CD8A and cancer: COX-2/PGE2 axis contributes to the formation of the inflammatory microenvironment in the tumor tissues, resulting in proliferation, invasion, epithelial-mesenchymal transition (EMT), cancer cell stemness, and inhibition of apoptosis via regulating the function of macrophages, cancer-associated fibroblasts, CD8+ T cells, and myeloid-derived suppressor cells (MDSCs) (Fig. 2) [39], [40], [41], [42], [43], [44], [45], [46], [48], [49], [50], [51].