As we studied PD-L1 expression in NSCLC, we also hypothesized that the PD-L1 molecule in cancer cells would eventually flow into the circulation, given that it is degraded into a soluble form by matrix metalloproteinase-mediated proteolytic cleavage [11, 12] and presumably through cytotoxicity-mediated antitumor immune responses. Here, CD274 is linked to cancer.