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 cancer stem cell (CSC) transcriptional master regulator PAF1 is significantly higher in PCa cell lines, tumor tissues, and docetaxel resistant (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.