ABSTRACT
Marine organisms provide several biologically active compounds that include alkaloids with high cytotoxic activity but only a few of them have so far reached clinical stage, due partly to their limited supply and complex structural features. In an attempt to develop novel anticancer compounds, we have now synthesized diaminoindoloylthiazoles (4a-c; DIT1-3) and diaminocinnamoylthiazoles (5a,b; DCT1-2) as analogs based on a topsentin scaffold and investigated the cytotoxic and apoptotic activities of these compounds in HeLa cells. The results suggest that diaminoindoloylthiazoles (DIT1-3) inhibit cell growth and among these, DIT3 is the most cytotoxic against HeLa cells (IC50 1 µM). The diaminocinnamoylthiazoles DCT1 and DCT2, which can be viewed as curcumin-diaminothiazole hybrids, also inhibited cell growth but at relatively higher concentrations with IC50 values of 60 and 30 µM, respectively. These compounds induced apoptosis through the intrinsic pathway by reducing the mitochondrial membrane potential and activating caspases, 9 and 3, but not caspase 8. Among the marine alkaloid analogs tested in this study, DIT1-3 are very effective in inducing apoptosis of HeLa cells followed by DCT2 and DCT1. The treated cells were arrested in G2/M phase followed by accumulation of the cells in the Sub G0 phase. The curcumin-diaminothiazole hybrid DCT1 had the maximum effect in downregulating TNF-induced NF-κB activation among the compounds tested in this study. Thus, we demonstrate that diaminoindoloylthiazoles and diaminocinnamoylthiazoles induce apoptosis, regulate cell cycle and NF-κB signaling and thus show promising anticancer effects that warrant further investigation.
Subject(s)
Alkaloids/chemical synthesis , Apoptosis/physiology , Imidazoles/chemical synthesis , Indoles/chemical synthesis , Thiazoles/chemical synthesis , Alkaloids/chemistry , Alkaloids/pharmacology , Animals , Apoptosis/drug effects , Caspase 3/metabolism , Caspase 9/metabolism , Cell Proliferation/drug effects , Cinnamates/chemical synthesis , Cinnamates/chemistry , Cinnamates/pharmacology , Dose-Response Relationship, Drug , Enzyme Activation/drug effects , Flow Cytometry , G2 Phase Cell Cycle Checkpoints/drug effects , HeLa Cells , Humans , Imidazoles/chemistry , Imidazoles/pharmacology , Indoles/chemistry , Indoles/pharmacology , Inhibitory Concentration 50 , Membrane Potential, Mitochondrial/drug effects , Models, Chemical , Molecular Structure , NF-kappa B/metabolism , Porifera/chemistry , Seawater/parasitology , Signal Transduction/drug effects , Thiazoles/chemistry , Thiazoles/pharmacology , Tumor Necrosis Factor-alpha/pharmacologyABSTRACT
The prevention of neovessel formation or angiogenesis is a recent popular strategy for limiting and curing cancer. Diaminothiazoles are a class of compounds that have been reported to show promise in the treatment of cancer by inhibiting cancer cell proliferation and inducing apoptosis, because of their effects on microtubules and as inhibitors of cyclin-dependent kinases. Many microtubule-targeting agents are being studied for their antiangiogenic activity, and a few have shown promising activity in the treatment of cancer. Here, we report that diaminothiazoles can be highly effective as antiangiogenic agents, as observed in the chick membrane assay. The lead compound, 4-amino-5-benzoyl-2-(4-methoxyphenylamino)thiazole (DAT1), inhibits endothelial cell processes such as invasion, migration, and tubule formation, which require a functional cytoskeleton. DAT1 also decreases the expression of cell adhesion markers. The antiangiogenic activities of DAT1 occur at concentrations that are not cytotoxic to the normal endothelium. Analysis of intracellular signaling pathways shows that DAT1 inhibits Akt phosphorylation, which is actively involved in the angiogenic process. The antiangiogenic properties of diaminothiazoles, in addition to their promising antimitotic and cytotoxic properties in cancer cell lines, give them an extra advantage in the treatment of cancer.
