CD8A and neoplasm: Both acquired immune cells, especially cytotoxic CD8+ T cells (CTLs), and innate immune cells such as NK cells play important roles in the eradication of tumor cells.99, 100 On the other hand, Treg cells and myeloid‐derived suppressor cells (MDSCs) interfere with the antitumor immunity.101 PD‐L1 and/or PD‐L2 expressed on some tumor cells also inhibit antitumor immunity by interacting with PD‐1 on cytotoxic T cells.101 In the course of tumor development, cancer cells frequently metastasize and relocate to other organs through nearby blood vessels.