No abstract

Both epigallocatechin gallate (EGCG) and curcumin have shown efficacy in various in vivo and in vitro models of cancer. This study was designed to determine the efficacy of these naturally derived polyphenolic compounds in vitro and in vivo, when given in combination. Studies in MDA-MB-231 cells demonstrated that EGCG 1 curcumin was synergistically cytotoxic and that this correlated with G 2 /M-phase cell cycle arrest. After 12 hr, EGCG (25 lM) 1 curcumin (3 lM) increased the proportion of cells in G 2 /M-phase to 263 6 16% of control and this correlated with a 50 6 4% decrease in cell number compared to control. To determine if this in vitro result would translate in vivo, athymic nude female mice were implanted with MDA-MB-231 cells and treated with curcumin (200 mg/kg/day, po), EGCG (25 mg/kg/day, ip), EGCG 1 curcumin, or vehicle control (5 ml/kg/day, po) for 10 weeks. Tumor volume in the EGCG 1 curcumin treated mice decreased 49% compared to vehicle control mice (p < 0.05), which correlated with a 78 6 6% decrease in levels of VEGFR-1 protein expression in the tumors. Curcumin treatment significantly decreased tumor protein levels of EGFR and Akt, however the expression of these proteins was not further decreased following combination treatment. Therefore, these results demonstrate that the combination of EGCG and curcumin is efficacious in both in vitro and in vivo models of ERa-breast cancer and that regulation of VEGFR-1 may play a key role in this effect. ' 2007 Wiley-Liss, Inc.

Estrogen receptor (ER)-negative breast cancer is an aggressive form that currently requires more drug treatment options. Thus, we have further modified cyclohexanone derivatives of curcumin and examined them for cytotoxicity towards ER-negative human breast cancer cells. Two of the analogs screened elicited increased cytotoxic potency compared to curcumin and other previously studied derivatives. Specifically, 2,6-bis(pyridin-3-ylmethylene)-cyclohexanone (RL90) and 2,6-bis(pyridin-4-ylmethylene)-cyclohexanone (RL91) elicited EC(50) values of 1.54 and 1.10 µM, respectively, in MDA-MB-231 cells and EC(50) values of 0.51 and 0.23 in SKBr3 cells. All other new compounds examined were less potent than curcumin, which elicited EC(50) values of 7.6 and 2.4 µM in MDA-MB-231 and SKBr3 cells, respectively. Mechanistic analyses demonstrated that RL90 and RL91 significantly induced G(2)/M-phase cell cycle arrest and apoptosis. RL90 and RL91 also modulated the expression of key cell signaling proteins, specifically, in SKBr3 cells, protein levels of Her-2, Akt, and NFκB were decreased in a time-dependent manner, while activity of stress kinases JNK1/2 and P38 MAPK were increased. Signaling events in MDA-MB-231 cells were differently implicated, as EGFR protein levels were decreased and activity of GSK-3β transiently decreased, while β-catenin protein level and activity of P38 MAPK, Akt, and JNK1/2 were transiently increased. In conclusion replacement of the phenyl group of cyclohexanone derived curcumin derivatives with heterocyclic rings forms a class of second-generation analogs that are more potent than both curcumin and other derivatives. These new derivatives provide a platform for the further development of drugs for the treatment of ER-negative breast cancer.

Phytochemicals have provided an abundant and effective source of therapeutics for the treatment of cancer. Here we describe the characterization of a novel plant toxin, persin, with in vivo activity in the mammary gland and a p53-, estrogen receptor -, and Bcl-2-independent mode of action. Persin was previously identified from avocado leaves as the toxic principle responsible for mammary gland -specific necrosis and apoptosis in lactating livestock. Here we used a lactating mouse model to confirm that persin has a similar cytotoxicity for the lactating mammary epithelium. Further in vitro studies in a panel of human breast cancer cell lines show that persin selectively induces a G 2 -M cell cycle arrest and caspase-dependent apoptosis in sensitive cells. The latter is dependent on expression of the BH3-only protein Bim. Bim is a sensor of cytoskeletal integrity, and there is evidence that persin acts as a microtubule-stabilizing agent. Due to the unique structure of the compound, persin could represent a novel class of microtubule-targeting agent with potential specificity for breast cancers. [Mol Cancer Ther 2006;5(9):2300 -9]