IGF2, a maternally imprinted foetal growth factor gene, is implicated in many childhood tumours including hepatoblastoma (HB); however, the genetic and epigenetic alterations have not comprehensively been studied. We analysed the methylation status of the H19 differentially methylated region (DMR), loss of heterozygosity (LOH) and allelic expression of IGF2 in 54 HB tumours, and found that 12 tumours (22%) with LOH, 9 (17%) with loss of imprinting (LOI) and 33 (61%) with retention of imprinting (ROI). Biallelic and monoallelic IGF2 expressions correlated with hypermethylation and normal methylation of H19 DMR, respectively, in two tumours with LOI and seven tumours with ROI. Quantitative RT -PCR analysis showed minimal expression of H19 mRNA and substantial expression of IGF2 mRNA in tumours with LOH or LOI, and substantial expression of both H19 and IGF2 mRNAs in tumours with ROI. Increased IGF2 expression with predominant embryonic P3 transcript was found in the majority of HBs with ROI and foetal livers. In contrast to the earlier reports, our findings suggest that the disruption of the enhancer competition model reported in Wilms' tumour may also occur in HB. Both frequencies of LOH and LOI seem to be lower in HB than in Wilms' tumour, reflecting the different tissue origins.

Despite the progress of therapy, outcomes of advanced hepatoblastoma patients who are refractory to standard preoperative chemotherapy remain unsatisfactory. To improve the mortality rate, novel prognostic markers are needed for better therapy planning. We examined the methylation status of 13 candidate tumor suppressor genes in 20 hepatoblastoma tumors by conventional methylation-specific PCR (MSP) and found hypermethylation in 3 of the 13 genes. We analyzed the methylation status of these 3 genes (RASSF1A, SOCS1 and CASP8) in 97 tumors and found hypermethylation in 30.9, 33.0 and 15.5%, respectively. Univariate analysis showed that only the methylation status of RASSF1A but not the other 2 genes predicted the outcome, and multivariate analysis showed a weak contribution of RASSF1A methylation to overall survival. Using quantitative MSP, we found RASSF1A methylation in 44.3% of the 97 tumors. CTNNB1 mutation was detected in 67.0% of the 97 tumors. While univariate analysis demonstrated RASSF1A methylation, CTNNB1 mutation and other clinicopathological variables as prognostic factors, multivariate analysis identified RASSF1A methylation (p 5 0.043; relative risk 9.39) and the disease stage (p 5 0.002; relative risk 7.67) but not CTNNB1 mutation as independent prognostic factors. In survival analysis of 33 patients in stage 3B or 4, patients with unmethylated tumor had better overall survival than those with methylated tumor (p 5 0.035). RASSF1A methylation may be a promising moleculargenetic marker to predict the treatment outcome and may be used to stratify patients when clinical trials are carried out. ' 2008 Wiley-Liss, Inc.Key words: RASSF1A; CTNNB1; quantitative MSP; hepatoblastoma; prognostic factor Hepatoblastoma is a rare malignant neoplasm of the liver, with an incidence of 0.5-1.5 per million children. 1 Remarkable progress in clinical outcome has been achieved in the past 20 years due to advances in chemotherapy and surgical procedures; however, the mortality rate remains 20-30% and treatment results in patients in advanced stages who are refractory to standard preoperative chemotherapy regimens are unsatisfactory. 2,3 To improve the mortality of these patients, innovative treatment and potent prognostic markers for better therapy planning are needed. The present clinical factors predicting outcome include the level of alpha-feto protein, histology, disease stage and growth pattern of the tumor. 2-4 Chromosomal gains of 2q, 8q and 20 and high expression of telomerase or PLK1 were shown to be moleculargenetic markers predicting poor outcome 5-8 ; however, none have been proven to be independent prognostic factors by multivariate analysis.We previously reported that RASSF1A (RAS association domain family protein 1) methylation, found in 39% of 39 hepatoblastoma tumors, was correlated with poor outcome by univariate analysis. 9 Nevertheless, the article had some limitations that the number of tumors was not enough, the method used to detect the hypermethylation was suboptimal, and the prognostic signifi...

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