VSIR and cancer: Recently, PD-1H was reported to be highly expressed in various human cancers, including prostate cancer (Gao et al., 2017), non-small cell lung cancer (Villarroel-Espindola et al., 2018), colorectal carcinoma (Xie et al., 2018), ovarian and endometrial cancer (Mulati et al., 2019), esophageal adenocarcinoma (Loeser et al., 2019), and epithelioid malignant pleural mesothelioma (Muller et al., 2020); however, limited data about PD-H expression in ESCC have been reported.