CROSSTALK BETWEEN GLIOMA CELLS AND TUMOR ASSOCIATED-MACROPHAGES: MECHANISMS AND THERAPEUTIC STRATEGIES

Macrophages are highly plastic cells, able to respond to several microenvironment signals acquiring distinct functional phenotypes. In Glioblastoma (GBM), the most common malignant brain tumor, tumor-associated-macrophages (TAMs) represent the major infiltrating immune cell populations and are key drivers of the local immunosuppression supporting tumor progression and the resistance to immunomodulating treatments. Mutations in enzymes isocitrate dehydrogenases (IDH) occur in GBM subsets, characterized by more favorable prognosis. Also, other molecular alterations and metabolic features, such as accumulation of the oncometabolite 2-hydroxyglutarate, are associated with IDH-mutations. Despite many therapeutic strategies, GBM recur in almost all patients and prognosis remain poor, the development of new therapeutic strategies is strongly needed. In the last decades, innovative engineered nanovectors bears a promise for GBM treatment: these multifunctionalized liposomes encapsulate drugs and are able to cross the blood brain barrier that will guarantee the localized release of candidate drugs to control neuroinflammation. The aim of the present study is to investigate the relevance of the cross-talk between macrophages and glioma cells, needed to overcome limitations of the current therapeutic approaches. Firstly, we analysed the interplay between macrophages and U87 glioma cells lines, harbouring wild-type or mutant IDH genes, through direct and indirect cocultures. Then we investigated the mechanisms underlying the macrophages-glioma cells’ crosstalk in hypoxia, a key aspect of the tumor microenvironment. In addition, in the context of nanovectors’ strategy, we set coculture models of macrophages and patient-derived GSCs to explore the potential of macrophages as target cells of encapsulated drugs for the rebalance of the glioma microenvironment. In our results, we showed that glioma-derived factors, released by U87 IDH1-WT and IDH-MUT, are able to polarize macrophages toward a pro-tumoral M2-like phenotype with the increase of the CD206 expression. Moreover, the effect of TCM collected from U87 IDH1-MUT is different compared with TCM from U87 IDH1-WT on macrophages’ differentiation and polarization. In addition, we demonstrated that hypoxic condition induces its target genes in a cell-specific manner, with significant differences between Wt and IDH-mutant U87 cultures. Similarly, in cocultures macrophages shape tumor cells responses to hypoxia. In the nanovector experiments we evaluated that the vitality of macrophages treated with free drugs is different based on polarization conditions. Moreover, macrophage in coculture with GSC cells are less sensible to the drug treatment compare to macrophages alone.