title: Generation of recombinant CHO(dhfr-) cell lines by single selection for dhfr+ transformants.
abstract: In order to establish a mammalian cell expression system with a minimum of selection steps and a stable expression of microgram amounts of recombinant protein (human tissue-type plasminogen activator mutants and chimeric proteins) per 10(6) cells per day, we investigated Chinese hamster ovary cells and the dihydrofolate reductase-deficient Chinese hamster ovary cell line CHO(dhfr-). The 1tPA expression vector pCMVtPA was cotransfected either with the SV40 enhancer sequence containing dhfr expression vector pMT2 or with the enhancerless dhfr expression vector pAdD26SV(A) into CHO(dhfr-) cells. With both dhfr expression plasmids, selection for dhfr+ transformants followed by single dilution cloning was sufficient to generate cell lines with a production level of up to 4.6 micrograms tPA/10(6) cells.day. This approach is useful if gene amplification procedures are time-consuming and impracticable because of a large number of recombinant proteins. In order to establish CHO cell lines with a tPA expression level as high as that in the case of CHO(dhfr-) cells, repeated dilution cloning is necessary.
authors.affiliation: Central Institute of Molecular Biology, Berlin-Buch, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Wernicke
authors.forename: H
authors.initials: H
authors.lastname: Will
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D007700:Kinetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000235:genetics; D014170:Transformation, Genetic
chemical_list: D011994:Recombinant Proteins; D013762:Tetrahydrofolate Dehydrogenase; D010959:Tissue Plasminogen Activator