• KSBB Journal
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• 제30권1호
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• pp.44-51
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• 2015

Chinese hamster ovary (CHO) cells are the most widely used mammalian host for the commercial production of recombinant proteins. However, they show relatively low yields of recombinant proteins in comparison with microbial cells. Various strategies have been tried to overcome this drawback. The acetyl moieties are attached to the N-terminus of histone by histone acetyltransferase (HAT) while histone deacetylase (HDAC) removes histone-bound acetyl groups. HDAC inhibitor (HDACi), such as sodium butyrate, sodium propionate and valproic acid, can enhance specific productivity of CHO cells. Human albumin-erythropoietin (Alb-EPO) is a novel 105 kDa protein comprising recombinant human EPO fused to human albumin. In this study, we examined the effects of HDACi on the production of Alb-EPO in CHO cells with various concentrations in the range of 0-1 mM. The results showed that sodium butyrate was found to be the best HDACi for enhancing productivity. It enhanced not only the production of Alb-EPO but also the apoptosis of recombinant CHO cells.

• Journal of Microbiology and Biotechnology
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• 제29권1호
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• pp.55-58
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• 2019

Development of stable rCHO cell lines is still time consuming and labor intensive, although it is a critical step in the commercial development of recombinant antibodies. The current work demonstrates, for the first time, that electroporation of CHO cells with DMSO can enhance stable expression of recombinant antibodies in rCHO cells. Electroporation with DMSO resulted in an average 3.7-fold and 2.8-fold increases in expression levels of aflibercept and pembrolizumab, respectively, in pools of stable rCHO cells. It also resulted in an average of 2.2-fold and 2.6-fold increases in the expression of aflibercept and pembrolizumab, respectively, in single-cell derived rCHO clones. Simple batch cultures of rCHO cell clones with the highest expression produced 1.0 g/l for aflibercept and 1.4 g/l for pembrolizumab without a time-consuming gene amplification process. Electroporation with DMSO also shortened the development of rCHO cell lines to 2-3 months, allowing rapid establishment of stable rCHO cell lines with a desirable expression level antibodies.

• Journal of Microbiology and Biotechnology
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• 제23권8호
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• pp.1116-1122
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• 2013

Cell line development is the most critical and also the most time-consuming step in the production of recombinant therapeutic proteins. In this regard, a variety of vector and cell engineering strategies have been developed for generating high-producing mammalian cells; however, the cell line engineering approach seems to show various results on different recombinant protein producer cells. In order to improve the secretory capacity of a recombinant tissue plasminogen activator (t-PA)-producing Chinese hamster ovary (CHO) cell line, we developed cell line engineering approaches based on the ceramide transfer protein (CERT) and X-box binding protein 1 (XBP1) genes. For this purpose, CERT S132A, a mutant form of CERT that is resistant to phosphorylation, and XBP1s were overexpressed in a recombinant t-PA-producing CHO cell line. Overexpression of CERT S132A increased the specific productivity of t-PA-producing CHO cells up to 35%. In contrast, the heterologous expression of XBP1s did not affect the t-PA expression rate. Our results suggest that CERT-S132A-based secretion engineering could be an effective strategy for enhancing recombinant t-PA production in CHO cells.

• Journal of Microbiology and Biotechnology
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• 제16권5호
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• pp.695-703
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• 2006

The dissolved oxygen level of any cell culture environment has a critical effect on cellular metabolism. Specifically, hypoxia condition decreases cell viability and recombinant protein productivity. In this work, to develop CHO cells producing recombinant protein with high productivity, mammalian expression vectors containing a human tissue-type plasminogen activator (t-PA) gene with hypoxia response element (HRE) were constructed and stably transfected into CHO cells. CHO/2HRE-t-PA cells produced 2-folds higher recombinant t-PA production than CHO/t-PA cells in a $Ba^{2+}-alginate$ immobilized culture, and 16.8-folds in a repeated batch culture. In a non-aerated batch culture of suspension-adapted cells, t-PA productivity of CHO/2HRE/t-PA cells was 4.2-folds higher than that of CHO/t-PA cells. Our results indicate that HRE is a useful tool for the enhancement of protein productivity in mammalian cell cultures.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2002년도 생물공학의 동향 (X)
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• pp.257-260
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• 2002

Dissolved oxygen level of cell culture media has a critical effect on cellular metabolism, which governs specific productivity of recombinant proteins and mammalian cell growth However, in the cores of cell aggregates or cell-immobilized beads, oxygen level frequently goes below a critical level. Mammalian cells have a number of genes induced in the lower level of oxygen, and the genes contain a common cis-acting element (-RCGTG-), hypoxia response element (HRE). By binding of hypoxia inducible factor-l (HIF-I) to the HRE, promoters of hypoxia inducible genes are activated, which is a survival mechanism. In this work, to develop a CHO cell capable of producing recombinant proteins in immobilization and high density cell culture efficiently, mammalian expression vectors containing human tissue-type plasminogen activator (t-PA) gene controlled by HRE were constructed and stably transfected into the CHO cells. In $Ba^{2+}$ -alginate immobilization culture, CHO/pCl/dhfr/2HRE-t-PA cells produced 2 folds higher recombinant t-PA activity than CHO/pCl/dhfrlt-PA cells without $CoCl_2$ treatment. Furthermore, in repeated fed batch culture, productivity of t-PA in immobilized CHO/pCI/dhfr/2HRE-t-PA cells was 121 ng/ml/day, total production of 0.968 mg/day at 11 days culture while CHO/pCIIdhfrlt-PA cells was 22.8 ng/ml/day. All these results indicate that HRE is very useful for the enhancement of protein productivity in mammalian cell cultures.

• Journal of Microbiology and Biotechnology
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• 제18권12호
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• pp.1945-1952
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• 2008

Sialylation, the attachment of sialic acid residues to a protein, can affect the biological activity and in vivo circulatory half-life of glycoproteins. Human ${\alpha}2$,3-sialyltransferase (${\alpha}2$,3-ST) and ${\beta}1$,4-galactosyltransferase (${\beta}1$,4-GT) are responsible for terminal sialylation and galactosylation, respectively. Enhanced sialylation of human erythropoietin (EPO) by the expression of ${\alpha}2$,3-ST and ${\beta}1$,4-GT was achieved using recombinant Chinese hamster ovary (CHO) cells (EC1). The sialic acid content and sialylation of N-glycans were evaluated by HPLC. When ${\alpha}2$,3-ST was expressed in CHO cells (EC1-ST2), the sialic acid content (moles of sialic acid/mole of EPO) increased from 6.7 to 7.5. In addition, the amount of trisialylated glycans increased from 17.3% to 26.1 %. When ${\alpha}2$,3-ST and ${\beta}1$,4-GT were coexpressed in CHO cells (EC1-GTST15), the degree of sialylation was greater than that in EC1-ST2 cells. In the case of EC1-GTST15 cells, the sialic acid content increased to 8.2 and the proportion of trisialylated glycans was markedly increased from 17.3% to 35.5%. Interestingly, the amount of asialoglycans decreased only in the case of GTST15 cells (21.4% to 14.2%). These results show that coexpression of ${\alpha}2$,3-ST and ${\beta}1$,4-GT is more effective than the expression of ${\alpha}2$,3-ST alone. Coexpression of ${\alpha}2$,3-ST and ${\beta}1$,4-GT did not affect CHO cell growth and metabolism or EPO production. Thus, coexpression of ${\alpha}2$,3-ST and ${\beta}1$,4-GT may be beneficial for producing therapeutic glycoproteins with enhanced sialylation in CHO cells.

• Reproductive and Developmental Biology
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• 제36권2호
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• pp.109-114
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• 2012

We prepared the polyclonal antibody anti-$20{\alpha}$-hydroxysteroid dehydrogenase (anti-$20{\alpha}$-HSD) against the recombinant full-length protein bovine $20{\alpha}$-HSD in Escherichia coli. The specificity of anti-$20{\alpha}$-HSD was demonstrated using Chinese hamster ovary (CHO) cells transfected with recombinant bovine $20{\alpha}$-HSD and bovine placental tissues. According to western blot analysis, anti-$20{\alpha}$-HSD specifically recognizes the 37-kDa protein bovine $20{\alpha}$-HSD. The protein is not present in untransfected CHO cells. Anti-$20{\alpha}$-HSD also recognizes a specific protein in the ovaries and placenta of other animals. Immunostaining was used to detect expression of bovine $20{\alpha}$-HSD protein in the cultured luteal cells during the estrous cycle later.

• 한국가축번식학회지
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• 제27권3호
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• pp.197-206
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• 2003

hFSH는 $\alpha$와 $\beta$ subunit으로 구성된 heterodimer로서 두 subunit의 조합은 활성을 지닌 호르몬의 생산에 있어서 매우 중요한 단계이다. 이 조합과정의 효율을 증대하기 위하여 본 연구에서는 hFSH를 단일사슬의 단백질로 구축하고자 하였으며, 이의 일환으로 각 subunit 대한 cDNA단편을 연결하는 서열로 CTP linker를 도입하였다. 재조합한 hFSH-CTP 유전자는 pseudotype의 retrovirus vector system을 이용하여 CHO 세포와 닭의 배로 각각 전이되었다. CHO 세포에서의 FSH의 생산은 $\alpha$와 $\beta$를 각각 전이한 경우에 비해 hFSH-CTP를 전이한 경우에서 17배 이상 높은 것으로 나타났다. 닭에서는 유전자 전이를 시도한 62개체 중에서 11마리가 부화하였으며 그 중 10마리가 형질전환된 닭인 것으로 RT-PCR을 통하여 확인되었다. 그러나 개체의 혈중 FSH의 생산은 확인하지 못하였다. 이상의 실험 결과를 바탕으로 하여 재조합된 hFSH-CTP는 FSH의 발현에 매우 효율적인 구조로 생각되며, 또한 retrovirus를 이용한 유전자 전이 방법은 형질전환 가금의 생산에 있어서 매우 적절한 방법으로 사료된다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2001년도 추계학술발표대회
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• pp.457-458
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• 2001

To determine the effect of ERp57 expression on thrombopoiein (TPO) productivity in recombinant Chinese hamster ovary (rCHO) cells, TPO producing rCHO cell line with doxycycline-regulated ERp57 expression \Vas developed. The Erp57 expression level could be regulated by addition of different concentrations of doxycycline to culture medium. The doxycycline concentration of I ${\mu}g/mL$ was high enough to suppress the ERp57 expression. Up to 5 ${\mu}g/mL$ doxycycline concentration used in culture medium, no observable cytotoxic effect of doxycycline was detected during culture. Overexpression of ERp57 、 vas found to increase the specific TPO productivity ($q_{Tpo}$) without growth inhibition, probably due to the chaperone-like activity of ERp57 in CHO cells.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVI)
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• pp.37-37
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• 2005

Human chorionic gonadotropin (hCG) is a heterodimeric glycoprotein hormone consisting of non-covalently linked two subunits, the ${\alpha}$ and ${\beta}$ subunit. It has been used as a infertility drug for ovulation to mimic luteinizing hormone $(LH).^{1)}$ A stable cell line was established by transfection of Rc/CMV-i-dhfr-hCG, expression vector containing hCG ${\alpha}-$ and ${\beta}-genes$, into dihydrofolate reductase-deficient CHO cells and subesquent methotrexate-mediated gene amplification. Anchorage-dependent CHO cells were adapted into a serum-free and/or animal component-free suspension medium through gradual serum weaning for the hCG production. The established cell line showed typical morphological characteristics and growth profile of CHO cells, and could produce FSH with passage-to-passage consistency. The high density perfusion culture of the CHO cells was carried out in Celligen Plus bioreactor equipped with a spin-filter as a internal cell retention device. The cell density reached up to $>1x10^{7}$ cells/ml in less than 7 days and a perfusion-control strategy based on cellular consumption rates of glucose was $established.^{2)}$ Biologically active recombinant hCG was purified by a series of chromatographic steps including anion exchange chromatography and hydrophobic interaction chromatography to homogeneity. The highly purified recombinant hCG was characterized for physicochemical, immunological and biological properties.