In addition, naïve CD8+ T cells can differentiate into a population of effector T (Teff) cells, followed by the release of enzymes and toxins and executing killing functions against infections and cancers, while the population of CD8+ memory T (Tmem) cells have the ability to maintain long-term rapid response to the reintroduction of relevant pathogens after an infection has been eliminated. This evidence concerns the gene CD8A and cancer.