Novel Interaction In Epithelial-Mesenchymal Transition (EMT) Pathway Of Esophageal Squamous CellCarcinoma

TWIST1 is a highly conserved bHLH transcription factor. It activates a cell migration-invasionprogram called epithelial mesenchymal transition (EMT). As a potent oncogene, TWIST1allows epithelial cells to convert to a mesenchymal fate while avoiding cell death. MAGEA4is a germ-line gene belongs to a large group of cancer testis antigens (CTAs). Aberrantexpression of MAGEA4 is frequently observed in a large variety of tumors and relatively littleis known about the mechanisms of this process. Since MAGEA4 and TWIST1 haveoncogenic roles in tumorigenesis, progression, and aggressiveness of esophagealsquamous cell carcinoma (ESCC), our aim in this study was to elucidate the possible linkagebetween these genes in the disease. Expression of TWIST1 and MAGEA4 mRNA wasanalyzed in 40 ESCC patients. ESCC cell line, KYSE30, was transducted with preparedretroviral particles containing TWIST1. Gene expression analysis was performed on stabletransducted cells using Real-time PCR and western blotting. Chromatin immunoprecipitation(CHIP) was also carried out to confirm functional study. TWIST1 and MAGEA4 wereoverexpressed in majority of ESCC samples in significant correlation with each other as wellas lymph node metastasis and stage of tumor progression. Enforced expression of TWIST1using retroviral particles up-regulated MAGEA4 expression in KYSE-30 cells nearly 6 folds incomparison with control cells. CHIP analysis showed significant attachment of TWIST1protein to the MAGEA4 promoter sequence in transducted cells compared to the control.MAGEA4 is a highly expressed CTA in majority of ESCC correlating with different indices ofpoor prognosis. This study proposes new mechanism for regulation of MAGEA4 expressionin cancer cells. Regulatory role of TWIST1 on MAGEA4 may highlight the probable crosstalkbetween EMT process and CTAs expression in ESCC and reveal the possible coordinationof these proteins in aggressiveness and metastasis of the disease.

Keywords:

TWIST1 , MAGEA4 , Epithelial-Mesenchymal Transition , Cancer Testis Antigens , Esophageal Squamous Cell Carcinoma