c-Myb expression is estrogen regulated. (A) MCF-7 cells were deprived of estrogen for 48 hr then stimulated with 10 nM 17-beta-estradiol for 6, 12 or 24 hr. Quantitative real time PCR (QPCR) was used to measure the levels of c-myb RNA during the deprivation and stimulation protocol. Error bars show standard deviation in triplicate PCR reactions, and results are relative to the estrogen-deprived cells. (B) Western blot with anti-c-Myb and anti-beta-actin antibodies of estrogen-deprived (Depr) or stimulated (Stim) MCF-7 cells, divided into cytoplasmic (C) or nuclear (N) fractions as described in Methods.