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Posted: July 25, 2008
Could metals help treat cancer?
(Nanowerk News) A fruitful collaboration between chemists and biologists has made it possible to identify the effects of a new class of molecules, polyoxometalates (1), primarily composed of metals and oxygen. These molecules are very powerful inhibitors of a specific protein kinase, CK2, an enzyme that is overactive in a number of cancers.
The enzyme's instrumental role in controlling cell proliferation and survival makes it an important target in the search for new medications. These results have just been published in the journal Chemistry and Biology ("Identification of Polyoxometalates as Nanomolar Noncompetitive Inhibitors of Protein Kinase CK2") by chemists from the Institut de chimie moléculaire (CNRS / UPMC) and biologists from the Institut de recherche en technologies et sciences pour le vivant (iRTSV, CEA de Grenoble / CNRS / Inserm.)
Structure of the protein kinase CK2 (left) and the structures of different polyoxometalate (POM) molecules (right). (Image: B. Hasenknopf)
Phosphorylation enzymes (2) , which include the protein kinase CK2, play a critical role in controlling cell proliferation. Deregulated protein kinase activity is implicated in a number of cancers, which has led to a recent surge in research on molecules that can inhibit the activity of these enzymes. The currently known CK2 inhibitors are all organic compounds that neutralize enzymatic activity by binding to its active site (3).
The contribution of the study carried out by the researchers at the Institut de chimie moléculaire and the Institut de recherche en technologies et sciences pour le vivant was to reveal a new class of CK2 inhibitors. The new inhibitors are inorganic molecules, polyoxometalates (POMs), primarily made up of metals (molybdenum and tungsten) and oxygen. They are the most powerful CK2 inhibitors yet discovered, working at very low (nanomolar) concentrations. In addition, the researchers showed that the mode of action of POMs, although not yet fully understood, is completely new. Unlike organic inhibitors, POMs do not bind to the active site of the enzyme.
This work opens up several areas for further research: clarifying the mechanism of action of these new molecules, finding the minimum molecular entity that can inhibit enzyme activity, and finally, given its importance in the health field, improving knowledge of how the enzyme CK2 works. In the longer term, these results could pave the way for new approaches to developing anti-cancer drugs.
(1) Polyoxometalates are anionic inorganic metal oxide structures that have valuable catalytic properties.
(2) Phosphorylation enzymes called protein kinases can attach a phosphate group to proteins that may be inactive enzymes. The addition of the phosphate group can activate these “silent” enzymes. Protein kinases thus play a central role in controlling the activity of numerous enzymes in the cell.
(3) The active site of an enzyme is a particular region where the substrates bind together and enzymatic reactions takes place.