Isolation of EpH4 mammary epithelial cell subpopulations which differ in their morphogenetic properties.

EpH4 is a nontumorigenic cell line derived from spontaneously immortalized mouse mammary gland epithelial cells (Fialka et al., 1996). When grown in collagen gels, EpH4 cells give rise to different types of structures, e.g., solid cords or branching tubes. By removing and subsequently dissociating single three-dimensional colonies of defined morphology, we have isolated six clonal subpopulations of EpH4 cells which display distinct morphogenetic properties in collagen gel cultures. Thus, cells from the H1B clone form branching cords devoid of a central lumen, K3A3 cells form cords enclosing small multifocal lumina, and J3B1 cells form large cavitary structures containing a wide lumen. I3G2 cells form either cords or tubes, depending on the type of serum added to the culture medium. Finally, when grown in serum-free medium, Bela cells form spherical cysts, whereas Be4a cells form long, extensively branched tubes. In additional assays of morphogenesis, i.e., cell sandwiching between two collagen gels or culture on a thick layer of Matrigel (a laminin-rich extracellular matrix), all clones form epithelial-cell lined cavitary structures, except H1B cells which are unable to generate lumina under these conditions. The EpH4 sublines we have isolated provide an in vitro system for studying the mechanisms responsible for lumen formation and branching morphogenesis, as well as for identifying the factors which subvert these developmental processes during mammary carcinogenesis.