CD8A and cancer: CD8+ T cell dependent killing of cancer cells requires appropriate presentation of tumor antigens by MHC, which in humans is human leukocyte antigen (HLA) molecules, resulting in at least three kinds of biomarkers: specific HLA genotype for certain cancer type (115), some kind of HLA alleles having strong antigen presentation ability (116), and high HLA diversity which could provide a large library and are more likely to have appropriate HLA (117).