Wang, ZF, Chang TC.
2012.
Molecular engineering of G-quadruplex ligands based on solvent effect of polyethylene glycol, Sep 1. Nucleic Acids Res. 40:8711-20., Number 17
AbstractBecause various non-parallel G-quadruplexes of human telomeric sequences in K+ solution can be converted to a parallel G-quadruplex by adding polyethylene glycol (PEG) as a co-solvent, we have taken advantage of this property of PEG to study the covalent attachment of a PEG unit to a G-quadruplex ligand, 3,6-bis(1-methyl-4-vinylpyridinium) carbazole diiodide (BMVC). The hybrid ligand with the PEG unit, BMVC-8C3O or BMVC-6C2O by substituting either the tetraethylene glycol or the triethylene glycol terminated with a methyl-piperidinium cation in N-9 position of BMVC, not only induces structural change from different non-parallel G-quadruplexes to a parallel G-quadruplex but also increases the melting temperature of human telomeres in K+ solution by more than 45 degrees C. In addition, our ligand work provides further confidence that the local water structure plays the key to induce conformational change of human telomere.
Huang, FC, Chang CC, Wang JM, Chang TC, Lin JJ.
2012.
Induction of senescence in cancer cells by the G-quadruplex stabilizer, BMVC4, is independent of its telomerase inhibitory activity, Sep. Br J Pharmacol. 167:393-406., Number 2
AbstractBACKGROUND AND PURPOSE: Telomerase is the enzyme responsible for extending G-strand telomeric DNA and represents a promising target for treatment of neoplasia. Inhibition of telomerase can be achieved by stabilization of G-quadruplex DNA structures. Here, we characterize the cellular effects of a novel G-quadruplex stabilizing compound, 3,6-bis(4-methyl-2-vinylpyrazinium iodine) carbazole (BMVC4). EXPERIMENTAL APPROACH: The cellular effects of BMVC4 were characterized in both telomerase-positive and alternative lengthening of telomeres (ALT) cancer cells. The molecular mechanism of how BMVC4 induced senescence is also addressed. KEY RESULTS: BMVC4-treated cancer cells showed typical senescence phenotypes. BMVC4 induced senescence in both ALT and telomerase-overexpressing cells, suggesting that telomere shortening through telomerase inhibition might not be the cause for senescence. A large fraction of DNA damage foci was not localized to telomeres in BMVC4-treated cells and BMVC4 suppressed c-myc expression through stabilizing the G-quadruplex structure located at its promoter. These results indicated that the cellular targets of BMVC4 were not limited to telomeres. Further analyses showed that BMVC4 induced DNA breaks and activation of ataxia telangiectasia-mutated mediated DNA damage response pathway. CONCLUSIONS AND IMPLICATIONS: BMVC4, a G-quadruplex stabilizer, induced senescence by activation of pathways of response to DNA damage that was independent of its telomerase inhibitory activity. Thus, BMVC4 has the potential to be developed as a chemotherapeutic agent against both telomerase positive and ALT cancer cells.
Chang, CC, Hsieh MC, Lin JC, Chang TC.
2012.
Selective photodynamic therapy based on aggregation-induced emission enhancement of fluorescent organic nanoparticles, Jan. Biomaterials. 33:897-906., Number 3
AbstractThree binary molecule conjugates were designed and synthesized by conjugating a chromophore (3, 6-bis-(1-methyl-4-vinylpyridinium)-carbazole diiodide, BMVC) to mono-, bis- and trishydroxyl photosensitizers, respectively. BMVC plays the role of cancer cells recognizer; AIEE (aggregation-induced emission enhancement) generator and FRET (Fluorescence Resonance Energy Transfer) donor. The self assembling properties of these binary conjugates result in different degrees of AIEE and then achieve the formations of FONs (fluorescent organic nanoparticles), which present efficient FRET and singlet oxygen generations. Biologically, FONs-photosensitizers from these compounds were much more phototoxicities to cancer cell than to normal cell without significant dark toxicity. In addition, their intracellular fluorescent colors switching upon photo-excitation are expected to be used for further cell death biomarker applications. This improved photodynamic activity might be due to the aggregation of compounds in the cell that form FONs which can promote PDT (photodynamic therapy) and are observed in cancer cell but not normal cell.
Chien, CH, Chen WW, Wu JT, Chang TC.
2012.
Investigation of lipid homeostasis in living Drosophila by coherent anti-Stokes Raman scattering microscopy, Dec. J Biomed Opt. 17:126001., Number 12
AbstractTo improve our understanding of lipid metabolism, Drosophila is used as a model animal, and its lipid homeostasis is monitored by coherent anti-Stokes Raman scattering microscopy. We are able to achieve in vivo imaging of larval fat body (analogous to adipose tissue in mammals) and oenocytes (analogous to hepatocytes) in Drosophila larvae at subcellular level without any labeling. By overexpressing two lipid regulatory proteins--Brummer lipase (Bmm) and lipid storage droplet-2 (Lsd-2)--we found different phenotypes and responses under fed and starved conditions. Comparing with the control larva, we observed more lipid droplet accumulation by approximately twofold in oenocytes of fat-body-Bmm-overexpressing (FB-Bmm-overexpressing) mutant under fed condition, and less lipid by approximately fourfold in oenocytes of fat-body-Lsd-2-overexpressing (FB-Lsd-2-overexpressing) mutant under starved condition. Moreover, together with reduced size of lipid droplets, the lipid content in the fat body of FB-Bmm-overexpressing mutant decreases much faster than that of the control and FB-Lsd-2-overexpressing mutant during starvation. From long-term starvation assay, we found FB-Bmm-overexpressing mutant has a shorter lifespan, which can be attributed to faster consumption of lipid in its fat body. Our results demonstrate in vivo observations of direct influences of Bmm and Lsd-2 on lipid homeostasis in Drosophila larvae.
Chang, TC, Chu JF, Tsai YL, Wang ZF.
2012.
Structure conversion and structure separation of G-quadruplexes investigated by carbazole derivatives. Curr Pharm Des. 18:2002-13., Number 14
AbstractThe challenge of G-quadruplexes is that the G-rich sequences can adopt various G4 structures and possibly interconvert among them, particularly under the change of environmental conditions. Both NMR and circular dichroism (CD) show the spectral conversion of d[AG3(T2AG3)3] (HT22) from Na-form to K-form after Na+/K+ ion exchange. No appreciable change on the induced CD spectra of BMVC molecule and the single molecule tethered particle motion of HT22 in Na+ solution upon K+ titration suggests that the spectral conversion is unlikely due to the structural conversion via fully unfolded intermediate. Although a number of mechanisms were proposed for the spectral change induced by the Na+/K+ ion exchange, determining the precise structures of HT22 in K+ solution may be essential to unravel the mechanism of the structural conversion. Thus, development of a new method for separating different structures is of critical importance for further individual verification. In the second part of this review, we describe a new approach based on "micelle-enhanced ultrafiltration" method for DNA structural separation. The BMVC, a G-quadruplex ligand, is first modified and then forms a large size of emulsion after ultrasonic emulsification, together with its different binding affinities to various DNA structures; for the first time, we are able to separate different DNA structures after membrane filtration. Verification of the possible structural conversion and investigation of structural diversity among various G4 structures are essential for exploring their potential biological roles and for developing new anticancer drugs.