Loss of Mitochondrial Localization of Human FANCG Causes Defective FANCJ Helicase.

Fanconi anemia (FA) is a unique DNA damage repair pathway. To date, 22 genes have been identified that are associated with the FA pathway. A defect in any of those genes causes genomic instability, and the patients bearing the mutation become susceptible to cancer. In our earlier work, we identified that Fanconi anemia protein G (FANCG) protects the mitochondria from oxidative stress. In this report, we have identified eight patients having a mutation (C.65G>C), which converts arginine at position 22 to proline (p.Arg22Pro) in the N terminus of FANCG. The mutant protein, hFANCGR22P, is able to repair the DNA and able to retain the monoubiquitination of FANCD2 in the FANCGR22P/FGR22P cell. However, it lost mitochondrial localization and failed to protect mitochondria from oxidative stress. Mitochondrial instability in the FANCGR22P cell causes the transcriptional downregulation of mitochondrial iron-sulfur cluster biogenesis protein frataxin (FXN) and the resulting iron deficiency of FA protein FANCJ, an iron-sulfur-containing helicase involved in DNA repair.

New dibutyltin(IV) ladders: Syntheses, structures and, optimization and evaluation of cytotoxic potential employing A375 (melanoma) and HCT116 (colon carcinoma) cell lines in vitro.

Synthesis and spectroscopic properties of seven new dibutyltin(IV) compounds of 2-{(E)-4-hydroxy-3-[(E)-4-(aryl)iminomethyl]phenyldiazenyl}benzoic acids (LnHH'; n=2-8) with general formula {[Bu2Sn(LnH)]2O}2 (1-7) are reported. The compounds were characterized by elemental analysis and by UV-Visible, fluorescence, IR, 1H, 13C and 119Sn NMR spectroscopies. Solid state structures of dibutyltin(IV) compounds 1-3, 6 and 7 were accomplished from single crystal X-ray crystallography which reveal the common ladder-type structure with two endo- and two exo-Sn atoms. The redox properties of LnHH' (n=2-4, 7 and 8) and their diorganotin(IV) compounds 1-3, 6 and 7 were also investigated by cyclic voltammetry. In general, the dibutyltin(IV) derivatives exhibited significant in vitro cytotoxic potency towards A375 (melanoma) and HCT116 (colon carcinoma) cell lines as determined by several experiments, like Live and Dead assay, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability assay, LDH (lactate dehydrogenase), cleavage of caspases and PARP (poly(ADP-ribose)polymerase), and DNA fragmentation. Dibutyltin(IV) compounds increase cell death without cytolysis and decreases membrane fluidity, without interfering with p53. Among the dibutyltin(IV) compounds, compound 6 was found to be the most potent, with an IC50 value of 78nM. A mechanism of action for tumor cell death is proposed.

Synthesis, photophysical properties and structures of organotin-Schiff bases utilizing aromatic amino acid from the chiral pool and evaluation of the biological perspective of a triphenyltin compound.

Five new organotin(IV) complexes of compositions [Me2SnL1] (1), [Me2SnL2]n (2), [Me2SnL3] (3), [Ph3SnL1H]n (4) and [Ph3SnL3H] (5) (where L1=(2S)-2-((E)-((Z)-4-hydroxypent-3-en-2-ylidene)amino)-3-(1H-indol-3-yl)propanoate, L2=(2S)-(E)-2-((2-hydroxybenzylidene)amino)-3-(1H-indol-3-yl)propanoate and L3=(2S)-(E)-2-((1-(2-hydroxyphenyl)ethylidene)amino)-3-(1H-indol-3-yl)propanoate were synthesized and spectroscopically characterized. The crystal structures of 1-4 were determined. For the dimethyltin derivative 2, a polymeric chain structure was observed as a result of a long Sn∙∙∙O contact involving the exocyclic carbonyl oxygen-atom from the tridentate ligand of a neighboring Sn-complex unit. The tin atom in this complex has a distorted octahedral coordination geometry, in which the long Sn-O bond is almost trans to the tridentate ligand nitrogen-atom. In contrast, the dimethyltin(IV) complexes 1 and 3 displayed discrete monomeric structures where the tin atom has distorted trigonal-bipyramidal geometry with the two coordinating L oxygen atoms defining the axial positions. On the other hand, 4 is a chain polymer in the solid state. The ligand-bridged Sn atoms adopt a trans-Ph3SnO2 trigonal-bipyramidal configuration with equatorial phenyl groups. A carboxylato oxygen atom from one and the hydroxyl oxygen of the successive ligand in the chain occupy the axial positions. The solution structures were predicted by the use of 119Sn NMR chemical shifts. The photophysical properties of the complexes were investigated in the solid and in solution. The triphenyltin(IV) compound 4 was tested in detail ex vivo against A375 (human melanoma) cell line, exhibiting an IC50 value of 261nM to induce cell death as assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay without significant alteration of cytolysis as determined by lactate dehydrogenase (LDH) assay. Compound 4-mediated potent cell death was also determined by Live and Dead assay and caspase-mediated cleavage of poly-ADP ribose polymerase (PARP). Potent cell death activity was not observed in primary cells, like blood-derived peripheral mononuclear cells (PBMC). Compound 4 inhibited the diphenyl hexatriene (DPH) binding to cells and decreased the micro viscosity in a dose-dependent manner. Additionally, the ability of 4 and cyclodextrin (CD) to interact was determined by molecular modelling.

Suppression of microphthalmia-associated transcription factor, but not NF-kappa B sensitizes melanoma specific cell death.

Mutation in B-Raf leads to gain of function in melanoma and causes aggressive behavior for proliferation. Most of the therapeutics are ineffective in this scenario. However, regulation of this aggressive behavior by targeting the key molecules would be viable strategy to develop novel and effective therapeutics. In this report we provide evidences that the resveratrol is potent to regulate melanoma cell growth than other inducers of apoptosis. Resveratrol inhibits pronounced cell proliferation in melanoma than other tumor cell types. Cell cycle analysis using flow cytometry shows that the treatment with resveratrol results in S phase arrest. Resveratrol inhibits microphthalmia-associated transcription factor (MITF) and its dependent genes without interfering the MITF DNA binding in vitro. Resveratrol-mediated cell death is protected in MITF overexpressed cells and it is aggravated in MITF knocked down cells. These suggest the resveratrol-mediated decrease in MITF is the possible cause of melanoma cell death. Though resveratrol-mediated downregulation of NF-κB is responsible for cell apoptosis, but the downregulation of MITF is the main reason for melanoma-specific cell death. Thus, resveratrol can be effective chemotherapeutic agent against rapid proliferative melanoma cells.

Profilin potentiates chemotherapeutic agents mediated cell death via suppression of NF-κB and upregulation of p53.

The molecular mechanism by which Profilin acts as a tumor suppressor is still unclear. Several chemotherapeutic agents, used till date either have unfavorable side effects or acquired resistance in tumor cells. Our findings show that Profilin enhances cell death mediated by several chemotherapeutic-agents. The activation of NF-κB and its dependent genes, mediated by paclitaxel and vinblastine, was completely inhibited in Profilin overexpressing cells. This inhibition was due to the Profilin mediated attenuation of IκBα degradation, thereby preventing p65 nuclear translocation and low NF-κB DNA binding activity.Moreover, Profilin increases level of p53 in the presence of known inducers, such as doxorubicin, vinblastine, and benzofuran. This increased p53 level leads to enhanced cell death as indicated by activation of caspases 3, 8, 9, which results in cleavage of PARP.Furthermore, knocking down of p53 in Profilin overexpressing cells leads to decreased cell death. Ectopic expression of Profilin in HCT116 p53 knock out cells showed lesser cell death as compared to the HCT116 p53 wild type cells. For the first time, we provide evidences, which suggest that Profilin synergizes with chemotherapeutic drugs to induce tumor cell death by regulating NF-κB and p53. Thus, modulation of Profilin may be a useful strategy for effective combination therapy.

A natural xanthone increases catalase activity but decreases NF-kappa B and lipid peroxidation in U-937 and HepG2 cell lines.

Mangiferin, a C-glycosyl xanthone, has shown anti-inflammatory, antioxidant, and anti-tumorigenic activities. In the present study, we investigated the molecular mechanism for the antioxidant property of mangiferin. Considering the role of nuclear transcription factor kappa B (NF-κB) in inflammation and tumorigenesis, we hypothesized that modulating its activity will be a viable therapeutic target in regulating the redox-sensitive ailments. Our results show that mangiferin blocks several inducers, such as tumor necrosis factor (TNF), lypopolysaccharide (LPS), phorbol-12-myristate-13-acetate (PMA) or hydrogen peroxide (H2O2) mediated NF-κB activation via inhibition of reactive oxygen species generation. In silico docking studies predicted strong binding energy of mangiferin to the active site of catalase (-9.13 kcal/mol), but not with other oxidases such as myeloperoxidase, glutathione peroxidase, or inducible nitric oxide synthase. Mangiferin increased activity of catalase by 44%, but had no effect on myeloperoxidase activity in vitro. Fluorescence spectroscopy further revealed the binding of mangiferin to catalase at the single site with binding constant and binding affinity of 3.1×10(-7) M(-1) and 1.046 respectively. Mangiferin also inhibits TNF-induced lipid peroxidation and thereby protects apoptosis. Hence, mangiferin with its ability to inhibit NF-κB and increase the catalase activity may prove to be a potent therapeutic.