ID1 and neoplasm: Here we describe, for the first time, the synergistic effect of the combined blockade of Id1 and PD-1 in KRAS-driven LUAD murine models and the immune mechanisms that may be involved, confirming previous studies showing the immunosuppressive role of Id1. The rationale behind this approach is that combined treatment may partially reverse the immunosuppressive tumor microenvironment, favor the immune infiltration of tumors, and thereby exert a relevant antitumor activity.