Abstract 1990: Effects of pomegranate extract on proliferation, apoptosis and mRNA expression in human breast cancer cells

Abstract

Abstract Pomegranates (Punica granatum L.) contain a mixture of phytochemicals such as ellagitannins, ellagic acid and anthocyanins and possess antioxidant and anticancer activities. Pomegranate juice, aqueous pomegranate extract or seed oil reduces growth of different cancer cell lines and human prostate and lung cancer xenografts. Although several potential mechanisms such as stimulation of apoptosis, inhibition of inflammation and angiogenesis have been identified, further mechanistic investigations, especially in breast cancer, are needed. In this study, we examined the growth inhibitory effects of PE in association with antioxidant activity and global gene expression changes in MCF-7 breast cancer cells. PE caused a time and concentration-dependent inhibition of cell proliferation associated with the G2/M cell cycle arrest. In addition, PE induced apoptosis in a concentration-dependent manner. High antioxidant activity of PE was confirmed using the Trolox Equivalent Antioxidant Capacity assay (Trolox assay). Our data shows that 50 µg/ml of PE, which inhibits 50% of cell growth, is equivalent to 75 µg/ml of Trolox, a water-soluble vitamin E analog, and 40 µg/ml of N-acetyl Cysteine, a well-known low molecular weight thiol antioxidant. To understand whether the antioxidant activity of PE contributed to the observed cell growth inhibition, we determined whether PE (dose range 0-50 µg/ml) and equivalent doses of N-acetyl Cysteine and Trolox inhibit MCF-7 cell growth. Only PE but not equivalent doses N-acetyl Cysteine and Trolox inhibited cell growth suggesting that the growth inhibition of PE cannot solely be attributed to its antioxidant potential. To get insight into the molecular mechanisms of action of PE we conducted gene expression profiling on the cells treated with 50% growth inhibitory dose of PE using Affymetrix Human Gene 1.0 ST Array. Our data showed that 903 gene entities were altered by PE treatment (1.5-fold cut-off, p<0.05), from which 398 were downregulated, while 505 were upregulated. Most of the genes that were downregulated by PE treatment affect processes associated with mitosis, chromosomal organization and segregation, DNA replication, DNA recombination and repair, whereas most upregulated genes constitute genes involved in the regulation of apoptosis and cell cycle. Of particular interest, PE downregulated important DNA damage response and repair genes including genes of MRE11-RAD50-NBS1 complex and BRCA1-associated genome surveillance complex. Given that targeting of DNA repair in cancer may sensitize cancer cells to drugs, these findings may have a translational potential. We are currently validating the genes at their mRNA and protein levels to identify novel ‘pomegranate-target gene’ interactions that are relevant to breast cancer. It may provide novel molecular and cellular targets for pomegranate-based anticancer approaches. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1990. doi:1538-7445.AM2012-1990