Amplification of the dihydrofolate reductase gene (Dhfr) by methotrexate (Mtx) exposure is commonly used for recombinant protein expression in Chinese hamster ovary (CHO) cells. However, this method is both time- and labor-intensive, and the high-producing cells that are generated are frequently unstable in culture. Another gene amplification method is based on using a plasmid bearing a mammali...

Background Cell line development (CLD) is a critical step in the generation of biotherapeutics, but it is still hindered by several pain points, including the lengthy and laborintensive workflow needed to isolate desirable clones, lack of reproducibility, as well as potential protein quality issues. Over the last decade, antibody titers in mammalian cell culture systems in excess of 3 g/L have ...

Plasmids with both a mammalian replication initiation region (IR) and a matrix attachment region (MAR) are spontaneously amplified in transfected cells, and generate extrachromosomal double minute (DM) or chromosomal homogeneously staining region (HSR). We previously isolated the shortest core IR (G5) required for gene amplification. In this study, we ligated the G5 DNA to create direct or inve...

Four versions of tricistronic vectors expressing IgG1 light chain (LC), IgG1 heavy chain (HC), and dihydrofolate reductase (DHFR) in one transcript were designed to compare internal ribosome entry site (IRES) and furin-2A (F2A) for their influence on monoclonal antibody (mAb) expression level and quality in CHO DG44 cells. LC and HC genes are arranged as either the first or the second cistron. ...

Cell culture feeds optimization is a critical step in process development of pharmaceutical recombinant protein production. Amino acids are the basic supplements of mammalian cell culture feeds with known effect on their growth promotion and productivity. In this study, we reported the implementation of the Plackett-Burman (PB) multifactorial design to screen the effects of amino acids on the g...

We previously found that plasmids bearing a mammalian replication initiation region (IR) and a nuclear matrix attachment region (MAR) efficiently initiate gene amplification and spontaneously increase their copy numbers in animal cells. In this study, this novel method was applied to the establishment of cells with high recombinant antibody production. The level of recombinant antibody expressi...

Production of recombinant antibodies against botulinum neurotoxin is necessary for the development of a post-exposure treatment. CHO-DG44 cells were transfected with a plasmid encoding the light and heavy chains of a chimeric monoclonal antibody (S25) against botulism neurotoxin serotype A. Stable cell lines were obtained by dilution cloning and clones were shown to produce nearly equivalent le...

Amplification of DHFR gene in CHO cells by selection of MTx has been widely applied to the establishment of stable cell lines that efficiently produce recombinant protein pharmaceuticals. However, the DHFR/MTx technology was highly time-and labor-consuming. On the other hand, we had found that a plasmid bearing a mammalian replication initiation region (IR) and a matrix attachment region (MAR) ...

Conclusions and Perspectives 2 Summary 3 Summary Recombinant proteins are gaining in importance for therapeutic applications. The proteins are expressed in stable cell lines, within which recombinant DNA has incorporated into the host cells genome. Identification and isolation of extremely high producers from transfected cell populations is a tedious and time-consuming effort. We proposed two d...