Therapeutic strategies for <scp>MMAE</scp> ‐resistant bladder cancer through <scp>DPP4</scp> inhibition

Monomethyl auristatin E (MMAE) is used as the cytotoxic payload for enfortumab vedotin (EV) in the treatment of locally advanced and metastatic bladder cancer (BC). However, the development of resistance to MMAE in BC is a therapeutic problem. To explore the mechanism of resistance to MMAE in BC, we established MMAE-resistant BC cells (MR-BCs). RNA sequencing analysis showed that the expression of dipeptidyl peptidase 4 (DPP4, also called CD26) increased significantly in MR-BCs compared with parental BC cells. Knock down of DPP4 expression using small interfering RNA inhibited the viability of MR-BCs. In addition, the DPP4 inhibitor sitagliptin suppressed the proliferation, migration, and invasion of BC cells, and cotreatment with MMAE effectively induced cell apoptosis, arrested cells in the G₂M phase of the cell cycle, increased reactive oxygen species production by inhibiting the AKT pathway, and significantly inhibited the in vivo growth of MMAE-resistant cells. This study provides insights into the use of DPP4 inhibitors as a treatment strategy for MMAE-resistant BC.