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Volume 10 Supplement 2

Breast Cancer Research 2008

NRG1is frequently silenced by methylation in breast cancers and is a strong candidate for the 8p tumour suppressor gene

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Background

It has long been suspected that there is an important breast cancer tumour suppressor gene on the short arm of chromosome 8, 8p, and our array CGH data suggest that it may be close to NRG1 [1]. NRG1 encodes growth factors that bind to tyrosine kinases ErbB3 and ErbB4, and can both stimulate cell proliferation and apoptosis. NRG1 is also quite frequently broken by chromosome translocations [2].

Methods and results

By quantitiative PCR, NRG1 expression was repressed or abolished in many breast cancer cell lines and tumours as compared with normal breast. Methylation analysis by sequencing or pyrosequencing bisulphite-treated DNA showed striking DNA methylation at a CpG island in NRG1, which is correlated with an absence of NRG1 transcripts. Treatment of cancer cell lines with 5-aza-2-deoxycytidine reactivated the expression of NRG1 by 7 to 100 times. NRG1 was also methylated in tumour tissue samples while it was not in uncultured normal breast epithelium. Knocking down NRG1 expression by siRNA led to an increase in net cell proliferation.

Conclusion

NRG1 could be the 8p tumour suppressor gene. It is located in the right place. It is silenced by methylation or other mechanisms in many breast cancer cell lines and tumours. Functionally, NRG1 expression is antiproliferative – shown both by our siRNA experiments and older work that showed expression to be proapoptotic to breast cancer cell line MCF7 [3].

References

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    Pole JC, Courtay-Cahen C, Garcia MJ, Blood KA, Cooke SL, Alsop AE, Tse DM, Caldas C, Edwards PA: High-resolution analysis of chromosome rearrangements on 8p in breast, colon and pancreatic cancer reveals a complex pattern of loss, gain and translocation. Oncogene. 2006, 25: 5693-5706. 10.1038/sj.onc.1209570.

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    Huang HE, Chin SF, Ginestier C, Bardou VJ, Adelaide J, Iyer NG, Garcia MJ, Pole JC, Callagy GM, Hewitt SM, Gullick WJ, Jacquemier J, Caldas C, Chaffanet M, Birnbaum D, Edwards PA: A recurrent chromosome breakpoint in breast cancer at the NRG1/neuregulin 1/heregulin gene. Cancer Res. 2004, 64: 6840-6844. 10.1158/0008-5472.CAN-04-1762.

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    Grimm S, Weinstein EJ, Krane IM, Leder P: Neu differentiation factor (NDF), a dominant oncogene, causes apoptosis in vitro and in vivo. J Exp Med. 1998, 188: 1535-1539. 10.1084/jem.188.8.1535.

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Acknowledgements

Supported by Breast Cancer Campaign and also Cancer Research UK and the Ludwig Institute for Cancer Research.

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Chua, Y., Ito, Y., Pole, J. et al. NRG1is frequently silenced by methylation in breast cancers and is a strong candidate for the 8p tumour suppressor gene. Breast Cancer Res 10, P11 (2008) doi:10.1186/bcr1895

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Keywords

  • Breast Cancer
  • Breast Cancer Cell Line
  • Normal Breast
  • Breast Cancer Cell Line MCF7
  • Stimulate Cell Proliferation