CD274 and non-small cell lung carcinoma: The expression of ligand of programmed death-1 (PD-1; i.e., PD-L1) and/or PD-L2 was considered as one of the most important biomarkers of PD-1 inhibitors; a high expression of PD-L1 could be a predictive factor of response to anti-PD-1 therapy, and in some malignancies such as non-small cell lung cancers, the evaluation of PD-L1 expression was inseparably linked to the indication of immunotherapy [120,121].