Therapeutic Resistance Research Articles

Single-cell sequencing reveals immune features of treatment response to neoadjuvant immunochemotherapy in esophageal squamous cell carcinoma

Neoadjuvant immunochemotherapy (nICT) has dramatically changed the treatment landscape of operable esophageal squamous cell carcinoma (ESCC), but factors influencing tumor response to nICT are not well understood. Here, using single-cell RNA sequencing paired with T cell receptor sequencing, we profile tissues from ESCC patients accepting nICT treatment and characterize the tumor microenvironment context. CXCL13+CD8+ Tex cells, a subset of exhausted CD8+ T cells, are revealed to highly infiltrate in pre-treatment tumors and show prominent progenitor exhaustion phenotype in post-treatment samples from responders. We validate CXCL13+CD8+ Tex cells as a predictor of improved response to nICT and reveal CXCL13 to potentiate anti-PD-1 efficacy in vivo. Post-treatment tumors from non-responders are enriched for CXCL13+CD8+ Tex cells with notably remarkable exhaustion phenotype and TNFRSF4+CD4+ Tregs with activated immunosuppressive function and a significant clone expansion. Several critical markers for therapeutic resistance are also identified, including LRRC15+ fibroblasts and SPP1+ macrophages, which may recruit Tregs to form an immunosuppressive landscape. Overall, our findings unravel immune features of distinct therapeutic response to nICT treatment, providing a rationale for optimizing individualized neoadjuvant strategy in ESCC.

Local Regulation of Mitochondrial Respiratory for Enhancing Photodynamic Therapy and Breaking Chemoresistance in Hypoxia.

The hypoxic condition in solid tumors induces therapy resistance, limited therapeutic efficacy, and tumor recurrence, especially for chemotherapy and aerobic photodynamic therapy (PDT). To address this matter, an O2 regulator (SNP@Ato) is designed for breaking chemoresistance and enhancing PDT, which is constructed by loading Atovaquone (Ato) through self-assembly and host-guest interaction between β-cyclodextrin functionalized tetraphenylporphyrin (TPP-CD4) and thioketal-linked camptothecin/azobenzene (Azo-TK-CPT). Specifically, the porphyrin units in SNP@Ato are in "Off state" due to the photoinduced electron transfer (PET) effect between the porphyrin units and azobenzene. After encountering the hypoxic condition in solid tumors, SNP@Ato is dissociated by the cleaved azobenzene on account of over-expressed azo-reductase. Then the mitochondrial respiratory of cancer cells would be suppressed with the participation of Ato, generating a local hypoxia relief for sensitized chemotherapy and enhanced PDT. Accompanied by efficient PDT, the TK linker is broken by ROS, and the CPT is released from the prodrugs. Compared with the SNP group without oxygen-regulator, SNP@Ato exhibits a remarkable improvement of the therapeutic effect against hypoxic tumors in vitro and in vivo. This work proposes a novel paradigm for overcoming hypoxia-induced therapeutic resistance.

Insights into CSF-1R Expression in the Tumor Microenvironment.

The colony-stimulating factor 1 receptor (CSF-1R) plays a pivotal role in orchestrating cellular interactions within the tumor microenvironment (TME). Although the CSF-1R has been extensively studied in myeloid cells, the expression of this receptor and its emerging role in other cell types in the TME need to be further analyzed. This review explores the multifaceted functions of the CSF-1R across various TME cellular populations, including tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), dendritic cells (DCs), cancer-associated fibroblasts (CAFs), endothelial cells (ECs), and cancer stem cells (CSCs). The activation of the CSF-1R by its ligands, colony-stimulating factor 1 (CSF-1) and Interleukin-34 (IL-34), regulates TAM polarization towards an immunosuppressive M2 phenotype, promoting tumor progression and immune evasion. Similarly, CSF-1R signaling influences MDSCs to exert immunosuppressive functions, hindering anti-tumor immunity. In DCs, the CSF-1R alters antigen-presenting capabilities, compromising immune surveillance against cancer cells. CSF-1R expression in CAFs and ECs regulates immune modulation, angiogenesis, and immune cell trafficking within the TME, fostering a pro-tumorigenic milieu. Notably, the CSF-1R in CSCs contributes to tumor aggressiveness and therapeutic resistance through interactions with TAMs and the modulation of stemness features. Understanding the diverse roles of the CSF-1R in the TME underscores its potential as a therapeutic target for cancer treatment, aiming at disrupting pro-tumorigenic cellular crosstalk and enhancing anti-tumor immune responses.

KINOME-WIDE SYNTHETIC LETHAL SCREEN IDENTIfiES PANK4 AS A MODULATOR OF TEMOZOLOMIDE RESISTANCE IN GLIOBLASTOMA

Abstract AIMS Temozolomide (TMZ) represents the cornerstone of glioblastoma (GBM) therapy. However, acquisition of resistance limits its therapeutic potential. The human kinome is an undisputable source of druggable targets, still, current knowledge remains confined to a limited fraction of it, with a multitude of under-investigated proteins yet to be characterised. We aimed to uncover synthetic lethal partners of TMZ in GBM that could enhance the effect of TMZ, thus improving TMZ therapy response. METHOD A kinome-wide RNAi screen was performed in a TMZ-resistant GBM cell model. A panel of several TMZ-resistant and patient-derived GBM cell lines was implemented for in vitro validation of our findings through several phenotypic assays. In vivo TMZ-resistant GBM xenografts and immunohistochemical (IHC) analysis of IDH- wildtype GBM specimens were employed to assess the clinical relevance of our findings. Tandem Mass Tag (TMT)-based quantitative proteomic studies were undertaken to elucidate the underlying mechanisms. RESULTS Following a kinome-wide RNAi screen, pantothenate kinase 4 (PANK4) was uncovered as a modulator of TMZ resistance in GBM. Validation of PANK4 across various TMZ-resistant GBM cell models, patient-derived GBM cell lines, tissue samples, as well as in vivo studies, corroborated the potential translational significance of these findings. Moreover, PANK4 expression is induced during TMZ treatment, and its expression is associated with a worse clinical outcome. A Tandem Mass Tag (TMT)-based quantitative proteomic approach revealed that PANK4 abrogation leads to a significant downregulation of numerous proteins with central roles in cellular detoxification and cellular response to oxidative stress. Mechanistically, as cells undergo genotoxic stress during TMZ exposure, PANK4 depletion represents a crucial event that can lead to accumulation of intracellular reactive oxygen species (ROS) and subsequent cell death. CONCLUSION Our study provides novel insights into chemoresistance in GBM and unveils a previously unreported role for PANK4 in mediating therapeutic resistance to TMZ in GBM.

Polyploid cancer cells reveal signatures of chemotherapy resistance.

Therapeutic resistance in cancer significantly contributes to mortality, with many patients eventually experiencing recurrence after initial treatment responses. Recent studies have identified therapy-resistant large polyploid cancer cells in patient tissues, particularly in late-stage prostate cancer, linking them to advanced disease and relapse. Here, we analyzed bone marrow aspirates from 44 advanced prostate cancer patients and found the presence of CTC-IGC was significantly associated with poorer progression-free survival. Single cell copy number profiling of CTC-IGC displayed clonal origins with typical CTCs, suggesting complete polyploidization. Induced polyploid cancer cells from PC3 and MDA-MB-231 cell lines treated with docetaxel or cisplatin were examined through single cell DNA sequencing, RNA sequencing, and protein immunofluorescence. Novel RNA and protein markers, including HOMER1, TNFRSF9, and LRP1, were identified as linked to chemotherapy resistance. These markers were also present in a subset of patient CTCs and associated with recurrence in public gene expression data. This study highlights the prognostic significance of large polyploid tumor cells, their role in chemotherapy resistance, and their expression of markers tied to cancer relapse, offering new potential avenues for therapeutic development.

Interleukin-1 Receptor-Associated Kinase 1 in Cancer Metastasis and Therapeutic Resistance: Mechanistic Insights and Translational Advances.

Interleukin-1 Receptor Associated Kinase 1 (IRAK1) is a serine/threonine kinase that plays a critical role as a signaling transducer of the activated Toll-like receptor (TLR)/Interleukin-1 receptor (IL-1R) signaling pathway in both immune cells and cancer cells. Upon hyperphosphorylation by IRAK4, IRAK1 forms a complex with TRAF6, which results in the eventual activation of the NF-κB and MAPK pathways. IRAK1 can translocate to the nucleus where it phosphorylates STAT3 transcription factor, leading to enhanced IL-10 gene expression. In immune cells, activated IRAK1 coordinates innate immunity against pathogens and mediates inflammatory responses. In cancer cells, IRAK1 is frequently activated, and the activation is linked to the progression and therapeutic resistance of various types of cancers. Consequently, IRAK1 is considered a promising cancer drug target and IRAK1 inhibitors have been developed and evaluated preclinically and clinically. This is a comprehensive review that summarizes the roles of IRAK1 in regulating metastasis-related signaling pathways of importance to cancer cell proliferation, cancer stem cells, and dissemination. This review also covers the significance of IRAK1 in mediating cancer resistance to therapy and the underlying molecular mechanisms, including the evasion of apoptosis and maintenance of an inflammatory tumor microenvironment. Finally, we provide timely updates on the development of IRAK1-targeted therapy for human cancers.

From Bench to Bedside: A Team's Approach to Multidisciplinary Strategies to Combat Therapeutic Resistance in Head and Neck Squamous Cell Carcinoma.

Head and neck squamous cell carcinoma (HNSCC) is diagnosed in more than 71,000 patients each year in the United States, with nearly 16,000 associated deaths. One significant hurdle in the treatment of HNSCC is acquired and intrinsic resistance to existing therapeutic agents. Over the past several decades, the University of Wisconsin has formed a multidisciplinary team to move basic scientific discovery along the translational spectrum to impact the lives of HNSCC patients. In this review, we outline key discoveries made throughout the years at the University of Wisconsin to deepen our understanding of therapeutic resistance in HNSCC and how a strong, interdisciplinary team can make significant advances toward improving the lives of these patients by combatting resistance to established therapeutic modalities. We are profoundly grateful to the many scientific teams worldwide whose groundbreaking discoveries, alongside evolving clinical paradigms in head and neck oncology, have been instrumental in making our work possible.

Compressive stresses in cancer: characterization and implications for tumour progression and treatment.

Beyond their many well-established biological aberrations, solid tumours create an abnormal physical microenvironment that fuels cancer progression and confers treatment resistance. Mechanical forces impact tumours across a range of biological sizes and timescales, from rapid events at the molecular level involved in their sensing and transmission, to slower and larger-scale events, including clonal selection, epigenetic changes, cell invasion, metastasis and immune response. Owing to challenges with studying these dynamic stimuli in biological systems, the mechanistic understanding of the effects and pathways triggered by abnormally elevated mechanical forces remains elusive, despite clear correlations with cancer pathophysiology, aggressiveness and therapeutic resistance. In this Review, we examine the emerging and diverse roles of physical forces in solid tumours and provide a comprehensive framework for understanding solid stress mechanobiology. We first review the physiological importance of mechanical forces, especially compressive stresses, and discuss their defining characteristics, biological context and relative magnitudes. We then explain how abnormal compressive stresses emerge in tumours and describe the experimental challenges in investigating these mechanically induced processes. Finally, we discuss the clinical translation of mechanotherapeuticsthat alleviate solid stresses and their potential to synergize with chemotherapy, radiotherapy and immunotherapies.

Strategies to Target Chemoradiotherapy Resistance in Small Cell Lung Cancer.

Background: Small cell lung cancer (SCLC) is a lethal form of lung cancer with few treatment options and a high rate of relapse. While SCLC is initially sensitive to first-line DNA-damaging chemo- and radiotherapy, relapse disease is almost universally therapy-resistant. As a result, there has been interest in understanding the mechanisms of therapeutic resistance in this disease. Conclusions: Progress has been made in elucidating these mechanisms, particularly as they relate to the DNA damage response and SCLC differentiation and transformation, leading to many clinical trials investigating new therapies and combinations. Yet there remain many gaps in our understanding, such as the effect of epigenetics or the tumor microenvironment on treatment response, and no single mechanism has been found to be ubiquitous, suggesting a significant heterogeneity in the mechanisms of acquired resistance. Nevertheless, the advancement of techniques in the laboratory and the clinic will improve our ability to study this disease, especially in patient populations, and identify methods to surmount therapeutic resistance.

Stimulating Soluble Guanylyl Cyclase with the Clinical Agonist Riociguat Restrains the Development and Progression of Castration-Resistant Prostate Cancer.

Castration-resistant prostate cancer (CRPC) is incurable and fatal, making prostate cancer the second-leading cancer-related cause of death for American men. CRPC results from therapeutic resistance to standard-of-care androgen deprivation (AD) treatments, through incompletely understood molecular mechanisms, and lacks durable therapeutic options. Here, we identified enhanced soluble guanylyl cyclase (sGC) signaling as a mechanism that restrains CRPC initiation and growth. Patients with aggressive, fatal CRPC exhibited significantly lower serum levels of the sGC catalytic product cyclic GMP (cGMP) compared to their castration-sensitive stage. In emergent castration-resistant cells isolated from castration-sensitive prostate cancer (CSPC) populations, the obligate sGC heterodimer was repressed via methylation of its beta subunit. Genetically abrogating sGC complex formation in CSPC cells promoted evasion of AD-induced senescence and concomitant castration-resistant tumor growth. In established castration-resistant cells, the sGC complex was present but in a reversibly oxidized and inactive state. Subjecting CRPC cells to AD regenerated the functional complex, and co-treatment with riociguat, an FDA-approved sGC agonist, evoked redox stress-induced apoptosis. Riociguat decreased castration-resistant tumor growth and increased apoptotic markers, with elevated cGMP levels correlating significantly with lower tumor burden. Riociguat treatment reorganized tumor vasculature and eliminated hypoxic tumor niches, decreasing CD44+ tumor progenitor cells and increasing the radiosensitivity of castration-resistant tumors. Thus, this study showed that enhancing sGC activity can inhibit CRPC emergence and progression through tumor cell-intrinsic and extrinsic effects. Riociguat can be repurposed to overcome CRPC, with noninvasive monitoring of cGMP levels as a marker for on-target efficacy.

Characterization of cell states in biliary tract cancers identifies mechanisms of therapeutic resistance in a phase II trial of DKN-01/nivolumab.

Biliary tract cancers demonstrate profound therapeutic resistance, and broadly effective therapies for refractory disease are lacking. We conducted a single-arm, second-line phase II trial combining DKN-01, a humanized monoclonal antibody targeting Dickkopf-1 (DKK-1), and nivolumab to treat patients with advanced biliary tract cancer ( NCT04057365 ). No objective responses were seen. To identify mechanisms of treatment failure, we analyzed paired pre-treatment and on-treatment biopsies using scRNA-seq and constructed a detailed molecular classification of malignant and immune cells. We annotated five biliary tract cancer malignant cell states: classical, basal, mesenchymal, neural-like, and endothelial-like. Neural-like and endothelial-like states, which drive therapeutic resistance in other cancers, have not previously been described in BTC. Malignant cell states co-varied with distinct immune cell states, revealing diverse mechanisms of myeloid and T-cell mediated immune suppression, including M2 myeloid and terminally exhausted T cell programs that were induced by DKN-01/nivolumab. Here, we provide the first systematic classification of functionally annotated cell states in biliary tract cancer and provide new insight into resistance mechanisms to an immunotherapy combination that can inform the next generation of trials.

Bridging early life trauma to difficult-to-treat depression: scoping review.

Accumulating evidence suggests that early life trauma (ELT) initiates and perpetuates a cycle of depression, leading to challenges in management and achieving remission. This scoping review aimed to examine the intricate relationship between ELT and difficult-to-treat depression (DTD). An extensive literature search from 1 January 2013 to 21 October 2023 was conducted using the Cochrane Library, PubMed, Scopus, PsycINFO and OpenGrey. Our review identified scientific literature illustrating the multifaceted link between ELT and DTD, highlighting the dual impact of ELT on therapeutic resistance and clinical complexity. This complexity hampers management of patients with DTD, who are characterised by limited pharmacological responsiveness and heightened relapse risk. While exploring the ELT-DTD nexus, the review revealed a paucity of literature on the impact of ELT within DTD. Findings underscore the profound link between ELT and DTD, which is essential for comprehensive understanding and effective management. Tailoring treatments to address ELT could enhance therapeutic outcomes for patients with DTD. Future studies should use larger samples and well-defined diagnostic criteria and explore varied therapeutic approaches.

EZH2 functional dichotomy in reactive oxygen species-stratified glioblastoma.

EZH2, well-known for its canonical methyltransferase activity in transcriptional repression in many cancers including glioblastoma (GBM), has an understudied non-canonical function critical for sustained tumor growth. Recent GBM consortial efforts reveal complex molecular heterogeneity for which therapeutic vulnerabilities correlated with subtype stratification remain relatively unexplored. Current enzymatic EZH2 inhibitors (EZH2inh) targeting its canonical SET domain show limited efficacy and lack durable response, suggesting that underlying differences in the non-canonical pathway may yield new knowledge. Here, we unveiled dual roles of the EZH2 CXC domain in therapeutically-distinct, reactive oxygen species (ROS)-stratified tumors. We analyzed differentially expressed genes between ROS classes by examining cis-regulatory elements as well as clustering of activities and pathways to identify EZH2 as the key mediator in ROS-stratified cohorts. Pull-down assays and CRISPR knockout of EZH2 domains were used to dissect the distinct functions of EZH2 in ROS-stratified GBM cells. The efficacy of NF-κB-inducing kinase inhibitor (NIKinh) and standard-of-care temozolomide was evaluated using orthotopic patient-derived GBM xenografts. In ROS(+) tumors, CXC-mediated co-interaction with RelB drives constitutive activation of non-canonical NF-κB2 signaling, sustaining the ROS(+) chemoresistant phenotype. In contrast, in ROS(-) subtypes, PRC2 methyltransferase activity represses canonical NF-κB. Addressing the lack of EZH2inh targeting its non-methyltransferase roles, we utilized a brain-penetrant NIKinh that disrupts EZH2-RelB binding, consequently prolonging survival in orthotopic ROS(+)-implanted mice. Our findings highlight the functional dichotomy of the EZH2 CXC domain in governing ROS-stratified therapeutic resistance, thereby advocating for the development of therapeutic approaches targeting its non-canonical activities and underscoring the significance of patient stratification methodologies.

8018 Improving Anti-Breast Cancer Activities by Optimizing Torsion Angle Energies

Abstract Disclosure: D.R. Zak: None. E.C. Fink: None. G.R. Hancock: None. K.S. Young: None. S.W. Fanning: None. Overexpression of estrogen receptor alpha (ER-alpha) is found in 70% of breast cancer tumors. Normally, ER-alpha remains inactive and sequestered in the cytoplasm until estrogen binds to the ligand-binding domain (LBD) to enable nuclear translocation, coregulator recruitment, and subsequent activation of proliferative ER-alpha-dependent transcriptomic profiles. The majority of breast cancers are treated successfully with ER-targeted endocrine therapies, but hotspot ER-alpha LBD mutants are selected for, namely Y537S and D538G causing therapeutic resistance, relapse, and aggressive metastatic disease. The selective estrogen receptor modulator (SERM) lasofoxifene (laso) and selective estrogen receptor degrader (SERD) elacestrant (RAD1901) are chemically distinctive and show great promise in the ER-alpha mutant setting with potent anti-tumor effects and improved side effect profiles compared to the standard-of-care SERD fulvestrant (ICI). To elucidate the structural-transcriptional relationships of these ligands, we created a laso/RAD1901 chemical hybrid T6I-29 that demonstrated both canonical and unexpected therapeutic mechanisms of action. However, it possesses reduced anti-proliferative potency compared to ICI. We hypothesized that minor chemical changes to T6I-29 could improve potency while maintaining its favorable pharmaceutical profiles. To address this hypothesis, we performed quantum mechanical calculations of a series of T6I-derivatives. The addition of a methyl linker within the scaffold core significantly improved the torsion angle energies of the ligand binding pose. Multiple derivatives were synthesized based on these computations. The new compound T6I-B2 exerted profound anti-proliferative effects on breast cancer cells and adopted a unique ligand binding pose within the LBD. This approach shows that T6I-SERM potency can be improved by optimizing ligand torsion angle energies. Presentation: 6/3/2024

LSD1 and CoREST2 Potentiate STAT3 Activity to Promote Enteroendocrine Cell Differentiation in Mucinous Colorectal Cancer.

Neuroendocrine cells have been implicated in therapeutic resistance and worse overall survival in many cancer types. Mucinous colorectal cancer (mCRC) is uniquely enriched for enteroendocrine cells (EECs), the neuroendocrine cell of the normal colon epithelium, as compared to non-mCRC. Therefore, targeting EEC differentiation may have clinical value in mCRC. Here, single cell multi-omics uncovered epigenetic alterations that accompany EEC differentiation, identified STAT3 as a regulator of EEC specification, and discovered a rare cancer-specific cell type with enteric neuron-like characteristics. Furthermore, LSD1 and CoREST2 mediated STAT3 demethylation and enhanced STAT3 chromatin binding. Knockdown of CoREST2 in an orthotopic xenograft mouse model resulted in decreased primary tumor growth and lung metastases. Collectively, these results provide rationale for developing LSD1 inhibitors that target the interaction between LSD1 and STAT3 or CoREST2, which may improve clinical outcomes for patients with mCRC.

Discovery of Oral Degraders of the ROS1 Fusion Protein with Potent Activity against Secondary Resistance Mutations.

The development of therapeutic resistance in the majority of patients limits the long-term benefit of ROS1 inhibitor treatment. On-target mutations of the ROS1 kinase domain confer resistance to crizotinib and lorlatinib in more than one-third of acquired resistance cases with no current effective treatment option. As an alternative to stoichiometric inhibition, proteolytic degradation of ROS1 could provide an effective tool to combat resistance generated by these mutations. Our study has identified a potent, orally active ROS1 degrader with an excellent pharmacokinetics profile. The degrader can effectively inhibit ROS1-dependent cell proliferation and tumor growth by degrading the ROS1 kinase, thereby eliminating the active phospho-ROS1. More importantly, the degradation-based therapeutic modality can overcome on-target mutation resistance to tyrosine kinase inhibitors by efficient degradation of the mutated kinase to achieve greater potency than inhibition.

RPS15 Coordinates with CtIP to Facilitate Homologous Recombination and Confer Therapeutic Resistance in Breast Cancer.

The repair of DNA double-strand breaks (DSBs) through homologous recombination (HR) is vital for maintaining the stability and integrity of the genome. RNA binding proteins (RBPs) intricately regulate the DNA damage repair process, yet the precise molecular mechanisms underlying their function remain incompletely understood. In this study, we highlight the pivotal role of RPS15, a representative RBP, in homologous recombination repair. Specifically, we demonstrate that RPS15 promotes DNA end resection, a crucial step in homologous recombination. Notably, we identify an interaction between RPS15 and CtIP, a key factor in homologous recombination repair. This interaction is essential for CtIP recruitment to DSB sites, subsequent RPA coating, and RAD51 replacement, all critical steps in efficient homologous recombination repair and conferring resistance to genotoxic treatments. Functionally, suppressing RPS15 expression sensitizes cancer cells to X-ray radiation and enhances the therapeutic synergistic effect of PARP1 inhibitors in breast cancer cells. In summary, our findings reveal that RPS15 promotes DNA end resection to ensure effective homologous recombination repair, suggesting its potential as a therapeutic target in cancer treatment.

Prognostic and therapeutic implications of tumor-restrictive type III collagen in the breast cancer microenvironment

Collagen plays a critical role in regulating breast cancer progression and therapeutic resistance. An improved understanding of both the features and drivers of tumor-permissive and -restrictive collagen matrices are critical to improve prognostication and develop more effective therapeutic strategies. In this study, using a combination of in vitro, in vivo and bioinformatic experiments, we show that type III collagen (Col3) plays a tumor-restrictive role in human breast cancer. We demonstrate that Col3-deficient, human fibroblasts produce tumor-permissive collagen matrices that drive cell proliferation and suppress apoptosis in non-invasive and invasive breast cancer cell lines. In human triple-negative breast cancer biopsy samples, we demonstrate elevated deposition of Col3 relative to type I collagen (Col1) in non-invasive compared to invasive regions. Similarly, bioinformatics analysis of over 1000 breast cancer patient biopsies from The Cancer Genome Atlas BRCA cohort revealed that patients with higher Col3:Col1 bulk tumor expression had improved overall, disease-free, and progression-free survival relative to those with higher Col1:Col3 expression. Using an established 3D culture model, we show that Col3 increases spheroid formation and induces the formation of lumen-like structures that resemble non-neoplastic mammary acini. Finally, our in vivo study shows co-injection of murine breast cancer cells (4T1) with rhCol3-supplemented hydrogels limits tumor growth and decreases pulmonary metastatic burden compared to controls. Taken together, these data collectively support a tumor-suppressive role for Col3 in human breast cancer and suggest that strategies that increase Col3 may provide a safe and effective therapeutic modality to limit recurrence in breast cancer patients.

KDM4B Histone Demethylase Inhibition Attenuates Tumorigenicity of Malignant Melanoma Cells by Overriding the p53-Mediated Tumor Suppressor Pathway.

Despite significant advances in the treatment of cutaneous melanoma (hereaftermelanoma), the prognosis remains less favorable due to therapeutic resistance, which is presumably linked to epigenetic dysregulation. We hypothesized that the histone lysine demethylase KDM4B could play a pivotal role in controlling therapy-resistant melanoma. To validate our hypothesis, we retrieved RNA sequencing data from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA)program and observed upregulation of KDM4B in both primary and metastatic melanoma, which was associated with poor survival. To explore its role, we used murine B16, human SK-MEL-5, and G-361 melanoma cells as in vitro models of melanoma. We found that KDM4B inhibition using NCGC00244536 increased global levels of H3K9me3 and downregulated the expressions of cell cycle progression-related genes Cdk1, Cdk4, Ccnb1, and Ccnd1. Moreover, genetic ablation of KDM4B or its chemical inhibition using NCGC00244536 reduced p53 production by upregulating MDM2, which enhances the proteolytic degradation of p53. Interestingly, despite the reduction of p53, these interventions augmented apoptosis and senescence-induced cell death by activating pathways downstream of p53, as evidenced by reduced levels of pro-survival Bcl-2 and Bcl-xL proteins and increased production of pro-apoptotic cleaved caspase-3, caspase-7, Bax, and the senescence inducer Cdkn1a. Compared to the FDA-approved anti-melanoma agent dacarbazine, NCGC00244536 exhibited more pronounced cytotoxic and antiproliferative effects in melanoma cells. Importantly, NCGC00244536 demonstrated minimal cytotoxicity to low Kdm4b-expressing mouse embryonic fibroblasts. In conclusion, our findings suggest that KDM4B inhibition can override the antitumor effect of p53, and potentially serve as a therapeutic strategy for melanoma.

131 (PB119): Novel Androgen Receptor Antagonists with Improved Activity Against Common LBD Variants Associated with Therapeutic Resistance

131 (PB119): Novel Androgen Receptor Antagonists with Improved Activity Against Common LBD Variants Associated with Therapeutic Resistance