Greater inhibition of TamR (A) and MCF7-X (B) cell growth by the pure anti-oestrogen fulvestrant is apparent when the drug is used in combination with AZD8055. TamR cells were grown for seven days in the absence of tamoxifen. TamR and MCF7-X cells were then grown for seven days in the presence of fulvestrant (10-7 M) and AZD8055 (0 to 25 nM). Cells were counted and the results expressed as a percentage of the untreated control. Results are means of four independent experiments. Statistical analyses used ANOVA with a post hoc test to compare doses of AZD8055 plus fulvestrant versus AZD8055 alone and AZD8055 plus fulvestrant versus the fulvestrant alone control (0). *P <0.05, **P <0.01, ***P <0. 001. ANOVA, analysis of variance.