Two members of the SLC15 family of proton-coupled peptide transporters, PepT1 (SLC15A1) and PepT2 (SLC15A2) exhibit remarkable ligand promiscuity, and are known to transport many different drug molecules, including angiotensin-converting enzyme inhibitors, beta-lactam antibiotics, an N-methyl-d-aspartate receptor antagonist PD-15874 and 5-aminolevulinic acid, currently being evaluated as a treatment for bladder and oesophageal cancer [11–13]. This evidence concerns the gene SLC15A2 and carcinoma of esophagus.