Clinical studies revealed that PD-L1-overexpressed tumors showed better clinical responses compared to PD-L1 low-expressing tumors in several malignancy types3,4, suggesting that PD-L1 overexpression in tumor tissues is a potential biomarker for ICI targeting PD-1/PD-L1; however, an objective response was seen in both PD-L1 negative and positive MPM2, implying that the MPM tumor immune escape mechanism is complicated. The gene discussed is PDCD1; the disease is neoplasm.