Inhibitors of histone deacetylases (HDACs) are a promising class of anticancer agents that have an effect on gene regulation. The naturally occurring cyclic depsipeptide FK228 containing disulfide and Largazole possessing thioester functionalities act as pro-drugs and share the same HDAC inhibition mechanism in cell. Inspired from these facts, we have reported bicyclic tetrapeptide disulfide HDAC inhibitors resembling FK228 with potent activity and enhanced selectivity. In the present study, we report the design and synthesis of several mono and bicyclic tetrapeptide thioester HDAC inhibitors that share the inhibition mechanism similar to Largazole. Most of the compounds showed HDAC1 and HDAC4 inhibition and p21 promoting activity in nanomolar ranges. Among these the monocyclic peptides 1, 2 and bicyclic peptide, 4 are notable demanding more advanced research to be promising anticancer drug candidates.
(R)-(+)-Goniothalamin (GTN), a styryl-lactone isolated from the medicinal plant Goniothalamus macrophyllus, exhibits pharmacological activities including cytotoxic and anti-inflammatory effects. In this study, GTN modulated TNF-α induced NF-κB activation. GTN concentrations up to 20 μM showed low cytotoxic effects in K562 chronic myelogenous leukemia and in Jurkat T cells. Importantly, at these concentrations, no cytotoxicity was observed in healthy peripheral blood mononuclear cells. Our results confirmed that GTN inhibited tumor necrosis factor-α (TNF-α)-induced NF-κB activation in Jurkat and K562 leukemia cells at concentrations as low as 5 μM as shown by reporter gene assays and western blots. Moreover, GTN down-regulated translocation of the p50/p65 heterodimer to the nucleus, prevented binding of NF-κB to its DNA response element and reduced TNF-α-activated interleukin-8 (IL-8) expression. In conclusion, GTN inhibits TNF-α-induced NF-κB activation at non-apoptogenic concentrations in different leukemia cell models without presenting toxicity towards healthy blood cells underlining the anti-leukemic potential of this natural compound.