HMGB1 Decreases CCR-2 Expression and Migration of M2 Macrophages under Hypoxia

Objective The hypoxic milieu at tumor microenvironment is able to drive the behavior of infiltrating tumor cells. Considering that hypoxia-mediated HMGB1 release is known to promote tumor growth, as well to enhance the pro-tumoral profile of M2 macrophages by a RAGE-dependent mechanism, it is tempting to evaluate the potential contribution of HMGB1 under hypoxia to restrain M2 macrophages mobility. Methods CCR-2 expression was evaluated in M2 polarized macrophages by western blotting and immunocytochemistry. The secreted levels of CCL-2 and the migration capability were evaluated using an ELISA and a chemotaxis assay, respectively. Results HMGB1, under hypoxic conditions, markedly reduce both the production of CCL-2 and the expression of its receptor CCR-2; and reduced the migration capacity of M2 macrophages. Conclusions These results provided new insights into the mechanisms that regulate M2 macrophages mobility at the tumor microenvironment.