LY6K and esophageal squamous cell carcinoma: We previously reported that three novel HLA-A24-restricted immunodominant peptides, which were derived from three different Cancer-Testis antigens, TTK protein kinase (TTK), lymphocyte antigen 6 complex locus K (LY6K), and insulin-like growth factor (IGF)-II mRNA binding protein 3 (IMP-3), were promising targets for cancer vaccination for ESCC patients [6] because of their specific and frequent expression in tumor tissues [6-12].