EP300/CREBBP acetyltransferase inhibition limits steroid receptor and FOXA1 signaling in prostate cancer cells (ATAC-seq)

The androgen receptor (AR) serves as the primary target for therapeutic intervention in prostate cancer (PCa), and AR-targeted treatments constitute the cornerstone of clinical management for this malignancy. Nevertheless, their effectiveness is often compromised by the emergence of resistance mechanisms. These resistant forms of PCa persist in activating AR signaling, highlighting the urgent need for new therapeutic strategies to combat therapy-resistant PCa. Resistance to AR-targeted therapies can manifest through a multitude of mechanisms, including the overexpression of AR splice variants and altered activities of other transcription factors, such as the glucocorticoid receptor (GR) and FOXA1. A shared characteristic among these transcription factors is their dependence on a common set of coregulators, with EP300/CREBBP being a prominent example. This suggests a compelling rationale for employing coregulatory-targeted therapies in the management of treatment-resistant PCa. Here, we aimed to explore the impact of EP300/CREBBP acetyltransferase inhibition on steroid receptor and FOXA1 signaling in PCa cells, employing genome-wide techniques. Our findings illuminate that EP300/CREBBP inhibition exerts a substantial disruptive effect on the AR-regulated transcriptome and receptor chromatin binding, primarily by downregulating the AR-gene. Similarly, the transcriptome regulated by GR and the chromatin binding of the receptor were also hindered, although this was not associated with decreased GR expression levels. Instead, EP300/CREBBP acetyltransferase inhibition leads to a significant reduction in FOXA1 chromatin binding, consequently constraining GR signaling. In summary, our results emphasize how EP300/CREBBP acetyltransferase inhibition distinctly curtails the signaling activities of oncogenic transcription factors, underscoring the potential effectiveness of coregulatory-targeted therapies in PCa. Overall design: Examination of chromatin accessibility by ATAC-seq from 22Rv1 and VCaP prostate cancer cells treated with or without A485 and grown in the presence or absence of ENZ. Sequencing was done with Illumina NextSeq 500 or Illumina NextSeq 2000.

雄激素受体（androgen receptor, AR）是前列腺癌（prostate cancer, PCa）治疗干预的核心靶点，靶向AR的治疗方案亦是该恶性肿瘤临床管理的基石。然而，此类治疗的疗效常因耐药机制的出现而受损。这类耐药性前列腺癌仍可激活AR信号通路，凸显了开发新型治疗策略以对抗治疗耐药性前列腺癌的迫切需求。AR靶向治疗的耐药可通过多种机制产生，包括AR剪接变体的过表达，以及糖皮质激素受体（glucocorticoid receptor, GR）、FOXA1等其他转录因子的活性异常。这些转录因子的共同特征是依赖于一组共通的共调节因子，其中EP300/CREBBP便是典型代表。这一特性为采用靶向共调节因子的治疗方案管理治疗耐药性前列腺癌提供了充分的理论依据。

本研究旨在借助全基因组技术，探究EP300/CREBBP乙酰转移酶抑制对前列腺癌细胞中类固醇受体及FOXA1信号通路的影响。研究结果显示，EP300/CREBBP抑制可显著破坏AR调控的转录组及受体染色质结合行为，其主要机制为下调AR基因的表达。类似地，GR调控的转录组及受体染色质结合也受到阻碍，尽管这一现象与GR表达水平的降低并无关联。相反，EP300/CREBBP乙酰转移酶抑制可显著降低FOXA1的染色质结合能力，进而限制GR信号通路的活性。

综上，本研究结果阐明了EP300/CREBBP乙酰转移酶抑制可特异性削弱致癌转录因子的信号活性，凸显了靶向共调节因子的治疗方案在前列腺癌治疗中的潜在有效性。

实验整体设计：对经或未经A485处理、在含或不含ENZ的培养基中培养的22Rv1与VCaP前列腺癌细胞，通过ATAC-seq（转座酶可及性测序）检测其染色质可及性。测序采用因美纳（Illumina）NextSeq 500或NextSeq 2000平台完成。