PGPEP1 and carcinoma of esophagus: They included pannexin 1 (a major ATP release and nucleotide eflux channel; Chekeni et al., 2010; Elliott et al., 2009), pyroglutamyl-peptidase I (PGPEP1; an exopeptidase; Cummins and O'Connor, 1998) and lymphocyte antigen 6K (LY6K; a biomarker of lung and esophageal carcinomas; Ishikawa et al., 2007).