Evaluation Of Desmoglein 1 Alterations In Esophageal Carcinogenesis

Marcela COSTA, Instituto Nacional de Câncer, Brazil

1 Programa de Carcinogênese Molecular, CPQ, Instituto Nacional de Câncer, Rio de Janeiro, Brazil

Esophageal cancer is one of the ten most frequent types of tumors with a five-year survival lower than 20% in Brazil and worldwide. Squamous cell carcinoma (ESCC) is the main histological subtype and is usually diagnosed in late stages, leading to an ineffective treatment. This panorama shows the urgency in understanding the mechanisms that lead to ESCC development. A previous study from our group showed that DNA methylation alterations are common in ESCC and affect pathways like cell adhesion, as evidenced by the promoter hypermethylation of Desmoglein 1 (DSG1), which encodes a desmosomal cadherin. Based on this, the aim of this study is to evaluate the regulation of DSG1 in ESCC. Initially, we treated the ESCC-derived cell line OE21 with the demethylating agent decitabine and observed a dose and time-dependent demethylation of DSG1 promoter by pyrosequencing, which was accompanied by an increase of mRNA expression (RT-qPCR). We also performed the same analyses in tumors and matched normal surrounding tissue from 36 ESCC patients. Our data showed that ESCC samples show a higher methylation and a lower DSG1 expression in comparison with the surrounding tissue. In addition, we analyzed DSG1 protein expression in ESCC and showed that normal esophageal tissue presents a predominant membrane expression. In tumors, we observed different expression patterns, varying from complete expression loss to cytoplasmic staining with a few regions of membrane expression. A new DSG1 isoform, which loses the transmembrane domain, has been predicted, but not yet validated. We were able to detect the mRNA expression of this isoform using specific oligonucleotides and this could explain the cytoplasmic expression observed in ESCC. In conclusion, our data shows an inverse correlation between DSG1 methylation and expression in vitro and in vivo and suggests that the full-length DSG1 is lost in ESCC. Funding source: Ministério da Saúde, CAPES.