Tumor released autophagosomes regulate M2-like macrophage polarization (TUM6P.974)

Abstract

Abstract Tumor cells secrete mediators that modulate macrophage activation and polarization into M2 type tumor associated macrophages (TAMs), which contribute to tumor progression. However, the mechanisms that regulate the polarization are poorly defined. We have previously reported that the enrichment of autophagosomes in tumor cell conditioned medium and malignant ascites from patients. The present study investigated the hypothesis that tumor released autophagosomes promoted M2 polarization. Here we isolated autophagosomes released from murine liver cancer cells using affinity purification. In vivo mouse experiments demonstrated that intraperitoneal injected autophagosomes were efficiently internalized by peritoneal macrophages, which correlated with upregulation of M2 markers. In vitro, coculture of autophagosomes with bone marrow-derived macrophages (BMDMs) also induced macrophage polarization into a M2-like phenotype. Furthmore, this effect of autophagosomes was largely abolished in BMDMs from MyD88 KO mice. Taken together, our findings suggest that, under stress conditions, tumor released autophagosomes may promote tumor progression via regulation of TAMs in tumor microenvironment, providing new insight into TAMs polarization. Keywords: Tumor released autophagosomes, Macrophage, Polarization, MyD88.