Deciphering the Impact of ZNF397-deficiency in Promoting TET2-driven Epigenetic Rewiring, Lineage Plasticity, and Therapy Resistance in Prostate Cancer

PROJECT SUMMARY Phenotypic plasticity and epigenetic reprogramming stand as two noteworthy cancer hallmarks. Lineage plasticity, in particular, has been recognized as a key mechanism that enables cancer cells to evade targeted therapies. Prostate cancer (PCa), especially its most aggressive form, metastatic castration-resistant prostate

cancer (mCRPC), exemplifies lineage plasticity-based resistance to Androgen Receptor (AR) targeted therapies. This resistance significantly constrains patient clinical outcomes, rendering mCRPC incurable, underscoring the critical demand for elucidating the mechanisms of resistance and identifying actionable therapeutic targets to

overcome resistance. We identified ZNF397 as a pivotal coactivator for AR expression, essential for the transcriptional program governing AR-driven luminal lineage in various cancers. ZNF397 deficiency, a prevalent event observed in 25-40% of PCa patients, enables the transition of cancer cells from an AR-driven luminal

lineage to a TET2-driven lineage plastic state, consequently leading to AR therapy resistance. Preliminary results also suggest that both genetic and pharmaceutical inactivation of TET2 eradicates AR targeted therapy resistance, highlighting TET2 as a potential therapeutic target to combat AR targeted therapy resistance in

advanced PCa, including mCRPC. Therefore, the Overall Objective of this study is to comprehensively decipher the molecular mechanism of ZNF397-deficiency in promoting lineage plasticity and AR-targeted therapy resistance, with a goal to develop innovative therapeutic approaches to overcome resistance and benefit patients

suffering from this devastating disease. We proposed three aims to test the hypothesis that the frequently observed ZNF397-deficiency is a molecular driver that promotes the transition of cancer cells from an AR-driven luminal lineage state to a TET2-driven lineage plastic state, which subsequently becomes non-responsive to AR-

targeted therapy. In Aim 1, we will comprehensively assess the effect of ZNF397-deficiency in PCa tumorigenesis, therapy responsiveness and lineage plasticity, using our uniquely generated GEMM with ZNF397-KO, as well as single cell RNA-seq and spatial transcriptomics. In Aim 2, we will elucidate the molecular

mechanism of TET2-driven epigenetic rewiring and lineage plasticity in ZNF397-deficient PCa. In Aim 3, we will assess the predictive potency of ZNF397 expression as a biomarker for AR targeted therapy response and examine the efficacy of two novel strategies to overcome resistance in ZNF397-deficient tumors: TET2 inhibitors

and ZNF397-DUBTACs. The proposed aims will capitalize on our laboratory's expertise and that of our collaborators to comprehensively define the molecular function of ZNF397. Completion of this project will not only refine our understanding of the mechanisms propelling AR-targeted therapy resistance but also lead to a

new predictive biomarker and two innovative therapeutic strategies to combat this lethal complication of modern targeted therapies, thereby improving the clinical outcomes for patients.