Research article

Promoter methylation-associated loss of ID4 expression is a marker of tumour recurrence in human breast cancer

Erik Noetzel¹ , Jürgen Veeck¹ , Dieter Niederacher² , Oliver Galm³ , Felicitas Horn⁴ , Arndt Hartmann⁵ , Ruth Knüchel¹ and Edgar Dahl¹

¹  Molecular Oncology Group, Institute of Pathology, University Hospital of the RWTH Aachen, Aachen, Germany

²  Department of Gynaecology and Obstetrics, Heinrich-Heine University, Düsseldorf, Germany

³  Medical Clinic IV, University Hospital of the RWTH Aachen, Aachen, Germany

⁴  Department of Gynaecology and Obstetrics, University of Regensburg, Regensburg, Germany

⁵  Institute of Pathology, University of Erlangen, Erlangen, Germany

author email corresponding author email

BMC Cancer 2008, 8:154doi:10.1186/1471-2407-8-154

Published:	30 May 2008

Abstract

Background

Inhibitor of DNA binding/Inhibitor of differentiation 4 (ID4) is a critical factor for cell proliferation and differentiation in normal vertebrate development. ID4 has regulative functions for differentiation and growth of the developing brain. The role of ID1, ID2 and ID3 are expected to be oncogenic due to their overexpression in pancreatic cancer and colorectal adenocarcinomas, respectively. Aside from these findings, loss of ID3 expression was demonstrated in ovarian cancer. The aim of the present study was to reveal the factual role of ID4 in carcinogenesis in more detail, since its role for the pathogenesis of human breast cancer has been discussed controversially, assigning both oncogenic and tumour suppressive functions.

Methods

ID4 promoter methylation, ID4 mRNA expression and ID4 protein expression were analysed in primary human breast cancer specimens using methylation-specific PCR (MSP) (n=170), semiquantitative realtime RT-PCR (n=46) and immunhistochemistry (n=3), respectively. In order to demonstrate a functional association of ID4 promoter methylation with its gene silencing, we performed DNA demethylation analysis with four human breast cell lines using MSP and semiquantitative realtime RT-PCR. In addition, we performed correlations of ID4 promoter methylation with ID4 mRNA and ID4 protein expression in matched samples of breast tumour and corresponding normal tissue. We carried out statistical analyses in order to find correlations between ID4 promoter methylation and clinicopathological parameters.

Results

Frequent ID4 promoter methylation was observed in primary breast cancer samples (69%, 117/170). We found a tight correlation (P<0.0001) between ID4 promoter methylation and loss of ID4 expression in primary breast cancer 3 specimens. Demethylating treatment with breast cancer cell lines was associated with clear ID4 mRNA re-expression. Tumours with ID4 promoter methylation showed distinct loss of ID4 expression on both transcription and protein level. Interestingly, ID4 promoter methylation was a factor for unfavourable recurrence-free survival (P=0.036) and increased risk for lymph node metastasis (P=0.030).

Conclusion

ID4 is indeed a novel tumour suppressor gene in normal human breast tissue and is epigenetically silenced during cancer development, indicating increased risk for tumour relapse. Thus, ID4 methylation status could serve as a prognostic biomarker in human breast cancer.