Effect of Black Raspberry Extract in Inhibiting NFκ B Dependent Radioprotection in Human Breast Cancer Cells

Abstract

Black raspberry extracts (RSE) have been shown to inhibit cancer cell growth and stimulate apoptosis. Also, studies have demonstrated that RSE inhibits transcriptional regulators including NF κ B. Accordingly, we investigated the effect of RSE in inhibiting radiation (IR) induced NF κ B mediated radioprotection in breast adenocarcinoma cells. MCF-7 cells were exposed to IR (2Gy), treated with RSE (0.5, 1.0, 2.0 μ g/ml) or treated with RSE (1.0 μ g/ml) followed by IR exposure, and harvested after 1, 3, 6, 24, 48, and 72 h. NF κ B DNA-binding activity was measured by EMSA and phosphorylated I κ B α by immunoblotting. Expression of IAP1, IAP2, XIAP and survivin were measured by QPCR and immunoblotting. Cell survival was measured using MTT assay and cell death using Caspase-3/7 activity. Effect of RSE on IR induced MnSOD, TNF α , IL-1 α and MnSOD activity was also determined. RSE inhibited NF κ B activity in a dose-dependent manner. Also, RSE inhibited IR-induced sustained activation of NF κ B, and NF κ B regulated IAP1, IAP2, XIAP, and survivin. In addition, RSE inhibited IR-induced TNF α , IL-1 α , and MnSOD levels and MnSOD activity. RSE suppressed cell survival and enhanced cell death. These results suggest that RSE may act as a potent radiosensitizer by overcoming the effects of NF κ B mediated radioprotection in human breast cancer cells.

ACKNOWLEDGMENTS

We thank Salahuddin Ahmad and Daniel A. Johnson, Department of Radiation Oncology at the University of Oklahoma Health Sciences Center, for irradiator calibrations. This work was supported by the Department of Radiation Oncology research development funds and American Cancer Society institutional review grant (ACS-IRG-05-066-01) to N. Aravindan.