Expression and promoter methylation of SIX2 gene in peripheral blood of pediatric patients with nephroblastoma

Abstract

To explore the transcriptional expression and promoter methylation status of SIX2 gene in peripheral blood of pediatric children with nephroblastoma and discuss their clinicopathological correlations. Approved by the hospital ethics committee, peripheral blood samples were collected from 45 children with Wilms' tumor(case group) at the Department of Pediatric Surgery, First Affiliated Hospital, Zhengzhou University from October 2008 to January 2012. And another 15 pediatric cases gender-and-age matched, were selected as the control group (excluding cancer and other malignant diseases). The real-time quantitative (qRT)-PCR and methylation-specific PCR (MSP) were used to detect the mRNA expression level and methylation status of SIX2 gene.t or χ(2) test were used. Then analyzed their clinicopathological correlations in the case group and how SIX2 gene methylation affected its transcription. Relative quantity(RQ) of SIX2 mRNA in the case group was higher than that of the control group (1.93 ± 1.10 vs 0.57 ± 0.39, t = 5.354, P = 0.000). There were 8 SIX2 gene methylation-positive cases in the case group versus 12 cases in the control group. And the methylation positive ratio was extremely lower in the case group (χ(2) = 19.600, P = 0.000). RQ values in the case group was associated with tumor size, clinical stage, pathological type, lymph node metastasis, treatment and outcome (all P < 0.05). RQ values in the methylated group was lower than that of the unmethylated group both in case and control group (1.35 ± 0.44 vs 1.95 ± 1.15, 0.43 ± 0.29 vs 1.13 ± 0.20, t = 2.459 and 3.896, P = 0.020 and 0.002) . RQ values of case group was higher than that of the control group in methylated group (t = 5.624, P = 0.000) . No statistical significance existed in RQ values between the case and control groups of unmethylated group (t = 1.222, P = 0.229) . A close correlation between SIX2 low methylation and high mRNA expression in blood suggests that aberrant promoter methylation is possibly one of gene expression regulations, and may be correlated with the occurrence and development of Wilms' tumor. And SIX2 gene in methylated Wilms' tumor may play the role of oncogenes. A negative correlation exists between the overexpression in transcriptional level and its methylation status.