Effects of E2 or SWT on cell growth of MCF-7 (A) and MDA-MB-231 (B). The hormone-deprived cells in 96-well plates (5,000 cells per well) were treated with E2 or SWT for 48 hours, cell growth was measured with SRB assay. Results are expressed as percentage of control cells with no drug treatment. Points, means from three replicates; bars, S.D. *, P < 0.05; **, P < 0.01.