A single point mutation in Drosophila dihydrofolate reductase confers methotrexate resistance to a transgenic CHO cell line

Genome ◽  
2003 ◽  
Vol 46 (4) ◽  
pp. 707-715 ◽  
Author(s):  
K Neumann ◽  
K M Al-Batayneh ◽  
M J Kuiper ◽  
J Parsons-Sheldrake ◽  
M G Tyshenko ◽  
...  
Keyword(s):  
Cell Line ◽  
Point Mutation ◽  
Cell Lines ◽  
Dihydrofolate Reductase ◽  
Cho Cells ◽  
Chinese Hamster ◽  
Single Point Mutation ◽  
Parental Line ◽  
Wild Type ◽  
Drosophila Cell

Sequence analysis of a cDNA encoding dihydrofolate reductase (DHFR) from a selected methotrexate-resistant Drosophila melanogaster cell line (S3MTX) revealed a substitution of Gln for Leu at position 30. Although the S3MTX cells were ~1000 fold more resistant to methotrexate (MTX), the karyotype was similar to the parental line and did not show elongated chromosomes. Furthermore, kinetic analysis of the recombinant enzyme showed a decreased affinity for MTX by the mutant DHFR. To determine if the resistance phenotype could be attributed to the mutant allele, Drosophila Dhfr cDNAs isolated from wild type and S3MTX cells were expressed in Chinese hamster ovary (CHO) cells lacking endogenous DHFR. The heterologous insect DHFRs were functional in transgenic clonal cell lines, showing ~400-fold greater MTX resistance in the cell line transfected with the mutant Dhfr than the wild type Dhfr. Resistance to other antifolates in the CHO cells was consistent with the drug sensitivities seen in the respective Drosophila cell lines. ELevated Levels of Dhfr transcript and DHFR in transgenic CHO cells bearing the mutant cDNA were not seen. Taken together, these results demonstrate that a single substitution in Drosophila DHFR alone can confer Levels of MTX resistance comparable with that observed after considerable gene amplification in mammalian cells.Key words: dihydrofolate reductase, methotrexate, drug resistance, point mutation.

Chromosome-mediated gene transfer of hydroxyurea resistance and amplification of ribonucleotide reductase activity

1983 ◽  
Vol 3 (6) ◽  
pp. 1053-1061
Author(s):  
W H Lewis ◽  
P R Srinivasan
Keyword(s):  
Cell Line ◽  
Cell Lines ◽  
Ribonucleotide Reductase ◽  
Chinese Hamster ◽  
Fold Increase ◽  
Resistant Cell ◽  
Plating Efficiency ◽  
Wild Type Cell ◽  
Wild Type ◽  
Metaphase Chromosomes

Metaphase chromosomes purified from a hydroxyurea-resistant Chinese hamster cell line were able to transform recipient wild-type cells to hydroxyurea resistance at a frequency of 10(-6). Approximately 60% of the resulting transformant clones gradually lost hydroxyurea resistance when cultivated for prolonged periods in the absence of drug. One transformant was subjected to serial selection in higher concentrations of hydroxyurea. The five cell lines generated exhibited increasing relative plating efficiency in the presence of the drug and a corresponding elevation in their cellular content of ribonucleotide reductase. The most resistant cell line had a 163-fold increase in relative plating efficiency and a 120-fold increase in enzyme activity when compared with the wild-type cell line. The highly hydroxyurea-resistant cell lines had strong electron paramagnetic resonance signals characteristic of an elevated level of the free radical present in the M2 subunit of ribonucleotide reductase. Two-dimensional electrophoresis of cell-free extracts from one of the resistant cell lines indicated that a 53,000-dalton protein was present in greatly elevated quantities when compared with the wild-type cell line. These data suggest that the hydroxyurea-resistant cell lines may contain an amplification of the gene for the M2 subunit of ribonucleotide reductase.

scholarly journals Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells.

1993 ◽  
Vol 13 (9) ◽  
pp. 5175-5185 ◽  
Author(s):  
M J Evans ◽  
J E Metherall
Keyword(s):  
Transcriptional Regulation ◽  
Cell Lines ◽  
Transcriptional Activation ◽  
Cho Cells ◽  
Mutant Cell ◽  
Chinese Hamster ◽  
Wild Type ◽  
Hmg Coa Reductase ◽  
Low Levels ◽  
Coa Reductase

Cholesterol biosynthesis and uptake are controlled by a classic end product-feedback mechanism whereby elevated cellular sterol levels suppress transcription of the genes encoding 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase, HMG-CoA reductase, and the low-density lipoprotein receptor. The 5'-flanking region of each gene contains a common cis-acting element, designated the sterol regulatory element (SRE), that is required for transcriptional regulation. In this report, we describe mutant Chinese hamster ovary (CHO) cell lines that lack SRE-dependent transcription. Mutant cell lines were isolated on the basis of their ability to survive treatment with amphotericin B, a polyene antibiotic that kills cells by interacting with cholesterol in the plasma membrane. Four mutant lines (SRD-6A, -B, -C, and -D) were found to be cholesterol auxotrophs and demonstrated constitutively low levels of mRNA for all three sterol-regulated genes even under conditions of sterol deprivation. The mutant cell lines were found to be genetically recessive, and all four lines belonged to the same complementation group. When transfected with a plasmid containing a sterol-regulated promoter fused to a bacterial reporter gene, SRD-6B cells demonstrated constitutively low levels of transcription, in contrast to wild-type CHO cells, which increased transcription under conditions of sterol deprivation. Mutation of the SREs in this plasmid prior to transfection reduced the level of expression in wild-type CHO cells deprived of sterols to the level of expression found in SRD-6B cells. The defect in SRD-6 cells is limited to transcriptional regulation, since posttranscriptional mechanisms of sterol-mediated regulation were intact: the cells retained the ability to posttranscriptionally suppress HMG-CoA reductase activity and to stimulate acyl-CoA:cholesterol acyltransferase activity. These results suggest that SRD-6 cells lack a factor required for SRE-dependent transcriptional activation. We contrast these cells with a previously isolated oxysterol-resistant cell line (SRD-2) that lacks a factor required for SRE-dependent transcriptional suppression and propose a model for the role of these genetically defined factors in sterol-mediated transcriptional regulation.

The dihydrofolate reductase amplicons in different methotrexate-resistant Chinese hamster cell lines share at least a 273-kilobase core sequence, but the amplicons in some cell lines are much larger and are remarkably uniform in structure

1988 ◽  
Vol 8 (12) ◽  
pp. 5268-5279
Author(s):  
J E Looney ◽  
C Ma ◽  
T H Leu ◽  
W F Flintoff ◽  
W B Troutman ◽  
...  
Keyword(s):  
Cell Line ◽  
Cell Lines ◽  
Dihydrofolate Reductase ◽  
Dna Sequences ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Resistant Cell ◽  
Pulse Field ◽  
Ovary Cell ◽  
Type I

We have previously cloned and characterized two different dihydrofolate reductase amplicon types from a methotrexate-resistant Chinese hamster ovary cell line (CHOC 400). The largest of these (the type I amplicon) is 273 kilobases (kb) in length. In the present study, we utilized clones from the type I amplicon as probes to analyze the size and variability of the amplified DNA sequences in five other independently isolated methotrexate-resistant Chinese hamster cell lines. Our data indicated that the predominant amplicon types in all but one of these cell lines are larger than the 273-kb type I sequence. In-gel renaturation experiments as well as hybridization analysis of large SfiI fragments separated by pulse-field gradient gel electrophoresis showed that two highly resistant cell lines (A3 and MK42) have amplified very homogeneous core sequences that are estimated to be at least 583 and 653 kb in length, respectively. Thus, the sizes of the major amplicon types can be different in different drug-resistant Chinese hamster cell lines. However, there appears to be less heterogeneity in size and sequence arrangement within a given methotrexate-resistant Chinese hamster cell line than has been reported for several other examples of DNA sequence amplification in mammalian systems.

Replication in the amplified dihydrofolate reductase domain in CHO cells may initiate at two distinct sites, one of which is a repetitive sequence element

1989 ◽  
Vol 9 (2) ◽  
pp. 532-540
Author(s):  
B Anachkova ◽  
J L Hamlin
Keyword(s):  
Dna Replication ◽  
Cell Line ◽  
Dihydrofolate Reductase ◽  
Cho Cells ◽  
Chinese Hamster ◽  
Replication Initiation ◽  
Ovary Cell ◽  
Sequence Element ◽  
Hybridization Probes ◽  
Ovary Cell Line

To study initiation of DNA replication in mammalian chromosomes, we have established a methotrexate-resistant Chinese hamster ovary cell line (CHOC 400) that contains approximately 1,000 copies of the early replicating dihydrofolate reductase (DHFR) domain. We have previously shown that DNA replication in the prevalent 243-kilobase (kb) amplicon type in this cell line initiates somewhere within a 28-kb region located downstream from the DHFR gene. In an attempt to localize the origin of replication with more precision, we blocked the progress of replication forks emanating from origins at the beginning of the S phase by the introduction of trioxsalen cross-links at 1- to 5-kb intervals in the parental double-stranded DNA. The small DNA fragments synthesized under these conditions (which should be centered around replication origins) were then used as hybridization probes on digests of cosmids and plasmids from the DHFR domain. These studies suggested that in cells synchronized by this regimen, DNA replication initiates at two separate sites within the previously defined 28-kb replication initiation locus, in general agreement with results described in the accompanying paper (T.-H. Leu and J. L. Hamlin, Mol. Cell. Biol. 9:523-531, 1989). One of these sites contains a repeated DNA sequence element that is found at or near many other initiation sites in the genome, since it was also highly enriched in the early replicating DNA isolated from cross-linked CHO cells that contain only two copies of the DHFR domain.

scholarly journals Multi-omics profiling of CHO parental hosts reveals cell line-specific variations in bioprocessing traits

2019 ◽  
Author(s):  
Meiyappan Lakshmanan ◽  
Yee Jiun Kok ◽  
Alison P. Lee ◽  
Sarantos Kyriakopoulos ◽  
Hsueh Lee Lim ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Line ◽  
Cell Lines ◽  
Cho Cells ◽  
Cell Cycle Progression ◽  
Chinese Hamster ◽  
Suspension Cultures ◽  
Host Cells ◽  
Phenotypic Traits ◽  
Cell Factories

AbstractChinese hamster ovary (CHO) cells are the most prevalent mammalian cell factories for producing recombinant therapeutic proteins due to their ability to synthesize human-like post-translational modifications and ease of maintenance in suspension cultures. Currently, a wide variety of CHO host cell lines have been developed; substantial differences exist in their phenotypes even when transfected with the same target vector. However, relatively less is known about the influence of their inherited genetic heterogeneity on phenotypic traits and production potential from the bioprocessing point of view. Herein, we present a global transcriptome and proteome profiling of three commonly used parental cell lines (CHO-K1, CHO-DXB11 and CHO-DG44) in suspension cultures and further report their growth-related characteristics, and N- and O-glycosylation patterns of host cell proteins (HCPs). The comparative multi-omics analysis indicated that some physiological variations of CHO cells grown in the same media are possibly originated from the genetic deficits, particularly in the cell cycle progression. Moreover, the dihydrofolate reductase deficient DG44 and DXB11 possess relatively less active metabolism when compared to K1 cells. The protein processing abilities and the N- and O-glycosylation profiles also differ significantly across the host cell lines, suggesting the need to select host cells in a rational manner for the cell line development on the basis of recombinant protein being produced.

scholarly journals Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells

1993 ◽  
Vol 13 (9) ◽  
pp. 5175-5185
Author(s):  
M J Evans ◽  
J E Metherall
Keyword(s):  
Transcriptional Regulation ◽  
Cell Lines ◽  
Transcriptional Activation ◽  
Cho Cells ◽  
Mutant Cell ◽  
Chinese Hamster ◽  
Wild Type ◽  
Hmg Coa Reductase ◽  
Low Levels ◽  
Coa Reductase

Cholesterol biosynthesis and uptake are controlled by a classic end product-feedback mechanism whereby elevated cellular sterol levels suppress transcription of the genes encoding 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase, HMG-CoA reductase, and the low-density lipoprotein receptor. The 5'-flanking region of each gene contains a common cis-acting element, designated the sterol regulatory element (SRE), that is required for transcriptional regulation. In this report, we describe mutant Chinese hamster ovary (CHO) cell lines that lack SRE-dependent transcription. Mutant cell lines were isolated on the basis of their ability to survive treatment with amphotericin B, a polyene antibiotic that kills cells by interacting with cholesterol in the plasma membrane. Four mutant lines (SRD-6A, -B, -C, and -D) were found to be cholesterol auxotrophs and demonstrated constitutively low levels of mRNA for all three sterol-regulated genes even under conditions of sterol deprivation. The mutant cell lines were found to be genetically recessive, and all four lines belonged to the same complementation group. When transfected with a plasmid containing a sterol-regulated promoter fused to a bacterial reporter gene, SRD-6B cells demonstrated constitutively low levels of transcription, in contrast to wild-type CHO cells, which increased transcription under conditions of sterol deprivation. Mutation of the SREs in this plasmid prior to transfection reduced the level of expression in wild-type CHO cells deprived of sterols to the level of expression found in SRD-6B cells. The defect in SRD-6 cells is limited to transcriptional regulation, since posttranscriptional mechanisms of sterol-mediated regulation were intact: the cells retained the ability to posttranscriptionally suppress HMG-CoA reductase activity and to stimulate acyl-CoA:cholesterol acyltransferase activity. These results suggest that SRD-6 cells lack a factor required for SRE-dependent transcriptional activation. We contrast these cells with a previously isolated oxysterol-resistant cell line (SRD-2) that lacks a factor required for SRE-dependent transcriptional suppression and propose a model for the role of these genetically defined factors in sterol-mediated transcriptional regulation.

scholarly journals Chromosome-mediated gene transfer of hydroxyurea resistance and amplification of ribonucleotide reductase activity.

1983 ◽  
Vol 3 (6) ◽  
pp. 1053-1061 ◽  
Author(s):  
W H Lewis ◽  
P R Srinivasan
Keyword(s):  
Cell Line ◽  
Cell Lines ◽  
Ribonucleotide Reductase ◽  
Chinese Hamster ◽  
Fold Increase ◽  
Resistant Cell ◽  
Plating Efficiency ◽  
Wild Type Cell ◽  
Wild Type ◽  
Metaphase Chromosomes

Metaphase chromosomes purified from a hydroxyurea-resistant Chinese hamster cell line were able to transform recipient wild-type cells to hydroxyurea resistance at a frequency of 10(-6). Approximately 60% of the resulting transformant clones gradually lost hydroxyurea resistance when cultivated for prolonged periods in the absence of drug. One transformant was subjected to serial selection in higher concentrations of hydroxyurea. The five cell lines generated exhibited increasing relative plating efficiency in the presence of the drug and a corresponding elevation in their cellular content of ribonucleotide reductase. The most resistant cell line had a 163-fold increase in relative plating efficiency and a 120-fold increase in enzyme activity when compared with the wild-type cell line. The highly hydroxyurea-resistant cell lines had strong electron paramagnetic resonance signals characteristic of an elevated level of the free radical present in the M2 subunit of ribonucleotide reductase. Two-dimensional electrophoresis of cell-free extracts from one of the resistant cell lines indicated that a 53,000-dalton protein was present in greatly elevated quantities when compared with the wild-type cell line. These data suggest that the hydroxyurea-resistant cell lines may contain an amplification of the gene for the M2 subunit of ribonucleotide reductase.

scholarly journals Replication in the amplified dihydrofolate reductase domain in CHO cells may initiate at two distinct sites, one of which is a repetitive sequence element.

1989 ◽  
Vol 9 (2) ◽  
pp. 532-540 ◽  
Author(s):  
B Anachkova ◽  
J L Hamlin
Keyword(s):  
Dna Replication ◽  
Cell Line ◽  
Dihydrofolate Reductase ◽  
Cho Cells ◽  
Chinese Hamster ◽  
Replication Initiation ◽  
Ovary Cell ◽  
Sequence Element ◽  
Hybridization Probes ◽  
Ovary Cell Line

To study initiation of DNA replication in mammalian chromosomes, we have established a methotrexate-resistant Chinese hamster ovary cell line (CHOC 400) that contains approximately 1,000 copies of the early replicating dihydrofolate reductase (DHFR) domain. We have previously shown that DNA replication in the prevalent 243-kilobase (kb) amplicon type in this cell line initiates somewhere within a 28-kb region located downstream from the DHFR gene. In an attempt to localize the origin of replication with more precision, we blocked the progress of replication forks emanating from origins at the beginning of the S phase by the introduction of trioxsalen cross-links at 1- to 5-kb intervals in the parental double-stranded DNA. The small DNA fragments synthesized under these conditions (which should be centered around replication origins) were then used as hybridization probes on digests of cosmids and plasmids from the DHFR domain. These studies suggested that in cells synchronized by this regimen, DNA replication initiates at two separate sites within the previously defined 28-kb replication initiation locus, in general agreement with results described in the accompanying paper (T.-H. Leu and J. L. Hamlin, Mol. Cell. Biol. 9:523-531, 1989). One of these sites contains a repeated DNA sequence element that is found at or near many other initiation sites in the genome, since it was also highly enriched in the early replicating DNA isolated from cross-linked CHO cells that contain only two copies of the DHFR domain.

scholarly journals The dihydrofolate reductase amplicons in different methotrexate-resistant Chinese hamster cell lines share at least a 273-kilobase core sequence, but the amplicons in some cell lines are much larger and are remarkably uniform in structure.

1988 ◽  
Vol 8 (12) ◽  
pp. 5268-5279 ◽  
Author(s):  
J E Looney ◽  
C Ma ◽  
T H Leu ◽  
W F Flintoff ◽  
W B Troutman ◽  
...  
Keyword(s):  
Cell Line ◽  
Cell Lines ◽  
Dihydrofolate Reductase ◽  
Dna Sequences ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Resistant Cell ◽  
Pulse Field ◽  
Ovary Cell ◽  
Type I

We have previously cloned and characterized two different dihydrofolate reductase amplicon types from a methotrexate-resistant Chinese hamster ovary cell line (CHOC 400). The largest of these (the type I amplicon) is 273 kilobases (kb) in length. In the present study, we utilized clones from the type I amplicon as probes to analyze the size and variability of the amplified DNA sequences in five other independently isolated methotrexate-resistant Chinese hamster cell lines. Our data indicated that the predominant amplicon types in all but one of these cell lines are larger than the 273-kb type I sequence. In-gel renaturation experiments as well as hybridization analysis of large SfiI fragments separated by pulse-field gradient gel electrophoresis showed that two highly resistant cell lines (A3 and MK42) have amplified very homogeneous core sequences that are estimated to be at least 583 and 653 kb in length, respectively. Thus, the sizes of the major amplicon types can be different in different drug-resistant Chinese hamster cell lines. However, there appears to be less heterogeneity in size and sequence arrangement within a given methotrexate-resistant Chinese hamster cell line than has been reported for several other examples of DNA sequence amplification in mammalian systems.

scholarly journals Using Metabolomics to Identify Cell Line-Independent Indicators of Growth Inhibition for Chinese Hamster Ovary Cell-Based Bioprocesses

Metabolites ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 199 ◽  
Author(s):  
Nicholas Alden ◽  
Ravali Raju ◽  
Kyle McElearney ◽  
James Lambropoulos ◽  
Rashmi Kshirsagar ◽  
...  
Keyword(s):  
Growth Inhibition ◽  
Cell Line ◽  
Cell Lines ◽  
Chinese Hamster Ovary ◽  
Cho Cells ◽  
Feeding Strategy ◽  
Chinese Hamster ◽  
Ovary Cell ◽  
Growth Stages ◽  
Cho Cell

Chinese hamster ovary (CHO) cells are widely used for the production of biopharmaceuticals. Efforts to improve productivity through medium design and feeding strategy optimization have focused on preventing the depletion of essential nutrients and managing the accumulation of lactate and ammonia. In addition to ammonia and lactate, many other metabolites accumulate in CHO cell cultures, although their effects remain largely unknown. Elucidating these effects has the potential to further improve the productivity of CHO cell-based bioprocesses. This study used untargeted metabolomics to identify metabolites that accumulate in fed-batch cultures of monoclonal antibody (mAb) producing CHO cells. The metabolomics experiments profiled six cell lines that are derived from two different hosts, produce different mAbs, and exhibit different growth profiles. Comparing the cell lines’ metabolite profiles at different growth stages, we found a strong negative correlation between peak viable cell density (VCD) and a tryptophan metabolite, putatively identified as 5-hydroxyindoleacetaldehyde (5-HIAAld). Amino acid supplementation experiments showed strong growth inhibition of all cell lines by excess tryptophan, which correlated with the accumulation of 5-HIAAld in the culture medium. Prospectively, the approach presented in this study could be used to identify cell line- and host-independent metabolite markers for clone selection and bioprocess development.

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