Oncology
Splicing factor TRA2B enhances synthesis of androgen receptor variant AR-V7 in prostate cancer cells
Abstract
Treatment of locally advanced and metastatic prostate cancer (PC) with androgen receptor–targeting (AR-targeting) therapies has limited durability, with disease eventually progressing to castrate-resistant PC (CRPC). Constitutively active AR splice variants (AR-Vs), such as AR-V7, play a key role in driving treatment resistance and disease progression. Importantly, the failure to attenuate AR-V function represents a major unmet clinical need, and as such, defining how AR-Vs are generated is likely to yield new therapeutic targets. Our knowledge of factors that mediate splicing of AR-V–encoding mRNAs remains limited. Here, we have employed an RNA-targeting CasRx approach to identify selective protein interactors of AR-V7 mRNA in PC. TRA2B and its ortholog, TRA2A, were identified as splicing regulators of AR transcripts that facilitate AR-V synthesis at the expense of full-length AR isoforms. TRA2B expression correlated with AR-V7 transcript in CRPC and attenuation of TRA2-mediated splicing diminished PC cell growth. Exploiting TRA2B function may therefore provide new therapeutic opportunities in advanced disease.
Authors
Nicholas Brittain, Alec Paschalis, Ryan Nelson, Beth Adamson, Laura Walker, Ruaridh Duncan, Graham R. Smith, Suzanne McGill, Richard J.S. Burchmore, Denisa Bogdan, Juan M. Jiménez-Vacas, Jonathan Welti, Wei Yuan, Craig N. Robson, Pasquale Rescigno, Sara Luzzi, Adam Sharp, Johann de Bono, Luke Gaughan
Abstract
New androgen receptor (AR) pathway inhibitors (ARPIs) in clinical development, including AR degraders and CYP11A inhibitors, largely target ligand-dependent AR activation and have reported antitumor activity in metastatic castration-resistant prostate cancer (mCRPC) resistant to established ARPIs, predominately against tumors with AR mutations. We hypothesized that AR-mutated mCRPC exhibits lower AR splice variant 7 (AR-V7) expression and remains full-length–AR (FL-AR) driven, explaining, in part, the antitumor activity of these AR ligand–binding domain (LBD) targeting drugs. The data herein demonstrate that mCRPC tissue biopsies with detectable AR mutations express significantly lower levels of AR-V7 protein and associate with better overall survival and enhanced sensitivity to ARPIs. This is independent of differences in the total number of global splicing events but may be related to differences in splicing factor expression between AR-mutated and nonmutated mCRPC. In conclusion, AR-mutated mCRPC frequently exhibits low AR-V7 expression, arguably explaining the enhanced sensitivity to ARPIs observed in these cancers. Consequently, AR mutation status may serve as a biomarker to predict response to AR-directed therapies.
Authors
Alec Paschalis, Ines Figueiredo, Denisa Bogdan, Arian Lundberg, Rita Santos, Bora Gurel, Tarek Taha, Ossian Longoria, Ana Ferreira, Claudia Bertan, Nicholas Brittain, Ryan Nelson, Laura Walker, Antje Neeb, Jonathan Welti, Wei Yuan, Costas Mitsopoulos, Stephen R. Plymate, Michael C. Haffner, Adam G. Sowalsky, Suzanne Carreira, Adam Sharp, Luke Gaughan, Johann de Bono
Abstract
BACKGROUND Proliferation is a key biological feature of cancer and in prostate cancer is modulated by androgen receptor (AR) signalling. Cohort studies have suggested that highly proliferative tumors respond poorly to androgen receptor pathway inhibitors (ARPIs). To clarify whether tumor proliferation interacts with treatment benefit from adding abiraterone to androgen deprivation therapy (ADT), we assessed the Ki-67 proliferation index in prostate core biopsies from participants enrolled in the STAMPEDE platform protocol. METHODS Proliferation was assessed by Ki67 immunohistochemistry on tumors from patients randomized in two sequential but non-overlapping (ie no shared controls) phase 3 trials of abiraterone or abiraterone and enzalutamide conducted in STAMPEDE (NCT00268476), with 14-year survival outcomes. A standardised unweighted global assessment method was used. Survival analyses used Cox proportional hazards models adjusted for established prognostic factors. Ki-67 was examined both continuously and dichotomised at the median. Sensitivity analyses excluded samples exposed to ADT. RESULTS Ki-67 was successfully scored on cancers from 1,605 patients. Higher Ki-67 was strongly prognostic for shorter overall survival across disease states. However, in metastatic patients treated with ADT plus abiraterone, the adverse prognostic impact of high Ki-67 was substantially attenuated (aHR=1.06 per 10-percentage-point increase), with a statistically-significant treatment-biomarker interaction (p<0.001) confirming highly proliferative tumors derived greater treatment benefit. No interaction was observed in non-metastatic disease. CONCLUSION Ki-67 is an independent prognostic biomarker in advanced prostate cancer. In metastatic disease, higher proliferation predicts greater sensitivity to abiraterone added to ADT, suggesting a potential biological vulnerability of rapidly cycling tumors to intensified AR pathway blockade. TRIAL REGISTRATION: NCT00268476
Authors
Larissa Mendes, Peter F. Dutey-Magni, Emily Grist, Ashwin Sachdeva, Sara Santos Vidal, Sharanpreet Lall, Marina A. Parry, Claire L. Amos, Nafisah B. Atako, Anna Wingate, Daniel Wetterskog, Matthew R. Sydes, Chris C. Parker, Noel Clarke, Christopher J. Sweeney, Mahesh KB Parmar, Louise C. Brown, Nicholas D. James, Daniel M. Berney, Gerhardt Attard
Abstract
Epigenetic dysregulation is associated with immune evasion and immune checkpoint blockade (ICB) resistance. Here, using in vivo CRISPR-Cas9 screens targeting epigenetic-related factors in mouse tumor models treated with ICB, we identified Chromobox 4 (CBX4) as a key negative regulator of immune tumor microenvironment. Single-cell RNA sequencing and spatial transcriptomics analyses of patients receiving neoadjuvant anti-PD-1 therapy revealed high CBX4 expression in both tumor cells and immunosuppressive tumor-associated macrophage subpopulations, with preferential accumulation in non-responders. Deficiency of CBX4 in macrophages or tumor cells, induced robust anti-tumor immunity, increased infiltration and cytotoxic activity of CD8+ T cells and NK cells, thereby heightening the sensitivity of ICB treatment. Mechanistically, CBX4 targeted H3K9me3 and H3K27me3-marked endogenous retroelements such as RLTR4-Mm-int. Loss of CBX4 derepressed retrotransposons, activating cytosolic RNA-sensing pathways and triggering type I interferon response, ultimately leading to robust inflamed TME. Moreover, we uncovered a negative correlation between CBX4 expression and immune responses, retrotransposon levels as well as the prognosis of patients with hepatocellular carcinoma (HCC) undergoing ICB therapy. Our study establishes CBX4 as an epigenetic immune checkpoint through the epigenetic silencing of retrotransposons, remodeling immune TME and thus providing a promising therapeutic target to enhance tumor immunogenicity and overcoming immunotherapy resistance.
Authors
Zhibo Ma, Wenlong Jia, Xi Zhou, Jing Liu, Qingwen Li, Ruizhi Chang, Shiqi Gu, Naonao Yuan, Zhishui Chen, Peixiang Lan
Abstract
Resistance to HIF-2α inhibitors such as Belzutifan underscores the need to better understand how HIF-2α is transcriptionally regulated in clear cell renal cell carcinoma (ccRCC). Here, we uncover a cytokine-driven enhancer mechanism that sustains HIF-2α expression through the JAK1–STAT3 signaling pathway. Using a genome-wide CRISPR screen in VHL-deficient ccRCC cells, we identified SOCS3 as a key negative regulator of HIF-2α. Mechanistically, loss of SOCS3 activates JAK1–STAT3 signaling, leading to the recruitment of STAT3 to distal enhancers upstream of EPAS1 that physically loop to its promoter to drive HIF-2α transcription. This cytokine–enhancer circuit was recapitulated in ccRCC patient samples and functionally validated using CRISPR interference, which disrupted enhancer–promoter looping and reduced tumor growth in HIF-2α–dependent models. SOCS3 overexpression or pharmacologic inhibition of JAK1/STAT3 markedly suppressed HIF-2α expression and tumor progression both in vitro and in vivo. Unlike prior studies focusing on VHL/HIF occupancy–driven enhancer activation, this work defines a trans-acting cytokine–JAK1–STAT3 pathway that transcriptionally controls EPAS1. Together, these findings reveal a targetable enhancer mechanism that sustains HIF-2α expression and suggest that combined inhibition of JAK1/STAT3 and HIF-2α may overcome therapeutic resistance in kidney cancer.
Authors
Jun Fang, Jeremy M Simon, Tao Wang, Yunpeng Gao, Xianju Bi, Lianxin Hu, Chengheng Liao, Cheng Zhang, Yayoi Adachi, Jin Zhou, Hongyi Liu, Qian Liang, James A. Nathan, Ram Mani, James Brugarolas, Qing Zhang
Abstract
Single-agent anti-PD-1 antibody is ineffective for pancreatic ductal adenocarcinoma (PDAC) due to its immunosuppressive tumor-microenvironment (TME). KRAS-mutations contribute to the inflammatory TME and therapeutic resistance by upregulating IL-8 via MAPK pathways. Thus, this study attempted to overcome the resistance to anti-PD-1 antibody by targeting downstream KRAS-effectors. The study found that the resistance to anti-PD-1 antibody can be overcome through MEK1/2-inhibition. The combination of anti-PD-1 antibody and MEK inhibitor displayed antitumor activity in Krasmut (mutated) KPC mouse tumors, but not KrasWT (wild-type) Panc02 tumors. The combination of anti-PD-1 antibody and MEK inhibitor induced recruitment of tumor-associated neutrophils (TANs) via CXCR2, an IL-8 receptor, and increased memory CD8+ T cells and IFNgamma production in treatment-sensitive tumors. However, larger tumors still resisted to the combination of anti-PD-1 antibody and MEK inhibitor likely due to hypoxia/necrosis-induced NETosis and associated paucity of CD8+ T cells. The subsequent addition of anti-CXCR2 antibody overcame this resistance by blocking TAN-infiltration to hypoxic/necrotic areas. Consistently, a risk-score based on the NETosis-MAPK signaling interaction is significantly associated with poorer survival in human PDACs. This study thus provides a new venue for overcoming resistance to strategies targeting KRAS signaling.
Authors
Brian Herbst, Alex B. Blair, Yiming Li, Elizabeth M. Jaffee, Lei Zheng
Abstract
Glioblastoma (GBM) is a highly aggressive brain tumor characterized by extensive crosstalk between glioblastoma stem cells (GSCs) and immunosuppressive microglia, with our previous work identifying CLOCK and TFPI2 as key regulators of this interaction. Here, we uncover a ‘symbiotic exclusivity’ pattern between CLOCK and TFPI2, showing that despite mutually exclusive amplifications, they sustain symbiotic regulatory interactions in GBM. The CLOCK-BMAL1 complex transcriptionally upregulates TFPI2, while TFPI2-driven hypoxia inducible factor 1 alpha (HIF1a) signaling activates nuclear factor kappa B (NF-kB) P65 to upregulate the CLOCK-BMAL1 complex, creating a positive feedback loop to promote stemness, immunosuppression, and tumor progression. Disrupting the CLOCK-TFPI2 interplay through dual inhibition of their downstream effectors reduces GSC stemness and immunosuppressive microglia, activates antitumor immunity, and synergizes with anti-PD1 therapy to achieve complete tumor regression in 50-62.5% of tumor-bearing mice. This study uncovers a promising therapeutic strategy for a broader subset of GBM patients with high expression of either CLOCK or TFPI2, and provides a framework for identifying 'symbiotic exclusivity' genes in cancer.
Authors
Fei Zhou, Lizhi Pang, Yang Liu, Fatima Khan, Peiwen Chen
Abstract
Gemcitabine-based chemotherapy is the standard treatment regime for advanced intrahepatic cholangiocarcinoma (iCCA), but the frequent presence of chemoresistance limits its efficacy. Here, we identified isocitrate dehydrogenase 1 (IDH1) as the crucial target that confers chemoresistance of iCCA to gemcitabine using a druggable CRISPR/Cas9 library. The positive association between IDH1 expression and chemoresistance was revealed in a gemcitabine-treated iCCA cohort and cell-based drug sensitivity assays. Utilizing patient-derived organoids, cell line-derived xenografts, and patient-derived xenografts, we demonstrated that IDH1 knockdown or IDH1 pharmacological inhibition facilitated gemcitabine efficacy in these pre-clinical iCCA models carrying wild-type IDH1 (wtIDH1). Mechanistically, wtIDH1 oxidizes isocitrate to generate α-ketoglutarate and NADPH, thereby coping with the oxidative stress induced by gemcitabine, maintaining cellular redox homeostasis, and ultimately leading to their chemoresistance to gemcitabine. Significantly, ivosidenib, the FDA-approved allosteric IDH1 inhibitor, demonstrated synergistic anti-tumor efficacy with gemcitabine in wtIDH1 pre-clinical iCCA models through boosting intracellular oxidative stress under physiological conditions. The low level of Mg2+, an ion that competitively hinders binding of ivosidenib on wtIDH1, in iCCA tumor microenvironment contributed to the expanded therapeutic window of ivosidenib in patients with iCCA. Our work revealed the potency of combining targeting IDH1 and chemotherapy against wtIDH1 iCCA and other tumors.
Authors
Xiuxian Li, Zhixiao Song, Shusheng Lin, Man Luo, Shaoru Liu, Yang Liu, Fapeng Zhang, Leibo Xu, Chao Liu, Honghua Zhang
Abstract
PRC2/EZH2 inhibitors (PRC2i/EZH2i) are promising for treatment of advanced cancers including metastatic prostate cancer. Here we show that PRC2i/EZH2i alone or in combination with AR inhibitors induce diverse cell state programs (CSP) (e.g., response to stress or interferon, MYC targets, stem cell, EMT and multiple developmental programs) which led to increased tumor cell invasion, metastasis and resistance to other drugs, in addition to modest suppression of tumor growth. In contrast to the current perception, our comprehensive, integrated genomics and epigenomics profiling of PDX and clinical tumors revealed that PRC2/EZH2 suppresses CSP genes through maintaining chromatin bivalency. Hyperactive Wnt/β-catenin signaling and inhibitors of PRC2/EZH2 and AR alter chromatin bivalency through antagonizing PRC2 and stimulating MLL2/KMT2B in a feedforward manner. Circadian rhythm regulator REV-ERBα unexpectedly reprograms β-catenin in promoting bivalency resolution and CSP gene expression. Dual targeting of Wnt/β-catenin and EZH2 diminishes diverse cell states through restoring bivalency and effectively block tumor growth. Our findings provide unexpected insights of chromatin bivalency and dysregulated circadian rhythm in control of cell state diversity and offer alternative therapeutic strategies targeting PRC2/EZH2 for advanced malignancies.
Authors
Yatian Yang, Xiong Zhang, Varadha Balaji Venkadakrishnan, Hongye Zou, Xingling Zheng, Shiyao Guo, Christopher Z. Chen, Alexander D. Borowsky, Eva Corey, Ronald M. Evans, Allen C. Gao, Marc A. Dall'Era, Amina Zoubeidi, Primo N. Lara, Hsing-Jien Kung, Xinbin Chen, Himisha Beltran, Hong-Wu Chen
Abstract
V-domain immunoglobulin suppressor of T cell activation (VISTA) is an immune checkpoint protein that impairs antitumor T cell responses. While broadly expressed on myeloid cells and T cells, the specific contribution of T cell–intrinsic VISTA to antitumor immunity remains undefined. This study investigated the phenotypic and functional consequences of T cell–specific VISTA deletion in tumor-specific CD8+ T cells. Single-cell transcriptomic analysis, TCR repertoire profiling, and flow cytometry revealed that loss of T cell–intrinsic VISTA enhanced early priming and short-term expansion of CD8+ T cells, yet this initial advantage failed to confer durable tumor control. Persistent dysfunction in VISTA-deficient T cells was in part driven by trans-VISTA on myeloid cells, while CTLA-4 upregulation further constrained T cell responses. T cell–intrinsic VISTA deficiency cooperated with CTLA-4 blockade to improve T cell survival and broaden TCR repertoire diversity, resulting in more robust tumor regression than CTLA-4 inhibition alone. A transcriptional signature enriched in VISTA-deficient cytotoxic T cells correlated with favorable outcomes in cancer patients treated with existing immune checkpoint inhibitors. These findings collectively define T cell–intrinsic mechanisms by which VISTA enforces T cell dysfunction and underscore its potential as both a therapeutic target and a biomarker of resistance to current immunotherapies.
Authors
Cassandra Gilmour, Elizabeth DeLaney, Prerana B. Parthasarathy, Dia Roy, Hieu M. Ta, Amin Zakeri, Paolo Elguera Grandez, Sachin Patnaik, Keman Zhang, Ivan Juric, Rahul Rangan, Zahraa Al-Hilli, Anthony Tufaro, Booki Min, Samuel E. Weinberg, Timothy A. Chan, Natalie L. Silver, Stefanie Avril, Tyler Alban, Li Lily Wang
Copyright © 2026 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)