Cyclin D1 Overexpression is Associated with Estrogen Receptor Expression in Caucasian but not African-American Breast Cancer

Background: African-American (AA) breast cancer patients consistently show a shortened survival when compared with Caucasian patients. This worse prognosis is most likely due to a combination of socioeconomic factors and differences in tumor biology. Previous studies have demonstrated that cyclin D1 overexpression is strongly associated with estrogen receptor (ER) expression in breast cancer, but these series either included primarily Caucasian patients or did not specify race. Materials and Methods: We analyzed 200 breast cancer cases obtained from AA and Caucasian patients who were matched on age, stage, ER status, and year of diagnosis. We examined expression levels of cyclin D1, p53, p27 Kip1 (p27), and p21 Cip1 (p21), and correlated their expression with ER status. Results: Cyclin D1, p53, p27, and p21 expression rates were similar in matched cases of AA and Caucasian breast cancer (p values>0.05). However, cyclin D1 overexpression was significantly associated with ER status in only the Caucasian (p=0.0005), and not the AA cases (p=0.07). Conclusion: This finding suggests a novel biological difference, which may contribute to the more aggressive phenotype of AA breast cancer.