Fibrotic response in fibroblasts from congenital disorders of glycosylation

Congenital disorders of glycosylation (CDG) are characterized by a generalized underglycosylation of proteins. CDG is associated with multiple symptoms such as psychomotor retardation, hypotonia, hormonal disturbances, liver fibrosis and coagulopathies. The molecular basis of these symptoms is poorly understood considering the large extent of affected glycoproteins. To better understand the cellular responses to protein underglycosylation in CDG, we have investigated the differences in gene expression between healthy control and CDG fibroblasts by transcriptome comparison. This analysis revealed a strong induction of several genes encoding components of the extracellular matrix, such as collagens, COMP, IGFBP5 and biglycan. The extent of this response was confirmed at the protein level by showing increased production of collagen type-I for example. This fibrotic response of CDG fibroblasts was not paralleled by a differentiation to myofibroblasts and by increased TGF-β signalling. We could show that the addition of recombinant IGFBP5, one of the induced proteins in CDG, to healthy control fibroblasts increased the production of collagen type-I to levels similar to those found in CDG fibroblasts. The fibrotic response identified in CDG fibroblasts may account for the elevated tissue fibrosis, which is often encountered in CDG patients.

The PAX5 oncogene is expressed in N-type neuroblastoma cells and increases tumorigenicity of a S-type cell line

Neuroblastoma is a neural crest-derived neoplasm of infancy with poor outcome in patients with advanced disease. The oncogenic transcription factor PAX5 is an important developmental regulator and is implicated in the pathogenesis of several malignancies. Screening of neuroblastoma cell lines revealed PAX5 expression in a malignant subset of neuroblastoma cells, so-called 'N-type' cells, but not in the more benign 'S-type' neuroblastoma cells. PAX5 expression was also detected in small cell lung cancer, an aggressive tumor of neural crest origin. Based on this observation we hypothesized that there could be a relationship between PAX5 expression and the more malignant phenotype of N-type cells. Stable PAX5 expression was established in several clones of the S-type cell line CA-2E. A noticeable difference in morphology of these transfectants was observed and there was also a significant increase in the proliferation rate. Moreover, PAX5 expressing clones gained the ability to form colonies in a soft agar assay, a marker of tumorigenicity. Down-regulation of PAX5 in several N-type cell lines and one small cell lung cancer cell line utilizing small interfering RNA resulted in a significant decrease in growth rate. Taken together we propose PAX5 as an important factor for the maintenance of the proliferative and tumorigenic phenotype of neuroblastoma. Our data, together with a recent study on the role of PAX genes in cancer suggest that PAX5 and other PAX transcription factors might be valuable targets for cancer therapy.

Implications for space radiation environment models from CREAM & CREDO measurements over half a solar cycle

Flight data obtained between 1990 and 1997 from the Cosmic Radiation Environment Monitors CREAM & CREDO carried on UoSAT-3, Space Shuttle, STRV-1a (Space Technology Research Vehicle) and APEX (Advanced Photovoltaic and Electronics Experiment Spacecraft) provide coverage over half a solar cycle. The modulation of cosmic rays and evolution of the South Atlantic Anomaly are observed, the former comprising a factor of three increase at high latitudes and the latter a general increase accompanied by a north-westward drift. Comparison of particle fluxes and linear energy transfer (LET) spectra is made with improved environment & radiation transport calculations which account for shield distributions and secondary particles. While there is an encouraging convergence between predictions and observations, significant improvements are still required, particularly in the treatment of locally produced secondary particles. Solar-particle events during this time period have LET spectra significantly below the October 1989 event which has been proposed as a worst case model.