Furthermore, using a genetic approach, the authors demonstrated that CD8+ cytolytic T cells, isolated from conditional knockout GSK-3α/β-/- mice, exhibited reduced PD-1 expression and suppressed melanoma tumor growth and pulmonary metastasis to the same extent as PD-1 gene deficiency, thus suggesting the direct role of GSK-3 in the regulation of CTL antitumor function. This evidence concerns the gene PDCD1 and melanoma.