Alterations in Progesterone Receptor Isoform Balance in Normal and Neoplastic Breast Cells Modulates the Stem Cell Population.

María Sol Recouvreux,María Inés Diaz Bessone,Agustina Taruselli,Laura Todaro,Mina J Bissell,Marina Simian,Rocío G Sampayo,María Amparo Lago Huvelle

doi:10.3390/cells9092074

Abstract

To investigate the role of PR isoforms on the homeostasis of stem cells in the normal and neoplastic mammary gland, we used PRA and PRB transgenic mice and the T47D human breast cancer cell line and its derivatives, T47D YA and YB (manipulated to express only PRA or PRB, respectively). Flow cytometry and mammosphere assays revealed that in murine breast, overexpression of PRB leads to an increase in luminal and basal progenitor/stem cells. Ovariectomy had a negative impact on the luminal compartment and induced an increase in mammosphere-forming capacity in cells derived from WT and PRA mice only. Treatment with ICI 182,780 augmented the mammosphere-forming capacity of cells isolated from WT and PRA mice, whilst those from PRB remained unaltered. T47D YB cells showed an increase in the CD44+/CD24Low/− subpopulation; however, the number of tumorspheres did not vary relative to T47D and YA, even though they were larger, more irregular, and had increased clonogenic capacity. T47D and YA tumorspheres were modulated by estrogen/antiestrogens, whereas YB spheres remained unchanged in size and number. Our results show that alterations in PR isoform balance have an impact on normal and tumorigenic breast progenitor/stem cells and suggest a key role for the B isoform, with implications in response to antiestrogens.

Highlights

The normal mammary gland consists of an epithelial hierarchy where tissue-specific stem cells are able to self-renew and produce committed progenitors that give rise to terminally differentiated cells which comprise the functional gland [1]
To isolate cell populations enriched in mouse mammary progenitor/stem cells and their derivative colony-forming cell progeny, we removed the hematopoietic and endothelial cell compartment and selected different mammary cell sub-compartments according to the expression of CD24 and CD29 cell surface markers
Show that overexpression of PRB led to a statistically significant increase in the CD24+ /CD29hi basal and CD24+ /CD29+ luminal cell compartments as compared to cells derived from mammary glands of wild type (WT) and PRA transgenic mice

Summary

Introduction

The normal mammary gland consists of an epithelial hierarchy where tissue-specific stem cells are able to self-renew and produce committed progenitors that give rise to terminally differentiated cells which comprise the functional gland [1]. The epithelium of the mammary gland is composed of two cellular lineages: luminal cells that surround a central lumen and myoepithelial cells that are located in a basal position next to the basement membrane. Together, these cells are organized into a series. Estrogen receptor-alpha (ERα) is critical for mammary gland development and plays a key role in tumor progression and in determining whether a patient is eligible for endocrine therapy; 75% of diagnosed breast cancers are ERα-positive [4,5]. Estrogens are proposed to play an indirect role in the expansion of normal murine mammary stem cells by inducing PR expression [6,7]. Selective ER down modulators, like Tamoxifen, down regulators such as ICI 182,780, and aromatase inhibitors have proved to enrich the cancer stem cell pool [10,11]

Methods

Results

Conclusion