Targeting UBE2T Potentiates Gemcitabine Efficacy in Pancreatic Cancer by Regulating Pyrimidine Metabolism and Replication Stress

Although small patient subsets benefit from current targeted strategies or immunotherapy, gemcitabine remains the first-line drug for pancreatic cancer (PC) treatment. However, gemcitabine resistance is widespread and compromises long-term survival. Here, we identified ubiquitin-conjugating enzyme E2T (UBE2T) as a potential therapeutic target to combat gemcitabine resistance in PC.Proteomics and metabolomics were combined to examine the effect of UBE2T on pyrimidine metabolism remodeling. Spontaneous PC mice (LSL-KrasG12D/+, LSL-Trp53R172H/+, Pdx1-Cre; KPC) with Ube2t-conditional knockout, organoids, and large-scale clinical samples were used to determine the effect of UBE2T on gemcitabine efficacy. Organoids, patient-derived xenografts (PDX), and KPC mice were used to examine the efficacy of the combination of a UBE2T inhibitor and gemcitabine.Spontaneous PC mice with Ube2t deletion had a marked survival advantage after gemcitabine treatment, and UBE2T levels were positively correlated with gemcitabine resistance in clinical patients. Mechanistically, UBE2T catalyzes ring finger protein 1 (RING1)-mediated ubiquitination of p53 and relieves the transcriptional repression of ribonucleotide reductase subunits M1 and M2, resulting in unrestrained pyrimidine biosynthesis and alleviation of replication stress. Additionally, high-throughput compound library screening using organoids identified pentagalloylglucose (PGG) as a potent UBE2T inhibitor and gemcitabine sensitizer. The combination of gemcitabine and PGG diminished tumor growth in PDX models and prolonged long-term survival in spontaneous PC mice.Collectively, UBE2T-mediated p53 degradation confers PC gemcitabine resistance by promoting pyrimidine biosynthesis and alleviating replication stress. This study offers an opportunity to improve PC survival by targeting UBE2T and develop a promising gemcitabine sensitizer in clinical translation setting.