It has been well acknowledged that cancer patients may present aberrant changes in the T lymphocyte subsets in the peripheral blood, which was reported to be related to the immune response imbalance due to imbalance of CD3+, CD4+, and CD8+ cells upon onset of malignant lesions, particularly the disturbance of the CD4+/CD8+ balance [28, 33]. This evidence concerns the gene CD8A and cancer.