The purpose of this study was to determine whether black cohosh contains constituents that inhibit the growth of human breast cancer cells, and therefore might eventually be useful in the prevention or treatment of breast cancer. Black cohosh rhizomes were extracted with methanol/water and fractionated by solvent-solvent partitioning to yield three fractions: hexane, ethyl acetate and water. The ethyl acetate fraction displayed the highest potency in two cell-based assays, growth inhibition and cell cycle analysis. This fraction inhibited growth of both the ER+ MCF7 and ER-MDA-MB-453 human breast cancer cell lines with IC50 values of about 20 and 10 micro g/ml, respectively. It also induced cell cycle arrest at G1 when tested at 30 micro g/ml and at G2/M at 60 micro g/ml in MCF7 cells. This suggests that the extract contains a mixture of components with the more active (or more abundant) causing G1 arrest and the less active causing G2/M arrest. We then examined specific components in this extract. The triterpene glycoside fraction obtained by polyamide column chromatography, and the specific triterpene glycosides actein, 23-epi-26-deoxyactein and cimiracemoside A, inhibited growth of the MCF7 human breast cancer cells and induced cell cycle arrest at G1. The most potent compound, actein, decreased the level of cyclin D1, cdk4 and the hyperphosphorylated form of the pRb protein and increased the level of p21cip1 in MCF7 cells, changes that may contribute to the arrest in G1. Further studies are in progress to identify the mechanisms by which actein and related compounds present in black cohosh inhibit growth of human breast cancer cells.

We previously reported that the garlic-derived compound S-allylmercaptocysteine (SAMC) causes growth inhibition, mitotic arrest, and induction of apoptosis in SW480 human colon cancer cells by inducing microtubule depolymerization and c-Jun NH 2 terminus kinase-1 activation. In the present study, we compared the aforementioned effects of SAMC to those of a series of garlic-derived and other organosulfur compounds. Among the 10 compounds tested, only SAMC, diallyl disulfide (DADS), and S-trityl-Lcysteine (trityl-cys) cause significant inhibition of cell growth with IC 50 values of 150, 56, and 0.9 Mmol/L, respectively. These three compounds also induce G 2 -M cell cycle arrest and apoptosis. Further studies reveal that, like SAMC, the garlic-derived compound DADS exerts antiproliferative effects by binding directly to tubulin and disrupting the microtubule assembly, thus arresting cells in mitosis and triggering mitochondriamediated signaling pathways that lead to apoptosis. However, the synthetic compound trityl-cys exerts its effect on M-phase arrest and growth inhibition by mechanisms that involve spindle impairment but do not involve disruption of microtubule structure or dynamics. Furthermore, trityl-cys does not induce marked loss of mitochondrial membrane potential or release of cytochrome c, but it does induce caspase-3 activation and poly(ADP-ribose) polymerase cleavage. Structure-function analysis suggests that both the allyl and the disulfide moieties are important features for the antiproliferative effects of SAMC and DADS. These findings may be useful in the identification, synthesis, and development of organosulfur compounds that have anticancer activity. [Mol Cancer Ther 2005;4(9):1388 -98]

Hepatoma is one of the most frequently occurring cancers worldwide. However, effective chemotherapeutic agents for this disease have not been developed. Acyclic retinoid, a novel synthetic retinoid, can reduce the incidence of postsurgical recurrence of hepatoma and improve the survival rate. OSI-461, a potent derivative of exisulind, can increase intracellular levels of cyclic GMP, which leads to activation of protein kinase G and induction of apoptosis in cancer cells. In the present study, we examined the combined effects of acyclic retinoid plus OSI-461 in the HepG2 human hepatoma cell line. We found that the combination of as little as 1.0 mol/L acyclic retinoid and 0.01 mol/L OSI-461 exerted synergistic inhibition of the growth of HepG2 cells. Combined treatment with low concentrations of these two agents also acted synergistically to induce apoptosis in HepG2 cells through induction of Bax and Apaf-1, reduction of Bcl-2 and Bcl-x L , and activation of caspase-3, -8, and -9. OSI-461 enhanced the G 0 -G 1 arrest caused by acyclic retinoid, and the combination of these agents caused a synergistic decrease in the levels of expression of cyclin D1 protein and mRNA, inhibited cyclin D1 promoter activity, decreased the level of hyperphosphorylated forms of the Rb protein, induced increased cellular levels of the p21 CIP1 protein and mRNA, and stimulated p21 CIP1 promoter activity. Moreover, OSI-461 enhanced the ability of acyclic retinoid to induce increased cellular levels of retinoic acid receptor ␤ and to stimulate retinoic acid response element-chloramphenicol acetyltransferase activity. A hypothetical model involving concerted effects on p21 CIP1 and retinoic acid receptor ␤ expression is proposed to explain these synergistic effects. Our results suggest that the combination of acyclic retinoid plus OSI-461 might be an effective regimen for the chemoprevention and chemotherapy of human hepatoma and possibly other malignancies.

A significantly simpler analog of the natural product migrastatin, termed migrastatin ether (ME), has been prepared and evaluated. Both in vivo and in vitro studies indicate that ME exhibits a concentration-dependent inhibitory effect on migration of breast cancer cells.

Exisulind (sulindac sulfone) and three highly potent derivatives, OSI-461 (CP461), OSIP486823 (CP248), and OSIP487703, inhibit growth and induce apoptosis in SW480 human colon cancer cells, with IC 50 s of 200, 2, 0.1, and 0.003 Mmol/L, respectively. The latter three compounds, but not exisulind, induce marked M-phase cell cycle arrest in these cells. This effect seems to be independent of the known ability of these compounds to cause activation of protein kinase G. When tested at twice their IC 50 concentration for growth inhibition, OSI-461, OSIP486823, and OSIP487703 cause depolymerization of microtubules in interphase cells, inhibit spindle formation in mitotic cells, and induce multinucleated cells. In vitro tubulin polymerization assays indicate that all three compounds interact with tubulin directly to cause microtubule depolymerization and/or inhibit de novo tubulin polymerization. These results suggest that the dual effects of OSI-461, OSIP486823, and OSIP487703 on impairment of microtubule functions and protein kinase G activation may explain the potent antiproliferative and apoptotic effects of these compounds in cancer cells. [Mol Cancer Ther 2006;5(1):60 -7]

We examined the effects of exisulind (sulindac sulfone) and a potent derivative CP248 on the Barrett's esophagus (BE)-related adenocarcinoma cell lines Seg-1 and Bic-1, and on HCE7 esophageal squamous carcinoma cells. Marked growth inhibition and apoptosis occurred in all cell lines with IC50 values of 100-300 microM for exisulind and 100 nM for CP248. Bic-1 and HCE7 cells were more sensitive to the growth inhibitory properties of exisulind. Treatment of all cell lines with CP248 for 24 h increased the proportion of cells in mitosis. Exisulind had no effect on cell-cycle progression. Treatment with either compound induced rapid activation of the c-Jun NH2-terminal kinase 1 (JNK1), suggesting that JNK1 activation plays a role in the induction of apoptosis by these compounds. Only Seg-1 cells expressed a detectable basal level of cyclooxygenase-2 (cox-2), providing further evidence that cox-2 is not the critical target for the growth inhibitory and apoptotic effects of these compounds. Cellular levels of reduced glutathione (GSH) increased approximately five-fold in all cell lines after 24 h of treatment with either compound. These studies provide support for the use of exisulind in BE chemoprevention trials, and of exisulind or CP248 in the therapy of patients with esophageal carcinoma.