CD8A and colorectal carcinoma: In addition to these immune suppressive cells, there are a variety of other immune cell populations found in the tumor microenvironment such as dendritic cells, monocytes, neutrophils, mast cells, NK cells, CD4, CD8 cells, B cells that play diverse roles in promoting tumorigenesis in CRC via degranulation, release of pro-angiogenic factors, growth stimulatory factors (VEGF, FGF2, TNF-α), angiopoitin-1 and tryptase, granzyme B, perforin and upregulation of MHC class 1 and co-stimulatory ligands leading to tumor progression and proliferation [61].