Rewiring the transcriptome of castration-resistant prostate cancer through CDK9 inhibition dataset 3

The rewiring of transcriptional and epigenetic programs is a hallmark of cancer and a targetable vulnerability for treating metastatic cancers. CDK9, whose primary function is to promote transcriptional elongation at active gene promoters, is emerging as a therapeutic target with broad efficacy in various cancer types. We used the novel and selective CDK9 inhibitor PRT2527 to demonstrate this approach's therapeutic efficacy and tolerability in multiple preclinical tumor models with specific transcriptional dependencies. In castration-resistant prostate cancer (CRPC), PRT2527 inhibited CDK9, AR and other transcription factors (e.g., c-MYC, STAT3, and NF-kB) implicated in disease progression and treatment resistance. PRT2527 reduced the proliferation of tumor cell lines and the growth of 3D tumor organoids and spheroids, demonstrating the impact on the bulk tumor cells and the stem-like subpopulation in human and murine CRPC models. PRT2527 was also highly active in vivo in patient-derived CRPC models LuCaP 35 and LuCap 145.2) and transgenic Pb-Cre4;Ptenflox/flox;R26ERG (ERG/PTEN) mice. Notably, PRT2527 induced relevant changes in gene expression, reflecting the impact on the distinct transcriptional programs of various CRPC models. Despite this heterogeneity, a common core of genes and pathways related to oncogenesis was affected in all models. Our data further demonstrate the efficacy and safety of CDK9 inhibition in multiple models of transcriptionally addicted solid tumors. Given its role in transcription, CDK9 is an ideal target for developing novel therapeutic strategies to block tumor cell plasticity driving tumor progression, metastatic spread, and treatment resistance.