CD27 and cancer: The second group of five upregulated CDs, namely CD27 (a tumor necrosis factor receptor (TNFR), a superfamily member and co-stimulation receptor), semaphoring 7A (SEMA7A), CD108, (which promotes axonal growth and T cell development), TNFSF4 (CD134, OX40 ligand, a co-stimulation receptor), and GGT1[CD224, which promotes clear cell renal cell carcinoma initiation and progression (91)], played roles in co-stimulating T cell immune responses, promoting cancer growth (92), and establishing immune memory (93–97).