In vitro activities of crude extracts and triterpenoid constituents of Dichapetalum crassifolium Chodat against clinical isolates of Schistosoma haematobium

Dichapetalum crassifolium Chodat (Dichapetalaceae) is widely distributed in Africa, Tropical Asia and Latin America. As part of our quest for potential bioactive lead compounds for various neglected tropical diseases, we report the anti-schistosomal potential of the crude extracts and chemical constituents of the stems and roots of Dichapetalum crassifolium. Column chromatography of extracts of the stems and roots led to the isolation and identification of three oleanane-type triterpenoids, friedelan-3β-ol (1), friedelan-3-one (2), and maslinic acid (3); the ursane-type tritepenoid, pomolic acid (4) and the dammarane-type tetracyclic triterpenoids, dichapetalin A (5) and dichapetalin M (6). Dichapetalin A was isolated from only the roots. Isolated compounds were identified by comparison of their physico-chemical and spectral data with published data. The highest in vitro anti-schistosomal activity (IC₅₀) of the crude extracts against clinical isolates of Schistosoma haematobium (Bilharz 1852) was 248.6 μg/ml for the ethyl acetate extract of the root while dichapetalin A gave the highest activity at 151.1 μg/ml among the compounds compared with the 15.5 μg/ml for the standard drug, praziquantel. The rest of the compounds showed activities in the order 177.9, 191.0, and 378.1 μg/ml respectively for mixture of β-sitosterol/stigmasterol, dichapetalin M and friedelan-3-one. The least active extract was the methanol extract of the stem (893.7 μg/ml). The constituents of D. crassifolium showed activity against the S. haematobium that are below praziquantel. It is envisaged that the presence of multiple layers and the minute sizes of pores in the egg shells, may preclude penetration of eggs by the compounds.

Isolation, characterization, and anthelminthic activities of a novel dichapetalin and other constituents of Dichapetalum filicaule

CONTEXT

Dichapetalum filicaule Breteler (Dichapetalaceae) is a rare species occurring only in Côte d'Ivoire and Ghana. Although research on several species of the genus has produced interesting bioactive compounds, particularly the Dichapetalins, a novel class of triterpenoids with antineoplastic properties, there is virtually no information on the ethnobotanical uses and chemical constituents of D. filicaule.

OBJECTIVE

The phytochemical and anthelminthic activities of the constituents of D. filicaule were investigated.

MATERIALS AND METHODS

Chemical constituents of the petroleum ether, chloroform-acetone, and methanol root extracts of D. filicaule were isolated by column chromatography and characterized by their physico-chemical properties, 1-D and 2-D NMR spectroscopy and mass spectrometry. In vitro anthelminthic activity of the extracts and compounds against the human hookworm, Necator americanus, Stiles 1902 (Nematoda: Ancylostomatidae) was determined within a concentration range of 2500-250 μg/ml using the Egg Hatch Inhibition (EHI) Assay. The hookworm species were identified using a published polymerase chain reaction (PCR) method.

RESULTS

A new dichapetalin, dichapetalin X (1), together with the known dichapetalin A (2), pomolic acid (3), glycerol monostearate (4), D:A-friedooleanan-3β-ol (5), and D:A-friedooleanan-3-one (6) were isolated. Compounds 1, 2, and 4 exhibited EHI with IC50 values of 523.2, 162.4, and 306.0 μg/ml, respectively, against the hookworm. The positive control albendazole gave an IC50 value of 93.27 μg/ml.

DISCUSSION AND CONCLUSION

This is the first report of the phytochemical investigation of D. filicaule. The study has yielded a new dichapetalin and also demonstrated the potential anthelminthic properties of the constituents.

Diprenylated Indole Alkaloids from Fruits of Hexalobus monopetalus

New hexalobine type alkaloid, 5-(2″,3″-epoxy-3″-methylbutyl)-3-(3'-hydroxy-3'-methyl-1'-acetyloxy-but-2'-yl)indole (1) alongside the known hexalobines 3-(2',3'-dihydroxy-3'-methylbutyl)-5-(3″-methylcrotonoyl) indole (2), 3,5-hexalobine C (3) and 3,5-hexalobine D (4) were isolated from fruits of Hexalobus monopetalus. Compounds 3 and 4 exhibited antifungal activity against Candida albicans.

Antifungal Enantiomeric Styrylpyrones from Sanrafaelia ruffonammari and Ophrypetalum odoratum

Phytochemical investigation of Sanrafaelia ruffonammari Verd and Ophrypetalum odoratum Diels that belongs to the rare genera confined to East African coastal forests led to the isolation of enantiomeric styrylpyrone dimer, (±)-5-methoxy-7-phenyl-[4-methoxy-2-pyronyl]-1-(E)-styryl-2-oxabicyclo-[4.2.0]-octa-4-en-3-one (1) alongside (+)-6-styryl-7,8-epoxy-4-methoxypyran-2-one (2) and the enantiomeric (+)- (3) and (-)-6-styryl-7,8-dihydroxy-4-methoxypyran-2-ones (4). Their structures were established by means of spectroscopic methods. In this paper we reveal for the first time the occurrence of styrylpyrones in East African biodiversity. (+)-6-Styryl-7,8-epoxy-4-methoxypyran-2-one (2) and the dihydroxystyrylpyrone enantiomer (3) showed in vitro antifungal activity against Candida albicans at a concentration of 24.4 and 26.2 µM with zones of inhibition of 17 and 9 mm, respectively. Compound 2 exhibited strong activity in the brine shrimp test with LC50 = 1.7 µg/mL. Their high cytotoxic and antifungal activities render them candidates for further scientific attention for drug development programs against cancer and microbial infections.

Biotransformation of 21-O-acetyl-deoxycorticosterone by cell suspension cultures of Digitalis lanata (strain W.1.4)

Cell cultures of Digitalis species are known to accept exogenous substrates for biotransformation reactions. We here report the biotransformation of 21-O-acetyl-deoxycorticosterone (1) by cell suspension cultures of Digitalis lanata strain W.1.4. Nine derivatives of 1 were obtained and their chemical structures determined by spectroscopic methods. 2β-Hydroxylation and C-21-glucosylation of the steroidal nucleus were described for the first time in suspension-cultured plant cells. Steroid 5α- and 5β-reduction products were also observed. Among the compounds isolated and structures elucidated were 2β,3β,21-trihydroxy-4-pregnen-20-one, 2β,3α,21-trihydroxy-4-pregnen-20-one and 3β,21-dihydroxy-5α-pregnan-20-one-3β-O-β-glucoside.

A simple chemical method for synthesizing malonyl hemiesters of 21-hydroxypregnanes, potential intermediates in cardenolide biosynthesis

A simple and versatile method for the chemical synthesis of 21-hydroxypregnane 21-O-malonyl hemiesters which may be important intermediates of cardenolide biosynthesis is described. Starting from commercial beta-methyldigitoxin, acid hydrolysis followed by 3beta-O-acetylation and ozonolysis with reductive cleavage of the ozonides afforded 3beta-acetoxy-5beta-pregnane-14beta,21-diol-20-one which was finally converted into the target compound by treatment with malonyl chloride. The malonylation protocol was optimized using deoxycorticosterone (DOC) as the pregnane educt.

Molecular building kit of fused-proline-derived peptide mimetics allowing specific adjustment of the dihedral Psi angle

Proline-derived peptide mimetics have become an area of paramount importance in peptide and protein chemistry. Since protein crystal structures frequently display Psi angles of 140-170 degrees for prolyl moieties, our intention was to design a completely novel series of 2,3-fused-proline-derived lactams covering this particular conformational space. Extending our recently described toolset of spirocyclic reverse-turn mimetics, we synthesized pyrrolidinyl-fused seven-, eight-, and nine-membered unsaturated lactam model peptides taking advantage of Grubbs' ring-closing metathesis. Investigating the seven-membered lactam 3a by means of IR and NMR spectroscopy and semiempirical molecular dynamics simulations, we could not observe a U-turn conformation; however, increasing the ring size to give eight- and nine-membered congeners revealed moderate and high type IotaIota beta-turn inducing properties. Interestingly, the conformational properties of our model systems depend on both the ring size of the fused dehydro-Freidinger lactam and the position of the endocyclic double bond. Superior reverse-turn inducing properties could be observed for the fused azacyclononenone 3e. According to diagnostic transanular NOEs, a discrete folding principle of the lactam ring strongly deviating from the regioisomeric lactams 3c,f explains the conformational behavior. Hence, we were able to establish a molecular building kit that allows adjustments of a wide range of naturally occurring proline Psi angles and thus can be exploited to probe molecular recognition and functional properties of biological systems.

SCRF-DFT and NMR Comparison of Tetracycline and 5a,6-Anhydrotetracycline in Solution

A combination of structures, energies, and spectral data calculated using density functional theory (DFT) with experimental NMR data has been used to assign conformational equilibria for tetracycline and 5a,6-anhydrotetracycline in water at pH 1, 7, and 10 and in chloroform (5a,6-anhydrotetracycline) and methanol (tetracycline). The results suggest that tetracycline always prefers the extended conformation but that 5a,6-anhydrotetracycline exists in water as a mixture of the two conformers and in chloroform exclusively in the twisted conformation. The conformational equilibria are also shown to be pH dependent.

C18 tetraynoic fatty acids and essential oil composition of Mkilua fragrans

The fatty acids 17,18-dihydroxyoctadeca-9,11,13,15-tetraynoic acid (mkiluaynoic acid A) and 18-hydroxyoctadeca-9,11,13,15-tetraynoic acid (mkiluaynoic acid B), 5,7,3',4'-tetrahydroxyflavanol, 3,4-dihydroxybenzoic acid and a mixture of stearic and oleic acids were isolated from fruits and stem barks of Mkilua fragrans (Annonaceae). Mkiluaynoic acid A exhibited antifungal activity against Candida albicans comparable with that of the standard antifungal agent Ketoconazole. Structural determination was achieved by analysis of spectroscopic data. The flower stalks yielded essential oils that mainly consisted of sesquiterpenoids as revealed by GC-MS analysis, whereby 14 sesquiterpenes and four other compounds were identified.

Cyclohexanoid protoflavanones from the stem-bark and roots of Ongokea gore

Phytochemical investigation of root and stem-bark of the West African medicinal plant Ongokea gore resulted in the isolation of four novel flavonoids with an unusual cyclohexyl substituent instead of the common aromatic ring B. The structures of the isolated compounds were elucidated by spectroscopic methods, mainly 1D and 2D NMR, and subsequently, the structures were corroborated by chemical conversion to (-)-(S)-sakuranetin. The absolute configurations, and preferred conformations were determined by NOE experiments and CD measurements.

Two glucosylated abscisic acid derivates from avocado seeds (Persea americana Mill. Lauraceae cv. Hass)

Phytochemical investigation of avocado seed material (Persea americana Mill., Lauraceae) resulted in the isolation of two glucosylated abscisic acid derivates. One of these was not known as a natural product and can be regarded as a potential 'missing link' in abscisic acid metabolism in plants. After fractionation by high-speed countercurrent chromatography, and multiple steps of column chromatography, structures were elucidated by 1D-, 2D-NMR, electrospray-MS to be the novel beta-d-glucoside of (1'S,6'R)-8'-hydroxyabscisic acid, and (1'R,3'R,5'R,8'S)-epi-dihydrophaseic acid beta-d-glucoside. Absolute configuration was determined by circulardichroism, optical rotation, and by NOE experiments.

Radiolabelling of glycosylated MFE-23::CPG2 fusion protein (MFECP1) with 99mTc for quantitation of tumour antibody-enzyme localisation in antibody-directed enzyme pro-drug therapy (ADEPT)

MFECP1 is a glycosylated recombinant fusion protein composed of MFE-23, a high-affinity anti-carcinoembryonic antigen (CEA) single chain Fv (scFv), fused to the enzyme carboxypeptidase G2 (CPG2), and has been constructed for use in antibody-directed enzyme pro-drug therapy (ADEPT). Radiolabelling of glycosylated MFECP1 with technetium-99m was developed for the purpose of determining tumour localisation of MFECP1 in a phase I ADEPT clinical study. The method used was 99mTc-carbonyl [99mTc(H2O)3(CO)3]+ (abbreviated to TcCO) mediated labelling of 99mTc to the hexahistidine (His) tag of MFECP1. MFECP1 fusion protein was labelled with TcCO under a variety of conditions, and this was shown to be a relatively simple and robust method. Tissue biodistribution was assessed in a CEA-expressing LS174T (human colon carcinoma) nude mouse xenograft model. Tissues were taken at 1, 4 and 6 h for assessment of distribution of radioactivity and for measurement of CPG2 enzyme levels. The amount of radioactivity retained by the tumour proved to be an accurate estimation of actual measured enzyme activity, indicating that this radiolabelling method does not appear to damage the antibody-antigen binding or the enzyme activity of MFECP1. However, correlation between CPG2 enzyme activity and measured radioactivity in liver, spleen and kidney was poor, indicating retention of radioactivity in non-tumour sites but loss of enzyme activity. The high retention of technetium radioisotope in normal tissues may limit the clinical applicability of this radiolabelling method for MFECP1; however, these results suggest that this technique does have applicability for measuring the biodistribution of His-tagged recombinant proteins.

Isolation of dammarane saponins from Panax notoginseng by high-speed counter-current chromatography

The Chinese phytomedicinal formulation Sanqi Zongdai Pian, traditionally prepared from crude extracts from roots of Panax notoginseng (Araliaceae), contains highly polar dammarane saponins which were separated at a preparative scale using high-speed counter-current chromatography (HSCCC). In each operation, 283 mg methanolic extract of five tablets was separated and yielded pure 157, 17, 13 and 56 mg of ginsenoside-Rb1, notoginsenoside-R1, ginsenoside-Re and ginsenoside-Rg1, respectively, n-hexane-n-butanol-water (3:4:7, v/v/v) was used for the two-phase solvent system of the HSCCC separation. The chemical structures of three ginsenosides and one notoginsenoside were elaborated by means of electrospray ionization MS-MS and NMR analysis.

Sesquineolignans and other constituents from the seeds of Joannesia princeps

From the methanolic extract of the seeds of the Brazilian Joannesia princeps 3,3'-bisdemethylpinoresinol and six new sesquineolignans were isolated besides the known neolignans americanol A, isoamericanol A and isoamericanin A which were found to be the major constituents. A method was developed to distinguish americanol- from isoamericanol-type compounds spectroscopically.

A general approach to dehydro-Freidinger lactams: ex-chiral pool synthesis and spectroscopic evaluation as potential reverse turn inducers

Starting from natural alpha-amino acids, a practical synthesis of the dehydro-Freidinger lactams 9a-h based on the ring-closing olefin metathesis reaction was investigated. The presented examples comprise 6-, 7-, 8-, 9-, and 10-membered cyclic dipeptide mimics. Structural variations were demonstrated. We approached the metathesis precursors 8a-h employing an N-alkylation/peptide-coupling strategy. Subsequent ring closure was promoted by the ruthenium-based catalyst 10a or 10b. The resulting tetraresidue 11d was shown to undergo intramolecular hydrogen bonding based on NMR and FT-IR studies. Thus, the development of dehydro-Freidinger lactams as potential reverse turn inducers stabilizing an intramolecular NH(i+3)...CO(i) hydrogen-bond was demonstrated.

Reaction of folic acid with reducing sugars and sugar degradation products

The reaction of folic acid with reducing sugars (nonenzymatic glycation) under conditions that can occur during food processing and preparation was studied by high-performance liquid chromatography with diode array detection. N-(p-Aminobenzoyl)-L-glutamic acid, a well-established oxidation product, was detected in the reaction mixtures. Furthermore, a new product was isolated and identified as N2-[1-(carboxyethyl)]folic acid (CEF). CEF was the main product that was formed by the nonenzymatic glycation of folic acid. For preparation, N2-[1-(carboxyethyl)]folic acid was obtained in high yields when folic acid and dihydroxyacetone (DHA), a sugar degradation product, were heated at 100 degrees C in phosphate buffer. Mixtures of folic acid and different sugars or DHA were heated under variation of reaction time and temperature, and CEF was quantified. Up to 50% of the vitamin was converted to CEF, with highest yields formed from maltose (49%) and lactose (43%).

Biokinetics of a F(ab')3 iodine-131 labeled antigen binding construct (Mab 35) directed against CEA in patients with colorectal carcinoma

An 131I labeled trivalent antigen binding construct, formed from 3 Fab' fragments of murine anti-CEA monoclonal antibody (Mab) 35, has shown favorable biokinetics in animal studies.

OBJECTIVES

The aim of this study was to evaluate biodistribution and tumor uptake of 131I-F(ab')3 in patients and its potential utility for radioimmunotherapy of CEA expressing tumors.

PATIENTS AND METHODS

Six patients (5 M, 1 F; age 62 +/- 13 y) with liver metastases of colorectal cancer, scheduled for hepatic surgery were studied by 2-3 whole body scans immediately post infusion of 111-137 MBq of 131I labeled Mab 35 F(ab')3 and up to 72 h. Circulating CEA ranged from 1.2 to 1930 ng/ml. We evaluated plasma and whole body clearance, activity accumulation by post-surgical ex-vivo tissue measurement in primary tumor (T) and metastases (M), and calculated M to blood (M/B) and M to liver (M/L) ratios.

RESULTS

All known tumor sites were detected by immunoscintigraphy and confirmed at surgery. Whole body effective T1/2 calculated in two patients was 51.5 h and 55.6 h respectively. Effective serum T1/2 was mono-exponential in 3 patients (short observation interval) with 20.9 +/- 7 h and bi-exponential in three with alpha T1/2 of 6.3 +/- 1 h and beta T1/2 of 38.6 +/- 5 h. In a patient with concomitant colic and hepatic lesions uptake of primary tumor was 0.0071% injected dose per gram of tissue (%ID/g) and mean metastases activity was 0.0275 %ID/g at 48 h. In the 3 patients who had surgery at 48 h, mean uptake in metastases and normal liver was 0.0182 %ID/g and 0.0021 %ID/g, respectively (M/L 8.67). In the single subject followed until 7 days post infusion, residual activity in liver metastases was 10 times higher than in normal parenchyma.

CONCLUSIONS

Tumor uptake and tumor to blood ratio, as well as serum clearance of the triconstruct are similar to those observed with intact iodinated anti-CEA antibodies. In the patient studied for 7 days the tumor residence time was favorable. Further improvements, however, need to be obtained before considering this approach for radioimmunotherapy.

Tumor targeting of mono-, di-, and tetravalent anti-p185(HER-2) miniantibodies multimerized by self-associating peptides

Multimerization of antibody fragments increases the valency and the molecular weight, both identified as key features in the design of the optimal targeting molecule. Here, we report the construction of mono-, di-, and tetrameric variants of the anti-tumor p185(HER-2) single chain Fv fragment 4D5 by fusion of self-associating peptides to the carboxyl terminus. Dimeric miniantibodies with a synthetic helix-turn-helix domain and tetrameric ones with the multimerization domain of the human p53 protein were produced in functional form in the periplasm of Escherichia coli. We have directly compared these molecules and the single-chain Fv fragment in the targeting of SK-OV-3 xenografts. Tetramerization of the 4D5 antibody fragment resulted in increased serum persistence, significantly reduced off-rate, due to the avidity effect, both in surface plasmon resonance measurements on purified p185(HER-2) and on SK-OV-3 cells. The (99m)technetium-tricarbonyl-labeled tetrameric 4D5-p53 miniantibody localized with the highest dose at the tumor and remained stably bound for at least 72 h. The highest total dose was 4.3% injected dose/g after 24 h, whereas the highest tumor-to-blood ratio was found to be 13.5:1 after 48 h, with a total dose of 3.2% injected dose/g. The tetramer shows no higher avidity than the dimer, presumably since the simultaneous binding to more than two antigen molecules on the surface of cells is not possible, and the improvement in performance over the dimer must at least be due in part to the molecular weight. These results demonstrate that multimerization by self-associating peptides can be used for the development of more effective targeting molecules for medical diagnostics and therapy.

Human scFv antibody fragments specific for the epithelial tumour marker MUC-1, selected by phage display on living cells

New anti-cancer agents are being developed that specifically recognise tumour cells. Recognition is dependent upon the enhanced expression of antigenic determinants on the surface of tumour cells. The tumour exposure and the extracellular accessibility of the mucin MUC-1 make this marker a suitable target for tumour diagnosis and therapy. We isolated and characterised six human scFv antibody fragments that bound to the MUC-1 core protein, by selecting a large naive human phage display library directly on a MUC-1-expressing breast carcinoma cell line. Their binding characteristics have been studied by ELISA, FACS and indirect immunofluorescence. The human scFv antibody fragments were specific for the tandem repeat region of MUC-1 and their binding is inhibited by soluble antigen. Four human scFv antibody fragments (M2, M3, M8, M12) recognised the hydrophilic PDTRP region of the MUC-1 core protein, which is thought to be an immunodominant region. The human scFv antibody fragments were stable in human serum at 37 degrees C and retained their binding specificity. For imaging or targeting to tumours over-expressing MUC-1, it might be feasible to use these human scFv, or multivalent derivatives, as vehicles to deliver anti-cancer agents.

Aporphinoid alkaloids and other constituents from Lettowianthus stellatus

Two new aporphinoid alkaloids, f1ttowianthine and 11-methoxylettowianthine were isolated from the root bark of Lettowianthus stellatus, together with the new sesquiterpene 11-hydroxyguaia-4,6-diene and the known compounds liriodenine, (Z)-7-octadecen-9-ynoic acid, methyl (2E,6E,10R)-10,11-epoxy-3,7,11-trimethyl-2,6-dodecadienoate, methyl (2E,6E,10R)-10,11-dihydroxy-3,7,11-trimethyl-2,6-dodecadienoate , and 3,4,5-trimethoxyphenol. The structure elucidation was achieved by spectroscopic methods.

High thermal stability is essential for tumor targeting of antibody fragments: engineering of a humanized anti-epithelial glycoprotein-2 (epithelial cell adhesion molecule) single-chain Fv fragment

The epithelial glycoprotein-2 is abundantly expressed on many solid tumors and is a suitable target for antibody-based therapy. In the present study, an antiepithelial glycoprotein-2 single-chain Fv (scFv) was derived from the hybridoma MOC31 by phage display. Despite its high affinity (KD = 3.9 x 10(-9) M), however, this antibody fragment failed to significantly enrich at lung tumor xenografts in mice, mostly because of its insufficient thermal stability. To overcome this limitation, the antigen-binding residues of the MOC31 scFv fragment were grafted onto the framework of the highly stable and well-folding anti-c-erbB2 scFv 4D5. Further modification of the resulting 4D5 MOC-A, which was performed by transferring eight additional residues of the heavy chain variable domain core of the parent MOC31 antibody, produced 4D5 MOC-B, resulting in increased serum stability at 37 degrees C and also significantly improved expression behavior while retaining the antigen specificity and affinity of the parent MOC31 scFv. In mice, the scFv 4D5 MOC-B, which was radiolabeled with 99mtechnetium using a new histidine-tag specific labeling method (Waibel et al., Nature Biotechnol., 17: 897-901, 1999), showed favorable blood clearance and efficient enriches at lung tumor xenografts, with a tumor:blood ratio of 5.25 and a total dose of 1.47% injected dose per gram after 24 h. Biophysical properties such as high thermal stability are thus decisive for whether these molecules are useful in vivo, and our approach may provide a general strategy to solve this problem. This is also the first report of using a humanized anti-EGP-2 scFv in vivo for targeting solid tumors, which is a promising targeting moiety for the diagnostics and therapy of EGP-2-positive tumors in patients.

Organometallic 99mTc-aquaion labels peptide to an unprecedented high specific activity

A new peptide labeling method that uses the organometallic aquaion [99mTc(H2O)3(CO)3]+ has been developed.

METHODS

A selection of amino acids was labeled at different concentrations with the organometallic aquaion, and the labeling yield was determined by high-performance liquid chromatography. This investigation has shown histidine to be a very potent ligand, with specific activities of up to 6 TBq/micromol (160 Ci/micromol) ligand. Histidine derivatives have been coupled to neurotensin(8-13) (NT[8-13]) and have been labeled with the aquaion, resulting in high specific activities with (N(alpha)-histidinyl)acetic acid-NT(8-13) similar to those with histidine.

RESULTS

Histidine derivatives of NT(8-13) labeled using this approach fully retained their receptor affinity, showing KD values of all investigated NT analogs below 1 nmol/L on colon carcinoma HT29 cells. Biodistrbution experiments in BALB/c mice showed complete clearance of (N(alpha)-histidinyl)acetic acid-NT(8-13) from the blood after 24 h and no unwanted accumulation in any tissue.

CONCLUSION

The novel labeling method using the organometallic 99mTc-aquaion combines the advantage of highest specific activities with minimal functionalization of proteins and peptides under retention of biologic affinity.

Anti-neuroblastoma antibody chCE7 binds to an isoform of L1-CAM present in renal carcinoma cells

Immunoprecipitation after cell surface labeling of human neuroblastoma cells showed that the anti-neuroblastoma monoclonal antibody (mAb) chCE7 binds to a 200,000 M(r) cell surface protein. The protein was partially purified by immuno-affinity chromatography from a human renal carcinoma and a human neuroblastoma cell line, which both showed high levels of binding of MAb chCE7. NH(2)-terminal sequences of 18 and 15 amino acid residues were determined. Both sequences isolated from the renal carcinoma and the neuroblastoma cells showed strong homology to human cell adhesion molecule L1 (L1-CAM), and both were characterized by the NH(2)-terminal deletion of 5 amino acids, comprising exon 2 of L1-CAM. Reverse trancription-polymerase chain reaction (RT-PCR) analysis of the regions spanning exon 2 and exon 27 of L1-CAM indicated that in neuroblastoma cells both transcripts for the full-length and exon-deleted forms are present, whereas in the renal carcinoma cell lines only the exon-deleted L1-CAM isoform were detected. Western blot analysis showed that 6 of 7 tested renal carcinoma cell lines and 5 of 15 renal carcinoma tissues expressed L1-CAM. In normal adult kidney tissue, very low levels of protein expression were found. Northern blot analysis confirmed that in renal carcinoma and neuroblastoma cell lines L1-CAM mRNA levels are correlated with protein expression.

Stable one-step technetium-99m labeling of His-tagged recombinant proteins with a novel Tc(I)-carbonyl complex

We have developed a technetium labeling technology based on a new organometallic chemistry, which involves simple mixing of the novel reagent, a 99m Tc(I)-carbonyl compound, with a His-tagged recombinant protein. This method obviates the labeling of unpaired engineered cysteines, which frequently create problems in large-scale expression and storage of disulfide-containing proteins. In this study, we labeled antibody single-chain Fv fragments to high specific activities (90 mCi/mg), and the label was very stable to serum and all other challenges tested. The pharmacokinetic characteristics were indistinguishable from iodinated scFv fragments, and thus scFV fragments labeled by the new method will be suitable for biodistribution studies. This novel labeling method should be applicable not only to diagnostic imaging with 99mTc, but also to radioimmunotherapy approaches with 186/188 Re, and its use can be easily extended to almost any recombinant protein or synthetic peptide.

Differential inhibitory effect of L-lysine on renal accumulation of 67Cu-labelled F(ab')2 fragments in mice

The basic amino acid L-lysine was administered to mice in an attempt to circumvent unwanted renal accumulation of 67Cu-labelled F(ab')2 fragments derived from the anti-NCAM IgG1, SEN7 and anti-CEA IgG1 monoclonal antibody (MAb)35. In control experiments, significant renal uptake of both 67Cu-labelled F(ab')2 fragments was observed, radiolabel being primarily localised to proximal tubules in the renal cortex. Following optimised L-lysine dosing protocols, renal uptake of 67Cu-MAb35 F(ab')2 was inhibited by up to 42%. Surprisingly, little inhibition (< 10%) of 67Cu-SEN7 F(ab')2 uptake was observed. Experiments to investigate this differential inhibition indicated that inhibition of MAb35 F(ab')2 uptake was relatively short-lived (approx. 6 hr), whilst no apparent differences were found in blood clearance rates between either 67Cu-F(ab')2 fragment. L-lysine administration caused a significant diuresis with high levels of intact 67Cu-labelled SEN7 and MAb35 F(ab')2 appearing in the urine, possibly due to blockade of renal uptake and lysine-induced increases in glomerular membrane permeability. Iso-electric focusing studies failed to identify any charge differences between the 67Cu-labelled F(ab')2 fragments, although a cathodal migration of all 67Cu-labelled samples, presumably due to the net positive charge conferred by addition of 67Cu2+ ions, was observed. Our results demonstrate that in addition to net charge, other unidentified characteristics may influence renal accumulation of radiometal-labelled F(ab')2 fragments and their inhibition by L-lysine.

Isolation and characterization of rat liver microsomal R-ibuprofenoyl-CoA synthetase

Microsomal long-chain acyl-CoA synthetase (EC 6.1.2.3.) has been suggested to be involved in the stereoselective formation of the CoA thioester of ibuprofen. In this study, we demonstrated that the microsomal enzyme from rat liver responsible for palmitoyl-CoA synthesis also catalyzes the formation of R-ibuprofenoyl-CoA in a Mg(2+)- and ATP-dependent process. Long-chain acyl-CoA synthetase from rat liver microsomes was purified to homogeneity as evidenced by SDS-gel electrophoresis. Simultaneous measurements of palmitoyl-CoA and R-ibuprofenoyl-CoA formation with HPLC in various fractions and purification steps during protein isolation revealed a high correlation between both activities. The purification procedure included solubilization of the microsomes obtained from rat livers with Triton X-100 and subsequent chromatography of the 100,000 x g supernatant on blue-sepharose, hydroxyapatite, and phosphocellulose. The purified enzyme exhibited an apparent molecular weight of 72 kDa as estimated by SDS gel electrophoresis, with specific activities of 71 nmol.min-1.mg-1 protein and 901 nmol.min-1.mg-1 protein for formation of R-ibuprofenoyl-CoA and palmitoyl-CoA, respectively. Palmitoyl-CoA formation catalyzed by the purified enzyme exhibited biphasic kinetics indicative of two isoforms, a high-affinity (KM 0.13 +/- 0.11 microM), low-capacity form and a low-affinity (KM 81 +/- 11.5 microM), high-capacity form. In contrast, measurement of R-ibuprofenoyl-CoA synthesis over a concentration range from 5 to 3000 microM showed the participation of a single CoA ligase with a KM of 184 +/- 19 microM, corresponding to the low-affinity isoform of palmitoyl-CoA synthesis with a marked enantioselectivity towards the R-form of ibuprofen. R-ibuprofenoyl-CoA formation of the enzyme preparation was inhibited by palmitic acid (KI 13.5 +/- 0.5 microM) and S-ibuprofen (KI 405 +/- 10 microM). In summary, these data give strong evidence for the identity of R-ibuprofenoyl-CoA and long-chain acyl-CoA synthetase.

Pharmacokinetics of morphine and its glucuronides after intravenous infusion of morphine and morphine-6-glucuronide in healthy volunteers

Steady-state pharmacokinetics of morphine and morphine-6-glucuronide (M-6-G) after intravenous administration of either morphine or M-6-G were determined in healthy volunteers. With a dosing regimen calculated on the basis of data obtained in a first series of experiments in four subjects (morphine: intravenous loading dose of 0.24 mg/kg for 5 minutes and an intravenous infusion of 0.069 mg.kg-1.hr-1 for 4 hours; M-6-G: loading dose of 0.011 mg/kg for 5 minutes and an infusion of 0.006 mg.kg-1.hr-1 for 4 hours), it was possible to yield plasma concentrations of morphine and M-6-G in another four subjects close to predefined targeted levels (35 and 45.5 ng/ml morphine and M-6-G, respectively). This dosing regimen may be used in further pharmacodynamic studies to compare the analgesic effects of morphine and M-6-G. In addition, metabolite kinetics of M-6-G were calculated as a function of time with use of a linear systems approach to the estimation of rate and fraction of morphine glucuronidation to M-6-G.

Association of CD24 with the kinase c-fgr in a small cell lung cancer cell line and with the kinase lyn in an erythroleukemia cell line

Human CD24 is a highly glycosylated glycosylphosphatidylinositol-linked (GPI-linked) cell surface protein. GPI-linked proteins are involved in signal transduction mediated by members of the protein tyrosine kinase (PTK) family. Therefore we studied associated molecules providing the signaling capacity of CD24. Lysates of SW2 and K562 cells were analysed for expression of PTK of the c-src family by Western blotting. We identified c-fgr in SW2 lysates and c-fgr and also lyn in K562 lysates. To study a putative association of these PTK with CD24 we performed immunoprecipitations with the mAb SWA11 directed against CD24. Western analysis of the precipitates showed an association of c-fgr with CD24 in SW2 cells and lyn in K562 cells. We conclude that either c-fgr or lyn is physically associated with CD24 in a cell-type depending manner. An involvement of these complexes in signaling phenomenons of CD24 in small cell lung cancer and in leukaemias is discussed.

Radiation studies on B cell differentiation marker CD24/SCLC Cluster-4 antigen expressing and non-expressing lung cancer cell lines and mouse fibroblasts

A correlation between CD24 expression and higher intrinsic radiation sensitivity has been described in B-lineage acute lymphoblastic leukaemia (B-ALL). We recently identified the SCLC surface antigen Cluster-4 (CL-4) to be identical to the B cell differentiation marker CD24, except for one amino acid residue. The CD24/CL-4 antigen is highly expressed on SCLC, but rarely on NSCLC cells. In order to investigate the influence of the expression of CD24/CL-4 on the radiation sensitivity in a non-leukaemic cell system, sublines of the human SCLC H249 cell line transfected with mutated ras oncogene, and differing in their CD24/CL-4 expression, were studied. In addition, we stably transfected the NSCLC A125 cell line and the mouse fibroblast NIH3T3 cell line with the CL-4 cDNA. The differential expression of CD24/CL-4 on the cells had no influence on morphology, proliferation and cloning efficiency. Radiation studies were done with cells in exponential growth phase. In the highly resistant NSCLC A125 cells no difference in radioresponsiveness was observed between CD24/CL-4 expressing and non-expressing cells. In the rather radiosensitive cells, similar responses to radiation were observed between CD24/CL-4 expressing and non-expressing SCLC H249-ras cells, whereas the CL-4 transfected NIH3T3 mouse fibroblasts showed a substantially higher radioresistance than the CD24/CL-4 non-expressing control cells. In conclusion, the correlation between CD24/CL-4 expression and radiation sensitivity is controversial and depends on the cell type.