• Journal of Microbiology and Biotechnology
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• v.17 no.6
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• pp.1036-1040
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• 2007

Sodium butyrate (NaBu) has been used to enhance protein expression levels in mammalian cell culture. To determine the clonal variability of recombinant Chinese hamster ovary (rCHO) cells in response to NaBu addition regarding specific antibody productivity $(q_{Ab})$, three rCHO clones were subjected to different concentrations of NaBu. For all three clones, NaBu addition inhibited cell growth and decreased cell viability in a dose-dependent manner. On the other hand, the enhancing effect of NaBu on $q_{Ab}$ varied significantly among the clones. NaBu addition enhanced the antibody production of only one clone. RT-PCR analysis revealed that the changes in $q_{Ab}$ correlated linearly with those of the mRNA transcription level. Thus, it was concluded that the different enhancing effects of NaBu on protein expression in rCHO cell clones resulted from their different mRNA transcription levels.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.231.2-231.2
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• 2003

The efficient EPO (Erythropoietin) expression system in Chinese Hamster Ovary (CHO) cells was devised through the removal of ammonium ion accumulated in the media by introducing urea cycle enzymes. Previously, we developed C05 cell by transfecting the carbamoly phosphate synthase (CPS) and ornithine transcarbamoylase (OTC) into the EPO expressing CHO cell, IBE. (omitted)

• Journal of Microbiology
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• v.38 no.4
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• pp.270-274
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• 2000

Pathogenic Salmonella typhimurium can invade the intestinal epithelium and cause a wide range of diseases including gastroenteritis and bacteremia in human and animals. To identify the genes involved in the infection, the invasion determinant was obtained from S. typhimurium 82/6915 and was subcloned into pGEM-7Z. A subclone DHl (pSV6235) invaded HEp-2 and Chinese hamster ovary epithelial cells and contained a 4.4 kb fragment of S. typhimurium genomic region. Compared with the host strain E. coli DHl, the subclone DHl (pSV6235) invaded cultured HEp-2 and Chinese hamster ovary cells at least 75- and 68-fold higher, respectively. The invasion rate of E. coli DHl for the cells significantly increased by harbouring the genomic region derived from pathogenic S. typhimurium 82/6915.

• KSBB Journal
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• v.28 no.2
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• pp.86-91
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• 2013

To date, various strategies have been studied to increase specific productivity in Chinese hamster ovary (CHO) cell cultures. Also, albumin-fusion platform is being applied to other important bioactive peptides with short half-lives. Here, we investigated the effects of silkworm gland hydrolysate (SGH) on the production of albumin-erythropoietin (Alb-EPO) in transgenic CHO cells. The viable cell density of CHO cells was increased by 13% in the medium containing 1 mg/mL SGH higher than in the control medium without SGH. In addition, the production of Alb-EPO was also 1.26- fold enhanced by reducing the early apoptosis of CHO cells. In conclusion, SGH could be used as a useful supplement for the enhancement of recombinant protein production.

• Journal of Microbiology and Biotechnology
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• v.14 no.4
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• pp.810-815
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• 2004

Many biological properties and the clinical potential of human interleukin-2 (hIL-2) draw much attention to its high-level expression in mammalian cells. Recombinant human IL-2 (rhIL-2) was expressed in Chinese hamster ovary (CHO) cells, using the recently developed expression system which confers position-independent expression. Stable CHO cell lines carrying several hundred amplified copies of the rhIL-2 gene were easily obtained and rhIL-2 was expressed at high levels after selection with increasing concentrations of methotrexate. Interestingly, the insertion of the transcription terminator of the human gastrin gene into the downstream region of the gene for rhIL-2 considerably increased rhIL-2 expression. Using the expression system with the transcription terminator, it was possible to get a CHO cell line expressing the rhIL-2 at a very high level, about $11.4\mug/10^6$ cell/day, which is about 6 times higher than that previously reported. The biological activity of the rhIL-2 protein purified from the cell line was also confirmed by the cell proliferation assay.

• Preventive Nutrition and Food Science
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• v.8 no.1
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• pp.36-39
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• 2003

Many defined cell culture media were formulated over 3() years ago and may be deficient in certain micronutrients whose essentiality has only subsequently been recognised. The objective of this study was to evaluate whether alpha-minimal essential medium (MEM) supplemented with 10% foetal bovine serum contained sufficient selenium for optimal activity of the selenium containing enzymes cytosolic glutathione peroxidase (cGPx) and phospholipid hydroperoxide glutathione peroxidase (PHGPx) in cultured Chinese hamster ovary (CHO) cells. Additionally, the effect of zinc deficiency and metallothionein (MT) overexpression on cGPx and PHGPx activity was studied. The addition of 100 nM of selenous acid to the culture medium increased cGPx expression by 10-fold and PHGPx by about 2-fold in both wild-type CHO-K1 cells and CHO-K1 cells overexpressing mouse MT-1. Zinc deficiency had no significant effect on enzyme activity, but cells overexpressing mouse MT-1 had higher levels of cGPx activity. Zinc deficiency decreased cell survival but overexpression of MT-1 was partially protective, probably because its presence in quantity favoured the uptake, sequestration and cellular retention of any remaining zinc. This study demonstrates that selenium in complete alpha-MEM is insufficient for optimal cGPx and PHGPx activity and may compromise the cellular response to oxidative stress.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1397-1401
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• 2005

Bone morphogenetic protein-4 (BMP-4) is a signaling homodimeric molecule that acts as a morphogen to influence cell fate in a concentration-dependent manner. The limited supply of a pure preparation of BMP-4, due to very low level of their expression in vivo, makes it difficult not only to study the biological activities of BMPs, but also to use them as a clinical tool. For a large-scale production of BMP-4, human BMP-4 cDNA was expressed in Chinese hamster ovary (CHO) cells by a recently development vector system, which confers position-independent stable expression of the foreign genes. The CHO cell line expressing recombinant human BMP-4 (rhBMP-4) at the level of $7\;{\mu}g/ml$ could be obtained after stepwise selection with methotrexate. This level of expression is about 70 times higher than those previously reported. The partially processed form of BMP-4 as well as mature form could be detected, when the aliquots of culture media were analyzed by Western blot. The glycosylation pattern and biological activity of the rhBMP-4 were determined by glycosidase treatment and the induction rate of alkaline phosphatase in mouse osteoblastic cells.

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2002.11a
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• pp.100-100
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• 2002

As an preliminary experiment for making transgenic animals producing human follicle stimulating hormone (hFSH), we tried to express recombinant hFSH gene in vitro. hFSH is a heterodimeric glycoprotein hormone produced in the anterior pituitary gland. The hormone is essential in the regulation of reproductive processes, such as follicular development and ovulation. Genes encoding the common gonadotrophin alpha subunit and FSH-specific beta subunit were inserted into retroviral vectors under the control of the rat beta actin promoter. Gene transfer to the Chinese hamster ovary (CHO) cells was done by infection of the retroviruses harvested from PT67 packaging cells transfected with recombinant retrovirus vector DNA. After selection with G4l8, PCR and RT-PCR analyses of the G4l8-resistant CHO cells showed successful transfer and expression of both ${\alpha}$ and ${\beta}$ fragments of the FSH gene.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.153-158
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• 2003

The genome-wide program of gene expression during the cell division cycle response to serum free media in chinese hamster ovary(CHO) cells was characterized using cDNA microarrays. Many transcripts of genes showed variation during the cell cycle. Characterization is critical step toward understanding the basic cell cycle processes and serum-free media role in CHO cells

• YAKHAK HOEJI
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• v.45 no.6
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• pp.708-714
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• 2001

Many studies have provided evidences that hepatitis B surface antigen (HBsAg) including preS region could be an ideal candidate for a new hepatitis B virus (HBV) vaccine with higher efficacy. We established CHO cell lines, IY-CHO-2 and IY-CHO-11 expressing high levels of HBsAg containing preS2 and S protein by stable transfection method. These cell lines expressed the correct size (about 1 kb in length) of HBsAg mRNA as expected. The purified protein from the culture supernatants of the clones showed the same sizes as those expressed in native hepatitis B virus (24 kDa, 27 kDa, 34 kDa and 36 kDa). Antibody productivity of CHO-derived HBsAg protein at lower dose challenge was higher than the protein containing S region alone expressed in yeast system. These results indicate that CHO-derived HBsAg protein containing preS2 and S region can be effectively used for a better immune response as a HBV vaccine.