Development and characterization of HAT-sensitive Ewing tumour cells for immunotherapy

BACKGROUND

Despite improvements in the treatment of patients with Ewing family tumours (EFT) during the past decades, the prognosis for patients with advanced disease is still unsatisfying. New treatment strategies have to be developed.

MATERIALS AND METHODS

A hypoxanthine/aminopterin/thymidine (HAT)-sensitive EFT cell line was developed by repetitive treatment of the EFT cell line SK-N-MC with 8'-azaguanine (8AG). By using DNA microarrays, the gene expression profile of this cell line was characterized. Immunostimulatory activity was assessed by mixed lymphocyte/tumour cell culture (MLTC). Artificial fusion of tumour cells and dendritic cells was visualized by flow cytometry.

RESULTS

After selection of 8AG-resistant cells, a cell line with high sensitivity for treatment with HAT was obtained. Expression of the X chromosome inactivation specific transcript XIST was higher in HAT-sensitive cells. Nevertheless, HAT-sensitive cells retained the EFT-associated gene expression profile. Moreover, in the presence of HAT, it was possible to use these cells without irradiation as stimulatory cells in MLTC or as fusion partner for dendritic cells.

CONCLUSION

HAT-sensitive EFT cells might be an interesting tool for the development of new immunotherapeutic approaches for the treatment of EFT.

Influence of methylenetetrahydrofolate reductase polymorphisms on efficacy and toxicity of methotrexate in patients with juvenile idiopathic arthritis

OBJECTIVE

To study the relationship of C677T and A1298C polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene to toxicity and efficacy of methotrexate (MTX) in patients with juvenile idiopathic arthritis (JIA).

METHODS

Single nucleotide polymorphisms of the MTHFR gene were investigated by polymerase chain reaction and restriction enzyme analysis of DNA extracted from peripheral blood cells. The fasting plasma homocysteine concentration was analyzed by enzyme immunoassay. Clinical data of 58 patients with JIA treated with MTX were analyzed retrospectively.

RESULTS

The 1298A/A genotype was present in 31 patients, 1298C/C in 4 patients, and 21 patients were heterozygous. The 677C/C genotype was present in 29 patients, 677 T/T in 3 patients, and 26 patients were heterozygous. In patients who presented the C allele of the A1298C polymorphism, improvement with respect to the number of swollen joints, the number of tender joints, and a decrease in erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels occurred more frequently than in 1298 A/A homozygous patients (p < 0.05 for ESR, p < 0.01 for CRP, chi-square test). There was no relationship between the C677T polymorphism and the efficacy of MTX treatment. Forty-two adverse events were noted in 26 patients; gastrointestinal symptoms were most common (n = 20), followed by elevated serum levels of transaminases (n = 19) and hair loss (n = 3). There was no cytopenia. Patients with the heterozygous genotype 677C/T exhibited adverse events more frequently than patients with the homozygous C/C genotype (65% vs 31%; p < 0.05, chi-square test). The A1298C polymorphism, however, was not associated with occurrence of adverse events. Plasma homocysteine was elevated in 6 patients with up to 16.9 mmol/l. No association was found to a specific genotype or to adverse events.

CONCLUSION

These preliminary data suggest an association of the MTHFR 677C/C polymorphism to a higher tolerability of MTX, and of the 1298A/A to lower clinical efficacy of MTX therapy in JIA.

Hyperhomocysteinemia: marker of systemic atherosclerosis in peripheral arterial disease

AIM

Patients suffering from peripheral arterial disease (PAD) are increasingly described as having hyperhomocysteinemia more than in patients with coronary artery or cerebrovascular disease. Cases of symptomatic PAD usually present with associated coronary artery or cerebrovascular disease and renal artery disease. It can thus be postulated that multilocular atherosclerosis is linked to hyperhomocysteinemia and that the extent of atherosclerosis has a possible correlation with homocysteine concentrations. The aim of this study was to ascertain whether fasting total homocysteine concentrations in patients with PAD are associated with the extent and the localization of systemic atherosclerosis in cerebrovascular, coronary and/or renal vascular zones.

METHODS

A total of 183 patients with PAD, Fontaine stages II-IV, were divided into 2 groups: Group A contained patients with isolated PAD (n=98) and Group B patients with systemic atherosclerosis in PAD (n=85). Characterization of vascular disease in various vascular zones was indication-adapted using non-invasive and/or invasive

METHODS

Patients with renal insufficiency were excluded from the study.

RESULTS

Homocysteine concentrations were significantly lower in patients with isolated PAD than in patients with additional systemic atherosclerosis (10.1+/-4.4 vs 16.7+/-7.04 micromol/l, p<0.0001). There were no differences in localization or extent of concomitant systemic atherosclerosis. Logistic regression analysis indicated that elevated plasma homocysteine and decreasing ABPI served independently as significant risk indicators for systemic atherosclerosis in patients with PAD (p<0.0001).

CONCLUSION

Hyperhomocysteinemia is a precursoral marker of systemic atherosclerosis and thus a prognostic indicator of cardiovascular morbidity and mortality in PAD.

Nuclear lamins: their structure, assembly, and interactions

Nuclear lamins are intermediate filament-type proteins that are the major building blocks of the nuclear lamina, a fibrous proteinaceous meshwork underlying the inner nuclear membrane. Lamins can also be localized in the nuclear interior, in a diffuse or spotted pattern. Nuclei assembled in vitro in the absence of lamins are fragile, indicating that lamins mechanically stabilize the cell nucleus. Available evidence also indicates a role for lamins in DNA replication, chromatin organization, spatial arrangement of nuclear pore complexes, nuclear growth, and anchorage of nuclear envelope proteins. In this review we summarize the current state of knowledge on the structure, assembly, and possible functional roles of nuclear lamins, emphasizing the information concerning the ability of nuclear lamins to self-assemble into distinct oligomers and polymers.

The preprotein translocation channel of the outer membrane of mitochondria

The preprotein translocase of the outer membrane of mitochondria (TOM complex) facilitates the recognition, insertion, and translocation of nuclear-encoded mitochondrial preproteins. We have purified the TOM complex from Neurospora crassa and analyzed its composition and functional properties. The TOM complex contains a cation-selective high-conductance channel. Upon reconstitution into liposomes, it mediates integration of proteins into and translocation across the lipid bilayer. TOM complex particles have a diameter of about 138 A, as revealed by electron microscopy and image analysis; they contain two or three centers of stain-filled openings, which we interpret as pores with an apparent diameter of about 20 A. We conclude that the structure reported here represents the protein-conducting channel of the mitochondrial outer membrane.

Making heads and tails of intermediate filament assembly, dynamics and networks

Thus far, intermediate filaments (IFs) have been the least understood of the three cytoskeletal filament systems with regard to their structure, assembly, network formation, and dynamics. This picture is now slowly but definitely changing, as recent in vivo and in vitro experiments, including generation of transgenic animals, have yielded important new data shedding light on the following areas: the molecular architecture of IFs; the role of the highly variable end domains during IF assembly and network formation; the factors that govern whether IF proteins are involved in de novo filament formation or are incorporated into a pre-existing IF network; and the effects of post-translational modifications, such as phosphorylation and glycosylation of IF polypeptides, on filament assembly, dynamics and turnover.

The rod domain of NF-L determines neurofilament architecture, whereas the end domains specify filament assembly and network formation

Neurofilaments, assembled from NF-L, NF-M, and NF-H subunits, are the most abundant structural elements in myelinated axons. Although all three subunits contain a central, alpha-helical rod domain thought to mediate filament assembly, only NF-L self-assembles into 10-nm filaments in vitro. To explore the roles of the central rod, the NH2-terminal head and the COOH-terminal tail domain in filament assembly, full-length, headless, tailless, and rod only fragments of mouse NF-L were expressed in bacteria, purified, and their structure and assembly properties examined by conventional and scanning transmission electron microscopy (TEM and STEM). These experiments revealed that in vitro assembly of NF-L into bona fide 10-nm filaments requires both end domains: whereas the NH2-terminal head domain promotes lateral association of protofilaments into protofibrils and ultimately 10-nm filaments, the COOH-terminal tail domain controls lateral assembly of protofilaments so that it terminates at the 10-nm filament level. Hence, the two end domains of NF-L have antagonistic effects on the lateral association of protofilaments into higher-order structures, with the effect of the COOH-terminal tail domain being dominant over that of the NH2-terminal head domain. Consideration of the 21-nm axial beading commonly observed with 10-nm filaments, the approximate 21-nm axial periodicity measured on paracrystals, and recent cross-linking data combine to support a molecular model for intermediate filament architecture in which the 44-46-nm long dimer rods overlap by 1-3-nm head-to-tail, whereas laterally they align antiparallel both unstaggered and approximately half-staggered.

Effect of MAP2, MAP2c, and tau on kinesin-dependent microtubule motility

By making use of DIC video microscopy to monitor microtubule motility we have studied the effect of several MAPs (MAP2, MAP2c, tau) on microtubule-kinesin interactions and microtubule gliding. Of the three MAPs tested, MAP2 interferes most strongly with kinesin-dependent microtubule motility.

Aluminum fluoride, microtubule stability, and kinesin rigor

Aluminum fluoride may be used both to stabilize microtubules and to induce strong binding of kinesin, thus circumventing the need for taxol and AMP-PNP in kinesin preparations.