USP10-dependent stabilization of UGT8 promotes oxaliplatin resistance by sustaining NRF2-associated antioxidant signaling and suppressing ferroptosis in gastric cancer.

Oxaliplatin (OXA) is widely used to treat advanced gastric cancer, but acquired resistance limits its benefit. How resistant cells avoid ferroptosis remains unclear. Quantitative proteomics identified UGT8, a glycosphingolipid biosynthetic enzyme, as an upregulated protein in OXA-resistant gastric cancer cells. UGT8 protein was also increased in tumors from clinically OXA-resistant patients treated with oxaliplatin-based chemotherapy, and high UGT8 expression was associated with shorter survival. UGT8 overexpression increased OXA tolerance, while UGT8 depletion sensitized resistant cells and patient-derived organoids (PDOs) from clinically OXA-resistant patients to OXA. UGT8 depletion increased lipid reactive oxygen species and malondialdehyde, reduced glutathione, and aggravated ferroptosis-associated mitochondrial damage. Immunoprecipitation followed by mass spectrometry identified USP10 as a UGT8-associated protein. USP10 increased UGT8 stability and limited its K48-linked polyubiquitination. K307 was identified by mutational analysis as a functionally important residue involved in USP10-regulated UGT8 ubiquitination. UGT8 increased NRF2 nuclear accumulation and maintained HO-1, SLC7A11, and GPX4 expression. Restoring UGT8 or pharmacologically enhancing NRF2-associated antioxidant signaling reduced the effects of USP10 or UGT8 depletion on OXA sensitivity and ferroptosis-associated changes. Disrupting the USP10-UGT8 pathway also improved the OXA response in xenografts. These results support a role for USP10-dependent UGT8 stabilization in sustaining NRF2-associated antioxidant signaling, suppressing ferroptosis, and promoting OXA resistance.