Mammary gland stem cells: Current status and future challenges

Abstract

Distinct subsets of cells, including with cell-like properties, have been proposed to exist in normal human breast epithelium and carcinomas. The cellular origins epithelial cells contributing to gland development, tissue homeostasis and cancer are, however, still poorly understood. The mouse is a widely used model mammary gland development, both directly by studying the mouse mammary epithelial cells themselves and indirectly, studying development, morphogenesis, differentiation and carcinogenesis xenotransplanted human epithelium in vivo. While early studies, human or mouse epithelium was implanted as fragments into the mouse gland, more recent technical progress has allowed the self-renewal capacity and differentiation potential of distinct cell populations even individual cells to be interrogated. Here, we review and discuss similarities and differences between mouse and human gland development with particular emphasis on the identity and localization stem cells, and the influence the surrounding microenvironment. It is concluded that while recent advances in the field have contributed immense insight how the normal mammary gland develops and maintained, significant discrepancies exist the mouse and human gland which should taken into consideration current and future models of mammary stem cell biology. © 2011 UBC Press.