PDCD1 and melanoma: In order to clarify the putative role of PD-1 in melanoma growth, Kleffel et al. (123) produced stable Pdcd1 knockdown (KD) and Pdcd1-overexpressing (OE) B16 melanoma lines observing that melanoma-specific Pdcd1-KD and Pdcd1-OE showed a reduction and an increase in melanoma growth, respectively, in immunocompetent C57BL/6 mice respect to controls.