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1.  Stability-Indicating LC Method for the Determination of Prasugrel Hydrochloride in Pharmaceutical Dosage Form 
Scientia Pharmaceutica  2012;80(2):379-391.
A simple, rapid and precise method was developed for the quantitative estimation of prasugrel hydrochloride in pharmaceutical dosage form. A chromatographic separation of prasugrel and its degradants was achieved with Zorbax XDB C8, 150 × 4.6 mm, 3.5μm analytical column using aqueous solution of 0.05 M ammonium acetate pH 4.5 with acetic acid-acetonitrile (40:60 v/v). The instrumental settings include flow rate of 1.0 ml/min, column temperature at 30°C and detector wavelength of 254 nm using a photodiode array detector. Theoretical plates for prasugrel were 7023. Tailing factor for prasugrel was 1.11. Prasugrel was exposed to thermal, photolytic, hydrolytic and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. Peak homogeneity data of prasugrel was obtained using photodiode array detector in the stressed sample chromatograms, which demonstrated the specificity of the method for the estimation in presence of degradants. The described method showed excellent linearity over a range of 10–300 μg/ml for prasugrel. The correlation coefficient is 0.999. The relative standard deviation of peak area for six measurements is always less than 2%. Overall, the proposed method was found to be suitable and accurate for quantitative determination and stability study of prasugrel in pharmaceutical dosage form.
PMCID: PMC3383204  PMID: 22896824
Liquid chromatography; Method validation; Pharmaceutical preparation; Prasugrel hydrochloride
Neuro-Oncology  2014;16(Suppl 6):vi18.
INTRODUCTION: Brain metastases pose many challenges in terms of prognosis, complexity of tumour biology and tumour evolution. Here, we have analysed epigenetically deregulated candidate metastatic suppressor genes in metastatic brain tumours that evolved from primary breast tumours. Identified genes may be useful as prognostic markers that could be used to predict the risk of brain metastases from breast tumours or provide novel therapeutic targets. METHOD: We screened 80 genes that are epigenetically deregulated in cancer but not frequently methylated in primary breast tumours. These genes were identified by interrogating The Cancer Genome Atlas and a broad literature review. We analysed these genes for promoter methylation in metastatic brain tumours and their associated primary breast tumours. We carried out tumorigenicity assays to investigate the role of these genes in invasion and metastasis. RESULTS: We identified five genes (BNC1, CCDC8, L3MBTL1, GALNT9 and mir127), which are infrequently methylated in primary breast tumours and frequently methylated in brain metastases. In vitro migration and invasion assays indicate that these genes contribute to the metastatic potential of breast cancer cell lines. CONCLUSION: We have identified a number of genes that may contribute to breast to brain metastasis. Two of which (BNC1, GALNT9) are methylated and silenced specifically in the brain metastasis, indicating an event that has occurred after the tumour has disseminated. Another three genes (CCDC8, L3MBTL1 and mir127) are methylated in primary tumours that metastasised to the brain indicating a potential early role in metastasis. These findings may help develop prognostic and therapeutic tools.
PMCID: PMC4200957
3.  The GALNT9, BNC1 and CCDC8 genes are frequently epigenetically dysregulated in breast tumours that metastasise to the brain 
Clinical Epigenetics  2015;7(1):57.
Tumour metastasis to the brain is a common and deadly development in certain cancers; 18–30 % of breast tumours metastasise to the brain. The contribution that gene silencing through epigenetic mechanisms plays in these metastatic tumours is not well understood.
We have carried out a bioinformatic screen of genome-wide breast tumour methylation data available at The Cancer Genome Atlas (TCGA) and a broad literature review to identify candidate genes that may contribute to breast to brain metastasis (BBM). This analysis identified 82 candidates. We investigated the methylation status of these genes using Combined Bisulfite and Restriction Analysis (CoBRA) and identified 21 genes frequently methylated in BBM. We have identified three genes, GALNT9, CCDC8 and BNC1, that were frequently methylated (55, 73 and 71 %, respectively) and silenced in BBM and infrequently methylated in primary breast tumours. CCDC8 was commonly methylated in brain metastases and their associated primary tumours whereas GALNT9 and BNC1 were methylated and silenced only in brain metastases, but not in the associated primary breast tumours from individual patients. This suggests differing roles for these genes in the evolution of metastatic tumours; CCDC8 methylation occurs at an early stage of metastatic evolution whereas methylation of GANLT9 and BNC1 occurs at a later stage of tumour evolution. Knockdown of these genes by RNAi resulted in a significant increase in the migratory and invasive potential of breast cancer cell lines.
These findings indicate that GALNT9 (an initiator of O-glycosylation), CCDC8 (a regulator of microtubule dynamics) and BNC1 (a transcription factor with a broad range of targets) may play a role in the progression of primary breast tumours to brain metastases. These genes may be useful as prognostic markers and their products may provide novel therapeutic targets.
Electronic supplementary material
The online version of this article (doi:10.1186/s13148-015-0089-x) contains supplementary material, which is available to authorized users.
PMCID: PMC4457099  PMID: 26052355
Breast; Brain; Metastasis; DNA methylation; Epigenetic; Tumour suppressor
4.  Protein Binding of Rifapentine and Its 25-Desacetyl Metabolite in Patients with Pulmonary Tuberculosis 
Rifapentine is highly protein bound in blood, but the free, unbound drug is the microbiologically active fraction. In this exploratory study, we characterized the free plasma fraction of rifapentine in 41 patients with tuberculosis. We found a lower total rifapentine concentration but significantly higher free rifapentine levels in African patients of black race compared to non-Africans. These data support larger pharmacokinetic/pharmacodynamic studies to confirm these findings and assess free rifapentine in relation to microbiological and clinical outcomes.
PMCID: PMC4136068  PMID: 24841270
5.  Structure-Function Studies of the bHLH Phosphorylation Domain of TWIST1 in Prostate Cancer Cells12 
Neoplasia (New York, N.Y.)  2015;17(1):16-31.
The TWIST1 gene has diverse roles in development and pathologic diseases such as cancer. TWIST1 is a dimeric basic helix-loop-helix (bHLH) transcription factor existing as TWIST1-TWIST1 or TWIST1-E12/47. TWIST1 partner choice and DNA binding can be influenced during development by phosphorylation of Thr125 and Ser127 of the Thr-Gln-Ser (TQS) motif within the bHLH of TWIST1. The significance of these TWIST1 phosphorylation sites for metastasis is unknown. We created stable isogenic prostate cancer cell lines overexpressing TWIST1 wild-type, phospho-mutants, and tethered versions. We assessed these isogenic lines using assays that mimic stages of cancer metastasis. In vitro assays suggested the phospho-mimetic Twist1-DQD mutation could confer cellular properties associated with pro-metastatic behavior. The hypo-phosphorylation mimic Twist1-AQA mutation displayed reduced pro-metastatic activity compared to wild-type TWIST1 in vitro, suggesting that phosphorylation of the TWIST1 TQS motif was necessary for pro-metastatic functions. In vivo analysis demonstrates that the Twist1-AQA mutation exhibits reduced capacity to contribute to metastasis, whereas the expression of the Twist1-DQD mutation exhibits proficient metastatic potential. Tethered TWIST1-E12 heterodimers phenocopied the Twist1-DQD mutation for many in vitro assays, suggesting that TWIST1 phosphorylation may result in heterodimerization in prostate cancer cells. Lastly, the dual phosphatidylinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) inhibitor BEZ235 strongly attenuated TWIST1-induced migration that was dependent on the TQS motif. TWIST1 TQS phosphorylation state determines the intensity of TWIST1-induced pro-metastatic ability in prostate cancer cells, which may be partly explained mechanistically by TWIST1 dimeric partner choice.
PMCID: PMC4309734  PMID: 25622896
EMT, epithelial-mesenchymal transition; bHLH, basic helix-loop-helix; T-T, TWIST1-TWIST1; E12/E47, E2A proteins; T-E, TWIST1-E12; IHC, immunohistochemistry; PI, propidium iodide; PKA, protein kinase A
6.  Synthesis of structurally diverse benzosuberene analogues and their biological evaluation as anti-cancer agents 
Bioorganic & medicinal chemistry  2013;21(24):8019-8032.
Diversely functionalized, fused aryl-alkyl ring systems hold a prominent position as well-established molecular frameworks for a variety of anti-cancer agents. The benzosuberene (6,7 fused, also referred to as dihydro-5H-benzo[7]annulene and benzocycloheptene) ring system has emerged as a valuable molecular core component for the development of inhibitors of tubulin assembly, which function as antiproliferative anti-cancer agents and, in certain cases, as vascular disrupting agents (VDAs). Both a phenolic-based analogue (known as KGP18, compound 39) and its corresponding amine-based congener (referred to as KGP156, compound 45), which demonstrate strong inhibition of tubulin assembly (low micromolar range) and potent cytotoxicity (picomolar range for KGP18 and nanomolar range for KGP156) are noteworthy examples of such benzosuberene-based compounds. In order to extend the structure-activity relationship (SAR) knowledge base related to benzosuberene anti-cancer agents, a series of eleven analogues (including KGP18) were prepared in which the methoxylation pattern on the pendant aryl ring as well as functional group incorporation on the fused aryl ring were varied. The synthetic approach to these compounds featured a sequential Wittig olefination, reduction, Eaton's reagent-mediated cyclization strategy to achieve the core benzosuberone intermediate, and represented a higher-yielding synthesis of KGP18 (which we prepared previously through a ring-expansion strategy). Incorporation of a fluorine or chlorine atom at the 1-position of the fused aryl ring or replacement of one of the methoxy groups with hydrogen (on the pendant aryl ring of KGP18) led to benzosuberene analogues that were both strongly inhibitory against tubulin assembly (IC50 approximately 1.0 M) and strongly cytotoxic against selected human cancer cell lines (for example, GI50 = 5.47 nM against NCI-H460 cells with fluorobenzosuberene analogue 37). A water-soluble phosphate prodrug salt of KGP18 (referred to as KGP265, compound 44) and a water-soluble serinamide salt (compound 48) of KGP156 were also synthesized and evaluated in this study.
PMCID: PMC3968794  PMID: 24183586
inhibitors of tubulin assembly; benzosuberene-based anti-cancer agents; vascular disrupting agents (VDAs); combretastatin analogues
7.  Metabolic activation of CaMKII by Coenzyme A 
Molecular cell  2013;52(3):325-339.
Active metabolism regulates oocyte cell death via calcium/calmodulin-dependent protein kinase II (CaMKII) mediated phosphorylation of caspase-2, but the link between metabolic activity and CaMKII is poorly understood. Here we identify coenzyme A (CoA) as the key metabolic signal that inhibits Xenopus laevis oocyte apoptosis, in a novel mechanism of CaMKII activation. We found that CoA directly binds to the CaMKII regulatory domain in the absence of Ca2+ to activate CaMKII in a calmodulin-dependent manner. Furthermore, we show that CoA inhibits apoptosis not only in X. laevis oocytes, but also in Murine oocytes. These findings uncover a novel mechanism of CaMKII regulation by metabolism and further highlight the importance of metabolism in preserving oocyte viability.
PMCID: PMC3967247  PMID: 24095281
8.  The Twist Box Domain is Required for Twist1-induced Prostate Cancer Metastasis 
Molecular cancer research : MCR  2013;11(11):10.1158/1541-7786.MCR-13-0218-T.
Twist1, a basic helix-loop-helix transcription factor, plays a key role during development and is a master regulator of the epithelial-mesenchymal transition (EMT) that promotes cancer metastasis. Structure-function relationships of Twist1 to cancer-related phenotypes are underappreciated, so we studied the requirement of the conserved Twist box domain for metastatic phenotypes in prostate cancer (PCa). Evidence suggests that Twist1 is overexpressed in clinical specimens and correlated with aggressive/metastatic disease. Therefore, we examined a transactivation mutant, Twist1-F191G, in PCa cells using in vitro assays which mimic various stages of metastasis. Twist1 overexpression led to elevated cytoskeletal stiffness and cell traction forces at the migratory edge of cells based on biophysical single-cell measurements. Twist1 conferred additional cellular properties associated with cancer cell metastasis including increased migration, invasion, anoikis resistance, and anchorage-independent growth. The Twist box mutant was defective for these Twist1 phenotypes in vitro. Importantly, we observed a high frequency of Twist1-induced metastatic lung tumors and extra-thoracic metastases in vivo using the experimental lung metastasis assay. The Twist box was required for PCa cells to colonize metastatic lung lesions and extra-thoracic metastases. Comparative genomic profiling revealed transcriptional programs directed by the Twist box that were associated with cancer progression, such as Hoxa9. Mechanistically, Twist1 bound to the Hoxa9 promoter and positively regulated Hoxa9 expression in PCa cells. Finally, Hoxa9 was important for Twist1-induced cellular phenotypes associated with metastasis. These data suggest that the Twist box domain is required for Twist1 transcriptional programs and PCa metastasis.
PMCID: PMC3833995  PMID: 23982216
Twist1; Twist box; epithelial-mesenchymal transition; prostate cancer; metastasis; Hoxa9
9.  Neutrophil Mobilization by Surface-Glycan Altered Th17-Skewing Bacteria Mitigates Periodontal Pathogen Persistence and Associated Alveolar Bone Loss 
PLoS ONE  2014;9(9):e108030.
Alveolar bone (tooth-supporting bone) erosion is a hallmark of periodontitis, an inflammatory disease that often leads to tooth loss. Periodontitis is caused by a select group of pathogens that form biofilms in subgingival crevices between the gums and teeth. It is well-recognized that the periodontal pathogen Porphyromonas gingivalis in these biofilms is responsible for modeling a microbial dysbiotic state, which then initiates an inflammatory response destructive to the periodontal tissues and bone. Eradication of this pathogen is thus critical for the treatment of periodontitis. Previous studies have shown that oral inoculation in mice with an attenuated strain of the periodontal pathogen Tannerella forsythia altered in O-glycan surface composition induces a Th17-linked mobilization of neutrophils to the gingival tissues. In this study, we sought to determine if immune priming with such a Th17-biasing strain would elicit a productive neutrophil response against P. gingivalis. Our data show that inoculation with a Th17-biasing T. forsythia strain is effective in blocking P. gingivalis-persistence and associated alveolar bone loss in mice. This work demonstrates the potential of O-glycan modified Tannerella strains or their O-glycan components for harnessing Th17-mediated immunity against periodontal and other mucosal pathogens.
PMCID: PMC4167248  PMID: 25225799
10.  Immunoglobulin Concentration in Tears of Contact Lens Wearers 
To evaluate changes in the concentration of tear immunoglobulins in contact lens wearers.
A total of 45 cases including 23 contact lens wearers (43 eyes) and 22 age and sex matched healthy controls having no ocular pathology were studied for immunoglobulins (IgA, IgG, IgM) in their tears by single radial immunodiffusion method.
Most of the cases used soft (56.6%) and semi-soft gas permeable (30.4%) contact lenses. Tear IgM was detected in only 17.4% and tear IgG in 43.6% of contact lens wearers, while in controls IgG was detected in 9.1% but none of the controls had IgM. There was a significant rise in total tear IgA (13.17 ± 4.44 mg/dl) in contact lens wearer as compared to controls (8.93 ± 3.79 mg/dl). Rise of tear IgA was more in symptomatic patients (15.38 ± 5.28 mg/dl) and in those wearing hard (19.73 ± 5.43 mg/dl) and semi-soft contact lenses (13.31 ± 5.43 mg/dl). A significant increase in tear IgA was noticed in subjects wearing lenses for >3 years (15.69 ± 5.39 mg/dl). About 43.4% of lens wearers were symptomatic and 80% of their lenses showed deposits and/or haziness. All cases with IgM in tear were symptomatic.
The relation of immunoglobulin concentration with increasing duration of wear and material of contact lens shows that tear immunoglobulin rise accrues due to mechanical stimulation, hence contact lenses should not be used for a long period and lenses of hard nature should be discouraged. The maintenance, cleaning and deproteinization of the lenses are of high importance to avoid immunostimulation.
PMCID: PMC4307655  PMID: 25667732
Contact Lens; Radial Immunodiffusion Method; Tear Immunoglobulins
11.  A bacterial glycan core linked to surface (S)-layer proteins modulates host immunity through Th17 suppression 
Mucosal immunology  2012;6(2):415-426.
Tannerella forsythia is a pathogen implicated in periodontitis, an inflammatory disease of the tooth supporting tissues often leading to tooth loss. This key periodontal pathogen is decorated with a unique glycan core O-glycosidically linked to the bacterium’s proteinacious surface(S)-layer lattice and other glycoproteins. Herein we show that the terminal motif of this glycan core acts to modulate dendritic cell effector functions to suppress Th17 responses. In contrast to the wild-type bacterial strain, infection with a mutant strain lacking the complete S-layer glycan core induced robust Th17 and reduced periodontal bone loss in mice. Our findings demonstrate that surface glycosylation of this pathogen acts to ensure its persistence in the host by suppressing Th17 responses. In addition our data suggest that the bacterium then induces the TLR2-Th2 inflammatory axis that has previously shown to cause bone destruction. Our study provides a biological basis for pathogenesis and opens opportunities in exploiting bacterial glycans as therapeutic targets against periodontitis and a range of other infectious diseases.
PMCID: PMC4049606  PMID: 22968422
12.  Effect of soaking and cooking on dietary fibre components of different type of chickpea genotypes 
Processing is an important and essential component to enhance the digestibility of essential nutrients of grains. Dietary fibres play an important role in bringing health advantages in chickpea and help in lowering plasma cholesterol. Changes during soaking and soaking followed by cooking on cellulose, hemicellulose, lignin and pectin contents of four genotypes of desi type (KWR 108, JG 74, DCP 92-3 and BG 256), four genotypes of kabuli types (KAK 2, JKG 1, BG 1053, and L 550) and two genotypes of green seed type (BGD 112 and Sadabahar) of chickpeas (Cicer arietinum, L.) was studied. Cellulose, lignin and pectin increased during soaking and cooking, whereas hemicellulose increased during soaking but decreased drastically during cooking. Cellulose recorded an overall increase of 40% during cooking, followed by 15.7% and 15.2% increase in pectin and lignin, respectively during cooking of chickpea grain. Hemicellulose, on the contrary showed a decrease of 26.8% during cooking.
PMCID: PMC3602558  PMID: 24425956
Chickpea; Cooking; Cellulose; Hemicellulose; Lignin; Pectin
13.  Cost-Effectiveness of a Tuberculosis Active Case Finding Program Targeting Household and Neighborhood Contacts in Cambodia 
In many high-risk populations, access to tuberculosis (TB) diagnosis and treatment is limited and pockets of high prevalence persist. We estimated the cost-effectiveness of an extensive active case finding program in areas of Cambodia where TB notifications and household poverty rates are highest and access to care is restricted. Thirty operational health districts with high TB incidence and household poverty were randomized into intervention and control groups. In intervention operational health districts, all household and symptomatic neighborhood contacts of registered TB patients of the past two years were encouraged to attend screening at mobile centers. In control districts, routine passive case finding activities continued. The program screened more than 35,000 household and neighborhood contacts and identified 810 bacteriologically confirmed cases. The cost-effectiveness analysis estimated that in these cases the reduction in mortality from 14% to 2% would result in a cost per daily adjusted life year averted of $330, suggesting that active case finding was highly cost-effective.
PMCID: PMC4015580  PMID: 24615134
14.  Inhibition of TWIST1 Leads to Activation of Oncogene-Induced Senescence in Oncogene Driven Non-Small Cell Lung Cancer 
Molecular cancer research : MCR  2013;11(4):329-338.
A large fraction of non-small cell lung cancers (NSCLC) are dependent on defined oncogenic driver mutations. Although targeted agents exist for EGFR- and EML4-ALK-driven NSCLC, no therapies target the most frequently found driver mutation, KRAS. Furthermore, acquired resistance to the currently targetable driver mutations is nearly universally observed. Clearly a novel therapeutic approach is needed to target oncogene driven NSCLC. We recently demonstrated that the basic helix-loop-helix transcription factor Twist1 cooperates with mutant Kras to induce lung adenocarcinoma in transgenic mouse models and that inhibition of Twist1 in these models led to Kras-induced senescence. In the current study, we examine the role of TWIST1 in oncogene driven human NSCLC. Silencing of TWIST1 in KRAS mutant human NSCLC cell lines resulted in dramatic growth inhibition and either activation of a latent oncogene-induced senescence program or in some cases, apoptosis. Similar effects were observed in EGFR mutation driven and c-Met amplified NSCLC cell lines. Growth inhibition by silencing of TWIST1 was independent of p53 or p16 mutational status and did not require previously defined mediators of senescence, p21 and p27, nor could this phenotype be rescued by overexpression of SKP2. In xenograft models, silencing of TWIST1 resulted in significant growth inhibition of KRAS mutant, EGFR mutant and c-Met amplified NSCLC. Remarkably, inducible silencing of TWIST1 resulted in significant growth inhibition of established KRAS mutant tumors. Together these findings suggest that silencing of TWIST1 in oncogene driver dependent NSCLC represents a novel and promising therapeutic strategy.
PMCID: PMC3631276  PMID: 23364532
15.  Novel Hsp90 inhibitor NVP-AUY922 radiosensitizes prostate cancer cells 
Cancer Biology & Therapy  2013;14(4):347-356.
Outcomes for poor-risk localized prostate cancers treated with radiation are still insufficient. Targeting the “non-oncogene” addiction or stress response machinery is an appealing strategy for cancer therapeutics. Heat-shock-protein-90 (Hsp90), an integral member of this machinery, is a molecular chaperone required for energy-driven stabilization and selective degradation of misfolded “client” proteins, that is commonly overexpressed in tumor cells. Hsp90 client proteins include critical components of pathways implicated in prostate cancer cell survival and radioresistance, such as androgen receptor signaling and the PI3K-Akt-mTOR pathway. We examined the effects of a novel non-geldanamycin Hsp90 inhibitor, AUY922, combined with radiation (RT) on two prostate cancer cell lines, Myc-CaP and PC3, using in vitro assays for clonogenic survival, apoptosis, cell cycle distribution, γ-H2AX foci kinetics and client protein expression in pathways important for prostate cancer survival and radioresistance. We then evaluated tumor growth delay and effects of the combined treatment (RT-AUY922) on the PI3K-Akt-mTOR and AR pathways in a hind-flank tumor graft model. We observed that AUY922 caused supra-additive radiosensitization in both cell lines at low nanomolar doses with enhancement ratios between 1.4–1.7 (p < 0.01). RT-AUY922 increased apoptotic cell death compared with either therapy alone, induced G2-M arrest and produced marked changes in client protein expression. These results were confirmed in vivo, where RT-AUY922 combination therapy produced supra-additive tumor growth delay compared with either therapy by itself in Myc-CaP and PC3 tumor grafts (both p < 0.0001). Our data suggest that combined RT-AUY922 therapy exhibits promising activity against prostate cancer cells, which should be investigated in clinical studies.
PMCID: PMC3667875  PMID: 23358469
prostate cancer; Hsp90; NVP-AUY922; radiosensitizer; DNA damage response
16.  Protein-linked glycans in periodontal bacteria: prevalence and role at the immune interface 
Protein modification with complex glycans is increasingly being recognized in many pathogenic and non-pathogenic bacteria, and is now thought to be central to the successful life-style of those species in their respective hosts. This review aims to convey current knowledge on the extent of protein glycosylation in periodontal pathogenic bacteria and its role in the modulation of the host immune responses. The available data show that surface glycans of periodontal bacteria orchestrate dendritic cell cytokine responses to drive T cell immunity in ways that facilitate bacterial persistence in the host and induce periodontal inflammation. In addition, surface glycans may help certain periodontal bacteria protect against serum complement attack or help them escape immune detection through glycomimicry. In this review we will focus mainly on the generalized surface-layer protein glycosylation system of the periodontal pathogen Tannerella forsythia in shaping innate and adaptive host immunity in the context of periodontal disease. In addition, we will also review the current state of knowledge of surface protein glycosylation and its potential for immune modulation in other periodontal pathogens.
PMCID: PMC3797959  PMID: 24146665
protein glycosylation; periodontal bacteria; immune response
17.  Crystallization and preliminary X-ray diffraction studies of sortase A from Streptococcus pneumoniae  
Sortase A from S. pneumoniae has been crystallized in two crystal forms: diamond-shaped (construct ΔN59SrtA) and rod-shaped (construct ΔN81SrtA). The diamond-shaped crystals diffracted poorly to 4.0 Å resolution and belonged to a tetragonal system, whereas the rod-shaped crystals diffracted to 2.91 Å resolution and belonged to space group P21.
Sortases are cell-membrane-anchored cysteine transpeptidases that are essential for the assembly and anchoring of cell-surface adhesins in Gram-positive bacteria. Thus, they play critical roles in virulence, infection and colonization by pathogens. Sortases have been classified into four types based on their primary sequence and the target-protein motifs that they recognize. All Gram-positive bacteria express a class A housekeeping sortase (SrtA). Sortase A from Streptococcus pneumoniae (NP_358691) has been crystallized in two crystal forms. Diamond-shaped crystals of ΔN59SrtA diffracted to 4.0 Å resolution and belonged to a tetragonal system with unit-cell parameters a = b = 122.8, c = 86.5 Å, α = β = γ = 90°, while rod-shaped crystals of ΔN81SrtA diffracted to 2.91 Å resolution and belonged to the monoclinic space group P21 with unit-cell parameters a = 66.8, b = 103.47, c = 74.79 Å, α = γ = 90, β = 115.65°. The Matthews coefficient (V M = 2.77 Å3 Da−1) with ∼56% solvent content suggested the presence of four molecules in the asymmetric unit for ΔN81SrtA. Also, a multi-copy search using a monomer as a probe in the molecular-replacement method resulted in the successful location of four sortase molecules in the asymmetric unit, with statistics R = 41.61, R free = 46.44, correlation coefficient (CC) = 64.31, CCfree = 57.67.
PMCID: PMC3212360  PMID: 22102025
sortases; cysteine transpeptidases; Streptococcus pneumoniae
18.  Identification of a unique TLR2-interacting peptide motif in a microbial leucine-rich-repeat protein 
Pathogenesis of many bacterially-induced inflammatory diseases is driven by toll- like receptor (TLR) mediated immune responses following recognition of bacterial factors by different TLRs. Periodontitis is a chronic inflammation of the tooth supporting apparatus often leading to tooth loss, and is caused by a Gram-negative bacterial consortium that includes Tannerella forsythia. This bacterium expresses a virulence factor, the BspA, which drives periodontal inflammation by activating TLR2. The N- terminal portion of the BspA protein comprises a leucine-rich repeat (LRR) domain previously shown to be involved in the binding and activation of TLR2. The objective of the current study was to identify specific epitopes in the LRR domain of BspA that interact with TLR2. Our results demonstrate that a sequence motif GC(S/T)GLXSIT is involved in mediating the interaction of BspA with TLR2. Thus, our study has identified a peptide motif that mediates the binding of a bacterial protein to TLR2 and highlights the promiscuous nature of TLR2 with respect to ligand binding. This work could provide a structural basis for designing peptidomimetics to modulate the activity of TLR2 in order to block bacterially-induced inflammation.
PMCID: PMC3405494  PMID: 22695115
leucine-rich repeat protein; BspA; TLR-2; Tannerella forsythia
19.  An Amino-Benzosuberene Analogue That Inhibits Tubulin Assembly and Demonstrates Remarkable Cytotoxicity 
MedChemComm  2012;3(6):720-724.
The recent discovery of a small-molecule benzosuberene-based phenol that demonstrates remarkable picomolar cytotoxicity against selected human cancer cell lines and strongly inhibits tubulin polymerization (1–2 µM) inspired the design and synthesis of a variety of new, structurally diverse benzosuberene derivatives. An efficient synthetic route to functionalized benzosuberenes was developed. This methodology utilized a Wittig reaction, followed by a selective alkene reduction and ring-closing cyclization to form the core benzosuberone structure. This synthetic route facilitated the preparation of a 6-nitro-1-(3′,4′,5′-trimethoxyphenyl) benzosuberene derivative and its corresponding 6-amino analogue in good yield. The 6-amino analogue was a strong inhibitor of tubulin polymerization (1.2 µM), demonstrated enhanced cytotoxicity against the human cancer cell lines examined (GI50 = 33 pM against SK-OV-3 ovarian cancer, for example), and exhibited a concentration dependent disruption of a pre-established capillary-like network of tubules formed from human umbilical vein endothelial cells.
PMCID: PMC3682772  PMID: 23772309
20.  Concurrent versus Sequential Sorafenib Therapy in Combination with Radiation for Hepatocellular Carcinoma 
PLoS ONE  2013;8(6):e65726.
Sorafenib (SOR) is the only systemic agent known to improve survival for hepatocellular carcinoma (HCC). However, SOR prolongs survival by less than 3 months and does not alter symptomatic progression. To improve outcomes, several phase I-II trials are currently examining SOR with radiation (RT) for HCC utilizing heterogeneous concurrent and sequential treatment regimens. Our study provides preclinical data characterizing the effects of concurrent versus sequential RT-SOR on HCC cells both in vitro and in vivo. Concurrent and sequential RT-SOR regimens were tested for efficacy among 4 HCC cell lines in vitro by assessment of clonogenic survival, apoptosis, cell cycle distribution, and γ-H2AX foci formation. Results were confirmed in vivo by evaluating tumor growth delay and performing immunofluorescence staining in a hind-flank xenograft model. In vitro, concurrent RT-SOR produced radioprotection in 3 of 4 cell lines, whereas sequential RT-SOR produced decreased colony formation among all 4. Sequential RT-SOR increased apoptosis compared to RT alone, while concurrent RT-SOR did not. Sorafenib induced reassortment into less radiosensitive phases of the cell cycle through G1-S delay and cell cycle slowing. More double-strand breaks (DSBs) persisted 24 h post-irradiation for RT alone versus concurrent RT-SOR. In vivo, sequential RT-SOR produced the greatest tumor growth delay, while concurrent RT-SOR was similar to RT alone. More persistent DSBs were observed in xenografts treated with sequential RT-SOR or RT alone versus concurrent RT-SOR. Sequential RT-SOR additionally produced a greater reduction in xenograft tumor vascularity and mitotic index than either concurrent RT-SOR or RT alone. In conclusion, sequential RT-SOR demonstrates greater efficacy against HCC than concurrent RT-SOR both in vitro and in vivo. These results may have implications for clinical decision-making and prospective trial design.
PMCID: PMC3675179  PMID: 23762417
21.  High Throughput Transcriptome Profiling of Lithium Stimulated Human Mesenchymal Stem Cells Reveals Priming towards Osteoblastic Lineage 
PLoS ONE  2013;8(1):e55769.
Human mesenchymal stem cells (hMSCs) present in the bone marrow are the precursors of osteoblasts, chondrocytes and adipocytes, and hold tremendous potential for osteoregenerative therapy. However, achieving directed differentiation into osteoblasts has been a major concern. The use of lithium for enhancing osteogenic differentiation has been documented in animal models but its effect in humans is not clear. We, therefore, performed high throughput transcriptome analysis of lithium-treated hMSCs to identify altered gene expression and its relevance to osteogenic differentiation. Our results show suppression of proliferation and enhancement of alkaline phosphatase (ALP) activity upon lithium treatment of hMSCs under non-osteogenic conditions. Microarray profiling of lithium-stimulated hMSC revealed decreased expression of adipogenic genes (CEBPA, CMKLR1, HSD11B1) and genes involved in lipid biosynthesis. Interestingly, osteoclastogenic factors and immune responsive genes (IL7, IL8, CXCL1, CXCL12, CCL20) were also downregulated. Negative transcriptional regulators of the osteogenic program (TWIST1 and PBX1) were suppressed while genes involved in mineralization like CLEC3B and ATF4 were induced. Gene ontology analysis revealed enrichment of upregulated genes related to mesenchymal cell differentiation and signal transduction. Lithium priming led to enhanced collagen 1 synthesis and osteogenic induction of lithium pretreated MSCs resulted in enhanced expression of Runx2, ALP and bone sialoprotein. However, siRNA-mediated knockdown of RRAD, CLEC3B and ATF4 attenuated lithium-induced osteogenic priming, identifying a role for RRAD, a member of small GTP binding protein family, in osteoblast differentiation. In conclusion, our data highlight the transcriptome reprogramming potential of lithium resulting in higher propensity of lithium “primed” MSCs for osteoblastic differentiation.
PMCID: PMC3559497  PMID: 23383279
22.  MORC2 Signaling Facilitates Phosphorylation-dependent, ATPase-coupled Chromatin Remodeling during the DNA Damage Response 
Cell reports  2012;2(6):1657-1669.
Chromatin dynamics play a central role in maintaining genome integrity, but how this is achieved remains largely unknown. Here, we report that microrchidia CW-type zinc finger 2 (MORC2), an uncharacterized protein with a derived PHD finger domain and a conserved GHKL-type ATPase module, is a physiological substrate of p21-activated kinase 1 (PAK1), an important integrator of extracellular signals and nuclear processes. Following DNA damage, MORC2 is phosphorylated on serine 739 in a PAK1 dependent manner, and phosphorylated MORC2 regulates its DNA-dependent ATPase activity to facilitate chromatin remodeling. Moreover, MORC2 associates with chromatin and promotes gamma-H2AX induction in a PAK1 phosphorylation-dependent manner. Consequently, cells expressing MORC2-S739A mutation displayed a reduction in DNA repair efficiency and were hypersensitive to DNA-damaging agent. These findings suggest that the PAK1-MORC2 axis is critical for orchestrating the interplay between chromatin dynamics and the maintenance of genomic integrity through sequentially integrating multiple essential enzymatic processes.
PMCID: PMC3554793  PMID: 23260667
Chromatin remodeling; DNA damage response; Genomic stability; Modifier of radiosensitivity; MORC2
23.  Fusobacterium nucleatum and Tannerella forsythia Induce Synergistic Alveolar Bone Loss in a Mouse Periodontitis Model 
Infection and Immunity  2012;80(7):2436-2443.
Tannerella forsythia is strongly associated with chronic periodontitis, an inflammatory disease of the tooth-supporting tissues, leading to tooth loss. Fusobacterium nucleatum, an opportunistic pathogen, is thought to promote dental plaque formation by serving as a bridge bacterium between early- and late-colonizing species of the oral cavity. Previous studies have shown that F. nucleatum species synergize with T. forsythia during biofilm formation and pathogenesis. In the present study, we showed that coinfection of F. nucleatum and T. forsythia is more potent than infection with either species alone in inducing NF-κB activity and proinflammatory cytokine secretion in monocytic cells and primary murine macrophages. Moreover, in a murine model of periodontitis, mixed infection with the two species induces synergistic alveolar bone loss, characterized by bone loss which is greater than the additive alveolar bone losses induced by each species alone. Further, in comparison to the single-species infection, mixed infection caused significantly increased inflammatory cell infiltration in the gingivae and osteoclastic activity in the jaw bones. These data show that F. nucleatum subspecies and T. forsythia synergistically stimulate the host immune response and induce alveolar bone loss in a murine experimental periodontitis model.
PMCID: PMC3416462  PMID: 22547549
25.  Regioselective Synthesis of Water Soluble Monophosphate Derivatives of Combretastatin A-1 
Journal of Natural Products  2011;74(7):1568-1574.
The natural products combretastatin A-4 (CA4) and combretastatin A-1 (CA1) are potent cancer vascular disrupting agents (VDAs) and inhibitors of tubulin assembly (IC50 = 1–2 μM). The phosphorylated prodrugs CA4P and CA1P are undergoing human clinical trials against cancer. CA1 is unique due to its incorporation of a vicinal phenol, which has afforded the opportunity to prepare both diphosphate and regioisomeric monophosphate derivatives. Here, we describe the first synthetic routes suitable for the regiospecific preparation of the CA1-monophosphates, CA1MPA (8a/b) and CA1MPB (4a/b). The essential regiochemistry necessary to distinguish between the two vicinal phenolic groups was accomplished with a tosyl protecting group strategy. Each of the four monophosphate analogues (including Z and E isomers) demonstrated in vitro cytotoxicity against selected human cancer cell lines comparable to their corresponding diphosphate congeners. Furthermore, Z-CA1MPA (8a) and Z-CA1MPB (4a) were inactive as inhibitors of tubulin assembly (IC50 > 40 μM), as anticipated in this pure protein assay.
PMCID: PMC3275140  PMID: 21718055

Results 1-25 (43)