The Histone Methyltransferase KMT2D is a Critical Mediator of Lineage Plasticity and Therapeutic Response in Castration Resistant Prostate Cancer [DU145 Bulk RNA-seq]

Castration-resistant prostate cancer (CRPC) is largely dependent on the androgen receptor (AR) for growth and often exhibits hyperactive PI3K signaling, most frequently due to PTEN loss. Therapeutic pressure from anti-AR therapies can induce trans-differentiation toward an AR-independent phenotype. Recently, different subtypes of AR-independent CRPC have been redefined, with the stem cell-like (SCL) subtype emerging as one of the most prevalent. Elucidation of the epigenetic mechanisms controlling the maintenance of these distinct CRPC cell states could pave the way for effective combinatorial therapies for CRPC. In this study, we identified a key role for the histone methyltransferase KMT2D in establishing the chromatin competence necessary for the recruitment of AR and FOXA1 transcription factors (TFs) that are essential for the AR transcriptional output in AR-dependent CRPC cell lines, patient derived organoids, and patient samples. Unexpectedly, KMT2D maintained the identity of the AR-low CRPC-SCL subtype and controlled activity of AP-1 TFs such as FOSL1, which acts as a master regulator of this subtype. Single cell transcriptomics and chromatin assays underscored the role of KMT2D in sustaining a mixed lineage cell state via AP-1 and FOXA1. The combined suppression of PI3K/AKT and KMT2D reduced cell proliferation in prostate cancer cells and patient-derived organoids in both CRPC-AR and CRPC-SCL subtypes. Altogether, these results unveil KMT2D as a major mediator of the epigenetic landscape in subtype-specific CRPC, contributing to tumor growth and therapeutic response. Overall design: Bulk RNA-Seq was performed in DU145 AR-neg prostate cancer cells with doxycycline-inducible knockdown of KMT2D

去势抵抗性前列腺癌（Castration-resistant prostate cancer, CRPC）的生长高度依赖雄激素受体（androgen receptor, AR），且常伴随过度激活的磷脂酰肌醇3-激酶（PI3K）信号通路，该通路异常最常见的诱因为PTEN缺失。抗AR治疗带来的治疗选择压力可诱导肿瘤发生转分化，形成AR非依赖表型。近期，学界已重新定义了多种AR非依赖型CRPC亚型，其中干细胞样（stem cell-like, SCL）亚型已成为最常见的亚型之一。阐明调控这些不同CRPC细胞状态维持的表观遗传机制，可为CRPC的有效联合治疗开辟新路径。本研究中，我们在AR依赖型CRPC细胞系、患者来源类器官及患者样本中，明确了组蛋白甲基转移酶KMT2D在建立染色质开放状态中的关键作用——该状态是招募AR与FOXA1转录因子（transcription factors, TFs）所必需的，而这两种转录因子对AR的转录活性至关重要。出乎意料的是，KMT2D可维持AR低表达的CRPC-SCL亚型的细胞身份，并调控FOSL1等激活蛋白1（AP-1）转录因子的活性，而FOSL1是该亚型的核心调控因子。单细胞转录组学与染色质检测实验证实，KMT2D可通过AP-1与FOXA1维持混合谱系细胞状态。同时抑制PI3K/AKT通路与KMT2D，可降低CRPC-AR与CRPC-SCL两种亚型的前列腺癌细胞及患者来源类器官的细胞增殖能力。综上，本研究结果揭示KMT2D是亚型特异性CRPC表观遗传景观的重要介导因子，其参与调控肿瘤生长与治疗应答。整体实验设计：我们对转染多西环素诱导性KMT2D敲低载体的DU145 AR阴性前列腺癌细胞开展了批量RNA测序（Bulk RNA-Seq）。