Kynurenine facilitates renal cell carcinoma progression by suppressing M2 macrophage pyroptosis through inhibition of CASP1 cleavage

Renal cell carcinoma (RCC) is an aggressive malignancy with a poor prognosis influenced by pyroptosis in tumor-associated M2 macrophages. This study investigated how kynurenine modulates pyroptosis in M2 macrophages and promotes RCC progression. M2 macrophages were treated with pyroptosis inhibitor VX-765 or kynurenine to evaluate their effects on cell viability and pyroptosis. Transwell co-culture systems were employed to assess the impact of M2 macrophages on RCC cell proliferation, colony formation, and viability. The interaction between kynurenine and CASP1 (caspase-1), a key executor of pyroptosis that cleaves gasdermin D (GSDMD) to trigger inflammatory cell death, was analyzed using surface plasmon resonance. The results demonstrated that VX-765 treatment significantly enhanced M2 macrophage viability while reducing pyroptosis, thereby promoting RCC cell proliferation in co-culture systems. Kynurenine significantly enhanced M2 macrophage viability while suppressing pyroptosis. Mechanistically, kynurenine reduced the cleavage of CASP1 (caspase-1) by directly binding to it. Overexpression of CASP1 reversed kynurenine-induced suppression of pyroptosis in M2 macrophages. Furthermore, CASP1 overexpression abolished kynurenine-mediated enhancement of RCC cell viability, colony formation, and proliferation. This study revealed that kynurenine inhibits pyroptosis in M2 macrophages via direct targeting of CASP1, creating a tumor-supportive microenvironment that accelerates RCC progression. These findings establish the kynurenine-CASP1 axis as a critical regulator of M2 macrophage pyroptosis and demonstrate its role in promoting RCC progression, identifying a potential therapeutic target for RCC treatment.