Efficient expression of human beta-interferon in Namalwa KJM-1 cells adapted to serum-free medium by a dhfr gene coamplification method

✍ Scribed by Hiromasa Miyaji; Nahoko Harada; Tamio Mizukami; Seiji Sato; Nobuo Fujiyoshi; Seiga Itoh

• Publisher: Springer
• Year: 1990
• Tongue: English
• Weight: 563 KB
• Volume: 4
• Category: Article
• ISSN: 0920-9069
• DOI: 10.1007/bf00365098

✦ Synopsis

We previously reported the expression of human beta-interferon (B-IFN) (Miyaji et al., 1989) and human lymphotoxin (Miyaji et al., 1990) in Namalwa KJM-1 cells adapted to serum-free medium. To establish an efficient gene expression system, a dihydrofolate reductase (dhfr) gene coamplification method was applied to this cell line. A B-IFN expression plasmid was introduced with a dhfr expression plasmid into KJM-1 and methotrexate (MTX)-resistant derivatives were selected by a stepwise increase of MTX concentration. Among them, derivatives which showed higher expression levels of B-IFN than that achieved by the parental transformants were obtained, suggesting that a dhfr gene coamplification method can be used for efficient expression of foreign genes in KJM-1 which contains endogenous dhfr genes. Then, an improved B-IFN expression vector was constructed, which contains a dhfr transcription unit. This plasmid was introduced into KJM-1 and then, MTX-resistant derivatives were selected. Among them, the highest producer, clone 40-10-24, secreted B-IFN at a level as high as 5 ktg/ml, which is about 100-fold higher than that obtained by the G418-resistant parental transformants. In addition, B-IFN produced by recombinant KJM-1 cells had the same molecular weight of that produced by fibroblasts.