USP5 regulates purine metabolism and represents a therapeutic target in esophageal cancer.

Ubiquitination is a critical regulator of cancer development, yet the role of deubiquitinases in purine metabolism remains largely unexplored. In this study, untargeted metabolomic analysis revealed a significant upregulation of purine metabolism in esophageal cancer (ESCC). Database analysis further identified a strong positive correlation between the deubiquitinase USP5 and purine metabolism. Functional assays demonstrated that USP5 knockdown suppressed cell proliferation in vitro and inhibited tumor growth in vivo, accompanied by a reduction in purine metabolism. Mechanistically, USP5 directly interacts with inosine monophosphate dehydrogenase 2 (IMPDH2), the rate-limiting enzyme in de novo guanine nucleotide biosynthesis, and removes K48-linked polyubiquitin chains at lysine 489. This deubiquitination event stabilizes IMPDH2, prevents its proteasomal degradation, and promotes guanine nucleotide synthesis. Guanine supplementation enhanced ESCC cell proliferation, whereas dietary purine restriction suppressed tumor progression in vivo. Furthermore, we identified mebendazole, an FDA-approved anthelmintic, as a pharmacological inhibitor of USP5. Combination treatment with mebendazole and oxaliplatin significantly enhanced chemosensitivity in ESCC cells. Collectively, these findings establish the USP5-IMPDH2-guanine axis as a critical driver of ESCC progression and highlight its potential as a promising therapeutic target for ESCC.