Figure 1

MYC expression is elevated in antiestrogen resistant breast cancer in vitro and in vivo . A, Basal MYC-luciferase activity is 4.24-fold (SE = 0.10) higher in LY2 and LCC2 (estrogen independent but responsive; antiestrogen resistant) and 6.67-fold (SE = 0.09) higher in LCC9 (estrogen independent and non-responsive; antiestrogen resistant) compared with LCC1 (estrogen independent but responsive; antiestrogen sensitive); see Experimental Procedures. ANOVA, p < 0.001; *p < 0.05 for MYC promoter activation in indicated cells compared with LCC1 cells. B, Western blot shows increased expression of MYC protein in LCC9 cells compared to LCC1 cells while MAX protein levels did not change; actin was used as a loading control. C, Immunohistochemical (IHC) MYC staining show increased protein levels (brown) in LCC9 compared with LCC1 xenografts; for negative controls, antibody diluents without MYC antibody were used. D, DMBA-induced rat mammary gland tumors with acquired resistance to TAM show increased levels MYC protein levels (brown) compared to sensitive (or de novo resistant) tumors.