Role of thymoma-derived growth factor (MGFF) in growth control of the thymus

点击翻译按钮获取中文摘要

Rats of the BUF/Mna strain develop spontaneous large benign thymomas in two years. The high incidence of the tumor is regulated mainly by a single susceptible gene (Tsr-1) and is inherited dominantly. An intrinsic thymic epithelial abnormality is responsible for the development of the thymomas. Mice and rats mutated at the nude locus show defects in normal hair growth and thymic dysgenesis.A factor which stimulated the growth and cell fusion of thymic macrophages was produced by a rat thymoma epithelial cell line, TaD-1-3, and designated as MGFF.MGFF was purified from the conditioned medium of TaD-1-3 with DEAE column chromatography, Sephacryl S-200 gel filtration column chromatography, RCA-agarose lectin column chromatography and SDS-PAGE.Native MGFF was suggested to be a glycoprotein of a molecular weight of 100 kdalton, having disulfide-bonds. The biological activity was resistant to trypsin, RNase, DNase and various glycolytic enzymes and distinguished from recombinant G-CSF,M-CSF and GM-CSF.These results suggest that MGFF is a novel factor contributing to the development of the thymoma in a thymoma-prone rat strain, BUF/Mna.Clonal epithelial cell lines from thymuses of BUF/Mna-rnu/+ and BUF/Mna-rnu /rnu rats were established in a medium containing 1 mM dexamethasone (Dex), and were examined for growth characteristics and expression of intermediate filaments. The established cell line from BUF/Mna-rnu/+ (B(nu/+) -5-4) showed a polygonal shape and a high expression of keratin peptides similar to the other cell lines. However, the cells from a nude rat thymic rudiment (B(nu/nu) -1-3) were flatter and showed a lower saturation density than those from the ohter cell lines. Expression of intermediate filaments was much different from other cell lines. These cell lines may be useful in investigating the defects of thymic epithelial cells of nude rats, the function of whn gene and the involvement of the rnu (whn) gene on thymomagenesis in BUF/Mna rats.