CTLA4 and cancer: Also, they can modulate the expression of immune checkpoint molecules such as PD-1, PD-L1 (programmed cell death ligand 1), PD-L2 (programmed cell death ligand 2), CTLA-4 ), CD47, etc., in several cancers [7,8,9,10,11,12,13,14,15,16,17,18,19].