Vulnerability Of Cancer Cells Research Articles

Abstract 1114: Evaluating strategies to harness metabolic vulnerabilities in cervical

Abstract Tumor cells frequently alter their metabolism to generate biomolecular intermediates for tumor maintenance and proliferation. Previous reports from Dr. Julie Schwarz’s laboratory have shown that cervical cancer cells with altered AKT/mTOR pathways show increased reliance on glucose and exogenous glutamine. The laboratory has introduced PIK3CA E545K mutation and PTEN null mutation in cervical cancer cell line SiHa. Further, to evaluate the role of glutamine metabolism in these genotypes, these cells were cultured in sequentially lower levels of glutamine until these cells were able to proliferate without exogenous glutamine supplementation. These isogenic long-term glutamine-deprived (QD) cells allow us to tease out the role of these specific mutations in cellular metabolism. In our study, long-term glutamine deprivation inhibits the proliferation of rapidly proliferating PI3K-AKT-altered cell lines. Even though glutamine is required for GSH synthesis, which quenches reactive oxygen species, QD cells were refractory to cisplatin and irradiation. Since PI3K-AKT altered were dependent on exogenous glutamine, it was expected that QD cells would have lower GLS levels to inhibit glutaminolysis. However, GLS levels in WT and QD were similar. Altogether, these data indicate that in PI3K-AKT altered cervical tumor glutamine antagonists can reduce tumor proliferation. Further glutamine reduction does not alter GLS levels and hence GLS can be targeted as well to further improve treatment outcomes. To evaluate the alternate metabolic dependencies in cervical cancer tumors, both cellular as well as secreted metabolites were evaluated. To identify alternative pathways that are activated in these glutamine-deprived cell lines, we cultured these cells in uniformly labeled 13C glucose. Mass spectrometric studies also evaluated the protein levels of various metabolic intermediates in glutamine-deprived cell lines compared to control cells. To confirm our observations, we used kit-based assays to evaluate metabolites in the cells. To further confirm the change in the metabolite pathway we evaluated changes in transcriptional changes of regulating proteins/enzymes. This pre-clinical study reinforced efforts that are anticipated to reveal new metabolic vulnerabilities of cancer cells that can be targeted by therapeutic interventions. This study also helped us evaluate druggable metabolic targets that can be targeted for effective tumor eradication along with conventional treatment. This understanding will help advance the pre-clinical trials persistent to the cure of cervical cancer. Citation Format: Dr Julie K. Schwarz, Dr Nishanth Gabriel, Aunannya Banik. Evaluating strategies to harness metabolic vulnerabilities in cervical [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1114.

Abstract 1048: Loss of MTAP expression is strongly linked to homozygous 9p21 deletion, unfavorable tumor phenotype and non-inflamed microenvironment in urothelial bladder cancer

Abstract 9p21 deletions are common in urothelial carcinoma and mostly include S-methyl-5′-thioadenosine phosphorylase (MTAP) a critical enzyme for DNA and RNA synthesis. Homozygous MTAP deletions result in a complete loss of expression which can be visualized by immunohistochemistry (IHC). Evidence is emerging that MTAP deficiency results in a critical vulnerability of cancer cells towards drugs targeting multiple different pathways that depend on a functional MTAP gene and causes resistance to immune checkpoint inhibitors. To determine the prevalence and clinical significance of MTAP deficiency and its relationship with the tumor microenvironment in urothelial bladder carcinomas, more than 2,500 tumors were analyzed by fluorescence in-situ hybridization (FISH) and IHC in a tissue microarray format, and the data were compared with existing data on intratumoral lymphocyte subsets and PD-L1 expression. The cohort included 1,826 patients that underwent radical cystectomy for muscle-invasive disease (pT2-4). 9p21 deletion was homozygous in 364 (21.3%) and heterozygous in 334 (19.5%) of 1,711 analyzable tumors. The rate of 9p21 deleted tumors increased from pTa G2 low (9.2% homozygous, 25.8% heterozygous) to pTa G2 high (32.6%, 20.9%; p<0.0001) but was slightly lower in pTa G3 (16.7% each). In pT2-pT4 carcinomas, 9p21 deletions were homozygous in 23.3% and heterozygous in 17.9%. Within muscle-invasive cancers, 9p21 deletions were tied to high pT (p=0.0014) and poor overall survival (p=0.0461). MTAP expression loss was strongly linked to homozygous 9p21 deletions. Complete absence of MTAP staining was seen in 96.1% of homozygous deleted cancers while only 4 of 249 MTAP negative cancers had retained at least one 9p21 copy (p<0.0001). Accordingly, absence of MTAP staining was also linked to advanced pT status and poor overall survival (p<0.05 each). Tumors with heterozygous 9p21 deletion did often show preserved but low-level expression of MTAP. 9p21 deletions were associated with low numbers of PD-L1 positive tumor cells (p<0.0001), CD8 (p=0.01) and CD4 positive lymphocytes (p=0.009), M2-macrophages (p<0.0001), and dendritic cells (p=0.0007). A similar tendency was observed for MTAP expression loss, but the level of significance was only reached for PD-L1 positive tumor cells (p<0.0001), M2 macrophages (p=0.001) and dendritic cells (p=0.012). Complete MTAP expression loss is common in urinary bladder cancer and strongly tied to homozygous 9p21 loss, aggressive disease, and non-inflamed microenvironment. Drugs targeting MTAP-deficiency may be highly useful in bladder cancer. MTAP IHC is an excellent surrogate for the detection of MTAP deficiency in this tumor entity. Citation Format: Natalia Gorbokon, Niklas Wößner, Viktoria Ahlburg, Simon Schallenberg, Henning Plage, Sebastian Hofbauer, Kira Furlano, Sarah Weinberger, Paul G. Bruch, Florian Roßner, Sefer Elezkurtaj, Maximilian Lennartz, Niclas C. Blessin, Andreas H. Marx, Henrik Samtleben, Margit Fisch, Michael Rink, Marcin Slojewski, Krystian Kaczmarek, Thorsten Ecke, Steffen Hallmann, Stefan Koch, Nico Adamini, Sarah Minner, Ronald Simon, Guido Sauter, Henrik Zecha, David Horst, Tobias Klatte, Thorsten Schlomm, Martina Kluth. Loss of MTAP expression is strongly linked to homozygous 9p21 deletion, unfavorable tumor phenotype and non-inflamed microenvironment in urothelial bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1048.

Abstract 1046: Prevalence of MTAP deficiencyin human cancer: A tissue microarray study on 17,078 cancers from 149 different tumor types

Abstract The S-methyl-5′-thioadenosine phosphorylase (MTAP) gene is located at 9p21 and is often co-deleted with CDKN2A. Because homozygous MTAP deletions result in a complete expression loss, MTAP immunohistochemistry (IHC) can be used for detection of homozygous deleted cells. MTAP IHC is of diagnostic utility for the distinction of mesotheliomas (often 9p21 deleted) from benign mesothelial proliferations. Moreover, evidence is emerging that MTAP deficiency results in a critical vulnerability of cancer cells towards drugs targeting several different pathways that depend on a functional MTAP gene and also causes resistance to immune checkpoint inhibitors. To determine the prevalence of complete MTAP expression loss and to assess the diagnostic utility of MTAP IHC, a tissue microarray containing 17,078 samples from 149 different tumor entities and 608 samples of 76 different normal tissue types was analyzed by IHC. All cases with complete MTAP loss were validated by fluorescence in situ hybridization (FISH). In normal tissues, MTAP was ubiquitously expressed resulting in a cytoplasmic and nuclear MTAP staining. At least one case with a complete MTAP expression loss was observed in 87 of 149 (58%) tumor categories. MTAP staining was most commonly lost in neuroendocrine neoplasms of various sites (up to 80%), Hodgkin’s lymphoma (38%), mesothelioma (24-30%), bilio-pancreatic adenocarcinomas (9-36%), urothelial neoplasms (19-29%), malignant melanoma (14-21%), mucinous carcinoma of the ovary (27%), squamous cell carcinomas of various organs of origin (up to 24%), various types of sarcomas (up to 20%), adenocarcinoma of the lung (11%), gastro-esophageal adenocarcinomas (2.6-11%), and in various types of non-Hodgkin’s lymphomas (up to 14%). FISH validation identified homozygous 9p21 deletions in 90-98% of cases with MTAP expression loss in most tumor categories including urothelial neoplasms, mesotheliomas, and pancreatic cancers, and others. There were, however, also tumor types such as neuroendocrine tumors and Hodgkin’s lymphomas that always lacked 9p21 deletions. In summary, our data provide a comprehensive overview on MTAP expression in cancer and show a strong link between MTAP expression loss and homozygous 9p21 deletions in most tumor entities. These cancers might most benefit from cancer drugs targeting MTAP deficiency. The absence of 9p21 deletions in other entities with frequent MTAP expression loss demonstrates that other mechanisms can cause significant MTAP downregulation. Whether these tumors benefit from targeting MTAT deficiency remains to be determined. Citation Format: Natalia Gorbokon, Maximilian Lennartz, Doris Hoeflmayer, Sebastian Dwertmann Rico, Simon Kind, Viktor Reiswich, Florian Viehweger, Florian Lutz, Christoph Fraune, Andreas M. Luebke, Claudia Hube-Magg, Franziska Büscheck, Anne Menz, Ria Schlichter, Till Krech, Andrea Hinsch, Eike Burandt, Guido Sauter, Ronald Simon, Stefan Steurer, Andreas H. Marx, Patrick Lebok, David Dum, Sarah Minner, Frank Jacobsen, Till S. Clauditz, Christian Bernreuther, Martina Kluth. Prevalence of MTAP deficiencyin human cancer: A tissue microarray study on 17,078 cancers from 149 different tumor types [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1046.

Lipid-Restricted Culture Media Reveal Unexpected Cancer Cell Sensitivities.

Cancer cell culture models frequently rely on fetal bovine serum as a source of protein and lipid factors that support cell survival and proliferation; however, serum-containing media imperfectly mimic the in vivo cancer environment. Recent studies suggest that typical serum-containing cell culture conditions can mask cancer dependencies, for example, on cholesterol biosynthesis enzymes, that exist in vivo and emerge when cells are cultured in media that provide more realistic levels of lipids. Here, we describe a high-throughput screen that identified fenretinide and ivermectin as small molecules whose cytotoxicity is greatly enhanced in lipid-restricted media formulations. The mechanism of action studies indicates that ivermectin-induced cell death involves oxidative stress, while fenretinide likely targets delta 4-desaturase, sphingolipid 1, a lipid desaturase necessary for ceramide synthesis, to induce cell death. Notably, both fenretinide and ivermectin have previously demonstrated in vivo anticancer efficacy despite their low cytotoxicity under typical cell culture conditions. These studies suggest ceramide synthesis as a targetable vulnerability of cancer cells cultured under lipid-restricted conditions and reveal a general screening strategy for identifying additional cancer dependencies masked by the superabundance of medium lipids.

Hacking the Lipidome: New Ferroptosis Strategies in Cancer Therapy.

The concept of redirecting metabolic pathways in cancer cells for therapeutic purposes has become a prominent theme in recent research. Now, with the advent of ferroptosis, a new chink in the armor has evolved that allows for repurposing of ferroptosis-sensitive lipids in order to trigger cell death. This review presents the historical context of lipidomic and metabolic alterations in cancer cells associated with ferroptosis sensitization. The main proferroptotic genes and pathways are identified as therapeutic targets for increasing susceptibility to ferroptosis. In this review, a particular emphasis is given to pathways in cancer cells such as de novo lipogenesis, which has been described as a potential target for ferroptosis sensitization. Additionally, we propose a connection between ketolysis inhibition and sensitivity to ferroptosis as a new vulnerability in cancer cells. The main proferroptotic genes and pathways have been identified as therapeutic targets for increasing susceptibility to ferroptosis. Proferroptotic metabolic pathways and vulnerable points, along with suggested agonists or antagonists, are also discussed. Finally, general therapeutic strategies for ferroptosis sensitization based on the manipulation of the lipidome in ferroptosis-resistant cancer cell lines are proposed.

Involvement of ferroptosis‐defensive xCT/GPX4 axis in radioresistance and its impacts on prognosis in oral squamous cell carcinoma

AbstractAimRadiotherapy, the mainstay treatment for patients with advanced oral squamous cell carcinoma (OSCC), has low clinical efficacy, resulting in poor prognosis. Radiation induces ferroptosis, a form of cell death driven by iron‐dependent lipid peroxidation. Since the xCT/glutathione peroxidase 4 (GPX4) axis is predominantly involved in the ferroptosis defense system, targeting this axis may potentiate cancer cell vulnerability to ferroptosis.MethodsWe examined the expression of xCT and GPX4 in the tumor cells of biopsy specimens using immunohistochemistry and evaluated the radiation‐mediated antitumor effects of the ferroptosis inducers, erastin and RSL3, that act by inhibiting xCT and GPX4, respectively.ResultsUnivariate analysis revealed that high immunohistochemical expression of xCT was correlated with shorter survival, and high GPX4 expression was an independent poor prognostic factor, indicating that the xCT/GPX4 axis influences the clinical outcome of OSCC. Analyses using two types of OSCC cell lines revealed that the clonogenic survival of irradiated cells was increased by the ferroptosis inhibitor ferrostatin‐1 and decreased by erastin and RSL3. The enhanced antitumor effects of erastin and RSL3 were accompanied by increased lipid peroxidation, which was suppressed by the iron chelator deferoxamine. Erastin and RSL3 enhance the effects of radiation on OSCC cells in a mouse xenograft model; these effects were associated with increased expression of the lipid peroxidation marker 4‐hydroxynonenal in tumor cells.ConclusionsxCT/GPX4 axis is involved in the tumor resistance against radiation through the inhibition of ferroptosis in OSCC. Furthermore, radiotherapy combined with ferroptosis induction by targeting the xCT/GPX4 axis may improve patient prognosis in advanced OSCC.

Unlocking the Potential of Therapy-Induced Cytokine Responses: Illuminating New Pathways in Cancer Precision Medicine.

Precision cancer medicine primarily aims to identify individual patient genomic variations and exploit vulnerabilities in cancer cells to select suitable patients for specific drugs. These genomic features are commonly determined by gene sequencing prior to therapy, to identify individuals who would be most responsive. This precision approach in cancer therapeutics remains a powerful tool that benefits a smaller pool of patients, sparing others from unnecessary treatments. A limitation of this approach is that proteins, not genes, are the ultimate effectors of biological functions, and therefore the targets of therapeutics. An additional dimension in precision medicine that considers an individual's cytokine response to cancer therapeutics is proposed. Cytokine responses to therapy are multifactorial and vary among individuals. Thus, precision is dictated by the nature and magnitude of cytokine responses in the tumor microenvironment exposed to therapy. This review highlights cytokine responses as modules for precision medicine in cancer therapy, including potential challenges. For solid tumors, both detectability of cytokines in tissue fluids and their being amenable to routine sensitive analyses could address the difficulty of specimen collection for diagnosis and monitoring. Therefore, in precision cancer medicine, cytokines offer rational targets that can be utilized to enhance the efficacy of cancer therapy.

Tumor acidosis-induced DNA damage response and tetraploidy enhance sensitivity to ATM and ATR inhibitors

Tumor acidosis is associated with increased invasiveness and drug resistance. Here, we take an unbiased approach to identify vulnerabilities of acid-exposed cancer cells by combining pH-dependent flow cytometry cell sorting from 3D colorectal tumor spheroids and transcriptomic profiling. Besides metabolic rewiring, we identify an increase in tetraploid cell frequency and DNA damage response as consistent hallmarks of acid-exposed cancer cells, supported by the activation of ATM and ATR signaling pathways. We find that regardless of the cell replication error status, both ATM and ATR inhibitors exert preferential growth inhibitory effects on acid-exposed cancer cells. The efficacy of a combination of these drugs with 5-FU is further documented in 3D spheroids as well as in patient-derived colorectal tumor organoids. These data position tumor acidosis as a revelator of the therapeutic potential of DNA repair blockers and as an attractive clinical biomarker to predict the response to a combination with chemotherapy.

Genome-wide loss-of-function genetic screen identifies INSIG2 as the vulnerability of hepatitis B virus-integrated hepatoma cells.

There are approximately 250 million people chronically infected with hepatitis B virus (HBV) worldwide. Although HBV is often integrated into the host genome and promotes hepatocarcinogenesis, vulnerability of HBV integration in liver cancer cells has not been clarified. The aim of our study is to identify vulnerability factors for HBV-associated hepatocarcinoma. Loss-of-function screening was undertaken in HepG2 and HBV-integrated HepG2.2.15 cells expressing SpCas9 using a pooled genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) library. Genes whose guide RNA (gRNA) abundance significantly decreased in HepG2.2.15 cells but not in HepG2 cells were extracted using the MAGeCK algorithm. We identified four genes (BCL2L1, VPS37A, INSIG2, and CFLAR) that showed significant reductions of gRNA abundance and thus potentially involved in the vulnerability of HBV-integrated cancer cells. Among them, siRNA-mediated mRNA inhibition or CRISPR-mediated genetic deletion of INSIG2 significantly impaired cell proliferation in HepG2.2.15 cells but not in HepG2 cells. Its inhibitory effect was alleviated by cotransfection of siRNAs targeting HBV. INSIG2 inhibition suppressed the pathways related to cell cycle and DNA replication, downregulated cyclin-dependent kinase 2 (CDK2) levels, and delayed the G1 -to-S transition in HepG2.2.15 cells. CDK2 inhibitor suppressed cell cycle progression in HepG2.2.15 cells and INSIG2 inhibition did not suppress cell proliferation in the presence of CDK2 inhibitor. In conclusion, INSIG2 inhibition induced cell cycle arrest in HBV-integrated hepatoma cells in a CDK2-dependent manner, and thus INSIG2 might be a vulnerability factor for HBV-associated liver cancer.

Integrative modeling uncovers p21-driven drug resistance and prioritizes therapies for PIK3CA-mutant breast cancer

Utility of PI3Kα inhibitors like BYL719 is limited by the acquisition of genetic and non-genetic mechanisms of resistance which cause disease recurrence. Several combination therapies based on PI3K inhibition have been proposed, but a way to systematically prioritize them for breast cancer treatment is still missing. By integrating published and in-house studies, we have developed in silico models that quantitatively capture dynamics of PI3K signaling at the network-level under a BYL719-sensitive versus BYL719 resistant-cell state. Computational predictions show that signal rewiring to alternative components of the PI3K pathway promote resistance to BYL719 and identify PDK1 as the most effective co-target with PI3Kα rescuing sensitivity of resistant cells to BYL719. To explore whether PI3K pathway-independent mechanisms further contribute to BYL719 resistance, we performed phosphoproteomics and found that selection of high levels of the cell cycle regulator p21 unexpectedly promoted drug resistance in T47D cells. Functionally, high p21 levels favored repair of BYL719-induced DNA damage and bypass of the associated cellular senescence. Importantly, targeted inhibition of the check-point inhibitor CHK1 with MK-8776 effectively caused death of p21-high T47D cells, thus establishing a new vulnerability of BYL719-resistant breast cancer cells. Together, our integrated studies uncover hidden molecular mediators causing resistance to PI3Kα inhibition and provide a framework to prioritize combination therapies for PI3K-mutant breast cancer.

Green Tea Leaves and Rosemary Extracts Selectively Induce Cell Death in Triple-Negative Breast Cancer Cells and Cancer Stem Cells and Enhance the Efficacy of Common Chemotherapeutics.

While incredible medical advancements in chemotherapeutics development for cancer treatment have been made, the majority of these are not selective in their mechanism of action, leading to adverse effects. Given the systemic toxicity associated with these therapies, they are not well suited for long-term use. Natural health products, or NHPs, may provide a way to selectively target the oxidative and metabolic vulnerabilities in cancer cells. White tea (Camelia sinensis) and rosemary (Salvia rosmarinus) are two natural extracts that have been studied extensively for their medicinal properties. However, their anticancer activity and mechanism of action are yet to be fully elucidated. We have examined the extracts' cancer cell-killing ability as well as their interactions with common chemotherapeutics in MDA-MB-231 cells, a triple-negative breast cancer cell line, in vitro. Cell death measurement, morphological and biochemical characterization of apoptotic cell death, mechanisms of action (mitochondrial depolarization and oxidative stress), and immunofluorescence assays to estimate the percentage of cancer stem cells (CSCs) were performed following treatment with Synthite tea extract (STE) and rosemary extract (RE), provided by Synthite Industries Limited alone and in combination with cisplatin and paclitaxel. The key findings in this study are that STE and RE alone demonstrated very efficient anticancer activity against TNBC, and more importantly, the administration of the extracts in conjunction with cisplatin and paclitaxel sensitizes cancer cells to achieve enhanced cell death. In addition, CSCs were found to be sensitive to treatment with STE alone and in combination with RE and exhibited greater sensitivity to combination therapies compared to chemotherapeutic alone. The significance of these observations is that STE and RE, well-tolerated NHPs, have the potential to enhance the efficacy of current chemotherapeutics when combined, as well as prevent relapse for TNBC.

Dual Inhibition of CDK4/6 and XPO1 Induces Senescence With Acquired Vulnerability to CRBN-Based PROTAC Drugs

Background and aimsDespite the increasing number of treatment options available for liver cancer, only a small proportion of patients achieve long-term clinical benefits. Herein, we aim to develop new therapeutic approaches for liver cancer. MethodsA compound screen was conducted to identify inhibitors that could synergistically induce senescence when combined with CDK4/6 inhibitor. The combination effects of CDK4/6 inhibitor and XPO1 inhibitor on cellular senescence were investigated in a panel of human liver cancer cell lines and multiple liver cancer models. A senolytic-drug screen was performed to identify drugs that selectively killed senescent liver cancer cells. ResultsThe combination of CDK4/6 inhibitor and XPO1 inhibitor synergistically induces senescence of liver cancer cells in vitro and in vivo. The XPO1 inhibitor acts by causing accumulation of RB1 in the nucleus, leading to decreased E2F signaling and promoting senescence induction by the CDK4/6 inhibitor. Through a senolytic-drug screen, CRBN-based PROTAC ARV-825 was identified as an agent that can selectively kill senescent liver cancer cells. Upregulation of CRBN was a vulnerability of senescent liver cancer cells, making them sensitive to CRBN-based PROTAC drugs. Mechanistically, we find that USP2 directly interacts with CRBN, leading to the deubiquitination and stabilization of CRBN in senescent liver cancer cells. ConclusionOur study demonstrates a striking synergy in senescence induction of liver cancer cells through the combination of CDK4/6 inhibitor and XPO1 inhibitor. These findings also shed light on the molecular processes underlying the vulnerability of senescent liver cancer cells to CRBN-based PROTAC therapy.

Discovery and Mechanistic Elucidation of NQO1‐Bioactivatable Small Molecules That Overcome Resistance to Degraders

AbstractDegraders hold the promise to efficiently inactivate previously intractable disease‐relevant targets. Unlike traditional inhibitors, degraders act substoichiometrically and rely on the hijacked proteolysis machinery, which can also act as an entry point for resistance. To fully harness the potential of targeted protein degradation, it is crucial to comprehend resistance mechanisms and formulate effective strategies to overcome them. We conducted a chemical screening to identify synthetic lethal vulnerabilities of cancer cells that exhibit widespread resistance to degraders. Comparative profiling followed by tailored optimization delivered the small molecule RBS‐10, which shows preferential cytotoxicity against cells pan‐resistant to degraders. Multiomics deconvolution of the mechanism of action revealed that RBS‐10 acts as a prodrug bioactivated by the oxidoreductase enzyme NQO1, which is highly overexpressed in our resistance models. Collectively, our work informs on NQO1 as an actionable vulnerability to overcome resistance to degraders and as a biomarker to selectively exploit bioactivatable prodrugs in cancer.

Discovery and Mechanistic Elucidation of NQO1-Bioactivatable Small Molecules That Overcome Resistance to Degraders.

Degraders hold the promise to efficiently inactivate previously intractable disease-relevant targets. Unlike traditional inhibitors, degraders act substoichiometrically and rely on the hijacked proteolysis machinery, which can also act as an entry point for resistance. To fully harness the potential of targeted protein degradation, it is crucial to comprehend resistance mechanisms and formulate effective strategies to overcome them. We conducted a chemical screening to identify synthetic lethal vulnerabilities of cancer cells that exhibit widespread resistance to degraders. Comparative profiling followed by tailored optimization delivered the small molecule RBS-10, which shows preferential cytotoxicity against cells pan-resistant to degraders. Multiomics deconvolution of the mechanism of action revealed that RBS-10 acts as a prodrug bioactivated by the oxidoreductase enzyme NQO1, which is highly overexpressed in our resistance models. Collectively, our work informs on NQO1 as an actionable vulnerability to overcome resistance to degraders and as a biomarker to selectively exploit bioactivatable prodrugs in cancer.

Abstract B081: SOAT1 as a targetable KRAS dependency in PDAC

Abstract Metabolic rewiring is an emerging hallmark of neoplasia. In pancreatic ductal adenocarcinoma (PDAC), KRAS alters myriad metabolic programs to promote cellular transformation. Among them, the cholesterol synthesis pathway has emerged as a vulnerability of cancer cells due to the importance of cholesterol in membrane fluidity and the production of isoprenoid intermediates that enable KRAS membrane localization and activation in pancreatic cancer. We recently reported that the non-essential gene SOAT1 (Sterol-O-Acyl transferase 1), encoding an enzyme that esterifies free cholesterol into an insoluble form for storage and transport, is markedly upregulated in metastatic PDAC cells. SOAT1 promotes the hyperactivation of the mevalonate synthesis pathway due to loss of negative feedback by free cholesterol, thereby leading to increased production of isoprenoids such as farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), which are required for RAS and RHO membrane localization and activity, respectively. Genetic ablation of Soat1 reduced RAS and RHO membrane localization and inhibited cellular proliferation and mitochondrial function in vitro, and these effects were largely rescued by exogenous FPP and GGPP. Therefore, our study nominated SOAT1 as a new candidate gene for therapeutic targeting. Based on SuFEx Click Chemistry (ASCC) technology, we have designed and synthesized a panel of drug-like candidates. The first series of Soat1 probes selectively impair the proliferation of PDAC cells that express SOAT1, reduce SOAT1 protein content in cells, and covalently bind to SOAT1. In mice, the most active SOAT1 probes were tolerated in a 28-day daily dosing study up to 120 mg/kg. Marked tumor growth inhibition was noted in mice bearing PDAC xenografts and GEMM mice treated as monotherapy with 15 mg/kg/d of the most active SOAT1 probe, and tissue analysis demonstrated tumor necrosis, decreased proliferation, and increased apoptosis. Mechanistically, SOAT1 loss or inhibition targets multiple important components of cellular transformation in PDAC including KRAS, RHO, and mitochondrial biology, and our work suggests that it is an attractive target to pursue for further drug development in this cancer. Citation Format: Wenjun Lan, Shoujun Sun, Jeremy Nigri, Josh Homer, Young Park, Astrid Deschenes, Paolo Cifani, Justin Cross, Victoria Gaeth, Sunny Kim, Shawn Ting, Rachel Rubino, John Moses, David Tuveson. SOAT1 as a targetable KRAS dependency in PDAC [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B081.

Akt enhances the vulnerability of cancer cells to VCP/p97 inhibition-mediated paraptosis

Valosin-containing protein (VCP)/p97, an AAA+ ATPase critical for maintaining proteostasis, emerges as a promising target for cancer therapy. This study reveals that targeting VCP selectively eliminates breast cancer cells while sparing non-transformed cells by inducing paraptosis, a non-apoptotic cell death mechanism characterized by endoplasmic reticulum and mitochondria dilation. Intriguingly, oncogenic HRas sensitizes non-transformed cells to VCP inhibition-mediated paraptosis. The susceptibility of cancer cells to VCP inhibition is attributed to the non-attenuation and recovery of protein synthesis under proteotoxic stress. Mechanistically, mTORC2/Akt activation and eIF3d-dependent translation contribute to translational rebound and amplification of proteotoxic stress. Furthermore, the ATF4/DDIT4 axis augments VCP inhibition-mediated paraptosis by activating Akt. Given that hyperactive Akt counteracts chemotherapeutic-induced apoptosis, VCP inhibition presents a promising therapeutic avenue to exploit Akt-associated vulnerabilities in cancer cells by triggering paraptosis while safeguarding normal cells.

Interpreting and integrating genomic tests results in clinical cancer care: Overview and practical guidance.

The last decade has seen rapid progress in the use of genomic tests, including gene panels, whole-exome sequencing, and whole-genome sequencing, in research and clinical cancer care. These advances have created expansive opportunities to characterize the molecular attributes of cancer, revealing a subset of cancer-associated aberrations called driver mutations. The identification of these driver mutations can unearth vulnerabilities of cancer cells to targeted therapeutics, which has led to the development and approval of novel diagnostics and personalized interventions in various malignancies. The applications of this modern approach, often referred to as precision oncology or precision cancer medicine, are already becoming a staple in cancer care and will expand exponentially over the coming years. Although genomic tests can lead to better outcomes by informing cancer risk, prognosis, and therapeutic selection, they remain underutilized in routine cancer care. A contributing factor is a lack of understanding of their clinical utility and the difficulty of results interpretation by the broad oncology community. Practical guidelines on how to interpret and integrate genomic information in the clinical setting, addressed to clinicians without expertise in cancer genomics, are currently limited. Building upon the genomic foundations of cancer and the concept of precision oncology, the authors have developed practical guidance to aid the interpretation of genomic test results that help inform clinical decision making for patients with cancer. They also discuss the challenges that prevent the wider implementation of precision oncology.

Ferroptosis and circular RNAs: new horizons in cancer therapy.

Cancer poses intricate challenges to treatment due to its complexity and diversity. Ferroptosis and circular RNAs (circRNAs) are emerging as innovative therapeutic avenues amid the evolving landscape of cancer therapy. Extensive investigations into circRNAs reveal their diverse roles, ranging from molecular regulators to pivotal influencers of ferroptosis in cancer cell lines. The results underscore the significance of circRNAs in modulating molecular pathways that impact crucial aspects of cancer development, including cell survival, proliferation, and metastasis. A detailed analysis delineates these pathways, shedding light on the molecular mechanisms through which circRNAs influence ferroptosis. Building upon recent experimental findings, the study evaluates the therapeutic potential of targeting circRNAs to induce ferroptosis. By identifying specific circRNAs associated with the etiology of cancer, this analysis paves the way for the development of targeted therapeutics that exploit vulnerabilities in cancer cells. This review consolidates the existing understanding of ferroptosis and circRNAs, emphasizing their role in cancer therapy and providing impetus for ongoing research in this dynamic field. See also the graphical abstract(Fig. 1).

Harnessing glucose metabolism with nanomedicine for cancer treatment.

The significance of metabolic processes in cancer biology has garnered substantial attention, as they are essential for meeting the anabolic demands and maintaining the redox balance of rapidly dividing cancer cells. A distinctive feature of tumors is that cancer cells, unlike normal cells, exhibit an increased rate of glucose metabolism. They predominantly relying on aerobic glycolysis to metabolize glucose, which enables these cells to supply energy and produce the necessary building blocks for growth. Targeting glucose metabolism has led to the development of various cancer treatments. However, these agents often have limited efficacy due to factors such as poor stability and solubility, rapid clearance and an insufficient amount of the drug reaching the target site. These limitations can be overcome by preparing nano dosage forms through nanotechnology, which leverages the unique properties of nanomaterials to deliver drugs more precisely to target tissues with controlled release. In this review, we provide a comprehensive overview of the latest advancements in nanomedicine, focusing on the modulation of glucose metabolism in cancer cells. We discuss the design and application of various strategies that have been engineered to target the metabolic hallmarks of cancer. These nanomedicine strategies aim to exploit the metabolic vulnerabilities of cancer cells, thereby offering novel approaches to cancer therapy. The review highlights the innovative nanomaterials and their potential to deliver therapeutic agents more effectively, as well as the challenges and considerations in translating these nanomedicines from bench to bedside. By targeting the glucose metabolism of cancer cells, these nanoscale interventions hold promise for improving treatment outcomes and potentially overcoming the resistance that often plagues conventional cancer therapies.

The Role of the AT-Rich Interaction Domain 1A Gene (ARID1A) in Human Carcinogenesis.

The switch/sucrose non-fermentable (SWI/SNF) (SWI/SNF) complex uses energy from ATP hydrolysis to mobilise nucleosomes on chromatin. Components of SWI/SNF are mutated in 20% of all human cancers, of which mutations in AT-rich binding domain protein 1A (ARID1A) are the most common. ARID1A is mutated in nearly half of ovarian clear cell carcinoma and around one-third of endometrial and ovarian carcinomas of the endometrioid type. This review will examine in detail the molecular functions of ARID1A, including its role in cell cycle control, enhancer regulation, and the prevention of telomerase activity. ARID1A has key roles in the maintenance of genomic integrity, including DNA double-stranded break repair, DNA decatenation, integrity of the cohesin complex, and reduction in replication stress, and is also involved in mismatch repair. The role of ARID1A loss in the pathogenesis of some of the most common human cancers is discussed, with a particular emphasis on gynaecological cancers. Finally, several promising synthetic lethal strategies, which exploit the specific vulnerabilities of ARID1A-deficient cancer cells, are briefly mentioned.