ECRG4 and breast cancer: Esophageal cancer-related gene-4 (ECRG4 or C2orf40) has been characterized as a tumor suppressor gene in several types of cancers, such as colorectal cancer (Gotze et al., 2009; Cai et al., 2016), esophageal squamous cell carcinoma (ESCC; Mori et al., 2007; Li et al., 2011; Wen and Hu, 2015), breast cancer (Sabatier et al., 2011; Lu et al., 2013; You et al., 2016; Tang et al., 2019), renal cell carcinoma (Luo et al., 2016), gastric cancer (Deng et al., 2018), and nasopharyngeal carcinoma (Chen J.Y. et al., 2017).