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1.  Small-molecule pyrimidine inhibitors of the cdc2-like (Clk) and dual specificity tyrosine phosphorylation-regulated (Dyrk) kinases: Development of chemical probe ML315 
Substituted pyrimidine inhibitors of the Clk and Dyrk kinases have been developed, exploring structure-activity relationships around four different chemotypes. The most potent compounds have low-nanomolar inhibitory activity against Clk1, Clk2, Clk4, Dyrk1A and Dyrk1B. Kinome scans with 442 kinases using agents representing three of the chemotypes show these inhibitors to be highly selective for the Clk and Dyrk families. Further off-target pharmacological evaluation with ML315, the most selective agent, supports this conclusion.
PMCID: PMC3664191  PMID: 23642479
Clk; Dyrk; Kinase inhibitor; Splicing; Pyrimidine
2.  The Interplay of AMP-activated Protein Kinase and Androgen Receptor in Prostate Cancer Cells† 
Journal of cellular physiology  2014;229(6):688-695.
AMP-activated protein kinase (AMPK) has recently emerged as a potential target for cancer therapy due to the observation that activation of AMPK inhibits tumor cell growth. It is well-known that androgen receptor (AR) signaling is a major driver for the development and progression of prostate cancer and that downregulation of AR is a critical step in the induction of apoptosis in prostate cancer cells. However, little is known about the potential interaction between AMPK and AR signaling pathways. In the current study, we showed that activation of AMPK by metformin caused decrease of AR protein level through suppression of AR mRNA expression and promotion of AR protein degradation, demonstrating that AMPK activation is upstream of AR downregulation. We also showed that inhibition of AR function by an anti-androgen or its siRNA enhanced AMPK activation and growth inhibition whereas overexpression of AR delayed AMPK activation and increased prostate cancer cellular resistance to metformin treatment, suggesting that AR suppresses AMPK signaling-mediated growth inhibition in a feedback mechanism. Our findings thus reveal a novel AMPK-AR regulatory loop in prostate cancer cells and should have a potential clinical significance.
PMCID: PMC3947449  PMID: 24129850
AMP-activated protein kinase; Androgen receptor; Prostate cancer; Metformin; Apoptosis
3.  High-Throughput Screening for the Identification of New Therapeutic Options for Metastatic Pheochromocytoma and Paraganglioma 
PLoS ONE  2014;9(4):e90458.
Drug repurposing or repositioning is an important part of drug discovery that has been growing in the last few years for the development of therapeutic options in oncology. We applied this paradigm in a screening of a library of about 3,800 compounds (including FDA-approved drugs and pharmacologically active compounds) employing a model of metastatic pheochromocytoma, the most common tumor of the adrenal medulla in children and adults. The collection of approved drugs was screened in quantitative mode, testing the compounds in compound-titration series (dose-response curves). Analysis of the dose-response screening data facilitated the selection of 50 molecules with potential bioactivity in pheochromocytoma cells. These drugs were classified based on molecular/cellular targets and signaling pathways affected, and selected drugs were further validated in a proliferation assay and by flow cytometric cell death analysis. Using meta-analysis information from molecular targets of the top drugs identified by our screening with gene expression data from human and murine microarrays, we identified potential drugs to be used as single drugs or in combination. An example of a combination with a synergistic effect is presented. Our study exemplifies a promising model to identify potential drugs from a group of clinically approved compounds that can more rapidly be implemented into clinical trials in patients with metastatic pheochromocytoma or paraganglioma.
PMCID: PMC3974653  PMID: 24699253
4.  Alterations in serum immunoglobulin levels in workers occupationally exposed to trichloroethylene 
Carcinogenesis  2012;34(4):799-802.
Trichloroethylene (TCE) has been associated with a variety of immunotoxic effects and may be associated with an increased risk of non-Hodgkin lymphoma (NHL). Altered serum immunoglobulin (Ig) levels have been reported in NHL patients and in animals exposed to TCE. Recently, we reported that occupational exposure to TCE is associated with immunosuppressive effects and immune dysfunction, including suppression of B-cell counts and activation, even at relatively low levels. We hypothesized that TCE exposure would also affect Ig levels in humans. We measured serum levels of IgG, IgM and IgE, by enzyme-linked immunosorbent assay, in TCE-exposed workers (n = 80) and unexposed controls (n = 45), matched by age and gender, in a cross-sectional, molecular epidemiology study of occupational exposure to TCE in Guangdong, China. Exposed workers had about a 17.5% decline in serum levels of IgG compared with unexposed controls (P = 0.0002). Similarly, serum levels of IgM were reduced by about 38% in workers exposed to TCE compared with unexposed controls (P < 0.0001). Serum levels of both IgG and IgM were significantly decreased in workers exposed to TCE levels below 12 p.p.m., the median exposure level. Adjustment for B-cell counts had minimal impact on our findings. IgE levels were not significantly different between exposed and control subjects. These results provide further evidence that TCE is immunotoxic at relatively low exposure levels and provide additional biologic plausibility for the reported association of TCE with NHL.
PMCID: PMC3616671  PMID: 23276795
5.  A Panel of Diverse Assays to Interrogate the Interaction between Glucokinase and Glucokinase Regulatory Protein, Two Vital Proteins in Human Disease 
PLoS ONE  2014;9(2):e89335.
Recent genetic and clinical evidence has implicated glucokinase regulatory protein (GKRP) in the pathogenesis of type 2 diabetes and related traits. The primary role of GKRP is to bind and inhibit hepatic glucokinase (GCK), a critically important protein in human health and disease that exerts a significant degree of control over glucose metabolism. As activation of GCK has been associated with improved glucose tolerance, perturbation of the GCK-GKRP interaction represents a potential therapeutic target for pharmacological modulation. Recent structural and kinetic advances are beginning to provide insight into the interaction of these two proteins. However, tools to comprehensively assess the GCK-GKRP interaction, particularly in the context of small molecules, would be a valuable resource. We therefore developed three robust and miniaturized assays for assessing the interaction between recombinant human GCK and GKRP: an HTRF assay, a diaphorase-coupled assay, and a luciferase-coupled assay. The assays are complementary, featuring distinct mechanisms of detection (luminescence, fluorescence, FRET). Two assays rely on GCK enzyme activity modulation by GKRP while the FRET-based assay measures the GCK-GKRP protein-protein interaction independent of GCK enzymatic substrates and activity. All three assays are scalable to low volumes in 1536-well plate format, with robust Z’ factors (>0.7). Finally, as GKRP sequesters GCK in the hepatocyte nucleus at low glucose concentrations, we explored cellular models of GCK localization and translocation. Previous findings from freshly isolated rat hepatocytes were confirmed in cryopreserved rat hepatocytes, and we further extended this study to cryopreserved human hepatocytes. Consistent with previous reports, there were several key differences between the rat and human systems, with our results suggesting that human hepatocytes can be used to interrogate GCK translocation in response to small molecules. The assay panel developed here should help direct future investigation of the GCK-GKRP interaction in these or other physiologically relevant human systems.
PMCID: PMC3929664  PMID: 24586696
6.  Occupational exposure to formaldehyde and alterations in lymphocyte subsets 
Formaldehyde is used in many occupational settings, most notably in manufacturing, health care, and embalming. Formaldehyde has been classified as a human carcinogen, but its mechanism of action remains uncertain.
We carried out a cross-sectional study of 43 formaldehyde exposed-workers and 51 unexposed age and sex-matched controls in Guangdong, China to study formaldehyde’s early biologic effects. To follow-up our previous report that the total lymphocyte count was decreased in formaldehyde-exposed workers compared to controls, we evaluated each major lymphocyte subset (i.e., CD4+ T cells, CD8+ T cells, natural killer (NK) cells, and B cells) and T cell lymphocyte subset (CD4+ naïve and memory T cells, CD8+ naïve and memory T cells, and regulatory T cells). Linear regression of each subset was used to test for differences between exposed workers and controls, adjusting for potential confounders.
Total NK cell and T cell counts were about 24% (p=0.037) and 16% (p=0.0042) lower, respectively, among exposed workers. Among certain T cell subsets, decreased counts among exposed workers were observed for CD8+ T cells (p=0.026), CD8+ effector memory T cells (p=0.018), and regulatory T cells (CD4+FoxP3+: p=0.04; CD25+FoxP3+: p=0.008).
Formaldehyde exposed-workers experienced decreased counts of NK cells, regulatory T cells, and CD8+ effector memory T cells; however, due to the small sample size these findings need to be confirmed in larger studies.
PMCID: PMC3493854  PMID: 22767408
formaldehyde; NK cell; B cell; T cell; T cell subset
7.  Synthesis and biological evaluation of analogues of the kinase inhibitor nilotinib as Abl and Kit inhibitors 
The importance of the trifluoromethyl group in the polypharmacological profile of nilotinib was investigated. Molecular editing of nilotinib led to the design, synthesis and biological evaluation of analogues where the trifluoromethyl group was replaced by a proton, fluorine and a methyl group. While these analogues were less active than nilotinib toward Abl, their activity toward Kit was comparable, with the monofluorinated analogue being the most active. Docking of nilotinib and of analogues 2a–c to the binding pocket of Abl and of Kit showed that the lack of shape complementarity in Kit is compensated by the stabilizing effect from its juxtamembrane region.
PMCID: PMC3547291  PMID: 23273517
CML; Kit; Abl; kinase; molecular editing
8.  A complicated case of pachydermoperiostosis with spondyloarthritides: a case report 
Pachydermoperiostosis is a rare, hereditary disease commonly presenting with digital clubbing, pachydermia and periosteal hypertrophy. Therapeutic options for pachydermoperiostosis are few because of the unknown pathogenesis. Here, we report the complicated case of a patient with pachydermoperiostosis combined with spondyloarthritides, who was refractory to steroids and tumor necrosis factor alpha antagonists. We treated this patient with zoledronic acid and performed an arthroscopic synovectomy, with a satisfactory outcome. To the best of our knowledge, this is the first report in English on the combination of zoledronic acid administration and synovectomy for the treatment of a patient with pachydermoperiostosis and spondyloarthritides.
Case presentation
An 18-year-old Han Chinese man was diagnosed with pachydermoperiostosis in the presence of digital clubbing, periostitis and swollen limbs. Combined spondyloarthritides was also considered based on his lower back pain, lower limbs synovitis, bilateral sacroiliac sclerosis and a positive test for human leukocyte antigen B27, as well as immunoglobulin A nephropathy. He was refractory to steroids and tumor necrosis factor alpha antagonists, but treated with intravenous zoledronic acid and an arthroscopic synovectomy, with a satisfactory outcome.
This is a rare, complicated case of pachydermoperiostosis with spondyloarthritides. Combination therapy of zoledronic acid administration with synovectomy is a novel, convenient and effective option for patients with pachydermoperiostosis with remarkable synovitis.
PMCID: PMC3878661  PMID: 24330652
Bisphosphonate; Pachydermoperiostosis; Spondyloarthritides; Synovectomy; Zoledronic acid
9.  A “Stem Cells in Cancer” special issue in Translational Cancer Research 
PMCID: PMC3872554  PMID: 24385709
10.  Correction: Identification of Therapeutic Candidates for Chronic Lymphocytic Leukemia from a Library of Approved Drugs 
PLoS ONE  2013;8(11):10.1371/annotation/e2536fcb-3ab3-44a0-8eab-91aaeb8e49b6.
PMCID: PMC3815351
11.  An MRI-Visible Non-Viral Vector Bearing GD2 Single Chain Antibody for Targeted Gene Delivery to Human Bone Marrow Mesenchymal Stem Cells 
PLoS ONE  2013;8(10):e76612.
The neural ganglioside GD2 has recently been reported to be a novel surface marker that is only expressed on human bone marrow mesenchymal stem cells within normal marrow. In this study, an MRI-visible, targeted, non-viral vector for effective gene delivery to human bone marrow mesenchymal stem cells was first synthesized by attaching a targeting ligand, the GD2 single chain antibody (scAbGD2), to the distal ends of PEG-g-PEI-SPION. The targeted vector was then used to condense plasmid DNA to form nanoparticles showing stable small size, low cytotoxicity, and good biocompatibility. Based on a reporter gene assay, the transfection efficiency of targeting complex reached the highest value at 59.6% ± 4.5% in human bone marrow mesenchymal stem cells, which was higher than those obtained using nontargeting complex and lipofectamine/pDNA (17.7% ± 2.9% and 34.9% ± 3.6%, respectively) (P<0.01). Consequently, compared with the nontargeting group, more in vivo gene expression was observed in the fibrotic rat livers of the targeting group. Furthermore, the targeting capacity of scAbGD2-PEG-g-PEI-SPION was successfully verified in vitro by confocal laser scanning microscopy, Prussian blue staining, and magnetic resonance imaging. Our results indicate that scAbGD2-PEG-g-PEI-SPION is a promising MRI-visible non-viral vector for targeted gene delivery to human bone marrow mesenchymal stem cells.
PMCID: PMC3792021  PMID: 24116127
12.  Identification of Therapeutic Candidates for Chronic Lymphocytic Leukemia from a Library of Approved Drugs 
PLoS ONE  2013;8(9):e75252.
Chronic lymphocytic leukemia (CLL) is an adult lymphoid malignancy with a variable clinical course. There is considerable interest in the identification of new treatments, as most current approaches are not curative. While most patients respond to initial chemotherapy, relapsed disease is often resistant to the drugs commonly used in CLL and patients are left with limited therapeutic options. In this study, we used a luminescent cell viability assay based on ATP levels to find compounds that were potent and efficacious in killing CLL cells. We employed an in-house process of quantitative high throughput screening (qHTS) to assess 8 concentrations of each member of a 2,816 compound library (including FDA-approved drugs and those known to be bio-active from commercial suppliers). Using qHTS we generated potency values on each compound in lymphocytes donated from each of six individuals with CLL and five unaffected individuals. We found 102 compounds efficacious against cells from all six individuals with CLL (“consensus” drugs) with five of these showing low or no activity on lymphocytes from a majority of normal donors, suggesting some degree of specificity for the leukemic cells. To our knowledge, this is the first study to screen a drug library against primary CLL cells to identify candidate agents for anti-cancer therapy. The results presented here offer possibilities for the development of novel drug candidates for therapeutic uses to treat CLL and other diseases.
PMCID: PMC3779154  PMID: 24073257
13.  Targeting the ubiquitin–proteasome system for cancer therapy 
The ubiquitin–proteasome system (UPS) degrades 80 – 90% of intracellular proteins. Cancer cells take advantage of the UPS for their increased growth and decreased apoptotic cell death. Thus, the components that make up the UPS represent a diverse group of potential anti-cancer targets. The success of the first-in-class proteasome inhibitor bortezomib not only proved that the proteasome is a feasible and valuable anti-cancer target, but also inspired researchers to extensively explore other potential targets of this pathway.
Areas covered
This review provides a broad overview of the UPS and its role in supporting cancer development and progression, especially in aspects of p53 inactivation, p27 turnover and NF-κB activation. Also, efforts toward the development of small molecule inhibitors (SMIs) targeting different steps in this pathway for cancer treatment are reviewed and discussed.
Expert opinion
Whereas some of the targets in the UPS, such as the 20S pro-teasome, Nedd8 activating enzyme and HDM2, have been well-established and validated, there remains a large pool of candidates waiting to be investigated. Development of SMIs targeting the UPS has been largely facilitated by state-of-the-art technologies such as high-throughput screening and computer-assisted drug design, both of which require a better understanding of the targets of interest.
PMCID: PMC3773690  PMID: 23822887
cancer therapy; deubiquitinases; E3 ligases; proteasome; small molecule inhibitors; ubiquitin
14.  Firefly luciferase in chemical biology: A compendium of inhibitors, mechanistic evaluation of chemotypes, and suggested use as a reporter 
Chemistry & biology  2012;19(8):1060-1072.
Firefly luciferase (FLuc) is frequently used as a reporter in high-throughput screening assays owing to the exceptional sensitivity, dynamic range, and rapid measurement that bioluminescence affords. However, interaction of small molecules with FLuc has, to some extent, confounded its use in chemical biology and drug discovery. To identify and characterize chemotypes interacting with FLuc, we determined potency values for 360,864 compounds, found in the NIH Molecular Libraries Small Molecule Repository, available in PubChem. FLuc inhibitory activity was observed for 12% of this library with discernible SAR. Characterization of 151 inhibitors demonstrated a variety of inhibition modes including FLuc-catalyzed formation of multisubstrate-adduct enzyme inhibitor complexes. As in some cell-based FLuc reporter assays compounds acting as FLuc inhibitors yield paradoxical luminescence increases, data on compounds acquired from FLuc-dependent assays requires careful analysis as described in this report.
PMCID: PMC3449281  PMID: 22921073
profiling; PubChem; luciferase; quantitative high-throughput screening; qHTS; firefly luciferase; reporter-gene assays; adenylate forming enzymes
15.  Association of metals and proteasome activity in erythrocytes of prostate cancer patients and controls 
PMCID: PMC3736342  PMID: 22422614
Prostate cancer; metal; arsenic; cadmium; copper; lead; zinc; proteasome activity; erythrocyte
16.  Elevated urinary levels of kidney injury molecule-1 among Chinese factory workers exposed to trichloroethylene 
Carcinogenesis  2012;33(8):1538-1541.
Epidemiological studies suggest that trichloroethylene (TCE) exposure may be associated with renal cancer. The biological mechanisms involved are not exactly known although nephrotoxicity is believed to play a role. Studies on TCE nephrotoxicity among humans, however, have been largely inconsistent. We studied kidney toxicity in Chinese factory workers exposed to TCE using novel sensitive nephrotoxicity markers. Eighty healthy workers exposed to TCE and 45 comparable unexposed controls were included in the present analyses. Personal TCE exposure measurements were taken over a 2-week period before urine collection. Ninety-six percent of workers were exposed to TCE below the current US Occupational Safety and Health Administration permissible exposure limit (100 ppm 8h TWA), with a mean (SD) of 22.2 (35.9) ppm. Kidney injury molecule-1 (KIM-1) and Pi-glutathione S transferase (GST) alpha were elevated among the exposed subjects as compared with the unexposed controls with a strong exposure-response association between individual estimates of TCE exposure and KIM-1 (P < 0.0001). This is the first report to use a set of sensitive nephrotoxicity markers to study the possible effects of TCE on the kidneys. The findings suggest that at relatively low occupational exposure levels a toxic effect on the kidneys can be observed. This finding supports the biological plausibility of linking TCE exposure and renal cancer.
Abbreviations:GSTglutathione-S-transferaseKIM-1kidney injury molecule-1NAGN-acetyl-beta-(d)-glucosaminidaseOVMorganic vapour monitoringTCEtrichloroethyleneVEGFvascular endothelial growth factor.
PMCID: PMC3499056  PMID: 22665366
17.  Pyruvate kinase M2 activators promote tetramer formation and suppress tumorigenesis 
Nature chemical biology  2012;8(10):839-847.
Cancer cells engage in a metabolic program to enhance biosynthesis and support cell proliferation. The regulatory properties of pyruvate kinase M2 (PKM2) influence altered glucose metabolism in cancer. PKM2 interaction with phosphotyrosine-containing proteins inhibits enzyme activity and increases availability of glycolytic metabolites to support cell proliferation. This suggests that high pyruvate kinase activity may suppress tumor growth. We show that expression of PKM1, the pyruvate kinase isoform with high constitutive activity, or exposure to published small molecule PKM2 activators inhibit growth of xenograft tumors. Structural studies reveal that small molecule activators bind PKM2 at the subunit interaction interface, a site distinct from that of the endogenous activator fructose-1,6-bisphosphate (FBP). However, unlike FBP, binding of activators to PKM2 promotes a constitutively active enzyme state that is resistant to inhibition by tyrosine-phosphorylated proteins. These data support the notion that small molecule activation of PKM2 can interfere with anabolic metabolism.
PMCID: PMC3711671  PMID: 22922757
18.  An RGD-Modified MRI-Visible Polymeric Vector for Targeted siRNA Delivery to Hepatocellular Carcinoma in Nude Mice 
PLoS ONE  2013;8(6):e66416.
RNA interference (RNAi) has significant therapeutic promise for the genetic treatment of hepatocellular carcinoma (HCC). Targeted vectors are able to deliver small interfering RNA (siRNA) into HCC cells with high transfection efficiency and stability. The tripeptide arginine glycine aspartic acid (RGD)-modified non-viral vector, polyethylene glycol-grafted polyethylenimine functionalized with superparamagnetic iron oxide nanoparticles (RGD-PEG-g-PEI-SPION), was constructed as a magnetic resonance imaging (MRI)-visible nanocarrier for the delivery of Survivin siRNA targeting the human HCC cell line Bel-7402. The biophysical characterization of the RGD-PEG-g-PEI-SPION was performed. The RGD-modified complexes exhibited a higher transfection efficiency in transferring Survivin siRNA into Bel-7402 cells compared with a non-targeted delivery system, which resulted in more significant gene suppression at both the Survivin mRNA and protein expression levels. Then, the level of caspase-3 activation was significantly elevated, and a remarkable level of tumor cell apoptosis was induced. As a result, the tumor growth in the nude mice Bel-7402 hepatoma model was significantly inhibited. The targeting ability of the RGD-PEG-g-PEI-SPION was successfully imaged by MRI scans performed in vitro and in vivo. Our results strongly indicated that the RGD-PEG-g-PEI-SPION can potentially be used as a targeted non-viral vector for altering gene expression in the treatment of hepatocellular carcinoma and for detecting the tumor in vivo as an effective MRI probe.
PMCID: PMC3676333  PMID: 23922634
19.  Physicochemical Characterization of a Thermostable Alcohol Dehydrogenase from Pyrobaculum aerophilum 
PLoS ONE  2013;8(6):e63828.
In this work we characterize an alcohol dehydrogenase (ADH) from the hyperthermophilic archaeon Pyrobaculum aerophilum (PyAeADHII). We have previously found that PyAeADHII has no activity when standard ADH substrates are used but is active when α-tetralone is used as substrate. Here, to gain insights into enzyme function, we screened several chemical libraries for enzymatic modulators using an assay employing α-tetralone. The results indicate that PyAeADHII activity in the presence of α-tetralone was inhibited by compounds such as flunarizine. We also examined metal coordination of the enzyme in solution by performing metal substitution of the enzyme-bound zinc (Zn2+) with cobalt. The solution-based absorption spectra for cobalt substituted PyAeADHII supports substitution at the structural Zn2+ site. To gain structural insight, we obtained the crystal structure of both wild-type and cobalt-substituted PyAeADHII at 1.75 Å and 2.20 Å resolution, respectively. The X-ray data confirmed one metal ion per monomer present only at the structural site with otherwise close conservation to other ADH enzymes. We next determined the co-crystal structure of the NADPH-bound form of the enzyme at 2.35 Å resolution to help define the active site region of the enzyme and this data shows close structural conservation with horse ADH, despite the lack of a catalytic Zn2+ ion in PyAeADHII. Modeling of α-tetralone into the NADPH bound structure suggests an arginine as a possible catalytic residue. The data presented here can yield a better understanding of alcohol dehydrogenases lacking the catalytic zinc as well as the structural features inherent to thermostable enzymes.
PMCID: PMC3673990  PMID: 23755111
20.  Leukemia-related chromosomal loss detected in hematopoietic progenitor cells of benzene-exposed workers 
Benzene exposure causes acute myeloid leukemia, and hematotoxicity, shown as suppression of mature blood and myeloid progenitor cell numbers. As the leukemia-related aneuploidies monosomy 7 and trisomy 8 previously had been detected in the mature peripheral blood cells of exposed workers, we hypothesized that benzene could cause leukemia through the induction of these aneuploidies in hematopoietic stem and progenitor cells. We measured loss and gain of chromosomes 7 and 8 by fluorescence in situ hybridization in interphase colony-forming unit-granulocyte-macrophage (CFU-GM) cells cultured from otherwise healthy benzene-exposed (n=28) and unexposed (n=14) workers. CFU-GM monosomy 7 and 8 levels (but not trisomy) were significantly increased in subjects exposed to benzene overall, compared to levels in the control subjects (p=0.0055 and p=0.0034, respectively). Levels of monosomy 7 and 8 were significantly increased in subjects exposed to <10 ppm (20%, p=0.0419 and 28%, p=0.0056, respectively) and ≥10 ppm (48%, p=0.0045 and 32%, p=0.0354) benzene, compared with controls, and significant exposure-response trends were detected (ptrend=0.0033 and 0.0057). These data show that monosomies 7 and 8 are produced in a dose-dependent fashion in the blood progenitor cells of workers exposed to benzene and may be mechanistically relevant biomarkers of early effect for benzene and other leukemogens.
PMCID: PMC3472034  PMID: 22643707
Benzene; leukemia; monosomy; hematopoietic progenitor
21.  From Bortezomib to other Inhibitors of the Proteasome and Beyond 
Current pharmaceutical design  2013;19(22):4025-4038.
The cancer drug discovery field has placed much emphasis on the identification of novel and cancer-specific molecular targets. A rich source of such targets for the design of novel anti-tumor agents is the ubiqutin-proteasome system (UP-S), a tightly regulated, highly specific pathway responsible for the vast majority of protein turnover within the cell. Because of its critical role in almost all cell processes that ensure normal cellular function, its inhibition at one point in time was deemed non-specific and therefore not worth further investigation as a molecular drug target. However, today the proteasome is one of the most promising anti-cancer drug targets of the century. The discovery that tumor cells are in fact more sensitive to proteasome inhibitors than normal cells indeed paved the way for the design of its inhibitors. Such efforts have led to bortezomib, the first FDA approved proteasome inhibitor now used as a frontline treatment for newly diagnosed multiple myeloma (MM), relapsed/refractory MM and mantle cell lymphoma. Though successful in improving clinical outcomes for patients with hematological malignancies, relapse often occurs in those who initially responded to bortezomib. Therefore, the acquisition of bortezomib resistance is a major issue with its therapy. Furthermore, some neuro-toxicities have been associated with bortezomib treatment and its efficacy in solid tumors is lacking. These observations have encouraged researchers to pursue the next generation of proteasome inhibitors, which would ideally overcome bortezomib resistance, have reduced toxicities and a broader range of anti-cancer activity. This review summarizes the success and limitations of bortezomib, and describes recent advances in the field, including, and most notably, the most recent FDA approval of carfilzomib in July, 2012, a second generation proteasome inhibitor. Other proteasome inhibitors currently in clinical trials and those that are currently experimental grade will also be discussed.
PMCID: PMC3657018  PMID: 23181572
Ubiquitin-proteasome system (UP-S); inhibitors of the 20S proteasome; bortezomib; drug discovery; cancer; natural compounds; clinical studies
22.  Dual-Specific Interaction to Detect DNA on Gold Nanoparticles 
Sensors (Basel, Switzerland)  2013;13(5):5749-5756.
An approach to selectively and efficiently detect single strand DNA is developed by using streptavidin coated gold nanoparticles (StAuNPs) as efficient quenchers. The central concept for the successful detection is the combination the of streptavidin-biotin interaction with specific probe-target DNA hybridization. Biotin labeled probe DNAs act as “bridges” to bring Cy5 labeled targets to the particle surface and the fluorophore dye can be rapidly and efficiently quenched by StAuPNs. By measuring the changes of photoluminescence intensity of Cy5, an efficient, selective, and reversed detection of DNA hybridization is realized. The methodology may pave a new way for simple and rapid detections of biomolecules.
PMCID: PMC3690027  PMID: 23645111
nanoparticles; fluorophore dye; quenching; streptavidin/biotin; DNA hybridization; sensors
23.  Keratinocyte cytoskeletal roles in cell sheet engineering 
BMC Biotechnology  2013;13:17.
There is an increasing need to understand cell-cell interactions for cell and tissue engineering purposes, such as optimizing cell sheet constructs, as well as for examining adhesion defect diseases. For cell-sheet engineering, one major obstacle to sheet function is that cell sheets in suspension are fragile and, over time, will contract. While the role of the cytoskeleton in maintaining the structure and adhesion of cells cultured on a rigid substrate is well-characterized, a systematic examination of the role played by different components of the cytoskeleton in regulating cell sheet contraction and cohesion in the absence of a substrate has been lacking.
In this study, keratinocytes were cultured until confluent and cell sheets were generated using dispase to remove the influence of the substrate. The effects of disrupting actin, microtubules or intermediate filaments on cell-cell interactions were assessed by measuring cell sheet cohesion and contraction. Keratin intermediate filament disruption caused comparable effects on cell sheet cohesion and contraction, when compared to actin or microtubule disruption. Interfering with actomyosin contraction demonstrated that interfering with cell contraction can also diminish cell cohesion.
All components of the cytoskeleton are involved in maintaining cell sheet cohesion and contraction, although not to the same extent. These findings demonstrate that substrate-free cell sheet biomechanical properties are dependent on the integrity of the cytoskeleton network.
PMCID: PMC3599259  PMID: 23442760
Cell sheet; Cytoskeleton; Adhesion; Contraction
24.  Risk factors for hepatic decompensation in patients with primary biliary cirrhosis 
AIM: To examine the clinical features and analyze prognostic factors in a prospective study of primary biliary cirrhosis (PBC) patients.
METHODS: From 1995 to 2010, PBC patients without hepatic decompensation seen at the Peking Union Medical College Hospital were enrolled. Clinical signs and manifestations (pruritus, persistent fatigue, jaundice and pain in the right hypochondrium), laboratory parameters (auto-antibodies for autoimmune hepatic disease, biliary and hepatic enzymes, immunoglobulin, bilirubin, and albumin) and imaging findings were recorded at entry and at specific time points during follow-up. Cox regression and Kaplan-Meier analyses, respectively, assessed the risk factors for hepatic decompensation and survival.
RESULTS: Two hundred and sixty-two PBC patients were enrolled with a median follow-up of 75.2 mo (range, 21-201 mo). The 240 patients were aged 51.5 ± 10.2 years at diagnosis and 91.6% were female. Two hundred and forty-five (93.5%) were seropositive for anti-mitochondrial antibodies. At presentation, 170 patients (64.9%) were symptomatic, while 96 patients (36.6%) had extra-hepatic autoimmune disease. During the follow-up period, 62 (23.7%) patients developed hepatic decompensation of whom four underwent liver transplantation and 17 died. The cumulative survival rate and median survival time were 83.9% and 181.7 mo, respectively. Cox regression analysis revealed that an incomplete ursodeoxycholic acid (UDCA) response or inconsistent treatment [P < 0.001; hazard risk (HR) 95%CI = 2.423-7.541], anti-centromere antibodies (ACA) positivity (P < 0.001; HR 95%CI = 2.516-7.137), alanine aminotransferase ratio (AAR) elevations (P < 0.001; HR 95%CI = 1.357-2.678), and histological advanced liver disease (P = 0.006; HR 95%CI = 1.481-10.847) were predictors of hepatic decompensation. The clinical features and survival of PBC in China are consistent with those described in Western countries.
CONCLUSION: Incomplete UDCA response or inconsistent treatment, ACA positivity, AAR elevations, and advanced histological stage are predictors of decompensation.
PMCID: PMC3582000  PMID: 23467321
Primary biliary cirrhosis; Risk factor; Hepatic decompensation; Survival; Ursodeoxycholic acid response; Anti-centromere antibodies; Histological stage
25.  A Homogeneous, High-Throughput Assay for Phosphatidylinositol 5-Phosphate 4-Kinase with a Novel, Rapid Substrate Preparation 
PLoS ONE  2013;8(1):e54127.
Phosphoinositide kinases regulate diverse cellular functions and are important targets for therapeutic development for diseases, such as diabetes and cancer. Preparation of the lipid substrate is crucial for the development of a robust and miniaturizable lipid kinase assay. Enzymatic assays for phosphoinositide kinases often use lipid substrates prepared from lyophilized lipid preparations by sonication, which result in variability in the liposome size from preparation to preparation. Herein, we report a homogeneous 1536-well luciferase-coupled bioluminescence assay for PI5P4Kα. The substrate preparation is novel and allows the rapid production of a DMSO-containing substrate solution without the need for lengthy liposome preparation protocols, thus enabling the scale-up of this traditionally difficult type of assay. The Z’-factor value was greater than 0.7 for the PI5P4Kα assay, indicating its suitability for high-throughput screening applications. Tyrphostin AG-82 had been identified as an inhibitor of PI5P4Kα by assessing the degree of phospho transfer of γ-32P-ATP to PI5P; its inhibitory activity against PI5P4Kα was confirmed in the present miniaturized assay. From a pilot screen of a library of bioactive compounds, another tyrphostin, I-OMe tyrphostin AG-538 (I-OMe-AG-538), was identified as an ATP-competitive inhibitor of PI5P4Kα with an IC50 of 1 µM, affirming the suitability of the assay for inhibitor discovery campaigns. This homogeneous assay may apply to other lipid kinases and should help in the identification of leads for this class of enzymes by enabling high-throughput screening efforts.
PMCID: PMC3542272  PMID: 23326584

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