CTLA4 and neoplasm: One factor that limits the recognition of these neoantigens by T cells is the level of expression of the mutated gene product in cancer cells. In the BALB/c-derived 4T1 mouse model of ICB-refractory metastatic breast cancer, we have previously shown that tumor-targeted radiation therapy (RT) combined with CTLA4 blockade induces CD8+ T cell-mediated regression of irradiated tumors and inhibits lung metastases [2].