CD8A and cancer: The ability of M2-TAMs to enhance tumor invasion and metastasis is not only by preventing tumor cells from being eliminated by CD8+ cytotoxic T cells or by natural killer cells, but also by promoting cancer cell proliferation, stimulating extracellular matrix breakdown, and augmenting epithelial-mesenchymal transition (EMT) [43,44], an event that preludes cancer stem cell phenotypes [45].