BAG-1: A novel biomarker predicting long-term survival in early-stage breast cancer

Purpose: Among women with early-stage breast cancer treated with lumpectomy and radiation therapy, 30% to 40% will develop metastatic disease, which is often fatal. A need exists therefore for biomarkers that distinguish patients at high risk of relapse. We performed a retrospective correlative analysis of BAG-1 protein expression in breast tumors derived from a cohort of early-stage breast cancer patients. Patients and Methods: Archival paraffin blocks from 122 women with stages I to II breast cancer treated with lumpectomy and radiation therapy (median follow-up, 12.1 years) were analyzed by immunohistochemical methods using monoclonal antibodies recognizing BAG-1 and other biomarkers, including Bcl-2, estrogen receptor, progesterone receptor, p53, and HER2/Neu. Immunostaining data were correlated with distant metastasis-free survival (DMFS) and overall survival (OS). Results: Cytosolic immunostaining for BAG-1 was upregulated in 79 (65%) of 122 invasive breast cancers (P <.001) compared with normal breast. Elevated BAG-1 was significantly associated with longer DMFS and OS, overall (stages I and II) and in node-negative (stage I only) patients, on the basis of univariate and multivariate analyses (DMFS, P = .005; OS, P = .01, in multivariate analysis of all patients; DMFS, P = .005; OS, P = .001, in multivariate analysis of node-negative patients). All other biomarkers failed to reach statistical significance in multivariate analysis. Clinical stage was an independent predictor of OS (P = .04) and DMFS (P = .02). Conclusion: These findings provide preliminary evidence that BAG-1 represents a potential marker of improved survival in early-stage breast cancer patients, independent of the status of axillary lymph nodes.