SRCs and HERs expression during tamoxifen treatment. SRC-1, -2 and -3 and HER-1, -2, -3 and -4 mRNA expression levels as well as the levels of Ets-2 and ERα mRNA after 14 days of oral tamoxifen treatment are presented compared to controls receiving vehicle only in DMBA-induced breast cancer. The mRNA levels of our target genes were calculated relative to the expression of the housekeeping gene TBP and the data presented as geometric means with error bars indicating 95% confidence intervals. Differences in mRNA levels between the treatment groups were evaluated using Mann Whitney U test and statistical significance indicated in the figure (* = P < 0.05, ** = P < 0.01) (A). The protein levels of the SRCs (B) and HER-2 and HER-3 (C) in tamoxifen treated tumors compared to controls were analyzed using Western blots. Representative blots of the tumor response to tamoxifen treatment are presented, using β-actin as control for protein load.