Combination ICI therapy, such as the combination of anti–CTLA-4 and anti–PD-1, aims to recruit T cells into tumors and then prevent them from being “turned off.” CTLA4 blockade induces frequent increases in intratumoral T cell infiltration beyond its clinical response rate (Zhou et al., 2018a), and concurrent ipilimumab plus nivolumab in melanoma has shown promise (Long et al., 2017; Martin et al., 2018b). The gene discussed is CTLA4; the disease is melanoma.