Ferroptosis-resistance determines high susceptibility of murine A/J strain to iron-induced renal carcinogenesis.

Cancer susceptibility is a critical factor to understand carcinogenesis. Intraperitoneal (ip) injection of an iron chelate, ferric nitrilotriacetate (Fe-NTA), produces hydroxyl radicals via Fenton reaction to induce ferroptosis in renal proximal tubules. Rats or mice subjected to repeated ip injections of Fe-NTA develop renal cell carcinoma (RCC). To elucidate the molecular mechanisms to cause susceptibility to renal carcinogenesis, we first established an inter-strain difference in the susceptibility to Fe-NTA-induced renal carcinogenesis in mice. Based on a previous observation of low incidence of RCCs with this model in C57BL/6J strain, we here chose A/J strain, resulting in a significantly higher susceptibility. Homozygous deletion of Cdkn2a/2b tumor suppressor locus was detected for the first time in mice with A/J strain. Focusing on ferroptosis and iron metabolism, we then explored the mechanisms involved in the difference in RCC development. We compared the protective responses in the kidney after Fe-NTA treatment between A/J and C57BL/6J strains. After 3-week Fe-NTA treatment, A/J mice maintained higher levels of expression of glutathione peroxidase 4 and xCT (SLC7A11), leading to a lower level of lipid peroxidation. Simultaneously, A/J mice decreased expression of transferrin receptor and increased expression of ferritin to greater degrees than C57BL/6 mice. After a single Fe-NTA injection, higher levels of oxidative cell damage and cytosolic catalytic Fe(II) were observed in C57BL/6J mice, accompanied by a greater increase in lipocalin-2. Lipocalin-2 deficiency significantly decreased oxidative renal damage. Our results suggest that genetic trait favoring ferroptosis-resistance contributes to high susceptibility to Fe-NTA-induced RCC in A/J strain.