Structure-based and ligand-based drug design for HER 2 receptor

DFT, molecular docking and molecular dynamics simulation studies on some recent natural products revealing their EGFR tyrosine kinase inhibition potential

Phytochemicals are important chemical compounds in pharmaceutical chemistry. These natural compounds have interesting biological activities, including anticancer, as well as many other functions. EGFR (epidermal growth factor receptor) tyrosine kinase inhibition is emerging as one of the accepted methods in the treatment of cancer. On the other hand, computer-aided drug design has become an increasingly important field of study due to its many important advantages such as efficient use of time and other resources. In this study, fourteen phytochemicals which have triterpenoid structure and have recently entered the literature were investigated computationally for their potential as EGFR tyrosine kinase inhibitors. In the study, DFT (density functional theory) calculations, molecular docking, molecular dynamics simulations, binding free energy calculations with the use of MM-PBSA (molecular mechanics Poisson-Boltzmann Surface Area) method, and ADMET predictions were performed. The obtained results were compared to the results obtained for reference drug Gefitinib. Results showed that the investigated natural compounds are promising structures for EGFR tyrosine kinase inhibition.Communicated by Ramaswamy H. Sarma.

The Breast Cancer Protooncogenes HER2, BRCA1 and BRCA2 and Their Regulation by the iNOS/NOS2 Axis

The expression of inducible nitric oxide synthase (iNOS; NOS2) and derived NO in various cancers was reported to exert pro- and anti-tumorigenic effects depending on the levels of expression and the tumor types. In humans, the breast cancer level of iNOS was reported to be overexpressed, to exhibit pro-tumorigenic activities, and to be of prognostic significance. Likewise, the expression of the oncogenes HER2, BRCA1, and BRCA2 has been associated with malignancy. The interrelationship between the expression of these protooncogenes and oncogenes and the expression of iNOS is not clear. We have hypothesized that there exist cross-talk signaling pathways between the breast cancer protooncogenes, the iNOS axis, and iNOS-mediated NO mutations of these protooncogenes into oncogenes. We review the molecular regulation of the expression of the protooncogenes in breast cancer and their interrelationships with iNOS expression and activities. In addition, we discuss the roles of iNOS, HER2, BRCA1/2, and NO metabolism in the pathophysiology of cancer stem cells. Bioinformatic analyses have been performed and have found suggested molecular alterations responsible for breast cancer aggressiveness. These include the association of BRCA1/2 mutations and HER2 amplifications with the dysregulation of the NOS pathway. We propose that future studies should be undertaken to investigate the regulatory mechanisms underlying the expression of iNOS and various breast cancer oncogenes, with the aim of identifying new therapeutic targets for the treatment of breast cancers that are refractory to current treatments.

Ligand decorated chitosan as an advanced nanocarrier for targeted delivery: a critical review

Nontargeted delivery systems present nonspecific delivery, low transfection efficiency and high toxicity. Ligand-conjugated chitosan (CS) nanocarriers have emerged as an outstanding option for achieving active delivery specifically and preferentially to the target sites by exploiting receptors mediated endocytosis. Mannosylated CS nanocarriers have brought tremendous breakthrough in gene therapy and have proven to be an excellent choice for treatment of infectious and inflammatory diseases. Similarly, folate and antibodies-conjugated CS play a significant role in diagnosis and treatment of various cancers. Current evidences obviously propose ligand-decorated CS as an attractive option for diagnosis and treatment of dreadful conditions. In order to bring huge revolution in the field of targeted delivery, challenges associated with these nanocarriers needs to be addressed.

Synthesis, cytotoxic evaluation, and molecular docking studies of the semi-synthetic "triterpenoid-steroid" hybrids

Synthetic transformations of steroids for drug discovery and improvement of drug effectiveness have been an important part of modern medicinal chemistry and pharmaceutical sciences. Pentacyclic triterpenoids, being represented in the nature by various structures and biogenetically related to steroids, can largely expand the spectrum of biologically active steroidal agents via synthesis of the so-called "triterpenoid-steroid" hybrids. In the presented work, the nitrile anion cyclizations of 3,4-secolupane and 3,4-seco-oleanane nitriles and follow-up synthetic transformations of the cyclized products with formation of the gemm-dimethyl-free A ring "triterpenoid-steroid" hybrids were studied. Furthermore, the resulting cyclic compounds were modified at C3, C4, and/or C5 positions of ring A, as well as at C20, C28, and C30 positions of the isopropylidene moiety in the case of lupane triterpenoids. The cytotoxic effect of the synthesized compounds against seven cancer cell lines HEp-2, HCT 116, MS, RD TE32, A549, MCF7, and PC3 was evaluated. The in silico identification of potential anticancer protein targets with regard to the compounds, which were active at micromolar concentrations against tested cell lines, was carried out. The molecular docking studies showed that compound 19, which demonstrated most pronounced cytotoxicity (IC₅₀ 0.64-3.17 μM) against all tested cell lines, fits well the active sites of CDK6 and HER2/neu.

Comparative Proteomics Reveals that Phosphorylation of β Carbonic Anhydrase 1 Might be Important for Adaptation to Drought Stress in Brassica napus

Little is known about the mechanism of drought tolerance in rapeseed (Brassica napus L.). In this study, different morphological and physiological responses to drought stress were studied in three rapeseed cultivars. For the cultivar 2AF009 with high drought tolerance, comparative proteomic analyses were conducted to determine the molecular mechanism behind. Approximately 138 differentially abundant proteins (DAPs) and 1232 phosphoproteins containing 4469 phosphopeptides were identified. Furthermore, 337 phosphoproteins containing 547 phosphorylation sites demonstrated significant changes. These drought-responsive DAPs and phosphoproteins were mainly involved in signal transduction, photosynthesis, and glutathione-ascorbate metabolism. Notably, 9 DAPs were also identified as drought-responsive phosphoproteins, especially beta carbonic anhydrase 1 (βCA1), which was represented by eight distinct protein spots with different abundant levels during drought stress. Tyr207 phosphorylated site of βCA1 was down-regulated at the phosphorylation level during drought stress, which was also located in the substrate-binding active region of three-dimensional (3D) structure. Moreover, drought stress inhibited CA activity. We concluded that Tyr207 was the most likely phosphorylation target affecting the enzyme activity, and phosphorylation of βCA1 might be important for the response to drought stress in rapeseed. The study provided a new clue for the drought tolerance mechanism in B.napus.

Multiple target drug cocktail design for attacking the core network markers of four cancers using ligand-based and structure-based virtual screening methods

BACKGROUND

Computer-aided drug design has a long history of being applied to discover new molecules to treat various cancers, but it has always been focused on single targets. The development of systems biology has let scientists reveal more hidden mechanisms of cancers, but attempts to apply systems biology to cancer therapies remain at preliminary stages. Our lab has successfully developed various systems biology models for several cancers. Based on these achievements, we present the first attempt to combine multiple-target therapy with systems biology.

METHODS

In our previous study, we identified 28 significant proteins--i.e., common core network markers--of four types of cancers as house-keeping proteins of these cancers. In this study, we ranked these proteins by summing their carcinogenesis relevance values (CRVs) across the four cancers, and then performed docking and pharmacophore modeling to do virtual screening on the NCI database for anti-cancer drugs. We also performed pathway analysis on these proteins using Panther and MetaCore to reveal more mechanisms of these cancer house-keeping proteins.

RESULTS

We designed several approaches to discover targets for multiple-target cocktail therapies. In the first one, we identified the top 20 drugs for each of the 28 cancer house-keeping proteins, and analyzed the docking pose to further understand the interaction mechanisms of these drugs. After screening for duplicates, we found that 13 of these drugs could target 11 proteins simultaneously. In the second approach, we chose the top 5 proteins with the highest summed CRVs and used them as the drug targets. We built a pharmacophore and applied it to do virtual screening against the Life-Chemical library for anti-cancer drugs. Based on these results, wet-lab bio-scientists could freely investigate combinations of these drugs for multiple-target therapy for cancers, in contrast to the traditional single target therapy.

CONCLUSIONS

Combination of systems biology with computer-aided drug design could help us develop novel drug cocktails with multiple targets. We believe this will enhance the efficiency of therapeutic practice and lead to new directions for cancer therapy.

In vitro antiviral effects and 3D QSAR study of resveratrol derivatives as potent inhibitors of influenza H1N1 neuraminidase

The anti-influenza virus activities of 50 resveratrol (RV: 3, 5, 4'-trihydroxy-trans-stilbene) derivatives were evaluated using a neuraminidase (NA) activity assay. The results showed that 35 compounds exerted an inhibitory effect on the NA activity of the influenza virus strain A/PR/8/34 (H1N1) with 50% inhibitory concentration (IC50) values ranging from 3.56 to 186.1 μm. Next, the 35 RV derivatives were used to develop 3D quantitative structure-activity relationship (3D QSAR) models for understanding the chemical-biological interactions governing their activities against NA. The comparative molecular field analysis (CoMFA r2=0.973, q2=0.620, qtest2=0.661) and the comparative molecular similarity indices analysis (CoMSIA r2=0.956, q2=0.610, qtest2=0.531) were applied. Afterward, molecular docking was performed to study the molecular interactions between the RV derivatives and NA. Finally, a cytopathic effect (CPE) reduction assay was used to evaluate the antiviral effects of the RV derivatives in vitro. Time-of-addition studies demonstrated that the RV derivatives might have a direct effect on viral particle infectivity. Our results indicate that the RV derivatives are potentially useful antiviral compounds for new drug design and development for influenza treatment.

Lead screening for CXCR4 of the human HIV infection receptor inhibited by traditional Chinese medicine

The acquired immunodeficiency syndrome (AIDS) is a serious worldwide disease caused by the human immunodeficiency virus (HIV) infection. Recent research has pointed out that the G protein-coupled chemokine receptor CXCR4 and the coreceptor C-C chemokine receptor type 5 (CCR5) are important targets for HIV infection. The traditional Chinese medicine (TCM) database has been screened for candidate compounds by simulating molecular docking and molecular dynamics against HIV. Saussureamine C, 5-hydroxy-L-tryptophan, and diiodotyrosine are selected based on the highest docking score. The molecular dynamics is helpful in the analysis and detection of protein-ligand interactions. According to the analysis of docking poses, hydrophobic interactions, hydrogen bond variations, and the comparison of the effect on CXCR4 and CCR5, these results indicate Saussureamine C may have better effect on these two receptors. But for some considerations, diiodotyrosine could make the largest variation and may have some efficacy contrary to expectations.

Investigation of estrogen receptor (ESR1) for breast cancer from traditional Chinese medicine

Recently, an important topic of breast cancer had been published in 2013. In this report, estrogen receptor (ESR1) had defined the relation of hormone-cause breast cancer. The screening of traditional Chinese medicine (TCM) database has found the molecular compounds by simulating molecular docking and molecular dynamics to regulate ESR1. S-Allylmercaptocysteine and 5-hydroxy-L-tryptophan are selected according to the highest docking score than that of other TCM compounds and Raloxifene (control). The simulation from molecular dynamics is helpful in analyzing and detecting the protein-ligand interactions. After a comparing the control and the Apo form, then based on the docking poses, hydrophobic interactions, hydrogen bond and structure variations, this research postulates that S-allylmercaptocysteine may be more appropriate than other compounds for protein-ligand interaction.

In silico investigation of traditional Chinese medicine compounds to inhibit human histone deacetylase 2 for patients with Alzheimer's disease

Human histone deacetylase 2 (HDAC2) has been identified as being associated with Alzheimer's disease (AD), a neuropathic degenerative disease. In this study, we screen the world's largest Traditional Chinese Medicine (TCM) database for natural compounds that may be useful as lead compounds in the search for inhibitors of HDAC2 function. The technique of molecular docking was employed to select the ten top TCM candidates. We used three prediction models, multiple linear regression (MLR), support vector machine (SVM), and the Bayes network toolbox (BNT), to predict the bioactivity of the TCM candidates. Molecular dynamics simulation provides the protein-ligand interactions of compounds. The bioactivity predictions of pIC50 values suggest that the TCM candidatesm, (-)-Bontl ferulate, monomethylcurcumin, and ningposides C, have a greater effect on HDAC2 inhibition. The structure variation caused by the hydrogen bonds and hydrophobic interactions between protein-ligand interactions indicates that these compounds have an inhibitory effect on the protein.

An investigation of small GTPases in relation to liver tumorigenesis using traditional Chinese medicine

Recently, an important topic of liver tumorigenesis had been published in 2013. In this report, Ras and Rho had defined the relation of liver tumorigenesis. The traditional Chinese medicine (TCM) database has been screened for molecular compounds by simulating molecular docking and molecular dynamics to regulate Ras and liver tumorigenesis. Saussureamine C, S-allylmercaptocysteine, and Tryptophan are selected based on the highest docking score than other TCM compounds. The molecular dynamics are helpful in the analysis and detection of protein-ligand interactions. Based on the docking poses, hydrophobic interactions, and hydrogen bond variations, this research surmises are the main regions of important amino acids in Ras. In addition to the detection of TCM compound efficacy, we suggest Saussureamine C is better than the others for protein-ligand interaction.

Insight into HIV of IFN-induced myxovirus resistance 2 (MX2) expressed by traditional Chinese medicine

Recently, an important topic of the acquired immunodeficiency syndrome (AIDS) had been published in 2013. In this report, the expression of the IFN-induced myxovirus resistance 2 (MX2) had been defined the function to kill the human immunodeficiency virus (HIV). The screening from the Traditional Chinese Medicine (TCM) database by simulating molecular docking and molecular dynamics could select candidate compounds, which may express MX2 against HIV. Saussureamine C, Crotalaburnine, and Precatorine are selected based on the highest docking score and other TCM compounds. The data from molecular dynamics are helpful in the analysis and detection of protein-ligand interactions. According to the docking poses, hydrophobic interactions, and hydrogen bond with structure variations, this research could assess the interaction between protein and ligand interaction. In addition to the detection of TCM compound efficacy, we suggest that Saussureamine C is better than the others in protein-ligand interaction and the structural variation to express MX2.

Lead screening for HIV-1 integrase (IN) inhibited by traditional Chinese medicine

Human immunodeficiency virus causes the acquired immunodeficiency syndrome (AIDS) and becomes a serious world-wide problem because of this disease's rapid propagation and incurability. Integrase strand transfer inhibitors (INSTIs) supports HIV have rapid drug resistance for antitreatment. Screening the traditional Chinese medicine (TCM) database by simulating molecular docking and molecular dynamics may select molecular compounds to inhibit INSTIs against HIV drug resistance. (S)-cathinone and (1S,2S)-norpseudoephedrine are selected based on structure and ligand-based drugs are designed and then get higher bioactivity predicted score from SVM than Raltegravir and other TCM compounds. The molecular dynamics are helpful in the analysis and detection of protein-ligand interactions. According to the docking poses, hydrophobic interactions and hydrogen bond variations define the main regions of important amino acids in integrase. In addition to the detection of TCM compound efficacy, we suggest (1S,2S)-norpseudoephedrine is better than the others based on the analysis of interaction and the effect on the structural variation.

Lead Screening for Chronic Obstructive Pulmonary Disease of IKK2 Inhibited by Traditional Chinese Medicine

Chronic obstructive pulmonary disease (COPD) is a chronic obstructive lung disease and is frequently found in well-developed countries due to the issue of aging populations. Not all forms of medical treatment are unable to return a patient's limited pulmonary function back to normal and eventually they could require a lung transplant. At this time, COPD is the leading cause of death in the world. Studies surveying I-kappa-B-kinase beta (IKK2) are very relevant to the occurrence and deterioration of the condition COPD. The sinapic acid-4-O-sulfate, kaempferol, and alpha-terpineol were found to be IKK2 inhibitors and helped prevent COPD occurrence and worsening according to a screening of the traditional Chinese medicine (TCM) database. The protein-ligand interaction of these three compounds with regard to IKK2 was also done by molecular dynamics. The docking poses, hydrogen bond variation, and hydrophobic interactions found Asp103 and Lys106 are crucial to IKK2 binding areas for IKK2 inhibition. Finally, we found the three compounds that have an equally strong effect in terms of IKK2 binding proven by the TCM database and perhaps these may be an alternative treatment for COPD in the future.

In Silico Investigation of Potential PARP-1 Inhibitors from Traditional Chinese Medicine

Poly(ADP-ribose) polymerases (PARPs) are nuclear enzymes which catalyze the poly-ADP-ribosylation involved in gene transcription, DNA damage repair, and cell-death signaling. As PARP-1 protein contains a DNA-binding domain, which can bind to DNA strand breaks and repair the damaged DNA over a low basal level, the inhibitors of poly(ADP-ribose) polymerase 1 (PARP-1) have been indicated as the agents treated for cancer. This study employed the compounds from TCM Database@Taiwan to identify the potential PARP-1 inhibitors from the vast repertoire of TCM compounds. The binding affinities of the potential TCM compounds were also predicted utilized several distinct scoring functions. Molecular dynamics simulations were performed to optimize the result of docking simulation and analyze the stability of interactions between protein and ligand. The top TCM candidates, isopraeroside IV, picrasidine M, and aurantiamide acetate, had higher potent binding affinities than control, A927929. They have stable H-bonds with residues Gly202 and, Ser243 as A927929 and stable H-bonds with residues Asp105, Tyr228, and His248 in the other side of the binding domain, which may strengthen and stabilize ligand inside the binding domain of PARP-1 protein. Hence, we propose isopraeroside IV and aurantiamide acetate as potential lead compounds for further study in drug development process with the PARP-1 protein.

Treatment of acute lymphoblastic leukemia from traditional chinese medicine

Acute lymphoblastic leukemia (ALL) is a cancer that immature white blood cells continuously overproduce in the bone marrow. These cells crowd out normal cells in the bone marrow bringing damage and death. Methotrexate (MTX) is a drug used in the treatment of various cancer and autoimmune diseases. In particular, for the treatment of childhood acute lymphoblastic leukemia, it had significant effect. MTX competitively inhibits dihydrofolate reductase (DHFR), an enzyme that participates in the tetrahydrofolate synthesis so as to inhibit purine synthesis. In addition, its downstream metabolite methotrexate polyglutamates (MTX-PGs) inhibit the thymidylate synthase (TS). Therefore, MTX can inhibit the synthesis of DNA. However, MTX has cytotoxicity and neurotoxin may cause multiple organ injury and is potentially lethal. Thus, the lower toxicity drugs are necessary to be developed. Recently, diseases treatments with Traditional Chinese Medicine (TCM) as complements are getting more and more attention. In this study, we attempted to discover the compounds with drug-like potential for ALL treatment from the components in TCM. We applied virtual screen and QSAR models based on structure-based and ligand-based studies to identify the potential TCM component compounds. Our results show that the TCM compounds adenosine triphosphate, manninotriose, raffinose, and stachyose could have potential to improve the side effects of MTX for ALL treatment.

Lead Screening for HIV of C-C Chemokine Receptor Type 5 Receptor Inhibited by Traditional Chinese Medicine

The acquired immunodeficiency syndrome (AIDS), caused by the human immunodeficiency virus (HIV), has become a serious world-wide problem because of this disease's rapid propagation and incurability. Recent research has pointed out that the C-C chemokine receptor type 5 (CCR5) is an important target for HIV infection. The traditional Chinese medicine (TCM) database (http://tcm.cmu.edu.tw/) has been screened for molecular compounds that, by simulating molecular docking and molecular dynamics, may protect CCR5 against HIV. Saussureamine C, 5-hydroxy-L-tryptophan, and abrine are selected based on the docking score being higher than Maraviroc and other TCM compounds. The molecular dynamics are helpful in the analysis and detection of protein-ligand interactions. According to the docking poses, hydrophobic interactions, and hydrogen bond variations, this research surmises TRP86, TYR108, GLN194, TYR251, and GLU283 are the main regions of important amino acids in CCR5. In addition to the detection of TCM compound efficacy, we suggest saussureamine C is better than the others for maintaining protein composition during protein-ligand interaction, based on the structural variation.

Potential retinoid x receptor agonists for treating Alzheimer's disease from traditional chinese medicine

Alzheimer's disease is neurodegenerative disorder due to the accumulation of amyloid-β in the brain and causes dementia with ageing. Some researches indicate that the RXR agonist, Targretin, has also been used for treatment of Alzheimer's disease in mouse models. We investigate the potent candidates as RXR agonists from the vast repertoire of TCM compounds in TCM Database@Taiwan. The potential TCM compounds, β-lipoic acid and sulfanilic acid, had higher potent binding affinities than both 9-cis-retinoic acid and Targretin in docking simulation and have stable H-bonds with residues Arg316 and some equivalent hydrophobic contacts with residues Ala272, Gln275, Leu309, Phe313, Val342, Ile345, and Cys432 as Targretin. The carboxyl or sulfonyl hydroxide group can form a H-bond with key residue Arg316 in the docking pose, and the phenyl group next to the carboxyl or sulfonyl hydroxide group can form a π interaction with residue Phe313. Moreover, β-lipoic acid and sulfanilic acid have stable H-bonds with residue Gln275, Ser313, and residue Ala327, respectively, which may strengthen and stabilize TCM candidates inside the binding domain of RXR protein. Hence, we propose β-lipoic acid and sulfanilic acid as potential lead compounds for further study in drug development process with the RXR protein against Alzheimer's disease.

Investigation of anti-infection mechanism of lactoferricin and splunc-1

The innate immune system is the first line in the defense system and prevents the body from further bacteria, virus, or fungal infections. Most of the innate immune system is relevant to mucosa immunity. Lactotransferrin is secreted from the human mammal breast duct epithelial tissue and strengthens infant immunity to defense with regard to outward pathogens. Splunc-1 is also an innate material secreted from the soft palate, lung, nasal cavity epithelium, and mucosa. It helps with mucosa defense against bacterial, virus, and even fungus. LPS is the main etiology of Gram-negative bacilla infection source. And studies of lactoferricin and slpunc-1 both can combine with LPS and subsequently cause insults to the mucosa. Although, we know that both of them partake in an important role in innate immunity, we do not know the effects when they work together. In this study, we just overview silicon stimulation to examine the combination of Lactoferricin and Splunc-1 and the effect with regard to LPS.

A new insight into mushroom tyrosinase inhibitors: docking, pharmacophore-based virtual screening, and molecular modeling studies

Tyrosinase, a widely spread enzyme in micro-organisms, animals, and plants, participates in two rate-limiting steps in melanin formation pathway which is responsible for skin protection against UV lights' harm whose functional deficiency result in serious dermatological diseases. This enzyme seems to be responsible for neuromelanin formation in human brain as well. In plants, the enzyme leads the browning pathway which is commonly observed in injured tissues that is economically very unfavorable. Among different types of tyrosinase, mushroom tyrosinase has the highest homology with the mammalian tyrosinase and the only commercial tyrosinase available. In this study, ligand-based pharmacophore drug discovery method was applied to rapidly identify mushroom tyrosinase enzyme inhibitors using virtual screening. The model pharmacophore of essential interactions was developed and refined studying already experimentally discovered potent inhibitors employing Docking analysis methodology. After pharmacophore virtual screening and binding modes prediction, 14 compounds from ZINC database were identified as potent inhibitors of mushroom tyrosinase which were classified into five groups according to their chemical structures. The inhibition behavior of the discovered compounds was further studied through Classical Molecular Dynamic Simulations and the conformational changes induced by the presence of the studied ligands were discussed and compared to those of the substrate, tyrosine. According to the obtained results, five novel leads are introduced to be further optimized or directly used as potent inhibitors of mushroom tyrosinase.

In SilicoInvestigation of Cytochrome P450 2C9 in relation to Aging Using Traditional Chinese Medicine

Cytochrome P450 2C9 (CYP2C9) metabolizes dehydroepiandrosterone-sulfate (DHEA-S), but in elderly people the amount of DHEA-S remaining after CYP2C9 metabolization may be insufficient for optimal health. A prediction model, molecular docking, and molecular dynamics were used to screen the Traditional Chinese Medicine (TCM) database to determine molecular compounds that may inhibit CYP2C9. The candidate compounds apocynoside(I), 4-methoxymagndialdehyde, and prunasin have higher Dock Scores, and prediction bioactivity than warfarin (the control drug). The interaction between 4-methoxymagndialdehyde and CYP2C9 is more intense than with other TCM compounds, but the simulation is longer. In these compounds, apocynoside(I) and prunasin have a greater number of pathways for their flexible structure, but these structures create weak interactions. These candidate compounds, which are known to have antioxidation and hypolipidemic functions that have an indirect effect on the aging process, can be extracted from traditional Chinese medicines. Thus, these candidate compounds may become CYP2C9 inhibitors and play an important role in providing optimal health in the elderly.

A possible strategy against head and neck cancer: in silico investigation of three-in-one inhibitors

Overexpression of epidermal growth factor receptor (EGFR), Her2, and uroporphyrinogen decarboxylase (UROD) occurs in a variety of malignant tumor tissues. UROD has potential to modulate tumor response of radiotherapy for head and neck cancer, and EGFR and Her2 are common drug targets for the treatment of head and neck cancer. This study attempts to find a possible lead compound backbone from TCM Database@Taiwan ( http://tcm.cmu.edu.tw/ ) for EGFR, Her2, and UROD proteins against head and neck cancer using computational techniques. Possible traditional Chinese medicine (TCM) lead compounds had potential binding affinities with EGFR, Her2, and UROD proteins. The candidates formed stable interactions with residues Arg803, Thr854 in EGFR, residues Thr862, Asp863 in Her2 protein, and residues Arg37, Arg41 in UROD protein, which are key residues in the binding or catalytic domain of EGFR, Her2, and UROD proteins. Thus, the TCM candidates indicated a possible molecule backbone for evolving potential inhibitors for three drug target proteins against head and neck cancer.

Inhibition of protein-protein interaction of HER2-EGFR and HER2-HER3 by a rationally designed peptidomimetic

Protein-protein interactions (PPI) play a crucial role in many biological processes and modulation of PPI using small molecules to target hot spots has therapeutic value. As a model system we will use PPI of human epidermal growth factor receptors (EGFRs). Among the four EGFRs, EGFR-HER2 and HER2-HER3 are well known in cancer. We have designed a small molecule that is targeted to modulate HER2-mediated signaling. Our approach is novel because the small molecule designed disrupts dimerization not only of EGFR-HER2, but also of HER2-HER3. In the present study we have shown, using surface plasmon resonance analysis, that a peptidomimetic, compound 5, binds specifically to HER2 protein extracellular domain and disrupts the dimerization of EGFRs. To evaluate the effect of compound 5 on HER2 signaling in vitro, Western blot and PathHunter assays were used. Results indicated that compound 5 inhibits the phosphorylation of HER2 kinase domain and inhibits the heterodimerization in a dose-dependent manner. Molecular modeling methods were used to model the PPI of HER2-HER3 heterodimer.

Traditional Chinese medicine as dual guardians against hypertension and cancer?

This study utilizes the comprehensive traditional Chinese medicine database TCM Database@Taiwan ( http://tcm.cmu.edu.tw/ ) in conjunction with structure-based and ligand-based drug design to identify multi-function Src inhibitors. The three potential TCM candidates identified as having suitable docking conformations and bioactivity profiles were Angeliferulate, (3R)-2'-hydroxy-3',4'-dimethoxyisoflavan-7-O-beta-D-glucoside (HMID), and 3-[2',6-dihydroxy-5'-(2-propenyl)[1,1'-biphenyl]3-yl]-(E)-2-propenoic acid (3PA). Molecular dynamics simulation demonstrated that the TCM candidates have more stable interactions with the cleft and in complex with Src kinase compared to Saracatinib. Angeliferulate and HMID, both originated from Angelica sinensis, not only interact with Lys298 and amino acids from different loops in the cleft, but also with Asp407 located on the activation loop. These interactions are important to reduce the opening of the activation loop due to phosphorylation, hence stabilize the Src kinase cleft structure and inhibit activation. The TCM candidates also exhibited high affinity to other cancer-related target proteins (EGFR, HER2, and HSP90). Our observations suggest that the TCM candidates might have multi-targeting effects in hypertension and cancer.

Biological evaluation and interaction of a newly designed anti-cancer Pd(II) complex and human serum albumin

The pharmacokinetics and pharmacodynamics of any drug will depend, largely, on the interaction that has with human serum albumin (HSA), the most abundant plasma protein. The interaction between newly synthesized Pd(II) complexe, 2,2'-bipyridin Butylglycinato Pd(II) nitrate, an anti-tumor component, with HSA was studied at different temperatures by fluorescence, far UV circular dichroism (CD), UV-visible spectrophotometry and theoretical approaches. The Pd(II) complex has a strong ability to quench the intrinsic fluorescence of HSA through a dynamic quenching procedure. The binding parameters and thermodynamic parameters, including δH°, δS° and δG° were calculated by fluorescence quenching method, indicated that hydrophobic forces play a major role in the interaction of Pd(II) complex with HSA. Based on Autodock, FRET (fluorescence resonance energy transfer) and fluorescence quenching data, it may be concluded that one of the binding sites in the complex of HSA is near the only one Trp of HSA (Trp214) in sub domain IIA of the protein. Far-UV-CD results indicated that Pd(II)-complex induced increase in the α-helical content of the protein. The anti-tumor property of the synthesized Pd(II) complex was studied by testing it on human tumor cell line K562. The 50% cytotoxic concentration (Cc₅₀) of complex was determined using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Also, fluorescence staining with DAPI (4,6-diamidino-2-phenylindole) revealed some typical nuclear changes that are characteristic of apoptosis which is induced at Cc₅₀ concentration of Pd(II) complex in K562 cell line after 24 h incubation. Our results suggest that Pd(II) complex is a promising anti-proliferative agent and should execute its biological effects by inducing apoptosis.

Search for novel remedies to augment radiation resistance of inhabitants of Fukushima and Chernobyl disasters: identifying DNA repair protein XRCC4 inhibitors

Two nuclear plant disasters occurring within a span of 25 years threaten health and genome integrity both in Fukushima and Chernobyl. Search for remedies capable of enhancing DNA repair efficiency and radiation resistance in humans appears to be a urgent problem for now. XRCC4 is an important enhancer in promoting repair pathway triggered by DNA double-strand break (DSB). In the context of radiation therapy, active XRCC4 could reduce DSB-mediated apoptotic effect on cancer cells. Hence, developing XRCC4 inhibitors could possibly enhance radiotherapy outcomes. In this study, we screened traditional Chinese medicine (TCM) database, TCM Database@Taiwan, and have identified three potent inhibitor agents against XRCC4. Through molecular dynamics simulation, we have determined that the protein-ligand interactions were focused at Lys188 on chain A and Lys187 on chain B. Intriguingly, the hydrogen bonds for all three ligands fluctuated frequently but were held at close approximation. The pi-cation interactions and ionic interactions mediated by o-hydroxyphenyl and carboxyl functional groups respectively have been demonstrated to play critical roles in stabilizing binding conformations. Based on these results, we reported the identification of potential radiotherapy enhancers from TCM. We further characterized the key binding elements for inhibiting the XRCC4 activities.

Identifying HER2 inhibitors from natural products database

The relationship between abnormal HER2 expression and cancer is important in cancer therapeutics. Formation and spread of cancer cells may be restricted by inhibiting HER2. We conducted ligand-based and structure-based studies to assess the potency of natural compounds as potential HER2 inhibitors. Multiple linear regression (MLR) and support vector machine (SVM) models were constructed to predict biological activities of natural compounds, and molecular dynamics (MD) was used to assess their stability with HER2 under a dynamic environment. Predicted bioactivities of the natural compounds ranged from 6.014–9.077 using MLR (r² = 0.7954) and 5.122–6.950 using SVM (r² = 0.8620). Both models were in agreement and suggest bioactivity based on candidate structure. Conformation changes caused by MD favored the formation of stabilizing H-bonds. All candidates had higher stability than Lapinatib, which may be due to the number and spatial distribution of additional H-bonds and hydrophobic interactions. Amino acids Lys724 and Lys736 are critical for binding in HER2, and Thr798, Cys805, and Asp808 are also important for increased stability. Candidates may block the entrance to the ATP binding site located within the inner regions and prevent downstream activation of HER2. Our multidirectional approach indicates that the natural compounds have good ligand efficacy in addition to stable binding affinities to HER2, and should be potent candidates of HER2 inhibitors. With regard to drug design, designing HER2 inhibitors with carboxyl or carbonyl groups available for H-bond formation with Lys724 and Lys736, and benzene groups for hydrophobic contact with Cys805 may improve protein-ligand stability.

Molecular dynamics and docking studies on cardiac troponin C

Cardiac troponin C (cTnC) is the Ca²⁺ dependent switch for contraction in heart muscle making it a potential target for drug research in the therapy of heart failure. Calcium binding on Troponin C (TnC) triggers a series of conformational changes exposing a hydrophobic pocket in the N-domain of TnC (cNTnC), which leads to force generation. Mutations and acidic pH have been related to altering the sensitivity of TnC affecting the efficiency of the heart. Bepridil, identified as a calcium sensitizer to TnC, has been experimentally found to bind to the N-domain pocket of TnC but with negative cooperativity. Screening and de novo design were carried out using LUDI and AUTOLUDI programs in this work to identify and design potential ligands that can bind to the hydrophobic pocket of TnC. Two docking centers and multiple searching radii including 5 Å, 5.5 Å, 6 Å, 6.5 Å, 7.0 Å and 7.5 Å were used in LUDI to screen the ZINC database. Based on the LUDI docking results, 8 molecules were identified from the database with good potential to bind into the binding pocket and they were used as template molecules to generate a series of new molecules by AUTOLUDI design. Out of all the newly-designed molecules, 14 new ligands were recognized to be potential ligands that can bind and fit well into the binding pocket. These molecules can be used as starting molecules to develop TnC ligands. The binding stability and binding affinity of these molecules to the protein was further analyzed by molecular dynamics simulations. The results show that the binding energies, interactions and complex stabilities of 6 ligands are comparable to or better than bepridil.

Biphasic association of T7 RNA polymerase and a nucleotide analogue, cibacron blue as a model to understand the role of initiating nucleotide in the mechanism of enzyme action

T7 RNA polymerase (T7 RNAP) is an enzyme that utilizes ribonucleotides to synthesize the nascent RNA chain in a template-dependent manner. Here we have studied the interaction of T7 RNAP with cibacron blue, an anthraquinone monochlorotriazine dye, its effect on the function of the enzyme and the probable mode of binding of the dye. We have used difference absorption spectroscopy and isothermal titration calorimetry to show that the dye binds T7 RNAP in a biphasic manner. The first phase of the binding is characterized by inactivation of the enzyme. The second binding site overlaps with the common substrate-binding site of the enzyme. We have carried out docking experiment to map the binding site of the dye in the promoter bound protein. Competitive displacement of the dye from the high affinity site by labeled GTP and isothermal titration calorimetry of high affinity GTP bound enzyme with the dye suggests a strong correlation between the high affinity dye binding and the high affinity GTP binding in T7 RNAP reported earlier from our laboratory.

High performance screening, structural and molecular dynamics analysis to identify H1 inhibitors from TCM Database@Taiwan

New-type oseltamivir-resistant H1N1 influenza viruses have been a major threat to human health since the 2009 flu pandemic. To resolve the drug resistance issue, we aimed to identify a new type of inhibitors against H1 from traditional Chinese medicine (TCM) by employing the world's largest TCM database () for virtual screening and molecular dynamics (MD). From the virtual screening results, sodium (+)-isolaricireinol-2 alpha-sulfate, sodium 3,4-dihydroxy-5-methoxybenzoic acid methyl ester-4-sulfate, sodium (E)-7-hydroxy-1,7-bis(4-hydroxyphenyl)hept-5-ene-3S-sulfonate, and 3-methoxytyramine-betaxanthin were identified as potential drug-like compounds. MD simulation of the binding poses with the key residues Asp103 and Glu83, as well as other binding site residues, identified higher numbers of hydrogen bonds than N-Acetyl-D-Glucosamine (NAG), the natural ligand of the esterase domain in H1. Ionic bonds, salt bridges, and electrostatic energy also contribute to binding stability. Key binding residues include Lys71, Glu83, Asp103, and Arg238. Structural moieties promoting H-bond or salt bridge formations at these locations greatly contribute to a stable ligand-protein complex. An available sodium atom for ionic interactions with Asp103 can further stabilize the ligands. Based on virtual screening, MD simulation, and interaction energy evaluation, TCM candidates demonstrate good potential as novel H1 inhibitors. In addition, the identified stabilizing features can provide insights for designing highly stable H1 inhibitors.

In search of allosteric modulators of a7-nAChR by solvent density guided virtual screening

Nicotinic acetylcholine receptors (nAChR) are pentameric ligand gated ion channels whose activity can be modulated by endogenous neurotransmitters as well as by synthetic ligands that bind the same or distinct sites from the natural ligand. The subtype of α7 nAChR has been considered as a potenial therapeutic target for Alzheimer's disease, schizophrenia and other neurological and psychiatric disorders. Here we have developed a homology model of α7 nAChR based on two high resolution crystal structures with Brookhaven Protein Data Bank (PDB) codes 2QC1 and 2WN9 for threading on one monomer and then for building a pentamer, respectively. A number of small molecule binding sites are identified using Pocket Finder (J. An, M. Tortov, and R. Abagyan, Molecular & Cellular Proteomics, 4.6, 752-761 (2005)) of Internal Coordinate Mechanics (ICM). Remarkably, these computer-identified sites match perfectly with ordered solvent densities found in the high-resolution crystal structure of α1 nAChR, suggesting that the surface cavities in the α7 nAChR model are likely binding sites of small molecules. A high throughput virtual screening by flexible ligand docking of 5008 small molecule compounds was performed at three potential allosteric modulator (AM) binding sites of α7 nAChR using Molsoft ICM software (R. Abagyan, M. Tortov and D. Kuznetsov, J Comput Chem 15, 488-506, (1994)). Some experimentally verified allosteric modulators of α7 like CCMI comp-6, LY 7082101, 5-HI, TQS, PNU-120596, genistein, and NS-1738 ranked among top 100 compounds, while the rest of the compounds in the list could guide further search for new allosteric modulators.

Screening from the world's largest TCM database against H1N1 virus

The swine influenza virus (H1N1) 2009 pandemic highlights the importance of having effective anti-viral strategies. Recently, oseltamivir (Tamiflu) resistant influenza viruses are identified; which further emphasizes the urgency in developing new antiviral agents. In influenza virus replication cycle, viral surface glycoprotein, hemagglutinin, is responsible for viral entry into host cells. Hence, a potentially effective antiviral strategy is to inhibit viral entry mechanism. To develop novel antiviral agent that inhibits viral entry, we analyzed 20,000 traditional Chinese medicine (TCM) ingredients in hemagglutinin subtype H1 sialic acid binding site found on H1N1 virus. We then performed molecular dynamics simulations to investigate receptor-ligand interaction of the candidates obtained from docking. Here, we report three TCM derivatives that have high binding affinities to H1 sialic acid binding site residues based on structure-based calculations. The top three derivatives, xylopine_2, rosmaricine_14 and rosmaricine_15, all have an amine group that interact with Glu83 and a pyridinium group that interact with Asp103. Molecular dynamics simulations show that these derivatives form strong hydrogen bonding with Glu83 but interact transiently with Asp103. We therefore suggest that an enhanced hemagglutinin inhibitor, based on our scaffold, should be designed to bind both Glu83 and Asp103 with high affinity.

Identification of potent EGFR inhibitors from TCM Database@Taiwan

Overexpression of epidermal growth factor receptor (EGFR) has been associated with cancer. Targeted inhibition of the EGFR pathway has been shown to limit proliferation of cancerous cells. Hence, we employed Traditional Chinese Medicine Database (TCM Database@Taiwan) (http://tcm.cmu.edu.tw) to identify potential EGFR inhibitor. Multiple Linear Regression (MLR), Support Vector Machine (SVM), Comparative Molecular Field Analysis (CoMFA), and Comparative Molecular Similarities Indices Analysis (CoMSIA) models were generated using a training set of EGFR ligands of known inhibitory activities. The top four TCM candidates based on DockScore were 2-O-caffeoyl tartaric acid, Emitine, Rosmaricine, and 2-O-feruloyl tartaric acid, and all had higher binding affinities than the control Iressa®. The TCM candidates had interactions with Asp855, Lys716, and Lys728, all which are residues of the protein kinase binding site. Validated MLR (r² = 0.7858) and SVM (r² = 0.8754) models predicted good bioactivity for the TCM candidates. In addition, the TCM candidates contoured well to the 3D-Quantitative Structure-Activity Relationship (3D-QSAR) map derived from the CoMFA (q² = 0.721, r² = 0.986) and CoMSIA (q² = 0.662, r² = 0.988) models. The steric field, hydrophobic field, and H-bond of the 3D-QSAR map were well matched by each TCM candidate. Molecular docking indicated that all TCM candidates formed H-bonds within the EGFR protein kinase domain. Based on the different structures, H-bonds were formed at either Asp855 or Lys716/Lys728. The compounds remained stable throughout molecular dynamics (MD) simulation. Based on the results of this study, 2-O-caffeoyl tartaric acid, Emitine, Rosmaricine, and 2-O-feruloyl tartaric acid are suggested to be potential EGFR inhibitors.

Investigation into potent inflammation inhibitors from traditional Chinese medicine

Microsomal prostaglandin E synthase-1 (mPGES-1) is the key enzyme for prostaglandin E2 (PGE2) generation during inflammation and is a potential target for designing anti-inflammatory drugs. Potential inhibitors of m-PGES-1 were selected from traditional Chinese medicine (TCM Database@Taiwan) based on the pharmacophore map generated by the top HypoGen hypothesis and validated using structure- and ligand-based analysis. Key features for potential m-PGES-1 inhibitors include pi-interactions and H-bond donors. TCM compounds, shanciol B, shanciol A, castilliferol, and aurantiamide acetate, contoured to the quantitative structure-activity relationship pharmacophore and exhibited high docking scores and binding stability with m-PGES-1. Bioactivity models multiple linear regression (MLR) and support vector machine also supported activity predictions for the candidate compounds. Our results indicate that the investigated TCM compounds could be of use for development into mPGES-1 inhibitors.