Promoter hypermethylation and quantitative expression analysis of CDKN2A (p14^ARF and p16^INK4a) gene in esophageal squamous cell carcinoma

Background: Abnormal hypermethylation of the CDKN2A (p14^ARF and p16^INK4a) gene can lead to repression of gene expression and contribute to carcinogenesis and tumor progression. Materials and Methods: In esophageal squamous cell carcinoma (ESCC), the promoter methylation of the p14^ARF and p16^INK4a gene was investigated in 38 cases by methylation-specific PCR and the expression of each gene in 18 cases was quantified by real-time quantitative reverse transcription-PCR. Results: Aberrant methylation of p14^ARF and of p16^INK4a was detected in 23 (61%) and 29 (76%) cases, respectively. No relationship was found between clinicopathological variables and p14^ARF or p16 ^INK4a promoter methylation. A statistically significant association between p14^ARF methylation status and mRNA expression was found (p=0.0441). Regarding p14^ARF, a low expression group showed a significantly higher proportion of cases with deep invasion of tumor, lymph node metastasis, and a high TNM stage of disease (p=0.0474, 0.0474, and 0.0441, respectively), and a significantly poor prognosis (p=0.0402). Regarding p16 ^INK4a, no relationship was found among the methylation status, mRNA expression and clinicopathological variables, including survival. Conclusion: Our results suggest that methylation is the predominant mechanism of inactivation of the p14^ARF gene in ESCC. The decrease in p14 ^ARF gene expression associated with invasive and metastatic phenotypes may be significant as an indicator of the malignant potential of human ESCC.