Antineoplastic Agents/therapeutic use; Aromatase Inhibitors; Breast Neoplasms/drug therapy; Drug Resistance, Neoplasm; Estradiol/analogs & derivatives; Fibroblast Growth Factors/physiology; Tamoxifen/therapeutic use; Androstenedione/analogs & derivatives; Androstenedione/therapeutic use; Androstenedione/toxicity; Animals; Antineoplastic Agents/toxicity; Breast Neoplasms/metabolism; Breast Neoplasms/pathology; Cell Division/drug effects; Cell Line; Chloramphenicol O-Acetyltransferase/biosynthesis; Enzyme Inhibitors/therapeutic use; Enzyme Inhibitors/toxicity; Estradiol/therapeutic use; Estradiol/toxicity; Estrogen Antagonists/therapeutic use; Estrogen Antagonists/toxicity; Female; Fibroblast Growth Factors/biosynthesis; Fulvestrant; Humans; Letrozole; Luciferases/biosynthesis; Mice; Mice, Nude; Nitriles/therapeutic use; Nitriles/toxicity; Ovariectomy; Polymerase Chain Reaction; RNA, Messenger/biosynthesis; Receptors, Progesterone/biosynthesis; Recombinant Fusion Proteins/biosynthesis; Tamoxifen/toxicity; Transcription, Genetic; Transfection; Transplantation, Heterologous; Triazoles/therapeutic use; Triazoles/toxicity; Tumor Cells, Cultured