CTLA4 and lung carcinoma: To this aim, we first checked the levels of expression of PD-1, PD-L1 and CTLA-4 on MDA-MB-231 and BT-549 breast cancer cells, and A-549 lung cancer cells by cell ELISA to measure the levels of these ICs exposed on the cell surface and by Western blotting to measure the total amounts of the proteins by using the commercial anti-PD-1, anti-PD-L1 and anti-CTLA-4 mAbs at a concentration of 200 nM (see Figure 1A,B).