P388 Murine Leukemia Research Articles

Concise Synthesis and Biological Assessment of (+)‐Neopeltolide and a 16‐Member Stereoisomer Library of 8,9‐Dehydroneopeltolide: Identification of Pharmacophoric Elements

We describe herein a concise synthesis of (+)-neopeltolide, a marine macrolide natural product that elicits a highly potent antiproliferative activity against several human cancer cell lines. Our synthesis exploited the powerful bond-forming ability and high functional group compatibility of olefin metathesis and esterification reactions to minimize manipulations of oxygen functionalities and to maximize synthetic convergency. Our findings include a chemoselective olefin cross-metathesis reaction directed by H-bonding, and a ring-closing metathesis conducted under non-high dilution conditions. Moreover, we developed a 16-member stereoisomer library of 8,9-dehydroneopeltolide to systematically explore the stereostructure-activity relationships. Assessment of the antiproliferative activity of the stereoisomers against A549 human lung adenocarcinoma, MCF-7 human breast adenocarcinoma, HT-1080 human fibrosarcoma, and P388 murine leukemia cell lines has revealed marked differences in potency between the stereoisomers. This study provides comprehensive insights into the structure-activity relationship of this important antiproliferative agent, leading to the identification of the pharmacophoric structural elements and the development of truncated analogues with nanomolar potency.

Synthesis, Structure and Cytotoxic Activity of New Acetylenic Derivatives of Betulin

A new series of betulin derivatives containing one or two pharmacophores bearing an acetylenic and carbonyl function at the C-3 and/or C-28 positions has been synthesized and characterized by 1H- and 13C-NMR, IR, MS and elemental analyses. The crystal structure of 28-O-propynoylbetulin was determined by X-ray structural analysis. All new compounds, as well as betulin, were tested in vitro for their antiproliferative activity against human SW707 colorectal, CCRF/CEM leukemia, T47D breast cancer, and against murine P388 leukemia and Balb3T3 normal fibroblasts cell lines. Most of the compounds showed better cytotoxicity than betulin and cisplatin used as reference agent. 28-O-Propynoylbetulin was the most potent derivative, being over 500 times more potent than betulin and about 100 times more cytotoxic than cisplatin against the human leukemia (CCRF/CEM) cell line, with an ID50 value of 0.02 μg/mL.

Phytochemical of Indonesian Macaranga and their Cytotoxic Properties Against P388 Cells

Plants as a source of bioactive chemicals have been known since very long time, and thus it is a rational strategy to develop phytochemical studies on the Indonesian plants and tested the isolated chemicals on a various biological systems. Since 1999, the author, as a part the Group of Natural Products Chemistry, Institut Teknologi Bandung, has actively wotk on a number of Indonesian plant families, including Lauraceae, Moraceae, Dipterocarpaceae, Zingiberaceae, and Euphorbiaceae, aiming to find new biologically active chemicals from nature. In this presentation, studies on Macaranga species (Euphorbiaceae) will be presented, hightlighting the results from six species of the genus, namely M. gigantea, M. lowii, M. pruinosa, M. recurvata, M. rhizinoides, and M. trichocarpa. Samples of the plants to be extracted were the leaves, and extraction was done either with acetone or methanol. Fractionation was carried out by vacuum liquid chromatography eluted by a gradient solvent system of n-hexaneEtOAc. Purification of the metabolites was done mainly with radial chromatography eluted with various solvent systems. Twenty seven flavonoid and stibene derivatives were isolated and identified, seventeen of which were new compounds. These compounds are substituted with isoprenyl, geranyl, farnesyl, and an iregular sesquiterpenyl group with a cyclobutane skeleton. In the presentation, several selected NMR spectra of the compounds will be described. On biological evaluation against murine leukemia P-388 cells by MTT assay these compounds showed varying cytotoxicities, with the highest active compounds was an isoprenylated dihydroflavanone isolated from M. recurvata. In conclusion, Macaranga is a unique source of flavonoid and stilbene derivatives, some of them have potential for biological activities. Keeping that Indonesia is one of the center of Macaranga’s diversity, pytochemical and biological research on this plant should be continued.

Cytotoxic Activity of Secondary Metabolites from the Bark of Dipterocarpus Confertus Sloot

Four compounds, namely β-sitosterol (1), betulinic acid (2), cinnamic acid (3), and α-viniferin (4) have been successfully isolated from the bark methanol extract of Dipterocarpus confertus Sloot. The structures of the isolated compounds have been established on the basis spectroscopic data evidence, and comparison with the published data. In the cytotoxicity study, cinnamic acid (3) and betulinic acid (2) have been found to be very strong active against murine leukemia P388 and vero cells lines with the IC50 values of 2.25 and 5.10 µg/mL, respectively, while the other compounds were not active.

Pyrinodemins G–I, new bis-3-alkylpyridine alkaloids from a marine sponge Amphimedon sp.

Three new bis-3-alkylpyridine alkaloids, pyrinodemins G–I (1–3), were isolated from an Okinawan marine sponge Amphimedon sp. and the structures of 1–3 were elucidated on the basis of spectroscopic data. Pyrinodemins G–I (1–3) were novel bis-3-alkylpyridine alkaloids possessing an N-methoxy amide moiety, an α,β-unsaturated 3,5-disubstituted γ-lactone moiety, and a 2,3-di-substituted acrolein at a junction of two 3-alkylpyridines, respectively. Pyrinodemins G (1) and H (2) showed cytotoxicity against P388 murine leukemia cells.

Synthesis, antiproliferative and apoptotic activities of N-(6(4)-indazolyl)-benzenesulfonamide derivatives as potential anticancer agents

Recently, it has been reported that compounds bearing a sulfonamide moiety possess many types of biological activities, including anticancer activity. The present work reports the synthesis and antiproliferative evaluation of some N-(6(4)-indazolyl)benzenesulfonamides and 7-ethoxy-N-(6(4)-indazolyl)benzenesulfonamides.All compounds were evaluated for their in vitro antiproliferative activity against three tumor cell lines: A2780 (human ovarian carcinoma) A549 (human lung adenocarcinoma) and P388 (murine leukemia). The results indicated that sulfonamides 2c, 3c, 6d, 8, 13, 3b and 16 were endowed with a pharmacologically interesting antiproliferative activity with compounds 2c and 3c showing the lower IC50 (from 0.50 ± 0.09 to 1.83 ± 0.52 μM and from 0.58 ± 0.17 to 5.83 ± 1.83 μM, respectively). Moreover, these indazoles were able to trigger apoptosis through the upregulation of the typical apoptosis markers p53 and bax.As regard to the hypothetic targets of these compounds, a preliminary docking analysis showed that all compounds seemed to interact with β-tubulin, in particular compound 3b that showed the lower Ki. The cytofluorimetric analysis of the cell cycle phases indicates that all compounds, when administered at their IC75, caused a block in the G2/M phase of the cell cycle with the generation of subpopulations of cells with a number of chromosome >4n. When the IC50s were applied we observed a prevalent block in the G0/G1 phase except for compounds 16 and 8 where a partial G2/M block was present with a concomitant decrease of cells in the G0/G1 and S phases of the cell cycle. Altogether these results suggest a possible, but not exclusive, interaction with microtubules.

A mixture of amino acids and other small molecules present in the serum suppresses the growth of murine and human tumors in vivo

Previously we have hypothesized that the small molecules which are selectively accumulated in cancer cells might participate in a non-immunological antitumor surveillance mechanism. We demonstrated earlier that a mixture of experimentally selected substances (“active mixture”, AM: l-arginine, l-histidine, l-methionine, l-phenylalanine, l-tyrosine, l-tryptophan, l-ascorbate, d-biotin, pyridoxine, riboflavin, adenine, l(-)malate) possesses a selective toxic effect in vitro on a variety of tumor cell lines, and we have shown that the AM selectively induces apoptosis of cancer cells in vitro. To explore the in vivo significance of our earlier findings we examined the antitumor effect of AM in Colon 26 murine colorectal adenocarcinoma, B16 murine melanoma, MXT murine mammary carcinoma, S180 murine sarcoma, P388 murine lymphoid leukemia, HL-60 human promyeloid leukemia, PC-3 human prostate carcinoma, and HT-29 human colon carcinoma tumor models. Treatment of tumor bearing mice with AM inhibited the growth of the tumors investigated, with an inhibitory effect ranging from 40 to 69%. The AM had a comparable antitumor effect with 5-fluorouracil and cisplatin in the Colon-26 tumor model, and combined treatment with AM and 5-fluorouracil or cisplatin resulted in an enhanced tumor growth inhibitory effect. The AM induced apoptosis through the mitochondrial pathway and induced G1 arrest in PC-3 cells and increased the number of apoptotic cells in PC-3 xenografts. These findings suggest that the AM might offer an interesting perspective in the treatment of cancer and in combination with other treatments may offer hope for a more effective cancer therapy.

Synthesis and characterization of new trimetallic complexes with {Pt2Au(μ-S)2}n+ (n = 2, 3) cores containing C, N and N, N donor ligands

Reactions of the dinuclear platinum(II) sulfide complex [Pt2(μ-S)2(PPh3)4] with a range of gold(III) dichloride complexes [AuLCl2] containing C, N- or N, N-cycloaurated ligands L gives a new series of dicationic adducts [Pt2(μ-S)2(PPh3)4AuL]2+, isolated as their PF6− salts. The complexes investigated are [Au{C6–H4(CH2NMe2)-2}Cl2], [Au{C6H3(CH2NMe2)-2-(OMe)-5}Cl2], [Au{NC5H4(CH2C6H4)-2}Cl2], [Au{NC5H4(COC6H4)-2}Cl2] and [Au{NC5H4(CONH)-2}Cl2]. An X-ray structure determination on the picolinamide-derived complex [Pt2(μ-S)2(PPh3)4Au{NC5H4(CONH)-2}](PF6)2 was not of sufficiently high quality for detailed discussion, but confirmed the atom connectivity. Reactions of [Pt2(μ-S)2(PPh3)4] with [AuCl2(bipy)]PF6 (L=bipy=2,2’-bipyridine) and [AuCl2(phen)]Cl (L=phen=1,10-phenanthroline) gives the corresponding tricationic adducts [Pt2(μ-S)2(PPh3)4AuL]3+, also isolated as their PF6− salts. The complexes are characterised by NMR spectroscopy, electrospray mass spectrometry and microelemental analyses. Biological assay data of a selection of these new complexes towards the P388 murine leukemia cell line, as well as a range of antimicrobial tests, reveals overall low activity compared to other cycloaurated gold(III) complexes.

Cytotoxic triterpenoids from the bark of Aglaia smithii (Meliaceae)

Two new dammarane triterpenoids, aglinone (1) and aglinin E (20S,24S-epoxy-25-hydroxy-1-en-dammarene) (2) along with three known compounds, 3-epiocotillol (3), aglinin A (4), and eichlerianic acid (5), were isolated from the bark of Aglaia smithii. The chemical structures of the new compound were elucidated on the basis of spectroscopic data interpretation. All the compounds isolated were evaluated for their cytotoxic effects against P-388 murine leukemia cells. Compounds 1, 2, 4 and 5 showed cytotoxicity against P-388 murine leukemia cells with IC50 values of 21, 42, 34, and 11μg/mL, respectively.

TERPENOIDS FROM THE STEM BARK OF JATROPHA PLANTS AND THEIR BIOLOGICAL ACTIVITIES

Three terpenoids, including two diterpenes (curcusone B and jatrophone) and a triterpene (stigmasterol) have been isolated from the stem bark of Jatropha plants. Curcusone B and stigmasterol were isolated from J. curcas, meanwhile jatrophone and stigmasterol were from J. gossypifolia. The biological activities of these compounds have been evaluated toward bacteria, fungi and tumour cells. Isolation was carried out in vacuum liqiud cromatography (VLC) technique with silica gel as an adsorben and some solvents as eluents. The compound structures were determined by spectroscopic methodes i.e. UV-vis, FTIR, NMR (1-D, 2-D) and were then compared based on their spectroscopic data with similiar data from literatures. The biological properties of these compounds were evaluated against four strains of bacteria (Acetobacter sp., Eschericia coli, Staphylococcus aureus, and Streptococcus sp.), 4 strains of fungi (Aspergilus niger, Penicillium sp. (grey), Penicillium sp. (white) and Rhizopus sp.) and murine leukemia P-388 cells. The results showed that cytotoxic property of curcusone B towards murine leukemia P-388 cells is better than jatrophone and stigmasterol which are IC50 = 0.57 μg/mL (1.93 μM) for curcusone B and IC50 > 100 μg/mL for jatrophone and stigmasterol. Meanwhile, activities against bacteria, jatrophone is better than curcusone B and stigmasterol. Jatrophone is the most active against S. aureus (bacteria) with growth inhibition zone 36 mm and A.niger (fungi) is 44 mm. Further study indicated that jatrophone was bacteriostatic against S. aureus.

Isolation and Characterization of a Murine P388 Leukemia Line Resistant to Thiarabine

A murine P388 leukemia line fully resistant to thiarabine was obtained after five courses of intraperitoneal treatment (daily for nine consecutive days). The subline was sensitive as was the parental P388/0 line to 5-fluorouracil, gemcitabine, cyclophosphamide, cisplatin, melphalan, BCNU, mitomycin C, doxorubicin, mitoxantrone, etoposide, irinotecan, vincristine, and paclitaxel, but was cross resistant (at least marginally) to three antimetabolites: palmO-ara-C, fludarabine phosphate, and methotrexate. The deoxycytidine kinase activity in the subline was comparable to that for P388/0, whereas the dCMP deaminase activity was 43% of that for P388/0. No deoxycytidine deaminase activity was detected in either of the leukemias. There appeared to be little, if any, difference in the metabolism of deoxycytidine, cytidine, or thiarabine in the two leukemias.

Isolation and Characterization of a Murine P388 Leukemia Line Resistant to Clofarabine

A murine P388 leukemia line fully resistant to clofarabine was obtained after only two courses of intraperitoneal treatment (three times a day for nine consecutive days). The resistance was stable for at least 13 weeks without treatment. The subline was as sensitive to 5-fluorouracil, methotrexate, cyclophosphamide, cisplatin, melphalan, BCNU, doxorubicin, etoposide, irinotecan, vincristine, and docetaxel as was the parental P388/0 line but was cross-resistant to five antimetabolites [palmO-ara-C, 4′-thio-ara-C, fludarabine phosphate, cladribine, and gemcitabine—all of which require deoxycytidine kinase for activation] and paclitaxel. The subline had less than 1% of the deoxycytidine kinase activity in comparison to P388/0.

Anti-tumor activity of immunomodulatory peptide alloferon-1 in mouse tumor transplantation model

Alloferons are a group of antiviral and anti-tumor peptides primarily isolated from insects and stimulating cytotoxic activity of natural killer cells in mammals including mice and humans. Alloferon-1 is currently used in the treatment of persistent viral infections; however its anti-tumor potential needs further preclinical assessment. Here we evaluate alloferon-1 anti-tumor activity in DBA/2 mice grafted with syngenic P388 murine leukemia cells. Alloferon-1 was applied alone or in combination with conventional cytotoxic chemotherapy (a mixture of cyclophosphamide, doxorubicin and vincristine). Alloferon-1 monotherapy demonstrated moderate tumoristatic and tumoricidal activities comparable with low dose chemotherapy. When alloferon-1 and the cytotoxic drugs were combined in a regime of pulse immunochemotherapy the combination anti-tumor activity evidently exceeded that of the treatments applied individually.

Antioxidant, antibacterial and cytotoxic activities of essential oils and ethanol extracts of selected South East Asian herbs

Antioxidant, antibacterial and cytotoxic activities of essential oils and ethanol extracts of four South East Asian traditional herbs were investigated. Their essential oils were analyzed byGas chromatography mass spectrometry (GC-MS) and a total of 57 types of volatile organics were identified. Artemisia argyi, Centella asiatica, Cosmos caudatus, and Polygonum hydropiper contained 30, 20, 19 and 21 types of volatiles, respectively. The major volatile hydrocarbon for A. argyi, C. asiatica and C. caudatus was a-cadinene while dodecanal was the major component for P. hydropiper. Total phenolic content of ethanol extracts analyzed by Folin-Ciocalteu method were in the range of 31.58±3.08 to 84.03±8.15 mg GAE/100 g. Free radical-scavenging activity of the four ethanol extracts were in the range of 654.43±17.22 to 5857.54±164.13 mg AA/100 g; while ferric-reducing antioxidant power were in the range of 26.58±1.10 to 50.08±0.71 mg AAE/g. Essential oils of all four species were inactive for both these assays. Ethanol extracts of these herbs were active against 60 to 80% of ten strains of human pathogenic bacteria tested, compared to 20 to 50% inhibition for essential oils. Only ethanol extracts of A. argyi and C. caudatus showed activity against P388 murine leukemia cell line, while all the essential oils were inactive. Key words: Antimicrobial, antioxidant, cytotoxicity, ethanol extracts, essential oils, total phenolic content.

Synthesis and biological evaluation of novel pyrazole derivatives with anticancer activity

We synthesized thirty-six novel pyrazole derivatives and studied their antiproliferative activity in human ovarian adenocarcinoma A2780 cells, human lung carcinoma A549 cells, and murine P388 leukemia cells.Four of these substances were selected because of their higher antiproliferative activity and further analyses showed that they were all able to induce apoptosis, although to a different extent. The expression of p53 and p21waf1, which induce apoptosis and cell cycle arrest, was evaluated by western blot analysis in cells treated with compound 12d.The analysis of the cell cycle showed that all the selected compounds cause a partial G2/M block and the formation of polyploid cells. Furthermore, the four selected compounds were tested for their interaction with the microtubular cytoskeletal system by docking analysis, tubulin polymerization assay and immunofluorescence staining, demonstrating that the compound 12d, unlike the other active derivatives, was able to significantly bind dimers of α- and β-tubulin, probably causing a molecular distortion resulting in the disassembly of microtubules.

Induction of apoptosis in murine leukemia by diarylheptanoids from Curcuma comosa Roxb.

Diarylheptanoids, isolated from the rhizome of Curcuma comosa Roxb., have several biological activities including anti-oxidant and anti-inflammation. The present study investigated the effect of five diarylheptanoids isolated from C. comosa rhizome on the proliferation of murine P388 leukemic cells. Compound-092, (3S)-1-(3,4-dihydroxyphenyl)-7-phenyl-(6E)-6-hepten-3-ol, bearing a catechol moiety, was the most potent diarylheptanoid (IC(50) of 4μM) in inhibiting P388 leukemic cell viability by causing DNA breakage and inducing apoptosis. Apoptotic cell death was characterized by the presence of chromatin condensation, formation of apoptotic bodies, DNA fragmentation, and externalization of plasma membrane phosphatidylserine. This compound increased caspase-3 activity about fivefold above the untreated control, decreased the intracellular reduced glutathione level, and impaired mitochondrial transmembrane potential. In the presence of Cu(II) ion, the compound exhibited a pro-oxidant activity causing DNA strand breakage and enhancing the anti-proliferative activity. The results provide evidence for the pro-oxidant activity of the diarylheptanoid bearing a catechol moiety in the induction of apoptosis in murine P388 leukemia.

Novel Acrylonitrile Derivatives, YHO-13177 and YHO-13351, Reverse BCRP/ABCG2-Mediated Drug ResistanceIn VitroandIn Vivo

Breast cancer resistance protein (BCRP/ABCG2) confers resistance to anticancer drugs such as 7-ethyl-10-hydroxycamptothecin (SN-38, an active metabolite of irinotecan), mitoxantrone, and topotecan. In this study, we examined the reversing effects of YHO-13177, a novel acrylonitrile derivative, and its water-soluble diethylaminoacetate prodrug YHO-13351 on the BCRP-mediated drug resistance. YHO-13177 potentiated the cytotoxicity of SN-38, mitoxantrone, and topotecan in both BCRP-transduced human colon cancer HCT116 (HCT116/BCRP) cells and SN-38-resistant human lung cancer A549 (A549/SN4) cells that express BCRP, but had little effect in the parental cells. In addition, YHO-13177 potentiated the cytotoxicity of SN-38 in human lung cancer NCI-H460 and NCI-H23, myeloma RPMI-8226, and pancreatic cancer AsPC-1 cells that intrinsically expressed BCRP. In contrast, it had no effect on P-glycoprotein-mediated paclitaxel resistance in MDR1-transduced human leukemia K562 cells and multidrug resistance-related protein 1-mediated doxorubicin resistance in MRP1-transfected human epidermoid cancer KB-3-1 cells. YHO-13177 increased the intracellular accumulation of Hoechst 33342, a substrate of BCRP, at 30 minutes and partially suppressed the expression of BCRP protein at more than 24 hours after its treatment in both HCT116/BCRP and A549/SN4 cells. In mice, YHO-13351 was rapidly converted into YHO-13177 after its oral or intravenous administration. Coadministration of irinotecan with YHO-13351 significantly increased the survival time of mice inoculated with BCRP-transduced murine leukemia P388 cells and suppressed the tumor growth in an HCT116/BCRP xenograft model, whereas irinotecan alone had little effect in these tumor models. These findings suggest that YHO-13351, a prodrug of YHO-13177, could be clinically useful for reversing BCRP-mediated drug resistance in cancer chemotherapy.

Systematic coordination chemistry and cytotoxicity of copper(II) complexes with methyl substituted 4-nitropyridine N-oxides

Three new nitrato copper(II) complexes of dimethyl substituted 4-nitropyridine N-oxide were synthesized and characterized by elemental analysis, magnetic, spectroscopic, thermal and X-ray methods, respectively. They were isolated as trans isomers, mononuclear (μ = 1.70–1.88 BM), five ( 1– 2) and four (3) coordinate species of general formula [Cu(NO 3) 2(H 2O)L 2] where L = 2,3-dimethyl-, 2,5-dimethyl-4-nitropyridine N-oxide and [Cu (NO 3) 2L 2], L = 3,5-dimethyl-4-nitropyridine N-oxide, respectively. The X-ray crystal structure of ( 1) (L = 2,3-dimethyl-4-nitropyridine N-oxide) was determined. The organic ligands, the complexes and copper hexaqua ion as a reference were tested in vitro on the cytotoxic activity against human cancer cell lines: MCF-7 (breast), SW-707 (colon) and P-388 (murine leukemia). The complexes are relatively strong cytotoxic agents towards P-388 cell line. Comparative analysis was performed for all known copper(II) complexes containing methyl derivatives of the 4-nitropyridine N-oxide on the basis of their composition, structure and cytotoxic activities. To obtain the typical structure for these species (i.e., 4-coordinate mononuclear of the type trans-[Cu(inorganic anion) 2L 2]), two methyl groups must be situated on both sides of nitrogen atom(s) (i.e., NO and NO 2) in the ligand. The biological activity was found to be strongly dependent upon the number of the methyl groups and the type of cell line. The best cytotoxic results were found for the complexes without substituents or with one methyl group. Generally, for all cell lines, the complexation increased cytotoxicity when compared with the free ligands.

Abstract 3518: In vitro and in vivo synergistic effects of F14512, a novel targeted cytotoxic agent in phase I clinical study, in combination with other anticancer drugs

Abstract Targeted anticancer therapies represent an increasing subject of interest in order to improve tumor cell selectivity. Extensive study suggests that the Polyamine Transport System (PTS) is an energy-dependent machinery generally hyper-activated in cancer cells with a high demand for polyamines. This system can be viewed as a suitable molecular target to deliver selectively polyamine-based molecules into cancer cells. We exploited this strategy to target a potent cytotoxic agent to PTS-positive tumor cells with F14512, a novel polyamine-epipodophyllotoxin conjugate that exhibits a high in vivo anti-tumor activity in a series of experimental murine and human tumors. F14512 has recently entered into clinical development. This preclinical study was undertaken to investigate its potential in combination chemotherapy therapies. The in vitro cytotoxicity of F14512 against the A549 human non-small cell lung cancer cell line was investigated following simultaneous incubation with a variety of cytotoxic/cytostatic drugs. When using median effect analysis, F14512 in combination with 5-fluorouracil, camptothecin, gemcitabine or mitoxantrone showed synergistic cytotoxicity. Additive effects were demonstrated when F14512 was combined with bortezomib, doxorubicin or SAHA while antagonistic anti-proliferative effects were observed only with co-incubation of F14512 and etoposide, vinorelbine or paclitaxel. Combinations inducing synergistic anti-proliferative activities were also investigated against the HL-60 human acute myeloid leukemia cell line, confirming the synergy with gemcitabine. Cellular effects of F14512 are characterized by a DNA damage induction, a cell cycle blockage in G2 phase and a cell death induction. Such characteristics were investigated in A549 cells treated with this combination in order to propose mechanistic explanation of this synergy. In vivo, F14512 combined with irinotecan, gemcitabine, mitoxantrone or doxorubicin showed a gain of anti-tumor activity against P388 murine leukemia grafted intravenously. As an example, the administration of sub-optimal doses of F14512 (0.63 mg/kg, q1d4 schedule) and mitoxantrone (1.25 mg/kg, single dose) alone resulted in an increased life span of only 29% compared to untreated mice, while combined treatments improved survival of tumor bearing mice with an increase life span of 57%. Moreover, F14512 combined with doxorubicin displayed an increased antitumor activity against MX-1 human breast cancer in nude mice.F14512 appears to be a promising candidate for combination chemotherapy, especially with DNA-damaging agents and antimetabolites. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3518. doi:10.1158/1538-7445.AM2011-3518

Cytotoxic Tetramic Acid Derivative Produced by a Plant Type-III Polyketide Synthase

The tetramic acid (2,4-pyrrolidinedione) scaffold has been recognized as an important structural feature because of its mycotoxic, antibacterial, antiviral, and antioxidant activities. This important class of natural products is reportedly produced by the type-I polyketide synthase/nonribosomal peptide synthetase (PKS/NRPS) hybrid megaenzyme systems. In contrast, the benzalacetone synthase (BAS) from Rheum palmatum is a structurally simple, plant-specific type-III PKS that catalyzes the one-step decarboxylative condensation of malonyl-CoA with 4-coumaroyl-CoA. The type-III PKS exhibits unusually broad substrate specificity and notable catalytic versatility. Here we report that R. palmatum BAS efficiently produces a series of unnatural, novel tetramic acid derivatives by the condensation of malonyl-CoA with aminoacyl-CoA thioesters chemically synthesized from L- and D-amino acids. Remarkably, the novel tetramic acid dimer D-5 formed from D-phenylalanoyl-CoA showed moderate antiproliferative activity against murine leukemia P388 cells.