BACKGROUND: The product of the Bcar1/p130Cas (breast cancer resistance/p130Crk-associated substrate) gene causes resistance to antiestrogen drugs in human breast cancer cells in vitro. To investigate its role in clinical breast cancer, we determined the levels of Bcar1/p130Cas protein in a large series of primary breast carcinomas. METHODS: We measured Bcar1/p130Cas protein in cytosol extracts from 937 primary breast carcinomas by western blot analysis. The levels of Bcar1/p130Cas protein were tested for associations and trends against clinicopathologic and patient characteristics, the lengths of relapse-free survival and overall survival (n = 775), and the efficacy of first-line treatment with tamoxifen for recurrent or metastatic disease (n = 268). RESULTS: Bcar1/p130Cas levels in primary tumors were associated with age/menopausal status and the levels of estrogen receptor and progesterone receptor. In univariate survival analysis, higher Bcar1/p130Cas levels were associated with poor relapse-free survival and overall survival (both two-sided P =.04; log-rank test for trend). In multivariate analysis, a high level of Bcar1/p130Cas was independently associated with poor relapse-free survival and overall survival. The response to tamoxifen therapy in patients with recurrent disease was reduced in patients with primary tumors that expressed high levels of Bcar1/p130Cas. In multivariate analysis for response, Bcar1/p130Cas was independent of classical predictive factors, such as estrogen receptor status, age/menopausal status, disease-free interval, and dominant site of relapse. CONCLUSION: Patients with primary breast tumors expressing a high level of Bcar1/p130Cas protein appear to experience more rapid disease recurrence and have a greater risk of (intrinsic) resistance to tamoxifen therapy. Thus, measurement of Bcar1/p130Cas may provide useful prognostic information for patients with primary or metastatic breast cancer.

*Proteins, Adult, Aged, Aged, 80 and over, Antineoplastic Agents, Hormonal/pharmacology/*therapeutic use, Blotting, Western, Breast Neoplasms/*drug therapy/*metabolism, Crk-Associated Substrate Protein, Estrogen Receptor Modulators/pharmacology/*therapeutic use, Female, Genes, BRCA1/*drug effects, Humans, Logistic Models, Middle aged, Neoplasms, Hormone-Dependent/*drug therapy/*metabolism, Phosphoproteins/drug effects/*genetics, Prognosis, Proportional Hazards Models, Receptors, Estrogen/drug effects, Receptors, Progesterone/drug effects, Research Support, Non-U.S. Gov't, Retinoblastoma-Like Protein p130, Survival Analysis, Tamoxifen/pharmacology/*therapeutic use, Treatment Outcome
hdl.handle.net/1765/9229
National Cancer Institute. Journal (Print)
Erasmus MC: University Medical Center Rotterdam

van der Flier, S, Brinkman, A, Look, M.P, Kok, E.M, Meijer van Gelder, M.E, Klijn, J.G.M, … Foekens, J.A. (2000). Bcar1/p130Cas protein and primary breast cancer: prognosis and response to tamoxifen treatment. National Cancer Institute. Journal (Print). Retrieved from http://hdl.handle.net/1765/9229