Targeting the DDX3/PAF1 axis enhances chemotherapy efficacy in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy that has a poor survival rate of ∼13 % with limited options for effective therapies. DDX3 is a member of the DEAD-box RNA helicase enzyme family. It acts as an adapter protein that interacts with several transcription factors, enhancing their binding ability to the promoters of genes involved in cancer progression. Previously, we demonstrated that PAF1, a component of the RNA polymerase II-associated factor 1 complex, interacts with DDX3 to promote PDAC stemness. Here, we investigated the therapeutic efficacy of RK-33, a small-molecule inhibitor targeting DDX3, in combination with gemcitabine (GEM) and 5-fluorouracil (5FU), which enhanced therapeutic efficacy in KRAS-driven PDAC.-DDX3 and PAF1 exhibit progressively increased expression in various stages and correlate well with poor survival of PDAC. Targeting DDX3/PAF1 significantly mitigated clonogenic, EMT, and stemness phenotypes in PDAC cells. It also reduced tumor growth, proliferation, and increased apoptosis in xenograft and PDAC organoid models. Finally, MXRA5, EDIL3, COL13A1, and SLC16A2 were identified as top downstream response genes upon RK-33 treatment and potential new targets to mitigate extracellular matrix remodeling, angiogenesis, cell migration, and cell cycle progression, thereby enhancing the therapeutic efficacy of GEM and 5FU Overall, our data indicate that RK-33 enhances the therapeutic efficacy of GEM and 5FU in mitigating PDAC aggressiveness. Consequently, these findings open new avenues for developing efficacious therapeutic adjuvants to treat advanced pancreatic cancer.