Notch signaling is an important cellular pathway which affects the development and function of many organs. It plays critical roles in maintaining of progenitor stem cell population as well as balancing cell proliferation, survival, differentiation and apoptosis. It has been shown that notch signaling is aberrantly activated during the carcinogenesis of a variety of human cancers. In this study we aimed to explore activation of this signaling pathway in esophageal squamous cell carcinoma (ESCC) through expressional analysis of notch signaling target genes. The mRNA expression of HEY1 and HEY2 was comparatively analyzed by real-time PCR in tumor and related margin normal tissues of 50 ESCC patients. Comparative quantitative real-time PCR indicates the overexpression of HEY1 and HEY2 in 54 and 30% of ESCC samples, respectively. Overexpression of HEY1 was significantly associated with stage of the tumor (p = 0.048) and tumor location (p = 0.008). HEY2 overexpression was also significantly correlated to node metastasis of tumor cells (p = 0.043). Overexpression of HEY1 and HEY2 in ESCC is correlated to different indices of poor prognosis and it is extrapolated that such overexpression is important in progression and development of ESCC tumorigenesis. To the best of our knowledge, this is the first report introducing aberrant activation of notch signaling target genes in ESCC, where it plays roles in development and progression of the malignancy and may be considered in therapeutic modalities to restrict ESCC progression.

Although we have not observed any significant correlation between the HES1 expression and notch activation in ESCC, this study is the first report that elucidated the HES1 underexpression in ESCC and revealed its correlation with the invasiveness of ESCC.