Mass Cytometric Analysis Reveals Viable Activated Caspase-3+ Luminal Progenitors in the Normal Adult Human Mammary Gland

Abstract

The normal adult human female mammary gland isabilayered structure consisting of an outer basal layer and two readily distinguished subsets of cells within the inner luminal layer. We now present a validated methodology for undertaking large-scale multi-parameter mass cytometric analyses of these cell types at single-cell resolution. In addition, we show how combining this approach with invitro clonogenic assays of the proliferative and signaling responses of normal human mammary cells to epidermal growth factor (EGF) allows additional subsets with different EGF responses to be discerned. This included the identification of a subset of cells within the phenotypically defined luminal progenitor fraction that displays an elevated content of active caspase-3, including some that generate clones invitro in response to EGF, with immunohistochemical evidence of their presence insitu in fixed preparations of normal human breast tissue.