Abstract B74: Racial variation of adipocytokine levels in women with breast cancer

Abstract

Abstract Background: The incidence of breast cancer is lower among African-American women than White women; however, African-American women have worse survival, represent a greater proportion of young women with breast cancer, and tend to have more aggressive tumors at diagnosis. A number of social factors contribute to the disparities; however, biologic differences are being explored. Obesity is a risk factor that has a significant effect in breast cancer disparities. Two cytokines produced by adipose tissue, leptin and adiponectin, have been shown to be active in breast cancer cell lines in vitro and to correlate with breast cancer risk and tumor characteristics in epidemiologic studies. Leptin has mitogenic effects on breast cancer cells in vitro and increases with obesity. Adiponectin has inhibitory effects on cancer growth and decreases with obesity. Data from studies of cardiovascular disease and metabolic syndrome suggest that levels of adipocytokines may differ by race, adjusted for body mass index (BMI). We measured levels of leptin and adiponectin in African-American and White women with breast cancer to test our hypothesis that serum levels differ by race. We hypothesized that African-American women would have higher levels of leptin and lower levels of adiponectin, adjusted for BMI. We also correlated tumor characteristics, including grade, age, stage, ER/PR and Her-2/neu status with levels of these adipocytokines to test the hypothesis that more aggressive tumor features would correlate with higher levels of leptin and lower levels of adiponectin. Methods: We performed a retrospective case-case study of 68 African-American and 59 White breast cancer patients. Adiponectin and leptin levels were measured in serum samples by enzyme-linked immunosorbent assay (ELISA). Medical records were abstracted for BMI, age, stage, tumor grade, ER/PR, and Her-2 neu status. Differences in leptin and adiponectin levels between races were assessed using the Kruskal-Wallis test. Linear regression was used to detect differences in levels after adjusting for BMI. Results: Mean levels of leptin and adiponectin were significantly higher in African-American women, compared to White women. Mean leptin levels were 57.8 ng/ml and 30.1 ng/ml in African-American and White women, respectively (p<0.001). Mean adiponectin levels were 24.68 ng/ml and 19.19 ng/ml in African-American and White women, respectively (p=0.006). A persistently significant difference in both leptin and adiponectin between racial groups remained after adjustment for BMI. Adiponectin levels were positively correlated with higher grade tumors (p=0.04). There was a trend of a positive correlation between leptin and higher grade tumors, but this association did not reach statistical significance (p=0.057). We found no correlation between adiponectin and leptin and stage at diagnosis, ER/PR, Her-2/neu status, orage. Conclusions: Our findings suggest that adipocytokine levels may differ by race in women with breast cancer, adjusted for BMI. There may also be a positive correlation between adipocytokine levels and higher tumor grade in women with breast cancer. Our study population was small, and we will validate the results in a larger sample size. If the results are demonstrated in further studies, differences in adipocytokine levels may prove to be a biologic cause of some of the observed racial disparities in women with breast cancer. Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):B74.