More importantly, melanoma patients could potentially benefit from the concomitant administration of vitamin D and ICIs based on the following observations [106]: (1) Vitamin D has an anti-proliferative effect in experimental melanoma models [61], which could strengthen the cytotoxic activity of T cells stimulated by ICIs; (2) Vitamin D was shown to upregulate the expression of PD-L1 [60], which was positively correlated with the response to ICIs in melanoma [116]. This evidence concerns the gene CD274 and melanoma.