Adrenomedullin/FOXO3 enhances sunitinib resistance in clear cell renal cell carcinoma by inhibiting FDX1 expression and cuproptosis.

Cuproptosis, a new type of copper-induced cell death, is involved in the antitumor activity and resistance of multiple chemotherapeutic drugs. Our previous study revealed that adrenomedullin (ADM) was engaged in sunitinib resistance in clear cell renal cell carcinoma (ccRCC). However, it has yet to be investigated whether and how ADM regulates sunitinib resistance by cuproptosis. This study found that the ADM expression was elevated in sunitinib-resistant ccRCC tissues and cells. Furthermore, the upregulation of ADM significantly enhanced the chemoresistance of sunitinib compared with their respective control. Moreover, cuproptosis was involved in ADM-regulated sunitinib resistance by inhibiting mammalian ferredoxin 1 (FDX1) expression. Mechanically, the upregulated ADM activates the p38/MAPK signaling pathway to promote Forkhead box O3 (FOXO3) phosphorylation and its entry into the nucleus. Consequently, the increased FOXO3 in the nucleus inhibited FDX1 transcription and cell cuproptosis, promoting chemoresistance. Collectively, cuproptosis has a critical effector role in ccRCC progress and chemoresistance and thus is a relevant target to eradicate the cell population of sunitinib resistance.