Role of regorafenib in macrophage

Regorafenib increased M1/M2 ratio of BMDMs polarization and proliferation/activation of co-cultured T cells in vitro, indicating angiogenesis-independent immunomodulatory effects. Suppression of p38 kinase phosphorylation and downstream CREB-KLF4 activity in BMDMs by regorafenib reversed M2 polarization. Regorafenib enhanced antitumor efficacy of adoptively transferred antigen-specific T cells, whereas macrophage deletion negated regorafenib’s antitumor effects. Synergistic antitumor efficacy between low-dose regorafenib and anti-PD1 was associated with multiple immune-related pathways in the tumor microenvironment. Mouse bone marrow-derived macrophages were polarized with IFN-gamma + LPS or IL4 for 24 h to induce M1 or M2 phenotypes, respectively.