LY6K and esophageal squamous cell carcinoma: LY6K was found to be a molecular marker for non-small-cell lung carcinoma (Ishikawa et al., 2007), head-and-neck squamous cell carcinoma (de Nooij-van Dalen et al., 2003), breast cancer (Kong et al., 2012), bladder cancer (Matsuda et al., 2011), and esophageal squamous cell carcinoma (Zhang et al., 2012).