CD8A and non-small cell lung carcinoma: Previous studies on non-small cell lung cancer (NSCLC) and chronic viral infections reported that high expression of PD-1 on the surface of activated CD8+ T cells restrained transcriptional coactivator peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1-α), a critical gene transcriptional regulator of mitochondrial metabolism and biogenesis, leading to mitochondrial depolarization accompanied with the reduced number and length of cristae, and a trend towards ROS accumulation.