Promoter methylation‑associated silencing of p27kip1 gene with metastasis in esophageal squamous cell carcinoma.

The aim of the present study was to determine the frequency of p27kip1 promoter methylation in esophageal squamous cell carcinoma (ESCC). The methylation status of the p27kip1 promoter was analyzed by methylation‑specific polymerase chain reaction (MSP) in 50 ESCC and matched non‑tumor tissues. Cell lines were treated with the demethylation agent 5‑aza‑2'‑deoxycytidine (5‑Aza‑CdR) and p27kip1 mRNA expression was detected by quantitative polymerase chain reaction. p27kip1 methylation was found in 36% (18/50) of ESCC patients, but only in 12% (6/50) of the corresponding non‑tumor tissues (P=0.005). There were statistically significant associations between the presence of methylation and tumor metastasis (P=0.002). The p27kip1 mRNA was lower in ESCC compared with non‑tumor tissues (mean ± standard deviation, ‑0.886±3.298 vs. 0.988±0.257; P=0.0033). Furthermore, a significant association was identified between the methylation status of the p27kip1 promoter and p27kip1 mRNA expression in the tissue (P<0.01). Thus, demethylation by 5‑Aza‑CdR was capable of inducing p27kip1 mRNA expression in esophageal cancer cell lines. The high promoter methylation of p27kip1 is a common phenomenon in ESCC, which may be an important mechanism of silencing p27kip1 mRNA expression.