Immune-based antitumor effects of BRAF Inhibitors rely on signaling by CD40L and IFN-γ

Menée à l'aide d'un modèle murin de mélanome présentant la mutation V600E du gène BRAF, cette étude met en évidence des mécanismes par lesquels, via la signalisation CD40L et IFNγ, un inhibiteur de BRAF (PLX4720) favorise le développement d'une immunité antitumorale dans le micro-environnement

Résumé en anglais

B-RafV600E inhibitors have been suggested to promote tumor regression with the help of host immunity, but this hypothesis has not been examined directly in detail. In this study, we profiled immunological changes in the tumor microenvironment and tumor infiltrating lymphocytes (TILs) in a B-RafV600E/Pten-driven murine model of melanoma, after administration of the B-RafV600E small molecule inhibitor PLX4720. In this model, we found that as tumors developed they gradually acquired immunosuppressive features, including accumulation of regulatory T cells (Tregs) and CD11b+/Gr-1+ myeloid cells and loss of Th1 effector functions on CD4+ TILs, such as CD40L and IFN-γ expression. PLX4720 administration promoted development of a more immune stimulatory microenvironment associated with a relative increase in CD40L and IFNγ expression on intratumoral CD4+ TILs and a reduced accumulation of Tregs and CD11b+/Gr-1+ myeloid cells. Strikingly, CD40L or IFNγ blockade compromised the ability of PLX4720 to inhibit melanoma growth. Supporting this result, agonistic CD40 antibody was sufficient to evoke anti-tumor immunity and suppress tumor growth in tumor-bearing mice. Taken together, our results establish the critical role of immune-related changes with key contributions for CD40L and IFNγ signaling in the anti-tumor responses triggered in vivo by B-RafV600E inhibitors.