Identification of Cyclin D1– and Estrogen-Regulated Genes Contributing to Breast Carcinogenesis and Progression

Abstract

Tumors can become lethal when they progress from preinvasive lesions to invasive carcinomas. Here, we identify candidate tumor progression genes using gene array analysis of preinvasive and invasive tumors from mice, which were then evaluated in human cancers. Immediate early response protein IEX-1, small stress protein 1 (HSPB8), and tumor necrosis factorassociated factor-interacting protein mRNAs displayed higher expression levels in invasive lesions than in preinvasive lesions using samples obtained by laser capture microdissection (LCM) from transgenic erbB2, ras, and cyclin D1 mice. LCM-isolated tissues from patient-matched normal, ductal carcinoma in situ, and invasive ductal carcinoma revealed similar increased expression in invasive human cancers compared with preinvasive and normal samples. These genes induced anchorage independence, increased cell proliferation, and protected against apoptosis, singly or in collaboration with erbB2. Surprisingly, they were all up-regulated by 17B-estradiol and cyclin D1, and cyclin D1 overexpression increased p300/CBP binding to their promoters, supporting the model that cyclin D1-estrogen receptor (ER) coactivator interactions may be important to its role in ER-positive breast cancer. Additionally, an irreversible dual kinase inhibitor of ErbB signaling inhibited expression of the same genes. The up-regulation of genes contributing to increased invasiveness of ER-positive cancers offers a novel explanation for the contribution of cyclin D1 to a worse prognosis in ER-positive cancers. As targets of estrogen, cyclin D1, and erbB2 signaling, these candidates offer insights into the nature of the second events involved in breast cancer progression, regulatory events contributing to invasion, and potential targets of combined inhibition of hormone and growth factor signaling pathways. (Cancer Res 2006; 66(24): 11649-58)

Induction of Hsp22 (HspB8) by estrogen and the metalloestrogen cadmium in estrogen receptor– positive breast cancer cells

“…Previous studies demonstrated induction of Hsp22 by E 2 in ER ϩ breast cancer cells at the transcriptional level (Charpentier et al 2000;Yang et al 2006). Here, we present data concerning Hsp22 induction at the protein level.…”

“…The current hypothesis is that E 2 acts as an epigenetic factor that is involved in conversion of precancerous to cancerous cells in the course of tumor progression. Hsp22 was identified recently as a potential key player in the progression of breast cancer in humans (Yang et al 2006). Hsp22 expression is a downstream event of both erbB2 → cyclin D1 and E 2 signaling pathways, and this fact was suggested to be the basis for the well known association between cyclin D1 expression and poor prognosis.…”

“…Previously it was shown that ectopic expression of Hsp22 and Hsp27 promoted cell growth and resistance to doxorubicin in breast cancer cells (Oesterreich et al 1993;Yang et al 2006). In order to explore the possibility of downregulation of Hsp22 as a potential therapeutic strategy, we decreased the amount of Hsp22 in MCF-7 cells by the RNA interference (RNAi) method, and tested to see whether this would modulate cell growth and drug resistance.…”

“…On the basis of previous reports on E 2 induction of Hsp22 mRNA in MCF-7 cells (Charpentier et al 2000;Yang et al 2006), we tested to see whether this response also translates to the level of the protein. For optimal response, MCF-7 cells were grown consecutively in complete medium, starvation medium, and in E 2 -deficient medium, which was supplemented with the substances as is specified in Figure 1 and in the Materials and Methods section.…”

“…In one of those studies, a serial analysis of gene expression (SAGE) screen was conducted with the aim to identify genes that are regulated by E 2 . Hsp22 mRNA was found to be among the most highly induced transcripts in ER ϩ MCF-7 breast cancer cells (Charpentier et al 2000), and this up-regulation of Hsp22 mRNA was confirmed in a more recent study (Yang et al 2006). These data strongly suggest Hsp22 induction to be a hitherto unrecognized part of the estrogenic response, although to date, this induction has not been verified at the protein level.…”