Expression of human beta-interferon in Namalwa KJM-1 which was adapted to serum-free medium.

A Namalwa cell line, KJM-1, which was adapted to serum-free medium is thought to be a very useful host cell line for recombinant DNA technology. Thus, the utility of Namalwa KJM-1 for expression of foreign genes was examined. As a model system human beta-interferon (beta-IFN) gene was engineered for expression in this cell line. For construction of the beta-IFN expression vector pSE1 beta 1-4, the expression vector pAGE107 was constructed and used. It contains simian virus 40 (SV40) early promoter, the rabbit beta-globin RNA processing signals for splicing and polyadenylation, and SV40 early RNA processing signal for polyadenylation. In addition to the above transcription unit, pAGE107 contains the ampicillin-resistance gene and G418-resistance gene. They can confer ampicillin resistance to Escherichia coli (E. coli) and G418 resistance to animal cells. To introduce plasmid DNA into cells, electroporation is a useful method (Wong, 1982; Potter, 1984). We have established conditions for DNA-mediated transfection of Namalwa KJM-1 cell line by electroporation. Among pSE1 beta 1-4-introduced cells, clone 1-3 was further examined for the expression of beta-IFN in serum-free medium. The production level of beta-IFN was elevated with the increase of the cell density. The results indicated that the Namalwa KJM-1 cell line is useful for production of foreign gene products.