They demonstrated that in an immune-free condition, knockdown/overexpression of PD-1 in tumor cells altered AKT and ERK1/2 phosphorylation dependent on PD-L1, while Nivolumab and Pembrolizumab administration activated AKT and ERK1/2 signaling to promote the growth of PD-1+ lung cancer cells and even colon cancer cells. Here, PDCD1 is linked to lung cancer.