In vitro propagation and transcriptional profiling of human mammary stem/progenitor cells

Abstract

Although the existence of mammary stem cells has been suggested by serial transplantation studies in mice, their identification has been hindered by the lack of specific surface markers, and by the absence of suitable in vitro assays for testing stem cell properties: self-renewal and ability to generate differentiated progeny. We have developed an in vitro cultivation system that allows for propagation of human mammary epithelial cells (HMECs) in an undifferentiated state, based on their ability to proliferate in suspension, as nonadherent mammospheres. We demonstrate that nonadherent mammospheres are enriched in early progenitor/stem cells and able to differentiate along all three mammary epithelial lineages and to clonally generate complex functional structures in reconstituted 3D culture systems. Gene expression analysis of cells isolated from nonadherent mammospheres revealed overlapping genetic programs with other stem and progenitor cells and identified new markers that may be useful in the identification of mammary stem cells. The isolation and characterization of these stem cells should help elucidate the molecular pathways that govern normal mammary development and carcinogenesis.

The lymphovascular embolus of inflammatory breast cancer exhibits a Notch 3 addiction

“…Overexpression of active forms of murine Notch 1-4 The gene expression profile of CD44 þ immunosorted cells was obtained from a published study (Shipitsin et al, 2007). The gene expression profile of CD44 þ mammospheres/neurospheres was obtained from a published study (Dontu et al, 2003).…”

“…The gene expression profile of the MARY-X spheroids was compared with the published gene expression profile of acknowledged models of mammary gland stem cells: CD44 þ mammospheres/neurospheres and CD44 þ immunosorted cells (Dontu et al, 2003;Shipitsin et al, 2007). Several genes in common, including Notch 3 (Sansone et al, 2007a, b), were overexpressed in all three models (Table 3).…”

Stem cells in the heart: What's the buzz all about?—Part 1: Preclinical considerations

“…In fact, spontaneous sphere formation by progenitor cells is not a phenomenon unique to progenitors isolated from the heart. Sphere formation also has been observed with neural, 30 retinal, 31 mammary, 32 kidney, 33 and prostate 34 progenitors and is thought to play a role in determining cell phenotype and survival. 35 We were highly successful using the cardiosphere method.…”

Introduction of SV40ER and hTERT into mammospheres generates breast cancer cells with stem cell properties

“…More recently, a small sub-population of human mammary epithelial cells (HMECs) was shown to form three-dimensional (3D) spheroids called mammospheres when grown in suspension in vitro (Dontu et al, 2003). Mammospheres are largely comprised of primitive mammary stem and progenitor cells of varying proliferation potential, and capable of undergoing both self-renewal and multilineage differentiation in vitro (Dontu et al, 2003).…”

“…More recently, a small sub-population of human mammary epithelial cells (HMECs) was shown to form three-dimensional (3D) spheroids called mammospheres when grown in suspension in vitro (Dontu et al, 2003). Mammospheres are largely comprised of primitive mammary stem and progenitor cells of varying proliferation potential, and capable of undergoing both self-renewal and multilineage differentiation in vitro (Dontu et al, 2003). Moreover, transplantation of mammospheres into cleared mammary fat pad generated complete mammary structures in vivo, further confirming the presence of long-term self-renewing stem/progenitor population within mammospheres (Liao et al, 2007).…”