Aranorosin and a novel derivative inhibit the anti-apoptotic functions regulated by Bcl-2.

Bcl-2 is an intracellular membrane protein that prevents cells from undergoing apoptosis in response to various cell-death signals. It negatively regulates mitochondrial outer membrane permeabilization, which is responsible for the release of apoptogenic factors and the subsequent activation of caspases. A microbial metabolite, aranorosin, was identified as an inhibitor of the anti-apoptotic function of Bcl-2. Based on its structure, a more potent derivative, K050, was synthesized. Apoptosis could be induced in a cell line that overexpressed Bcl-2 when cells were treated with an anti-Fas antibody in addition to K050, at sub-micromolar concentrations. Furthermore, K050 inhibited anti-apoptotic functions regulated by Bcl-2, resulting in a Fas-triggered mitochondrial transmembrane potential loss, the activation of caspase-9, and a morphological change to apoptosis. Inhibition of cell-based function of Bcl-2 and its anti-apoptotic effects could serve as useful pharmacological effects. Thus, a novel aranorosin derivative, K050, could be a potent therapeutic agent against Bcl-2-overexpressing human malignancies.

Stressful death of T-ALL tumor cells after treatment with the anti-tumor agent Tetrocarcin-A.

The T-ALL cell lines CCRF-CEM and Jurkat were studied for their sensitivity toward apoptosis induced by tetrocarcin-A (TC-A), an antibacterial and antitumor agent isolated from the actinomycete Micromonospora. This substance promoted cell death via a mitochondrial signaling pathway, that is, by activation of Bid and Bax, loss of the mitochondrial transmembrane potential, release of cytochrome c, and activation of effector caspases, even under conditions of Bcl-2 overexpression. Furthermore, sensitivity to TC-A was not dependent on expression of wild-type caspase-8. In contrast, this apoptotic pathway was inhibited markedly by pretreatment of cells with cycloheximide, an inhibitor of de novo protein synthesis. cDNA microarray chip analysis revealed that TC-A induced a significant up-regulation of members of the heat shock protein family known to be involved in the endoplasmic reticulum (ER)-stress-induced apoptotic program. The activation of caspase-12, the central inducer caspase involved in ER-stress by TC-A treatment, is in concordance with this result. These results show that, in T-ALL cells, TC-A induces an apoptotic machinery via mitochondrial and ER signaling, which is not inhibited by aberrant expression/function of important regulators of death receptor- and drug-induced apoptosis.

Discovery and structure-activity relationships of novel piperidine inhibitors of farnesyltransferase.

A novel piperidine series of farnesyltransferase (FTase) inhibitors is described. Systematic medicinal chemistry studies starting with the lead compound, discovered from a 5-nitropiperidin-2-one combinatorial library, resulted in a potent series of novel FTase inhibitors. We found that all of four substituents of the piperidine core played an important role for FTase inhibition. A 10-fold increase in potency was observed by changing the piperidine-2-one core to the corresponding piperidine core. This class of compounds was found to inhibit farnesyltransferase in a Ras competitive manner. Optical resolution of several potent inhibitors revealed that the (+)-enantiomers showed potent farnesyltransferase inhibition. (+)-8 inhibited FTase with an IC(50) of 1.9 nM.

Design and synthesis of piperidine farnesyltransferase inhibitors with reduced glucuronidation potential.

The design and synthesis of a novel piperidine series of farnesyltransferase (FTase) inhibitors with reduced potential for metabolic glucuronidation are described. The various substitution and exchange of the phenyl group at the C-2 position of the previously described 2-(4-hydroxy)phenyl-3-nitropiperidine 1a (FTase IC(50)=5.4nM) resulted in metabolically stable compounds with potent FTase inhibition (14a IC(50)=4.3nM, 20a IC(50)=3.0nM, and 50a IC(50)=16nM). Molecular modeling studies of these compounds complexed with FTase and farnesyl pyrophosphate are also described.