Altersolanol A: a selective cytotoxic anthraquinone from a Phomopsis sp.

UNLABELLED: The cytotoxic compound Altersolanol A, an anthraquinone derivative was isolated from PM0409092 a fungus of Nyctanthes arbor-tristis (family Oleaceae). It was identified as a Phomopsis sp. by DNA amplification and sequencing of the ITS region. The chemical structure of Altersolanol A was elucidated from its physicochemical properties, 2D NMR spectroscopy and other spectroscopic data. The compound has in vitro cytotoxic activity against 34 human cancer cell lines with mean IC50 (IC70) values of 0.005 µg ml(-1) (0.024 µg ml(-1)) respectively. Altersolanol A, a kinase inhibitor, induces cell death by apoptosis through the cleavage by Caspase-3 and -9 and by decreased anti-apoptotic protein expression. There are several previous reports of the anticancer activity of Altersolanol A, but we report here an extensive study using 36 cell lines which gives wider spectrum of results. SIGNIFICANCE AND IMPACT OF THE STUDY: This study confirms the cytotoxic potential of Altersolanol A isolated from the endophyte Phomopsis sp. (PM0409092) of the plant Nyctanthes arbor-tristis. The compound exhibits in vitro cytotoxicity against 34 human cancer cell lines with mean IC50 (IC70) value of 0.005 µg ml(-1) (0.024 µg ml(-1)). This is an in-depth report of Altersolanol A against a panel of 34 human cancer cell lines and extends observations from previous studies indicating that Altersolanol A can be used for the development of chemotherapeutics. Altersolanol A, a kinase inhibitor, induces cell death by apoptosis through the cleavage of Caspase-3 and -9 and by decreased anti-apoptotic protein expression.

Telomerase activity and telomere length in human tumor cells with acquired resistance to anticancer agents.

Telomeres and telomerase are targets for anticancer drug development and specific inhibitors are currently under clinical investigation. However, it has been reported that standard cytotoxic agents can affect telomere length and telomerase activity suggesting that they also have of a role in drug resistance. in this study, telomere lengths and telomerase activity as well as drug efflux pump expression, glutathione (GSH) levels and polyadenosine-ribose polymerase (PARP) cleavage were assessed in a panel of human tumor cell lines made resistant to vindesine, gemcitabine and cisplatin. these included two lung cancer cell lines resistant to vindesine (LXFL 529L/Vind, LXFA 526L/Vind), a renal cancer cell line (RXF944L/Gem) and an ovarian cancer cell line (AG6000) resistant to gemcitabine, and one resistant to cisplatin (ADDP). The resistant clones were compared to their parental lines and evaluated for cross resistance to other cytotoxic agents. Several drug specific resistance patterns were found, and various complex patterns of cross resistance emerged from some cell lines, but these mechanisms of resistance could not be related to drug efflux pump expression, GSH levels or pARp cleavage. However, all displayed changes in telomerase activity and/or telomere length. Our studies present evidence that telomere maintenance should be taken into consideration in efforts not only to overcome drug resistance, but also to optimize the use of telomere-based therapeutics.

Preclinical pharmacology of the pyrrolobenzodiazepine (PBD) monomer DRH-417 (NSC 709119).

The pyrrolobenzodiazepine monomer DRH-417 is a member of the anthramycin group of anti-tumor antibiotics that bind covalently to the N2 of guanine within the minor groove of DNA. DRH-417 emerged from the EORTC-Drug Discovery Committee and NCI 60 cell line in vitro screening programs as a potent antiproliferative agent with differential sensitivity towards certain cancer types such as melanoma, breast and renal cell carcinoma (mean IC(50) = 3 nM). DRH-417 was therefore tested for in vivo activity. The maximum tolerated dose (MTD) was established as 0.5 mg/kg given i.p. Marked anti-tumor activity was seen in two human renal cell cancers, one breast cancer and a murine colon tumor model (p<0.01). A selective HPLC (LC/MS) analytical method was developed and plasma pharmacokinetics determined. At a dose of 0.5 mg kg(-1), the plasma AUC was 540 nM h (197.1 ng h ml(-1)) and the peak plasma concentration (171 nM [62.4 ng ml(-1)]) occurred at 30 min., reaching doses levels well above those needed for in vitro antiproliferative activity. Genomic profiling of in vivo sensitive tumors revealed that the latter have an activated insulin-like growth factor signaling pathway.

Anticancer activity of a lectin-rich mistletoe extract injected intratumorally into human pancreatic cancer xenografts.

BACKGROUND: In single case observations, tumour remissions after intratumoral injections of mistletoe extracts have been described. MATERIALS AND METHODS: We investigated the antitumour activity of intratumorally (i.t.)-injected lectin-rich mistletoe extract at different dosages and i.t.-injected mistletoe lectin I in comparison to intravenous (i.v.) Gemcitabine and i.t. treatment with placebo in a human pancreatic cancer xenograft. RESULTS: In a preliminary dose-response experiment, the most marked tumour inhibition was induced when mistletoe extract was given at 8 mg/kg body weight (BW) and mistletoe lectin I at 5.3 microg/kg BW. In a second experiment, bi-weekly i.t. injections of mistletoe extract over 8 weeks resulted in a very high antitumour activity with an optimal T/C value (=median relative tumour volume of the test group vs. the control) of 0.4% combined with 3/8 partial and 3/8 complete remissions. Gemcitabine was less active with 2/8 partial and 1/8 complete remissions and an optimal TIC of 4.6%. CONCLUSION: I.t.-injected lectin-rich mistletoe extract should be further evaluated in patients with inoperable locally advanced pancreatic cancer.

Clonogenic assay with established human tumour xenografts: correlation of in vitro to in vivo activity as a basis for anticancer drug discovery.

Pluripotent cells can be grown in clonogenic assays. The tumour stem-cell fraction, which accounts for <0.4% of the total cells, and which is considered the most relevant cell type in the development of metastases and recurrences, is able to divide and to form colonies in a semisolid matrix (agar or methylcellulose). Major applications of the tumour clonogenic assay (TCA) are chemosensitivity testing of tumours and xenografts, and for assessments within drug discovery programmes. Of critical relevance for the usefulness of the TCA is whether it can predict sensitivity or resistance towards clinically used agents. When we compared the response of human tumours established as xenografts in nude mice in the TCA in vitro to that of the clinical response, 62% of the comparisons for drug sensitivity, and 92% of the comparisons for drug resistance were correct. The same percentage of true/false observations was found when tumours were tested after serial passage in nude mice in the TCA in vitro and their response compared to in vivo activity in corresponding xenografts (60% and 90%, respectively). The highest correct predictive values were, however, found when the clinical response of tumours was compared to their explants established in the nude mouse and treated in vivo. Of 80 comparisons performed, we observed a correct prediction for tumour resistance in 97% and for tumour sensitivity in 90%. In our opinion, the TCA with established human tumour xenografts has an important role in current drug discovery strategies. We therefore included the TCA as secondary assay in our approach to anticancer drug discovery and found that a number of novel agents were active; these are now in advanced preclinical development or clinical trials. Thus, the tumour clonogenic assay has proven predictive value in the chemosensitivity testing of standard and experimental anticancer drugs.

Antitumor activity of imidazothioxanthones in murine and human tumor models in vitro and in vivo.

BACKGROUND: A new series of imidazothioxanthones has recently been synthesized as potential anticancer agents with the aim of overcoming drug resistance. The route of synthesis and DNA-binding properties of the compounds were reported previously. This paper describes the general structure-activity relationships for the class of imidazothioxanthones in panels of human and murine tumor cell lines in vitro, and the in vivo activity against human and murine solid tumors of the most potent compound, N-[3-(Dimethylamino)propylo]-11-oxo-11H-benzothiopyrano [3',2':2,3]pyrido[1,2-a]imidazo-2-carboxamide (10a). In addition, the interaction between compound 10a and DNA is also considered in terms of molecular mechanics methods and flexible docking techniques. MATERIALS AND METHODS: The cytotoxicity of compounds 10a, 11-oxo-N-[2-(pyrrolidino)ethylo]-11H-benzothiopyrano [3',2':2,3]pyrido[1,2-a]imidazo-2-carboxamide, 11-oxo-N-[2-(piperidino)ethylo]-11H-benzothiopyrano [3',2':2,3]pyrido[1,2-a]imidazo-2-carboxamide and N-[2-(morpholino)ethylo]-11-oxo-11H-benzothiopyrano [3',2':2,3]pyrido[1,2-a]imidazo-2-carboxamide (10c-10e) was assessed in human tumor cell lines and xenografts using the sulforhodamine B assay, MTT assay and the clonogenic assay. The human ovarian xenograft, PXN/109TC, two human breast carcinomas, MT-1 and MCF-7, and the murine colon adenocarcinoma, MAC15A were used for the in vivo testing of compound 10a. In addition, the interaction between compound 10a and DNA is also considered in terms of molecular mechanics methods and flexible docking techniques. RESULTS: Two compounds, 10a and 10c, showed cytotoxic activity below 10 mM in the NCI in vitro screen of 60 human tumor cell lines. The IC50 value of compound 10a was 6.8 mM and that of 10c, 8.3 mM. In addition, both compounds possessed differential activity against leukemia, colon and mammary cancer. The activity pattern was confirmed in two further screens using monolayer and clonogenic, assays. In vivo antitumor studies showed that 10a was active against the human mammary carcinoma MT-1 and murine colon cancer MAC15A. Marginal activity was observed in human ovarian cancer model PXN/109T/C and the compound was inactive in human mammary cancer MCF-7. CONCLUSION: The results warrant further in vivo testing of 10a in additional human solid tumor models. The molecular modeling showed that the planarity of the chromophore and the side-chain conformation could assist the insertion of compound 10a between the base pairs of the double helix. On the other hand, docking to the nucleotide sequence GGAATTGCCTCA suggested that the molecule could also act as a minor groove binder.

No evidence of stimulation of human tumor cell proliferation by a standardized aqueous mistletoe extract in vitro.

The in vitro antiproliferative or stimulatory activity of an aqueous mistletoe extract (AME) with a defined content of bioactive mistletoe lectin (ML) was investigated in 6 human tumor cell lines, including two melanomas and leiomyosarcomas, each of which had previously been reported to show evidence of growth stimulation if treated with low concentrations of isolated ML. The effects of AME were compared to that of the standard cytotoxic agent adriamycin (ADR) using the well established propidium iodide and sulforhodamin B proliferation assays. The AME concentrations used ranged from 0.5 pg to 5 ng (0.82 fMol-85 pM) bioactive ML/ml in melanoma (HT-144, SK-MEL-28) and leiomyosarcoma (SK-MLS-1, S-UT-1B) cell lines and from 0.1-100 ng ML/ml (1.7 pM-1.7 nM) in MCF-7 breast cancer and SW620 colon carcinoma cell lines, respectively. The influence of AME on cell growth was determined at various time-points from 24 hours to 6 days of exposure. We found a time- and cell line-dependent inhibition of tumor cell growth, but no reproducible stimulation of tumor cell proliferation. Inhibitory concentrations 50% (IC50) for e.g. the SK-MEL-28 melanoma cell line, decreased from 4.1 ng ML/ml at 24 hours to 0.16 ng ML/ml at 72 hours and 0.18 ng ML/ml at 5 days. Our data clearly demonstrate that, by applying scientifically valid methods and procedures, the standardized AME did not stimulate tumor cell proliferation but showed time- and concentration-dependent antiproliferative effects.

5-Fluorouracil in vesicular phospholipid gels for anticancer treatment: entrapment and release properties.

Vesicular phospholipid gels (VPG), i.e. highly concentrated liposomal dispersions, are suitable for entrapping substances such as anticancer drugs with particular high encapsulation efficiencies (EE). We prepared different formulations of VPG with 30% (w/w) lipid containing 5-fluorouracil (5-FU) by high pressure homogenization and analysed their EE and drug release. Using mixtures of hydrogenated soy phosphatidylcholine and cholesterol with molar ratios ranging from 55/45 to 75/25, a decreasing amount of cholesterol correlated with an increasing EE, which is probably due to a reduced amount of smaller vesicles and number of lamellae. Using a 5-FU solution of pH 8.6 for VPG preparation, an EE of approximately 40% was found after redispersion of the gel to a liposomal dispersion and separation of free drug from liposomal drug by size exclusion chromatography. The reduced EE for preparations with lower pH values was attributed to a fast initial drug release due to the increased drug lipophilicity below the pK(a) value of 8. After redispersion of a VPG of pH 8.0, an initially faster release of about a third of the entrapped drug was found during the first 20 min, followed by stable entrapment over many hours. The rapid initial release may be due to the portion of liposomes smaller than 40 nm in diameter, determined by photon correlation spectroscopy. Cryo electron microscopic pictures show a lentil-like shape of these small liposomes. The membrane defects on the edges are probably the reason for the very high initial drug release rate. The half-life time of the release of 5-FU from intact FU-VPG at both pH 7.4 and 8.0 was found to be in the order of 4-5 h and the kinetics are typical for matrix-controlled drug diffusion. The in vitro data of 5-FU loaded VPG suggest their applicability as implants with controlled release properties or, after redispersion, as intravenously injected liposomal formulations.

Change in pharmacokinetic and pharmacodynamic behavior of gemcitabine in human tumor xenografts upon entrapment in vesicular phospholipid gels.

PURPOSE: The in vivo pharmacokinetics (PK), biodistribution and antitumor activity of a new liposomal formulation of gemcitabine (GemLip) were compared to the conventional (clinical) formulation of gemcitabine (GemConv). METHODS: Gemcitabine was entrapped in a vesicular phospholipid gel (VPG) consisting of densely packed liposomes. Redispersed VPG containing GemLip consisted of 33% liposomally entrapped and 67% free gemcitabine. The in vivo efficacies of GemLip and GemConv were compared using the subcutaneously growing human soft tissue sarcoma SXF 1301 and the orthotopically growing human bladder cancer BXF 1299T. PK and biodistribution were evaluated using radiolabeled drug and lipid in SXF 1301 tumor-bearing nude mice. RESULTS: GemLip was highly active in SXF 1301 at a gemcitabine dose of 6-9 mg/kg (days 1, 8 and 15; dose near the MTD). In the 6-mg/kg groups, complete tumor remissions were observed in seven of eight mice. Equimolar doses of GemConv resulted in only moderate tumor growth inhibition. Even at equitoxic doses (360 mg/kg given on days 1, 8 and 15, or 120 mg/kg on days 1, 5 and 8) GemConv was less active than GemLip. Furthermore, GemLip was active in the orthotopically growing BXF 1299T bladder cancer model at 6 mg/kg and prevented distant organ metastasis. In the PK study, GemLip achieved a 35-fold higher plasma AUC (1680 mg x h/ml) than GemConv (47.6 mg x h/ml). The serum half-lives were 0.15 h for free gemcitabine and 13.3 h for liposomal gemcitabine (6 mg/kg each i.v.). Moreover, gemcitabine levels in tumors were fourfold higher following injection of GemLip than following injection of GemConv. CONCLUSIONS: GemLip is a highly effective gemcitabine delivery system which results in superior gemcitabine pharmacodynamics and PK than GemConv. The enhanced in vivo efficacy might be explained by sustained release and passive tumor targeting.

Synthetic 2-aroylindole derivatives as a new class of potent tubulin-inhibitory, antimitotic agents.

A new class of simple synthetic antimitotic compounds based on 2-aroylindoles was discovered. (5-Methoxy-1H-2-indolyl)-phenylmethanone (1) as well as analogous 3-fluorophenyl- (36) and 3-methoxyphenyl (3) derivatives displayed high cytotoxicity of IC(50) = 20 to 75 nM against the human HeLa/KB cervical, SK-OV-3 ovarian, and U373 astrocytoma carcinoma cell lines. The inhibition of proliferation correlated with the arrest in the G2/M phase of the cell cycle. In in vitro assays with tubulin isolated from bovine brain, in general antiproliferative activity correlated with inhibition of tubulin polymerization. Thus, the antimitotic activity of 2-aroylindoles is explained by interference with the mitotic spindle apparatus and destabilization of microtubules. In contrast to colchicine, vincristine, nocodazole, or taxol, 1 did not significantly affect the GTPase activity of beta-tubulin. Interestingly, selected compounds inhibited angiogenesis in the chorioallantoic membrane (CAM) assay. In xenograft experiments, 1 was highly active after oral administration at 200 mg/kg against the human amelanocytic melanoma MEXF 989 in athymic nude mice. We conclude, that 2-aroylindoles constitute an interesting new class of antitubulin agents with the potential to be clinically developed for cancer treatment.

Design and optimization of 20-O-linked camptothecin glycoconjugates as anticancer agents.

To improve the biological profile of 20(S)-camptothecin, a novel class of 20-O-linked camptothecin glycoconjugates has been designed for preferential cellular uptake into tumor cells by an active transport mechanism. Such conjugates have been optimized for enhanced solubility, stabilization of the camptothecin lactone ring, sufficient hydrolytic and proteolytic stability, and for an overall improvement in tumor selectivity. The constitution of the peptide spacer has a major impact on stability and biological activity of the conjugates both in vitro and in vivo. Glycoconjugates 17-22 with valine residues at the linkage position to camptothecin are sufficiently stable and show good antitumor activity in vitro against HT29 and other tumor cell lines. Fluorescence microscopy and flow cytometry experiments indicate that glycoconjugates such as 19 are taken up into lysosomal compartments of the tumor cell line HT29 by an active transport mechanism. The steric configuration of the particular amino acid residues linked to the camptothecin moiety has a major impact on the in vivo activity of the corresponding glycoconjugates in the breast cancer xenograft MX-1 model. Inhibiting tumor growth by >96%, the glycoconjugates 19 and 21 show the best activity in this particular model and have been investigated more extensively. The glycoconjugate 19 compares favorably to topotecan 4 and glycoconjugate 21 with respect to toxicity against hematopoietic stem cells and hepatocytes. Based on its profile, 19 has been selected for clinical trials.

Genotyping of NAD(P)H:quinone oxidoreductase (NQO1) in a panel of human tumor xenografts: relationship between genotype status, NQO1 activity and the response of xenografts to Mitomycin C chemotherapy in vivo(1).

Pharmacogenetic analysis of polymorphisms in drug metabolizing enzymes is currently generating considerable interest as a means of individualizing patient therapy. Recent studies have suggested that patients that are homozygous for a polymorphic variant (a C to T transition at position 609 of the cDNA sequence) of the enzyme NAD(P)H:quinone oxidoreductase (NQO1) may be resistant to Mitomycin C (MMC). Genotyping of a panel of 54 human tumor xenografts by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP), classified tumors as wild type (40/54), heterozygotes (11/54), and homozygous mutants (3/54). Previously, 37 of these tumors had been characterized in terms of their response to MMC in vivo, and in this study, a further nine tumor xenografts have been characterized in terms of their response to MMC. No correlation could be found between the NQO1 polymorphic status of xenografts and their response to MMC in vivo. In terms of genotype/phenotype relationships, NQO1 activity in tumors genotyped as wild type, heterozygotes, and homozygous mutants were 311.1 +/- 421.9 (N = 40), 76.9 +/- 109.5 (N = 11), and 0.2 +/- 0.17 (N = 3) nmol/min/mg, respectively. Genotyping of patients may provide a useful initial step in identifying patients who are unlikely to benefit from quinone-based chemotherapy. In the case of MMC, however, the work presented here demonstrates that genotyping of individuals with respect to NQO1 is unlikely to be beneficial in terms of predicting tumor responses to MMC.

Lycobetaine acts as a selective topoisomerase II beta poison and inhibits the growth of human tumour cells.

The phenanthridine alkaloid lycobetaine is a minor constituent of Amaryllidaceae. Inhibition of cell growth was studied in the clonogenic assay on 21 human tumour xenografts (mean IC(50) = 0.8 microM). The growth of human leukaemia cell lines was also potently inhibited (mean IC(50) = 1.3 microM). Athymic nude mice, carrying s.c. implanted human gastric tumour xenograft GXF251, were treated i.p. with lycobetaine for 4 weeks, resulting in a marked tumour growth delay. Lycobetaine was found to act as a specific topoisomerase II beta poison. In the presence of calf thymus DNA, pure recombinant human topoisomerase II beta protein was selectively depleted from SDS-gels, whereas no depletion of topoisomerase II alpha protein was observed. In A431 cells immunoband-depletion of topoisomerase II beta was induced, suggesting stabilization of the covalent catalytic DNA-intermediate in living cells. It is reasonable to assume that this mechanism will cause or at least contribute significantly to the antitumour activity.

2-benzoxazolyl and 2-benzimidazolyl hydrazones derived from 2-acetylpyridine: a novel class of antitumor agents.

Here we describe the effects of novel benzoxazol-2-yl and benzimidazol-2-yl hydrazones derived from 2-pyridinecarbaldehyde and 2-acetylpyridine. The IC(50) values for inhibition of cell proliferation in KB-3-1, CCRF-CEM, Burkitt's lymphoma, HT-29, HeLa, ZR-75 and MEXF276L by most of the novel compounds are in the nanomolar range. In colony-forming assays with human tumor xenografts the compounds 2-actylpyridine benzoxazol-2-ylhydrazone (EPH52), 2-acetylpyridine benzoimidazol-2-ylhydrazone (EPH61) and 2-acetylpyridine 1-methylbenzoimidazol-2-ylhydrazone (EPH116) exhibited above-average inhibition of colon carcinoma (IC(50) = 1.3-4.56 nM); EPH52 and EPH116 also exhibited above-average inhibition of melanoma cells. As shown with human liver microsomes, EPH116 is only moderately metabolized. The compound inhibited the growth of human colon cancer xenografts in nude mice in a dose-dependent manner. Thiosemicarbazones derived from 2-formylpyridines have been shown to be inhibitors of ribonucleotide reductase (RR). The following results show that RR is not the target of the novel compounds: cells overexpressing the M2 subunit of RR and resistant to the RR inhibitor hydroxyurea are not cross-resistant to the novel compounds; inhibition of RR occurs at 6- to 73-fold higher drug concentrations than that of inhibition of cell proliferation; the pattern of cell cycle arrest in S phase induced by the RR inhibitor hydroxyurea is not observed after treatment with the novel compounds; and a COMPARE analysis with the related compounds 2-acetylpyrazine benzothiazol-2-ylhydrazone (EPH95) and 3-acetylisoquinoline benzoxazol-2-ylhydrazone (EPH136) showed that the pattern of these compounds is not related to any of the standard antitumor drugs. Therefore, these novel compounds show inhibition of colon cancers and exhibit a novel mechanism of action.

Antiproliferative activity of an aqueous mistletoe extract in human tumor cell lines and xenografts in vitro.

The in vitro antiproliferative activity of an aqueous mistletoe extract (AME) with a defined content of bioactive mistletoe lectin (ML) was tested in 25 human tumor cell lines, including 20 solid and 5 hematological malignancies and 47 human tumor xenografts. The antiproliferative activity of AME was compared to that of the standard cytotoxic agent doxorubicin (CAS 23214-92-8, adriamycin, ADR) using the sulforhodamin B, propidium iodide and soft agar colony forming assays, respectively. AME was highly cytotoxic in solid human tumors with mean IC70 values in the range of 0.17-1 ng ML/ml (2.8-17 pmol bioactive ML). On a molar basis, AME was 3 to 4 logs more potent than ADR and showed differential cytotoxicity towards tumors of the breast, small cell and non-small cell lung, prostate and renal cell cancers. AME was also highly active in hematological malignancies with steep dose response curves resulting in mean IC70 values of 0.12 ng ML/ml (2 pmol). The acute lymphoblastic leukemia cell line HL-60 was the most sensitive, the histiocytic lymphoma cell line U937 the most resistant hematological malignancy. It is important to stress that AME did not induce a biologically relevant increase of cell proliferation in any of the tumor cell lines tested. Our data suggest that AME has in vitro antitumor profiles similar to those of classical anticancer agents. Clear dose-response relationships were found in all of the performed experiments and interesting differential cytotoxicity patterns were observed. Experiments with sensitive tumor types identified in these in vitro studies are currently ongoing in order to demonstrate the anticancer activity of AME in different animal tumor models.

Anticancer activity of an aqueous mistletoe extract (AME) in syngeneic murine tumor models.

Mistletoe extracts have been used for decades for non-specific stimulation of the immune system in cancer therapy. Mistletoe lectins (ML) have been identified as the active principle with cytotoxic and immunomodulatory potencies. In the present in vivo experiments, the anticancer effects of an aqueous mistletoe extract (AME) were investigated in different subcutaneously growing syngeneic murine tumors such as Renca renal cell carcinoma, C8 colon 38 carcinoma, F9 testicular carcinoma, B16 melanoma and Lewis lung carcinoma. The animals used were immunocompetent mice of different strains (C57BL/6, BALB/c), depending on the type of tumor tested. After tumor transplantation, the mice were treated with AME at dose levels corresponding to 0, 0.3, 3, 30 or 300 ng ML/kg/d by the i.p. or s.c. route for a maximum of 4 consecutive weeks. The tumor volume was determined by serial caliper measurements and expressed relative to controls. Significant tumor growth inhibition was observed with the Renca , C8 colon 38 and F9 testicular carcinomas at 30 and 300 ng ML/kg/d. These findings were confirmed in independent repeat experiments. No inhibitory effects were seen with the Lewis lung carcinoma and B16 melanoma under the conditions described above. In conclusion, AME showed in vivo anticancer activity in different transplantable syngeneic murine tumor models following repeated parenteral treatment. In view of the low dose levels used, the effects are most likely due to the immunostimulatory rather than to the cytotoxic potencies of AME.

Synthesis, cytotoxicity, and antitumor activity of copper(II) and iron(II) complexes of (4)N-azabicyclo[3.2.2]nonane thiosemicarbazones derived from acyl diazines.

A series of thiosemicarbazones (TSCs) (bearing a (4)N-azabicyclo[3.2.2]nonane moiety) derived from 3-acylpyridazines, 4-acetylpyrimidines, and 2-acetylpyrazines (1-8) were synthesized as potential antitumor agents. TSCs 1-8 exhibited potent cytotoxic activity against human acute lymphoblastic leukemia CCRF-CEM cells (IC(50) = 0.05-0.77 microM) and colon adenocarcinoma HT-29 cells (IC(50) = 0.011-2.22 microM). Copper II complexes of TSCs 1-8 showed significant improvement in cytotoxic activity against HT-29 cells (IC(50) = 0.004-1.51 microM) by a factor of 3. However, complexation of ligands 1, 2, 4, and 6 with Fe(II) results in lowering of cytotoxic activity by a factor of approximately 7. In clonogenic assays involving human tumor cells of different tumor origins, compounds 5, 7, 8, and their copper complexes 5Cu(II), 7Cu(II), and 8Cu(II) exhibited remarkable cytotoxic activities with mean IC(50) values of 6, 0.18, 1, 1, 0.37, and 0.37 nM, respectively. In particular, the compounds were highly effective against human colon carcinoma and large and small cell lung carcinoma cells. The TSC derivative 5 was evaluated in vivo in nude mice bearing LXFL 529 human large cell lung carcinoma cells. With respect to antitumor activity, application of 30 mg/kg/d resulted in moderate inhibition (42%) of tumor growth. No effect on tumor growth was observed at a dose of 10 mg/kg/d. However, a dose of 40 or 60 mg/kg/d resulted in 50 and 75% death, respectively, in the treated mice, indicating the high toxicity of these compounds. Using human liver microsomes, compound 5 was found to be rapidly and highly metabolized in vitro. In actual fact, only 2% of the unmetabolized compound could be detected in the incubation medium after 5 min. The IC(50) for cell proliferation (0.006-0.022 microM) elicited by these compounds is much lower than that of the inhibition of [(14)C]cytidine incorporation into DNA (0.18-3.32 microM). These compounds are also noncell cycle specific agents. Interestingly, compounds 5, 5Cu(II), and 8 were found to be potent inducers of apoptosis in Burkitt's lymphoma cells.

Pre-clinical evaluation of a methotrexate-albumin conjugate (MTX-HSA) in human tumor xenografts in vivo.

Methotrexate covalently bound to human serum albumin in a 1:1 molar ratio (MTX-HSA) is a new macromolecular drug which is currently being studied in phase I clinical trials by the German Association for Medical Oncology (AIO) Phase I/II study group. Previous studies have shown that MTX-HSA differs favorably from unbound MTX in terms of plasma half-life time, tumor accumulation of albumin and uptake mechanisms into cancer cells. To achieve optimal drug efficacy, repeated treatment cycles were necessary. To evaluate the anti-tumor activity of MTX-HSA and MTX in pre-clinical in vivo models, we selected 7 solid human tumor xenografts growing s.c. in nude mice and administered drug either i.p. or i.v. weekly for 3 weeks. The maximal tolerated dose (MTD) of MTX-HSA in nude mice was 12.5 mg/kg given i.p. on days 1, 8 and 15, whereas the MTD for free MTX was 100 mg/kg given i.v. MTX-HSA was significantly more active (p > 0.01) than MTX in 3 models. In the soft tissue sarcoma SXF 1301, MTX-HSA effected complete remission/cure after a single injection, whereas free MTX resulted in short-lasting, partial tumor regression. In the prostate-cancer model PRXF PC3M, MTX-HSA produced growth inhibition of 92.8% of control or an optimal test/control (T/C) of 7.2% compared to a T/C of 20.8% for MTX (p = 0.05). In the osteosarcoma model SXF 1410, optimal T/C values were 10.2% and 14.5%, respectively (p = 0.025). In lung cancers LXFE 409 and LXFL 529, bladder cancer BXF 1258 and breast cancer MAXF 449, both compounds were inactive. The improved therapeutic effects seen in 3 xenograft models under MTX-HSA treatment are promising and might be due to specific accumulation of the compound in solid tumors owing to their enhanced permeability and retention effect. Thus, clinical development of MTX-HSA will continue and sarcomas as well as prostate cancers will be included as potential target tumors for upcoming clinical phase II trials.

A short and efficient transformation of rhamnose into activated daunosamine, acosamine, ristosamine and epi-daunosamine derivatives, and synthesis of an anthracycline antibiotic acosaminyl-epsilon-iso-rhodomycinone.

3-Amino-2,3,6-trideoxyhexopyranoses are essential constituents of most anthracycline antitumour antibiotics. For an investigation of structure-activity relationships, the four diastereomeric amino sugars daunosamine, acosamine, ristosamine, and epi-daunosamine were synthesised in short and efficient routes starting from commercially available rhamnose. Several glycosyl donors were provided and their use was exemplified in the synthesis of acosaminyl-epsilon-isorhodomycinone.