Identification of Novel Human Breast Carcinoma (MDA-MB-231) Cell Growth Modulators from a Carbohydrate-Based Diversity Oriented Synthesis Library

The application of a cell-based growth inhibition on a library of skeletally different glycomimetics allowed for the selection of a hexahydro-2H-furo[3,2-b][1,4]oxazine compound as candidate inhibitors of MDA-MB-231 cell growth. Subsequent synthesis of analogue compounds and preliminary biological studies validated the selection of a valuable hit compound with a novel polyhydroxylated structure for the modulation of the breast carcinoma cell cycle mechanism.

Synthesis and Characterization of a Walnut Peptides-Zinc Complex and Its Antiproliferative Activity against Human Breast Carcinoma Cells through the Induction of Apoptosis

The walnut peptides and zinc ions were combined to generate a walnut peptides-zinc complex (WP1-Zn) with enhanced antiproliferative ability as well as reduced toxicity. The result indicated that Zn ions were successfully combined with WP1 through Zn-N and Zn-O covalent bonds. WP1-Zn compounds exhibited strong antiproliferative ability against the selected human cell lines, especially MCF-7 cells, whose survival rate reduced to 20.02% after exposure to 300 μg/mL of WP1-Zn for 48 h. WP1-Zn inhibited MCF-7 cell proliferation through inducing cell apoptosis and cell cycle arrest. The results indicated that WP1-Zn induced MCF-7 cell apoptosis via the ROS triggered mitochondrial-mediated pathway and cell surface receptor-mediated pathway. Our work is the first attempt to elucidate the synergic effect of novel walnut peptides and Zn and with the hope of better understanding the antiproliferative action of bioactive peptides and a zinc complex and support the potential application of WP1-Zn as a functional food ingredient or complementary medicine.

Enantioselective synthesis of dictyoceratin-A (smenospondiol) and -C, hypoxia-selective growth inhibitors from marine sponge

Total syntheses of (+)-dictyoceratin-C (1) and (+)-dictyoceratin-A (smenospondiol) (2), hypoxia-selective growth inhibitors isolated from marine sponge, were executed. The absolute stereochemistry of the each compound was determined through the enantioselective total syntheses of them. It revealed that the unnatural enantiomers of them also exhibited the hypoxia-selective growth inhibitory activity against human prostate cancer DU-145 cells.

Novel antimitotic activity of 2-hydroxy-4-methoxy-2',3'-benzochalcone (HymnPro) through the inhibition of tubulin polymerization

The natural chalcones and their derivatives exhibit many biological activities, such as anti-inflammatory and antitumoral. However, the precise mechanisms of action of benzochalcone derivatives are currently unknown. Here, a set of benzochalcones was synthesized, and the molecular mechanisms underlying inhibition of tumor growth were investigated. Colony-forming assays revealed that among tested compounds, 2-hydroxy-4-methoxy-2',3'-benzochalcone (HymnPro) most effectively inhibited the clonogenicity of Capan-1 human pancreatic cancer cells. HymnPro inhibited cell proliferation in several human solid tumor cell lines and suppressed xenografted tumor growth in nude mice. Mechanistically, HymnPro induced cell cycle arrest at the G2/M phase, followed by an increase in apoptotic cell death. These events were associated with the inhibition of tubulin polymerization through binding of HymnPro to tubulin, leading to the formation of abnormal mono- or multipolar mitotic microtubule structures accompanied by spherical arrangement of multinucleated chromosomes. Furthermore, HymnPro activated caspase-2, caspase-9, caspase-3, and caspase-7 and increased the cleavage of poly(ADP-ribose) polymerase (PARP). HymnPro increased the phosphorylation of JNK1/2, Erk1/2, and p38 kinase. Pretreatment with SP600125, U0126, or SB600125 abrogated HymnPro-induced activation of caspases-3 and caspase-7 and the cleavage of PARP, suggesting that MAPK signalings are involved in HymnPro-induced apoptosis. It was concluded that a novel HymnPro compound exerts antitumor activity by disrupting microtubule assembly, which leads to mitotic arrest and sequential activation of the caspase pathway, resulting in apoptosis.

Synthesis and biological activity of optically active NCL-1, a lysine-specific demethylase 1 selective inhibitor

Optically active (1S,2R)-NCL-1 and (1R,2S)-NCL-1 were synthesized and evaluated for their lysine-specific demethylase 1 inhibitory activity and cell growth inhibitory activity. In enzyme assays, the (1S,2R)-isomer was approximately four times more potent than the (1R,2S)-isomer. In cell growth inhibition assays, the two isomers showed similar activity in HEK293 cells and SH-SY5Y cells, whereas the (1S,2R)-isomer showed approximately four times more potent activity than the (1R,2S)-isomer in HeLa cells.

[The influence of potassium 4-toluenethiosulfonate on membrane potential and ATPase activity of plasmatic membranes of loach embryos]

The influence of novel biologically active substance potassium 4-toluenethiosulfonate in concentration of 4 x 10(-5) M on the changes of electrophysiological parameters of embryonic cells in early development of fish (Misgurnus fossilis L.) was investigated including the changes of membrane potential (TMP) and enzyme activity of plasmatic membranes of loach embryos during the period of synchronous division of blastomers in the early period of development. The evaluation of influence of these matters was studied and aperiodic changes of the level of TMP were shown. The diminishing of amplitude in every period by 7/12 mV and diminishing of growth of maximal values of vibrations of TMP by 39 mV in comparison to control was noticed. It was related to inhibition of some biosynthetic processes and results in the decline of activity of membrane enzyme (Na+, K(+)-ATPase) by 75.5 +/- 4.1% and 78.4 +/- 10.4% both at the action of high (4 x 10(-3) M) and low (4 x 10(-9) M) concentrations, accordingly, at first hours of development with subsequent renewal of its activity to the level of control only for the actions of low concentration.

3,5,3',4',5'-pentamethoxystilbene (MR-5), a synthetically methoxylated analogue of resveratrol, inhibits growth and induces G1 cell cycle arrest of human breast carcinoma MCF-7 cells

3,5,3',4',5'-pentamethoxystilbene (MR-5) is a synthetically methoxylated analogue of resveratrol and has been suggested to have antitumor activity because of structural similarity to resveratrol. Herein, we investigate the antiproliferative effect of MR-5 in human breast cancer MCF-7 cells and demonstrate that MR-5 had a more potent inhibition on cell growth compared with resveratrol and other methoxylated derivatives. Exploring the growth-inhibitory mechanisms of MR-5, we found that it is accompanied by G1 cell cycle arrest, which coincides with a marked inhibition of G1 cell cycle regulatory proteins, including decreased cyclins (D1/D3/E) and cyclin-dependent kinases (CDK2/4/6) and increased CDK inhibitors (CKIs) such as p15, p16, p21, and p27. Furthermore, the increase in CKI levels by MR-5 resulted in a concomitant increase in their interactions of CDK4 and CDK2, along with a strong inhibition in CDK4 kinase activity and the accumulation of hypophosphorylated Rb. MR-5 also modulated some critical kinase activities related to cell cycle regulation, including Akt, mitogen-activated protein kinase (ERK1/2), p38 mitogen-activated protein kinase (p38 MAPK), and focal adhesion kinase (FAK) in MCF-7 cells. In total, our results demonstrate that MR-5 affects multiple cellular targets that contribute to its antiproliferative activity in MCF-7 cells and provide novel information for synthetic chemists to design new antitumor agents with introduction of methoxylated group(s) in the basic compound.

Synthesis and evaluation of aniline headgroups for alkynyl thienopyrimidine dual EGFR/ErbB-2 kinase inhibitors

Aniline 'headgroups' were synthesized and incorporated into an alkynyl thienopyrimidine series of EGFR and ErbB-2 inhibitors. Potent inhibition of enzyme activity and cellular proliferation was observed. In certain instances, protein binding was reduced and oral exposure was found to be somewhat improved relative to compounds containing the reference aniline.

Design and synthesis of 7-alkoxy-4-heteroarylamino-3-quinolinecarbonitriles as dual inhibitors of c-Src kinase and nitric oxide synthase

Because both c-Src and iNOS are key regulatory enzymes in tumorigenesis, a new series of 4-heteroarylamino-3-quinolinecarbonitriles as potent dual inhibitors of both enzymes were designed, prepared, and evaluated for blocking multiple signaling pathways in cancer therapy. All compounds were evaluated by two related enzyme inhibition assays and an anti-proliferation assay in vitro. The results showed that most compounds could inhibit both enzymes, and several of them showed potent inhibition activity against different cancer cell lines. The best compound 20 (CPU-Y020) showed the IC(50) values of 6.58 and 7.61microM toward colon cancer HT-29 and liver cancer HepG2 cell lines.

In vivo disruption of T cell development by expression of a dominant-negative polypeptide designed to abolish the SLP-76/Gads interaction

Multi-molecular complexes nucleated by adaptor proteins play a central role in signal transduction. In T cells, one central axis consists of the assembly of several signaling proteins linked together by the adaptors linker of activated T cells (LAT), Src homology 2 domain-containing leukocyte-specific phosphoprotein of 76 kDa (SLP-76), and Grb2-related adaptor downstream of Shc (Gads). Each of these adaptors has been shown to be important for normal T cell development, and their proper sub-cellular localization is critical for optimal function in cell lines. We previously demonstrated in Jurkat T cells and a rat basophilic leukemic cell line that expression of a 50-amino acid polypeptide identical to the site on SLP-76 that binds to Gads blocks proper localization of SLP-76 and SLP-76-dependent signaling events. Here we extend these studies to investigate the ability of this polypeptide to inhibit TCR-induced integrin activity in Jurkat cells and to inhibit in vivo thymocyte development and primary T cell function. These data provide evidence for the in vivo function of a dominant-negative peptide based upon the biology of SLP-76 action and suggest the possibility of therapeutic potential of targeting the SLP-76/Gads interaction.

Peptide vaccines of the HER-2/neu dimerization loop are effective in inhibiting mammary tumor growth in vivo

Human epidermal growth factor receptor-2 (HER-2)/neu (ErbB2), a member of the epidermal growth factor family of receptors, is overexpressed in 20-30% of breast cancers. It is an attractive target for receptor-directed antitumor therapy using mAbs. Unlike other epidermal growth factor receptor family members, HER-2/neu does not bind a high-affinity ligand, but rather functions as the preferred dimerization partner. Pertuzumab (Omnitarg) is a humanized mAb directed against the HER-2/neu dimerization domain that inhibits receptor signaling. The recent definition of the crystal structure of the HER-2/neu-pertuzumab complex demonstrated that the receptor dimerization region encompassed residues 266-333. Based on the three-dimensional structure of the complex, we have designed three conformational peptide constructs (sequences 266-296, 298-333, and 315-333) to mimic regions of the dimerization loop of the receptor and to characterize their in vitro and in vivo antitumor efficacy. All the constructs elicited high-affinity peptide Abs that inhibited multiple signaling pathways including HER-2/neu-specific inhibition of cellular proliferation and cytoplasmic receptor domain phosphorylation. All the peptide Abs showed Ab-dependent cellular cytotoxicity to varying degrees with the 266-296 constructs being equally effective as compared with Herceptin. The 266-296 peptide vaccine had statistically reduced tumor onset in both transplantable tumor models (FVB/n and BALB/c) and significant reduction in tumor development in two transgenic mouse tumor models (BALB-neuT and VEGF(+/-)Neu2-5(+/-)). The 266-296 construct represents the most promising candidate for antitumor vaccination and could also be used to treat a variety of cancers with either normal or elevated expression of HER-2 including breast, lung, ovarian, and prostate.

Chemically synthesized sugar-cholestanols possess a preferential anticancer activity involving promising therapeutic potential against human esophageal cancer

The understanding of the cell signaling pathways and the molecular events leading to cell death of cancer cells will provide in-depth perspective into the identification and development of potent anticancer agents. A balance between cell proliferation and cell death has been raised as a rational target for the management of malignant tumors. In the present study, the authors demonstrated that chemically synthesized sugar-cholestanols consisting of GlcNAcbeta-, Galbeta- and GlcNAcbeta1,3Galbeta-cholestanols exerted a strong inhibiting activity against cell proliferation of esophageal cancer cells, but cholestanol itself did not show such an activity against the same cancer cells at all. In addition to their predominant role as an antiproliferation agent, evidence based on the molecular analyses suggested that sugar-cholestanols played a regulatory role in multiple signal transduction pathways inducing apoptosis through both the death signal-extrinsic and the mitochondria-intrinsic pathways. Sugar-cholestanols seemed to be more susceptible to esophageal cancer cells than to non-cancerous esophageal cells at the very early event of their exposure and, further, to suppress specifically the expression of vascular endothelial growth factor. Taken together, these novel functions of sugar-cholestanols indicate that they could have promising therapeutic potential against human esophageal cancer.

6-Substituted Pyrrolo[3,4-c]pyrazoles: An Improved Class of CDK2 Inhibitors

We have recently reported a new class of CDK2/cyclin A inhibitors based on a bicyclic tetrahydropyrrolo[3,4-c]pyrazole scaffold. The introduction of small alkyl or cycloalkyl groups in position 6 of this scaffold allowed variation at the other two diversity points. Conventional and polymer-assisted solution phase chemistry provided a way of generating compounds with improved biochemical and cellular activity. Optimization of the physical properties and pharmacokinetic profile led to a compound which exhibited good efficacy in vivo on A2780 human ovarian carcinoma.

Synthesis, Structure, and Anticancer Activity of Gallium(III) Complexes with Asymmetric Tridentate Ligands: Growth Inhibition and Apoptosis Induction of Cisplatin-Resistant Neuroblastoma Cells

Five gallium(III) complexes described as [Ga(III)(LX)2]ClO4, where (LX)- is the deprotonated form of a series of asymmetric ligands containing pyridine and 4,6-substituted phenol moieties, were synthesized and characterized by spectroscopic and spectrometric methods. Phenol substituents encompass the electron-withdrawing and electron-donating methoxy (1), nitro (2), chloro (3), bromo (4), and iodo (5) groups. Complexes 1 and 3 have had their molecular structure solved by X-ray crystallography and show distinct coordination modes. Complexes 1-5 were tested for growth-inhibition activity on cisplatin-resistant human neuroblastoma cells; those containing halogen substituents on the phenolate rings, i.e., 3-5, showed activity superior to that observed for cisplatin and induced apoptosis of neuroblastoma cells. Nitro-containing 2 suppressed proliferation of the neuroblastoma cells but induced apoptosis less effectively.

Synthesis andin vitro-Anticancer and Antimicrobial Evaluation of Some Novel Quinoxalines Derived from 3-Phenylquinoxaline-2(1H)-thione

Two novel series derived from 3-phenylquinoxaline-2(1H)-thione 2 and 2-(hydrazinocarbonylmethylthio)-3-phenylquinoxaline 6 have been synthesized. Eight out of twenty six new compounds were selected at the National Cancer Institute for evaluation of their in vitro-anticancer activity. Among them, compounds 3b, 3c, 4b, and 4c displayed moderate to strong growth inhibition activity against most of the tested sub-panel tumor cell lines with GI(50) 10(-5) to 10(-6 )molar concentrations. Compound 4b exhibited a significant value of percent tumor growth inhibition against breast cancer at concentration < 10(-8) M. Compound 4c showed moderate selectivity towards leukemia cell lines with GI(50) of 1.8 to 3.8 microM (selectivity ratio = 5.7). Preliminary antimicrobial testing revealed that compounds 7a, 7b, 8a, 11a, and 11b were as active as ampicillin against B. subtilis (MIC = 12.5 microg/mL). Compounds 7b and 8a were also nearly as active as ampicillin against E. coli (MIC = 12.5 microg/mL). In addition, compounds 4a, 7b, 10b, and 11a were as active as ampicillin against P. aerugenosa (MIC = 50 microg/mL). However, compounds 7b, 8a, and 10b showed mild activity against C. albicans (MIC = 50 microg/mL). The values of minimum bactericidal concentrations indicated that compounds 4a and 7b were bactericidal against B. subtilis and P. aerugenosa, respectively, while compound 10b was bactericidal against both organisms. However, compound 11a was bactericidal against E. coli, P. aerugenosa, and S. aureus.

Directed Ortho-Metalation of Unprotected Benzoic Acids. Methodology and Regioselective Synthesis of Useful Contiguously 3- and 6-Substituted 2-Methoxybenzoic Acid Building Blocks

[reaction: see text] By treatment with s-BuLi/TMEDA at -78 degrees C, unprotected 2-methoxybenzoic acid is deprotonated exclusively in the position ortho to the carboxylate. A reversal of regioselectivity is observed when the acid is treated with n-BuLi/t-BuOK. These results are of general utility for the one-pot preparation of a variety of very simple 3- and 6-substituted 2-methoxybenzoic acids that are not easily accessible by conventional means. The potential usefulness of the method is demonstrated by the expedient synthesis of lunularic acid.

Microtubule disassembly and inhibition of mitosis by a novel synthetic pharmacophore

Microtubule drugs, which block cell cycle progression through mitosis, have seen widespread use in cancer chemotherapies. Although microtubules are subject to regulation by signal transduction mechanisms, their pharmacological modulation has so far relied on compounds that bind to the tubulin subunit. A new microtubule pharmacophore, diphenyleneiodonium, causing disassembly of the microtubule cytoskeleton is described here. Although this synthetic compound does not affect the assembly state of purified microtubules, it profoundly suppresses microtubule assembly in vivo, causes paclitaxel-stabilized microtubules to cluster around the centrosomes, and selectively disassembles dynamic microtubules. Similar to other microtubule drugs, this new pharmacophore blocks mitotic spindle assembly and mitotic cell division.

Synthesis and comparative molecular field analysis (CoMFA) of argentatin B derivatives as growth inhibitors of human cancer cell lines

Synthesis, characterization, anticancer activity, and comparative molecular field analysis (CoMFA) of 14 argentatin B (1) analogs are described. The effect of argentatin B derivatives on the growth of K562 (leukemia), PC-3 (prostate), U251 (CNS), and HCT-15 (colon) human cancer cell lines was determined using the sulforhodamine B test. The most active compound in this series, 2-formyl-(16beta,24R)-16,24-epoxy-25-hydroxycycloart-1-en-3-one (12), was about 35-50 times more potent than argentatin B (1). Structures were built using the X-ray crystallography of six derivatives for 3D modeling with Sybyl6.9. CoMFA of Log (1/IC50) in K562 cell line gave q2 = 0.507, r2 = 0.907, and three components. The standard deviation CoMFA contours indicate that increased activity is associated with a bulky group at C-2, a C1-C2 double bond, and low electronic density at C-25. Experimental Log P values for argentatin B and one derivative were 1-2 Log units more hydrophilic than the calculated CLog P values.

Guanaconetins, new antitumoral acetogenins, mitochondrial complex I and tumor cell growth inhibitors

The antitumoral activity of a series of acetylated bis-tetrahydrofuranic acetogenins with a threo/trans/threo/trans/erythro relative configuration was characterized by four new natural and two semisynthetic, 15,24,30-trioxygenated acetogenins that were found to inhibit mitochondrial complex I enzyme as well as growth of several tumor cell lines. Placement of acetyl groups along the alkyl chain modulated the potency of the bis-tetrahydrofuranic acetogenins and could be important for future utilization of these compounds as chemotherapeutic agents.

The synthetic peptide Trp-Lys-Tyr-Met-Val-D-Met inhibits human monocyte-derived dendritic cell maturation via formyl peptide receptor and formyl peptide receptor-like 2

Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm) has been reported to stimulate monocytes, neutrophils, and dendritic cells (DCs). However, although WKYMVm has been reported to function as a DC chemoattractant, its role on DC maturation has not been examined. In this study, we investigated the effects of WKYMVm on human DC maturation. The costimulation of DCs with WKYMVm and LPS dramatically inhibited LPS-induced IL-12 production, CD86 and HLA-DR surface expression, and DC-mediated T cell proliferation. However, DC phagocytic activity was increased by WKYMVm stimulation. These findings demonstrate that WKYMVm inhibits DC maturation by LPS. In terms of the mechanism underlying DC maturation inhibition by WKYMVm, we found that LPS-induced DC maturation was negatively regulated by WKYMVm-stimulated ERK activity. Moreover, the costimulation of DCs with WKYMVm and LPS dramatically inhibited the LPS-induced accumulations of IL-12 mRNA, thus suggesting that WKYMVm inhibits LPS-induced IL-12 production at the transcriptional level. We also found that DCs express two WKYMVm receptors, formyl peptide receptor (FPR) and FPR-like 2 (FPRL2). In addition, formyl-Met-Leu-Phe (a FPR ligand), Trp-Lys-Tyr-Met-Val-Met, Hp(2-20) peptide, and F2L (three FPRL2 ligands) inhibited LPS-induced IL-12 production in DCs. Taken together, our findings indicate that the activations of FPR and FPRL2 inhibit LPS-induced DC maturation, and suggest that these two receptors should be regarded as important potential therapeutic targets for the modulation of DC maturation.

Synthesis and biological evaluation of quinoxaline-5,8-diones that inhibit vascular smooth muscle cell proliferation

A series of 6-arylamino-2,3-bis(pyridin-2-yl)-7-chloro-quinoxaline-5,8-diones were synthesized and evaluated for their inhibitory activity on the rat aortic smooth muscle cell (RAoSMC) proliferation. The quinoxaline-5,8-diones exhibited a potent antiproliferative activity. Further mechanistic study revealed that the inhibitory effect of one representative quinoxaline-5,8-dione on SMC proliferation was mediated by modulation of the extracellular signal-regulated kinase 1/2 signaling pathway in the RAoSMCs.

Synthesis and biological evaluation of benzimidazole-4,7-diones that inhibit vascular smooth muscle cell proliferation

A series of 6-arylamino-5-chloro-benzimidazole-4,7-diones were synthesized and tested for their inhibitory activity on the rat aortic smooth muscle cell (RAoSMC) proliferation. Among them, 6-arylamino-5-chloro-2-methyl-benzimidazole-4,7-diones exhibited potent antiproliferative activity. Benzimidazole-4,7-dione 2c activated SAPK/JNK signaling pathway in the RAoSMCs.

Preparation of 2-Pyridone-Containing Tricyclic Alkaloid Derivatives as Potential Inhibitors of Tumor Cell Proliferation by Regioselective Intramolecular N- and C-Acylation of 2-Pyridone

A novel and practical preparation of 2-pyridone-containing tricyclic alkaloid derivatives was developed. By regioselective intramolecular N- and C-acylation of 2-(4-aryl-2-pyridon-6-yl)benzoic acid, a pair of structural isomers 2-aryl pyrido[2,1-a]isoindole-4,6-diones and 4-aryl 1-methyl-1H-indeno[1,2-b]-pyridine-2,5-diones, as potential inhibitors of tumor cell proliferation, were prepared respectively.

Synthesis and cytotoxicity of substituted 2-benzylnaphth[2,3-d]imidazoles

Designed as a new series of so called "bivalent ligand" containing the proposed 2-benzylnaphthimidazole-type structure, a number of 2-benzylnaphth[2,3-d]imidazoles, bearing various substituents, have been prepared by a synthetic approach involving an heterocyclization of 2,3-diaminonaphthalene 4 with appropriate imidates 3 (for 1b-i) followed by alkylation (for 1j-l) with the desired alkylating agent. Compounds 1b-f, h-l were subjected to primary biological evaluation for cancer cell growth inhibition (one-dose, three-cell assay), and the four most active terms, 1c, h, i and j, were then evaluated for their cytotoxic profiles in the National Cancer Institute's (NCI) human disease-oriented, 60 cell line, in vitro antitumor screening protocol. Among them, two compounds (1h and 1i) are the most representatives demonstrating not only high growth-inhibitory activities against some leukemia cancer cells, but also fairly good activities against the growth of certain cell lines of some solid tumors.

Liposomes containing distamycins: preparation, characterization and antiproliferative activity

This article describes the production and characterization of two liposome formulations containing antitumor drugs, namely distamycin A (Dist) and a new alkyl derivative of distamycin A (C16-Dist). Egg-PC/cholesterol liposomes (4:1 mol/mol) were prepared by reverse phase evaporation technique followed by extrusion through polycarbonate filters. The encapsulation efficiency was found to be almost complete for C16-Dist (99.8%), while native distamycin A showed a lower yield (19.0%). The in vitro antiproliferative activity of the distamycins-containing liposomes determined on human leukaemic K562 cells, was 11-fold and 8-fold higher for native and alkyl derivative distamycin A, respectively, compared with that of the corresponding free drugs. Liposomal formulations show an increase in the activity and specificity of distamycins in experimental antitumor therapy.

A nuclear localization sequence endows human pancreatic ribonuclease with cytotoxic activity

Some members of the ribonuclease superfamily, such as Onconase, are cytotoxic to cancer cells. This is not the case for human pancreatic ribonuclease. This lack of cytotoxicity is probably a result of the inhibition exerted by the cytosolic ribonuclease inhibitor once the protein has reached the cytosol. Until now, all cytotoxic human pancreatic ribonuclease variants have been described as being resistant to the inhibitor. Here, we report on the characterization of a cytotoxic variant of human pancreatic ribonuclease which has an Arg triplet introduced onto one of its surface-exposed loops. Despite its sensitivity to the inhibitor, this variant, called PE5, was only 5-15 times less cytotoxic than Onconase. When it was taken up by cells, it was only observed within late compartments of the endocytic pathway, probably because the number of molecules transported to the cytosol was too small to allow their visualization. Nuclear import assays showed that the Arg triplet endows PE5 with a nuclear localization signal. In these experiments, PE5 was efficiently transported to the nucleus where it was initially localized in the nucleolus. Although the Arg introduction modified the net charge of the protein and somehow impaired recognition by the cytosolic inhibitor, control variants, which had the same number of charges or were not recognized by the inhibitor, were not toxic. We concluded that targeting a ribonuclease to the nucleus results in cytotoxicity. This effect is probably due to ribonuclease interference with rRNA processing and ribosome assembly within the nucleolus.

Pseudosubstrate peptides inhibit Akt and induce cell growth inhibition

We have designed peptide inhibitors that potently inhibit Akt both in vitro and inside cells. These peptide inhibitors are selective for Akt versus other closely related kinases. The peptides inhibit the in vitro phosphorylation of a biotinylated Bad peptide by Akt with potency up to 100 nM. We have shown that the binding between Akt1 and these peptide inhibitors requires MgATP. Mutating the two putative Akt phosphorylation sites to Ala (nonsubstrate) in these peptides increases the inhibitory potency while mutating the sites to aspartic acid (phosphorylation mimetic) reduces the potency. When delivered into cells, these peptide inhibitors can inhibit cellular Akt activity and cell growth. Thus, these Akt-specific peptide inhibitors provide prototypes for peptide mimetic drugs as well as very useful tools to dissect cellular functions of Akt.

Synthesis of 1,7-annulated indoles and their applications in the studies of cyclin dependent kinase inhibitors

The synthesis of a novel series of 1,7-annulated indolocarbazoles 2 and 16 is described. These compounds were found to be potent cyclin dependent kinase inhibitors with good antiproliferative activity against two human carcinoma cell lines. These inhibitors also arrested tumor cells at the G1 phase and inhibited pRb phosphorylation.

Fusion of Two Malaria Vaccine Candidate Antigens Enhances Product Yield, Immunogenicity, and Antibody-Mediated Inhibition of Parasite Growth In Vitro

A Plasmodium falciparum chimeric protein 2.9 (PfCP-2.9) was constructed consisting of the C-terminal regions of two leading malaria vaccine candidates, domain III of apical membrane ag-1 (AMA-1) and 19-kDa C-terminal fragment of the merozoite surface protein 1 (MSP1). The PfCP-2.9 was produced by Pichia pastoris in secreted form with a yield of 2600 mg/L and approximately 1 g/L of final product was obtained from a three-step purification process. Analysis of conformational properties of the chimeric protein showed that all six conformational mAbs interacted with the recombinant protein were reduction-sensitive, indicating that fusion of the two cysteine-rich proteins retains critical conformational epitopes. PfCP-2.9 was found to be highly immunogenic in rabbits as well as in rhesus monkeys (Macaca mulatta). The chimeric protein induced both anti-MSP1-19 and anti-AMA-1(III) Abs at levels 11- and 18-fold higher, respectively, than individual components did. Anti-PfCP-2.9 sera from both rabbits and rhesus monkeys almost completely inhibited in vitro growth of the P. falciparum FCC1/HN and 3D7 lines when tested at a 6.7-fold dilution. It was shown that the inhibition is dependent on the presence of Abs to the chimeric protein and their disulfide bond-dependent conformations. Moreover, the activity was mediated by a combination of growth-inhibitory Abs generated by the individual MSP1-19 and AMA-1(III) of PfCP-2.9. The combination of the extremely high yield of the protein and enhancement of its immune response provides a basis to develop an effective and affordable malaria vaccine.

Synthesis, cytotoxicity, QSAR, and intercalation study of new diindenopyridine derivatives

Seven new derivatives of diindenopyridine were synthesized by Hantsch pyridine synthesis. Their biological activity to inhibit cell proliferation was assessed by MTT assay on seven cell lines. 11-(4-Fluoro-phenyl)-diindeno[1,2-b;2',1'-e]pyridine-10,12-dione and 11-(2-nitro-phenyl)-diindeno[1,2-b;2',1'-e]pyridine-10,12-dione were active on K-562 cell line with IC50 values of 79.66 and 78.2 microM, respectively. Effect of structural parameters on the cytotoxicity was evaluated by quantitative structure activity relationship (QSAR) analysis and a linear relationship was found between the -logIC15 of these compounds and their surface area and molar refractivity. To model the DNA-intercalator complex, force field molecular mechanic calculation was employed and the binding energy of the reaction between the intercalating agent and each reasonable double base pairs of DNA was calculated. It was found that these molecules could intercalate into the DNA. Also, it was observed that 11-(2-nitro-phenyl)-diindeno[1,2-b;2',1'-e]pyridine-10,12-dione, which showed the highest activity in K-562 cell line, produced the most negative binding energy with a moderate selectivity toward A-G/T-C double base pairs.

Synthesis, crystal structure and antiproliferative evaluation of some new substituted benzothiazoles and styrylbenzothiazoles

The multistep synthesis of a series of new substituted-benzothiazoles as hydrochloride or quaternary salts is described. 6-Amidino substituted 2-aminobenzothiazoles (5, 6), N-methyl-2-(4-cyanostyryl)benzothiazolium iodide (8), cyano-substituted-2-styrylbenzothiazoles (9-11) and amidino and bis-amidino-substituted 2-styrylbenzothiazoles (12-17) were prepared. The crystal structure of amidino derivative (6) was determined by single crystal X-ray analysis. All new prepared compounds were tested on the cytostatic activities against malignant cell lines: (SW620, colon carcinoma; Hep2, laryngeal carcinoma; HBL, melanoma; HeLa, cervical carcinoma and WI38, human normal fibroblasts). The compounds exerted a different inhibitory effect, depended on concentration and type of the cells. The best inhibitory effect was achieved with compounds (12-15), with slight differences among them. All of them inhibited the growth of examined tumor cell lines and also normal fibroblasts. Other examined compounds exhibited a moderate inhibitory effect, depending on type of the cells. Majority of them inhibited the growth of HeLa cells and WI38.

Synthesis and biological activities of novel 4″-alkylidene avermectin derivatives

Horner-Emmons reaction of 4"-dehydro-5-O-TBDMS-avermectin B(1a) with a variety of phosphorus ylides using LHMDS gave novel 4"-alkylidene avermectin derivatives in high yields. Further modifications led to derivatives bearing diverse functional groups. The new avermectin derivatives showed potent growth inhibitory activity against Artemia salina and Caenorhabditis elegans.

An antitumor agent of beta-cyclodextrin-modified titanocene complex: synthesis and characterization

The complex of a derivative of beta-cyclodextrin, that is mono[6-deoxy-6-(2-butenedinitrile-2,3-dimercapto sodium salt)]-beta-cyclodextrin (6-mnt-beta-CD), with titanocene (titanocene di[mono[6-deoxy-6-(2-butenedinitrile-2,3-dimercapto)]-beta-cyclodextrin], Cp2Ti[6-mnt-beta-CD]2) has been synthesized and characterized by IR spectroscopy, UV spectroscopy, elemental analysis, thermogravimetry, 1H- and 13C-NMR spectroscopy. The stoichiometry of the target molecule was determined by 1H-NMR spectroscopy and elemental analysis.

T cell costimulus-independent and very efficacious inhibition of tumor growth in mice bearing subcutaneous or leukemic human B cell lymphoma xenografts by a CD19-/CD3- bispecific single-chain antibody construct

We have recently demonstrated that a recombinant single-chain bispecific Ab construct, bscCD19xCD3, in vitro induces rapid B lymphoma-directed cytotoxicity at picomolar concentrations with unstimulated peripheral T cells. In this study, we show that treatment of nonobese diabetic SCID mice with submicrogram doses of bscCD19xCD3 could prevent growth of s.c. human B lymphoma xenografts and essentially cured animals when given at an early tumor stage. The effect was dose dependent, dependent on E:T ratio and the time between tumor inoculation and administration of bscCD19xCD3. No therapeutic effect was seen in the presence of human lymphocytes alone, a vehicle control, or with a bispecific single-chain construct of identical T cell-binding activity but different target specificity. In a leukemic nonobese diabetic SCID mouse model, treatment with bscCD19xCD3 prolonged survival of mice in a dose-dependent fashion. The human lymphocytes used as effector cells in both animal models did not express detectable T cell activation markers at the time of coinoculation with tumor cells. The bispecific Ab therefore showed an in vivo activity comparable to that observed in cell culture with respect to high potency and T cell costimulus independence. These properties make bscCD19xCD3 superior to previously investigated CD19 bispecific Ab-based therapies.

A chimeric multi-human epidermal growth factor receptor-2 B cell epitope peptide vaccine mediates superior antitumor responses

Immunotherapeutic approaches to cancer should focus on novel undertakings that modulate immune responses by synergistic enhancement of antitumor immunological parameters. Cancer vaccines should preferably be composed of multiple defined tumor Ag-specific B and T cell epitopes. To develop a multiepitope vaccine, 12 high ranking B cell epitopes were identified from the extracellular domain of the human epidermal growth factor receptor-2 (HER-2) oncoprotein by computer-aided analysis. Four novel HER-2 B cell epitopes were synthesized as chimeras with a promiscuous T cell epitope (aa 288-302) from the measles virus fusion protein (MVF). Two chimeric peptide vaccines, MVF HER-2(316-339) and MVF HER-2(485-503) induced high levels of Abs in outbred rabbits, which inhibited tumor cell growth. In addition, Abs induced by a combination of two vaccines, MVF HER-2(316-339) and MVF HER-2(628-647) down-modulated receptor expression and activated IFN-gamma release better than the individual vaccines. Furthermore, this multiepitope vaccine in combination with IL-12 caused a significant reduction (p = 0.004) in the number of pulmonary metastases induced by challenge with syngeneic tumor cells overexpressing HER-2. Peptide Abs targeting specific sites in the extracellular domain may be used for exploring the oncoprotein's functions. The multiepitope vaccine may have potential application in the treatment of HER-2-associated cancers.

Anticancer bisquaternary heterocyclic compounds: a ras-ional design

A new family of symmetrical bisquaternary compounds with semirigid linkers have shown to be highly specific for Choline Kinase (ChoK) inhibition and to exert antitumoural activity in cell lines and in mice. A three-parameter regression equation has been derived which satisfactorily describes the ex vivo inhibitory potency of ChoK of the title compounds. The electronic effect of the group at position 4 of the cationic head plays a critical role although the hydrophobic contribution, especially that of the linker, favors the ChoK inhibitory activity. The antiproliferative activity (in vitro assay) is correlated with the ChoK inhibition (ex vivo assay) through the electronic effect and a squared term of the overall lipophilicity of the molecules. We also provide in vivo evidence that ChoK is a novel target for the design of antitumoural drugs. All these results suggest that ChoK plays a crucial role in the onset of carcinogenesis.

Synthesis of potent and selective inhibitors against the proliferation of human coronary artery smooth muscle cells

A series of diarylamide urea derivatives were synthesized and evaluated for their inhibitory activities against human coronary artery smooth muscle cells (SMCs) and human coronary artery endothelial cells (ECs). Compound 2h was much superior to Tranilast, in terms of both the potency of its inhibitory activity toward the proliferation of SMCs and the cell selectivity.

Critical components of a DNA fusion vaccine able to induce protective cytotoxic T cells against a single epitope of a tumor antigen

DNA vaccines can activate immunity against tumor Ags expressed as MHC class I-associated peptides. However, priming of CD8(+) CTL against weak tumor Ags may require adjuvant molecules. We have used a pathogen-derived sequence from tetanus toxin (fragment C (FrC)) fused to tumor Ag sequences to promote Ab and CD4(+) T cell responses. For induction of CD8(+) T cell responses, the FrC sequence has been engineered to remove potentially competitive MHC class I-binding epitopes and to improve presentation of tumor epitopes. The colon carcinoma CT26 expresses an endogenous retroviral gene product, gp70, containing a known H2-L(d)-restricted epitope (AH1). A DNA vaccine encoding gp70 alone was a poor inducer of CTL, and performance was not significantly improved by fusion of full-length FrC. However, use of a minimized domain of FrC, with the AH1 sequence fused to the 3' position, led to rapid induction of high levels of CTL. IFN-gamma-producing epitope-specific CTL were detectable ex vivo and these killed CT26 targets in vitro. The single epitope vaccine was more effective than GM-CSF-transfected CT26 tumor cells in inducing an AH1-specific CTL response and equally effective in providing protection against tumor challenge. Levels of AH1-specific CTL in vivo were increased following injection of tumor cells, and CTL expanded in vitro were able to kill CT26 cells in tumor bearers. Pre-existing immunity to tetanus toxoid had no effect on the induction of AH1-specific CTL. These data demonstrate the power of epitope-specific CTL against tumor cells and illustrate a strategy for priming immunity via a dual component DNA vaccine.

Antisense ferritin oligonucleotides inhibit growth and induce apoptosis in human breast carcinoma cells

BACKGROUND

Ferritin is the major iron-storage protein which sequesters and detoxifies excess iron that is taken up by cells but is not utilized in normal metabolic processes. Human ferritin consists of various combinations of heavy (FerH, Mr 21,000) and light (FerL, Mr 19,000) chains and excess iron leads to an increase in the synthesis of both heavy and light chains.

MATERIALS AND METHODS

In this study four pairs of antisense oligodeoxynucleotides (ODNs) were synthesized: FerH-A1 and FerL-A1 were complementary to the 24-base pair sequence overlapping the starting codons of the FerH and FerL genes, respectively, but the sequences of FerH-A2 and FerL-A2 only covered the coding sequences of the ferritin genes. The corresponding sense chain sequences (FerH-S1, FerH-S2, FerL-S1 and FerL-S2) were used as controls.

RESULTS

Treatment with FerH-S1, FerH-A1, FerH-S2, FerH-A2, FerL-S1, FerL-A1, FerL-S2 and FerL-A2 at 40 microM, 25 microM, 30 microM, 17 microM, 45 microM, 18 microM, 40 microM and 26 microM, respectively, for 72 hours resulted in 50% inhibition of DNA synthesis (IC50) in MCF-7 breast carcinoma cells, as measured by [3H]-thymidine incorporation. FerH chain mRNA, FerL chain mRNA and total ferritin protein levels were significantly decreased by the IC50 concentrations of each of the antisense ODNs but were not inhibited by IC50 concentrations of sense ODNs, as measured by quantitative RT-PCR and microparticle enzyme immunoassay. However, antisense ferritin ODNs had no effect on the total iron concentration in MCF-7 cells. Incubation with IC50 concentrations of antisense ferritin ODNs caused reduction in cell volume, condensation of nuclear structures and lower levels of Bcl-2 mRNA and protein compared to control cells, but Bax mRNA and protein levels remained unchanged.

CONCLUSION

This study demonstrates that antisense ODNs to ferritin genes are about two-fold more cytotoxic than sense ODNs, and that antisense ODNs are specific inhibitors of ferritin gene expression at both the transcriptional and the translational levels. Further, the antisense ferritin ODNs promote programmed cell death with low ratios of Bcl-2 to Bax mRNA and protein expression providing evidence that antisense ferritin ODNs specifically inhibit MCF-7 breast carcinoma cell growth through increased apoptosis. Finally, since the IC50 concentrations of FerH-A1 and FerH-A2, and FerL-A1 and FerL-A2 are very similar for inhibition of DNA synthesis and gene expression in human breast carcinoma MCF-7 cells, it does not seem necessary for the antisense ODNs to overlap the starting codons of ferritin gene to maximize inhibition.

Synthesis and antiproliferative activity in vitro of new 3-substituted aminopyrazolo[3,4-b]pyridines

The synthesis of several new 3-substituted aminopyrazolo[3,4-b]pyridines is described. The obtained compounds were tested for their antiproliferative activity in vitro. Two of them: 3-chloroacetylaminopyrazolo[3,4-b]pyridine [II] and 3-(2-bromopropionyl-amino)pyrazolo[3.4-b]pyridine [III] revealed cytotoxic activity against the cells of 5 human tumor cell lines applied. Their ID50 values were in the range of the international activity criterion for synthetic agents (4 microg/ml). The structures of the products II-XVII were established on the basis of elemental analysis and spectral data (IR, 1H NMR and MS).

Total synthesis of spirotryprostatin B via asymmetric nitroolefination

[reaction: see text] A total synthesis of spirotryprostatin B was accomplished via asymmetric nitroolefination as a key step.

Total syntheses of conformationally constrained didemnin B analogues. replacements of N,O-dimethyltyrosine with L-1,2,3,4-tetrahydroisoquinoline and L-1,2,3,4-tetrahydro-7-methoxyisoquinoline

The design and synthesis of two conformationally constrained analogues of didemnin B are described. The [N,O-Me(2)Tyr(5)]residue of didemnin B was replaced with L-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) and L-1,2,3,4-tetrahydro-7-methoxyisoquinoline-3-carboxylic acid (MeO-Tic), which mimic the N,O-dimethylated tyrosine while constraining the conformation of the molecule. Preliminary results indicate that the conformation of the [N,O-Me(2)Tyr(5)]residue closely matches the conformation imposed by the Tic replacement.

Antileukemic activity of synthetic daunomycinone derivatives bearing modifications in the glycosidic moiety

The antileukemic activities of the daunomycinone glycosides synthesized in our laboratories (compounds 4 and 7, code names S12 and S13, respectively) were characterized in L1210 cells in vitro. S13 inhibits tumor cell proliferation and viability at day 4 (IC50: 150-200 nM) more effectively than S12 (IC50: 250-450 nM), suggesting that the 4'-trifluoracetamido substitution of the glycosidic moiety of these 3'-halo daunonycinone derivatives has greater antitumor potential than the 4'-azido substitution. Since S12 and S13 do not increase but rather decrease the mitotic index of L1210 cells at 24 hours, they are not antitubulin drugs but might arrest the early stages of cell cycle progression. Pretreatments for 1.5-3 hours with S12 and S13 are sufficient to partially inhibit the rates of DNA and RNA syntheses (IC50: 4-10 microM) determined over 30- to 60-minute periods of pulse-labeling in L 1210 cells in vitro, but these daunomycinone glycosides alter neither the cellular transport of purine and pyrimidine nucleosides nor the rate of protein synthesis. After 24 hours, the concentration-dependent induction of DNA cleavage by S13 reaches a plateau at 10 microM but the weaker S12 requires 48 hours to maximally stimulate DNA cleavage like S13. The mechanism by which S13 induces DNA fragmentation is inhibited by actinomycin D, cycloheximide, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, benzyloxycarbonyl-Ile-Glu-Thr-Asp-fluoromethyl ketone, N-tosyl-L-phenylalanine chloromethyl ketone and ZnSO4, suggesting that S13 triggers apoptosis by caspase and endonuclease activation. Since microM concentrations of S12 and S13 are cytostatic and cytotoxic, but do not sufficiently inhibit RNA and protein syntheses to block their own ability to sustain the active process of apoptosis and DNA fragmentation, such 3'-halo daunomycinone glycosides might be valuable to develop new means of polychemotherapy.

Structure-based design of a bispecific receptor mimic that inhibits T cell responses to a superantigen

Key surface proteins of pathogens and their toxins bind to the host cell receptors in a manner that is quite different from the way the natural ligands bind to the same receptors and direct normal cellular responses. Here we describe a novel strategy for "non-antibody-based" pathogen countermeasure by targeting the very same "alternative mode of host receptor binding" that the pathogen proteins exploit to cause infection and disease. We have chosen the Staphylococcus enterotoxin B (SEB) superantigen as a model pathogen protein to illustrate the principle and application of our strategy. SEB bypasses the normal route of antigen processing by binding as an intact protein to the complex formed by the MHC class II receptor on the antigen-presenting cell and the T cell receptor. This alternative mode of binding causes massive IL-2 release and T cell proliferation. A normally processed antigen requires all the domains of the receptor complex for its binding, whereas SEB requires only the alpha1 subunit (DRalpha) of the MHC class II receptor and the variable beta subunit (TCRVbeta) of the T cell receptor. This prompted us to design a bispecific chimera, DRalpha-linker-TCRVbeta, that acts as a receptor mimic and prevents the interaction of SEB with its host cell receptors. We have adopted (GSTAPPA)(2) as the linker sequence because it supports synergistic binding of DRalpha and TCRVbeta to SEB and thereby makes DRalpha-(GSTAPPA)(2)-TCRVbeta as effective an SEB binder as the native MHC class II-T cell receptor complex. Finally, we show that DRalpha-(GSTAPPA)(2)-TCRVbeta inhibits SEB-induced IL-2 release and T cell proliferation at nanomolar concentrations.

Interaction between heat shock proteins and antimicrobial peptides

Drosocin, pyrrhocoricin, and apidaecin, representing the short (18-20 amino acid residues) proline-rich antibacterial peptide family, originally isolated from insects, were shown to act on a target bacterial protein in a stereospecific manner. Native pyrrhocoricin and one of its analogues designed for this purpose protect mice from bacterial challenge and, therefore, may represent alternatives to existing antimicrobial drugs. Furthermore, this mode of action can be a basis for the design of a completely novel set of antibacterial compounds, peptidic or peptidomimetic, if the interacting bacterial biopolymers are known. Recently, apidaecin was shown to enter Escherichia coli and subsequently kill bacteria through sequential interactions with diverse target macromolecules. In this paper report, we used biotin- and fluorescein-labeled pyrrhocoricin, drosocin, and apidaecin analogues to identify biopolymers that bind to these peptides and are potentially involved in the above-mentioned multistep killing process. Through use of a biotin-labeled pyrrhocoricin analogue, we isolated two interacting proteins from E. coli. According to mass spectrometry, Western blot, and fluorescence polarization, the short, proline-rich peptides bound to DnaK, the 70-kDa bacterial heat shock protein, both in solution and on the solid-phase. GroEL, the 60-kDa chaperonin, also bound in solution. Control experiments with an unrelated labeled peptide showed that while binding to DnaK was specific for the antibacterial peptides, binding to GroEL was not specific for these insect sequences. The killing of bacteria and DnaK binding are related events, as an inactive pyrrhocoricin analogue made of all-D-amino acids failed to bind. The pharmaceutical potential of the insect antibacterial peptides is underscored by the fact that pyrrhocoricin did not bind to Hsp70, the human equivalent of DnaK. Competition assay with unlabeled pyrrhocoricin indicated differences in GroEL and DnaK binding and a probable two-site interaction with DnaK. In addition, all three antibacterial peptides strongly interacted with two bacterial lipopolysaccharide (LPS) preparations in solution, indicating that the initial step of the bacterial killing cascade proceeds through LPS-mediated cell entry.

Selective inhibition of human Molt-4 leukemia type II inosine 5'-monophosphate dehydrogenase by the 1,5-diazabicyclo[3.1.0]hexane-2,4-diones

Inosine 5'-monophosphate dehydrogenase (IMPDH) is the rate-limiting enzyme in de novo purine biosynthesis. IMPDH activity results from expression of two isoforms. Type I is constitutively expressed and predominates in normal resting cells, while Type II is selectively up-regulated in neoplastic and replicating cells. Inhibitors of IMPDH activity selectively targeting the Type II isoform have great potential as cancer chemotherapeutic agents. For this study, an expression system was developed which yields 35-50 mg of soluble, purified recombinant Type I and II protein from 1 L of bacteria. In addition, three 1,5-diazabicyclo[3.1.0]hexane-2,4-diones were synthesized and shown to act as specific inhibitors of human recombinant Type II IMPDH. The agents are competitive inhibitors with respect to the endogenous substrate IMP and K(i) values range from 5 to 44 microM but were inactive as inhibitors of the Type I isoform at concentrations ranging from 0.5 to 500 microM. IC(50) values for recombinant Type II inhibition were determined and compared to IC(50) values obtained from Molt-4 cell extracts of IMPDH. Cytotoxicity assays revealed that the compounds inhibited Molt-4 leukemia growth with ED(50) values of 3.2-7.6 microM. Computational docking studies predict that the compounds bind to IMPDH in the IMP-binding site, although interactions with residues differ from those previously determined to interact with bound IMP. While all residues predicted to interact directly with the bound compounds are conserved in the Type I and Type II isoforms, sequence divergence within a helix adjacent to the active site may contribute to the observed selectivity for the human Type II isoform. These compounds represent the first class of selective IMPDH Type II inhibitors which may serve as lead compounds for the development of isoform-selective cancer chemotherapy.

Induced G2/M arrest and apoptosis in human epidermoid carcinoma cell lines by semisynthetic drug Ukrain

Exposure of ME180 and A431 carcinoma cells to Ukrain (NSC-631570), a novel semisynthetic drug from Chelidonium majus L, results in cell growth inhibition which is concomitant with reversible G2/M cell cycle arrest and apoptosis at doses as low as 7 microM. In contrast, the same drug concentrations were not affective towards normal human keratinocytes. In order to investigate whether cell cycle control mechanisms are effected in response to Ukrain, we analyzed cell cycle distribution and levels of cyclins and cyclin-dependent kinases in drug treated carcinoma cells. We found alterations in levels of mitotic cyclins A and B1, and cyclin-dependent kinases CDK1 and CDK2, after treatment. We also observed an upregulation of CDK inhibitor p27 in both cancer cell lines which may lead to the G2/M cells accumulation.

Design, synthesis and antitumor cytotoxicity of novel bis-benzimidazoles

A series of novel bis-benzimidazoles, IIa-e, IIIa-e and IVa-g, was designed, synthesized and evaluated for anticancer properties. Certain additional analogs were also designed by introducing the p-quinone moiety, a characteristic feature found in mitomycin C, indolequinones and other examples of bioreductively activated alkylating agents. Structural changes of the bis-benzimidazole nucleus with various leaving groups were investigated for their effects on their pharmacological properties. These compounds were evaluated for their cytotoxicity against human cancer cell lines. The results of the studies indicate that the compounds IIa, IIc, IVa, IVc, IVd and IVg possess significant cytotoxic activities against 22 cell lines in seven cancer panels with GI50 values between <0.01 and 99.5 microM especially in the cases of renal cancer, CNS cancer, colon cancer, melanoma and breast cancer.

Synthesis and antimelanoma activity of analogues of N-acetyl-4-S-cysteaminylphenol

N-Acetyl-4-S-cysteaminylphenol (1) has been shown by Jimbow and co-workers to possess useful antimelanoma activity. It is an analogue of a biosynthetic intermediate in the pathway to melanin and probably acts as a prodrug, being oxidized to an o-quinone which reacts with essential enzymes containing sulphydryl groups resulting in interference with cell growth and proliferation. We have synthesized a range of analogues of 1 by varying the acyl portion of the amide with the intention of increasing the lipophilicity of the compounds. A modest increase in melanoma activity against six melanoma cell lines for these analogues could be correlated with increased lipophilicity. The most active of these compounds, N-[2-[(4-hydroxyphenyl)thiol]ethyl]cyclohexanecarboxamide (9), showed promising selectivity (lack of cytotoxicity) on the non-melanotic cell line SK-Mel-24 and on an ovarian cell line. A significant improvement in antimelanoma activity was observed with a new type of analogue containing three carbon atoms between the sulphur and nitrogen. The most active of these new analogues, N-[3-[(4-hydroxyphenyl)-thiolpropyl]-1-cyclohexanecarboxamide (15), had activity comparable to cisplatin against several cell lines and low cytotoxicity towards the non-melanotic cell line.