CD274 and cancer: Recent studies indicate that cancer cells package PD-L1 into exosomes, exosomal PD-L1 mediates immune escape of tumor cells [54], and circulating exosomal PD-L1 levels can therefore be predictive of the clinical outcomes of anti-PD-1 therapy, ALIX was demonstrated to be required for incorporation of PD-L1 from membrane into exosomes [55].