Date of Award

12-2009

Degree Name

Master of Science

Department

Molecular Cellular and Systemic Physiology

First Advisor

Murphy, Laura

Abstract

Ginsenosides (GF) are a major bioactive constituent of ginseng and have been shown to elicit a multitude of actions ranging from the improvement of synaptic plasticity to the improved uptake of glucose into a cell. Furthermore, ginsenosides and their metabolites have been shown to be potent anti-cancer agents in multiple experimental cancer models. The aim of this study was to investigate the potential influence of GF derived from American ginseng root (Panax quinquefolius), and a ginsenoside metabolite Rh2, on tumor necrosis factor-α (TNF-α) cytotoxicity in MDA-MB 231 and MCF-7 human breast cancer cells. In combination, these agents significantly increased cell death in both cell lines. Together, ginsenosides and TNF-α induced a robust increase of the pre-G0/G1 and accompanying decrease in S phase cell populations in breast cancer cells. This cell death was the result of the induction of apoptosis, as determined by annexin-V/7-AAD and Hoechst staining. Furthermore, the mechanism of ginsenoside and TNF-α induced apoptosis is caspase-dependent, as determined by the pan-caspase inhibitor Z-VAD-FMK, with caspase-8, but not caspase-9, serving as initiator caspase in both cell lines. Additionally, ginsenoside treatment significantly XIAP expression in both MDA-MB 231 and MCF-7 cells, in the absence of TNF-α. In addition to enhancing apoptosis, it was also hypothesized that ginsenosides would abrogate pro-survival pathways induced by TNF-α. However, ginsenosides failed to block TNF-α effects on NFκB expression in either cell line. JNK which, when activated by TNF-α in MDA-MB 231 cells has a pro-survival function, was reduced by ginsenosides. However, JNK inhibition had no effect on cell death, suggesting that it does not play an integral role in the mechanism of action. In MCF-7 cells, JNK has been shown to have a pro-apoptotic function. Treatment with ginsenosides had no effect on TNF-α activation of JNK, but inhibition of JNK significantly reduced cell death in combined ginsenoside and TNF-α treated cells. To conclude, combined treatment with ginsenosides and TNF-α can enhance cell death in the sensitive MCF-7 cell line, and induce cell death in the insensitive MDA-MB 231 cell line in a caspase-dependent manner that is aided by the reduction of XIAP by ginsenosides.

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