USP1 promotes pancreatic cancer progression and autophagy by deubiquitinating ATG14

Pancreatic ductal adenocarcinoma (PDAC) is characterized by extremely poor prognosis, high mortality and limited therapeutic strategy. Autophagy is hyperactivated in PDAC and targeting autophagy are emerging as promising therapeutic strategies. The dysfunction of deubiquitinase USP1 results in tumorigenesis and chemotherapy resistance. However, little is known about how USP1 regulates autophagy and its mechanism in tumor progression and drug sensitivity in PDAC. In this study, we found USP1 elevated in pancreatic cancer and USP1 expression inversely correlated with overall survival. USP1 depletion inhibited cell proliferation, epithelial-mesenchymal transition (EMT) and migration in PDAC cells. Interestingly, USP1 knockdown or inhibition reduced autophagy initiation and autophagy flux. By screening of interacting protein using co-Immunoprecipitation, we identified that USP1 interacted with ATG14 protein, acting as a core component in autophagy initiation. Furthermore, USP1 overexpression deubiquitinated and enhanced ATG14 protein stability by reduced binding ubiquitin levels, whereas USP1 inhibition promoted its proteasome-dependent degradation. Notably, USP1 depletion or a novel USP1 inhibitor I-138 dramatically delayed tumor growth in xenograft model. USP1 inhibitor synergistically enhanced the anti-cancer efficiency of cisplatin in PDAC cells. Collectively, our study identifies USP1 as the first deubiquitinase in the modulation of ATG14 deubiquitination and unveils a regulatory role for USP1 in autophagy and PDAC progression. Targeting USP1 using a selective inhibitor I-138 may provide an effective strategy for chemotherapy treatment and combating drug resistance in autophagy-activated pancreatic cancer.