Differential Expression Of BRCA1 MRNA And Protein In Sporadic Breast Cancer

Objective: to investigate the changes in mRNA and protein expression of breast cancer susceptibility gene 1(BRCA1) during the development and progression sporadic breast cancer. Methods: BRCA1 mRNA expression in sporadic breast cancer tissue and normal breast tissue was determined by quantitative real-time polymerase chain reaction(qPCR); BRCA1 protein expression and subcellular location were determined by immunohistochemistry; and the correlation between BRCA1 and development and progression of sporadic breast cancer was analyzed. Results:1. BRCA1 mRNA expression was lower in breast cancer tissue( 0.759±0.440) than in normal breast tissue(1.530±0.810), and significantly higher in carcinoma in situ(with minimal invasion)(0.956±0.340)than invasive breast cancers(0.561±0.443)(P<0.01). BRCA1 mRNA expression also seem to be higher in lymph nodes with negative Ki-67 or a Ki-67 value≤14% than those with a Ki-67 value > 14%, but the difference was not statistically significant. BRCA1 mRNA expression was irrelevant to status of hormone receptors. 2.BRCA1 protein was highly expressed in normal breast tissue, and lowlier expressed in breast cancer(positive rate: 95% vs. 46%,χ2=27.040,P<0.001); BRCA1 expression was also significantly lower in invasive breast cancer than ductal carcinoma in situ(with minimal invasion)(χ2=4.037,P<0.05). We also observed alteration in subcellular location of BRCA1 protein, which is confined in the nucleus in normal breast tissue,and diffused in both nucleus(at decreased level) and the cytoplasm in breast cancer tissue.Conclusion: BRCA1 mRNA and protein expression altered with the development and progression of sporadic breast cancer.