PCDH17 and esophageal squamous cell carcinoma: The protocadherin 17 (PCDH17) gene, a member of the protocadherin family, is frequently methylated and associated with poor prognosis in various cancer types, including esophageal squamous cell carcinoma (ESCC),6 urological cancer,7 gastric cancer,8 and nasopharyngeal cancers.9 In a previous study, we demonstrated that PCDH17 was silenced in most CRC cell lines and that restoring PCDH17 expression reduced tumor cell growth.10 Therefore, PCDH17 is a potential tumor suppressor in CRC.