CLDN6 and breast carcinoma: CLDN6 had been demonstrated abnormal expression and can be a prognostic marker in cancers including ovarian cancer (Wang et al., 2013), endometrial cancer (Kojima et al., 2020), gastric cancer (Kohmoto et al., 2020), breast carcinoma (Liu et al., 2016; Jia et al., 2019), and lung cancer (Micke et al., 2014).