EP300/CREBBP acetyltransferase inhibition limits steroid receptor and FOXA1 signaling in prostate cancer cells (RNA-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.