title: Reporter gene assay demonstrates functional differences in estrogen receptor activity in purified breast cancer cells: a pilot study.
abstract: Tamoxifen has contributed to a dramatic reduction in breast cancer mortality and recent results indicate that aromatase inhibitors may further improve survival in some patients. Nevertheless, a substantial proportion of patients become resistant to treatment. To date, with the exception of estrogen receptor (ER) determination by ligand binding or immunohistochemical techniques, there has been no way of predicting which of several therapies is indicated in particular patients. We describe a novel assay using the adenoviral gene delivery system to assess ER function in breast cancer cells derived directly from patients. The purification and short-term culture of these cells has been recently described by our laboratory. Adenovirus containing an estrogen-regulated beta-galactosidase reporter gene (ERE-lacZ) was constructed and used to test ER activity in breast cancer cells derived from 18 patients with primary and 16 patients with metastatic cancer, under varying treatment schedules. The adenoviral assay enabled ER activity to be readily determined in purified cells from primary breast cancers and secondary sites. Breast cancers cells could be categorized on the basis of ER activity in the absence of ligand, the presence of estrogen or anti-estrogens. In primary breast cancers, our results correlated with ER determination by immunohistochemistry in 78% of cases. In patients who had become resistant to tamoxifen, however, we found some in whom reporter activity was stimulated by tamoxifen and others whose tumors were either still estrogen responsive or completely unresponsive, irrespective of the original ER content. Our findings indicate that this reporter assay could be useful in decisions regarding use of adjuvant endocrine therapies in breast cancer.
authors.affiliation: Cancer Research (UK) Laboratories, Department of Cancer Medicine, Faculty of Medicine, Imperial College, Hammersmith Hospital, London, United Kingdom.
authors.forename: Anjana
authors.initials: A
authors.lastname: Singh
authors.forename: Simak
authors.initials: S
authors.lastname: Ali
authors.forename: Manish S
authors.initials: MS
authors.lastname: Kothari
authors.forename: Manuela Tamburo
authors.initials: MT
authors.lastname: De Bella
authors.forename: Clive
authors.initials: C
authors.lastname: Smith
authors.forename: Emma
authors.initials: E
authors.lastname: Timms
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Slade
authors.forename: Brian M
authors.initials: BM
authors.lastname: Foxwell
authors.forename: R Charles
authors.initials: RC
authors.lastname: Coombes
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D001943:Breast Neoplasms / Q000473:pathology*; D044584:Carcinoma, Ductal / Q000473:pathology; D018288:Carcinoma, Small Cell / Q000473:pathology; D047628:Estrogen Receptor alpha; D005260:Female; D017930:Genes, Reporter; D005822:Genetic Vectors; D006801:Humans; D009361:Neoplasm Invasiveness; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015203:Reproducibility of Results; D014407:Tumor Cells, Cultured; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D047628:Estrogen Receptor alpha; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D011993:Recombinant Fusion Proteins; D001616:beta-Galactosidase