TMIC-51. GBP1 RECRUITS MACROPHAGES TO PROMOTE GLIOBLASTOMA GROWTH

Abstract Guanylate binding protein 1 (GBP1) is an interferon-inducible large GTPase which plays a key role in tumor development, but the molecular mechanism is poorly understood. Here we investigated whether GBP1 could influence the tumor microenvironment in glioblastoma, the most common and malignant brain tumor. We found that forced expression of GBP1 in glioblastoma cells induced macrophage polarization toward an M2 phenotype via upregulating Chemokine (C-C motif) ligand 2 (CCL2). CCL2 acted via its receptor C-C chemokine receptor 2 (CCR2) to enhance macrophage cell migration in vitro. The M2 macrophages in turn promoted glioblastoma cell proliferation and migration. The orthotopic mouse model showed that GBP1 recruited M2 macrophages into tumor to promote glioblastoma progression, and targeting CCL2/CCR2 signaling axis with a small molecule inhibitor RS504393 led to decreased macrophage attraction and M2 polarization and a significant tumor growth retardation and prolonged survival of tumor-bearing mice. Clinically, GBP1 expression positively correlated with M2 macrophage numbers and CCL2 expression in glioblastoma. Taken together, our results reveal that GBP1 modulates the tumor immune microenvironment through CCL2 induction to promote glioblastoma infiltrating growth, and targeting tumor-associated macrophages may represent a new therapeutic strategy against glioblastoma.