Abstract 3653: Cytotoxicity of curcumin combined with docetaxel at low or high dose implicates the antioxidant response and the glutathione cycle in MCF7 tumor cells: A metabolomics analysis
Authors: Bayet-Robert Mathilde , Planchat Eloïse , Durando Xavier , Barthomeuf Chantal , Chollet Philippe , Morvan Daniel 
Published: February 2011

Abstract
Curcumin (CCM) has antioxidant and chemopreventive properties at low dose. However, at high dose, it exhibits prooxidant activity. Recently, we showed using pharmacometabolomics that MCF7 cells response to docetaxel (DTX) involved, at low dose (1 nM), blockade of glutathione (GSH) biosynthesis, whereas, at high dose (5 µM), extensive GSH consumption. Cytotoxicity was significant even at low dose DTX. Here, we investigated whether CCM at 10 mg/l, a dose stimulating GSH synthesis, may interfere with GSH metabolism, reactive oxygen species (ROS) production, and cytotoxicity when combined to DTX at low and high doses.
MCF7 cells were exposed for 72h to DTX at 1 nM and 5 µM in combination with 10 mg/l CCM as a 24h-pretreatment (PRE), cotreatment (CO) and 24h- and 48h-posttreatment (POST24 and POST48). Cytotoxicity was assessed from DNA content (Hoescht 33342), and ROS production from DNA strand breaks (Comet assay). Metabolomics analysis used high resolution magic angle spinning 1H-NMR spectroscopy, 2D spectral acquisitions and a new 2D-based quantification procedure, enabling to measure 32 metabolites. We focused on the variations of 13 metabolites from the GSH metabolism.
Overall cytotoxicity of combinations increased according to POST48&lt;POST24&lt;CO&lt;PRE (all, P&lt;0.05), and ROS production was increased in PRE and CO (both, P&lt;0.05), at low and high dose DTX.
Metabolomics analysis of PRE at low and high dose DTX involved the preservation of GSH levels but an accumulation of 5-oxoproline (OP, X3.85 at 1 nM and X5.90 at 5 µM, both P&lt;0.05), suggesting a blockade at oxoprolinase (OPase), step of the GSH cycle.
Metabolomics analysis of CO at low dose DTX showed an increase in GSH (X1.25, P&lt;0.05), together with starvation of most GSH precursors: glycine (Gly, X0.26, P&lt;0.05) and homocysteine (Hcy, X0.24, P&lt;0.05)). At high dose DTX, the GSH level was unchanged, but OP was increased (X4.26, P&lt;0.05).
Metabolomics analysis of POST24 at low dose DTX involved an increase in GSH (X1.22, P&lt;0.05) suggesting increased biosynthesis of GSH but at the expense of taurine (X0.44, P=NS). At high dose DTX, GSH level was maintained, but associated with an increase in glutamate (Glu, X1.73, P&lt;0.05).
Metabolomics analysis of POST48 at low dose DTX showed an increase in GSH (X1.21, P&lt;0.05) without signs of blockade of transsulfuration (Hcy X0.80, P=NS). At high dose DTX, the GSH level was maintained with mild signs of precursor starvation (Gly, X0.27, P&lt;0.05), and decreased Glu derivatives (P&lt;0.05), suggesting increased GSH biosynthesis and consumption.
In all combinations, CCM at 10 mg/l generated an antioxidant response in MCF7 cells, with preserved or increased GSH levels. However, the underlying biochemical mechanism was different. Maximal cytotoxicity was obtained in PRE conditions involving ROS production, probable OPase blockade with the accumulation of biomarker OP.
Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3653.