Rearrangement of the F-actin cytoskeleton in estradiol-treated MCF-7 breast carcinoma cells

In response to treatment with 17 beta-estradiol, MCF-7 human breast carcino ma cells undergo a marked rearrangement of the F-actin cytoskeleton. The mo st conspicuous aspect of this rearrangement is the formation of an extensiv e array of lamellipodial structures which are situated beneath cell cluster s. Treatment of cells with 17 beta-estradiol in the presence of the anti-es trogen ICI182,780 suppressed the development of the lamellipodial structure s, indicating that this cytoskeletal rearrangement is mediated by the estro gen receptor. Time-lapse, video-enhanced, differential interference contras t microscopy reveals that the lamellipodial structures are actively motile beneath cell clusters. Furthermore, the lamellipodial structures form few f ocal contacts with the underlying substrate of the coverslip, as evidenced by either interference reflection microscopy or staining for the focal cont act protein talin, indicating: that these structures are not strongly adher ed to the substratum. Immunofluorescence localization of E-cadherin indicat es that this cell-cell adhesion receptor is present within these structures as either adhesion plaque- or point contact-like depositions. These findin gs implicate the cadherin-based cell-cell adhesion system in supporting tum or cell motility over adjacent cell surfaces via discrete adhesive structur es which are associated with motile lamellipodia.