CDK7 inhibition augments the response against multidrug chemotherapy in pancreatic cancer

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with a dismal prognosis. Although combined treatment with gemcitabine and albumin-bound paclitaxel has improved the prognosis of PDAC, both intrinsic and acquired chemoresistance cloud the outcomes. Hence, there is an urgent need to explore new therapeutic targets and formulate innovative strategies for the more effective treatment of PDAC.Methods: We transduced pancreatic cancer cells with a protein kinase library, and transfected cells were selected by puromycin treatment, followed by continuous exposure to vehicle control or gemcitabine/paclitaxel chemotherapy for 21 days. Next-generation sequencing as well as MAGeCK-VISPR analysis were performed to the identify candidate genes. Finally, we used the CRISPR-Cas9 to knockout the target gene, confirming that it is a viable target for overcoming chemoresistance in vivo and in vitro.Results: We identified several cell cycle checkpoint kinases and DNA damage-related kinases as targets for overcoming chemoresistance. Among them, cyclin-dependent kinase 7 (CDK7) ranked highly in both screenings. We demonstrated that both gene knockout and pharmacological inhibition of CDK7 by THZ1 result in cell cycle arrest, apoptosis induction. Furthermore, THZ1 synergized with gemcitabine and paclitaxel in vitro and in vivo, resulting in enhanced antitumor effects.Conclusions: Our findings support the application of CRISPR-Cas9 screening in identifying novel therapeutic targets and provide new strategies for overcoming chemoresistance in pancreatic cancer.