Enzyme inhibitors from marine invertebrates

DNA methylation: a promising target for the twenty-first century

BACKGROUND

Over the last few years DNA methylation and its involvement in diseases such as cancer has become of great interest for applied research. Since reversal of aberrant DNA methylation may influence the behavior of tumors, the methylation of DNA CpG sites is a potential target for the development of inhibitors for use in cancer treatment.

OBJECTIVE/METHODS

We briefly review the structural and mechanistic features of DNA methylation, including a structural analysis of the three main human DNA methyltransferases and some (pre)clinical results.

RESULTS/CONCLUSION

Despite side effects, data obtained to date still support the vision that DNA-methylation, possibly associated with the use of histone deacetylases (HDACs) and/or artificial transcription factors (ATFs), is a promising target for improving anticancer therapy in the 21st century.

Meriolins, a new class of cell death inducing kinase inhibitors with enhanced selectivity for cyclin-dependent kinases

Protein kinases represent promising anticancer drug targets. We describe here the meriolins, a new family of inhibitors of cyclin-dependent kinases (CDK). Meriolins represent a chemical structural hybrid between meridianins and variolins, two families of kinase inhibitors extracted from various marine invertebrates. Variolin B is currently in preclinical evaluation as an antitumor agent. A selectivity study done on 32 kinases showed that, compared with variolin B, meriolins display enhanced specificity toward CDKs, with marked potency on CDK2 and CDK9. The structures of pCDK2/cyclin A/variolin B and pCDK2/cyclin A/meriolin 3 complexes reveal that the two inhibitors bind within the ATP binding site of the kinase, but in different orientations. Meriolins display better antiproliferative and proapoptotic properties in human tumor cell cultures than their parent molecules, meridianins and variolins. Phosphorylation at CDK1, CDK4, and CDK9 sites on, respectively, protein phosphatase 1alpha, retinoblastoma protein, and RNA polymerase II is inhibited in neuroblastoma SH-SY5Y cells exposed to meriolins. Apoptosis triggered by meriolins is accompanied by rapid Mcl-1 down-regulation, cytochrome c release, and activation of caspases. Meriolin 3 potently inhibits tumor growth in two mouse xenograft cancer models, namely, Ewing's sarcoma and LS174T colorectal carcinoma. Meriolins thus constitute a new CDK inhibitory scaffold, with promising antitumor activity, derived from molecules initially isolated from marine organisms.

Application of a 6pi-1-azatriene electrocyclization strategy to the total synthesis of the marine sponge metabolite ageladine A and biological evaluation of synthetic analogues

A 12-step synthesis of the angiogenesis inhibitory marine metabolite ageladine A is reported. The key steps include a 6pi-1-azatriene electrocyclization for formation of the pyridine ring and a Suzuki-Miyaura coupling of N-Boc-pyrrole-2-boronic acid with a chloroimidazopyridine. In addition, an assessment of the biological activity of a variety of synthetic analogues of ageladine A prepared during this synthesis is described.