Lead Compound For Cancer Therapy Research Articles

2D QSAR Modelling, Docking, Synthesis and Evaluation of 2-substituted Benzimidazole Derivatives as Anti-breast Cancer Agents

Background: Cancer is a leading cause of death worldwide and is anticipated to reach 28,4 million fresh cases globally by 2040. Despite all the progress made in cancer prevention, diagnosis, and treatment, mortality by cancer is in second place. Objectives: The design of novel 2-substituted benzimidazole modelled by QSAR study. Molecular docking studies on the novel derivatives and synthesis characterization and evaluation of the anticancer activity of the novel derivatives against breast cancer cell line MCF 7. Methods: We designed 10 novel benzimidazole derivatives modeled by 2D QSAR. From the ten compounds by applying insilico tools of ADME properties and toxicity and through molecular docking on Tyrosine Kinase (PDB ID: 2SRC). Compound 2AD showed the highest dock score of -9.5 kcal/mol followed by 2 BD and 2GD (-9.3kcal/mol) Molecular dynamic simulation studies were conducted using CABSflex an online molecular dynamic simulation tool. Six compounds were selected for synthesis. The synthesized compounds were characterized and the invitro pharmacological activity was tested on MCF-7 cell line by MTT assay. Results: The compounds 2AD and 2GD showed good percentage inhibition on MCF-7 cell line withIC50 values of 2.757 µg/ml and 2.875 µg/ml respectively. Conclusion: The novel 2-substituted benzimidazole derivatives are good lead compounds for cancer therapy. Optimization of these compounds will be providing more target-specific anticancer agents.

The KDM5 inhibitor PBIT reduces proliferation of castration-resistant prostate cancer cells via cell cycle arrest and the induction of senescence

The compound 2–4(4-methylphenyl)-1,2-benzisothiazol-3(2H)-one (PBIT) is an inhibitor of the KDM5 family of lysine-specific histone demethylases that has been suggested as a lead compound for cancer therapy. The goal of this study was to explore the effects of PBIT within human prostate cancers. Micromolar concentrations of PBIT altered proliferation of castration-sensitive LNCaP and castration-resistant C4–2B, LNCaP-MDV3100 and PC-3 human prostate cancer cell lines. We then characterized the mechanism underlying the anti-proliferative effects of PBIT within the C4–2B and PC-3 cell lines. Data from Cell Death ELISAs suggest that PBIT does not induce apoptosis within C4–2B or PC-3 cells. However, PBIT did increase the amount of senescence associated beta-galactosidase. PBIT also altered cell cycle progression and increased protein levels of the cell cycle protein p21. PC-3 and C4–2B cells express varying amounts of KDM5A, KDM5B, and KDM5C, the therapeutic targets of PBIT. siRNA-mediated knockdown studies suggest that inhibition of multiple KDM5 isoforms contribute to the anti-proliferative effect of PBIT. Furthermore, combination treatments involving PBIT and the PPARγ agonist 15-deoxy-Δ-12, 14 -prostaglandin J2 (15d-PGJ₂) also reduced PC-3 cell proliferation. Together, these data strongly suggest that PBIT significantly reduces the proliferation of prostate cancers via a mechanism that involves cell cycle arrest and senescence.

A new biphenanthrene with cytotoxic activity from Liparis nervosa (Thunb.) Lindl

2,7,2′-Trihydroxy-3,4,4′7′-tetramethoxy-1,1′-biphenanthrene (1), a previously undescribed biphenanthrene, and five known phenanthrenes, i.e. 2,5-dihydroxy-4-methoxy-9,10-dihydroxyphenanthrene (2), 2,4-dihydroxy −7-methoxy-9,10-dihydroxyphenanthrene (3), 7-hydroxy-2-methoxy-phenanthrene-1,4-dione (4), 7-hydroxy-2-methoxy-9,10-dihydro­phenanthrene-1,4-dione (5), and 4,4′,7,7′-tetrahydroxy-2,2′-dimethoxy-9,9′,10,10′-tetrahydro−1,1′-biphenanthrene (6) were isolated from the whole plant (stems, leaves, roots and fruits) of Liparis nervosa (Thunb.) Lindl., which is a medicinal plant of the genus Liparis in the Orchidaceae family. The structures of isolates were identified using spectroscopic methods, including NMR and mass spectrometry. Additionally, the cytotoxic potency of all the isolates against human lung cancer A549 cell line was evaluated by an MTT assay. All the isolated compounds showed cytotoxic activities with IC50 values in the range of 10.20 ± 0.81 to 42.41 ± 2.34 μM. The obtained data highlight the importance of L. nervosa as a source of natural lead compounds for cancer therapy.

Structural Basis of Nanobody Induced ACKR3 Inhibition

When bound to their small, secreted chemotactic cytokine ligands (chemokines), the G protein‐coupled receptor (GPCR) subfamily known as chemokine receptors (CKRs) can promote cell proliferation, survival, and migration towards increasing chemokine concentration gradients. Their strong association with these phenotypic hallmarks of cancer and their upregulation in cancer cells has made these receptors a topic of extensive research in the cancer field. Recent findings show upregulation of the atypical chemokine receptor 3 (ACKR3) in a wide variety of cancers including various breast, lung, and brain cancers, suggesting the involvement of ACKR3 in cancer pathogenesis. Acting as a scavenger receptor for a narrow range of chemokine ligands (CXCL12/CXCL11), binding of ACKR3 to a cognate ligand induces non‐canonical β‐arrestin dependent signaling, which can lead to receptor‐ligand internalization, and cause a unique signaling cascade to directly promote cell proliferation, cell growth, and angiogenesis. Moreover, silencing of ACKR3 in murine models has been shown to significantly decrease the growth and invasiveness of breast, lung, and endothelial cancer. The development of therapeutics capable of selectively inhibiting ACKR3 has now become an area of active interest. Despite this drive, the characteristic promiscuity of the CKR network and a lack of understanding in ACKR3’s mechanism of inhibition has left all ACKR3 antagonists to date with varying degrees of partial agonism, low specificity, or low stability. Here we identify and characterize a new antagonist of ACKR3, turning to recombinant variable domain monomers from the unique heavy‐chain only camelid antibodies or “nanobodies”. These 13 kDa nanobodies have highly conserved structures with the exception of three structural loops which encode the nanobody complimentary‐determining regions (CDRs) involved in antigen recognition and protein binding. This intricate binding epitope allows nanobodies to uniquely target complex GPCR epitopes, offering increased receptor specificity and selectivity versus small molecules and traditional antibody therapeutics. Using NMR spectroscopy, we have resolved the solution structure of the nanobody VUN701, an ACKR3 antagonist capable of completely ablating ACKR3 signaling at nanomolar concentrations. The structure of this inhibitor contains an uncharacteristically well‐ordered extended beta‐hairpin in the CDR3 region. In combination with cell‐based assays and molecular modeling, this analysis has allowed us to develop an atomic view of the VUN701‐ACKR3 interface. These findings shed light on the mechanism behind ACKR3 inhibition and drive forward the development of highly specific lead compounds for cancer therapy.

Synthesis and biological activities of simplified aplysiatoxin analogs focused on the CH/π interaction

Debromoaplysiatoxin (DAT) is a potent protein kinase C (PKC) activator with tumor-promoting and pro-inflammatory activities. Irie and colleagues have found that 10-methyl-aplog-1 (1), a simplified analog of DAT, has strong anti-proliferative activity against several cancer cell lines with few adverse effects. Therefore, 1 is a potential lead compound for cancer therapy. We synthesized a new derivative 2 which has a naphthalene ring at the side chain terminal position instead of a benzene ring, to increase CH/π interactions with Pro-241 of the PKCδ-C1B domain. Based on the synthetic route of 1, 2 was convergently synthesized in 26 linear steps from 6-hydroxy-1-naphthoic acid with an overall yield of 0.18%. Although the anti-proliferative activity of 2 was more potent than that of 1, the binding potency of 2 to the PKCδ-C1B domain did not exceed that of 1. Molecular dynamics simulation indicated the capability of 2 to simultaneously form hydrogen bonds and CH/π interactions with the PKCδ-C1B domain. Focusing on the hydrogen bonds, their geometry in the binding modes involving the CH/π interactions seemed to be sub-optimal, which may explain the slightly lower affinity of 2 compared to 1. This study could be of help in optimizing such interactions and synthesizing a promising lead cancer compound.

Abstract 1759: KDM5 inhibitor regulates growth of early stage and advanced human prostate cancer cells

Abstract Prostate cancer (PCa) remains a leading cause of cancer deaths because many patients ultimately develop an incurable castration-resistant form of metastatic PCa. While chromatin alterations are linked to PCa, the role of histone demethylases in the PCa progression has not been fully elucidated. Members of the Jumonji AT-rich interactive domain 1 (JARID1) or lysine demethylase 5 (KDM5) family of lysine demethylases are known for their ability to demethylate H3K4me3. However, the genes encoding these proteins are amplified in metastatic PCa. Literature suggests members of the KDM5 family enhance expression and function of androgen receptor (AR), a protein that drives growth of human PCa cells. The KDM5 family inhibitor 2-4(4-methylphenyl)-1,2-benzisothiazol-3(2H)-one (PBIT) has been suggested as a potential lead compound for cancer therapy since it suppresses proliferation of human breast cancer cells. However, to date no studies have tested the effects of PBIT in PCa. The goal of this study was to characterize the effects of PBIT alone and in combination with a PPARγ agonist, 15-Deoxy-Δ-12,14-prostaglandin J2 (15-dPGJ2) on PCa cells. Presto blue analyses were conducted in AR positive, castration-sensitive LNCaP cells and the castration-resistant PC3 cells expressing little to no AR. Our studies revealed that PBIT treatment decreased the proliferation of both LNCaP and PC3 cells in a dose-dependent manner. Significant decreases in cell proliferation were detected when PBIT concentrations were greater than or equal to 5 μM. In addition, 15-dPGJ2 was able to decrease the proliferation of PCa cells. Importantly, the combination of PBIT and 15-dPGJ2 significantly suppressed the growth of PC3 and LNCaP cells. The anti-proliferative effect of the combined inhibition was at least additive, as the combination index was less than 1. Furthermore, PBIT at concentrations ≥ 5 μM also reduced migration of PC3 cells. Together, our data suggest that PBIT and other KDM5 inhibitors can reduce the proliferation and migration of multiple types of PCa cells. Our findings also provide evidence that the combination of KDM5 family inhibitors and PPARγ agonists might serve as an effective therapy for advanced human PCa. Citation Format: Tunde Smith, Zhenbang Chen, LaMonica V. Stewart. KDM5 inhibitor regulates growth of early stage and advanced human prostate cancer cells [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 1759.

Hyperelodiones A-C, monoterpenoid polyprenylated acylphoroglucinols from Hypericum elodeoides, induce cancer cells apoptosis by targeting RXRα

Hyperelodiones A-C, three undescribed monoterpenoid polyprenylated acylphloroglucinols possessing 6/6/6 fused tricyclic core, were isolated from Hypericum elodeoides Choisy. Their gross structures were elucidated by HRESIMS and NMR data. The absolute configurations of hyperelodiones A-C were assigned by their calculated and compared electronic circular dichroism (ECD) spectra combined with their common biosynthetic origin. A fluorescence quenching assay suggested that hyperelodiones A-C could bind to RXRα-LBD, whereas hyperelodione C showed the strongest interaction with a KD of 12.81 μΜ. In addition, hyperelodiones A-C dose-dependently inhibited RXRα transactivation and the growth of HeLa and MCF-7 cells. Among them, hyperelodione C showed the most potent inhibitory activities and dose-dependent PARP cleavage. Molecular docking results suggested that hyperelodione C showed a different interaction mode compared with hyperelodione A and hyperelodione B. Thus, hyperelodione C can be considered as a promising lead compound for cancer therapy, which can bind to RXRα-LBD and induce HeLa and MCF-7 cell apoptosis.

Physapubescin I from husk tomato suppresses SW1990 cancer cell growth by targeting kidney-type glutaminase

Kidney-type glutaminase (KGA), catalyzing the hydrolysis of glutamine to glutamate for energy supply, is over-expressed in many cancers and has been regarded as a new therapeutic target for cancers. Physapubescin I was isolated from the fruits of the edible herb Physalis pubescens L., commonly named as “husk tomato or hairy groundcherry”, and was predicted to be a potential KGA inhibitor through structure-based virtual ligand screening. Enzyme inhibition assays, microscale thermophoresis (MST) and cellular thermal shift assay (CETSA) experiments have demonstrated the high efficiency and specificity of physapubescin I targeting KGA. EdU proliferation, Hoechst 33258 staining and cytotoxicity assays indicated that physapubescin I could inhibit cancer cell proliferation and promote apoptosis more effectively than the known KGA inhibitor, BPTES. Knockdown of KGA by siRNA reduced the inhibition of physapubescin I to SW1990 cells. Meanwhile, physapubescin I impaired glutamine metabolism in SW1990 cells with increasing intracellular level of glutamine, and correspondingly decreasing glutamate and its downstream metabolites, which may account for its inhibition of cancer cell proliferation and proapoptosis. Physapubescin I also showed significant tumor growth inhibition and low toxicity in a SW1990 xenograft mouse model. Collectively, physapubescin I may serve as a potential drug candidate or lead compound for cancer therapy by targeting KGA.

Design, synthesis and biological evaluation of novel phthalazinone acridine derivatives as dual PARP and Topo inhibitors for potential anticancer agents

In this study, we designed and synthesized a series of phthalazinone acridine derivatives as dual PARP and Topo inhibitors. MTT assays indicated that most of the compounds significantly inhibited multiple cancer cells proliferation. In addition, all the compounds displayed Topo II inhibition activity at 10mol/L, and also possessed good PARP-1 inhibitory activities. Subsequent mechanistic studies showed that compound 9a induced remarkable apoptosis and caused prominent S cell cycle arrest in HCT116 cells. Our study suggested that 9a inhibiting Topo and PARP concurrently can be a potential lead compound for cancer therapy.

Prenylated xanthones from Metaxya rostrata suppress FoxM1 and induce active cell death by distinct mechanisms

BackgroundMetaxya rostrata C.Presl (Metaxyaceae) is a tree fern widespread in Central and South America and the dried rhizome is used in ethnic medicine against intestinal ulcers or tumors. An activity-guided isolation resulted in two structurally related xanthones: 2-deprenyl-rheediaxanthone B (XB) and 2-deprenyl-7-hydroxy-rheediaxanthone B (OH-XB). Hypothesis/PurposeThis study analyzed the cytotoxic activity and underlying cellular mechanisms of OH-XB for the first time in comparison to XB. MethodsWe exposed the colorectal cancer cell line SW480 and F331 fibroblasts to XB and OH-XB and determined cell viability by neutral red uptake and nuclear morphology by staining with Hoechst dye. Cell cycle distribution and the mechanism of cell death were analyzed by FACS and western blot. Knockdown of FoxM1 expression was performed with siRNA. ResultsOH-XB was at least as cytotoxic as XB in the induction of cell cycle arrest and active cell death. While both compounds strongly inhibited the transcription factor FoxM1, the cellular mechanisms of growth arrest and cell death induction differed widely: OH-XB induced S-phase cell cycle arrest in contrast to a G2-M-phase arrest by XB. It caused morphological modifications typical for classical apoptosis with increased caspase 7 activity and enhanced cleavage of PARP, while XB caused caspase 2 activation and mitotic catastrophe. After knockdown of FoxM1 expression no induction of caspase activity could be observed. ConclusionIn summary, our data clearly showed that XB and OH-XB are promising new lead compounds for cancer therapy with distinct cellular mechanisms. Both compounds are candidates for further pre-clinical and clinical investigations.

Anti-Angiogenic Activity of Rotenoids from the Stems of Derris trifoliata.

The plants in the genus Derris have proven to be a rich source of rotenoids, of which cytotoxic effect against cancer cells seem to be pronounced. However, their effect on angiogenesis playing a crucial role in both cancer growth and metastasis has been seldom investigated. This study aimed at investigating the effect of the eight rotenoids (1: -8: ) isolated from Derris trifoliata stems on three cancer cells and angiogenesis. Among them, 12a-hydroxyrotenone (2: ) exhibited potent inhibition on both cell growth and migration of HCT116 colon cancer cells. Further, anti-angiogenic assay in an ex vivo model was carried out to determine the effect of the isolated rotenoids on angiogenesis. Results revealed that 12a-hydroxyrotenone (2: ) displayed the most potent suppression of microvessel sprouting. The in vitro assay on human umbilical vein endothelial cells was performed to determine whether compound 2: elicits anti-angiogenic effect and its effect was found to occur via suppression of endothelial cells proliferation and tube formation, but not endothelial cells migration. This study provides the first evidence that compound 2: could potently inhibit HCT116 cancer migration and anti-angiogenic activity, demonstrating that 2: might be a potential agent or a lead compound for cancer therapy.

(±)‐Peharmaline A: A Pair of Rare β‐Carboline–Vasicinone Hybrid Alkaloid Enantiomers from Peganum harmala

(±)‐Peharmaline A (1), a pair of rare β‐carboline–vasicinone hybrid alkaloid enantiomers with the hitherto unknown hybrid dimeric system, was isolated from the seeds of Peganum harmala L. Their structures, including absolute configurations, were determined by extensive spectroscopic analyses and electronic circular dichroism (ECD) calculations. Plausible biogenetic pathways involving Mannich/Pictet–Spengler‐type and intermolecular Michael addition reactions are briefly discussed. Compound 1 exhibited significant cytotoxic activities against HL‐60, PC‐3, and SGC‐7901 cancer cell lines with median inhibitory concentration values of 9.2, 21.6, and 25.4 µm, respectively. However, two biosynthetically related precursors, harmaline and vasicinone, were inactive. This cytotoxic β‐carboline–vasicinone hybrid dimeric alkaloid may give some insight into the discovery of new lead compounds for cancer therapy.

Abstract 2171: Beta-hairpin peptide hydrogels as scaffolds for 3D high-throughput cancer drug discovery

Abstract High-throughput screening (HTS) remains a promising initial step in discovering novel lead compounds for cancer therapy, but its value is limited by the poor predictability of clinical effectiveness of candidate compounds. One compelling reason for this lack of reliability to predict in vivo efficacy is the fact that most HTS is done using traditional two-dimensional (2D) cell cultures. While 2D cultures are convenient and can easily be automated, compelling evidence suggests that cells cultured in these non-physiological conditions differ from cells grown in the more in vivo like three-dimensional (3D) systems that better mimic microenvironments. Thus, a 3D culture model is expected to be a better platform for cancer drug discovery. Here we demonstrate the feasibility of a beta-hairpin hydrogel as a novel platform for 3D HTS. MAX8 forms a bonded fibrillar hydrogel network under physiological conditions and moreover, due to its unique shear-thinning abilities can be incorporated into standard HTS equipment. MAX8 is biocompatible with a variety of cancer cell lines, can be tuned for porosity, permeability and stiffness, and can be functionalized with common and cell-type specific ligands to more closely resemble an in vivo-like tumor environment. Using medulloblastoma cells that are known to display more immature, tumor-like features in 3D and that were automatically dispensed onto 384-well plates we have developed a robust assay to measure cell viability on a HTS platform that will have broad applicability for other cancers for which 3D HTS is desirable. Citation Format: Peter Worthington, Katherine M. Drake, Andrew D. Napper, Darrin J. Pochan, Sigrid A. Langhans. Beta-hairpin peptide hydrogels as scaffolds for 3D high-throughput cancer drug discovery. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2171.

Synthesis of Pelorol and Its Analogs and Their Inhibitory Effects on Phosphatidylinositol 3-Kinase

There are numerous biologically active substances with novel structures and unique physiological functions in marine organisms. These substances are important sources of new lead compounds. Pelorol is a natural product isolated from marine organisms that possesses a novel structure with high bioactivity. In this paper, the synthesis of pelorol has been completed, and the synthesis of some intermediates has been optimized and scaled up. Five pelorol analogs have also been prepared. Preliminary biological activity testing demonstrated that compounds 5 and 6 might be potential lead compounds for cancer therapy.

Selected Secondary Plant Metabolites for Cancer Therapy

Secondary plant metabolites reveal numerous biological activities making them attractive as resource for drug development of human diseases. As the majority of cancer drugs clinically established during the past half century is derived from nature, cancer researchers worldwide try to identify novel natural products as lead compounds for cancer therapy. Natural products are considered as promising cancer therapeutics, either as single agents or in combination protocols, to enhance the antitumor activity of additional therapeutic modalities. Most natural compounds exert pleotrophic effects and modulate various signal transduction pathways. A better understanding of the complex mechanisms of action of natural products is expected to open new perspectives in coming years for their use alone or in combination therapies in oncology. Two major strategies to identify novel drug candidates from nature are the bioactivity-guided fractionation of medicinal plant extracts to isolate cytotoxic chemicals and the identification of small molecules inhibiting specific targets in cancer cells. In the present review, we report on our own efforts to unravel the molecular modes of action of phytochemicals in cancer cells and focus on resveratrol, betulinic acid, artesunate, dicentrine and camptothecin derivatives.

RETRACTED ARTICLE: Jacarelhyperol A induced apoptosis in leukaemia cancer cell through inhibition the activity of Bcl-2 proteins

BackgroundHypericum japonicum Thunb. ex Murray is widely used as an herbal medicine for the treatment of hepatitis and tumours in China. However, the molecular mechanisms of its effects are unclear. Our previous research showed that extracts of H. japonicum can induce apoptosis in leukaemia cells. We also previously systematically analysed and isolated the chemical composition of H. japonicum.MethodsThe fluorescence polarisation experiment was used to screen for inhibitors of Bcl-2 proteins which are proved as key proteins in apoptosis. The binding mode was modelled by molecular docking. We investigated the proliferation attenuating and apoptosis inducing effects of active compound on cancer cells by MTT assay and flow cytometry analysis. Activation of caspases were tested by Western blot. A broad-spectrum caspase inhibitor Z-VAD-FMK was used to investigate the caspases-dependence. In addition, co-immunoprecipitation was performed to analyse the inhibition of heterodimerization between anti-apoptotic Bcl-2 proteins with pro-apoptotic proteins. Moreover, in vivo activity was tested in a mouse xenograph tumour model.ResultJacarelhyperol A (Jac-A), a characteristic constituent of H. japonicum, was identified as a potential Bcl-2 inhibitor. Jac-A showed binding affinities to Bcl-xL, Bcl-2, and Mcl-1 with Ki values of 0.46 μM, 0.43 μM, and 1.69 μM, respectively. This is consistent with computational modelling results, which show that Jac-A presents a favorable binding mode with Bcl-xL in the BH3-binding pocket. In addition, Jac-A showed potential growth inhibitory activity in leukaemia cells with IC50 values from 1.52 to 6.92 μM and significantly induced apoptosis of K562 cells by promoting release of cytochrome c and activating the caspases. Jac-A also been proved that its effect is partly caspases-dependent and can disrupt the heterodimerization between anti-apoptotic Bcl-2 proteins with pro-apoptotic proteins. Moreover, Jac-A dose-dependently inhibited human K562 cell growth in a mouse xenograph tumour model with low toxicity.ConclusionIn this study, a characteristic constituent of H. japonicum, Jac-A, was shown to induce apoptosis in leukaemia cells by mediating the Bcl-2 proteins. Therefore, we propose a new lead compound for cancer therapy with a low toxicity, and have provided evidence for using H. japonicum as an anti-cancer herb.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-689) contains supplementary material, which is available to authorized users.

2-Deprenyl-Rheediaxanthone B Isolated from Metaxya rostrata Induces Active Cell Death in Colorectal Tumor Cells

Metaxya rostrata C. Presl (Metaxyaceae) is a common tree fern in Central and South America that is used for the treatment of intestinal ulcers and tumours in ethnic medicine. Using a bioactivity-guided strategy 2-deprenyl-rheediaxanthone B (XB) has been isolated as one of the active principles in this plant. XB induced loss of cell viability in colorectal cancer cell lines at IC50 concentrations of 11–23 µM. This was caused by both accumulation of cells in the G2- and S-phase as well as by induction of active cell death in a time and concentration-dependent manner. Cells exposed to XB were incapable of undergoing regular mitosis due to down-regulation of FoxM1 and absence of chromosome condensation. The apoptosis-related proteins Bcl2 and Bclxl were up-regulated so that Caspase 3 was not activated and classical apoptosis was not observed. However, XB triggered damage pathways down-stream of ATR and activated Caspase 2 causing cell death by a mechanism similar to mitotic catastrophe. Our observations are the first to show the cytotoxic activity of 2-deprenyl-rheediaxanthone B and indicate that XB is an interesting new lead compound for cancer therapy that merits further development.

Synthesis and evaluation of nicotinamide derivative as anti-angiogenic agents

Previously, we have found that BRN-103, a nicotinamide derivative, inhibits vascular endothelial growth factor (VEGF)-mediated angiogenesis signaling in human endothelial cells. During our continuous efforts to identify more potent anti-angiogenic agents, we synthesized various nicotinamide derivatives and evaluated their anti-angiogenic effects. We found that 2-{1-[1-(6-chloro-5-fluoropyrimidin-4-yl)ethyl]piperidin-4-ylamino}-N-(3-chlorophenyl) pyridine-3-carboxamide (BRN-250) significantly inhibited human umbilical vascular endothelial cells (HUVECs) proliferation, migration, tube formation, and microvessel growth in a concentration range of 10–100nM. Furthermore, BRN-250 inhibited the VEGF-induced phosphorylation and intracellular tyrosine kinase activity of VEGF receptor 2 (VEGFR2) and the activation of its downstream AKT pathway. Taken together, these findings suggest that BRN-250 be considered a potential lead compound for cancer therapy.

Apoptotic events induced by synthetic naphthylchalcones in human acute leukemia cell lines

Acute leukemia is a disorder of the hematopoietic system characterized by the expansion of a clonal population of cells blocked from differentiating into mature cells. Recent studies have shown that chalcones and their derivatives induce apoptosis in different cell lines. Since new compounds with biological activity are needed, the aim of this study was to evaluate the cytotoxic effect of three synthetic chalcones, derived from 1-naphthaldehyde and 2-naphthaldehyde, on human acute myeloid leukemia K562 cells and on human acute lymphoblastic leukemia Jurkat cells. Based on the results, the most cytotoxic compound (A1) was chosen for further analysis in six human acute leukemia cells and in a human colon adenocarcinoma cell line (HT-29). Chalcone A1 significantly reduced the cell viability of K562, Jurkat, Kasumi, U937, CEM and NB4 cells in a concentration and time-dependent manner when compared with the control group (IC50 values between ∼1.5μM and 40μM). It was also cytotoxic to HL-29 cells. To further examine its effect on normal cells, peripheral blood lymphocytes collected from healthy volunteers were incubated with the compound. It has also been incubated with human fibroblasts cultured from bone marrow (JMA). Chalcone A1 is non-cytotoxic to PBL cells and to JMA cells. A1 caused significant cell cycle arrest in all phases according to the cell line, and increased the proportion of cells in the sub G0/G1 phase. To evaluate whether this chalcone induced cell death via an apoptotic or necrotic pathway, cell morphology was examined using fluorescence microscopy. Cells treated with A1 at IC50 demonstrated the morphological characteristic of apoptosis, such as chromatin condensation and formation of apoptotic bodies. Apoptosis was confirmed by externalization of phosphatidylserine, which was detected by the Annexin V-FITC method, and by DNA fragmentation. The results suggest that chalcone A1 has potential as a new lead compound for cancer therapy.

Selected Approaches for Rational Drug Design and High Throughput Screening to Identify Anti-Cancer Molecules

Structure-based modeling combined with rational drug design, and high throughput screening approaches offer significant potential for identifying and developing lead compounds with therapeutic potential. The present review focuses on these two approaches using explicit examples based on specific derivatives of Gossypol generated through rational design and applications of a cancer-specificpromoter derived from Progression Elevated Gene-3. The Gossypol derivative Sabutoclax (BI-97C1) displays potent anti-tumor activity against a diverse spectrum of human tumors. The model of the docked structure of Gossypol bound to Bcl-XL provided a virtual structure-activity-relationship where appropriate modifications were predicted on a rational basis. These structure-based studies led to the isolation of Sabutoclax, an optically pure isomer of Apogossypol displaying superior efficacy and reduced toxicity. These studies illustrate the power of combining structure-based modeling with rational design to predict appropriate derivatives of lead compounds to be empirically tested and evaluated for bioactivity. Another approach to cancer drug discovery utilizes a cancer-specific promoter as readouts of the transformed state. The promoter region of Progression Elevated Gene-3 is such a promoter with cancer-specific activity. The specificity of this promoter has been exploited as a means of constructing cancer terminator viruses that selectively kill cancer cells and as a systemic imaging modality that specifically visualizes in vivo cancer growth with no background from normal tissues. Screening of small molecule inhibitors that suppress the Progression Elevated Gene-3-promoter may provide relevant lead compounds for cancer therapy that can be combined with further structure-based approaches leading to the development of novel compounds for cancer therapy.