Immunohistochemical Expression of BRCA1 in Prostate Cancer
M Fiorentino, L Mucci, K Fall, D Bailey, C Fiore, G Judson, O Andren, SO Andersson, M Loda. Dana-Farber Cancer Institute, Boston, MA; Harvard School of Public Health, Boston, MA; University of Orebro, Orebro, Sweden
Background: BRCA1 is a multifunctional protein involved in DNA repair, gene transcription and the regulation of cell-cycle check-points. While germline mutations of BRCA1 are rare in prostate cancer and seem to play a limited role in tumor susceptibility, BRCA1 expression has not been investigated to date.
Design: We analyzed the immunohistochemical expression of BRCA1 in paraffin embedded samples from 524 men with prostate cancer belonging to the Physicians' Health Study and the Swedish Watchful Waiting cohorts of prostate cancer patients. High density tissue micro-arrays (TMA) including at least three tumor cores for each case were utilized for the immunohistochemical staining with the monoclonal MS110 antibody specific for the N-terminus of the 220 kDa BRCA1 protein. Cases were scored as negative or positive for BRCA1 immunostaining. The Ki67 proliferation index was also assessed on the same TMAs and evaluated by quantitative image analysis.
Results: A positive nuclear immunostaining for BRCA1 was revealed in 62 of 524 (11.9%) patients while normal prostate control cores were all negative. BRCA1 positive tumors were associated with 4 times greater proliferation rate compared to BRCA1 negative tumors (p 0.0003). In addition, we found a linear trend such that tumors with greater number of TMA cores expressing BRCA1 had stronger extent of proliferation. Men with BRCA1 positive tumors had a slightly higher Gleason's score (mean 7.5) compared to those negative for BRCA1 (mean 7) No significant correlation was found between BRCA1 staining and cancer-specific death.
Conclusions: BRCA1 protein is expressed in a small subset of prostate cancers characterized by high proliferation index but not in normal prostate tissue. Expression of BRCA1 might be acquired in selected tumors to prevent DNA damage in actively replicating cells. A different role independent of germline mutations might be disclosed for BRCA1 as cell cycle regulator in prostate cancer.
Category: Genitourinary (including renal tumors)
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 103, Wednesday Morning