Breast Cancer DNA Methylation Profiles in Cancer Cells and Tumor Stroma: Association with HER-2/neu Status in Primary Breast Cancer

Heidi Fiegl,Elisabeth MüLler-Holzner,Peter W Laird,Christian Marth,Simone Millinger,Martin Widschwendter,Georg Goebel

doi:10.1158/0008-5472.can-05-2508

Abstract

The HER-2/neu gene is amplified and overexpressed in 20% to 30% of invasive breast carcinomas and is associated with increased metastatic potential and less tamoxifen sensitivity. We generated the DNA methylation profiles of 143 human breast tumors and found significant differences in HER-2/neu expression and DNA methylation of five genes. For three of these five genes [PGR (coding for the progesterone receptor), HSD17B4 (coding for type 4 17-beta-hydroxysteroid dehydrogenase, an enzyme that mainly degrades active 17-beta-estradiol into inactive metabolites), and CDH13 (coding for H-cadherin)] a higher prevalence of DNA methylation in HER-2/neu-positive cancers was confirmed in an independent set of microdissected primary breast cancers. DNA methylation was not only present in cancer cells but also in the tumor stroma fraction. Of the isolated fractions in HER-2/neu-positive versus -negative cancers, 27.1% versus 10.5%, respectively, showed DNA methylation of the five genes (P = 0.011, Fisher's exact test). In Her-2++/+++ breast cancers, HSD17B4 mRNA expression was inversely associated with HSD17B4 methylation (P = 0.04). These data support the view that in addition to HER-2/neu-associated signaling, epigenetic changes in cancer as well as in tumor stroma cells might attribute to the specific biological features of HER-2/neu-positive cancers.

Highlights

Breast cancer is the most common malignancy among females in most western countries, where women have an overall lifetime risk of >10% for developing invasive breast cancer [1]
From the initial set of 148 primary breast cancers [16], we used the 143 cases with known HER-2/neu status to correlate with 35 DNA methylation markers with the HER-2/neu immunohistochemical staining intensity for HER-2/neu
CDH13, MYOD1, PGR, and HSD17B4 were positively associated with HER-2/neu expression, whereas BRCA1 was negatively associated with HER-2/neu expression (Fig. 1); methylation of these genes in nonneoplastic breast specimens was either absent or at a low level (Fig. 1)

Summary

Introduction

Breast cancer is the most common malignancy among females in most western countries, where women have an overall lifetime risk of >10% for developing invasive breast cancer [1]. The HER-2/ neu (erbB-2) gene encodes a Mr 185,000 transmembrane glycoprotein that is a member of the epidermal growth factor receptor (EGFR or erbB) family of receptor tyrosine kinases. As the preferred heterodimerization partner among ligand-bound EGFR family members, HER-2/neu mediates lateral signal transduction, resulting in mitogenesis, apoptosis, angiogenesis, and cell differentiation [2]. Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). Doi:10.1158/0008-5472.CAN-05-2508 of invasive breast carcinomas and is associated with increased metastatic potential and decreased overall survival [2, 3]. Letrozole, an aromatase inhibitor, is a more effective neoadjuvant endocrine therapy than tamoxifen for Her-2/neu-positive, estrogen receptor–positive primary breast cancer [5]

Methods

Results

Conclusion