Involvement of c-src in beta-casein expression by mammary epithelial cells.

HC11 mouse mammary epithelial cells were stably transfected with c-src or a dominant negative mutant of c-src driven by a MMLV promoter. Prolactin increased c-src activity in control and c-src transfected cells, while dominant negative c-src reduced the prolactin-induced increase in c-src activity. Dominant negative c-src also reduced the ability of insulin, hydrocortisone, and prolactin to induce beta-casein accumulation to levels one-half to one-third that of control cells. This effect was uncorrelated with any change in cell proliferation or laminin accumulation and was observed both in cultures grown to confluency in the presence of EGF and in cultures grown on laminin.