Harnessing artificial intelligence for prostate cancer management

Prostate cancer (PCa) is a common malignancy in males. The pathology review of PCa is crucial for clinical decision-making, but traditional pathology review is labor intensive and subjective to some extent. Digital pathology and whole-slide imaging enable the application of artificial intelligence (AI) in pathology. This review highlights the success of AI in detecting and grading PCa, predicting patient outcomes, and identifying molecular subtypes. We propose that AI-based methods could collaborate with pathologists to reduce workload and assist clinicians in formulating treatment recommendations. We also introduce the general process and challenges in developing AI pathology models for PCa. Importantly, we summarize publicly available datasets and open-source codes to facilitate the utilization of existing data and the comparison of the performance of different models to improve future studies.

Predictive and prognostic biomarkers in urological tumours

Advancements in cutting-edge molecular profiling techniques, such as next-generation sequencing and bioinformatic analytic tools, have allowed researchers to examine tumour biology in detail and stratify patients based on factors linked with clinical outcome and response to therapy. This manuscript highlights the most relevant prognostic and predictive biomarkers in kidney, bladder, prostate and testicular cancers with recognised impact in clinical practice. In bladder and prostate cancer, new genetic acquisitions concerning the biology of tumours have modified the therapeutic scenario and led to the approval of target directed therapies, increasing the quality of patient care. Thus, it has become of paramount importance to choose adequate molecular tests, i.e., FGFR screening for urothelial cancer and BRCA1-2 alterations for prostate cancer, to guide the treatment plan for patients. While no tissue or blood-based biomarkers are currently used in routine clinical practice for renal cell carcinoma and testicular cancers, the field is quickly expanding. In kidney tumours, gene expression signatures might be the key to identify patients who will respond better to immunotherapy or anti-angiogenic drugs. In testicular germ cell tumours, the use of microRNA has outperformed conventional serum biomarkers in the diagnosis of primary tumours, prediction of chemoresistance, follow-up monitoring, and relapse prediction.

Natural Killer Cell Infiltration in Prostate Cancers Predict Improved Patient Outcomes

BACKGROUND

Natural killer (NK) cells are non-antigen specific innate immune cells that can be redirected to targets of interest using multiple strategies, although none are currently FDA-approved. We sought to evaluate NK cell infiltration into tumors to develop an improved understanding of which histologies may be most amenable to NK cell-based therapies currently in the developmental pipeline.

METHODS

DNA (targeted/whole-exome) and RNA (whole-transcriptome) sequencing was performed from tumors from 45 cancer types (N = 90,916 for all cancers and N = 3365 for prostate cancer) submitted to Caris Life Sciences. NK cell fractions and immune deconvolution were inferred from RNA-seq data using quanTIseq. Real-world overall survival (OS) and treatment status was determined and Kaplan-Meier estimates were calculated. Statistical significance was determined using X2 and Mann-Whitney U tests, with corrections for multiple comparisons where appropriate.

RESULTS

In both a pan-tumor and prostate cancer (PCa) -specific setting, we demonstrated that NK cells represent a substantial proportion of the total cellular infiltrate (median range 2-9% for all tumors). Higher NK cell infiltration was associated with improved OS in 28 of 45 cancer types, including (PCa). NK cell infiltration was negatively correlated with common driver mutations and androgen receptor variants (AR-V7) in primary prostate biopsies, while positively correlated with negative immune regulators. Higher levels of NK cell infiltration were associated with patterns consistent with a compensatory anti-inflammatory response.

CONCLUSIONS

Using the largest available dataset to date, we demonstrated that NK cells infiltrate a broad range of tumors, including both primary and metastatic PCa. NK cell infiltration is associated with improved PCa patient outcomes. This study demonstrates that NK cells are capable of trafficking to both primary and metastatic PCa and are a viable option for immunotherapy approaches moving forward. Future development of strategies to enhance tumor-infiltrating NK cell-mediated cytolytic activity and activation while limiting inhibitory pathways will be key.

Autocrine IGF-II-Associated Cancers: From a Rare Paraneoplastic Event to a Hallmark in Malignancy

The paraneoplastic syndrome referred in the literature as non-islet-cell tumor hypoglycemia (NICTH) and extra-pancreatic tumor hypoglycemia (EPTH) was first reported almost a century ago, and the role of cancer-secreted IGF-II in causing this blood glucose-lowering condition has been widely established. The landscape emerging in the last few decades, based on molecular and cellular findings, supports a broader role for IGF-II in cancer biology beyond its involvement in the paraneoplastic syndrome. In particular, a few key findings are constantly observed during tumorigenesis, (a) a relative and absolute increase in fetal insulin receptor isoform (IRA) content, with (b) an increase in IGF-II high-molecular weight cancer-variants (big-IGF-II), and (c) a stage-progressive increase in the IGF-II autocrine signal in the cancer cell, mostly during the transition from benign to malignant growth. An increasing and still under-exploited combinatorial pattern of the IGF-II signal in cancer is shaping up in the literature with respect to its transducing receptorial system and effector intracellular network. Interestingly, while surgical and clinical reports have traditionally restricted IGF-II secretion to a small number of solid malignancies displaying paraneoplastic hypoglycemia, a retrospective literature analysis, along with publicly available expression data from patient-derived cancer cell lines conveyed in the present perspective, clearly suggests that IGF-II expression in cancer is a much more common event, especially in overt malignancy. These findings strengthen the view that (1) IGF-II expression/secretion in solid tumor-derived cancer cell lines and tissues is a broader and more common event compared to the reported IGF-II association to paraneoplastic hypoglycemia, and (2) IGF-II associates to the commonly observed autocrine loops in cancer cells while IGF-I cancer-promoting effects may be linked to its paracrine effects in the tumor microenvironment. Based on these evidence-centered considerations, making the autocrine IGF-II loop a hallmark for malignant cancer growth, we here propose the functional name of IGF-II secreting tumors (IGF-IIsT) to overcome the view that IGF-II secretion and pro-tumorigenic actions affect only a clinical sub-group of rare tumors with associated hypoglycemic symptoms. The proposed scenario provides an updated logical frame towards biologically sound therapeutic strategies and personalized therapeutic interventions for currently unaccounted IGF-II-producing cancers.

Novel combination of imipridones and histone deacetylase inhibitors demonstrate cytotoxic effect through integrated stress response in pediatric solid tumors

There is a demonstrated need for new chemotherapy options in pediatric oncology, as pediatric solid tumors continue to plateau at 60% with event-free survival. Imipridones, a novel class of small molecules, represent a potential new therapeutic option, with promising pre-clinical data and emerging clinical trial data in adult malignancies. ONC201, ONC206, and ONC212 are imipridones showing pro-apoptotic anti-cancer response. Using cell viability assays, and protein immunoblotting, we were able to demonstrate single-agent efficacy of all 3 imipridones inducing cell death in pediatric solid tumor cell lines, including osteosarcoma, malignant peripheral nerve sheath tumors, Ewing sarcoma (EWS), and neuroblastoma. ONC201 displayed IC50 values for non-H3K27M-mutated EWS cell lines ranging from 0.86 µM (SK-N-MC) to 2.76 µM (RD-ES), which were comparable to the range of IC50 values for H3K27M-mutated DIPG cells lines (range 1.06 to 1.56 µM). ONC212 demonstrated the highest potency in single-agent cell killing, followed by ONC206, and ONC201. Additionally, pediatric solid tumor cells were treated with single-agent therapy with histone deacetylase inhibitors (HDACi) vorinostat, entinostat, and panobinostat, showing cell killing with all 3 HDACi drugs, with panobinostat showing the greatest potency. We demonstrate that dual-agent therapy with combinations of imipridones and HDACi lead to synergistic cell killing and apoptosis in all pediatric solid tumor cell lines tested, with ONC212 and panobinostat combinations demonstrating maximal potency. The imipridones induced the integrated stress response with ATF4 and TRAIL receptor upregulation, as well as reduced expression of ClpX. Hyperacetylation of H3K27 was associated with synergistic killing of tumor cells following exposure to imipridone plus HDAC inhibitor therapies. Our results introduce a novel class of small molecules to treat pediatric solid tumors in a precision medicine framework. Use of impridones in pediatric oncology is novel and shows promising pre-clinical efficacy in pediatric solid tumors, including in combination with HDAC inhibitors.

ONC201/TIC10 plus TLY012 anti-cancer effects via apoptosis inhibitor downregulation, stimulation of integrated stress response and death receptor DR5 in gastric adenocarcinoma

Gastric adenocarcinoma typically presents with advanced stage when inoperable. Chemotherapy options include non-targeted and toxic agents, leading to poor 5-year patient survival outcomes. Small molecule ONC201/TIC10 (TRAIL-Inducing Compound #10) induces cancer cell death via ClpP-dependent activation of the integrated stress response (ISR) and up-regulation of the TRAIL pathway. We previously found in breast cancer, pancreatic cancer and endometrial cancer that ONC201 primes tumor cells for TRAIL-mediated cell death through ISR-dependent upregulation of ATF4, CHOP and TRAIL death receptor DR5. We investigated the ability of ONC201 to induce apoptosis in gastric adenocarcinoma cells in combination with recombinant human TRAIL (rhTRAIL) or PEGylated trimeric TRAIL (TLY012). AGS (caspase 8-, KRAS-, PIK3CA-mutant, HER2-amplified), SNU-1 (KRAS-, MLH1-mutant, microsatellite unstable), SNU-5 (p53-mutant) and SNU-16 (p53-mutant) gastric adenocarcinoma cells were treated with ONC201 and TRAIL both in cell culture and in vivo. Gastric cancer cells showed synergy following dual therapy with ONC201 and rhTRAIL/TLY012 (combination indices < 0.6 at doses that were non-toxic towards normal fibroblasts). Synergy was observed with increased cells in the sub-G1 phase of the cell cycle with dual ONC201 plus TRAIL therapy. Increased PARP, caspase 8 and caspase 3 cleavage after ONC201 plus TRAIL further documented apoptosis. Increased cell surface expression of DR5 with ONC201 therapy was observed by flow cytometry, and immunoblotting revealed ONC201 upregulation of the ISR, ATF4, and CHOP. We observed downregulation of anti-apoptotic cIAP-1 and XIAP in all cells except AGS, and cFLIP in all cells except SNU-16. We tested the regimen in an organoid model of human gastric cancer, and in murine sub-cutaneous xenografts using AGS and SNU-1 cells. Our results suggest that ONC201 in combination with TRAIL may be an effective and non-toxic option for the treatment of gastric adenocarcinoma by inducing apoptosis via activation of the ISR, increased cell surface expression of DR5 and down-regulation of inhibitors of apoptosis. Our results demonstrate in vivo anti-tumor effects of ONC201 plus TLY012 against gastric cancer that could be further investigated in clinical trials.

Cancer cell seeding density as a mechanism of chemotherapy resistance: a novel cancer cell density index based on IC50-Seeding Density Slope (ISDS) to assess chemosensitivity

Although the 50% inhibitory concentration (IC50) is a commonly used measurement of chemosensitivity in cancer cells, it has been known to vary with the density of the treated cells (in that more densely seeded cells are more resistant to chemotherapeutic agents). Indeed, density-dependent chemoresistance may be a significant independent mechanism of therapy resistance. We examine the nature of cell density-dependent chemoresistance and explore possible underlying mechanisms. CellTiter-Glo assays and ethidium homodimer staining revealed that response to chemotherapy is density-dependent in all cancer cell lines tested. Our results prompted us to develop a novel cancer cell seeding density index of chemosensitivity, the ISDS (IC50-Seeding Density Slope), which we propose can serve as an improved method of analyzing how cancer cells respond to chemotherapeutic treatment compared to the widely-used IC50. Furthermore, western blot analysis suggests that levels of autophagy and apoptotic markers are modulated by cancer cell density. Cell viability experiments using the autophagy inhibitor chloroquine showed that chloroquine's efficacy was reduced at higher cell densities and that chloroquine and cisplatin exhibited synergy at both higher and lower cell densities in TOV-21G cells. We discuss alternative mechanisms of density-dependent chemoresistance and in vivo/clinical applications, including challenges of adjuvant chemotherapy and minimal residual disease. Taken together, our findings show that cell density is a significant contributor in shaping cancer chemosensitivity, that the ISDS (aka the Ujwal Punyamurtula/Wafik El-Deiry or Ujwal-WAF Index) can be used to effectively assess cell viability and that this phenomenon of density-dependent chemoresistance may be leveraged for a variety of biologic and cancer therapeutic applications.

Preclinical Synergistic Combination Therapy of Lurbinectedin with Irinotecan and 5-Fluorouracil in Pancreatic Cancer

Pancreatic cancer is a devastating disease with a poor prognosis. Novel chemotherapeutics in pancreatic cancer have shown limited success, illustrating the urgent need for new treatments. Lurbinectedin (PM01183; LY-01017) received FDA approval in 2020 for metastatic small cell lung cancer on or after platinum-based chemotherapy and is currently undergoing clinical trials in a variety of tumor types. Lurbinectedin stalls and degrades RNA Polymerase II and introduces breaks in DNA, causing subsequent apoptosis. We now demonstrate lurbinectedin's highly efficient killing of human-derived pancreatic tumor cell lines PANC-1, BxPC-3, and HPAF-II as a single agent. We further demonstrate that a combination of lurbinectedin and irinotecan, a topoisomerase I inhibitor with FDA approval for advanced pancreatic cancer, results in the synergistic killing of pancreatic tumor cells. Western blot analysis of combination therapy indicates an upregulation of γH2AX, a DNA damage marker, and the Chk1/ATR pathway, which is involved in replicative stress and DNA damage response. We further demonstrate that the triple combination between lurbinectedin, irinotecan, and 5-fluorouracil (5-FU) results in a highly efficient killing of tumor cells. Our results are developing insights regarding molecular mechanisms underlying the therapeutic efficacy of a novel combination drug treatment for pancreatic cancer.

The role of p53 in anti-tumor immunity and response to immunotherapy

p53 is a transcription factor that regulates the expression of genes involved in tumor suppression. p53 mutations mediate tumorigenesis and occur in approximately 50% of human cancers. p53 regulates hundreds of target genes that induce various cell fates including apoptosis, cell cycle arrest, and DNA damage repair. p53 also plays an important role in anti-tumor immunity by regulating TRAIL, DR5, TLRs, Fas, PKR, ULBP1/2, and CCL2; T-cell inhibitory ligand PD-L1; pro-inflammatory cytokines; immune cell activation state; and antigen presentation. Genetic alteration of p53 can contribute to immune evasion by influencing immune cell recruitment to the tumor, cytokine secretion in the TME, and inflammatory signaling pathways. In some contexts, p53 mutations increase neoantigen load which improves response to immune checkpoint inhibition. Therapeutic restoration of mutated p53 can restore anti-cancer immune cell infiltration and ameliorate pro-tumor signaling to induce tumor regression. Indeed, there is clinical evidence to suggest that restoring p53 can induce an anti-cancer immune response in immunologically cold tumors. Clinical trials investigating the combination of p53-restoring compounds or p53-based vaccines with immunotherapy have demonstrated anti-tumor immune activation and tumor regression with heterogeneity across cancer type. In this Review, we discuss the impact of wild-type and mutant p53 on the anti-tumor immune response, outline clinical progress as far as activating p53 to induce an immune response across a variety of cancer types, and highlight open questions limiting effective clinical translation.

Pan-integrin inhibitor GLPG-0187 promotes T-cell killing of mismatch repair-deficient colorectal cancer cells by suppression of SMAD/TGF-β signaling

Colorectal cancer is the third leading cause of cancer-related death and the third most common cause of cancer. As the five-year survival with advanced metastatic colorectal cancer (mCRC) is 14%, new treatment strategies are needed. Immune checkpoint blockade, which takes advantage of an individual's immune system to fight cancer, has an impact in the clinic; however, for CRC, it is only effective and approved for treating mismatch repair (MMR)-deficient cancer. Moreover, long-term outcomes in MMR-deficient mCRC suggest that most patients are not cured and eventually develop therapy resistance. We hypothesized that targeting TGF-β signaling may enhance immune-mediated T-cell killing by MMR-deficient CRC cells. Using GLPG-0187, an inhibitor of multiple integrin receptors and TGF-β, we demonstrate minimal cytotoxicity against MMR-deficient HCT116 or p53null HCT116 human CRC cells. GLPG-0187 promoted significant immune cell killing of the CRC cells by TALL-104 T lymphoblast cells and reduced phosphoSMAD2 in HCT116 p53-null cells either in the absence or presence of exogenous TGF-β. We observed a reduction in CCL20, CXCL5, prolactin, and TRAIL-R3, while GDF-15 was increased in TALL-104 cells treated with a T-cell activating dose of GLPG-0187 (4 µM). Our results suggest that TGF-β signaling inhibition by a general integrin receptor inhibitor may boost T-cell killing of MMR-deficient colorectal cancer cells and suggest that a combination of anti-GDF-15 in combination with TGF-β blockade be further investigated in the treatment of MMR-deficient mCRC. Our results support the development of a novel immune-based therapeutic strategy to treat colorectal cancer by targeting the TGF-β signaling pathway through integrin receptor blockade.

Broad spectrum integrin inhibitor GLPG-0187 bypasses immune evasion in colorectal cancer by TGF-β signaling mediated downregulation of PD-L1

Integrin receptors have long posed as a potentially attractive target for disrupting cancer hallmarks. Promising preliminary findings with integrin inhibition as an adjuvant to chemotherapy have not translated to clinical success. However, the effect of integrin inhibition on tumor-immune cell interactions remains largely unexplored. Further investigation could shed light on a connection between integrin signaling and immune checkpoint expression, opening the path for using integrin inhibitors to sensitize otherwise resistant tumors to immunotherapy. Fluorescently labeled wild-type HCT-116 colorectal cancer cells and TALL-104 T-cells were co-cultured and treated with GLPG-0187, a small molecule integrin inhibitor, at various doses. This assay revealed dose dependent cancer cell killing, indicating that integrin inhibition may be sensitizing cancer cells to immune cells. The hypothesized mechanism involves TGF-β-mediated PD-L1 upregulation in cancer cells. To investigate this mechanism, both WT and p53-/- HCT-116 cells were pre-treated with GLPG-0187 and subsequently with latent-TGF-β. Western blot analysis demonstrated that the addition of latent-TGF-β increased the expression of PD-L1 in cancer cells. Additionally, a low dose of integrin inhibitor rescued these effects, returning PD-L1 expression back to control levels. This indicates that the immunostimulatory effects of integrin inhibition may be due to downregulation of immune checkpoint PD-L1 on cancer cells. It must be noted that the higher dose of the drug did not reduce PD-L1 expression. This could potentially be due to off-target effects conflicting with the proposed pathway; however, these findings are still under active investigation. Ongoing proteomic experiments will include a larger range of both drug and latent-TGF-β doses. Probing for additional downstream markers of TGF-β and up-stream markers of PD-L1 will help to further elucidate this mechanism. Further co-culture experiments will also include anti-PD-L1 and anti-PD-1 therapy to investigate the viability of integrin inhibition as an adjuvant to immune checkpoint blockade.

PBRM1 mutations might render a subtype of biliary tract cancers sensitive to drugs targeting the DNA damage repair system

Polybromo-1 (PBRM1) loss of function mutations are present in a fraction of biliary tract cancers (BTCs). PBRM1, a subunit of the PBAF chromatin-remodeling complex, is involved in DNA damage repair. Herein, we aimed to decipher the molecular landscape of PBRM1 mutated (mut) BTCs and to define potential translational aspects. Totally, 1848 BTC samples were analyzed using next-generation DNA-sequencing and immunohistochemistry (Caris Life Sciences, Phoenix, AZ). siRNA-mediated knockdown of PBRM1 was performed in the BTC cell line EGI1 to assess the therapeutic vulnerabilities of ATR and PARP inhibitors in vitro. PBRM1 mutations were identified in 8.1% (n = 150) of BTCs and were more prevalent in intrahepatic BTCs (9.9%) compared to gallbladder cancers (6.0%) or extrahepatic BTCs (4.5%). Higher rates of co-mutations in chromatin-remodeling genes (e.g., ARID1A 31% vs. 16%) and DNA damage repair genes (e.g., ATRX 4.4% vs. 0.3%) were detected in PBRM1-mutated (mut) vs. PBRM1-wildtype (wt) BTCs. No difference in real-world overall survival was observed between PBRM1-mut and PBRM1-wt patients (HR 1.043, 95% CI 0.821-1.325, p = 0.731). In vitro, experiments suggested that PARP ± ATR inhibitors induce synthetic lethality in the PBRM1 knockdown BTC model. Our findings served as the scientific rationale for PARP inhibition in a heavily pretreated PBRM1-mut BTC patient, which induced disease control. This study represents the largest and most extensive molecular profiling study of PBRM1-mut BTCs, which in vitro sensitizes to DNA damage repair inhibiting compounds. Our findings might serve as a rationale for future testing of PARP/ATR inhibitors in PBRM1-mut BTCs.

GSK-3 Inhibitor Elraglusib Enhances Tumor-Infiltrating Immune Cell Activation in Tumor Biopsies and Synergizes with Anti-PD-L1 in a Murine Model of Colorectal Cancer

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that has been implicated in numerous oncogenic processes. GSK-3 inhibitor elraglusib (9-ING-41) has shown promising preclinical and clinical antitumor activity across multiple tumor types. Despite promising early-phase clinical trial results, there have been limited efforts to characterize the potential immunomodulatory properties of elraglusib. We report that elraglusib promotes immune cell-mediated tumor cell killing of microsatellite stable colorectal cancer (CRC) cells. Mechanistically, elraglusib sensitized CRC cells to immune-mediated cytotoxicity and enhanced immune cell effector function. Using western blots, we found that elraglusib decreased CRC cell expression of NF-κB p65 and several survival proteins. Using microarrays, we discovered that elraglusib upregulated the expression of proapoptotic and antiproliferative genes and downregulated the expression of cell proliferation, cell cycle progression, metastasis, TGFβ signaling, and anti-apoptotic genes in CRC cells. Elraglusib reduced CRC cell production of immunosuppressive molecules such as VEGF, GDF-15, and sPD-L1. Elraglusib increased immune cell IFN-γ secretion, which upregulated CRC cell gasdermin B expression to potentially enhance pyroptosis. Elraglusib enhanced immune effector function resulting in augmented granzyme B, IFN-γ, TNF-α, and TRAIL production. Using a syngeneic, immunocompetent murine model of microsatellite stable CRC, we evaluated elraglusib as a single agent or combined with immune checkpoint blockade (anti-PD-1/L1) and observed improved survival in the elraglusib and anti-PD-L1 group. Murine responders had increased tumor-infiltrating T cells, augmented granzyme B expression, and fewer regulatory T cells. Murine responders had reduced immunosuppressive (VEGF, VEGFR2) and elevated immunostimulatory (GM-CSF, IL-12p70) cytokine plasma concentrations. To determine the clinical significance, we then utilized elraglusib-treated patient plasma samples and found that reduced VEGF and BAFF and elevated IL-1 beta, CCL22, and CCL4 concentrations correlated with improved survival. Using paired tumor biopsies, we found that tumor-infiltrating immune cells had a reduced expression of inhibitory immune checkpoints (VISTA, PD-1, PD-L2) and an elevated expression of T-cell activation markers (CTLA-4, OX40L) after elraglusib treatment. These results address a significant gap in knowledge concerning the immunomodulatory mechanisms of GSK-3 inhibitor elraglusib, provide a rationale for the clinical evaluation of elraglusib in combination with immune checkpoint blockade, and are expected to have an impact on additional tumor types, besides CRC.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Abstract 5840: Normal fibroblasts, cancer-associated fibroblasts, and their senescent counterparts exert varying effects on tumorigenic potential and ABT-263 sensitivity of gastric cancer cells

It has become increasingly apparent that cancer is not a tumor cell-centric disease. Elements of the tumor microenvironment (TME), including fibroblasts and senescent cells, have been shown to contribute to tumor cell proliferation, metastasis, and therapy resistance, and are therefore major contributors to disease progression. However, this has been complicated by accumulating evidence suggesting that the function of fibroblasts is heterogeneous, with normal fibroblasts (NFs) and cancer-associated fibroblasts (CAFs) both promoting or suppressing tumorigenesis and drug sensitivity within different contexts. Moreover, although senescent fibroblasts have been shown to accelerate tumor growth and contribute to therapy resistance, whether phenotypic differences exist between different senescent fibroblasts remains poorly understood. It is clear that additional work must be done to unravel the precise mechanisms by which NFs, CAFs, and their senescent counterparts interact within the tumor microenvironment to modulate tumor cell growth and sensitivity to therapy. Here, we show different NF and CAF lines exert varying effects on AGS gastric cancer cells. We found that when AGS cells are co-cultured with IMR90 lung fibroblasts, they form fewer and smaller colonies (total colony area = 5.14E3 pixels^2) than when cultured alone (total colony area = 2.57E4 pixels^2). On the other hand, colony formation ability is enhanced when AGS cells are co-cultured with GF1 primary gastric fibroblasts (total colony area = 3.56E4 pixels^2), and to a greater extent when cultured with CK4520 (total colony area = 4.59E4 pixels^2) and CK8612 (total colony area = 4.88E4 pixels^2) primary gastric CAFs. We next sought to determine whether these cells modulate AGS sensitivity to ABT-263, a BH3 mimetic that activates the intrinsic apoptotic pathway by targeting and inhibiting Bcl-2 and Bcl-xl. We treated AGS cells with ABT-263 with or without the addition of fibroblast-conditioned medium. We showed that IMR90 cells sensitize AGS cells to ABT-263, with an IC50 shift from 109 nM to 54 nM in AGS cells treated with IMR90-conditioned medium. On the other hand, AGS cells were more resistant to ABT-263 when treated with GF1, CK4520, or CK8612-conditioned medium, with IC50s of 270 nM, 520 nM, and 540 nM, respectively. Ongoing efforts involve expanding these experiments to senescent fibroblasts and conducting cytokine profiles to begin investigating the mechanisms underlying these phenotypes. These results contribute to our understanding of tumorigenesis and drug resistance.

Citation Format: Francesca R. Di Cristofano, Shengliang Zhang, Kelsey E. Huntington, Wafik S. El-Deiry. Normal fibroblasts, cancer-associated fibroblasts, and their senescent counterparts exert varying effects on tumorigenic potential and ABT-263 sensitivity of gastric cancer cells. [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 5840.

Abstract 3254: Combination of palbociclib, a potent CDK4/6 inhibitor, with anti-PD1 drug pembrolizumab treatment to promote T-cell mediated glioblastoma tumor cell death under hypoxia

Glioblastoma (GBM) is the most common malignant brain and other central nervous system (CNS) tumor, which comprises 47.7% of all cases. The standard treatment options are surgery, radiation therapy, and chemotherapy using temozolomide. GBM is fast-growing, aggressive, and results in poor overall survival, approximately 40% in the first year and 17% in the second year. Hypoxia, the lack of sufficient oxygen in tissues, is the hallmark of GBM and can induce drug resistance and inhibit anti-tumor immune responses. Previous studies show that CDK inhibitors can destabilize HIF1, a key regulator of hypoxia induced apoptosis and p53 stabilization. Palbociclib, a potent oral inhibitor of CD4/6, is undergoing clinical trials for GBM treatment. However, it was not an effective treatment for recurrent GBM when used as alone in a Phase II study. Thus, we are exploring the cytotoxicity of palbociclib in combination with an anti-PD1 drug pembrolizumab, which is proven to be highly effective in other cancer types. Preliminary studies use CellTitlerGLO viability assay to determine the IC50s for Palbociclib at 24, 48, and 72 hours in both normoxia and hypoxia conditions. Immune cell co-culture, comprising of GBM cell lines plus TALL104 human leukemia T cells, was used to determine the amount of tumor cell death with palbociclib, pembrolizumab and a combination at different time points in both normoxia and hypoxia conditions. Our results are providing insights into improving immune checkpoint therapy for GBM patients.

Citation Format: Yutong Xia, Lanlan Zhou, Shuai Zhao, Wafik S. El-Deiry. Combination of palbociclib, a potent CDK4/6 inhibitor, with anti-PD1 drug pembrolizumab treatment to promote T-cell mediated glioblastoma tumor cell death under hypoxia [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 3254.

Abstract 3251: The immunostimulatory effect of 9-ING-41, a small molecule GSK-3 inhibitor, in sarcomas

Due to the rarity and genomic disparity of soft tissue and bone sarcomas, actionable therapeutic targets have been elusive. However, inhibition of GSK-3β has emerged as a potentially promising therapy that could be of great benefit to pediatric and adult sarcoma patients. Saos-2 osteosarcoma and 93T449 liposarcoma cell lines were pretreated at IC5072 with small molecule GSK-3β inhibitor 9-ING-41 (elraglusib). The cells were harvested for western blot analysis after 48 hours of treatment. Additionally, both cancer cell lines as well as TALL-104 T-cells and NK-92 NK cells were treated with 0.5 μM 9-ING-41 for 24 hours and harvested for Luminex cytokine profiling. The western blots demonstrated an increase in cPARP, an apoptotic marker, in both cancer cell lines after 9-ING-41 treatment. Additionally, an increase in PD-L1 expression was observed. The cytokine analysis revealed stimulation of immune cell activity in response to 9-ING-41. Treated T-cells had an increase in CXCL11, which is associated with T-cell recruitment, as well as an increased level of IL-18, which is shown to induce increased IFN-γ in Th1 cells. Additionally, NK-92 cells demonstrated an increase in IL-8 chemokine and an increase in soluble TRAIL (TRAIL/TNFSF10). The cancer cell lines showed a homogenous increase in growth factor TGF-ɑ, however, only the Saos-2 osteosarcoma cell line demonstrated an increase of IL-6. We are further validating the data with follow-up cytokine profiling. The increase in immunostimulatory cytokines as well as the increased expression of PD-L1 suggest a rationale for combining 9-ING-41 with immune checkpoint blockade therapy. The potential synergistic effect of these two therapies is currently under investigation with co-culture experiments of sarcoma and immune cells. The treatment cohorts for these experiments include 9-ING-41 combined with either anti-PD-L1, anti-PD-1, or anti-CTLA-4 immune checkpoint inhibitors. Our results suggest a promising combination therapeutic strategy for patients with soft tissue and bone sarcomas and future work will strive to better elucidate the mechanisms of efficacy.

Citation Format: William J. MacDonald, Samuel Lew, Kelsey E. Huntington, Rishi R. Lulla, Bradley D. DeNardo, Wafik S. El-Deiry. The immunostimulatory effect of 9-ING-41, a small molecule GSK-3 inhibitor, in sarcomas [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 3251.

Abstract 4959: TIC10/ONC201 activates ClpP to degrade ALAS1 while PG3 does not degrade ALAS1 in pathway to HRI, ATF4 and CHOP activation leading to tumor cell death

TRAIL-inducing compound TIC10/ONC201 binds and activates mitochondrial protease ClpP leading to integrated stress response (ISR) and ATF4 transcription factor activation. Our lab previously reported that ONC201 activates HRI (heme-regulated inhibitor) kinase but does not signal eIF2-alpha phosphorylation through PERK or GCN2. However, the connection between ClpP activation of HRI remains unknown. PG3, a prodigiosin analog that bypasses a defective p53 pathway potently induces ATF4 and pro-apoptotic PUMA. Our data indicate that PG3 activates ATF4 through ISR via HRI as knockdown of HRI but not PKR blocked upregulation of ATF4 and CHOP in several tumor cell lines. We have been exploring how ClpP activation leads to HRI and ISR activation, and the mechanism by which PG3 leads to HRI activation. We find that activation of HRI by PG3 or ONC201 is not through the OMA1/DELE1◊HRI activation pathway. Moreover, ROS and NO are not responsible for ONC201- or PG3-induced HRI activation. ALAS1 (5'-aminolevulinate synthase 1) catalyzes the first rate-limiting step in heme (Iron-protoporphyrin) biosynthesis. ONC201 treatment leads to potent downregulation and inhibition of ALAS1, indicating that ONC201 inhibits heme biosynthesis. It is well known that reduced heme results in activation of the HRI kinase. We show that an inhibitor of heme biosynthesis or knockdown of ALAS1 results in HRI activation, while knockdown of HRI blocks upregulation of ATF4 by ONC201. Knockdown of ClpP rescues ONC201-induced downregulation of ALAS1 which blocks ONC201-induced upregulation of CHOP. Our studies identify a novel link between ClpP activation induced by ONC201 treatment and ATF4 upregulation, via the ClpP/ALAS1◊HRI◊ATF4/CHOP pathway. However, PG3 does not inhibit ALAS1, reduce its expression or therefore signal through ClpP. PG3 treatment did not lead to degradation of ALAS1, indicating that PG3 does not activate ClpP as ALAS1 is a known ClpP direct substrate. We are further investigating the signaling pathway that leads to PG3-induced activation of HRI. Our results suggest that different small molecule inducers of the ISR such as ONC201 and PG3 can achieve an anti-tumor effect through different pathways involving kinase HRI ultimately leading to ATF4/CHOP activation and tumor cell death.

Citation Format: Xiaobing Tian, Wafik S. El-Deiry. TIC10/ONC201 activates ClpP to degrade ALAS1 while PG3 does not degrade ALAS1 in pathway to HRI, ATF4 and CHOP activation leading to tumor cell death. [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 4959.

Abstract 4909: Molecular analysis of small cell lung cancer provides insights into mechanism of action underlying the novel drug combination of lurbinectedin and TIC10/ONC201

We previously explored the combination of novel imipridone TIC10/ONC201 and small molecule RNA polymerase inhibitor lurbinectedin as a potentially effective treatment regimen for small cell lung cancer (SCLC). Data from cell viability experiments demonstrated synergistic killing of SCLC cells with minimal death of healthy control cells. Analysis of intracellular proteins via Western blot indicated that combinatorial treatment induces the integrated stress response, DNA damage/cell cycle checkpoint responses, and increased apoptosis of tumor cells. We have utilized the Luminex 200 platform to perform analyses of cytokine levels in SCLC cell lines with various genetic alterations before and after ONC201 and lurbinectedin treatment. Our results revealed significant changes in cytokine levels following treatment indicating potential immunomodulatory and angioregulatory effects of ONC201 and lurbinectedin. CCL3, known to recruit and activate granulocytes, was found to be elevated by treatment with lurbinectedin, ONC201 and combination versus control. Angiopoietin 1, which contributes to blood vessel maturation, and angiopoietin 2, which promotes neovascularisation, were elevated by all drug treatments in H1882 SCLC cells. Our ongoing studies are further analysing the importance of specific cytokines in tumor vascularity and in recruitment and killing of SCLC cells by immune cells. Results from these experiments are helping to elucidate the molecular mechanisms underlying SCLC, its immune landscape, and treatment response.

Citation Format: Ashley Sanchez Sevilla Uruchurtu, Nicholas Liguori, Leiqing Zhang, Kelsey Huntington, Lanlan Zhou, Young Lee, Abbas E. Abbas, Christopher G. Azzoli, Wafik S. El-Deiry. Molecular analysis of small cell lung cancer provides insights into mechanism of action underlying the novel drug combination of lurbinectedin and TIC10/ONC201. [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 4909.

Abstract 2674: Synergistic combinations of lurbinectedin with irinotecan and ONC212 in pancreatic cancer

Pancreatic cancer is a devastating disease with a five-year survival rate below 10% according to the American Cancer Society. Novel chemotherapeutics and targeted therapies in pancreatic cancer have shown limited success, illustrating the urgent need for new treatments. Lurbinectedin is a chemotherapeutic synthetic tetrahydroisoquinoline alkaloid that inhibits active transcription by binding to guanine rich sequences in the minor groove of DNA. Lurbinectedin has been shown to reduce oncogenic transcription by stalling and degrading RNA Polymerase II while also inducing single- and double-stranded breaks to DNA, causing subsequent apoptosis. Lurbinectedin received accelerated FDA approval in 2020 for metastatic small cell lung cancer on or after platinum-based chemotherapy and is currently undergoing clinical trials in a variety of tumor types. We recently described a synergistic interaction between lurbinectedin and ONC201/TIC10, a compound that induces the TRAIL pathway, in killing SCLC cell lines associated with activation of p-Chk1 and the integrated stress response. We now demonstrate lurbinectedin’s efficient killing of pancreatic tumor cells as a single agent in PANC-1, BxPC-3, and HPAF-II cell lines, with IC-50s corresponding to sub-nanomolar concentrations. We also demonstrate that a combination of lurbinectedin and irinotecan, a topoisomerase I inhibitor with FDA approval for advanced pancreatic cancer, results in synergistic killing of pancreatic tumor cells in vitro. We further demonstrate a combination of lurbinectedin and ONC212, an imipridone, the same class of compounds as ONC201, also results in synergistic killing of pancreatic tumor cells. Cell viability was measured using the CellTiterGlo assay at varying drug concentrations. We hypothesize a combination therapy of lurbinectedin and irinotecan or ONC212 can enhance immune cell killing of pancreatic tumor cells. This is being explored by co-culturing CD8+ T lymphoblast cells with pancreatic tumor cells treated with lurbinectedin, irinotecan, ONC212, and combination, along with molecular mechanisms of cell death and effects on cytokines in the tumor microenvironment. Our results are developing insights regarding molecular mechanisms underlying therapeutic efficacy of a novel combination drug treatment for pancreatic cancer.

Citation Format: Tej Tummala, Arielle De La Cruz, Ash Uruchurtu, Nicholas R. Liguori, Abbas E. Abbas, Leiqing Zhang, Christopher G. Azzoli, Lanlan Zhou, Wafik S. El-Deiry. Synergistic combinations of lurbinectedin with irinotecan and ONC212 in pancreatic 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 2674.

Abstract 4457: Post exposure suppression of radiation pneumonitis by TRAIL pathway agonists TLY012 and ONC201

Thoracic therapeutic ionizing radiation is limited by toxicities such as pneumonitis and fibrosis of the lungs. Such limitation restricts therapeutic doses and adversely affects patient quality of life while undergoing and following treatment. ONC201/TIC10 is a small-molecule anti-cancer drug that activates the integrated stress response (ISR) and drives the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) pathway. Pegylated recombinant long-acting TRAIL (TLY012) has been shown in preclinical models to induce the reversal of fibrosis and currently has orphan drug status for systemic sclerosis and chronic pancreatitis. We show a similar effect of both TLY012 and ONC201 in vivo in protecting from radiation pneumonitis and fibrosis of the lungs. WT and TRAIL-/- C57Bl/6 mice receiving a single 20 Gy thoracic radiation dose with shielding of other organs and treated with 10 mg/kg of TLY012 twice a week showed a significantly reduced alveolar wall thickness and lessened inflammation compared to controls and DR5-/- mice receiving the same treatment upon histological analysis of the lungs conducted 13 days post-irradiation. WT and TRAIL-/- C57Bl/6 mice treated with 100 mg/kg of ONC201 once a week showed similar effect to a lesser extent. Further analysis in C57Bl/6 WT mice bearing orthotopic mammary fat pad e0771 TNBC tumors similarly receiving a single 20 Gy thoracic radiation dose revealed the same pattern of protection from radiation pneumonitis upon TRAIL-pathway agonism through treatment with TLY012 and ONC201 both in combination and alone, while also showing a significant reduction in tumor burden at the experimental endpoint (day 9 post-irradiation) in the combination treated mice. Further, pulse oximetry readings of the hind paw revealed a notable reduction in oxygen saturation in all mice except those treated with TLY012. Cytokinomic profiling of mouse serum upon sacrifice revealed a significant reduction in CCL22/MDC levels in the TLY012 cohort. Additional post-hoc analysis including immunophenotyping, immunostaining, and bulk RNA analysis through Nanostring nCounter technologies is underway. Altogether, these findings suggest a role for TLY012, ONC201, or broader modulation of the TRAIL/DR5 pathway in mitigating adverse effects and outcomes of therapeutic radiation, and may serve as a foundation for safer use of radiation in the clinic.

Citation Format: Jillian R. Strandberg, Anna Louie, Marina Hahn, Praveen Srinivasan, Andrew George, Arielle De La Cruz, Leiqing Zhang, Liz Hernandez Borrero, Kelsey Huntington, Christopher Azzoli, Abbas E. Abbas, Lanlan Zhou, Seulki Lee, Wafik S. El-Deiry. Post exposure suppression of radiation pneumonitis by TRAIL pathway agonists TLY012 and ONC201. [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 4457.

Abstract 4786: Imipridones induce lipid peroxidation and oxidative stress in gastrointestinal malignancies

Colorectal and pancreatic cancer collectively comprise 20% of all cancer-related deaths in the United States. Despite therapeutic advancements, the current standard of care often results in significant toxicity. Therefore, there is an urgent need to develop more efficacious novel therapies. The imipridones, ONC201/TIC10, ONC206, and ONC212, are novel small-molecules that bind mitochondrial ClpP and induce activation of the integrated stress response (ISR), tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) signaling, and oxidative stress. Each has previously demonstrated antitumor effects in a variety of preclinical in vitro and in vivo cancer subtypes, including colorectal cancer, with limited toxicity. Reactive oxidation species (ROS) are natural biproducts of cellular oxidative metabolism and play important roles in the modulation of cell death pathways, differentiation, and immune response. Using varying doses of ONC201, ONC206, and ONC212, we observed increased lipid peroxidation in several colorectal and pancreatic cancer cell lines using the C-11 BODIPY assay which measures lipid-specific peroxides. Lipid peroxidation was reversed by the ferroptosis inhibitor liproxstatin-1, suggesting that in addition to inducing apoptosis, imipridones may be involved in ferroptosis induction. Future directions include mechanistic work, investigation of the effect of imipridone-induced lipid peroxidation on immune cell cytotoxicity, and understanding the relative importance of lipid peroxidation in the clinical efficacy of imipridones.

Citation Format: Arielle De La Cruz, Praveen R. Srinivasan, Andrew George, Varun V. Prabhu, Maximilian P. Pinho-Schwermann, Wafik S. El-Deiry. Imipridones induce lipid peroxidation and oxidative stress in gastrointestinal malignancies. [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 4786.

Abstract 6706: Co-culture of circulating tumor cells (CTCs)-derived 3D organoids and autologous cytotoxic CD8+ T cells: A new functional precision oncology platform

Greater than 10 million patients succumb to cancer each year. Cancer metastasis is responsible for more than 90% of all cancer-associated deaths due to treatment resistance and increased tumor burden. As a seed for metastases, circulating tumor cells (CTCs) present a new dimension and horizon for clinical doctors in diagnosis, prognosis prediction, treatment monitoring, disease mechanism, and drug development. CTCs could gradually replace tissue biopsies which are painful and may be difficult to obtain depending on tumor location. CTC isolation is feasible after minimally invasive liquid biopsy and provides the basis for a multitude of ex vivo and in vivo studies including establishment of CTCs-derived 2D and 3D cultures. Organoids are miniscule models of tissues that grow in a 3D semisolid extracellular matrix medium with specific growth factors supplied. CTCs-derived 3D organoids play a vital role in precision oncology because they can preserve tumor heterogeneity, imitate the tumor microenvironment (TME), mimic cancer hypoxia in the TME, and maintain cancer and metastasis phenotypes. Cytotoxic CD8+ T cells are the most powerful effectors in the anticancer immune response. We hypothesized that co-culture of CTCs-derived 3D organoids and autologous cytotoxic CD8+ T cells could maximize patient-relevance of laboratory assessment of cancer-treatment immune-system interactions to facilitate precision oncology practice. TellBio’s novel TellDx CTC technology allows for isolation of viable and intact CTCs in liquid biopsies, regardless of cancer type. Unlabeled CTCs were cultured in growth factor reduced Matrigel with organoid culture WENRAS medium. Magnetic beads labeled white blood cells (WBCs) were cultured with T cell culture medium - WBCs and magnetic beads usually separate in three days - cytotoxic CD8+ T cells were isolated with the EasySep™ Human CD8+ T Cell Isolation Kit. CTCs-derived 3D organoids and autologous cytotoxic CD8+ T cells were co-cultured with or without different drug treatments - cytotoxicity was measured with CellTiterGlo® 3D Cell Viability Assay and imaging, and further mechanistic studies were feasible. Our co-culture platform enables us to utilize a patient's peripheral blood or pleural effusions to create a patient-specific, in vivo-like TME and immune microenvironment to model and assess ex vivo responses to investigational and FDA-cleared cancer therapies, and potentially provide oncologists with insights to improve clinical outcomes.

Citation Format: Lanlan Zhou, Leiqing Zhang, Lindsey Carlsen, Kelsey E. Huntington, Vida Tajiknia, Andrew George, Arielle De La Cruz, Arunasalam Navaraj, Praveen Srinivasan, Maximilian Schwermann, Benedito A. Carneiro, Wafik S. El-Deiry. Co-culture of circulating tumor cells (CTCs)-derived 3D organoids and autologous cytotoxic CD8+ T cells: A new functional precision oncology platform [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 6706.

Abstract 5636: Multiplex digital spatial profiling (DSP) of proteins in the tumor microenvironment in response to GSK-3 inhibition by 9-ING-41 (elraglusib) correlates with novel immunostimulatory effects observed in vivo

Glycogen synthase kinase 3 (GSK-3) is a serine/threonine kinase with key roles in myriad biological processes such as tumor progression, and inhibition of GSK-3 using the small molecule elraglusib has shown promising preclinical antitumor activity in multiple tumor types. Our preclinical experiments showed that elraglusib treatment increased tumor cell PD-L1 expression, downregulated angiogenic and immunosuppressive signaling pathways, and increased anti-tumor immune responses in vitro and in vivo. Subsequent studies showed that several circulating factors were predictive of response to PD-1/PD-L1 blockade and GSK-3 inhibition in a murine model of colorectal cancer. To determine the translational relevance of our prior results we evaluated tumor biopsies and plasma samples from patients with refractory solid tumors of multiple tissue origins enrolled in a Phase 1 clinical trial investigating elraglusib (NCT03678883). Plasma samples were collected from patients at baseline and 24 hours post-IV administration of elraglusib and were analyzed using Luminex technology. Paired FFPE tumor biopsies from patients with colorectal or pancreatic cancer before and after treatment were selected to analyze the tumor microenvironment using NanoString GeoMx DSP technology. The region of interest (ROI) selection strategy focused on mixed tumor and immune cell segments and ROIs were segmented using panCK+ and CD45+ morphology stains. Cytokine analysis revealed that elevated baseline plasma levels of IL-1 beta and reduced levels of VEGF correlated with improved progression-free survival (PFS) and overall survival (OS). PFS was also found to be positively correlated with elevated plasma levels of immunostimulatory analytes such as Granzyme B, IFN-gamma, and IL-2 at 24 hours post-treatment with elraglusib. CD45+ tumor-infiltrating immune cells had lower expression of VISTA, PD-1, and IDO-1 inhibitory checkpoint proteins and higher expression of OX40L and B7-H3 stimulatory checkpoint proteins in post-treatment biopsies as compared to pre-treatment biopsies. Moreover, time-on-study length negatively correlated with CD39 expression in PanCK+ segments and positively correlated with CD163 expression in CD45+ segments. This ongoing study, to our knowledge, represents the first digital spatial analysis of tumor biopsies from patients treated with elraglusib. These novel circulating biomarkers of response to GSK-3 inhibition could provide significant clinical utility and the spatial proteomics data may give us insights into the immunomodulatory mechanisms of GSK-3 inhibition.

Citation Format: Kelsey E. Huntington, Christoph Schorl, Shaolei Lu, Daniel Newhouse, Benedito A. Carneiro, Wafik S. El-Deiry. Multiplex digital spatial profiling (DSP) of proteins in the tumor microenvironment in response to GSK-3 inhibition by 9-ING-41 (elraglusib) correlates with novel immunostimulatory effects observed in vivo. [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 5636.

Abstract 3952: Preclinical anti-tumor effects of MDM4/MDMX inhibitor XI-006 in breast cancer and prostate cancer cell lines mediated through reduced tumor cell migration

MDM2 and MDM4/MDMX have emerged as potential mediators of tumor progression, organ-specific metastasis, and hyper-progression after immune checkpoint blockade therapy. While there are currently a number of MDM2 inhibitors in clinical trials, we found no pure MDM4/MDMX inhibitors under clinical investigation. Because hormone-resistant cancers pose a significant challenge for clinical intervention, the identification of translatable novel therapeutic targets remains an important goal. Analysis of triple-negative breast cancer (TNBC) and castration-resistant prostate cancer (CRPC) reveals overexpression of p53 negative regulator MDM4/MDMX as a frequent alteration in these cancers. There is an urgent need to study and target MDM4/MDMX in cancer therapy and this may ultimately include dual MDM2 and MDM4/MDMX inhibitors. However, it is clear that MDM4/MDMX is a primary oncogenic driver that requires specific therapeutic targeting. As metastasis is often observed clinically in patients diagnosed with breast and prostate cancer, we sought to expand our understanding of the metastasis reduction potential of a previously described preclinical MDM4/MDMX inhibitor, a 4-nitrobenzofuroxan derivative, XI-006 (NSC207895). In a scratch assay using breast and prostate cancer cell lines, increasing doses of XI-006 decreased tumor cell migration in a time and dose-dependent manner, demonstrating the benefit of MDMX inhibition in preventing the induction of tumor cell migration. The exact mechanism of this result remains unclear, and further investigation is needed to elucidate the impact of XI-006 on TNBC and CRPC cell proliferation and migration. Our future directions include identifying the synergistic potential of combining MDM4/MDMX inhibitor XI-006 with other cancer therapies, assessing the impact of XI-006 on immune responses in co-culture studies, and testing therapeutic efficacy in vivo.

Citation Format: Arielle De La Cruz, Andrew George, Payton De La Cruz, Maximilian P. Pinho-Schwermann, Kimberly S. Meza, Taylor Arnoff, Ilyas Sahin, Stephanie L. Graff, Benedito A. Carneiro, Wafik S. El-Deiry. Preclinical anti-tumor effects of MDM4/MDMX inhibitor XI-006 in breast cancer and prostate cancer cell lines mediated through reduced tumor cell migration. [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 3952.

Targeting Mutated p53: Naivete and Enthusiasm to Attempt the Impossible

Tumor suppressor TP53 is an important gene in human cancer because it is mutated in the majority of tumors, leading to loss-of-function or gain-of-function phenotypes. Mutated TP53 acts like an oncogene, driving cancer progression and causing poor patient outcomes. The role of mutated p53 in cancer has been known for over three decades, yet there is no FDA-approved drug to address the problem. This brief historical perspective highlights some of the insightful advances as well as challenges in therapeutic targeting of p53, especially the mutated forms. The article focuses on a functional p53 pathway restoration approach to drug discovery that years ago was not mainstream, encouraged by anyone, taught in textbooks, or embraced by medicinal chemists. With some knowledge, a clinician scientist's interest, and motivation, the author pursued a unique line of investigation leading to insights for functional bypass of TP53 mutations in human cancer. Like mutated Ras proteins, mutant p53 is fundamentally important as a therapeutic target in cancer and probably deserves a "p53 initiative" like the NCI's "Ras initiative." There is a link between naivete and enthusiasm for pursuing difficult problems, but important solutions are discovered through hard work and persistence. Hopefully, some benefit comes to patients with cancer from such drug discovery and development efforts.

Abstract 4185: Inclusive basic and advanced translational laboratory research competencies for research in cancer biology and therapeutics

Our Laboratory was established in 1994 at Univ. of Pennsylvania. Lab members demonstrated initial competencies by performing cell culture, western blots, immunofluorescence, and flow cytometry showing induction of p53/p21(WAF1) in cells treated with chemotherapy. Years later, our Laboratory of Translational Oncology & Experimental Cancer Therapeutics moved to Penn State Univ., Fox Chase Cancer Center/Temple Univ. and then Brown Univ. By 2020, with desire for inclusiveness (everyone succeeds), scientific rigor/reproducibility mandated by NIH, and as a training and mentoring activity (lab scientists/trainees/students mentoring others at High School level and beyond), we established a process for onboarding and training new cancer researchers. By Fall of 2022, there were 17 current Brown University undergraduate students (10 receiving research credit and 7 not receiving credit), HS students, 7 graduate students (PhD, masters, MD/PhD), and 6 medical students working with collaborating faculty at our laboratory at Brown’s Legorreta Cancer Center. After completion of biosafety training, and required trainings such as by IACUC, new lab members complete basic competencies in cell culture, cell viability, and western blot analysis that include technical, presentation quality output, and quantitative/statistical rigor to satisfy current standards for journal publication. For cell culture this includes pathogen free conditions, authentication, attention to details of routine procedures, documentation of morphology, freezing, thawing, passaging, seeding density, and managing cell populations to not run out of cells. Cell viability assessment includes attention to culture conditions, synergy analysis, data robustness, and presentation, and for western blots attention to quality of blots, protein quantification, loading, labeling, antibody specificity and sensitivity controls, presentation at 2022 standards, conventions for splicing, and issues with reproducibility including biological replicates, and generalizability. Additional and advanced competencies include RT-PCR, long-term colony assays, 3-D cultures (spheroids, organoids), transfection (overexpression, knockdown, CRISPR), co-culture and triculture with immune cells and fibroblasts, cytokine profiling, in vivo studies, in vivo imaging, immunohistochemistry, flow cytometric analysis, single cell techniques, viral infection, circulating tumor cell isolation, blood immune and cytokine analysis, and work with transgenic organoids and inducible cancer predisposing alleles. Modeling the tumor microenvironment, relevance to human cancer and translational directions are emphasized. Shared online lab resources, protocols, practices, videos, and manuscripts are available for lab members. The framework herein may be of interest to others involved in similar training programs.

Citation Format: Wafik S. El-Deiry, Andrew George, Francesca Di Cristofano, Praveen Srinivasan, Lindsey Carlsen, Kelsey E. Huntington, Arielle De La Cruz, Leiqing Zhang, Marina Hahn, Shuai Zhao, Attila Seyhan, Bradley D. DeNardo, Aaron W. Maxwell, Dae Hee Kim, Alex Raufi, Hina Khan, Stephanie L. Graff, Don S. Dizon, Christopher Azzoli, Abbas E. Abbas, Roxanne Wood, Rishi R. Lulla, Howard P. Safran, Benedito A. Carneiro, Arunasalam Navaraj, Xiaobing Tian, Shengliang Zhang, Lanlan Zhou. Inclusive basic and advanced translational laboratory research competencies for research in cancer biology and therapeutics. [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 4185.

Abstract 4070: Engineering TRAIL-expressing immune cells to target GI malignancies

While adoptive cell therapies, such as chimeric antigen receptor (CAR) T cells, have had promising results in hematologic malignancies, their translation to solid tumors has been mostly unsuccessful. A significant limitation to use of adoptive cell therapy in solid tumors has been life-threatening off-target toxicities, including acute respiratory toxicity and cytokine release syndrome. The native T cell program releases a diverse range of toxic proteins upon activation, including interferons, interleukins, perforins, and granzymes. Rather than activate the native T-cell program, selective expression of tumor-targeting agents may be advantageous. TNF-related apoptosis-inducing ligand (TRAIL) is known to selectively target tumor cells with minimal toxicity to normal tissues. We therefore engineered Jurkat (a human CD4+ T cell leukemia cell line) and THP-1 (a human monocytic leukemia cell line) cells to constitutively express wild-type TRAIL using a third-generation lentivirus system. These cells killed multiple cell lines across colorectal and pancreatic cancer, thus representing a possible therapeutic strategy to target GI malignancies. Furthermore, the addition of the ferroptosis induced erastin enhanced cytotoxicity of TRAIL-engineered cells, suggesting that targeting ferroptosis in addition to apoptosis is a promising strategy for enhancing immune killing. Future work will focus on overcoming TRAIL resistance, tumor trafficking, and alteration of the tumor microenvironment.

Citation Format: Praveen R. Srinivasan, Shengliang Zhang, Wafik S. El-Deiry. Engineering TRAIL-expressing immune cells to target GI malignancies. [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 4070.

Abstract 3929: MDMX overexpression in cancer cells confers significant resistance to MDMX inhibitor XI-006 and may modulate chemosensitivity through suppressing p53 activation of pro-apoptotic factors

MDM2 inhibition has gained popularity in recent years as a therapeutic strategy in targeting both solid tumors and hematological malignancies, and several small molecule inhibitors of the p53-MDM2 binding interface have progressed into clinical trials in recent years. Alongside direct stabilization of p53, MDM2 has further been identified to have immune implications in terms of CD8+ T-cell mediated anti-tumor immunity and checkpoint-blockade therapies. However, little work has been done to explore the therapeutic targeting potential of related protein MDMX (MDM4). Pan-cancer analyses conducted by our lab (in part presented at the ASCO 2022 Annual Meeting) identify an important role of MDMX in several tumor types. Particularly, MDMX amplification is associated with a higher risk of brain and liver metastasis, and MDMX amplification itself also presents with significant frequency (10%) in glioblastoma multiforme (GBM). Notably, MDMX amplification also served as a better predictor of reduced overall survival in NSCLC following checkpoint-blockade. We have also previously reported on associations between MDMX amplification and CDKN2A deep deletions in melanoma, a predictor of favorable response to checkpoint blockade. Such findings establish the need for further exploration to be done and the role of MDMX both in cell phenotype and potential immune regulation to be better characterized. Preliminary data acquired from transient overexpression experiments using lipofection of MDMX cDNA and MDMX inhibitor XI-006 (NSC207895) alone and in combination with chemotherapy further supports the viability of MDMX-inhibition as a therapeutic strategy in several cell lines. Overexpression of MDMX in HCT116 p53WT cells demonstrably confers remarkable resistance to MDMX inhibitor XI-006 at a 72-hour timepoint (IC50 of 104.75 uM in overexpressing cells versus 29.03 uM in WT), and treatment with oxaliplatin reveals both reduced basal and post-treatment expression of p53-upregulated modulator of apoptosis (PUMA). Further mechanistic workup of this phenomenon is underway, particularly with an emphasis on immuno-oncological therapeutic translations. Altogether, initial findings ultimately establish the need for further investigation into the mechanistic basis of MDMX-correlated clinical outcomes and the therapeutic potential of MDMX inhibition.

Citation Format: Andrew George, Arielle De La Cruz, Shengliang Zhang, Ilyas Sahin, Praveen Srinivasan, Maximilian Schwermann, Morgan Turcotte, Taylor Arnoff, Wafik S. El-Deiry. MDMX overexpression in cancer cells confers significant resistance to MDMX inhibitor XI-006 and may modulate chemosensitivity through suppressing p53 activation of pro-apoptotic factors. [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 3929.

Abstract 165: Establishment and characterization of Vogelgram-mimic colorectal cancer organoids as a laboratory tool

Colorectal cancer is a deadly disease with a 14% five-year survival rate once it metastasizes. The development of colorectal cancer involves a stepwise accumulation of genetic alterations in APC, KRAS, DCC, and p53 that is often described as a “Vogelgram,” named after the Vogelstein laboratory which laid the groundwork for our understanding of the molecular events leading to colorectal cancer. Organoids are a highly physiologically relevant laboratory tool that can provide valuable information regarding the tumor microenvironment. Here, we describe ex vivo establishment of APC fl/fl, CRE+, KRAS G12D +/-, P53 fl/fl colorectal organoids, which behave normally before tamoxifen treatment but acquire malignant behaviors after tamoxifen-induced loss of APC and p53. Colonic crypts from mice with colon-specific expression of APC fl/fl, CRE+, KRAS G12D +/-, P53 fl/fl were isolated and grown in Matrigel and WENRAS medium following the Organoid Core Facility protocol of the Legorreta Cancer Center. Western blot was used to measure levels of KRAS, KRAS G12D, APC, and p53 after 12 days of tamoxifen treatment and images were taken after 6 days of tamoxifen treatment. The organoid growth medium was collected after 3-4 days of incubation and run on the Luminex 200 platform to measure the levels of 50+ cytokines. Organoids were embedded in OCT and cryosectioned for IF staining with p53, p21, Ki67 and Lgr5 antibodies. IF stained organoid slides were imaged by confocal microscope at 40X magnification. Tamoxifen treatment (12 days) induces overexpression of KRAD G12D protein, reduces expression of APC, and abolishes p53 expression. At day 6, distinct morphological changes indicate malignant transformation. This transformation was accompanied by a trend toward decreased BAFF and CCL20. H&E staining revealed clearly visible intra-organoid structures and florescent labeling of Ki67, Lgr5, and p21 visualized by confocal microscope revealed distinct localization of these proteins within the organoid structures. Here, we describe Vogelgram-mimicking organoids that may be used as a valuable laboratory tool to study the processes involved in the stepwise transformation into colorectal cancer. We plan to use this validated system to evaluate drug sensitivity, cytokine secretion, and immune cell interactions along colorectal cancer progression. We also plan to characterize cell populations with single-cell RNA-seq, establish triangulated cultures, and conduct in vivo studies using this transgenic mouse model.

Citation Format: Leiqing Zhang, Lindsey Carlsen, Lanlan Zhou, Liz Hernandez Borrero, Wafik S. El-Deiry. Establishment and characterization of Vogelgram-mimic colorectal cancer organoids as a laboratory tool [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 165.

Abstract 1070: The anti-tumor efficacy of combining oral ATR kinase inhibitor ceralasertib with TIC10/ONC201, an oral Akt/ERK inhibitor, TRAIL pathway and integrated stress response inducer, in prostate cancer treatment

Prostate cancer is the most common cancer and the second leading cause of cancer death among men in the United States. There are 268,490 estimated new cases and 34,500 estimated deaths in 2022 according to the NIH. Patients with metastatic castration resistant prostate cancer (mCRPC) have a poor prognosis and the current treatment options show limited efficacy. From the TRAP trial, 20% of mCRPC patients are reported to bear DNA repair defects. Ceralasertib, formerly known as AZD6738, is a potent and selective orally bioavailable inhibitor of the ataxia tenlangiectasia and Rad3-related (ATR) kinase, which is involved in DNA repair in response to DNA damage and replication stress. Ceralasertib’s antitumor activity as a monotherapy in treating prostate cancer is moderate. Thus, we investigated a combination therapy of ceralasertib with ONC201, a potent and cytotoxic orally bioavailable inhibitor of the serine/threonine protein kinase Akt and extracellular signal-regulated kinase (ERK). Upon administration, ONC201 can induce tumor cell apoptosis mediated by tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and activate integrated stress response (IRS). Preliminary results demonstrate synergistic activity with the combination therapy in vitro using CellTiterGLO viability assay 72 hours in a 96 well plate post treatment. Ongoing studies using western blotting and cytokine profiling are intended to illustrate the mechanism behind the proven synergy. Our results aim to solve the overarching need in developing novel therapeutic strategies to overcome resistance in current prostate cancer treatments.

Citation Format: Yutong Xia, Maximilian P. Schwermann, Andrew George, Anna Ochsner, Benedito A. Carneiro, Wafik S. El-Deiry. The anti-tumor efficacy of combining oral ATR kinase inhibitor ceralasertib with TIC10/ONC201, an oral Akt/ERK inhibitor, TRAIL pathway and integrated stress response inducer, in prostate cancer treatment [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 1070.

Abstract 2671: Imipridones ONC201 and ONC206 reduce expression of neogenin and EZH1/2 which correlate with synergy following their combination with EZH1/2 or HDAC inhibitors in treatment of DMG and other tumors

Imipridones are a family of small molecule compounds including ONC201, ONC206 and ONC212 with anti-cancer activity mediated in part through activation of the integrated stress response, induction of TRAIL and its receptor, DR5, and activation of mitochondrial caseinolytic protease ClpP with consequent impairment of oxidative phosphorylation. Early clinical data have indicated that ONC201 provides clinical benefit in a subset of patients with histone H3K27M-mutated diffuse midline glioma (DMG). The H3K27M mutation prevents the function of EZH2 in methylating H3K27 on the mutated protein. This phenomenon implicates H3K27M and EZH2 in the mechanism of the anti-cancer effect of ONC201. EZH1 is a homolog of EZH2 and forms an alternative for EZH2 in assembling the PRC2 complex. We investigated the effects of ONC201, ONC206 or ONC212 on EZH1/2 by treating DMG cells and a panel of other solid tumor cells including GBM, DMG, CRC, PDAC, SCLC, prostate cancer, HCC and breast cancer cells with ONC201, ONC206 or ONC212. We observed that imipridones inhibit expression of both EZH1 and EZH2 in these tumors. RNA-seq analysis and RT-PCR showed no regulation of EZH1/2 at the level of transcription after ONC201 treatment. Linear regression revealed a correlation between extent of EZH1/2 inhibition and extent of cell viability suppression by ONC201 thereby providing further rationale for the combination of ONC201 and EZH1/2 inhibitors or HDAC inhibitors. We combined ONC201 or ONC206 or ONC212 plus a dual EZH1/2 inhibitor or the triple combination of ONC201, EZH2i and HDACi in DMG, GBM, prostate cancer and SCLC cells for 72 hours, performed a CellTiterGlo assay and observed synergies. The effective combination index (CI) of ONC201 plus tazemetostat ranges 0.04-0.64 in SU-DIPG-25 and 0.55-0.84 in SU-DIPG-13 DMG cells. The effective CI of ONC206 plus tazemetostat and panobinostat ranges 0.27-0.77 in U251 GBM and 0.11-0.71 in SU-DIPG-13 DMG cells. The effective CI of ONC201 plus dual EZH1/2 inhibitor, valemetostat, ranges 0.44-0.89 in H1048 SCLC cells, 0.14-0.90 in LNCaP prostate cancer cells, and 0.13-0.79 in SNB19 GBM cells. The effective CI of ONC212 plus valemetostat ranges 0.33-0.83 in 22Rv1. The synergy in inducing apoptosis was demonstrated by immunoblotting of cleaved-PARP. We also observed that ONC201 or ONC206 inhibit neogenin which is associated with invasion of DMG in SU-DIPG-13 cells. We conclude that ONC201 inhibits EZH1/2 in tumor cells and also neogenin in DMG cells. Inhibition of these proteins may play roles in the anti-cancer effect of ONC201. The synergies between ONC201 and EZH1/2 or HDAC inhibitors provide clues for developing novel therapy for the mentioned tumors. Overexpression of EZH2 is in process to elucidate the role of EZH2 in the mechanism of the anti-cancer effect of ONC201.

Citation Format: Yiqun Zhang, Wafik S. El-Deiry. Imipridones ONC201 and ONC206 reduce expression of neogenin and EZH1/2 which correlate with synergy following their combination with EZH1/2 or HDAC inhibitors in treatment of DMG and other tumors [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 2671.

Abstract 1066: PARP inhibitor rucaparib in combination with imipridones ONC201 or ONC212 demonstrates preclinical synergy against BRCA1/2-deficient breast, ovarian, and prostate cancer cells

BRCA1/2 genes encode proteins that mediate homologous recombination and repair (HRR). BRCA1/2 mutations increase risk of breast, ovarian, prostate and other cancers. BRCA1/2 mutated tumor cells are sensitive to PARP inhibitors (PARPi), that cause DNA replication fork to collapse. Approximately 40% of patients develop PARPi resistance through different mechanisms. One of the mechanisms of PARPi resistance is through P13k/Akt pathway activation. Imipridones are TRAIL-inducing compounds which are PERK-independent activators of the integrated stress response, and dual inhibitors of Akt/ERK. We hypothesized that combining imipridones with PARPi would overcome PARPi resistance due to Akt activation. PARPi also sensitize various solid tumors to recombinant TRAIL and DR5 agonist antibodies thereby further suggesting possible synergies between imipridones and PARPi. Our lab previously showed efficacy of imipridone ONC201 in BRCA-deficient cancer cells and potential synergy with olaparib (2017 AACR annual meeting abstract), without further investigating potential synergistic mechanisms. We explored combination drug synergy of rucaparib (PARP inhibitor) and imipridones (ONC212 and ONC201) in BRCA1/2-deficient breast, ovarian and prostate cancer cell lines. CellTiterGLO viability assays were performed after 72 hours to demonstrate synergistic effects of combination treatment. Western blots were performed to investigate the effect of combination treatment on the Akt pathway, as well as expression of cellular metabolic stress protein ATF4. Cytokine profiling using the Luminex 200 technology was used to study the effect of treatment on the tumor microenvironment. Combination treatment (rucaparib and ONC212, rucaparib and ONC201) in BRCA–deficient cell lines (HCC1937, PEO1, KURAMOCHI, 22RV1, LNCAP) showed synergistic reduction in cell viability. In the HCC 1937 cell line, combination studies of rucaparib-ONC212 and rucaparib-ONC201 showed a synergystic effect, as calculated by Compusyn software, combination indexes below one were observed at concentration of 0.29-37.5 of µM rucaparib with ONC201 at 1.25-5 µM and ONC212 6.25-50 nM with the best combination index of 0.7 for rucaparib-ONC201 combination and 0.31 for rucaparib-ONC212. We similarly observed synergy in other cell lines with combination treatment. Western blot analysis of rucaparib-ONC212 combination showed total Akt protein reduction and an increase in ATF4 consistent with the synergistic effects. Further studies are ongoing to characterize possible mechanisms and effects of PARP inhibitor-imipridone combination treatment on immune-mediated killing. Our findings identify novel PARP inhibitor-imipridone therapy combinations that can be further developed for treatment of BRCA1/2 deficient cancers.

Citation Format: Maryam Ghandali, Kelsey E. Huntington, praveen Srinivasan, Don S. Dizon, Stephanie L. Graff, Benedito A. Carneiro, Wafik S. El-Deiry. PARP inhibitor rucaparib in combination with imipridones ONC201 or ONC212 demonstrates preclinical synergy against BRCA1/2-deficient breast, ovarian, and prostate cancer cells [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 1066.

Abstract 4812: Inhibition of Smurf2 E3 ubiquitin ligase by heclin and its analogues enhances HIF-1α expression and transcriptional activity in normoxia or hypoxia

Hypoxia-inducible factors (HIFs) act as transcription factors and play an essential role in cellular and systemic responses to low oxygen environments. HIF-1α expression is induced in acute hypoxia typically through failure of its ubiquitination and degradation mediated by Von Hippel-Lindau (VHL). Previously we discovered a non-canonical mechanism where the SMAD specific E3 ubiquitin protein ligase 2 (Smurf2) promotes the ubiquitination of HIF-1α and reduces HIF-1α level in HCT116 colorectal cancer cells. Smurf2 is a HECT-type ubiquitin ligase known to interact with Smad proteins, leading to their ubiquitination and proteasomal degradation. Overexpression of Smurf2 decreased HIF-1α expression in HCT116 and SW480 colorectal cancer cells under hypoxia as well as in RCC4 VHL-deficient kidney renal clear cell carcinoma cells under normoxia. Treatment with MG132 at least partially rescued the expression of HIF-1α following Smurf2 overexpression, indicating involvement of proteasome-dependent degradation in Smurf2-mediated HIF-1α destabilization. Knockdown of SMURF2 increased HIF-1α expression under normoxia in HCT116 and RCC4 cells. To investigate the effect of Smurf2 inhibition, we tested a selective reversible inhibitor of HECT E3 ubiquitin ligases, heclin, along with its analogues, PYR-41, C646 and 4E1RCat. Treatment with heclin increased HIF-1α expression in HCT116 under hypoxia as well as in SW480 and RCC4 cells under normoxia in a dose-dependent manner. PYR-41 elevated the level of HIF-1α level in HCT116 cells under hypoxia, in RCC4 cells under normoxia and in SW480 cells under both normoxia and hypoxia. To examine the effect on HIF transcriptional activity, we performed luciferase reporter assay using plasmids containing the hypoxia response element (HRE) from the PGK1 promoter and the VEGF promoter, respectively. PYR-41 induced transcriptional activity on PGK1-HRE in both HCT116 and SW480 cells. 4E1RCat robustly activated transcription on both VEGF-HRE and PGK1-HRE in HCT116 and SW480 cells. In summary, Smurf2 targets HIF-1α for ubiquitination and degradation independently of oxygen concentration and inhibition of Smurf2 to stimulate HIF activity under normoxia or hypoxia may be beneficial in pathological circumstances featuring anemia and hypoxemia.

Citation Format: Shuai Zhao, Wafik S. El-Deiry. Inhibition of Smurf2 E3 ubiquitin ligase by heclin and its analogues enhances HIF-1α expression and transcriptional activity in normoxia or hypoxia. [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 4812.

Abstract 3734: Neuroendocrine differentiation (ND) in sensitivity of neuroendocrine tumor (NET) cells to ONC201/TIC10 cancer therapeutic

Neuroendocrine tumors (NETs) harbor neuroendocrine differentiation (ND) with specific markers including protein gene product 9.5 (PGP9.5) and Chromogranin A (CgA). In prostate cancers (PC), ND is induced by BRN2/SOX2 transcription factors. NET-like cells with low or absent androgen receptor (AR) signaling cause hormone therapy resistance and poor prognosis in PC. Small cell lung carcinoma (SCLC), a high-grade NET, presents with metastasis early and has poor survival. ONC201/TIC10 is a small molecule inducer of TRAIL signaling in clinical trials. ONC201 antagonizes dopamine D2 or D3 receptors (DRD2/DRD3) and is an agonist of mitochondrial caseinolytic protease P (ClpP) resulting in activation of DR5/TRAIL-dependent apoptosis involving the integrated stress response (ISR). ONC201 is active in various malignancies including H3K27M-mutated glioma and NETs expressing high levels of DRD2. We hypothesized that altered BRN2/SOX2 may impact NET apoptosis by ONC201 through the ISR and TRAIL/DR5. We analyzed the expression of neuroendocrine markers PGP9.5, CgA, SOX2, and BRN2, as well as markers of TRAIL signaling pathway markers ATF4, DR5, ClpP, ClpX, and DRD2/DRD3 in PC and SCLC cell lines (N=6) ± treatment with ONC201. Specifically, we compared pre-treatment protein expression levels with the IC50. Our results reveal that DU145 (IC50=3.11μM), PC3 (IC50=3.02μM), and LNCaP (IC50=1.33μM) are ONC201 sensitive. H1417 SCLC expresses CgA, unlike PC3 and DU145. PGP9.5 is expressed in these lines. PGP9.5 is expressed in PC3, DU145, H1417, and H1048 but not in LNCaP and 22RV1. BRN2 is expressed in PC3, H1417, and H1048 but not DU145, LNCaP, or 22RV1. ClpX is expressed in all 6 lines but at lower levels in SCLC. ClpP is expressed in the 6 lines. DR5 is expressed at higher levels in PC3, DU145, LNCaP, and 22RV1 PC versus H1417 and H1048 SCLC. SOX2 is expressed at high levels in H1417 cells. These results are establishing the landscape of ND in PC and SCLC lines for further experimentation and testing of our hypothesis. To characterize the association of BRN2 dysregulation with ONC201 sensitivity, we are performing BRN2/SOX2 knockdown experiments using siRNA and evaluating effects towards ONC201 sensitivity. Our results provide insights into molecular mechanisms of ND in PC and SCLC sensitivity to ONC201. We are also currently working to overexpress BRN2 and SOX2 in cell lines to analyze the impact on neuroendocrine differentiation and ONC201 sensitivity.

Citation Format: Elizabeth C. Ding, Wafik S. El-Deiry. Neuroendocrine differentiation (ND) in sensitivity of neuroendocrine tumor (NET) cells to ONC201/TIC10 cancer therapeutic. [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 3734.

Abstract 4898: Imipridones and EZH2 inhibitors induce similar changes in cytokines and regulated genes in GBM and DMG while vorinostat potentiates anti-tumor efficacy despite variability in cytokine profiles

TIC10/ONC201 and ONC206 are small molecule imipridones with anti-cancer activity. ONC201, EZH2i and HDACi can modulate tumor microenvironment (TME) and antitumor immunity. We studied the impact of these drugs or their combinations on the TME or tumor immunity by investigating cytokine profiles. We treated U251 GBM and HCT116 CRC cells with vorinostat and found upregulation of CXCL11, CXCL14, INF-γ and TRAIL, and downregulation of prolactin, CXCL9, VEGF and CCL2 in U251. CXCL11 promotes anti-tumor immunity by increasing activated CD8+ T cells in tumors but was associated with metastasis of GBM. CXCL13 induces tertiary lymphoid structures and enhances infiltration of CD8+ T cells in tumors. INF-γ enhances antigen presentation and promotes activation of NK cells. Vorinostat upregulated the secretion of pro-immune cytokines and TRAIL which induces tumor apoptosis. Downregulated cytokines in U251 were prolactin, CXCL9 involved in tumor growth and metastasis, VEGF, and CCL2 involved in immunosuppression in GBM. Cytokines upregulated in HCT116 included IL-8 contributing to CRC progression, and CXCL13, and CXCL11 which correlates with anti-tumor immunity in colon cancer. Downregulated cytokines in HCT116 were soluble TRAIL R2 functioning as a decoy receptor for TRAIL, VEGF, and prolactin. We treated DMG, GBM and HCC cells with imipridones, EHZ2i tazemetostat or HDACi panobinostat alone or combination of imipridones plus tazemetostat or panobinostat or the triple combination of imipridone plus tazemetostat and panobinostat. We observed that cytokines impairing immunity were downregulated and cytokines promoting immunity were upregulated by individual drugs or combinations. Hep3B HCC cells showed the most robust changes among the mentioned tumors with respect to the changes of cytokine profile following the treatments. Imipridone or EZH2i treated cells showed similar cytokine profile changes in tumor cells. Imipridones downregulated EZH1 and EZH2 proteins in tumor cells. We RNA-seq to investigate gene expression profiles following treatment with ONC201 or tazemetostat. In GBM and DMG, ONC201 and tazemetostat shared similar top regulated genes. GO enrichment analysis showed overlap of top regulated pathways between ONC201 and EZH2i treated cells. Shared regulated pathways in U251 included cell cycle arrest, cell adhesion, nervous system development, cell proliferation, negative regulation of proliferation, PERK-mediated unfolded protein response, extracellular matrix organization, regulation of transcription from RNA polymerase II promoter, and cellular response to hypoxia pathways. We conclude that imipridones ONC201, ONC206, and ONC212 which reduce EZH1 and EZH2 proteins share similar cytokine alterations, gene expression targets and actions with EZH2 inhibitors.

Citation Format: Yiqun Zhang, Kelsey Huntington, Wafik S. El-Deiry. Imipridones and EZH2 inhibitors induce similar changes in cytokines and regulated genes in GBM and DMG while vorinostat potentiates anti-tumor efficacy despite variability in cytokine profiles. [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 4898.

Advances in Liquid Biopsy Technology and Implications for Pancreatic Cancer

Pancreatic cancer is a highly aggressive malignancy with a climbing incidence. The majority of cases are detected late, with incurable locally advanced or metastatic disease. Even in individuals who undergo resection, recurrence is unfortunately very common. There is no universally accepted screening modality for the general population and diagnosis, evaluation of treatment response, and detection of recurrence relies primarily on the use of imaging. Identification of minimally invasive techniques to help diagnose, prognosticate, predict response or resistance to therapy, and detect recurrence are desperately needed. Liquid biopsies represent an emerging group of technologies which allow for non-invasive serial sampling of tumor material. Although not yet approved for routine use in pancreatic cancer, the increasing sensitivity and specificity of contemporary liquid biopsy platforms will likely change clinical practice in the near future. In this review, we discuss the recent technological advances in liquid biopsy, focusing on circulating tumor DNA, exosomes, microRNAs, and circulating tumor cells.

GSK-3 inhibitor elraglusib enhances tumor-infiltrating immune cell activation in tumor biopsies and synergizes with anti-PD-L1 in a murine model of colorectal cancer

Inhibition of GSK-3 using small-molecule elraglusib has shown promising preclinical antitumor activity. Using in vitro systems, we found that elraglusib promotes immune cell-mediated tumor cell killing, enhances tumor cell pyroptosis, decreases tumor cell NF-κB-regulated survival protein expression, and increases immune cell effector molecule secretion. Using in vivo systems, we observed synergy between elraglusib and anti-PD-L1 in an immunocompetent murine model of colorectal cancer. Murine responders had more tumor-infiltrating T-cells, fewer tumor-infiltrating Tregs, lower tumorigenic circulating cytokine concentrations, and higher immunostimulatory circulating cytokine concentrations. To determine the clinical significance, we utilized human plasma samples from patients treated with elraglusib and correlated cytokine profiles with survival. Using paired tumor biopsies, we found that CD45+ tumor-infiltrating immune cells had lower expression of inhibitory immune checkpoints and higher expression of T-cell activation markers in post-elraglusib patient biopsies. These results introduce several immunomodulatory mechanisms of GSK-3 inhibition using elraglusib, providing a rationale for the clinical evaluation of elraglusib in combination with immunotherapy.

Statement of significance

Pharmacologic inhibition of GSK-3 using elraglusib sensitizes tumor cells, activates immune cells for increased anti-tumor immunity, and synergizes with anti-PD-L1 immune checkpoint blockade. These results introduce novel biomarkers for correlations with response to therapy which could provide significant clinical utility and suggest that elraglusib, and other GSK-3 inhibitors, should be evaluated in combination with immune checkpoint blockade.

Molecular characterization and clinical outcomes of pancreatic neuroendocrine tumors (pNENs) harboring PAK4-NAMPT alterations

649

Background: The mTOR inhibitor, Everolimus (EVE), is FDA-approved for the treatment of advanced PNENs on the basis of delay of progression. The RADIANT-3 trial showed an increase in PFS from 4.6 to 11 months compared to placebo with an ORR of only 5%. Prior studies suggest that targeting the aberrant expression of mTOR regulators p21 activated kinase 4 (PAK4) and nicotinamide adenine dinucleotide biosynthesis enzyme nicotinamide phosphoribosyltransferase (NAMPT) in PNENs sensitizes these tumors to EVE. To further qualify these observations, we queried a large real-world dataset of PNENs, characterizing the molecular and immune landscapes, as well as the clinical outcomes associated with aberrant PAK4 and NAMPT expression. Methods: 294 cases of PNENs were analyzed using Next Generation Sequencing (NextSeq) and Whole Exome and Whole Transcriptome Sequencing (NovaSeq) at Caris Life Sciences (Phoenix, AZ). For our analyses, we stratified our study cohort into four groups based on the median expression of PAK4 and NAMPT: PAK4-low/NAMPT-low, PAK4-low/NAMPT-high, PAK4-high/NAMPT-low and PAK4-high/NAMPT-high. Significance was determined using chi-square, Fisher-Exact or Mann-Whitney U, and p-values were adjusted for multiple comparisons (q < 0.05). Results: High prevalence of mutations in PTEN (10.71% vs 1.18%; p < 0.05, q > 0.05), a tumor suppressor of the mTOR pathway and high expression of genes activated in response to mTOR activation such as SLC2A1 (3.07-fold), PFKP (3.32-fold), SCD (2.70-fold), MVK (2.92-fold) and G6PD (2.58-fold) were observed in PAK4-high/NAMPT-high compared to the PAK4-low/NAMPT-low tumors (all q < 0.05). A congruent enrichment of PI3K/AKT/mTOR and glycolysis pathways by single-sample gene set enrichment analysis was observed in these tumors (all q < 0.05). When querying the immune landscape, we observed enrichment in inflammatory response, IL6/JAK/STAT3, IL2/STAT5 signaling pathways and immune checkpoint genes such as PDCD1 (5.14-fold), CD274 (2.84-fold), PDCD1LG2 (2.44-fold), CD80 (3.00-fold), CD86 (2.82-fold), IDO1 (1.92-fold), LAG3 (3.09-fold), HAVCR2 (2.66-fold) and CTLA4 (4.49-fold) in the PAK4-high/NAMPT-high tumors (all q < 0.05). Immune cell infiltration estimates revealed an increase in Neutrophils, NK cells and Tregs in the PAK4-high/NAMPT-high tumors (p < 0.05, q > 0.05). Conclusions: Our study demonstrates that PAK4-high/NAMPT-high PNENs are associated with distinct molecular and immune profiles. While the dual blockade of PAK4 and NAMPT has been reported to enhance the efficacy of EVE in PNENs, whether such a blockade would enhance the efficacy of immunotherapeutics warrants further investigation.

Characterizing colorectal cancer (CRC) carriers of the recessive MUTYH founders (G396D/Y179C) and the low-penetrance APC founder APC-I1307K mutation

210

Background: The clinical significance of CRC risk imparted by prevalent recessive mutations MUTYH-G396D and Y179C (Caucasian carrier rate 1/50) and the low-penetrance APC-I1307K mutation (Ashkenazi Jewish carrier rate ~1/15) is debated. Evidence supporting differential mutational spectrum, immune biology, and clinical outcomes in tumors that arise in carriers could lend support to their relevance. We characterized CRC carriers of MUTYH-G396D/Y179C and APC-I1307K, as well as those with concurrent second-hit mutations, in comparison to MUTYH or APC wild-type (WT) tumors. Methods: Retrospective review of patient samples (n = 13,896) submitted to a CLIA-certified laboratory (Caris Life Sciences, Phoenix, AZ) for next-generation sequencing (NGS) of DNA (592-gene or whole exome) and RNA (whole transcriptome). Deficient mismatch repair/high microsatellite instability (dMMR/MSI-H) was assessed by IHC/NGS. PD-L1 expression was tested by IHC (SP142; positive (+): ≥2+, ≥%5). Immune cell infiltration was estimated by RNA deconvolution using quanTIseq (Finotello, 2019). Presumed monoallelic (mMut) and biallelic mutations (bMut) included those with or without, respectively, a mutation or variant allele frequency ≥60%. Statistical significance determined by Fisher’s-Exact/Mann Whitney/X2 tests. *indicates raw p-value that was not significant after correction for multiple comparisons. Real world overall survival was obtained from insurance claims data, with Kaplan-Meier estimates used for comparison. Results: MUTYH-G396D/Y179C (119, 26 bMut) and APC-I1307K (11 mMut, ) alterations were identified, with all 3 founders being more common among male patients and associated with slightly increased median age at time of biopsy. MUTYH bMut had higher rates of genomic vs mMut 6.0%, p=0.02*; WT 11.0%, p=0.05*), and increased dendritic cell (p=0.04) and CD4 T-cell (p=0.007) proportions. APC bMut tumors were less frequently dMMR/MSI-H (2.6% vs mMut 18.%, p=0.11*; WT 15.5%, p=0.03*), TMB-H (2.6% vs mMut 27.3%, p=0.03*; WT 17.3%, p=0.02*), and PD-L1+ (0% vs mMut 18.2%, p=0.05*; WT 9.4%, p=0.04*), with enrichment of the canonical CMS2 subtype (44% vs 9% mMut, p<0.01; WT 11%, p<0.0001). In pMMR/MSS CRC, the prognosis of MUTYH founder carriers was superior to MUTYH WT tumors (HR 0.44, CI 0.25-0.78, p=0.004), with a non-significant trend toward greater sensitivity (HR 0.50, CI 0.21-1.2, p=0.). The prognosis of APC I1307K carriers was superior to APC WT tumors (HR 0.51, CI 0.34-0.76, p<0.001). Conclusions: Carrier status of MUTYH-G396D/Y179C and APC-I3017K founders may positively impact prognosis in patients with pMMR/MSS tumors. Differences may derive from distinct molecular signatures in tumors from MUTYH and APC founder mutations and warrant further investigation of these biomarkers in CRC.

Clinical features of patients with MTAP-deleted bladder cancer

Advanced urothelial carcinoma continues to have a dismal prognosis despite several new therapies in the last 5 years. FGFR2 and FGFR3 mutations and fusions, PD-L1 expression, tumor mutational burden, and microsatellite instability are established predictive biomarkers in advanced urothelial carcinoma. Novel biomarkers can optimize the sequencing of available treatments and improve outcomes. We describe herein the clinical and pathologic features of patients with an emerging subtype of bladder cancer characterized by deletion of the gene MTAP encoding the enzyme S-Methyl-5'-thioadenosine phosphatase, a potential biomarker of response to pemetrexed. We performed a retrospective analysis of 61 patients with advanced urothelial carcinoma for whom demographics, pathologic specimens, next generation sequencing, and clinical outcomes were available. We compared the frequency of histology variants, upper tract location, pathogenic gene variants, tumor response, progression free survival (PFS) and overall survival (OS) between patients with tumors harboring MTAP deletion (MTAP-del) and wild type tumors (MTAP-WT). A propensity score matching of 5 covariates (age, gender, presence of variant histology, prior surgery, and prior non-muscle invasive bladder cancer) was calculated to compensate for disparity when comparing survival in these subgroups. Non-supervised clustering analysis of differentially expressed genes between MTAP-del and MTAP-WT urothelial carcinomas was performed. MTAP-del occurred in 19 patients (31%). Tumors with MTAP-del were characterized by higher prevalence of squamous differentiation (47.4 vs 11.9%), bone metastases (52.6 vs 23.5%) and lower frequency of upper urinary tract location (5.2% vs 26.1%). Pathway gene set enrichment analysis showed that among the genes upregulated in the MTAP-del cohort, at least 5 were linked to keratinization (FOXN1, KRT33A/B, KRT84, RPTN) possibly contributing to the higher prevalence of squamous differentiation. Alterations in the PIK3 and MAPK pathways were more frequent when MTAP was deleted. There was a trend to inferior response to chemotherapy among MTAP-del tumors, but no difference in the response to immune checkpoint inhibitors or enfortumab. Median progression free survival after first line therapy (PFS1) was 5.5 months for patients with MTAP-WT and 4.5 months for patients with MTAP-del (HR = 1.30; 95% CI, 0.64-2.63; P = 0.471). There was no difference in the time from metastatic diagnosis to death (P = 0.6346). Median OS from diagnosis of localized or de novo metastatic disease was 16 months (range 1.5-60, IQR 8-26) for patients with MTAP-del and 24.5 months (range 3-156, IQR 16-48) for patients with MTAP-WT (P = 0.0218), suggesting that time to progression to metastatic disease is shorter in MTAP-del patients. Covariates did not impact significantly overall survival on propensity score matching. In conclusion, MTAP -del occurs in approximately 30% of patients with advanced urothelial carcinoma and defines a subgroup of patients with aggressive features, such as squamous differentiation, frequent bone metastases, poor response to chemotherapy, and shorter time to progression to metastatic disease.

ERBB family fusions are recurrent and actionable oncogenic targets across cancer types

Purpose

Gene fusions involving receptor tyrosine kinases (RTKs) define an important class of genomic alterations with many successful targeted therapies now approved for ALK, ROS1, RET and NTRK gene fusions. Fusions involving the ERBB family of RTKs have been sporadically reported, but their frequency has not yet been comprehensively analyzed and functional characterization is lacking on many types of ERBB fusions.

Materials and methods

We analyzed tumor samples submitted to Caris Life Sciences (n=64,354), as well as the TCGA (n=10,967), MSK IMPACT (n=10,945) and AACR GENIE (n=96,324) databases for evidence of EGFR, ERBB2 and ERBB4 gene fusions. We also expressed several novel fusions in cancer cell lines and analyzed their response to EGFR and HER2 tyrosine kinase inhibitors (TKIs).

Results

In total, we identified 1,251 ERBB family fusions, representing an incidence of approximately 0.7% across all cancer types. EGFR, ERBB2, and ERBB4 fusions were most frequently found in glioblastoma, breast cancer and ovarian cancer, respectively. We modeled two novel types of EGFR and ERBB2 fusions, one with a tethered kinase domain and the other with a tethered adapter protein. Specifically, we expressed EGFR-ERBB4, EGFR-SHC1, ERBB2-GRB7 and ERBB2-SHC1, in cancer cell lines and demonstrated that they are oncogenic, regulate downstream signaling and are sensitive to small molecule inhibition with EGFR and HER2 TKIs.

Conclusions

We found that ERBB fusions are recurrent mutations that occur across multiple cancer types. We also establish that adapter-tethered and kinase-tethered fusions are oncogenic and can be inhibited with EGFR or HER2 inhibitors. We further propose a nomenclature system to categorize these fusions into several functional classes.

Non-canonical approaches to targeting hypoxic tumors

Hypoxia is a common characteristic in solid cancers. Hypoxia-inducible factors (HIFs) are involved in various aspects of cancer, such as angiogenesis, metastasis and therapy resistance. Targeting the HIF pathway has been regarded as a challenging but promising strategy in cancer treatment with recent FDA approval of a HIF2α-inhibitor. During the past several decades, numerous efforts have been made to understand how HIFs participate in cancer development and progression along with how HIF signaling can be modulated to achieve anti-cancer effect. In this chapter, we will provide an overview of the role of hypoxia and HIFs in cancer, summarize the oxygen-dependent and independent mechanisms of HIF-1α regulation, and discuss emerging approaches targeting hypoxia and HIF signaling which possess therapeutic potential in cancer. We will emphasize on two signaling pathways, involving cyclin-dependent kinases (CDKs) and heat shock protein 90 (HSP90), which contribute to HIF-1α (and HIF-2α) stabilization in an oxygen-independent manner. Through reviewing their participation in malignant progression and the potential targeting strategies, we discuss the non-canonical approaches to target HIF signaling in cancer therapy.

Anti-cancer immune responses to DNA damage response inhibitors: Molecular mechanisms and progress toward clinical translation

DNA damage response inhibitors are widely used anti-cancer agents that have potent activity against tumor cells with deficiencies in various DNA damage response proteins such as BRCA1/2. Inhibition of other proteins in this pathway including PARP, DNA-PK, WEE1, CHK1/2, ATR, or ATM can sensitize cancer cells to radiotherapy and chemotherapy, and such combinations are currently being tested in clinical trials for treatment of many malignancies including breast, ovarian, rectal, and lung cancer. Unrepaired DNA damage induced by DNA damage response inhibitors alone or in combination with radio- or chemotherapy has a direct cytotoxic effect on cancer cells and can also engage anti-cancer innate and adaptive immune responses. DNA damage-induced immune stimulation occurs by a variety of mechanisms including by the cGAS/STING pathway, STAT1 and downstream TRAIL pathway activation, and direct immune cell activation. Whether or not the relative contribution of these mechanisms varies after treatment with different DNA damage response inhibitors or across cancers with different genetic aberrations in DNA damage response enzymes is not well-characterized, limiting the design of optimal combinations with radio- and chemotherapy. Here, we review how the inhibition of key DNA damage response enzymes including PARP, DNA-PK, WEE1, CHK1/2, ATR, and ATM induces innate and adaptive immune responses alone or in combination with radiotherapy, chemotherapy, and/or immunotherapy. We also discuss current progress in the clinical translation of immunostimulatory DNA-damaging treatment regimens and necessary future directions to optimize the immune-sensitizing potential of DNA damage response inhibitors.

Clinical activity of 9-ING-41, a small molecule selective glycogen synthase kinase-3 beta (GSK-3β) inhibitor, in refractory adult T-Cell leukemia/lymphoma

GSK-3β is a serine/threonine kinase implicated in tumorigenesis and chemotherapy resistance. GSK-3β blockade downregulates the NF-κB pathway, modulates immune cell PD-1 and tumor cell PD-L1 expression, and increases CD8 + T cell and NK cell function. We report a case of adult T-cell leukemia/lymphoma (ATLL) treated with 9-ING-41, a selective GSK-3β inhibitor in clinical development, who achieved a durable response. A 43-year-old male developed diffuse lymphadenopathy, and biopsy of axillary lymph node showed acute-type ATLL. Peripheral blood flow cytometry revealed a circulating clonal T cell population, and CSF was positive for ATLL involvement. After disease progression on the 3^rd line of treatment, he started treatment with 9-ING-41 monotherapy in a clinical trial (NCT03678883). CT imaging after seven months showed a partial response. Sustained reduction of peripheral blood ATLL cells lasted 15 months. Treatment of patient-derived CD8 + T cells with 9-ING-41 increased the secretion of IFN-γ, granzyme B, and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In conclusion, treatment of a patient with refractory ATLL with the GSK-3β inhibitor 9-ING-41 resulted in a prolonged response. Ongoing experiments are investigating the hypothesis that 9-ING-41-induced T cell activation and immunomodulation contributes to its clinical activity. Further clinical investigation of 9-ING-41 for treatment of ATLL is warranted.

Abstract 3947: Antitumor efficacy of combination treatment with ONC201 and enzalutamide or darolutamide in metastatic castration-resistant prostate cancer

The androgen receptor (AR) signaling pathway plays a primary role in prostate cancer progression. Various types of androgen receptor antagonists including enzalutamide, abiraterone and apalutamide have been widely used as single agents to treat patients with advanced disease. However, despite the initial improvements, patients with metastatic castration-resistant prostate cancer (mCPRC) frequently develop resistance, resulting in limited overall survival benefit. Darolutamide is a novel next-generation androgen receptor-signaling inhibitor currently in phase III clinical trials and has shown efficacy and tolerability in treating non-metastatic castration-resistant prostate cancer. ONC201 is a small molecule belonging to the imipridone class that activates the integrated stress response (ISR) pathway and upregulates TRAIL. ONC201 has demonstrated promising antiproliferative and proapoptotic effects in a variety of tumor types and is currently being evaluated in phase I/II clinical trials. This study investigates the integrated stress response and androgen receptor signaling as mechanisms for antitumor efficacy with ONC201 and enzalutamide or darolutamide as single agents or in combination against mCRPC in vitro and in vivo. Three mCRPC cell lines 22RV1, LNCaP, and PC3 were treated with ONC201, darolutamide, and enzalutamide as single agents or in combinations. In 22RV1, the single agent IC50 was calculated to be 1.22uM for ONC201, 51.5uM for darolutamide and &gt;80uM for enzalutamide. In LNCaP, the single agent IC50s are 1.67uM for ONC201, 58.7uM for darolutamide, and 4.05uM for enzalutamide. In 22RV1, the combination index (CI) of 0.38 was obtained when treated with 40uM of darolutamide and 1.25uM of ONC201, CI was 0.35 when treated with 80uM of enzalutamide and 1.25uM of ONC201. In LNCaP, CI of 0.19 was obtained when treated with 10uM of darolutamide and 0.3125uM of ONC201, CI was 0.45 when treated with 5uM of enzalutamide and 2uM of ONC201. Results showed that ONC201 synergized with darolutamide and enzalutamide and decreased cell viability. In both 22RV1 and LNCaP cell lines, when compared to single agents, combination treatments of ONC201 and darolutamide or enzalutamide reduced PSA level and demonstrated proapoptotic effects. Mouse xenograft models with luciferase expressing 22RV1 and LNCaP cell lines are currently being treated with ONC201 and darolutamide or enzalutamide as single agents or in combinations and the in vivo studies are ongoing. Our data provide insights to improved therapeutic benefits of combination treatment that can be further developed for more efficient anticancer strategies.

Citation Format: Jinxuan Laura Wu, Lanlan Zhou, Leiqing Zhang, Kelsey E. Huntington, Benedito Carneiro, Wafik S. El-Deiry. Antitumor efficacy of combination treatment with ONC201 and enzalutamide or darolutamide in metastatic castration-resistant prostate 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 3947.

Abstract 319: Imipridone ONC212 and trametinib combination therapy demonstrates anti-neoplastic effects through immune-mediated mechanisms in pancreatic ductal adenocarcinoma cell lines

Pancreatic ductal adenocarcinoma (PDAC) is characterized by limited therapeutic options and an extremely high mortality-to-incidence ratio. Chemotherapy remains the primary treatment for metastatic disease and results in only modest improvements in median overall survival, typically with significant toxicity. We previously reported a novel treatment approach with the combination of the imipridone ONC212 and the MEK inhibitor trametinib. This combination demonstrated synergy in multiple KRAS-mutated and KRAS wild-type pancreatic cancer cell lines (BxPC3, PANC1, HPAF-II, AsPC-1). Using Western Blot, we assessed markers of autophagy, including Beclin-1 and LC3B, as well as key second messenger pathway activation/suppression with p-AKT/AKT and p-ERK/ERK. The mechanism of this synergy appears to be heterogeneous, working through autophagy inhibition, MAPK/PI3K pathway perturbation, activation of the integrated stress response and increased cell surface expression of death receptor 5. Further investigation has revealed that ONC212 also appears to synergize with various autophagy inhibitors including hydroxychloroquine and chloroquine. We hypothesized that combining trametinib and ONC212 may also induce cell death in-part through immune cell-mediated mechanisms. To explore this, we performed immune cell co-culture experiments using HPAF-II PDAC cells and natural killer (NK-92) cells at a 1:1 effector-to-target cell ratio with or without ONC212, trametinib, or the combination of the two at different concentrations. We assessed the levels of NK cell mediated-tumor cell death 4, 8, and 24-hours after simultaneous treatment and initiation of co-culture using fluorescent microscopy. Compared to trametinib, ONC212 only treated co-culture showed greater NK cell-mediated tumor cell death. At 24-hours, we also observed an increase in NK cell-mediated killing of PDAC cells with dual treatment as compared to single agent alone or vehicle controls. Importantly, this combination did not appear to have any effect on NK or tumor cell viability. Thus, this combination may represent a potential therapeutic modality for PDAC and may hold promise if combined with immunotherapy. Further in vitro experiments will be conducted to evaluate the effect of ONC212, trametinib, and other autophagy inhibitors on the PDAC tumor microenvironment using a T cell co-culture system. Similarly, in vivo murine studies will also be performed to assess the translational potential of this combination.

Citation Format: Alexander G. Raufi, Arielle De La Cruz, Lindsey Carlsen, Kelsey Huntington, Lanlan Zhou, Varun Prabhu, Joshua Allen, Wafik S. El-Deiry. Imipridone ONC212 and trametinib combination therapy demonstrates anti-neoplastic effects through immune-mediated mechanisms in pancreatic ductal adenocarcinoma cell lines [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 319.

Abstract LB516: MDM2/MDM4 amplification and CDKN2A deletion in melanoma brain metastases and GBM may have implications for targeted therapeutics and immunotherapy

Melanoma has a five-year survival rate of 27% for distant metastatic disease, and there remains a paucity of targeted therapies for metastatic disease and biomarkers that predict metastasis to specific sites. We analyzed 1081 primary melanoma samples and 358 metastatic melanoma samples and found that metastatic disease is enriched for amplifications in both MDM2 and MDM4 compared to primary disease, and these amplifications are associated with a lower probability of overall survival. Two additional negative regulators of TP53, namely USP7 and PPM1D, are enriched for alterations in metastatic melanoma compared to primary melanoma. MDM4 amplifications are associated with a higher rate of metastasis to the brain, liver, and lungs, while MDM2 amplifications are associated with a higher rate of metastasis to the brain, liver, and adrenal glands. These findings suggest that patients with metastatic melanoma show an enhanced dysregulation of the TP53 pathway compared to primary disease; though still under ongoing preclinical evaluation to assess therapeutic implications, we propose that patients with metastatic melanoma and TP53 wild-type status may be more likely to benefit from MDM2, MDM4, USP7, and PPM1D inhibitors, both alone and in combination, compared to those with primary disease. Additionally, we found that patients with MDM2 alterations were more likely to have a deep deletion in CDKN2A, alterations that are also associated with a higher rate of metastasis to the brain. We found that patients with a CDKN2A deep deletion had a statistically significant higher rate of alterations in TTN, MUC16, LRP1B, NF1, and SERPINB4, alterations that have all been previously associated with a favorable response to immune checkpoint inhibitors in melanoma. We therefore propose that CDKN2A deletion may serve as a biomarker to predict response to immunotherapy in melanoma. Moreover, given prior documented cases of patients diagnosed with both melanoma and glioblastoma multiforme (GBM), we found that GBM displays the highest rate of deep deletions in CDKN2A (54.39%) across all cancer types screened. We analyzed 619 GBM samples and found that 9.16% display an MDM2 amplification and 9.52% display an MDM4 amplification. Given the genomic similarities between melanoma and glioblastoma, we suggest that patients with melanoma or GBM and amplifications in MDM2/4 and CDKN2A deletions may need the development of combinations of targeted inhibitors of MDM2/4, CDK’s and immunotherapy. We are currently pursuing these translational directions.

Citation Format: Taylor E. Arnoff, Wafik S. El-Deiry. MDM2/MDM4 amplification and CDKN2A deletion in melanoma brain metastases and GBM may have implications for targeted therapeutics and immunotherapy [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 LB516.

Abstract 1008: Cell density-related variability in chemotherapeutic resistance patterns in human cancer cells

Assessment of chemosensitivity and resistance varies with cancer cell of origin, drug and culture conditions. However, it is also not uncommon to find multiple different IC50 values for the same chemotherapeutic treatments acting on the same tumor cell lines. The aim of this research was to investigate this discrepancy in phenotypes and elucidate relevant variables that influence them. We assessed chemosensivity as a function of tumor cell density by plating TOV-21G ovarian, HT29 colorectal, and U2OS osteosarcoma cell lines in 96-well plates at various seeding densities per well and treated them with various concentrations of cisplatin, 5-fluorouracil (5-FU), and etoposide, respectively. CellTiter Glo assays were performed at 72 hours of treatment to determine IC50. Cisplatin IC50 for TOV-21G cells plated at 50,000, 20,000, 10,000, 5,000, 2,000, 1,000, and 500 cells/well were 12.00 μM, 5.47 μM, 3.16 μM, 2.45 μM, 2.54 μM, 2.83 μM, and 2.66 μM, respectively. Etoposide IC50 for U2OS cells plated at the same seeding densities were 6.50 μM, 5.19 μM, 3.23 μM, 2.98 μM, 2.49 μM, 2.13 μM, and 1.88 μM, respectively. IC50 values for HT29 cells treated with 5-FU at 2,000, 1,000, and 500 cells/well were 35.89 μM, 19.74 μM, and 13.42 μM, respectively. TOV-21G, U2OS, and HT29 cells all showed differences in IC50 values depending on cell plating density. TOV-21G and U2OS cells both showed a gradual decrease and plateau in IC50 as the cancer cell density decreased from 50,000 cells/well to 500 cells/well. HT29 cells displayed a sharper IC50 decrease as the cell density decreased from 2,000 cells/well to 500 cells/well. Our experiments demonstrate that IC50 values are not static at 72 hours and that tumor cell density is an important variable in influencing observed tumor resistance to traditionally effective drugs. As the density of cancer cells increases, the cells develop more resistance to the associated chemotherapy and require higher quantities of drug to achieve the same level of growth inhibition. We are currently exploring underlying molecular mechanisms that may influence these changes in IC50 including cell survival signaling proteins, cell-cell contact or growth factors that may influence cell density-related chemoresistance.

Citation Format: Thomas Brown, Ujwal Punyamurtula, Jill Strandberg, Wafik S. El-Deiry. Cell density-related variability in chemotherapeutic resistance patterns in human cancer cells [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 1008.