Promoter methylation and protein expression of tumor suppressor candidate 1 gene in adolescent papillary thyroid carcinoma

Abstract

Objective To study the relationship between status of methylation of tumor suppressor candidate 1 gene(TUSC1) promoter and expression of its protein in adolescent papillary thyroid carcinoma(PTC). Methods Forty cases of adolescent PTC were chosen and the corresponding para carcinoma tissues were taken from July 2010 to December 2013 in the First Affiliated Hospital of Zhengzhou University surgical specimens of the thyroid gland and were confirmed by pathology.Male 12 cases, female 28 cases, median age 14 (10-18) years old.Tumor node metastasis (TNM) stage Ⅰ-Ⅱ 13 cases, Ⅲ-Ⅳ stage 27 cases; grade Ⅰ in 15 cases, grade Ⅱ in 25 cases; lymph node metastasis in 22 cases, 18 cases were negative.Methylation-specific polymerase chain reaction (MSP) and Western blot were applied respectively to examine the methyaltion of TUSC1 gene promoter and its protein expression of 40 samples of adolescent PTC and their matched adjacent non-cancerous epithelium. Results The results of MSP revealed that there was no methylation of TUSC1 gene promoter in adjacent non-cancerous epithelium, while in the adolescent PTC, the hyper-methylation rate was 60%(24/60 cases, χ2=34.28, P<0.05). In additional, it was related to the TNM stage, pathological grade and lymph node metastasis (χ2=4.862, 7.111, 5.625, all P<0.05). The result of Western blot revealed that the positive expression rate of TUSC1 protein was 100% in adjacent non-cancerous epithelium and 30%(12/40 cases) in adolescent PTC (χ2=14.118, P<0.05), which was related to the TNM stage, pathological grade and lymph node metastasis (χ2=5.215, 6.222, 5.079, all P<0.05). There was distinct correlation between methylation of TUSC1 gene promoter and the protein expression (r=-0.84, P<0.05). Conclusions Methylation of promoter might be one of the important mechanisms of inactivation of TUSC1 gene, and might play an important role in carcinogenesis and progression of adolescent PTC. Key words: Papillary thyroid carcinoma; Methylation; Adolescent; Tumor suppressor candidate 1 gene