Yayin Fang

Combination Effects of Salvianolic Acid B with Low Dose Celecoxib on Inhibition of Head and Neck Squamous Cell Carcinoma Growth in vitro and in vivo

Head and neck squamous cell carcinoma (HNSCC) development is closely associated with inflammation. Cyclooxygenase-2 (COX-2) is an important mediator of inflammation. Therefore, celecoxib, a selective inhibitor of COX-2, was hailed as a promising chemopreventive agent for HNSCC. Dose-dependent cardiac toxicity limits long-term use of celecoxib, but it seems likely that this may be diminished by lowering its dose. We found that salvianolic acid B (Sal-B), isolated from Salvia miltiorrhiza Bge, can effectively suppress COX-2 expression and induce apoptosis in a variety of cancer cell lines. In this study, we report that combination of Sal-B with low-dose celecoxib results in a more pronounced anticancer effect in HNSCC than either agent alone. The combination effects were assessed in four HNSCC cell lines (JHU-06, JHU-011, JHU-013, and JHU-022) by evaluating cell viability, proliferation, and tumor xenograft growth. Cell viability and proliferation were significantly inhibited by both the combined and single-agent treatments. However, the combination treatment significantly enhanced anticancer efficacy in JHU-013 and JHU-022 cell lines compared with the single treatment regimens. A half-dose of daily Sal-B (40 mg/kg/d) and celecoxib (2.5 mg/kg/d) significantly inhibited JHU-013 xenograft growth relative to mice treated with a full dose of Sal-B or celecoxib alone. The combination was associated with profound inhibition of COX-2 and enhanced induction of apoptosis. Taken together, these results strongly suggest that combination of Sal-B, a multifunctional anticancer agent, with low-dose celecoxib holds potential as a new preventive strategy in targeting inflammatory-associated tumor development. Cancer Prev Res; 3(6); 787–96. ©2010 AACR.

Enaminones 8: CoMFA and CoMSIA studies on some anticonvulsant enaminones

3D-QSAR studies comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were carried out on 26 structurally diverse subcutaneous pentylenetetrazol (scPTZ) active enaminone analogues, previously synthesized in our laboratory. CoMFA and CoMSIA were employed to generate models to define the specific structural and electrostatic features essential for enhanced binding to the putative GABA receptor. The 3D-QSAR models demonstrated a reliable ability to predict the CLogP of the active anticonvulsant enaminones, resulting in a q(2) of 0.558 for CoMFA, and a q(2) of 0.698 for CoMSIA. The outcomes of the contour maps for both models provide detailed insight for the structural design of novel enaminone derivatives as potential anticonvulsant agents.

Molecular Dynamics Simulations of the Orientation of Ni(II)•Gly-Gly-His and Ni(II)•Arg-Gly-His Metallopeptide-DNA Association.

Ni(II)•Xaa-Gly-His metallopeptides (where Xaa is any α-amino acid) bind selectively to the minor groove of A/T-rich DNA regions as a function of their amino acid composition and chirality. Molecular dynamics simulations were performed to clarify the most likely binding orientations of Ni(II)•Gly-Gly-His and Ni(II)•L-Arg-Gly-His upon association with the B-form oligonucleotide d(CGCGAATTCGCG)2. Upon examination of four possible docking orientations (I-IV), these studies indicated that both metallopeptides favor association with DNA via I, involving insertion of the edge of the metallopeptide containing the amino-terminal N-H and the imidazole pyrrole N-H group of His into the minor groove. These metallopeptide moieties play important roles in this DNA recognition mode by functioning as H-bond donors to minor groove acceptors such as the N3 of adenine or the O2 of thymine located on the floor of the minor groove. The positively charged side chain of L-Arg was found to enhance DNA recognition relative to that exhibited by Ni(II)•Gly-Gly-His through an increased electrostatic interaction, its favorable stereochemistry, and by providing a third point of contact with the minor groove floor. The simulation of orientation I was found to reproduce the experimentally supported DNA-metallopeptide orientation, revealing factors that are important for the further development of DNA-binding ligands.

Novel drug design for Chagas disease via targeting Trypanosoma cruzi tubulin: Homology modeling and binding pocket prediction on Trypanosoma cruzi tubulin polymerization inhibition by naphthoquinone derivatives.

Chagas disease, also called American trypanosomiasis, is a parasitic disease caused by Trypanosoma cruzi (T. cruzi). Recent findings have underscored the abundance of the causative organism, (T. cruzi), especially in the southern tier states of the US and the risk burden for the rural farming communities there. Due to a lack of safe and effective drugs, there is an urgent need for novel therapeutic options for treating Chagas disease. We report here our first scientific effort to pursue a novel drug design for treating Chagas disease via the targeting of T. cruzi tubulin. First, the anti T. cruzi tubulin activities of five naphthoquinone derivatives were determined and correlated to their anti-trypanosomal activities. The correlation between the ligand activities against the T. cruzi organism and their tubulin inhibitory activities was very strong with a Pearsons r value of 0.88 (P value <0.05), indicating that this class of compounds could inhibit the activity of the trypanosome organism via T. cruzi tubulin polymerization inhibition. Subsequent molecular modeling studies were carried out to understand the mechanisms of the anti-tubulin activities, wherein, the homology model of T. cruzi tubulin dimer was generated and the putative binding site of naphthoquinone derivatives was predicted. The correlation coefficient for ligand anti-tubulin activities and their binding energies at the putative pocket was found to be r=0.79, a high correlation efficiency that was not replicated in contiguous candidate pockets. The homology model of T. cruzi tubulin and the identification of its putative binding site lay a solid ground for further structure based drug design, including molecular docking and pharmacophore analysis. This study presents a new opportunity for designing potent and selective drugs for Chagas disease.

Genome-Targeted Drug Design: Understanding the Netropsin-DNA Interaction

Knowledge of the sequence of the human genome has provided significant opportunities to exploit DNA as a target in the rational design of therapeutic agents. Among agents that target DNA, netropsin exhibits a strong preference for binding A/T rich regions. In order to investigate the key factors responsible for DNA recognition and binding by netropsin, molecular dynamics simulations were carried out on a DNA-netropsin complex in which two netropsin molecules are bound to each AATT site of the 16-mer d(CTTAATTCGAATTAAG)(2). In this complex, the two netropsins are bound to the DNA minor groove in a head-to-head orientation with the guanidinium-termini of both netropsins pointed toward the center of the DNA. Despite their identical environments, molecular dynamics simulations showed that the two netropsins exhibited differences in their respective RMS behaviors, binding energies, minor groove width fluctuations, and rotations of their structural planes. These observations suggest that DNA recognition and binding by small molecules may be governed by mechanism(s) that are much more complex than initially anticipated and may represent unexpected challenges in genome-targeted drug design.

AM1 study of catalytic hydrogenation of 3-anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-diones

Abstract 3-( p -methyl)anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-dione was selected as the model reactant compound to study the catalytic hydrogenation of 3-anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-diones by the AM1 semi-empirical method. Molecular information such as net charges, bond orders, values of frontier orbital energies, composition, proportions and bonding contribution was acquired and analyzed. Thus, possible reactive sites were proposed and the reaction mechanism was postulated via two different pathways. The postulated intermediates and products were also computed using the AM1 method. Their heat of formation values and energies of HOMO/LUMO/SOMO indicate that the mechanism of catalytic hydrogenation of 3-anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-diones is hydrogenolytic cleavage on a dihydropyrandione ring, not the simple addition of a C Cdouble bond. Therefore, the experiment result is elucidated theoretically.

Investigation of chiral recognition by molecular micelles with molecular dynamics simulations

ABSTRACT Molecular dynamics simulations were used to characterize the binding of the chiral drugs chlorthalidone and lorazepam to the molecular micelle poly-(sodium undecyl-(L)-leucine-valine). The project’s goal was to characterize the nature of chiral recognition in capillary electrophoresis separations that use molecular micelles as the chiral selector. The shapes and charge distributions of the chiral molecules investigated, their orientations within the molecular micelle chiral binding pockets, and the formation of stereoselective intermolecular hydrogen bonds with the molecular micelle were all found to play key roles in determining where and how lorazepam and chlorthalidone enantiomers interacted with the molecular micelle. GRAPHICAL ABSTRACT

Using molecular dynamics simulations to identify the key factors responsible for chiral recognition by an amino acid-based molecular micelle

Abstract Molecular dynamics (MD) simulations were used to investigate the binding of six chiral compounds to the amino acid-based molecular micelle (MM) poly-(sodium undecyl-(L)-leucine-leucine) or poly(SULL). The MM investigated is used as a chiral selector in capillary electrophoresis. The project goal was to characterize the chiral recognition mechanism in these separations and to move toward predictive models to identify the best amino acid-based MM for a given separation. Poly(SULL) was found to contain six binding sites into which chiral compounds could insert. Four sites had similar sizes, shapes, and electrostatic properties. Enantiomers of alprenolol, propranolol, 1,1′-bi-2-naphthyl-2,2′-diyl hydrogen phosphate, 1,1′-bi-2-naphthol, chlorthalidone, or lorazepam were separately docked into each binding pocket and MD simulations with the resulting intermolecular complexes were performed. Solvent-accessible surface area calculations showed the compounds preferentially associated with binding sites where they penetrated into the MM core and shielded their non-polar atoms from solvent. Furthermore, with five of the six compounds the enantiomer with the most favorable free energy of MM association also experienced the most favorable intermolecular hydrogen bonding interactions with the MM. This result suggests that stereoselective intermolecular hydrogen bonds play an important role in chiral discrimination in separations using amino acid-based MMs.GRAPHICAL ABSTRACT

Abstract 3170: Comprehensive analysis of the microRNA-128 function in head and neck squamous cell carcinoma

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL MicroRNAs are 22∼nucleotide-long endogenously expressed, highly conserved noncoding RNAs with important regulatory functions in proliferation, apoptosis, and metastasis. miR-128 a brain-enriched, which is transcribes from two gene copies (miR-128-1 and miR-128-2) on chromosome 2 and chromosome 3 which produce identical mature forms. miR-128 is most commonly in gliomas that have shown to function as a tumor suppressor which inhibits cell proliferation. Proteomic alterations of prostate cancer show miR-128 to down regulate cell invasiveness. Here we evaluated the role of miRNA-128 in HNSCC, to identify its putative targets and elucidate the possible mechanisms underlining the function of miR-128 in HNSCC. We established HNSCC cell lines that stably expressed individual members of the miR-128 using a lentiviral delivery system. The levels of miR-128 and their targeted proteins were analyzed by qRT-PCR and Western blot. miR-128 affinity was elucidated by MTT, colony formation, flow cytometry, and a tumor xenograft model. Two kinds of stably transfected HNSCC cell lines, including JHU-22miR-128 transfected with miR-128 and a vector control cell line JHU-22vector, were generated as a testing system. The miR-128 level in the JHU-22miR-128 cells was eleven fold higher than in JHU-22vector cells. We found that overexpression of miR-128 enable to effectively suppress cell viability (30%), decrease of proliferation (55%), and significantly reduced solid tumor growth in tumor xenografts models compared to the control groups. Transfected miR-128 cells exhibited astrocyte morphology. The inhibition mechanism of miR-128 was determined by evaluating five putative targets (BMI-1, BAG2, BAX, H3f3b, and Paip2) of miR-128. Overall, miR-128 enables to directly inhibit all these targets, but the binding affinity of miR-128 is dominantly towards to BMI-1 and BAG-2 targets. Conclusions: miR-128 exhibits anti-proliferative effects and phenotypic alteration in HNSCC by targeting multiple predicted conserved targets activity function in apoptosis, cell cycle, transcription, and translation. Our results provide a better understanding of miR-128 function in HNSCC and the potential targets to develop novel diagnostic markers and targeted therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3170. doi:1538-7445.AM2012-3170