Figure 3.

ER inhibits invasion and stimulates growth by distinct mechanisms. A, ER protein expression in Tet-on cells. Tet-on 231 cells were incubated with and without Tet for 24 hours and examined for ER and ER/T311A protein expression. B, Thr³¹¹ is required for ER transcription activity. Cells were transfected with ERE-Luc, incubated with and without Tet for 24 hours, and assessed for luciferase activity. Columns, mean of five independent experiments; bars, SD. C, ER requires its transcription activity to inhibit invasion. Cells were cultured ± Tet for 22 hours in the invasion chamber for the assay (see Materials and Methods). Columns, mean from 16 fields in one experiment; bars, SD. Similar results were obtained in two additional experiments. The absorption at A _{600 nm} (OD600 ) is mean of three separate experiments. D, ER does not require its transcription activity to stimulate DNA synthesis. Cells were cultured for 24 hours with or without Tet and cell growth was estimated by thymidine incorporation.