Association of the apoptotic effect of the coffee deterpene kahweol on human colon cancer cell with the expression of heat shock proteins (HSPs).

Abstract

622 Background: It has been reported that coffee has a preventative effect in several cancers because of its anti-oxidant, anti-inflammatory, and anti-tumor properties. However, there have been few reports about the effect and mechanism of coffee compounds in colorectal cancer. Heat shock proteins (HSPs) are molecular chaperones that prevent cell death. Their expression is significantly elevated in many tumors and is accompanied by increased cell proliferation, metastasis, and poor response to chemotherapy. Methods: We investigated the apoptotic effect of major components of coffee in the HT-29 human colon adenocarcinoma cells and evaluated the antitumor mechanism via the regulation of HSPs expression. HT-29 cells were cultured with bioactive compounds of coffee such as caffeine, chlorogenic acid, caffeic acid, and kahweol. Cell viability was determined by MTT and LDH assay according to the concentration of each component. Western blot assay was taken for evaluation of the apoptosis-related signals such as cleaved caspase-3, cleaved PAPR, Bcl-2, phospho-AKT(p-AKT), and HSPs including HSP40, HSP70, and HSP90. Results: Among the various coffee compounds, only kahweol showed significant anti-tumor cell activity, and cell death was observed in a concentration-dependent manner on MTT and LDH assay. Kahweol induced an increase in expression of cleaved caspase-3 and PAPR. In contrast, the reduction of anti-apoptotic proteins such as Bcl-2 and p-AKT was derived. HSPs including HSP40, HSP70, and HSP90 were decreased by kahweol treatment. HSP70 inhibitor such as quercetin and triptolide showed the significantly decreased viability of HT-29 cells. Conclusions: Kahweol had a cytotoxic effect on HT-29 cells via the apoptotic signal pathway in a concentration-dependent manner and inhibited the expressions of HSPs. HSP70 inhibitors showed tumor cell cytotoxicity, suggesting that HSP might play a significant role in the proliferation of cancer cells.