DBC1 promotes metastatic castration-resistant prostate cancer by enhancing the stability and activity of HSF1 [ChIP-seq]

Heat shock factor 1 (HSF1) is a key stress-protective transcription factor that is exploited by various cancers to promote cancer cell survival, therapy resistance, and metastasis. Metastatic castration-resistant prostate cancer (mCRPC) is the leading cause of cancer-related death in men worldwide, and mCRPC progression is associated with increased dependence on HSF1. However, mechanisms underlying HSF1 stabilization and persistent activation in metastatic malignancies remain unclear. Here we show that the HSF1-driven transcriptional program and its genome occupancy in mCRPC cells are distinct from those of CRPC cells. HSF1 is highly activated and required for the metastatic potential of mCRPC cells. Moreover, we report DBC1 as a critical regulator of HSF1 stability and activity in mCRPC cells. DBC1 is required for genome-wide chromatin occupancy and target gene expression of HSF1. Mechanistically, DBC1 enhances DYRK2/PKA-mediated HSF1 phosphorylation at S320/S326 and inhibits CHIP-mediated HSF1 ubiquitination, thereby stabilizing and activating HSF1. Importantly, DBC1 loss suppresses growth and metastasis of mCRPC cells, and high DBC1 expression correlates with poor outcomes in patients with mCRPC. Our results highlight the critical role of DBC1 as a key HSF1 coregulator in mCRPC progression and provide insights into regulatory mechanisms of HSF1 stability and activity in advanced and metastatic cancers. 22RV1, SM1 (derived from spine-metastasized 22RV1 cells), and their HSF1 or DBC1 knockout counterpart cells (22RV1-H1KO, 22RV1-D1KO, SM1-H1KO, and SM1-D1KO) were used for the analysis. We performed chromatin immunoprecipitation sequencing (ChIP-seq) using antibodies for HSF1, DBC1, and H3K27ac.

热休克因子1（Heat shock factor 1，HSF1）是一类关键的应激保护性转录因子，可被多种癌症劫持以促进癌细胞存活、治疗抵抗与转移。转移性去势抵抗性前列腺癌（metastatic castration-resistant prostate cancer，mCRPC）是全球男性癌症相关死亡的首要诱因，其进展与HSF1依赖性增强密切相关。然而，转移性恶性肿瘤中HSF1的稳定化与持续激活的潜在机制仍不明晰。
本研究发现，mCRPC细胞中HSF1驱动的转录程序及其全基因组染色质结合谱与去势抵抗性前列腺癌（CRPC）细胞存在显著差异。HSF1在mCRPC细胞中高度激活，且是其转移潜能所必需的。此外，本研究证实DBC1是mCRPC细胞中HSF1稳定性与活性的关键调控因子。DBC1对于HSF1的全基因组染色质结合及其靶基因表达不可或缺。
从机制层面来看，DBC1可增强DYRK2/PKA介导的HSF1在S320与S326位点的磷酸化，并抑制CHIP介导的HSF1泛素化，从而稳定并激活HSF1。值得注意的是，敲除DBC1可抑制mCRPC细胞的增殖与转移，且DBC1高表达与mCRPC患者的不良预后相关。本研究结果凸显了DBC1作为HSF1关键共调控因子在mCRPC进展中的核心作用，并为晚期及转移性癌症中HSF1稳定性与活性的调控机制提供了新见解。
本研究采用22RV1、SM1（源自脊柱转移灶的22RV1细胞）及其HSF1或DBC1敲除对应细胞株（22RV1-H1KO、22RV1-D1KO、SM1-H1KO及SM1-D1KO）开展分析。我们使用针对HSF1、DBC1及H3K27ac的抗体进行染色质免疫沉淀测序（chromatin immunoprecipitation sequencing，ChIP-seq）。