Showing papers by "Yung-Chi Cheng published in 2011"

Simple and convenient G-quadruplex-based turn-on fluorescence assay for 3' → 5' exonuclease activity.

Abstract: A selective, oligonucleotide-based, label-free, turn-on fluorescence detection method for 3' → 5' exonuclease activity has been developed using crystal violet as a G-quadruplex-binding probe. The assay is highly simple and rapid, does not require the use of gel-based equipment or radioisotopic labeling, and is amenable to high-throughput and real-time detection. A proof-of-concept of this assay has been demonstrated for prokaryotic Exonuclease III (ExoIII) and human TREX1.

Interaction of a traditional Chinese Medicine (PHY906) and CPT-11 on the inflammatory process in the tumor microenvironment

Abstract: Background - Traditional Chinese Medicine (TCM) has been used for thousands of years to treat or prevent diseases, including cancer. Good manufacturing practices (GMP) and sophisticated product analysis (PhytomicsQC) to ensure consistency are now available allowing the assessment of its utility. Polychemical Medicines, like TCM, include chemicals with distinct tissue-dependent pharmacodynamic properties that result in tissue-specific bioactivity. Determining the mode of action of these mixtures was previously unsatisfactory; however, information rich RNA microarray technologies now allow for thorough mechanistic studies of the effects complex mixtures. PHY906 is a long used four herb TCM formula employed as an adjuvant to relieve the side effects associated with chemotherapy. Animal studies documented a decrease in global toxicity and an increase in therapeutic effectiveness of chemotherapy when combined with PHY906.

Regulation of Inflammation by the NF-κB Pathway in Ovarian Cancer Stem Cells

Abstract: Problem—The NFκB pathway is a major source of pro-inflammatory cytokines, which may contribute to cancer chemoresistance. We showed that constitutive NFκB activity is characteristic of the ovarian cancer stem cells (OCSCs). The aim of this study is to determine if the inhibition of NFκB by Eriocalyxin B (EriB) in the OCSCs may induce cell death in otherwise chemoresistant cells. Methods—OCSCs and mature ovarian cancer cells (mOCCs) were treated with increasing concentrations of EriB. Cell viability was measured using the Celltiter 96 assay and caspase activity was quantified using Caspase-Glo™ assay. Cytokine levels were quantified using xMAP technology. Results—EriB decreased the percent of viable cells in all cultures tested with GI50 of 0.5 −1µM after 48h of treatment. The intracellular changes associated with EriB-induced cell death are: 1) inhibition of NF-κB activity; 2) decreased cytokine production; 3) activation of caspases; and 4) down-regulation of XIAP. In addition, EriB is able to sensitize OCSCs to TNFα and FasLmediated cell death. Conclusions—Inhibition of the NFκB pathway induces cell death in the OCSCs. Since the OCSCs may represent the source of recurrence and chemoresistance, the use of NFκB inhibitors like EriB may prevent recurrence in ovarian cancer patients.

Ellagic Acid, the Active Compound of Phyllanthus urinaria, Exerts In Vivo Anti-Angiogenic Effect and Inhibits MMP-2 Activity.

Abstract: This study aimed to assess the potential anti-angiogenic mechanism of Phyllanthus urinaria (P. urinaria) and characterize the major compound in P. urinaria that exerts anti-angiogenic effect. The water extract of P. urinaria and Ellagic Acid were used to evaluate the anti-angiogenic effect in chorioallantoic membrane (CAM) in chicken embryo and human vascular endothelial cells (HUVECs). The matrix metalloproteinase-2 (MMP-2) activity was determined by gelatin zymography. The mRNA expressions of MMP-2, MMP-14 and tissue inhibitor of metalloproteinase-2 (TIMP-2) were analyzed by reverse transcription polymerase chain reaction (RT-PCR). Level of MMP-2 proteins in conditioned medium or cytosol was determined by western blot analysis. We confirmed that P. urinaria's in vivo anti-angiogenic effect was associated with a reduction in MMP-2 activity. Ellagic acid, one of the major polyphenolic components as identified in P. urinaria by high performance liquid chromatography mass spectrometry (HPLC/MS), exhibited the same anti-angiogenic effect in vivo. Both P. urinaria and Ellagic Acid inhibited MMP-2 activity in HUVECs with unchanged mRNA level. The mRNA expression levels of MMP-14 and TIMP-2 were not altered either. Results from comparing the change of MMP-2 protein levels in conditioned medium and cytosol of HUVECs after the P. urinaria or Ellagic Acid treatment revealed an inhibitory effect on the secretion of MMP-2 protein. This study concluded that Ellagic Acid is the active compound in P. urinaria to exhibit anti-angiogenic activity and to inhibit the secretion of MMP-2 protein from HUVECs.

Alizarine derivatives as new dual inhibitors of the HIV-1 reverse transcriptase-associated DNA polymerase and RNase H activities effective also on the RNase H activity of non-nucleoside resistant reverse transcriptases.

Abstract: HIV-1 reverse transcriptase (RT) has two associated activities, DNA polymerase and RNase H, both essential for viral replication and validated drug targets. Although all RT inhibitors approved for therapy target DNA polymerase activity, the search for new RT inhibitors that target the RNase H function and are possibly active on RTs resistant to the known non-nucleoside inhibitors (NNRTI) is a viable approach for anti-HIV drug development. In this study, several alizarine derivatives were synthesized and tested for both HIV-1 RT-associated activities. Alizarine analogues K-49 and KNA-53 showed IC(50) values for both RT-associated functions of ∼ 10 μm. When tested on the K103N RT, both derivatives inhibited the RT-associated functions equally, whereas when tested on the Y181C RT, KNA-53 inhibited the RNase H function and was inactive on the polymerase function. Mechanism of action studies showed that these derivatives do not intercalate into DNA and do not chelate the divalent cofactor Mg(2+) . Kinetic studies demonstrated that they are noncompetitive inhibitors, they do not bind to the RNase H active site or to the classical NNRTI binding pocket, even though efavirenz binding negatively influenced K-49/KNA-53 binding and vice versa. This behavior suggested that the alizarine derivatives binding site might be close to the NNRTI binding pocket. Docking experiments and molecular dynamic simulation confirmed the experimental data and the ability of these compounds to occupy a binding pocket close to the NNRTI site.

Molecular histology analysis by matrix‐assisted laser desorption/ionization imaging mass spectrometry using gold nanoparticles as matrix

Abstract: Gold nanoparticles (AuNPs) were applied and optimized as matrix for matrix-assisted laser desorption/ionization mass spectrometry analysis of animal tissues, and enabled histological analysis of animal tissues at molecular level by imaging mass spectrometry (IMS). AuNPs were coated on animal tissue in a solvent-free manner via argon ion sputtering. Metabolites, including neurotransmitters, fatty acids and nucleobases, were directly detected from mouse brain tissue. Based on region-specific chemical profiles, fine histological features of mouse brain tissue and heterogeneous regions of tumor tissue were both revealed. Copyright © 2011 John Wiley & Sons, Ltd.

A randomized, double-blind phase III study of icotinib versus gefitinib in patients with advanced non-small cell lung cancer (NSCLC) previously treated with chemotherapy (ICOGEN).

Abstract: 7522 Background: Icotinib is a potent and selective EGFR-TKI. Of 88 kinases profiled, Icotinib (Ic) powerfully inhibited EGFR and its 3 mutants, with no meaningful inhibition of the rest of kinases...

Synthesis of 4′-Ethynyl-2′-deoxy-4′-thioribonucleosides and Discovery of a Highly Potent and Less Toxic NRTI

Abstract: The synthesis of 4′-ethynyl-2′-deoxy-4′-thioribonucleosides was carried out utilizing an electrophilic glycosidation in which 4-ethynyl-4-thiofuranoid glycal 16 served as a glycosyl donor. Electrophilic glycosidation between 16 and the silylated nucleobases (N4-acetylcytosine, N6-benzoyladenine, and N2-acetyl-O6-diphenylcarbamoylguanine) was carried out in the presence of N-iodosuccinimide (NIS), leading to the exclusive formation of the desired β-anomers 29, 33, and 36. Anti-HIV studies demonstrated that these 4′-thio nucleosides were less cytotoxic to T-lymphocyte (i.e., MT-4 cells) than the corresponding 4′-ethynyl derivatives of 2′-deoxycytidine (44), 2′-deoxyadenosine (45), and 2′-deoxyguanosine (46). Comparison of the selectivity indices (SI) was made between 4′-thionucleosides (32, 41, and 43) and the corresponding 4′-oxygen analogues 44-46 by using the reported CC50 and EC50 values. In the case of cytosine and adenine nucleosides, comparable SI values were obtained as follows: 32 (545) and 44 (458...

Determinants of Individual Variation in Intracellular Accumulation of Anti-HIV Nucleoside Analog Metabolites

Abstract: Individual variation in response to antiretroviral therapy is well-known, but it is not clear if demographic characteristics such as gender, age, and ethnicity are responsible for the variation. To optimize anti-HIV therapy and guide antiretroviral drug discovery, determinants that cause variable responses to therapy need to be evaluated. We investigated the determinants of intracellular concentrations of nucleoside analogs using peripheral blood mononuclear cells from 40 healthy donors. We observed individual differences in the concentrations of the intracellular nucleoside analogs; the mean concentrations of the triphosphate metabolite of ethynylstavudine (4′-Ed4T), zidovudine (AZT), and lamivudine (3TC) were 0.71 pmol/106 cells (minimum and maximum, 0.10 and 3.00 pmol/106 cells, respectively), 0.88 pmol/106 cells (minimum and maximum, 0.10 and 15.18 pmol/106 cells, respectively), and 1.70 pmol/106 cells (minimum and maximum, 0.20 and 7.73 pmol/106 cells, respectively). Gender and ethnicity had no effect on the concentration of 4′-Ed4T and 3TC metabolites. There was a trend for moderation of the concentrations of AZT metabolites by gender (P = 0.17 for gender·metabolite concentration). We observed variability in the activity and expression of cellular kinases. There was no statistically significant correlation between thymidine kinase 1 (TK-1) activity or expression and thymidine analog metabolite concentrations. The correlation between the activity of deoxycytidine kinase (dCK) and the 3TC monophosphate metabolite concentration showed a trend toward significance (P = 0.1). We observed an inverse correlation between the multidrug-resistant protein 2 (MRP2) expression index and the concentrations of AZT monophosphate, AZT triphosphate, and total AZT metabolites. Our findings suggest that the observed variation in clinical response to nucleoside analogs may be due partly to the individual differences in the intracellular concentrations, which in turn may be affected by the cellular kinases involved in the phosphorylation pathway and ATP-binding cassette (ABC) transport proteins.

A phase II study (CTONG0803) of erlotinib as second-line treatment in advanced non-small cell lung cancer (NSCLC) patients (pts) with asymptomatic brain metastases (BM) after first-line chemotherapy (CT).

Abstract: 7605 Background: About 20–30% of all pts with NSCLC develop BM, leading to a poor prognosis and a median survival of <6 months after whole brain radiotherapy. The role of systemic CT in the managem...

Ump/cmpk is not the critical enzyme in the metabolism of pyrimidine ribonucleotide and activation of deoxycytidine analogs in human rko cells

Abstract: Background Human UMP/CMP kinase was identified based on its enzymatic activity in vitro. The role of this protein is considered critical for the maintenance of pyrimidine nucleotide pool profile and for the metabolism of pyrimidine analogs in cells, based on the in vitro study of partially purified enzyme and recombinant protein. However, no detailed study has yet addressed the role of this protein in nucleotide metabolism in cells.