BackgroundBreast cancer is a major problem in the United States leading to tens of thousands of deaths each year. Although citrus auraptene suppresses cancer in numerous rodent models, its role in breast cancer prevention previously has not been reported. Thus, our goal was to determine the anticarcinogenic effects of auraptene against breast cancer.MethodsThe effects of auraptene on cell proliferation of MCF-7 and MDA-MB-231 human breast carcinoma cells in culture was assessed by measuring metabolism of a substrate to a formazan dye. Dietary effects of auraptene on tumor incidence, multiplicity and latency were studied in the N-methyl nitrosourea (MNU) induced mammary carcinogenesis model in female Sprague Dawley rats. The concentration of auraptene in rat tissues was analyzed by reverse phase HPLC. Cyclin D1 expression in MCF-7 cells and rat tumors was measured by western blot.ResultsAuraptene (500 ppm) significantly delayed median time to tumor by 39 days compared to the MNU only group (p < 0.05, n = 24–26). Auraptene (10 μM) reduced Insulin like Growth Factor-1 (IGF-1, 10 ng/mL)-induced cyclin D1 expression by 40% in MCF-7 cells. In comparison, western blot analysis of rat mammary tumors (n = 10 per group) confirmed that auraptene (500 ppm) significantly reduced (p < 0.05) cyclin D1 expression by 49% compared to the MNU only group. Analysis of rat mammary tissue extract by HPLC with fluorescence detection indicated an average concentration (means ± S.E.) of 1.4 ± 0.5 μM and 1.8 ± 0.3 μM in the normal mammary glands of the auraptene 200 ppm and 500 ppm groups, respectively. The concentration (means ± S.E.) of auraptene in the mammary tumors of the auraptene 200 ppm group was 0.31 ± 0.98 μM.ConclusionOverall, these observations suggest that the predominant effect of auraptene was to delay the development of tumors possibly through the suppression of cyclin D1 expression. These results point to the potential chemopreventive effects of auraptene in mammary carcinogenesis.

Our goal was to determine the anticarcinogenic effects of auraptene against breast cancer. In human breast carcinoma, MDA‐MB‐231 cells, auraptene inhibited cell proliferation by 50% at 12 μM and by 85% at 25 μM. In the in vivo study using the N‐methylnitrosourea (MNU) induced rat mammary carcinogenesis model, female Sprague‐Dawley rats were fed control diet, or diets containing auraptene (200 or 500 ppm) , at 42 days of age till the end of the study. Since eIF4E is over expressed in human breast cancer, another group with rapamaycin, an inhibitor of eIF4E was included (3.33 ppm in the diet). Auraptene (500 ppm) significantly delayed median time to tumor by 39 days compared to MNU only group. Analysis of rat mammary glands by HPLC with fluorescence detection indicated auraptene reaching the mammary glands in micromolar concentrations. In the analysis of human breast cancer samples in a tissue micro array (TMA) format, expression of cyclin D1, c‐Myc, and ODC (ornithine decarboxylase)the downstream effector molecules of eIF4E of showed an upregulation in the cancer samples.We studied the expressionof ODC in the mammary tumors in the auraptene‐fed groups and saw a significant reduction (p<0.05) in the expression of ODC. Recent studies in MCF‐7 cells showed that auraptene and rapamycin reduced the expression of cyclin‐D1.These results point to the potential chemopreventive effects of auraptene in mammary carcinogenesis.This study was supported by NCI: 1K22 CA102005‐01A2