COL5A1 and gastric cancer: Previous studies have shown that COL5A1 may affect the development of a variety of cancers, such as breast cancer, gastric cancer, lung adenocarcinoma, oral squamous cell carcinoma and ovarian cancer (Chai et al., 2016; Zhao et al., 2016; Li et al., 2017; Sun et al., 2017; Liu et al., 2018); moreover, the expression level of COL5A1 was an independent prognostic factor (Boguslawska et al., 2016).