This review examined the involvement of CD8+ T cells in tumors such as neurologic tumors [22–24], melanomas [25–28], squamous cell carcinoma [29–31], hepatocellular carcinoma [32, 33], colorectal carcinoma [34–36], lung carcinoma [37, 38], breast carcinoma [39, 40]. The gene discussed is CD8A; the disease is hepatocellular carcinoma.