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CHO Expression System

Introduction

Chinese Hamster Ovary (CHO) cells are one of the most established platforms for recombinant protein production, especially in the biopharmaceutical industry. Their ability to produce complex proteins with human-like post-translational modifications (PTMs), along with their scalability and adaptability to large-scale production, has made them indispensable for producing monoclonal antibodies, hormones, and other therapeutic proteins.

Mechanisms of Protein Expression in CHO Cells

  • Transfection of CHO Cells:
    • Chemical Methods: Polyethyleneimine (PEI) and lipofection are commonly used to mediate DNA uptake.
    • Electroporation: A physical method that introduces DNA into cells via electrical pulses.
    • Strategies: Stable transfection integrates the transgene into the host genome for long-term expression, while transient transfection is used for rapid, short-term production.
  • Transcription and Translation:
    • Promoters: Cytomegalovirus (CMV) promoter for high expression levels; Elongation factor-1 alpha (EF1α) promoter for stability over extended periods.
    • Transcription results in mRNA, which is translated into protein by the host’s ribosomal machinery.
  • Protein Folding and Assembly in the Endoplasmic Reticulum (ER):
    • Chaperones (e.g., BiP, PDI) assist in achieving correct conformations.
    • Disulfide bond formation and glycosylation are critical steps for functional protein production.
    • Misfolded proteins are degraded through the ER-associated degradation (ERAD) pathway.
  • Post-Translational Modifications:
    • N-linked glycosylation: Essential for protein stability, solubility, and biological activity.
    • Glycan Maturation: CHO systems can mimic human glycan structures, including complex sialylated glycans.
  • Secretion into the Culture Medium: Properly folded and modified proteins are transported to the Golgi apparatus and secreted into the culture medium for easy harvest.
  • Culture Optimization for High Yields: Suspension systems under fed-batch conditions enhance productivity, with media optimization further boosting yields.
  • Gene Amplification Strategies: Systems such as dihydrofolate reductase (DHFR) and glutamine synthetase (GS) increase transgene copy numbers for higher protein production.

Advantages of CHO Systems

  • Human-Like Post-Translational Modifications: Ensures therapeutic efficacy and reduced immunogenicity.
  • High Scalability: Ideal for industrial-scale production.
  • Versatility: Adaptable to various culture conditions and genetic modifications.
  • Regulatory Compliance: Widely accepted for biopharmaceutical production.

Applications of CHO Expression Systems

  • Therapeutics: Produces monoclonal antibodies (e.g., Rituximab, Trastuzumab), hormones (e.g., Erythropoietin), and enzymes (e.g., Alpha-galactosidase).
  • Vaccines: Used for recombinant protein subunit vaccines and virus-like particles (e.g., SARS-CoV-2).
  • Diagnostics: Produces diagnostic proteins with high purity and activity.

Challenges in CHO Systems

  • Cost: Mammalian systems require expensive media and longer culture times compared to bacterial systems.
  • Complex Glycoforms: Maintaining consistency in glycan structures is critical for regulatory approval.
  • Yield Optimization: Achieving high yields without compromising protein quality remains a technical challenge.

GenScript Services for CHO Expression Systems

Conclusion

CHO expression systems are the cornerstone of modern biopharmaceutical manufacturing, combining scalability, flexibility, and human-like PTMs to meet rigorous therapeutic demands. Advances in genetic engineering, cell line development, and culture optimization continue to push the boundaries of CHO cell capabilities, ensuring their pivotal role in the production of life-saving biologics and vaccines.


Related Biology Tools

  • GenSmart™ Codon Optimization

    GenSmart Optimization is a free online tool for performing codon optimization to improve gene expression. GenScript's patented algorithms are integrated into the tool to optimize the computing capability of high-performance sequence generation.

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  • DNA Construct Design Tool

    GenSmart™ Design is a free online DNA construct design tool developed by GenScript. GenSmart™ Design has two design modules, the Create Construct module for individual plasmid design and the Create Library module for DNA library design.

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  • Codon Frequency Tables

    This online tool shows commonly used genetic codon frequency table in expression host organisms including Escherichia coli and other common host organisms.

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Service and Products

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Immunoassay Development Services

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