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Loss of imprinting of IGF2 correlates with hypermethylation of the H19 differentially methylated region in hepatoblastoma.

Honda S, Arai Y, Haruta M, Sasaki F, Ohira M, Yamaoka H, Horie H, Nakagawara A, Hiyama E, Todo S, Kaneko Y - Br. J. Cancer (2008)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Cancer Diagnosis, Saitama Cancer Center, Research Institute for Clinical Oncology, 818 Komuro, Ina, Saitama 362-0806, Japan.

ABSTRACT
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.

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(A) Representative data of RT–PCR analysis of P3 transcripts. (B) Expression levels of P3 transcripts (upper lane) and total IGF2 mRNA (lower lane) are plotted in 20 tumours, in 2 cell lines, in foetal liver tissues and normal liver tissues (a mean value of 3 samples). Tumours are arranged in order by total levels of IGF2 mRNA. Numbers below X axis indicate the tumour number. (C) Correlation between levels of P3 transcript (X axis) and total IGF2 mRNA (Y axis).
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fig3: (A) Representative data of RT–PCR analysis of P3 transcripts. (B) Expression levels of P3 transcripts (upper lane) and total IGF2 mRNA (lower lane) are plotted in 20 tumours, in 2 cell lines, in foetal liver tissues and normal liver tissues (a mean value of 3 samples). Tumours are arranged in order by total levels of IGF2 mRNA. Numbers below X axis indicate the tumour number. (C) Correlation between levels of P3 transcript (X axis) and total IGF2 mRNA (Y axis).

Mentions: Because the IGF2 gene has four kinds of promoters, promoter-specific IGF2 transcripts were analysed to determine the usage of each promoter. Representative results of the P3 transcript are shown in Figure 3A. All 20 tumours showed undetectable or lower levels of P1 transcripts than 3 normal liver tissues. The levels of P2, P3 and P4 transcripts were higher in 13, 15 and 10 of the 20 tumours, respectively, than those of normal liver tissues. Polymerase chain reaction cycle numbers to obtain visible levels of PCR products were 40 for P2 transcripts, 30 for P3 transcripts and 35 for P4 transcripts, indicating that the amounts of P3 transcripts were high, those of P2 transcripts were low and those of P4 transcripts were intermediate. The Spearman correlation coefficient analysis showed that the expression levels of the P2, P3 and P4 transcripts correlated with the levels of total IGF2 mRNA (P2, rS=0.730; P3, rS=0.773 and P4, rS=0.646) (Figure 3B and C; data for the P2 and P4 transcripts are not shown).


Loss of imprinting of IGF2 correlates with hypermethylation of the H19 differentially methylated region in hepatoblastoma.

Honda S, Arai Y, Haruta M, Sasaki F, Ohira M, Yamaoka H, Horie H, Nakagawara A, Hiyama E, Todo S, Kaneko Y - Br. J. Cancer (2008)

(A) Representative data of RT–PCR analysis of P3 transcripts. (B) Expression levels of P3 transcripts (upper lane) and total IGF2 mRNA (lower lane) are plotted in 20 tumours, in 2 cell lines, in foetal liver tissues and normal liver tissues (a mean value of 3 samples). Tumours are arranged in order by total levels of IGF2 mRNA. Numbers below X axis indicate the tumour number. (C) Correlation between levels of P3 transcript (X axis) and total IGF2 mRNA (Y axis).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2600691&req=5

fig3: (A) Representative data of RT–PCR analysis of P3 transcripts. (B) Expression levels of P3 transcripts (upper lane) and total IGF2 mRNA (lower lane) are plotted in 20 tumours, in 2 cell lines, in foetal liver tissues and normal liver tissues (a mean value of 3 samples). Tumours are arranged in order by total levels of IGF2 mRNA. Numbers below X axis indicate the tumour number. (C) Correlation between levels of P3 transcript (X axis) and total IGF2 mRNA (Y axis).
Mentions: Because the IGF2 gene has four kinds of promoters, promoter-specific IGF2 transcripts were analysed to determine the usage of each promoter. Representative results of the P3 transcript are shown in Figure 3A. All 20 tumours showed undetectable or lower levels of P1 transcripts than 3 normal liver tissues. The levels of P2, P3 and P4 transcripts were higher in 13, 15 and 10 of the 20 tumours, respectively, than those of normal liver tissues. Polymerase chain reaction cycle numbers to obtain visible levels of PCR products were 40 for P2 transcripts, 30 for P3 transcripts and 35 for P4 transcripts, indicating that the amounts of P3 transcripts were high, those of P2 transcripts were low and those of P4 transcripts were intermediate. The Spearman correlation coefficient analysis showed that the expression levels of the P2, P3 and P4 transcripts correlated with the levels of total IGF2 mRNA (P2, rS=0.730; P3, rS=0.773 and P4, rS=0.646) (Figure 3B and C; data for the P2 and P4 transcripts are not shown).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Cancer Diagnosis, Saitama Cancer Center, Research Institute for Clinical Oncology, 818 Komuro, Ina, Saitama 362-0806, Japan.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus