Expression of BRCA1 is reduced in BG-1 cells following infection with antisense BRCA1. (A) Ribonuclease protection analysis of BRCA1 mRNA. Lanes 1 and 2 show undigested probe for BRCA1 and loading control, cyclophilin. Lanes 3 and 4 are pooled BG-1 neo-infected control cells grown minus [Dulbecco's modified eagle medium (DMEM)] and plus (E2) 10-8 mol/l estrogen 24 h. Lanes 5 and 6 are pooled BG-1 BRCA1 antisense-infected cells minus and plus 10-8 mol/l estrogen, respectively, for 24 h. The observed doublet is the result of incomplete digestion. (B) Western blot analysis of individual control (NEO) and BRCA1 antisense (AS) clones. MDAMB468 is a BRCA1-positive breast cancer cell line.