Combination of MAPK inhibition with photothermal therapy synergistically augments the anti-tumor efficacy of immune checkpoint blockade

The combination of MAPK-targeted therapy and immune checkpoint blockade is one of the most promising regimens for patients with advanced melanoma. However, the synergistic efficacy of the combo regimen is still controversial in clinical trials. Here, we report that MAPK inhibition induced T-cell suppression within tumor microenvironment is mediated by attenuation of HSP27/HSP70 and deficiency of neoantigen presentation. To address this problem, we designed a photothermal-responsive on-demand controlled drug release gold nano-system to carry BRAF inhibitor. The nano-system can be specifically delivered into tumor cells rather than T-cells, and effectively transformed the optical energy into heat energy upon laser irradiation. Combination of photothermal and targeted therapy significantly promoted immunogenic cell death and T-cell infiltration. On top of this regimen, systematically administration of PD-1 antibody not only suppressed local-treated tumor but also inhibited abscopal tumor by enhancing generalized immune-related antitumor response. More importantly, the triple-combo regimen could efficiently convert immune "cold" tumors into "hot" ones. In conclusion, our research proves the advantage of photothermal-targeted-immune triple combinatorial regimen in treating tumors which are clinical unresectable multifocal and lack of T-cell infiltration.