Design, Synthesis, and Biological Studies of Flavone-Based Esters and Acids as Potential P450 2A6 Inhibitors

As a potential means for smoking cessation and consequently prevention of smoking-related diseases and mortality, in this study, our goal was to investigate the inhibition of nicotine metabolism by P450 2A6. Smoking is the main cause of many diseases and disabilities and harms nearly every organ of the body. As reported by the Centers for Disease Control and Prevention (CDC), more than 16 million Americans are living with diseases caused by smoking. On average, the life expectancy of a smoker is about 10 years less than a nonsmoker. Smoking cessation can substantially reduce the incidence of smoking-related diseases, including cancer. At least, 70 of the more than 7000 cigarette smoke components, including polycyclic aromatic hydrocarbons, N-nitrosamines, and aromatic amines, are known carcinogens. Nicotine is the compound responsible for the addictive and psychopharmacological effects of tobacco. Cytochrome P450 enzymes are responsible for the phase I metabolism of many tobacco components, including nicotine. Nicotine is mainly metabolized by cytochrome P450s 2A6 and 2A13 to cotinine. This metabolism decreases the amount of available nicotine in the bloodstream, leading to increased smoking behavior and thus exposure to tobacco toxicants and carcinogens. Here, we report the syntheses and P450 2A6 inhibitory activities of a number of new flavone-based esters and acids. Three of the flavone derivatives studied were found to be potent competitive inhibitors of the enzyme. Docking studies were used to determine the possible mechanisms of the activity of these inhibitors.

Study of Ceramide-Flavone Analogs Showing Self-Fluorescence and Anti-Proliferation Activities

Background

Many current anti-cancer drugs used to treat breast cancer mediate tumor cell death through the induction of apoptosis. Cancer cells, however, often acquire multidrug-resistance following prolonged exposure to chemotherapeutics. Consequently, molecular pathways involved in tumor cell proliferation have become potential targets for pharmacological intervention. Ceramides are tumor suppressor lipids naturally found in the cell membrane, and are central molecules in the sphingolipid signalling pathway.

Methods

Our lab has targeted the ceramide signaling pathway for potential pharmacological intervention in the treatment of breast cancer. Previously, we have shown that certain ceramide analogs have therapeutic potential in the treatment of chemo-sensitive and multidrug-resistant breast cancers. Using the most active analog from our previous studies as the lead compound, new analogs containing a flavone moiety were designed and synthesized. In general, flavone derivatives often show interesting pharmacological properties, and compounds based on these molecules have been found useful in many different therapeutic areas including anti-tumor, anti-coagulants, and anti-HIV therapy.

Results

Synthesis and biological evaluation of five new flavonoid ceramide analogs are reported here. These compounds were also shown to be self-fluorescent, which can be useful when investigating their distribution and action in cancer cells.

Conclusion

Four out of the five flavone ceramide analogs in this study showed significant anti-proliferation activities in the three cell lines studied, MDA-MB-232, MCF-7, and MCF-7TN-R; some showing varying degrees of selectivity. The mechanisms involved in cell proliferation inhibition are complicated and further studies are needed.

Enabling internet of things in road traffic forecasting with deep learning models

Integration of the latest technological advancements such as Internet of Things (IoT) and Computational Intelligence (CI) techniques is an active research area for various industrial applications. The rapid urbanization and exponential growth of vehicles has led to crowded traffic in cities. The deployment of IoT infrastructures for building smart and intelligent traffic management system greatly improves the quality and comfort of city dwellers. This work aims at building a cost effective IoT enabled traffic forecasting system using deep learning techniques. The case study experimentation is done in a real time traffic environment. The main contributions of this work include: (i) deploying road side sensor station built with ultrasonic sensor and Arduino Uno controller for obtaining traffic flow data (ii) building an IoT cloud system based on open source Thingspeak cloud platform for monitoring real time traffic (iii) performing short term traffic forecast using Recurrent Neural Network (RNN) models such as Long Short Term Memory (LSTM) and Gated Recurrent Unit (GRU). The performance of the prediction model is compared with the traditional statistical methods such as Autoregressive Integrated Moving Average (ARIMA), Seasonal ARIMA (SARIMA) and Convolutional Neural Network (CNN). The results show good performance metrics with RMSE of 5.8, 7.9, 10.2 for LSTM model and 6.7, 8.6, 10.9 for GRU model for three different scenarios such as whole day, morning congested hour and evening congested hour datasets.

Abstract 343: New derivatives of 1,3-dioxoisoindoline: Potential breast cancer therapeutics that are S6K1 inhibitors

Currently, more than 3.8 million women in the United States are diagnosed with breast cancer which is the second leading cause of cancer-related death in women. The correlation of the ribosomal protein S6 kinase 1 (S6K1) activity and breast cancer is evident from the amplification of S6K1 localized chromosomal region 17q23 in 20% of primary breast cancers. S6K1 is a conserved serine/threonine protein kinase, is the principal kinase effector downstream of the PI3K/mTOR regulatory signaling pathway. Over-expression of S6K1 has been associated with cell transformation and elevated proliferation rates in tumors, poor prognosis and an increased risk of local recurrence. S6K1 has been found to play an important role in the progression of ER-positive (ER+) breast cancer, HER2 positive (HER2+) breast cancer and node-negative premenopausal breast cancer. Inhibition of this kinase can prove to be beneficial for the treatment of several types of breast cancer. Our group has identified new molecules that are derivatives of 6-amido-4-aminoisoindoline-1,3-dione core structure as S6K1 inhibitors with low micromolar inhibition potency (IC50 = 2-5 μM). These compounds also inhibited the growth of HER2+ (SKBR3 and HER2Δ16), ER+ and triple negative breast cancer cells (MDA-MB-231 and MDA-MB-468) with a range of EC50 values (2 - 2000 μM). The EC50 values of growth inhibition of these compounds varied by the type of breast cancer cells and were in direct correlation with the expression levels of S6K1 in those cell lines. These results clearly indicate that high efficacy S6K1 inhibitors can function as potential therapeutics for multiple types of breast cancer. Future work involves in-vivo studies to understand the efficacy and pharmacokinetics of the three compounds.

Citation Format: Satyendra Kumar, Rajesh Komati, Shahensha Shaik, Melyssa Bratton, Linh Tran, Rion Sam, Elijah Johnson-Henderson, Breyanah Graham, Christopher WIlliams, Jayalakshmi Sridhar. New derivatives of 1,3-dioxoisoindoline: Potential breast cancer therapeutics that are S6K1 inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 343.

Identification of CYP 2A6 inhibitors in an effort to mitigate the harmful effects of the phytochemical nicotine

AIM

In this study, our goal was to study the inhibition of nicotine metabolism by P450 2A6, as a means for reduction in tobacco use and consequently the prevention of smoking-related cancers. Nicotine, a phytochemical, is an addictive stimulant, responsible for the tobacco-dependence in smokers. Many of the other phytochemicals in tobacco, including polycyclic aromatic hydrocarbons, N-nitrosamines, and aromatic amines, are potent systemic carcinogens. Tobacco smoking causes about one of every five deaths in the United States annually. Nicotine plasma concentration is maintained by the smokers' smoking behavior within a small range. Nicotine is metabolized by cytochrome P450s 2A6 and 2A13 to cotinine. This metabolism causes a decrease in nicotine plasma levels, which in turn leads to increased tobacco smoking, and increased exposure to the tobacco carcinogens.

METHODS

Using the phytochemical nicotine as a lead structure, and taking its interactions with the P450 2A6 binding pocket into consideration, new pyridine derivatives were designed and synthesized as potential selective mechanism-based inhibitors for this enzyme.

RESULTS

The design and synthesis of two series of novel pyridine-based compounds, with varying substituents and substitution locations on the pyridine ring, as well as their inhibitory activities on cytochrome P450 2A6 and their interactions with its active site are discussed here. Substitutions at position 3 of the pyridine ring with an imidazole or propargyl ether containing group showed the most optimal interactions with the P4502A6 active site.

CONCLUSION

The pyridine compounds with an imidazole or propargyl ether containing substituent on position 3 were found to be promising lead compounds for further development. Hydrogen-bonding interactions were determined to be crucial for effective binding of these molecules within the P450 2A6 active site.

Abstract 6360: Development of a new substituted 1,3-dioxoisoindoline series that are RPS6K1 protein kinase inhibitors as potential cancer therapeutics

The 40S ribosomal S6 kinase 1 (S6K1), a conserved serine/threonine protein kinase, is the principal kinase effector downstream of the PI3K/mTOR regulatory signaling pathway. Over-expression of RPS6K1 has been associated with cell transformation and elevated proliferation rates in tumors, poor prognosis and an increased risk of local recurrence. RPS6K1 has been found to play an important role in the progression of ER-positive breast cancer, HER2 positive breast cancer and node-negative premenopausal breast cancer. Overexpression of RPS6K1 is closely correlated with aggressive progression and poor prognosis in prostate cancer patients. Inhibition of this kinase can prove to be beneficial for the treatment of several types of cancer including breast cancer, prostate cancer, non-small cell lung cancer, etc. Our laboratory has identified 7-amino-5-amido-1,3-dioxoisoindolines as S6K1 inhibitors with low micromolar IC50 values (2-5 μM). These compounds also inhibited the growth of prostate cancer cells DU-145 and breast cancer cells MCF-7 (ER-positive) and SKBR3 (HER2-positive). The IC50 values of growth inhibition of SKBR3 breast cancer cell lines by the compounds RJ19, RJ22 and RJ28 are 3.3, 1.9 and 4.7 μM, respectively. The core structure 5,7-diamino-1,3-dioxoisoindoline was found to selectively inhibit RPS6K1 over 99 other oncologic protein kinases. This series of compounds have the potential to become viable therapeutics for many types of cancer. The results from the synthesis of 7-amino-5-amido-1,3-dioxoisoindoline derivatives, the structure activity studies, and their efficacy studies will be presented.

Citation Format: Jayalakshmi Sridhar, Rajesh Komati, Melyssa Bratton. Development of a new substituted 1,3-dioxoisoindoline series that are RPS6K1 protein kinase inhibitors as potential cancer therapeutics [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6360.

Identification of New Mono/Dihydroxynaphthoquinone as Lead Agents That Inhibit the Growth of Refractive and Triple-Negative Breast Cancer Cell Lines

Human epidermal growth factor receptor 2 (HER2) is overexpressed in nearly 20-30% of breast cancers and is associated with metastasis resulting in poor patient survival and high recurrence. The dual EGFR/HER2 kinase inhibitor lapatinib has shown promising clinical results, but its limitations have also led to the resistance and activation of tumor survival pathways. Following our previous investigation of quinones as HER2 kinase inhibitors, we synthesized several naphthoquinone derivatives that significantly inhibited breast tumor cells expressing HER2 and trastuzumab-resistant HER2 oncogenic isoform, HER2Δ16. Two of these compounds were shown to be more effective than lapatinib at the inhibition of HER2 autophosphorylation of Y1248. Compounds 7 (5,8-dihydroxy-2-methylnaphthalene-1,4-dione) and 9 (2-(bromomethyl)-5,8-dihydroxynaphthalene-1,4-dione) inhibited HER2-expressing MCF-7 cells (IC50 0.29 and 1.76 μM, respectively) and HER2Δ16-expressing MCF-7 cells (IC50 0.51 and 1.76 μM, respectively). Compound 7 was also shown to promote cell death in multiple refractory breast cancer cell lines with IC50 values ranging from 0.12 to 2.92 μM. These compounds can function as lead compounds for the design of a new series of nonquinonoid structural compounds that can maintain a similar inhibition profile.

Microbial biopesticides for insect pest management in India: Current status and future prospects

The biopesticide industry in India is undergoing rapid change, reflecting increased global trade in agricultural commodities, a changing regulatory environment and evolving consumer preferences. Currently biopesticides comprise ≈ 5% of the Indian pesticide market, with at least 15 microbial species and 970 microbial formulations registered through the Central Insecticides Board and Registration Committee (CIBRC). As of 2017, over 200 products based on entomopathogenic fungi (Beauveria bassiana, B. brongniartii, Metarhizium anisopliae s.l., Lecanicillium lecanii and Hirsutella thompsonii) and nematicidal fungi (Purpureocillium lilacinum and Pochonia chlamydosporia) are registered for use against various arthropods and plant parasitic nematodes. Regarding bacteria, over 30 products based on Bacillus thuringiensis (Bt) subsp. kurstaki are registered against bollworms, loopers and other lepidopterans, while 12 based on Bt subsp. israelensis and three with Bt subsp. sphaericus have been used against mosquitoes. Two viruses are registered, namely Helicoverpa armigera nucleopolyhedrovirus (22 products) and Spodoptera litura nucleopolyhedrovirus (5 products) for use against bollworms and armyworms. Four entomopathogenic nematode species are sold in Indian market. These include long-lasting wettable powder formulations of Heterorhabditis indica developed by the ICAR-National Bureau of Agricultural Insect Resources, Bengaluru which have been distributed on a large scale to control white grubs and other sugarcane pests. Biopesticide research on the subcontinent is at a relatively early stage, but evolving rapidly, and focusing on indigenous entomopathogens. Despite onerous regulation, quality-control issues and limited large-scale production facilities, investment in domestic fermentation technologies, improved delivery systems, and promotion of biological control through private and public initiative will increase the share of microbial biopesticides in the country.

Ortho-Methylarylamines as Time-Dependent Inhibitors of Cytochrome P450 1A1 Enzyme

BACKGROUND

Members of the cytochrome P450 1A family metabolize many procarcinogens such as polycyclicaromatic hydrocarbons and heterocyclic amines. Inactivation of these enzymes is a prerequisite for cancer prevention and treatment in certain cases. Mechanism-based inhibition (time and co-factor dependent) is an effective method for the inactivation of these enzymes. Our recent study on emodin analogs revealed an anthraquinone with ortho-methylarylamine moiety that exhibited timedependent inhibition of P450 enzymes 1A1 and 1A2.

METHODS

To determine whether the amino group or the methyl group or both were responsible for the time-dependent inhibition of these enzymes, a set of eleven compounds containing the orthomethylarylamine moiety were identified through a database search, and studied for the inhibition of the P450 enzymes 1A1, 1A2, 2A6 and 2B1. Our earlier studies on carbazole derivatives provided us with highly selective P450 1A2 inhibitors. Glycine scanning studies were performed on the docked proteinligand complexes of compounds 1-20 in order to understand the contribution of different protein residues towards the ligand binding.

RESULTS

Four compounds were found to cause selective time-dependent inhibition of P450 1A1 with KI values ranging from 0.24 to 8.25 mM. These compounds exhibited only direct inhibition of P450 1A2. Molecular modeling studies of these molecules indicated that the shapes of the molecules, their binding modes, and the methyl substituent in close proximity (4.5-5.7 Å) to the heme-Fe all contributed to their selective time-dependent inhibition activity on P450 1A1. Glycine scanning studies for P450 1A1 indicated that ligand interaction with Phe123 was the strongest binding contributor and similar studies for P450 1A2 indicated that ligand interactions with the phenylalanine residues 226 and 260 were the largest binding contributors.

CONCLUSION

Four compounds have been identified that exhibit selective time-dependent inhibition of P450 1A1. Modeling studies have indicated that the proximity of the aromatic methyl group to the heme-Fe could be the main contributor for time-dependent inhibition. Future studies will focus on the confirmation of the involvement of the aromatic methyl group in enzyme inactivation.

Computational protein design and protein-ligand interaction studies for the improvement of organophosphorus degrading potential of Deinococcus radiodurans

The organophosphorus hydrolase enzyme is involved in the catalyzing reaction that involve hydrolysis of organophosphate toxic compounds. An enzyme from Deinococcus radiodurans reported as homologous to phosphotriesterase and show activity against organophosphate. In the past activity of this enzyme is low and efforts made to improve the activity by experimental mutation study. However only very few organophosphates tested against very few catalytic site mutations. In order to improve the catalytic power of the organophosphorus hydrolase enzyme, we carried out systematic functional hotspot based protein engineering strategy. The mutants tested against 46 know organophosphate compounds using molecular docking study. Finally, we carried out an extensive molecular docking study to predict the binding of 46 organophosphate compounds to wild-type protein and mutant organophosphorus hydrolase enzyme. At the end we are able to improve the degrading potential of organophosphorus hydrolase enzyme against organophosphate toxic compounds. This preliminary study and the outcome would be useful guide for the experimental scientist involved in the bioremediation of toxic organophosphate compounds.

DESIGN AND SYNTHESIS OF DIBENZYLFURAN BASED ETHER AND ESTER DERIVATIVES AS POTENTIAL P450 INHIBITORS

Cytochrome P450 enzymes are a superfamily of hemoproteins involved in the metabolism and detoxification of endogenous and exogenous compounds. P450s are involved in the bioactivation of certain procarcinogens leading to the production of carcinogenic species. This has resulted in P450s' popularity as targets in cancer research. Developing selective and potent mechanism-based inhibitors for these enzymes is expected to be the key to understanding their mechanisms of action, as well as, developing potential anticancer agents. Our group has shown that certain aryl and aryl-alkyl acetylenes act as inhibitors of these enzymes. In an attempt to increase the number of selective P450 inhibitors available for enzymatic studies, five novel dibenzofuran ethers and esters have been designed and synthesized successfully.

Synthetic Method to Form 2,2'-Bis(naphthoquinone) Compounds

We have discovered a transition-metal-free approach to the synthesis of 2,2'-bis(naphthoquinones) using a Diels-Alder reaction of conjugated ketene silyl acetals with benzoquinone. Its monomer analogue can also be synthesized by simply increasing the equivalents of benzoquinone.

Review of Ligand Specificity Factors for CYP1A Subfamily Enzymes from Molecular Modeling Studies Reported to-Date

The cytochrome P450 (CYP) family 1A enzymes, CYP1A1 and CYP1A2, are two of the most important enzymes implicated in the metabolism of endogenous and exogenous compounds through oxidation. These enzymes are also known to metabolize environmental procarcinogens into carcinogenic species, leading to the advent of several types of cancer. The development of selective inhibitors for these P450 enzymes, mitigating procarcinogenic oxidative effects, has been the focus of many studies in recent years. CYP1A1 is mainly found in extrahepatic tissues while CYP1A2 is the major CYP enzyme in human liver. Many molecules have been found to be metabolized by both of these enzymes, with varying rates and/or positions of oxidation. A complete understanding of the factors that govern the specificity and potency for the two CYP 1A enzymes is critical to the development of effective inhibitors. Computational molecular modeling tools have been used by several research groups to decipher the specificity and potency factors of the CYP1A1 and CYP1A2 substrates. In this review, we perform a thorough analysis of the computational studies that are ligand-based and protein-ligand complex-based to catalog the various factors that govern the specificity/potency toward these two enzymes.

Osteoinductive effects of glyceollins on adult mesenchymal stromal/stem cells from adipose tissue and bone marrow

BACKGROUND

While current therapies for osteoporosis focus on reducing bone resorption, the development of therapies to regenerate bone may also be beneficial. Promising anabolic therapy candidates include phytoestrogens, such as daidzein, which effectively induce osteogenesis of adipose-derived stromal cells (ASCs) and bone marrow stromal cells (BMSCs).

PURPOSE

To investigate the effects of glyceollins, structural derivatives of daidzein, on osteogenesis of ASCs and BMSCs.

STUDY DESIGN

Herein, the osteoinductive effects of glyceollin I and glyceollin II were assessed and compared to estradiol in ASCs and BMSCs. The mechanism by which glyceollin II induces osteogenesis was further examined.

METHODS

The ability of glyceollins to promote osteogenesis of ASCs and BMSCs was evaluated in adherent and scaffold cultures. Relative deposition of calcium was analyzed using Alizarin Red staining, Bichinchoninic acid Protein Assay, and Alamar Blue Assay. To further explore the mechanism by which glyceollin II exerts its osteoinductive effects, docking studies of glyceollin II, RNA isolation, cDNA synthesis, and quantitative RT-PCR (qPCR) were performed.

RESULTS

In adherent cultures, ASCs and BMSCs treated with estradiol, glyceollin I, or glyceollin II demonstrated increased calcium deposition relative to vehicle-treated cells. During evaluation on PLGA scaffolds seeded with ASCs and BMSCs, glyceollin II was the most efficacious in inducing ASC and BMSC osteogenesis compared to estradiol and glyceollin I. Dose-response analysis in ASCs and BMSCs revealed that glyceollin II has the highest potency at 10nM in adherent cultures and 1µM in tissue scaffold cultures. At all doses, osteoinductive effects were attenuated by fulvestrant, suggesting that glyceollin II acts at least in part through estrogen receptor-mediated pathways to induce osteogenesis. Analysis of gene expression demonstrated that, similar to estradiol, glyceollin II induces upregulation of genes involved in osteogenic differentiation.

CONCLUSION

The ability of glyceollin II to induce osteogenic differentiation in ASCs and BMSCs indicates that glyceollins hold the potential for the development of pharmacological interventions to improve clinical outcomes of patients with osteoporosis.

Ligands of Therapeutic Utility for the Liver X Receptors

Liver X receptors (LXRs) have been increasingly recognized as a potential therapeutic target to treat pathological conditions ranging from vascular and metabolic diseases, neurological degeneration, to cancers that are driven by lipid metabolism. Amidst intensifying efforts to discover ligands that act through LXRs to achieve the sought-after pharmacological outcomes, several lead compounds are already being tested in clinical trials for a variety of disease interventions. While more potent and selective LXR ligands continue to emerge from screening of small molecule libraries, rational design, and empirical medicinal chemistry approaches, challenges remain in minimizing undesirable effects of LXR activation on lipid metabolism. This review provides a summary of known endogenous, naturally occurring, and synthetic ligands. The review also offers considerations from a molecular modeling perspective with which to design more specific LXRβ ligands based on the interaction energies of ligands and the important amino acid residues in the LXRβ ligand binding domain.

Population genetic structure of cotton pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) using mitochondrial cytochrome oxidase I (COI) gene sequences from India

Pink bollworm (PBW), Pectinophora gossypiella is one of the most destructive pest's globally inflicting huge economic losses in cotton even during later stages of crop growth. In the present investigation, the population genetic structure, distribution, and genetic diversity of P. gossypiella in cotton growing zones of India using partial mitochondrial DNA cytochrome oxidase-I (COI) gene was addressed. The overall haplotype (Hd), number of nucleotide differences (K), and nucleotide diversity (π) were 0.3028, 0.327, and 0.00047, respectively which suggest that entire population exhibited low level of genetic diversity. Zone-wise clustering of population revealed that central zone recorded low level of Hd (0.2730) as compared to north (0.3619) and south (0.3028) zones. The most common haplotype (H1) reported in all 19 locations could be proposed as ancestral/original haplotype. This haplotype with one mutational step formed star-like phylogeny connected with 11 other haplotypes. The phylogenetic relationship studies revealed that most haplotypes of populations are closely related to each other. Haplotype 5 was exclusively present in Dharwad (South zone) shared with populations of Hanumangarh and Bathinda (North zone). The result indicated that there is no isolation by distance effect among the Indian populations of PBW. The present study reports a low genetic diversity among PBW populations of India and H1, as ancestral haplotype from which other haplotypes have evolved suggests that the migration and dispersal over long distance and invasiveness are major factors.

Molecular modeling and structural analysis of nAChR variants uncovers the mechanism of resistance to snake toxins

Nicotinic acetylcholine receptors (nAChRs) are neuromuscular proteins responsible for muscle contraction upon binding with chemical stimulant acetylcholine (ACh). The α-neurotoxins of snake mimic the structure of ACh and attacks nAChRs, which block the flow of ACh and leads to numbness and paralysis. The toxin-binding site of alpha subunit in the nAChRs is highly conserved throughout chordate lineages with few exceptions in resistance organisms. In this study, we have analyzed the sequence and structures of toxin-binding/resistant nAChRs and their interaction stability with toxins through molecular docking and molecular dynamics simulation (MDS). We have reported the potential glycosylation residues within the toxin-binding cleft adding sugar moieties through N-linked glycosylation in resistant organisms. Residue variations at key positions alter the secondary structure of binding cleft, which might interfere with toxin binding and it could be one of the possible explanations for the resistance to snake venoms. Analysis of nAChR-α-neurotoxin complexes has confirmed the key interacting residues. In addition, drastic variation in the binding stability of Mongoose nAChR-α-Bungarotoxin (α-BTX) and human nAChR-α-BTX complexes were found at specific phase of MDS. Our findings suggest that specific mutations in the binding site of toxin are potentially preventing the formation of stable complex of receptor-toxin, which might lead to mechanism of resistance. This in silico study on the binding cleft of nAChR and the findings of interacting residues will assist in designing potential inhibitors as therapeutic targets.

Novel functionalized 5-(phenoxymethyl)-1,3-dioxane analogs exhibiting cytochrome P450 inhibition: a patent evaluation WO2015048311 (A1)

Cytochrome P450's (CYP's) constitute a diverse group of over 500 monooxygenase hemoproteins, catalyzing transformations that involve xenobiotic metabolism, steroidogenesis and other metabolic processes. Over-production of the steroid hormone cortisol is implicated in the progression of diseases such as diabetes, heart failure and hypertension, stroke, Cushing's syndrome, obesity and renal failure, among others. The biosynthesis of cortisol involves a cascade of cholesterol metabolizing reactions regulated through three major CYP proteins: 17α-hydroxylase-C17/20-lyase (CYP17), 21-hydroxylase (CYP21), and 11β-hydroxylase (CYP11B1). Excess activities of these enzymes are linked to the progression of malignancies including prostate, breast, ovarian, and uterine cancers. A series of novel functionalized dioxane analogs have been developed and recently patented as CYP17, CYP21, and CYP11B1 inhibitors, which lead to the modulation of cortisol production as a method for treating, delaying, slowing, and inhibiting the implicated diseases. The findings disclosed in this patent have been analyzed and compared with the literature data on inhibitors of CYP17, CYP21, and CYP11B1. The compiled data provide insight into the novel functionality of the compounds described in the patent. In this regard, an objective opinion on the effectiveness and novel biochemistry of these compounds in comparison to current CYP inhibitors used in the treatment of cortisol-related diseases is presented in this paper.

Small molecule tyrosine kinase inhibitors of ErbB2/HER2/Neu in the treatment of aggressive breast cancer

The human epidermal growth factor receptor 2 (HER2) is a member of the erbB class of tyrosine kinase receptors. These proteins are normally expressed at the surface of healthy cells and play critical roles in the signal transduction cascade in a myriad of biochemical pathways responsible for cell growth and differentiation. However, it is widely known that amplification and subsequent overexpression of the HER2 encoding oncogene results in unregulated cell proliferation in an aggressive form of breast cancer known as HER2-positive breast cancer. Existing therapies such as trastuzumab (Herceptin®) and lapatinib (Tyverb/Tykerb®), a monoclonal antibody inhibitor and a dual EGFR/HER2 kinase inhibitor, respectively, are currently used in the treatment of HER2-positive cancers, although issues with high recurrence and acquired resistance still remain. Small molecule tyrosine kinase inhibitors provide attractive therapeutic targets, as they are able to block cell signaling associated with many of the proposed mechanisms for HER2 resistance. In this regard we aim to present a review on the available HER2 tyrosine kinase inhibitors, as well as those currently in development. The use of tyrosine kinase inhibitors as sequential or combinatorial therapeutic strategies with other HER family inhibitors is also discussed.

Ethynylflavones, highly potent, and selective inhibitors of cytochrome P450 1A1

The flavone backbone is a well-known pharmacophore present in a number of substrates and inhibitors of various P450 enzymes. In order to find highly potent and novel P450 family I enzyme inhibitors, an acetylene group was incorporated into six different positions of flavone. The introduction of an acetylene group at certain locations of the flavone backbone lead to time-dependent inhibitors of P450 1A1. 3′-Ethynylflavone, 4′-ethynylflavone, 6-ethynylflavone, and 7-ethynylflavone (K_I values of 0.035–0.056 μM) show strong time-dependent inhibition of P450 1A1, while 5-ethynylflavone (K_I value of 0.51 μM) is a moderate time-dependent inhibitor of this enzyme. Meanwhile, 4′-ethynylflavone and 6-ethynylflavone are highly selective inhibitors toward this enzyme. Especially, 6-ethynylflavone possesses a K_i value of 0.035 μM for P450 1A1 177- and 15-fold lower than those for P450s 1A2 and 1B1, respectively. The docking postures observed in the computational simulations show that the orientation of the acetylene group determines its capability to react with P450s 1A1 and 1A2. Meanwhile, conformational analysis indicates that the shape of an inhibitor determines its inhibitory selectivity toward these enzymes.

Modification and biological evaluation of thiazole derivatives as novel inhibitors of metastatic cancer cell migration and invasion

Fascin has recently emerged as a potential therapeutic target, as its expression in cancer cells is closely associated with tumor progression and metastasis. Following the initial discovery of a series of thiazole derivatives that demonstrated potent antimigration and antiinvasion activities via possible inhibition of fascin function, we report here the design and synthesis of 63 new thiazole derivatives by further structural modifications in search of more potent fascin inhibitors. The 5 series of analogues with longer alkyl chain substitutions on the thiazole nitrogen exhibited greater antimigration activities than those with other structural motifs. The most potent analogue, 5p, inhibited 50% of cell migration at 24 nM. Moreover, the thiazole analogues showed strong antiangiogenesis activity, blocking new blood vessel formation in a chicken embryo membrane assay. Finally, a functional study was conducted to investigate the mechanism of action via interaction with the F-actin bundling protein fascin.

Identification of quinones as HER2 inhibitors for the treatment of trastuzumab resistant breast cancer

HER2 overexpression is associated with aggressive breast cancer with high recurrence rate and poor patient prognosis. Treatment of HER2 overexpressing patients with the HER2 targeting therapy trastuzumab results in acquired resistance within a year. The HER2/EGFR dual kinase inhibitor lapatinib was shown to inhibit some trastuzumab resistant breast cancer cell lines and is currently in clinical trials. Our group has found two new quinone compounds that show excellent inhibition of breast tumor cells expressing HER2 or the trastuzumab resistant HER2 oncogenic isoform, HER2Δ16. Compound 4 ((1R,2S,3S)-1,2,3,5,8-pentahydroxy-1,2,3,4-tetrahydroanthracene-9,10-dione) and compound 5 (5,8-dihydroxy-2,3-bis(hydroxymethyl)naphthalene-1,4-dione) showed sub-micromolar inhibition potency against these cell lines. These compounds also inhibit auto-phosphorylation of the Y1248 and Y1068 residues of HER2 and EGFR, respectively.

The morphometric analysis of the mental foramen in adult dry human mandibles: a study on the South Indian population

AIM

The mental foramen is a small foramen which is located in the antero-lateral aspect of the body of the mandible. It is situated midway between the upper and the lower border of the mandible and it transmits the mental nerve and the vessels. The knowledge on the anatomy of the mental foramen is very important in clinical dentistry and in surgical procedures which involve that area.

MATERIAL AND METHODS

Our study was conducted on 90 adult dry human mandibles from the south Indian population, irrespective of age and sex. The location, shape, orientation and the presence of the accessory foramen were studied by visual examination. The size and position of the mental foramen were measured by using a digital vernier caliper. The SPSS, version 15 software was used for the statistical analysis, to calculate the minimum, maximum, incidence, mean and standard deviation.

RESULTS

In a majority of the mandibles, the mental foramen was located at the level of the root of the 2(nd) premolar, midway between the inferior margin and the alveolar margin of the mandible. Most of the mental foramina were oval in shape. The orientation of the foramen was postero-superior in 83% of the mandibles. The accessory foramens were noted in five mandibles.

CONCLUSION

The knowledge on the variations in the position and size of the mental foramen and the presence of the accessory foramen may be of much use to dental surgeons.

DESIGN, SYNTHESIS, AND EVALUATION OF CARBAZOLE ANALOGS AS POTENTIAL CYTOCHROME P450 INHIBITORS

Carbazoles are a class of nitrogen-containing aromatic heterocyclic compounds. They not only have various biological activities (e.g. antibacterial, anti-inflammatory, antitumor), but also exhibit useful properties as organic materials due to their special structures. Cytochrome P450 enzymes are a superfamily of hemoproteins involved in the metabolism of endogenous and exogenous compounds including many drugs and environmental chemicals. Some aryl and arylalkyl acetylenes, and propargyl ethers have been shown to act as inhibitors of certain P450s. In an attempt to improve the potency and selectivity of inhibition, we have focused our attention on the design and synthesis of a new series of carbazole analogs, a few of which contain a propargyl ether functional group. For this project, eight carbazole analogs have been synthesized and characterized.

Pyranoflavones: a group of small-molecule probes for exploring the active site cavities of cytochrome P450 enzymes 1A1, 1A2, and 1B1

Selective inhibition of P450 enzymes is the key to block the conversion of environmental procarcinogens to their carcinogenic metabolites in both animals and humans. To discover highly potent and selective inhibitors of P450s 1A1, 1A2, and 1B1, as well as to investigate active site cavities of these enzymes, 14 novel flavone derivatives were prepared as chemical probes. Fluorimetric enzyme inhibition assays were used to determine the inhibitory activities of these probes toward P450s 1A1, 1A2, 1B1, 2A6, and 2B1. A highly selective P450 1B1 inhibitor 5-hydroxy-4'-propargyloxyflavone (5H4'FPE) was discovered. Some tested compounds also showed selectivity between P450s 1A1 and 1A2. α-Naphthoflavone-like and 5-hydroxyflavone derivatives preferentially inhibited P450 1A2, while β-naphthoflavone-like flavone derivatives showed selective inhibition of P450 1A1. On the basis of structural analysis, the active site cavity models of P450 enzymes 1A1 and 1A2 were generated, demonstrating a planar long strip cavity and a planar triangular cavity, respectively.

DESIGN, SYNTHESIS, AND EVALUATION OF A FAMILY OF PROPARGYL PYRIDINYL ETHERS AS POTENTIAL CYTOCHROME P450 INHIBITORS

Cytochrome P450 enzymes are a superfamily of hemoproteins involved in the metabolism of endogenous and exogenous compounds including many drugs and environmental chemicals. In our previous research, we have determined that certain aryl and arylalkyl acetylenes act as inhibitors of these enzymes. Here we report a family of propargyl ethers containing a pyridine ring system. Five new compounds, 2,4-dimethyl-3-(prop-2-yn-1-yloxy)pyridine(I), 2,4-dimethyl-3-((prop-2-yn-1-yloxy) methyl)pyridine(II), 2,3-dimethyl-4-((prop-2-yn-1-yloxy)methyl)pyridine(III), 2-methyl-4-((prop-2-yn-1-yloxy)methyl)pyridine (IV), 2-methyl-4-(prop-2-yn-1-yloxy)pyridine (V) (Figure 1) have been synthesized and characterized.

Insights on cytochrome p450 enzymes and inhibitors obtained through QSAR studies

The cytochrome P450 (CYP) superfamily of heme enzymes play an important role in the metabolism of a large number of endogenous and exogenous compounds, including most of the drugs currently on the market. Inhibitors of CYP enzymes have important roles in the treatment of several disease conditions such as numerous cancers and fungal infections in addition to their critical role in drug-drug interactions. Structure activity relationships (SAR), and three-dimensional quantitative structure activity relationships (3D-QSAR) represent important tools in understanding the interactions of the inhibitors with the active sites of the CYP enzymes. A comprehensive account of the QSAR studies on the major human CYPs 1A1, 1A2, 1B1, 2A6, 2B6, 2C9, 2C19, 2D6, 2E1, 3A4 and a few other CYPs are detailed in this review which will provide us with an insight into the individual/common characteristics of the active sites of these enzymes and the enzyme-inhibitor interactions.

7-Ethynylcoumarins: selective inhibitors of human cytochrome P450s 1A1 and 1A2

To discover new selective mechanism-based P450 inhibitors, eight 7-ethynylcoumarin derivatives were prepared through a facile two-step synthetic route. Cytochrome P450 activity assays indicated that introduction of functional groups in the backbone of coumarin could enhance the inhibition activities toward P450s 1A1 and 1A2, providing good selectivity against P450s 2A6 and 2B1. The most potent product 7-ethynyl-3,4,8-trimethylcoumarin (7ETMC) showed IC(50) values of 0.46 μM and 0.50 μM for P450s 1A1 and 1A2 in the first six minutes, respectively, and did not show any inhibition activity for P450s 2A6 and 2B1 even at the dose of 50 μM. All of the inhibitors except 7-ethynyl-3-methyl-4-phenylcoumarin (7E3M4PC) showed mechanism-based inhibition of P450s 1A1 and 1A2. In order to explain this mechanistic difference in inhibitory activities, X-ray crystallography data were used to study the difference in conformation between 7E3M4PC and the other compounds studied. Docking simulations indicated that the binding orientations and affinities resulted in different behaviors of the inhibitors on P450 1A2. Specifically, 7E3M4PC with its two-plane structure fits into the P450 1A2's active site cavity with an orientation leading to no reactive binding, causing it to act as a competitive inhibitor.

Inhibition of cytochrome p450 enzymes by quinones and anthraquinones

In silico docking studies and quantitative structure-activity relationship analysis of a number of in-house cytochrome P450 inhibitors have revealed important structural characteristics that are required for a molecule to function as a good inhibitor of P450 enzymes 1A1, 1A2, 2B1, and/or 2A6. These insights were incorporated into the design of pharmacophores used for a 2D search of the Chinese medicine database. Emodin, a natural anthraquinone isolated from Rheum emodi and known to be metabolized by cytochrome P450 enzymes, was one of the hits and was used as the lead compound. Emodin was found to inhibit P450s 1A1, 1A2, and 2B1 with IC(50) values of 12.25, 3.73, and 14.89 μM, respectively. On the basis of the emodin molecular structure, further similarity searches of the PubChem and ZINC chemical databases were conducted resulting in the identification of 12 emodin analogues for testing against P450s 1A1-, 1A2-, 2B1-, and 2A6-dependent activities. 1-Amino-4-chloro-2-methylanthracene-9,10-dione (compound 1) showed the best inhibition potency for P450 1A1 with an IC(50) value of 0.40 μM. 1-Amino-4-chloro-2-methylanthracene-9,10-dione (compound 1) and 1-amino-4-hydroxyanthracene-9,10-dione (compound 2) both inhibited P450 1A2 with the same IC(50) value of 0.53 μM. In addition, compound 1 acted as a mechanism-based inhibitor of cytochrome P450s 1A1 and 1A2 with K(I) and K(inactivation) values of 5.38 μM and 1.57 min(-1) for P450 1A1 and 0.50 μM and 0.08 min(-1) for P450 1A2. 2,6-Di-tert-butyl-5-hydroxynaphthalene-1,4-dione (compound 8) directly inhibited P450 2B1 with good selectivity and inhibition potency (IC(50) = 5.66 μM). Docking studies using the 3D structures of the enzymes were carried out on all of the compounds. The binding modes of these compounds revealed the structural characteristics responsible for their potency and selectivity. Compound 1, which is structurally similar to compound 2 with the presence of an amino group at position 1, showed a difference in the mechanism of inhibition toward P450s 1A1 and 1A2. The mechanism-based inhibition seen for compound 1 may be attributed to the presence of the methyl group at the 2-position, in close proximity to the amino group. Compound 2, which is otherwise similar, lacks that methyl moiety and did not show mechanism-based inhibition.

Development of flavone propargyl ethers as potent and selective inhibitors of cytochrome P450 enzymes 1A1 and 1A2

Naturally occurring flavonoids are known to be metabolized by several cytochrome P450 enzymes including P450s 1A1, 1A2, 1B1, 2C9, 3A4, and 3A5. In general flavonoids can act as substrates, inducers, and/or inhibitors of P450 enzymes. The position of the substituents on the flavone backbone has been shown to impact the biological activity against P450 enzymes. To explore the effect of a propargyl ether substitution on flavones and flavanones, 2´-flavone propargyl ether (2´-PF), 3´-flavone propargyl ether (3´-PF), 4´-flavone propargyl ether (4´-PF), 5-flavone propargyl ether (5-PF), 6-flavone propargyl ether (6-PF), 7-flavone propargyl ether (7-PF), 6-flavanone propargyl ether (6-PFN), and 7- flavanone propargyl ether (7-PFN) were synthesized. All of the newly synthesized compounds and the parent hydroxy flavones were tested for both direct inhibition and mechanism-based inhibition of cytochrome P450 enzymes 1A1, 1A2, 2A6, and 2B1. The flavone propargyl ether derivatives were found to be more potent inhibitors of P450s 1A1 and 1A2. None of the flavones and flavanones in our study showed any inhibition of P450 2A6. Only 2´-PF and 6-PFN inhibited P450 2B1. 3´-PF showed direct inhibition of P450 1A1 with the highest observed potency of 0.02 µM, in addition to its ability to cause mechanism-based inhibition with KI and kinactivation values of 0.24 µM and 0.09 min-1 for this enzyme. 7- Hydroxy flavone also exhibited mechanism-based inhibition of P450 1A1 with KI and kinactivation values of 2.43 µM and 0.115 min-1. Docking studies and QSAR studies on P450 enzymes 1A1 and 1A2 were performed which revealed important insights into the nature of binding of these molecules and provided us with good QSAR models that can be used to design new flavone derivatives.

QSAR models of cytochrome P450 enzyme 1A2 inhibitors using CoMFA, CoMSIA and HQSAR

Quantitative structure-activity relationship (QSAR) studies were conducted on an in-house database of cytochrome P450 enzyme 1A2 inhibitors using the comparative molecular field analysis (CoMFA), comparative molecular similarity analysis (CoMSIA) and hologram QSAR (HQSAR) approaches. The database consisted of 36 active molecules featuring varied core structures. The model based on the naphthalene substructure alignment incorporating 19 molecules yielded the best model with a CoMFA cross validation value q(2) of 0.667 and a Pearson correlation coefficient r(2) of 0.976; a CoMSIA q(2) value of 0.616 and r(2) value of 0.985; and a HQSAR q(2) value of 0.652 and r(2) value of 0.917. A second model incorporating 34 molecules aligned using the benzene substructure yielded an acceptable CoMFA model with q(2) value of 0.5 and r(2) value of 0.991. Depending on the core structure of the molecule under consideration, new CYP1A2 inhibitors will be designed based on the results from these models.

Effects of 7-O substitutions on estrogenic and anti-estrogenic activities of daidzein analogues in MCF-7 breast cancer cells

Daidzein (1) is a natural estrogenic isoflavone. We report here that 1 can be transformed into anti-estrogenic ligands by simple alkyl substitutions of the 7-hydroxyl hydrogen. To test the effect of such structural modifications on the hormonal activities of the resulting compounds, a series of daidzein analogues have been designed and synthesized. When MCF-7 cells were treated with the analogues, those resulting from hydrogen substitution by isopropyl (3d), isobutyl (3f), cyclopentyl (3g), and pyrano- (2) inhibited cell proliferation, estrogen-induced transcriptional activity, and estrogen receptor (ER) regulated progesterone receptor (PgR) gene expression. However, methyl (3a) and ethyl (3b) substitutions of the hydroxyl proton only led to moderate reduction of the estrogenic activities. These results demonstrated the structural requirements for the transformation of daidzein from an ER agonist to an antagonist. The most effective analogue, 2, was found to reduce in vivo estrogen stimulated MCF-7 cell tumorigenesis using a xenograft mouse model.

In silico studies of polyaromatic hydrocarbon inhibitors of cytochrome P450 enzymes 1A1, 1A2, 2A6, and 2B1

A computational study was undertaken to understand the nature of binding and the structural features that play a significant role in the binding of arylacetylene molecules to cytochrome P450 enzymes 1A1, 1A2, 2A6, and 2B1. Nine polycyclic arylacetylenes determined to be mechanism-based P450 enzyme inhibitors were studied. The lack of polar substituents in these compounds causes them to be incapable of hydrogen bonding to the polar protein residues. The four P450 enzymes of interest all have phenylalanine residues in the binding pocket for potential pi-pi interactions with the aromatic rings of the inhibitors. The inhibition potency of these arylacetylenes toward P450s 1A1 and 2B1 showed a dependence on the proximity of the inhibitor's triple bond to the prosthetic heme Fe of the enzyme. In P450 enzyme 1A2, the inhibitor's potency showed more dependence on the pi-pi interactions of the inhibitor's ring systems with the phenylalanine residues of the protein, with the proximity of the inhibitor triple bond to the heme Fe weighing in as the second most important factor. The results suggest that maximizing the pi-pi interactions with phenylalanine residues in the binding pocket and optimum proximity of the acetylene moiety to the heme Fe will provide for a substantial increase in the potency of the polyaromatic hydrocarbon mechanism-based inhibitors. A fine balance of these two aspects of binding coupled with attention to supplementing hydrophobic interactions could address potency and selectivity issues for these inhibitors.

Highly potent and specific GSK-3beta inhibitors that block tau phosphorylation and decrease alpha-synuclein protein expression in a cellular model of Parkinson's disease

Research by Klein and co-workers suggests that the inhibition of GSK-3beta by small molecules may offer an important strategy in the treatment of a number of central nervous system (CNS) disorders including Alzheimer's disease, Parkinson's disease, and bipolar disorders. Based on results from kinase-screening assays that identified a staurosporine analogue as a modest inhibitor of GSK-3beta, a series of 3-indolyl-4-indazolylmaleimides was prepared for study in both enzymatic and cell-based assays. Most strikingly, whereas we identified ligands having poor to high potency for GSK-3beta inhibition, only ligands with a Ki value of less than 8 nM, namely maleimides 18 and 22, were found to inhibit Tau phosphorylation at a GSK-3beta-specific site (Ser 396/404). Accordingly, maleimides 18 and 22 may protect neuronal cells against cell death by decreasing the level of alpha-Syn protein expression. We conclude that the GSK-3beta inhibitors described herein offer promise in defending cells against MPP+-induced neurotoxicity and that such compounds will be valuable to explore in animal models of Parkinson's disease as well as in other Tau-related neurodegenerative disease states.

Selectivity and potency of cyclin-dependent kinase inhibitors

Members of the cyclin-dependent kinase (CDK) family play key roles in various cellular processes. There are 11 members of the CDK family known till now. CDKs are activated by forming noncovalent complexes with cyclins such as A-, B-, C-, D- (D1, D2, and D3), and E-type cyclins. Each isozyme of this family is responsible for particular aspects (cell signaling, transcription, etc) of the cell cycle, and some of the CDK isozymes are specific to certain kinds of tissues. Aberrant expression and overexpression of these kinases are evidenced in many disease conditions. Inhibition of isozymes of CDKs specifically can yield beneficiary treatment modalities with minimum side effects. More than 80 3-dimensional structures of CDK2, CDK5, and CDK6 complexed with inhibitors have been published. This review provides an understanding of the structural aspects of CDK isozymes and binding modes of various known CDK inhibitors so that these kinases can be better targeted for drug discovery and design. The amino acid residues that constitute the cyclin binding region, the substrate binding region, and the area around the adenosine triphosphate (ATP) binding site have been compared for CDK isozymes. Those amino acids at the ATP binding site that could be used to improve the potency and subtype specificity have been described.

Chimeric monoclonal antibody to tumor necrosis factor alpha (infliximab) in psoriasis

BACKGROUND

Insights into the pathogenesis of psoriasis have provided opportunities to target key steps in the disease process. Tumor necrosis factor-alpha (TNF- alpha) being crucial to the pathogenesis of psoriasis, monoclonal antibodies against this cytokine have proved useful in its treatment.

AIM

To study the efficacy of chimeric monoclonal antibody to TNF- alpha (infliximab) in Indian patients with recalcitrant psoriasis vulgaris.

MATERIALS AND METHODS

Three patients with recalcitrant psoriasis vulgaris were studied. Baseline haemogram, biochemical parameters, chest radiograph and Mantoux skin test were performed. A loading dose regimen of 5 mg/kg infliximab was administered at weeks 0, 2 and 6. PASI assessment, adverse drug event monitoring and laboratory assessments were carried out at 2-week intervals until week 10. Patients were followed up until week 22 for relapse.

RESULTS

Infliximab was well tolerated. The mean PASI was 25.4 at presentation and declined to 5.5 at 10 weeks. PASI 75 was attained at a mean of 9.6 weeks. Relapse occurred at a mean of 18.6 weeks after the first infusion.

CONCLUSIONS

This study on Indian patients brings out the importance of cytokine-based therapies in psoriasis. Indigenous production could make these therapies a viable therapeutic option for psoriasis patients in the near future.

Identification of novel angiogenesis inhibitors

Vascular endothelial growth factor (VEGF) is a key stimulant of angiogenesis, which is the process of generating new capillary blood vessels. Inhibition of the vascular endothelial growth factor receptor (VEGFR) kinase is known to result in blockage of angiogenesis. A pharmacophore was developed based on the binding of ATP to the hinge region of the kinase domain of VEGFR and a database search of 18,000 compounds was conducted. Selected hits were assessed for their ability to limit the induction of web-like network of capillary tubes by the human umbilical vascular endothelial cells. Two compounds (1 and 4) showed good inhibitory ability to prevent sprouting and closed polygon formation of the tubular networks, promising them to be lead compounds. Compound 4 showed 60% inhibition at 0.05 microM.

Isolation and characterization of a green tissue-specific promoter from pigeonpea [Cajanus cajan (L.) Millsp.]

Expression of rbcS genes encoding small subunit of rubisco, most abundant protein in green tissue, is regulated by at least three parameters--tissue type, light conditions and stage of development. One of the green tissue-specific promoters of rbcS gene family was isolated from pigeonpea by PCR. Expression of uidA gene encoding beta-glucuronidase in the transgenic tobacco plants under the control of pigeonpea rbcS promoter, clearly showed that this promoter was as strong as pea rbcS3A promoter characterized earlier. Study of the sequence similarity with pea rbcS3A promoter, especially the region (boxes I and III) that is required for rbcS3A expression, showed more than 50% divergence. In contrast, pigeonpea promoter sequence isolated in the present study was more similar to that of spinach and rice rbcS promoters.

Binding modes of 6,7 di-substituted 4-anilinoquinoline-3-carbonitriles to EGFR

4-Anilino-3-cyanoquinolines were reported to have irreversible binding to epidermal growth factor receptor kinase (EGFRK) by forming a covalent linkage to C773. Our initial docking studies gave results inconsistent with the in vitro data and showed two different binding modes. To perceive the exact mode of binding of these ligands, two models of the ligand-EGFR complexes were considered: (1) reversible binding mode in which the ligand had hydrogen bond interactions at the binding site and (2) irreversible binding mode wherein the ligand's Michael acceptor side chain has proximity to the sulfhydryl group of C773 of EGFR, thereby enabling a covalent interaction. The irreversible binding mode correlated better than reversible binding mode with respect to in vitro data. However, our results indicate that both modes are being adopted by the ligands and could be utilized to design more potent EGFRK inhibitors.

New bivalent PKC ligands linked by a carbon spacer: enhancement in binding affinity

Protein kinase C (PKC) is known to play an important role in many signal transduction pathways involved in hormone release, mitogenesis, and tumor promotion. In continuation of our efforts to find highly potent activators of PKC for possible use as Alzheimer's disease therapeutics, we designed and synthesized molecules containing two binding moieties (amides of benzolactams or esters of naphthylpyrrolidones) connected by a flexible spacer chain, which could theoretically bind to both the C1a and C1b activator binding domains of the catalytic region or to the C1 domains of two adjacent PKC molecules. The dimers 2a-g of benzolactam showed a 200-fold increase in affinity to PKCalpha and -delta as the spacer length increased from 4 to 20 carbon atoms. Replacement of the oligomethylene chain with an oligoethylene glycol unit (compounds 2h, 2i) showed a 4000- to 7000-fold decrease in affinity to PKCalpha. The dimers of naphthylpyrrolidones 4a-g did not show any marked improvement in binding affinities to PKC in comparison to the monomers synthesized earlier. The dimer of benzolactam 2e did not show much selectivity for PKCalpha, -betaIota, -delta, -epsilon, and -gamma. The high binding affinity of compounds 2d-g to PKCs gives us the impetus to design additional molecules that would retain this enhanced activity and would also show selectivity for the PKC isoforms.