The HER2-miR125a5p/miR125b loop in gastric and esophageal carcinogenesis

A subset of gastric (intestinal-type) and esophageal (Barrett) adenocarcinoma features HER2 protein overexpression. Consistent evidence demonstrates that microRNAs have a major role in HER2 (dys)regulation. MiR-125a-5p and miR125b expressions were tested in the spectrum of lesions in the gastroesophageal carcinogenic cascade, also correlating miR-125a-5p/125b levels with HER2 status. MiR-125a-5p and miR-125b expression (quantitative reverse transcriptase polymerase chain reaction [qRT-PCR]) and HER2 status (immunohistochemistry [IHC] and chromogenic in situ hybridization [CISH]) were assessed in a series of 90 biopsy samples spanning the whole histologic spectrum of gastric and esophageal carcinogenesis. To support the obtained results, the qRT-PCR levels of microRNAs and their expression (in situ hybridization) were tested in an adjunctive series of gastric and esophageal adenocarcinoma, including (IHC/CISH validated) HER2-negative and HER2-positive cases. Both miR-125a-5p and miR-125b levels were significantly down-regulated throughout the gastric and esophageal carcinogenic cascade. HER2 status (IHC and CISH) correlated inversely with miR-125 expression (qRT-PCR and in situ hybridization). Dysregulation of miR-125a-5p/125b and HER2 is an early event in the gastric (intestinal-type) and esophageal (Barrett) oncogenesis. In both oncogenetic cascades, miR-125 expression correlates inversely with HER2 status. MiR-125a-5p/125b can be considered among the therapeutic targets in HER2-positive esophageal and gastric adenocarcinoma.