PDCD1 and neoplasm: In addition, the aberrant vascular architecture, elevated interstitial fluid pressure, and compact extracellular matrix (ECM) in tumor tissues hamper the tumor accumulation of anti-PD-1/PD-L1 antibody and subsequent deep penetration into tumor parenchyma9,10, which limits the therapeutic effects of anti-PD-1/PD-L1 antibody.