAT-3 in PBMCs increased in RA males while it was unaltered in RA females. p-ERK expression was not altered while p-CREB expression was enhanced in RA males and females. Protein-protein interaction analyses demonstrated that these and other key signaling molecules were dysregulated in RA patients.

Conclusion

Our results suggest that sex-based differences in RA pathogenesis result from differential alterations in signaling pathways to influence the inflammatory process.

Abstract P6-04-14: The role of PELP1-TFAP2C crosstalk in mediating endocrine-therapy-resistance in breast cancer

Background: A significant proportion of estrogen receptor (ER) positive (ER+) breast cancer (BC) initially respond to endocrine therapies, such as antiestrogens or aromatase inhibitors. However, ER+ BC can build up resistance to treatment progressing into therapy resistant-BC (TR-BC). Development of effective therapeutics for endocrine-therapy-resistant BC represents a significant unmet need in BC treatment options. Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) is oncogenic nuclear receptor coregulator, commonly overexpressed in BC. PELP1 overexpression is correlated with poorer patient survival and is associated with development of TR-BC. TFAP2C (AP2Gamma) is a known regulator of ER activity. In addition, high expression of TFAP2C is associated with a decreased response to the steroidal antiestrogen, Fulvestrant. However, it remains unknown whether PELP1 and TFAP2C crosstalk and if the PELP1/TFAP2C axis behaves synergistically to contribute to the development of therapy resistance in TR-BC. Methods: To gain insight into PELP1 signaling mechanisms, we used yeast two-hybrid screen to identify proteins that interact with PELP1. The interaction between PELP1 and TFAP2C was confirmed by immunoprecipitation using both endogenous and GFP tagged proteins. GST fusions of various domains of PELP1 were used to identify the TFAP2C interacting domain. Functional significance of the crosstalk was tested using Celltiter Glo, MTT, apoptosis, and invasion assays. Mechanistic studies were conducted using shRNA, overexpression, Western Blot, reporter gene assays, RT-qPCR, ChIP and RNA-Seq analysis. Biological significance of PELP1 and TFAP2C in endocrine-therapy-resistance was examined using overexpression and under-expression models of PELP1 and TFAP2C in multiple ER+ BC and TR-BC model cells (MCF-7, ZR-75, T-47D, MCF-7-TamR, MCF7-LTLT and ZR75-ERMT537S. Results: Screening of a mammary gland cDNA expression library using PELP1 as the bait identified TFAP2C as a novel interacting protein of PELP1. Immunoprecipitation assays utilizing multiple BC cell lysates confirmed interaction of PELP1 with TFAP2C. We also confirmed PELP1 and TFAP2C interactions using GFP and GST epitope tagged proteins. Using GST fusion of various domains of PELP1, we identified the PELP1 N-terminal domain (aa 400-600) as the major interaction site for TFAP2C. Using PELP1 knockdown BC model cell lines with RNA-Seq analysis, we identified a set of genes regulated by PELP1. The GSEA results from the RNA-Seq data predicted TFAP2C as an enriched transcription factor in a subset of PELP1 regulated genes. RT-qPCR analysis confirmed that PELP1 is needed for optimal regulation of the ER and associated ER target genes by TFAP2C. Reporter gene assays confirmed that PELP1 functions as a coregulator of TFAP2C. Overexpression of TFAP2C contributed to endocrine-therapy-resistance in BC model cells, while knockdown of PELP1 abolished TFAP2C mediated therapy resistance. Conclusions: Collectively, our studies identified PELP1 functions as a coregulator of TFAP2C in modulating ER target genes. TFAP2C functions as a transcription factor of PELP1 regulated genes and blocking the PELP1-TFAP2C axis will have therapeutic utility for treating TR-BC

Citation Format: Junhao Liu, Suryavathi Viswanadhapalli, Mengxing Li, Uday P Pratap, Yiliao Luo, Kristin A Altwegg, Xiaonan Li, Gangadhara R Sareddy, Rajeshwar R Tekmal, Ratna K Vadlamudi. The role of PELP1-TFAP2C crosstalk in mediating endocrine-therapy-resistance in breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-04-14.

Abstract P3-11-08: Targeting LIFR enhances the activity of HDAC inhibitors for the treatment of triple negative breast cancer

Background: Triple-negative breast cancer (TNBC) is a heterogeneous disease. TNBC lacks targeted therapies and represents a disproportional share of the breast cancer (BC) mortality rate. Histone deacetylase inhibitors (HDACIs) are emerging as promising multifunctional agents in TNBC to elicit cytotoxic actions. Recent studies have shown that cancer cells elucidate feedback activation of leukemia inhibitory factor receptor (LIFR) which in turn curtails response to HDACIs. We developed a first-in-class inhibitor of LIFR, EC359 that directly interacts with LIFR and effectively blocks LIFR downstream signaling. Here, we examined whether the novel LIFR inhibitor, EC359, has the ability to counteract negative effects of LIFR signaling to enhance HDACIs therapeutic efficacy in the treatment of TNBC.

Methods: We tested multiple HDACIs currently in clinical trials including vorinostat, panobinostat, romidepsin, and givinostat using multiple TNBC models. The effect of combination therapy of HDACIs and EC359 on TNBC cell viability and invasion was examined using MTT assays and matrigel invasion assays respectively. The efficacy of combination therapy on cell survival and apoptosis was determined using clonogenic assays and Caspase 3/7 assays, respectively. Mechanistic studies were performed using Western blotting, qRT-PCR, and reporter gene assays. The efficacy of combination therapy in vivo was examined using Xenograft, patient-derived xenograft (PDX), and patient-derived explant (PDEX) models.

Results: We demonstrated that the treatment of TNBC models with HDACIs increased the expression of LIFR. Immunohistochemistry analyses of breast tumors using tissue microarrays revealed significant expression of LIFR in TNBC samples. Knockdown of LIFR or treatment with a small molecule inhibitor of LIFR (EC359) significantly enhanced the efficacy of HDACIs in reducing cell viability, colony formation ability, and invasiveness as well as promoted apoptosis compared to monotherapy of HDACIs or EC359 in TNBC cell lines. Mechanistic studies, reporter gene assays and biochemical studies using multiple TNBC models exhibited activation of the LIFR signaling pathway upon HDACIs treatment but was attenuated by EC359+HDACI combination therapy. Treatment of human breast tumors utilizing PDEX assays showed that EC359 enhanced the ability of HDACIs to decrease the proliferation (Ki-67 positivity) compared to monotherapy. Furthermore, using TNBC xenografts and PDX models, we demonstrated that EC359 treatment enhanced the ability of HDACIs to reduce in vivo tumor growth compared to monotherapy.

Conclusions: Our results suggest that the combination therapy of HDACIs and EC359 provides greater therapeutic efficacy than monotherapy. In addition, treatment with EC359 can overcome the feedback activation of LIFR currently observed in the treatment of TNBC with HDACIs.

Citation Format: Suryavathi Viswanadhapalli, Mengxing Li, Bindu Santhamma, Uday P Pratap, Yiliao Luo, Junhao Liu, Kristin A Altwegg, Xiaonan Li, Hui Yan, Zhenming Xu, Andrew Brenner, Gangadhara R Sareddy, Rajeshwar R Tekmal, Hareesh B Nair, Klaus J Nickisch, Ratna K Vadlamudi. Targeting LIFR enhances the activity of HDAC inhibitors for the treatment of triple negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-11-08.

Abstract P3-10-01: Development and characterization of a first-in-class small molecule inhibitor of PELP1

Background: Breast cancer (BCa) is the most commonly diagnosed cancer and the second leading cause of cancer death in women. BCa is composed of distinct molecular subtypes, such as ER positive BCa (ER+ BCa) and triple negative BCa (TNBC). Development of novel effective therapies for patients with therapy resistant breast cancer (TR-BC) and TNBC remains the highest unmet need in patient treatment and survivorship. Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) plays a critical role in multiple nuclear receptor functions leading to TR-BC and TNBC progression. PELP1 expression is dysregulated in BCa, is a prognostic indicator of poorer BCa survival, and its deregulation contributes to BCa therapy resistance. The objective of this study is development and characterization of a small molecule inhibitor of PELP1 (SMIP) as novel therapeutic for treating BCa.

Methods: Using yeast two-hybrid screening, we identified PELP1 Inhibitory Peptide (PIP1) from a library of peptides. PIP1 binds PELP1 with high affinity and functions to inhibit PELP1 oncogenic activity. Direct binding of PIP1 to PELP1 was confirmed using biotin pull-down assays and inhibition of BCa proliferation confirmed using MTT assays. We used the Hit-Ligand interaction site with PIP1 hot spot residues based on 3D alignment and morphology to generate a library of peptidomimetics (small chemical molecules). In vitro activity was assessed using Celltiter Glo, MTT, and matrigel invasion chamber assays in multiple BCa models. Mechanistic studies were conducted using Western blot, reporter gene assays, and peptide competition assays. Xenograft and patient derived explant (PDEX) assays were used for preclinical evaluation and preliminary toxicity analysis.

Results: Bioactivity screens revealed PELP1 Inhibitory Peptide (PIP1) significantly attenuates PELP1-mediated proliferation with an IC50 of 10µM across multiple BCa cell lines. We confirmed PIP1 binding to PELP1 using peptide pull-down assays with nuclear lysates from BCa cells. Using Hit-Ligand-Based interaction site with the PIP1 hot spot residues, we identified 61 potential hits using a 10,000 Diverse Set. Screening of these 61 potential hits using the MTT assays lead to the selection of SMIP34 (tetrahydropyrazolo [1,5a) pyrazole) as lead inhibitor of PELP1. SMIP34 treatment reduced proliferation at an IC50 of 3-10µM in ER+ BCa (ZR-75, MCF-7, and T- 47D); TR-BC (MCF-7-TamR, MCF-7-LTLT, ZR-75-MT-ER537S, and ZR-75-MT-ER538G); and TNBC (MDA- MB-231, and BT549) models. Additionally, SMIP34 showed no activity in human mammary epithelial cells. Specificity of SMIP34 was confirmed using PELP1 knockdown BCa cell lines. Mechanistic studies using Western blot analysis confirmed that SMIP34 binding to PELP1 contributes to its degradation. In matrigel invasion chamber assays, SMIP34 significantly reduced the invasiveness of TR-BC and TNBC models. In combination studies, SMIP34 displayed synergy and enhanced the efficacy of current chemotherapeutics Cisplatin and Paclitaxel. In PDEX assays, Ki67 staining revealed SMIP34 significantly decreased tumor proliferation. In xenograft models, SMIP34 (10mg/kg/s.c.) treatment resulted in significant reduction in tumors compared to vehicle treatment. Furthermore, overall mouse body weight in both control and SMIP34 treated groups were similar, suggesting no overt signs of toxicity.

Conclusion: We have developed a first-in-class small molecule inhibitor of PELP1 (SMIP) displaying effectivity against TR-BC and TNBC in vitro and in vivo.

Supported by CPRIT Predoctoral Fellowship CPRIT RTA; RP170345 (K.A. Altwegg)

Citation Format: Kristin A Altwegg, Suryavathi Viswanadhapalli, Monica Mann, Uday P Pratap, Mengxing Li, Junhao Liu, Yiliao Luo, Gangadhara R Sareddy, Hariprasad Vankayalapati, Ratna K. Vadlamudi. Development and characterization of a first-in-class small molecule inhibitor of PELP1 [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-10-01.

Estrogen receptor coregulator binding modulator (ERX-11) enhances the activity of CDK4/6 inhibitors against estrogen receptor-positive breast cancers

BACKGROUND

CDK4/6 inhibitors in combination with endocrine therapy (AE/AI/SERDs) are approved for the treatment of ER+ advanced breast cancer (BCa). However, not all patients benefit from CDK4/6 inhibitors therapy. We previously reported a novel therapeutic agent, ERX-11, that binds to the estrogen receptor (ER) and modulates ER-coregulator interactions. Here, we tested if the combination of ERX-11 with agents approved for ER+ BCa would be more potent.

METHODS

We tested the effect of combination therapy using BCa cell line models, including those that have acquired resistance to tamoxifen, letrozole, or CDK4/6 inhibitors or have been engineered to express mutant forms of the ER. In vitro activity was tested using Cell Titer-Glo, MTT, and apoptosis assays. Mechanistic studies were conducted using western blot, reporter gene assays, RT-qPCR, and mass spectrometry approaches. Xenograft, patient-derived explants (PDEs), and xenograft-derived explants (XDE) were used for preclinical evaluation and toxicity.

RESULTS

ERX-11 inhibited the proliferation of therapy-resistant BCa cells in a dose-dependent manner, including ribociclib resistance. The combination of ERX-11 and CDK4/6 inhibitor was synergistic in decreasing the proliferation of both endocrine therapy-sensitive and endocrine therapy-resistant BCa cells, in vitro, in xenograft models in vivo, xenograft-derived explants ex vivo, and in primary patient-derived explants ex vivo. Importantly, the combination caused xenograft tumor regression in vivo. Unbiased global mass spectrometry studies demonstrated profound decreases in proliferation markers with combination therapy and indicated global proteomic changes in E2F1, ER, and ER coregulators. Mechanistically, the combination of ERX-11 and CDK4/6 inhibitor decreased the interaction between ER and its coregulators, as evidenced by immunoprecipitation followed by mass spectrometry studies. Biochemical studies confirmed that the combination therapy significantly altered the expression of proteins involved in E2F1 and ER signaling, and this is primarily driven by a transcriptional shift, as noted in gene expression studies.

CONCLUSIONS

Our results suggest that ERX-11 inhibited the proliferation of BCa cells resistant to both endocrine therapy and CDK4/6 inhibitors in a dose-dependent manner and that the combination of ERX-11 with a CDK4/6 inhibitor may represent a viable therapeutic approach.

PELP1 signaling contributes to medulloblastoma progression by regulating the NF-κB pathway

Medulloblastoma (MB) is the most common and deadliest brain tumor in children. Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) is a scaffolding protein and its oncogenic signaling is implicated in the progression of several cancers. However, the role of PELP1 in the progression of MB remains unknown. The objective of this study is to examine the role of PELP1 in the progression of MB. Immunohistochemical analysis of MB tissue microarrays revealed that PELP1 is overexpressed in the MB specimens compared to normal brain. Knockdown of PELP1 reduced cell proliferation, cell survival, and cell invasion of MB cell lines. The RNA-sequencing analysis revealed that PELP1 knockdown significantly downregulated the pathways related to inflammation and extracellular matrix. Gene set enrichment analysis confirmed that the PELP1-regulated genes were negatively correlated with nuclear factor-κB (NF-κB), extracellular matrix, and angiogenesis gene sets. Interestingly, PELP1 knockdown reduced the expression of NF-κB target genes, NF-κB reporter activity, and inhibited the nuclear translocation of p65. Importantly, the knockdown of PELP1 significantly reduced in vivo MB progression in orthotopic models and improved the overall mice survival. Collectively, these results suggest that PELP1 could be a novel target for therapeutic intervention in MB.

PELP1 promotes glioblastoma progression by enhancing Wnt/β-catenin signaling

Background

Glioblastoma (GBM) is a deadly neoplasm of the central nervous system. The molecular mechanisms and players that contribute to GBM development is incompletely understood.

Methods

The expression of PELP1 in different grades of glioma and normal brain tissues was analyzed using immunohistochemistry on a tumor tissue array. PELP1 expression in established and primary GBM cell lines was analyzed by Western blotting. The effect of PELP1 knockdown was studied using cell proliferation, colony formation, migration, and invasion assays. Mechanistic studies were conducted using RNA-seq, RT-qPCR, immunoprecipitation, reporter gene assays, and signaling analysis. Mouse orthotopic models were used for preclinical evaluation of PELP1 knock down.

Results

Nuclear receptor coregulator PELP1 is highly expressed in gliomas compared to normal brain tissues, with the highest expression in GBM. PELP1 expression was elevated in established and patient-derived GBM cell lines compared to normal astrocytes. Knockdown of PELP1 resulted in a significant decrease in cell viability, survival, migration, and invasion. Global RNA-sequencing studies demonstrated that PELP1 knockdown significantly reduced the expression of genes involved in the Wnt/β-catenin pathway. Mechanistic studies demonstrated that PELP1 interacts with and functions as a coactivator of β-catenin. Knockdown of PELP1 resulted in a significant increase in survival of mice implanted with U87 and GBM PDX models.

Conclusions

PELP1 expression is upregulated in GBM and PELP1 signaling via β-catenin axis contributes to GBM progression. Thus, PELP1 could be a potential target for the development of therapeutic intervention in GBM.

Virgin coconut oil supplementation in diet modulates immunity mediated through survival signaling pathways in rats

Background Virgin coconut oil (VCO), a cold processed form of coconut oil, is traditionally consumed in Asian countries owing to its nutritional and medicinal properties. The aim of this study was to investigate whether the health benefits of VCO involve alterations in immune responses that are regulated by intracellular signaling molecules in the spleens of rats. Methods Young male Wistar rats were fed with three doses of VCO in diet for 30 days. At the end of the treatment period, spleens were isolated and in vitro effects on immune responses (Concanavalin A [Con A]-induced lymphoproliferation and cytokine production), and direct effects of VCO treatment on intracellular signaling molecules and antioxidant status were examined. Serum was collected to measure glucose, lipid levels, and leptin. Results VCO supplementation in diet enhanced Con A-induced splenocyte proliferation and Th1 cytokine production while it suppressed the proinflammatory cytokine production. VCO increased the expression of mechanistic target of rapamycin (p-mTOR), sirtuin1 (SIRT1), liver kinase B1 (p-LKB1) p-ERK, and p-CREB in spleen. Similarly, VCO increased the activities of antioxidant enzymes while it suppressed lipid peroxidation in the spleen. VCO diet had hypolipidemic effects on the rats: an increase in high density lipoprotein cholesterol (HDL-C) levels while lowering triacylglycerol (TAG) levels. Conclusion The health benefits of VCO may be mediated through enhanced Th1 immunity through the upregulation of survival signaling pathways and inhibition of free radical generation in the spleen besides its capacity to induce hypolipidemia.