AEG-1 silencing attenuates M2-polarization of glioma-associated microglia/macrophages and sensitizes glioma cells to temozolomide

Abstract

Glioma is the most frequent primary malignancy in the brain; temozolomide (TMZ) is the first-line chemotherapeutic agent used to combat this tumor. We showed here that astrocyte elevated gene-1 (AEG-1) was overexpressed in glioma tissues and associated with a worse subtype and a poor prognosis. CCK-8 proliferation assays and clone formation experiments presented that AEG-1 knockdown sensitizes glioma cells to TMZ. The γH2AX foci formation assays indicated that AEG-1 silencing promotes TMZ-induced DNA damage in glioma cells. Glioma-associated microglia/macrophages (GAMs), the largest subpopulation infiltrating glioma, play important roles in the tumor microenvironment. Bioinformatics analyses and functional studies demonstrated that AEG-1 silencing decreased M2-polarization of HMC3 microglia and the secretion of tumor supportive cytokines IL-6 and TGF-β1. The expression of AEG-1 was positively associated with M2 markers in glioma tissues varified by IHC staining. Based on the results of Affymetrix microarray and GSEA analyses, Western blot and Co-Immunoprecipitation assays were conducted to show that AEG-1 activates Wnt/β-catenin signaling by directly interacting with GSK-3β. The co-localization of AEG-1 and GSK-3β in the cytoplasm of glioma cells was detected through immunofluorescence staining. This study raises the possibility that targeting AEG-1 might improve the efficiency of chemotherapy and reduce immunosuppressive M2 GAMs in glioma.

Lucanthone Targets Lysosomes to Perturb Glioma Proliferation, Chemoresistance and Stemness, and Slows Tumor Growth In Vivo

“…Despite multimodal treatment, the recurrence rate for glioblastoma is ~100%. It has also been proposed that glioma cells change throughout the course of treatment such that the cells that survive treatment are functionally different than the parental tumor ( 47 – 49 ). We tested whether Lucanthone was able to exert oncolytic effects on glioma cells that have been selected for their ability to resist the standard chemotherapy temozolomide, TMZ.…”

“…Gliomas are comprised of multiple cell types specific to the CNS, and are heavily composed of CNS-resident microglia and blood-derived macrophages ( 70 ). Offsetting the tumor-promoting functions of these cells may directly slow the growth of gliomas and interact favorably with TMZ ( 49 , 71 , 72 ) and radiation ( 73 ). Investigations in peripheral tumor types, such as melanoma and hepatocellular carcinoma, revealed that late-stage autophagy inhibition with chloroquine, which was shown to act as an inhibitor of palmitoyl-protein thioesterase 1 (Ppt1) ( 74 – 76 ), reverses the immunosuppressive nature of tumor-associated macrophages and thus increases the efficacy of T-cell targeted PD-1 therapies ( 28 , 76 ).…”

Glioma-associated microglia/macrophages (GAMs) in glioblastoma: Immune function in the tumor microenvironment and implications for immunotherapy

“…M1 microglia/macrophages have the classic activated phenotype, and their activated receptors and functions are relatively clear. The polarization of M2 microglia and macrophages is strictly regulated and presents a highly dynamic state, often followed by M1 polarization ( 49 , 50 ). Type II inflammatory factors such as IL-4, IL-10, and IL-13 generally mediate M2 polarization, which can prevent further tissue damage by secreting multiple anti-inflammatory factors to downregulate the inflammatory response ( 51 , 52 ).…”

Microglia and Brain Macrophages as Drivers of Glioma Progression

“…In experimental animals, survival of TMZ-resistant glioma bearing mice can be improved by combination therapy with a p38 MAPK inhibitor and PD-L1 antibody and this seems to work via a reduction of infiltrating glioma-associated macrophages and PD-L1 expression on resident glioma-associated microglia [ 193 ]. Moreover, glioma cells can be sensitised to TMZ by silencing Metadherin (MTDH/AEG-1) which also attenuates M2-polarisation of glioma-associated microglia/macrophages [ 194 ].…”