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.

The LIFR Inhibitor EC359 Effectively Targets Type II Endometrial Cancer by Blocking LIF/LIFR Oncogenic Signaling

Endometrial cancer (ECa) is the most common female gynecologic cancer. When comparing the two histological subtypes of endometrial cancer, Type II tumors are biologically more aggressive and have a worse prognosis than Type I tumors. Current treatments for Type II tumors are ineffective, and new targeted therapies are urgently needed. LIFR and its ligand, LIF, have been shown to play a critical role in the progression of multiple solid cancers and therapy resistance. The role of LIF/LIFR in the progression of Type II ECa, on the other hand, is unknown. We investigated the role of LIF/LIFR signaling in Type II ECa and tested the efficacy of EC359, a novel small-molecule LIFR inhibitor, against Type II ECa. The analysis of tumor databases has uncovered a correlation between diminished survival rates and increased expression of leukemia inhibitory factor (LIF), suggesting a potential connection between altered LIF expression and unfavorable overall survival in Type II ECa. The results obtained from cell viability and colony formation assays demonstrated a significant decrease in the growth of Type II ECa LIFR knockdown cells in comparison to vector control cells. Furthermore, in both primary and established Type II ECa cells, pharmacological inhibition of the LIF/LIFR axis with EC359 markedly decreased cell viability, long-term cell survival, and invasion, and promoted apoptosis. Additionally, EC359 treatment reduced the activation of pathways driven by LIF/LIFR, such as AKT, mTOR, and STAT3. Tumor progression was markedly inhibited by EC359 treatment in two different patient-derived xenograft models in vivo and patient-derived organoids ex vivo. Collectively, these results suggest LIFR inhibitor EC359 as a possible new small-molecule therapeutics for the management of Type II ECa.

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.

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 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 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.

Profiling of Lipids, Nutraceuticals, and Bioactive Compounds Extracted from an Oilseed Rich in PUFA

Polyunsaturated fatty acid (PUFA) rich vegetable oils are nutritionally and economically important agriculture based commodities. The lipid profile, nutraceutical content, and antioxidant activity of Indian chia seed oil (CSO) were analysed and compared with PUFA rich vegetable oils. The total oil content was 28% (w/w) with α-linolenic acid (ALA; 65%) as the predominant fatty acid and a n-3/n-6 ratio of 3.5. The tocopherol content was 144 mg/kg of oil, with γ + β being the most abundant. The squalene content was 178.47 mg/100 g of oil, and the total phenolic content was 0.014 mg GAE/g of oil. The identity of major polyphenols in the methanolic extract of CSO were established by LC-HRMS. FTIR spectra of CSO exhibited characteristic features that were identical to other PUFA rich oils. Results demonstrate that the Indian CSO is an excellent source of essential fatty acids and key nutraceuticals.

Biochemical Characterization of Acyl-CoA: Lysophosphatidylcholine Acyltransferase (LPCAT) Enzyme from the Seeds of Salvia hispanica

Salvia hispanica (chia) is the highest reported terrestrial plant source of alpha-linolenic acid (ALA, ~ 65%), an ω-3 polyunsaturated fatty acid with numerous health benefits. The molecular basis of high ALA accumulation in chia is yet to be understood. We have identified lysophosphatidylcholine acyltransferase (LPCAT) gene from the developing seed transcriptome data of chia and carried out its biochemical characterization through heterologous expression in Saccharomyces cerevisiae. Expression profiling showed that the enzyme was active throughout the seed development, indicating a pivotal role in oil biosynthesis. The enzyme could utilize both saturated and unsaturated lysophosphatidylcholine substrates at the same rate, to synthesize phosphatidylcholine (PC). The enzyme also exhibited lysophosphatidic acid acyltransferase (LPAAT) activity, by preferring lysophosphatidic acid substrate. Substrate specificity studies showed that the enzyme preferred both monounsaturated and polyunsaturated fatty acyl CoAs over saturated CoAs. This activity may play a key role in enriching the PC fraction with polyunsaturated fatty acids (PUFAs). PUFAs present on PC can be transferred to oil through the action of other acyltransferases. Our results describe a new LPCAT enzyme that can be used to biotechnologically alter oilseed crops to incorporate more PUFA in its seed oil.

Functional characterization of acyltransferases from Salvia hispanica that can selectively catalyze the formation of trilinolenin

Salvia hispanica (chia) is an important oilseed crop cultivated commercially in South America, Australia, and India. It is the richest terrestrial natural source of α-linolenic acid (ALA), an ω-3 polyunsaturated fatty acid with varied health benefits. In this study, we have measured the total lipid content, fatty acid composition in four phases of seed development and analyzed the major triacylglycerol (TAG) molecular species present in Indian chia seed oil. We found that the mature seeds produced 28% oil, 65% of ALA, and trilinolenin as the major TAG species. To make TAG rich in ALA, there should be specialized enzymes that can efficiently transfer ALA to TAG. To study this hypothesis, we performed a characterization of TAG synthesizing enzymes present in chia. We have identified two acyl CoA:diacylglycerol acyltransferases (ShDGAT1 and ShDGAT2) and one phospholipid:diacylglycerol acyltransferase (ShPDAT1) from the chia transcriptome data. Functional characterization of these enzymes was conducted by heterologous expression in a TAG deficient mutant of Saccharomyces cerevisiae. Substrate specificity studies showed that ShDGAT2-1 and ShPDAT1 exhibited a strong preference towards substrates containing ALA and could incorporate 45% and 80% ALA into TAG, respectively. Both enzymes incorporated ALA in a concentration-dependent manner into TAG and were able to form trilinolenin in yeast. Our results provide a first insight into the high ALA accumulation in chia and the first demonstration of trilinolenin formation by DGAT2. The two identified enzymes (ShDGAT2-1 and ShPDAT1) can be used to metabolically engineer other oilseed crops to produce high levels of ALA.