CMTM6 and gastric cancer: Researches have shown a significant positive association between CMTM6 and PD-L1 expression in gastric cancer, glioma, hepatocellular carcinoma, non-small cell lung cancer, and lung squamous carcinoma (Burr et al., 2017; Mezzadra et al., 2017; Zhang et al., 2021; Ubukata et al., 2021; Tanaka et al., 2019; Peng et al., 2021; Zhao et al., 2020; Guan et al., 2018; Tian et al., 2021; Xiao et al., 2021; Koh et al., 2019; Zugazagoitia et al., 2019; Shang et al., 2020; Wang et al., 2020; Hou et al., 2020; Liu et al., 2021; Yafune et al., 2013; Zhu et al., 2019).