Figure 7.

Estrogen stimulation greatly promotes the growth of Cav-1-deficient acini but only during growth factor deprivation. WT and Cav-1 KO mammary epithelial cells were isolated, overlaid onto Matrigel, and allowed to form 3-D acini-like structures. Acini were cultured in the presence or absence of EGF and were either stimulated with estrogen or left untreated. Of course, all estrogen stimulation experiments were performed using phenol red-free media and charcoal-stripped serum (see Materials and Methods). A: Growth curve. Acinar growth was monitored by measuring the diameters of day 16 WT and Cav-1 KO acini. At least 50 epithelial structures were scored for each condition and for each genotype. Note that Cav-1-deficient mammary epithelial cells develop larger acini than WT cells, in the presence or absence of EGF. Remarkably, estrogen treatment greatly stimulates the growth of Cav-1 KO acini in the absence, but not in the presence of EGF, suggesting that a lack of EGF increases the estrogen sensitivity of Cav-1-null acini. Importantly, estrogen treatment did not exert any effects on WT acini. *P < 0.0075. B: Phase contrast images. Micrographs of EGF-deprived WT and Cav-1 KO acini, stimulated with estrogen or left untreated, are shown. Note that, in the absence of EGF, estrogen stimulation does not promote the growth of WT acini. In contrast, EGF-depleted Cav-1-deficient acini become much larger in response to estrogen stimulation.