Promoter methylation of HIN-1 in the progression to esophageal squamous cancer

Abstract

HIN-1 (High in normal-1) is a tumor suppressor gene that is highly expressed in many epithelial tissues, including breast lung, trachea, pancreas, prostrate, and salivary gland. Inactivation of HIN-1 expression by promoter methylation is frequent in many epithelial carcinomas and carcinoma-in-situ, including breast, lung, and nasopharyngeal. Because HIN-1 silencing commences at an early stage of malignant transformation in these tissues, it may be a useful marker for tumor presence. The status of HIN-1 regulation in esophageal cancer has not been previously reported. Thus, we analyzed 18 esophageal cancer cell lines for HIN-1 expression and methylation by reverse transcription PCR (RT-PCR) and methylation specific PCR (MSP). HIN-1 gene silencing and promoter methylation was present in 13 (72%) of the cell lines. Bisulfite-treated sequencing confirmed the methylation status in cell lines and demonstrated dense methylation of HIN-1 throughout the promoter region. Epigenetic changes of HIN-1 were examined throughout the progression of carcinogenesis in esophageal squamous lesions through analysis of archived surgical specimens from patients with normal esophageal mucosa (n=17), grade I dysplasia (n=39), grade II dysplasia (n=12), grade III dysplasia (n=9), and invasive squamous esophageal cancer (n=126). Methylation of HIN-1 was present in 0% of normal mucosa, 31% of grade I dysplasia, 33% of grade II dysplasia, 44% of grade III dysplasia, and 50% of esophageal cancer specimens analyzed. These studies demonstrate HIN-1 silencing is associated with dense promoter region hypermethylation in esophageal cancer and suggest that methylation of HIN-1 is an early event in dysplastic transformation.