Absent in melanoma 2-mediating M1 macrophages facilitate tumor rejection in renal carcinoma

Absent in melanoma 2 (AIM2) as an immune regulator for the regulation of tumor-associated macrophages (TAMs) function is unclear in tumor development. Here, the AIM2 function was investigated in TAMs-mediated malignant behaviors of renal carcinoma. The correlation analysis result showed that the AIM2 expression in TAMs was negatively correlated with the percentages of M2-like polarization phenotype in human or murine renal cancer specimens. By the cocultured assay with bone marrow-derived macrophages (BMDMs) and Renca cells, overexpression of AIM2 in macrophages enhanced the inflammasome activation and reversed the phenotype from M2 to M1. Compared with BMDMs-Ctrl cocultured group, BMDMs-AIM2 cocultured group showed reduced tumor cell proliferation and migration. The blockade of inflammasome activation by the inhibitor Ac-YVAD-CMK abrogated AIM2-mediated M1 polarization and the inhibition of tumor cell growth. To evaluate the therapeutic efficacy of AIM2-mediated M1 macrophages in vivo, BMDMs-AIM2 were intravenously injected into subcutaneous Renca-tumor mice. The results showed that the infiltration of M1 TAMs was increased and tumor growth was suppressed in BMDMs-AIM2-treated mice when compared with BMDMs-Ctrl-treat mice. Accordingly, the blockade of inflammasome activation reduced the anti-tumor activities of BMDMs-AIM2. Moreover, the lung metastases of renal carcinoma were suppressed by the administration of BMDMs-AIM2 accompanied with the reduced tumor foci. These results demonstrated that AIM2 enhanced TAMs polarization switch from anti-inflammatory M2 phenotypy to pro-inflammatory M1 through inflammasome signaling activation, thus exerting therapeutic intervention in renal carcinoma models. Our results provide a possible molecular mechanism for the modulation of TAMs polarization in tumor microenvironment and open a new potential therapeutic approach for renal cancer.