Pachydictyols B and C: new diterpenes from Dictyota dichotoma Hudson.

Two new diterpenoids, pachydictyol B (1a/1b) and C (2), were isolated from the dichloromethane extract of the marine brown alga, Dictyota dichotoma, collected from the Red Sea coast of Egypt, along with the known metabolites, pachydictyol A (3a), dictyol E (4), cis-africanan-1α-ol (5a), fucosterol (6), tetrahydrothiophen-1,1-dioxide and poly-ß-hydroxybutyric acid. GC-MS analysis of the nonpolar fractions also indicated the presence of ß-bourbonene and nonanal, along with three hydrocarbons and five fatty acids or their simple derivatives, respectively. GC-MS analysis of the unsaponifiable algal petroleum ether extract revealed the presence of a further eight compounds, among them 2,2,6,7-tetramethyl-10-oxatricyclo[4.3.0.1(1,7)]decan-5-one (7), N-(4-bromo-n-butyl)-pipe ridin-2-one (8) and tert-hexadecanethiol. Structures 1-6 were assigned by 1D and 2D NMR, mass spectra (EI, CI, HREI and HRESI) and by comparison with data from related structures. The crude algal extract was potently active against the breast carcinoma tumor cell line, MCF7 (IC50 = 0.6 µg mL⁻¹); pachydictyol B (1a) and dictyol E (4) showed weak antimicrobial properties, and the other compounds were inactive. Pachydictyols B (1a) and C (2) demonstrated a weak and unselective cytotoxicity against twelve human tumor cell lines with a mean IC50 of >30.0 µM.

Mansouramycins A-D, cytotoxic isoquinolinequinones from a marine streptomycete.

Chemical screening of the ethyl acetate extract from the marine-derived Streptomyces sp. isolate Mei37 resulted in five isoquinolinequinones, four new derivatives, mansouramycin A-D (1, 3-5), and the known 3-methyl-7-(methylamino)-5,8-isoquinolinedione (2). Their structures were elucidated by NMR and MS techniques and by comparison with related compounds. Cytotoxicity profiling of the mansouramycins in a panel of up to 36 tumor cell lines indicated significant cytotoxicity of several derivatives, with pronounced selectivity for non-small cell lung cancer, breast cancer, melanoma, and prostate cancer cells.

Electrospray ionization mass spectra of piperazimycins A and B and gamma-butyrolactones from a marine-derived Streptomyces sp.

Chemical investigation of the marine-derived Streptomyces sp. Act8015 led to the isolation of two cyclic peptide antibiotics, piperazimycins A and B (1a, 1b). Their structures were confirmed on the basis of a detailed HRESI-MS/MS analysis. Additionally, a new butanolide, 4,10-dihydroxy-10-methyl-dodecan-4-olide (2), and the respective acid, 4,10-dihydroxy-10-methyl-dodecanoic acid (3a) were identified. Further isolated compounds were staurosporin, adenine, indole-3-carboxylic acid, ferulic acid, tryptophol, and three gamma-butyrolactones: virginiae butanolide E (4e) and Graefe's Factors I (4f) and III (4g). The structures of 2 and 3a were confirmed by detailed 1D and 2D NMR studies and MS spectra and by comparison with related structures. A full signal assignment of virginiae butanolide E (4e) is reported here for the first time.

N-carboxamido-staurosporine and selina-4(14),7(11)-diene-8,9-diol, new metabolites from a marine Streptomyces sp.

In our screening of micro-organisms for novel bioactive natural products, a new staurosporinone, N-carboxamido-staurosporine (1c), and a new sesquiterpene, (5S,8S,9R, 10S)-selina-4(14),7(11)-diene-8,9-diol (2a), were isolated from the culture broth of the marine-derived Streptomyces sp. QD518. Their structures were determined by spectroscopic methods and by comparison of the NMR data with those of structurally related known natural products, which were isolated from the same strain.

2-aroylindoles, a novel class of potent, orally active small molecule tubulin inhibitors.

2-Aroylindoles with 5-methoxy-1H-2-indolyl-phenylmethanone (D-64131) as the lead structure were discovered as a new class of synthetic, small molecule tubulin inhibitors. By competitively binding with [(3)H]colchicine to alphabeta-tubulin and inhibiting microtubule formation, cycling cells were arrested in the G(2)-M phase of the cell division cycle. The proliferation of tumor cells from 12 of 14 different organs and tissues was inhibited with mean IC(50)s of 62 nM and 24 nM by D-64131 and D-68144, respectively, comparable with the potency of paclitaxel with mean IC(50) of 10 nM. By measuring the cytotoxicity in a human colon carcinoma cell model with ectopic ecdysone-inducible expression of the cyclin-dependent kinase inhibitor p21(WAF1), specificity toward cycling cells was demonstrated. In contrast to microtubule inhibitors from natural sources, 2-aroylindoles did not alter the polymerization-dependent GTPase activity of beta-tubulin and are not substrates of the multidrug resistance/multidrug resistance protein efflux pump. No cross-resistance toward cell lines with multidrug resistance/multidrug resistance protein independent resistance phenotypes became evident. In animal studies, no signs of systemic toxicity were observed after p.o. dosages of up to 400 mg/kg of D-64131. In xenograft experiments with the human amelanoic melanoma MEXF 989, D-64131 was highly active with treatment resulting in a growth delay of 23.4 days at 400 mg/kg. Therefore, D-64131 and analogues have the potential to be developed for cancer therapy, replacing or supplementing standard therapy regimens with tubulin-targeting drugs from natural sources.

Intrinsic Resistance to Cixutumumab Is Conferred by Distinct Isoforms of the Insulin Receptor.

UNLABELLED: Despite a recent shift away from anti-insulin-like growth factor I receptor (IGF-IR) therapy, this target has been identified as a key player in the resistance mechanisms to various conventional and targeted agents, emphasizing its value as a therapy, provided that it is used in the right patient population. Molecular markers predictive of antitumor activity of IGF-IR inhibitors remain largely unidentified. The aim of this study is to evaluate the impact of insulin receptor (IR) isoforms on the antitumor efficacy of cixutumumab, a humanized mAb against IGF-IR, and to correlate their expression with therapeutic outcome. The data demonstrate that expression of total IR rather than individual IR isoforms inversely correlates with single-agent cixutumumab efficacy in pediatric solid tumor models in vivo. Total IR, IR-A, and IR-B expression adversely affects the outcome of cixutumumab in combination with chemotherapy in patient-derived xenograft models of lung adenocarcinoma. IR-A overexpression in tumor cells confers complete resistance to cixutumumab in vitro and in vivo, whereas IR-B results in a partial resistance. Resistance in IR-B-overexpressing cells is fully reversed by anti-IGF-II antibodies, suggesting that IGF-II is a driver of cixutumumab resistance in this setting. The present study links IR isoforms, IGF-II, and cixutumumab efficacy mechanistically and identifies total IR as a biomarker predictive of intrinsic resistance to anti-IGF-IR antibody. IMPLICATIONS: This study identifies total IR as a biomarker predictive of primary resistance to IGF-IR antibodies and provides a rationale for new clinical trials enriched for patients whose tumors display low IR expression.

Anti-cancer and antibacterial trioxacarcins with high anti-malaria activity from a marine Streptomycete and their absolute stereochemistry.

The ethyl acetate extract from the Streptomyces sp. isolate B8652 delivered the trioxacarcins A to approximately C (2a to approximately 2c) and additionally three new derivatives designated as trioxacarcins D to approximately F (2d to approximately 2f). All trioxacarcins showed high anti-bacterial and some of them high anti-tumor and anti-malaria activity. The structures of the new antibiotics were derived from mass, 1D and 2D NMR spectra and confirmed by comparison of the NMR data with those of known derivatives. The absolute configuration of the trioxacarcins is deduced from the X-ray analysis of gutingimycin (2g) and from the known stereochemistry of the L-trioxacarcinoses A and B.

Chandrananimycins A approximately C: production of novel anticancer antibiotics from a marine Actinomadura sp. isolate M048 by variation of medium composition and growth conditions.

In our screening of marine actinomycetes for bioactive principles, three novel antibiotics designated as chandrananimycin A (3c), B (3d) and C (4) were isolated from the culture broth of a marine Actinomadura sp. isolate M045. The structures of the new antibiotics were determined by detailed interpretation of mass, 1D and 2D NMR spectra.

Validation of tumour models for use in anticancer nanomedicine evaluation: the EPR effect and cathepsin B-mediated drug release rate.

PURPOSE: Intravenously (i.v.) administered nanomedicines have the potential for tumour targeting due to the enhanced permeability and retention (EPR) effect, but in vivo tumour models are rarely calibrated with respect to functional vascular permeability and/or mechanisms controlling intratumoural drug release. Here the effect of tumour type and tumour size on EPR-mediated tumour localisation and cathepsin B-mediated drug release was studied. METHODS: Evans Blue (10 mg/kg) and an N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer­doxorubicin (Dox) conjugate (FCE28068) (5 mg/kg Dox-equiv) were used as probes and tumour levels (and Dox release) measured at 1 h after i.v. administration in a panel of murine and human xenograft tumours. RESULTS: Evans Blue and FCE28068 displayed similar tumour levels in the range of 2­18 % dose/g at 1 h for B16F10 and L1210. Approximately half of the tumour models evaluated exhibited tumour size-dependent accumulation of FCE28068; smaller tumours had the highest accumulation. Administration of free Dox (5 mg/kg) produced tumour levels of \2.5 % dose/g independent of tumour size. Whereas the degree of EPR-mediated targeting showed *12-fold difference across the tumour models evaluated, Dox release from FCE28068 at 1 h displayed *200-fold variation. CONCLUSIONS: Marked heterogeneity was seen in terms of EPR effect and Dox release rate, underlining the need to carefully calibrate tumour models used to benchmark nanomedicines against known relevant standard agents and for optimal development of strategies for late pre-clinical and clinical development.

Characterization of the anticancer properties of monoglycosidic cardenolides isolated from Nerium oleander and Streptocaulon tomentosum.

AIM OF THE STUDY: For identification of the active constituents we investigated the anticancer activity of cardenolides from Streptocaulon tomentosum Wight & Arn. (Asclepiadaceae) and from Nerium oleander L. (Apocynaceae) which are both used against cancer in the traditional medicine in their region of origin. MATERIAL, METHODS AND RESULTS: The antiproliferative activity of cardenolides isolated from roots of Streptocaulon tomentosum (IC(50)<1-15.3 µM after 2 days in MCF7) and of cardenolide containing fractions from the cold aqueous extract of Nerium oleander leaves ("Breastin", mean IC(50) 0.85 µg/ml in a panel of 36 human tumor cell lines), their influence on the cellular viability and on the cell cycle (block at the G2/M-phase or at the S-phase in tumor cells, respectively) were determined using different cell lines. The murine cell line L929 and normal non-tumor cells were not affected. Bioactivity guided fractionation of Breastin resulted in the isolation of the monoglycosidic cardenolides oleandrine, oleandrigeninsarmentoside, neritaloside, odoroside H, and odoroside A (IC(50)-values between 0.010 and 0.071 µg/ml). CONCLUSIONS: The observed anticancer activities of extracts and isolated cardenolides are in agreement with the ethnomedicinal use of Streptocaulon tomentosum and Nerium oleander. The most active anticancer compounds from both species are monoglycosidic cardenolides possessing the 3ß,14ß-dihydroxy-5ß-card-20(22)-enolide structure with or without an acetoxy group at C-16. The results indicate that the cytotoxic effects are induced by the inhibition of the plasma membrane bound Na(+)/K(+)-ATPase.

Julichrome Q6 glucuronide, a monomeric subunit of the julimycin B-I complex from a terrestrial Streptomyces sp.

The terrestrial Streptomyces sp. isolate GW6225 afforded julichrome Q 6 glucuronide ( 9), the first monomeric member of the julimycin-B complex, and additionally the julichromes Q 1.2 ( 7a), Q 1.5 ( 7b), and Q 3.5 ( 8), which were fully characterized by 2D NMR spectra. Additional new microbial compounds were 4-acetylchrysophanol ( 6a) and N-phenyl-beta-naphthylamine ( 10). The isomeric N-phenyl-alpha-naphthylamine ( 11) was found in the marine Streptomyces sp. B8335 and was also characterized. The high antibiotic activity of Streptomyces sp. GW6225 extracts was probably due to the thiazolyl cyclopeptide nosiheptide.

Correlation of ErbB2 gene status, mRNA and protein expression in a panel of >100 human tumor xenografts of different origin.

INTRODUCTION: The receptor tyrosine kinase ErbB2 is an important prognostic marker and therapeutic target in breast cancer. The aim of this study was to investigate the correlation between ErbB2 gene amplification, mRNA and protein expression in a panel of >100 patient-derived nude mouse tumor xenografts of different histological origin. MATERIALS AND METHODS: Data were obtained using fluorescence in situ hybridization, GenChip expression analysis, immunohistochemistry and enzyme-linked immunosorbent assay (ELISA). Tumors included the following types: urinary bladder, breast, colon, stomach, kidney, liver, lung, melanoma, ovary, pancreas, prostate, uterus/cervix uteri and others. RESULTS: All tumors with high-level ErbB2 gene amplification expressed ErbB2 mRNA at a level >10-fold above average and protein at a level >20-fold above average (ELISA). Correlation was found between ErbB2 mRNA and protein expression. CONCLUSION: Based on expression data, cervical, gastric and adenocarcinomas of the lung emerged as new potential indications for ErbB2-directed cancer therapies.

Correlation of the acid-sensitivity of polyethylene glycol daunorubicin conjugates with their in vitro antiproliferative activity.

Polyethylene glycol conjugates with linkers of varying acid-sensitivity were prepared by reacting five maleimide derivatives of daunorubicin containing an amide bond (1) or acid-sensitive carboxylic hydrazone bonds (2-5) with alpha-methoxy-poly(ethylene glycol)-thiopropionic acid amide (MW 20000) or alpha,omega-bis-thiopropionic acid amide poly(ethylene glycol) (MW 20000). The polymer drug derivatives were designed to release daunorubicin inside the tumor cell by acid-cleavage of the hydrazone bond after uptake of the conjugate by endocytosis. In subsequent cell culture experiments, the order of antitumor activity of the PEG daunorubicin conjugates correlated with their acid-sensitivity as determined by HPLC (cell lines: BXF T24 bladder carcinoma and LXFL 529L lung cancer cell line; assay: propidium iodide fluorescence assay). The acid-sensitivity of the link between PEG and daunorubicin is therefore an important parameter for in vitro efficacy.

Chinikomycins A and B: isolation, structure elucidation, and biological activity of novel antibiotics from a marine Streptomyces sp. isolate M045.

In our screening of marine Streptomycetes for bioactive principles, two novel antitumor antibiotics designated as chinikomycins A (2a) and B (2b) were isolated together with manumycin A (1), and their structures were elucidated by a detailed interpretation of their spectra. Chinikomycins A (2a) and B (2b) are chlorine-containing aromatized manumycin derivatives of the type 64-pABA-2 with an unusual para orientation of the side chains. They exhibited antitumor activity against different human cancer cell lines, but were inactive in antiviral, antimicrobial, and phytotoxicity tests.