PAF1-mediated transcriptional reprogramming confers docetaxel resistance in advanced prostate cancer.

Advanced prostate cancer (PCa) remains a significant clinical challenge, and docetaxel plays a significant role in disease management. Despite the efficacy of docetaxel as a first-line chemotherapy, resistance often develops. We developed three clinically relevant in vitro PCa cell models and transcriptomic analysis identified that the Paf1/RNA polymerase II complex component (PAF1)-associated pluripotent-transcription factor (TF), SOX2, plays a crucial role in docetaxel resistance. The master cancer stem cell (CSC) transcriptional regulator PAF1 is significantly higher in PCa cell lines, tumor tissues, and DR PCa cells than in age-matched control cells. To determine the molecular underlying and functional characteristics of PAF1 in resistance mechanisms, we performed coimmunoprecipitation, embryonic stem cell network proteins, in vitro tumor-initiating ability, and 3D multicellular organoid growth using PAF1 knockdown cells. Tet-inducible PAF1 depletion reduced the drug-efflux phenotype, tumor-initiating frequencies, and three-dimensional organoid growth of the docetaxel-resistant PCa cell lines. Functional studies also showed restoration of docetaxel sensitivity in a 3D tumorsphere model upon PAF1 depletion. PAF1 depletion was also associated with decreased pluripotent TFs and other CSC markers. This study provides a novel regulatory mechanism of docetaxel resistance in PCa through PAF1 and establishes clinically relevant docetaxel-resistant PCa cell lines.