DPP9 and nonpapillary renal cell carcinoma: Furthermore, dipeptidyl peptidase 9 (DPP9) competes with NRF2 for binding to KEAP1 in an enzyme-independent manner, thereby disrupting the KEAP1-NRF2 signaling pathway and influencing tumorigenesis and drug resistance in clear cell renal carcinoma (ccRCC) (11).