Digital PCR identifies changes in CDH1 (E-cadherin) transcription pattern in intestinal-type gastric cancer

// Raefa Abou Khouzam 1 , Chiara Molinari 2 , Samanta Salvi 2 , Monica Marabelli 1 , Valeria Molinaro 1 , Donata Orioli 3 , Luca Saragoni 4 , Paolo Morgagni 5 , Daniele Calistri 2 , Guglielmina Nadia Ranzani 1 1 Department of Biology and Biotechnology, University of Pavia, Pavia, Italy 2 Biosciences Laboratory, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy 3 Institute of Molecular Genetics, Consiglio Nazionale delle Ricerche, Pavia, Italy 4 Pathology Unit, Morgagni-Pierantoni Hospital, Forli, Italy 5 Department of General Surgery, Morgagni-Pierantoni Hospital, Forli, Italy Correspondence to: Guglielmina Nadia Ranzani, email: guglielmina.ranzani@unipv.it Keywords: CDH1 transcripts, digital-PCR quantification, intestinal-type gastric cancer, normal gastric mucosa Received: October 04, 2016 Accepted: November 09, 2016 Published: November 16, 2016 ABSTRACT E-cadherin is a cell-cell adhesion protein encoded by CDH1 tumor-suppressor gene. CDH1 inactivating mutations, leading to loss of protein expression, are common in gastric cancer of the diffuse histotype, while alternative mechanisms modulating E-cadherin expression characterize the more common intestinal histotype. These mechanisms are still poorly understood. CDH1 intron 2 has recently emerged as a cis -modulator of E-cadherin expression, encoding non-canonical transcripts. One in particular, CDH1a , proved to be expressed in gastric cancer cell lines, while being absent in the normal stomach. For the first time, we evaluated by digital PCR the expression of CDH1 and CDH1a transcripts in cancer and normal tissue samples from 32 patients with intestinal-type gastric cancer. We found a significant decrease in CDH1 expression in tumors compared to normal counterparts ( P = 0.001), which was especially evident in 76% of cases. CDH1a was detected at extremely low levels in 47% of tumors, but not in normal mucosa. A trend was observed of having less CDH1 in tumors expressing CDH1a transcript. The majority of tumors with both a decrease in CDH1 and presence of CDH1a also showed a decrease in miR-101 expression levels. On the whole, the decrease of CDH1 transcript, corresponding to the canonical protein, and the presence of CDH1a , corresponding to an alternative isoform, are likely to perturb E-cadherin-mediated signaling and cell-cell adhesion, thus contributing to intestinal-type gastric carcinogenesis.