Lineage plasticity, or transdifferentiation, is increasingly recognized as a resistance mechanism to androgen receptor (AR) inhibition in prostate cancer. Lineage plasticity is characterized by loss of AR signaling and epithelial differentiation, along with activation of stemness-associated pathways, epithelial-mesenchymal transition (EMT), or alternative differentiation programs such as neuroendocrine prostate cancer (NEPC). Loss of the tumor suppressors TP53 and RB1 is common in tumors exhibiting lineage plasticity; however, mechanisms by which TP53/RB1 loss promotes this phenotype remain poorly understood, and effective treatments are limited. Using multi-omic profiling of TP53/RB1 loss prostate cancer models, we identified alterations in chromatin accessibility, DNA methylation, and gene expression associated with lineage plasticity. Importantly, many pathways activated upon TP53/RB1 loss could be blocked through BET bromodomain inhibition. TP53/RB1-deficient cells also harbored widespread DNA methylation changes that silenced pathways linked with restraining lineage plasticity. Combined BET bromodomain and DNA methyltransferase (DNMT) inhibition was more effective than single agent treatment in suppressing growth of TP53/RB1 loss models exhibiting a stem-like or NEPC program. This was partly explained by abrogation of discrete lineage plasticity pathways modulated by each agent. Altogether, our work suggests combined BET bromodomain and DNMT inhibition is a promising therapeutic approach for prostate tumors exhibiting lineage plasticity.
W. Storck, Diana Flores, A. Kumaraswamy et al.· JCI Insight· 0 citations
The tumor microenvironment (TME) of pancreatic ductal adenocarcinoma (PDAC) is characterized by restrained function of effector T cells that drives resistance to immunotherapy. While tumor-extrinsic stroma and myeloid cells have been shown to mediate PDAC immune evasion, the role of tumor-intrinsic post-transcriptional gene regulation in driving tumor-immune crosstalk has been relatively unexplored. Here, we report that the RNA-binding protein HuR (ELAVL1) is enriched in human PDAC and negatively correlates with T-cell infiltration. In two immunocompetent, murine models of PDAC, we found that genetic disruption of HuR impaired tumor growth without significantly impacting in vivo proliferation. Comprehensive spatial and flow cytometry profiling of the PDAC TME revealed that genetic disruption of HuR in PDAC enhanced both T-cell number and functional state. Moreover, T-cell depletion abrogated the growth difference caused by HuR loss. Mechanistically, RNA immunoprecipitation sequencing, single-cell RNA sequencing, and orthogonal functional assays in vitro and in vivo showed that HuR stabilized mTOR pathway transcripts critical for metabolic adaptation in PDAC. HuR-driven metabolic reprogramming promoted tumor nutrient dominance and limited nutrient consumption by neighboring tumor-reactive T cells. Accordingly, HuR depletion sensitized PDAC tumors to immune checkpoint blockade and allowed for the expansion of tumor-specific T-cell populations, suggesting that HuR-mediated nutrient dominance and immune evasion have translational relevancy. Overall, we found that the post-transcriptional regulator HuR facilitates immune evasion in PDAC by constraining T-cell function, identifying HuR blockade as a promising therapeutic strategy in combination with immunotherapies.
Yi-Fei Guo, Jennifer M. Finan, Alexandra Q. Bartlett et al.· Cancer immunology research· 0 citations
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