Protein expression and promoter methylation of the deleted in liver cancer-1 gene in papillary thyroid carcinoma

Abstract

Objective To investigate the protein expression and promoter methylation of deleted in liver cancer-1 (DLC1) gene in papillary thyroid carcinoma (PTC) and pericarcinomatous thyroid tissue (PCTT),and its clinical significance.Methods Methylation-specific polymerase chain reaction (MSP),immunohistochemistry (IHC) and Western blotting were empolyed to detect the methylation status of DLC1 gene promoter and its protein expression in 40 PTC and PCTT samples.The location of DLC1 protein expression was examined by IHC,and the differential expression of DLC1 protein by Western blotting,respectively.Results By immunohistochemical technique,DLCl was expressed in the cytoplasm of thyrocytes.The positive expression rate of DLC1 protein in PCTT and PTC was 90％ (36/40) and 47.5％ ％(19/40),respectively (x2 =26.36,P ＜ 0.05).The absorbance (A) value of DLC1 protein confirmed was 0.18 ±0.12 in PTC versus 0.33 ±0.14 in PCTT (P ＜0.05).In PTC,the positive expression rate of DLC1 protein was correlated with the tumor size,lymph node metastasis and the TNM stage (x2 =18.050,15.132,7.020,P ＜ 0.05).The methylation rate of DLC 1 gene in PCTT and PTC was 12.5 ％ (5/40) and 40.0％ (16/40) respectively (x2 =7.813,P ＜0.05).The methylation of DLC1 gene in PTC was correlated with tumor size (x2 =12.857,P ＜0.05).Futhermore,there was distinct correlation between methylation of DLC1 gene promoter and its protein expression (r =0.526,P ＜ 0.05).Conclusion Methylation of promoter may be one of the important inactivating factors of DLC1 gene,and it plays an important role in the carcinogenesis and progression of PTC. Key words: Papillary thyroid carcinoma; Pericarcinomatous thyreoid tissue; Deleted in liver cancer-1 gene ; Methylation