Epithelial and stromal microRNA signatures of columnar cell hyperplasia linking Let-7c to precancerous and cancerous breast cancer cell proliferation.

Sofie Björner,Anita Ringberg,Crispin J Miller,Paul A Fitzpatrick,Craig Allred,Göran Landberg,Håkan Olsson,Anthony Howell,Yaoyong Li,Håkan Axelson

doi:10.1371/journal.pone.0105099

Abstract

Columnar cell hyperplasia (CCH) is the earliest histologically identifiable breast lesion linked to cancer progression and is characterized by increased proliferation, decreased apoptosis and elevated oestrogen receptor α (ERα) expression. The mechanisms underlying the initiation of these lesions have not been clarified but might involve early and fundamental changes in cancer progression. MiRNAs are key regulators of several biological processes, acting by influencing the post-transcriptional regulation of numerous targets, thus making miRNAs potential candidates in cancer initiation. Here we have defined novel epithelial as well as stromal miRNA signatures from columnar cell hyperplasia lesions compared to normal terminal duct lobular units by using microdissection and miRNA microarrays. Let-7c were among the identified downregulated epithelial miRNAs and its functions were delineated in unique CCH derived cells and breast cancer cell line MCF-7 suggesting anti-proliferative traits potentially due to effects on Myb and ERα. MiR-132 was upregulated in the stroma surrounding CCH compared to stoma surrounding normal terminal duct lobular units (TDLUs), and overexpression of miR-132 in immortalized fibroblasts and in fibroblasts co-cultured with epithelial CCH cells caused substantial expression changes of genes involved in metabolism, DNA damage and cell motility. The miRNA signatures identified in CCH indicate early changes in the epithelial and stromal compartment of CCH and could represent early key alterations in breast cancer progression that potentially could be targeted in novel prevention or treatment schedules.

Highlights

The initial model of the evolution of breast cancer was proposed to be a long process involving a few key stages, starting with proliferation and enlargement of the normal terminal duct lobular units (TDLUs) [1]
columnar cell hyperplasia (CCH) have altered miRNA expression patterns TDLUs and CCH with no or mild atypia from the same specimen were collected based on morphological evaluation and positive elevated oestrogen receptor a (ERa) expression using microdissection
By comparing the expression in TDLUs and CCH we discovered 23 altered miRNAs in the epithelial compartment (n = 4, p,0.05, Table 1) and 17 in the surrounding stroma (n = 2, more than 2.0 fold change, Table 2)

Summary

Introduction

The initial model of the evolution of breast cancer was proposed to be a long process involving a few key stages, starting with proliferation and enlargement of the normal terminal duct lobular units (TDLUs) [1] These alterations, denoted columnar cell hyperplasia (CCH), are common abnormalities in the adult female breast and are characterized by enlarged TDLUs lined by tightly packed columnar-shaped epithelial cells [2,3]. It is possible to observe changes in the stroma in early stages of cancer development, including an increased number of fibroblasts which have acquired an active phenotype that is observed in wound healing [8]. These cells are commonly called cancer-associated fibroblasts and can promote tumour growth and progression [9]

Methods

Results

Conclusion