Curcumin and its derivative, new chemical genetics modifiers for cell signaling

다국어 초록 (Multilingual Abstract)

Curcumin is a phenolic natural product found in the rhizome of Curcuma longa(turmeric). Recently, curcumin was shown to inhibit chemical carcinogen-induced tumor formation in mice and the proliferation of various cultured tumor cells. Moreover, curcumin inhibited corneal neovascularization without inhibiting TPA-induced secretion of vascular endothelial growth factor(VEGF) from tumor cells. These studies demonstrate that the potent chemopreventive activity of curcumin may be, in part, derived from the direct inhibition of in vivo angiogenesis. To date, however, the biochemical mechanism of inhibition of angiogenesis by curcumin has not been uncovered yet.
Using reverse chemical genetics approach, we discovered that curcumin binds to and inhibits CD13/aminopeptidase N(APN). APN is a membrane-bound, zinc-dependent metalloproteinase that is believed to play a key role in tumor invasion and angiogenesis. Curcumin irreversibly inhibited APN activity both in vitro and in vivo. Moreover, curcumin dose-dependently competed the binding of APN-specific antibody to the enzyme in HUVEC cells. However, curcumin did not inhibit the invasion of APN-negative tumor cells, suggesting that anti-invasive activity of curcumin against tumor cells is attributable to the inhibition of APN. These data demonstrate that curcumin is a new irreversible inhibitor of APN, which is one of functional targets of curcumin for antiangiogenic activity.
These interesting biological and chemical properties of curcumin have led us to develop several curcumin derivatives that can be utilized as chemical genetics modifiers. Interestingly, two new curcumin derivatives, hydrazinocurcumin(HC) and hydrazinobenzatecurcumin(HBC), potently inhibited the proliferation of several mammalian cells without inhibiting the activity of APN. It has been speculated that there may be a new target protein of two compounds other than APN, which is involved in common pathways in cellular proliferation. To identify the functional target of HBC, forward chemical genetics approach using phage display biopanning analysis was conducted with a synthetic bioactive biotinylated probe of HBC. Our results show that HBC directly binds to Ca^(2+)/calmodulin(Ca^(2+)/CaM) and regulates its biological functions. These data demonstrate that Ca^(2+)/CaM is a functional target of HBC in the cells and suggest that HBC can be used as a new chemical genetics modifier to study the function of Ca^(2+)/CaM in cell signaling.
In summary, the present study provides new chemical genetics modifiers bearing curcumin pharmacophore for cell signaling as well as for development of new drugs targeting cancer.