Mammalian Expression

Mammalian cell-based expression is the dominant system for the production of therapeutic recombinant proteins. Their capacity to handle complex post-translational modifications, folding and assembly of recombinant proteins and protein complexes is superior to other systems. Mammalian expression vectors have been engineered to contain elements that improve expression and are generally more complex than vectors from other systems.

There are two main methods for recombinant protein production in mammalian cells i.e. stably transfected and transiently transfected cell lines. Stably transfected cell lines enable continuous expression of the recombinant protein and have been shown to produce high yields. The creation of a stable cell line can take up to several months to complete.

A transient transfection can be used for small- to large-scale expression cultures. Recent improvements to the method have been able to increase yields from milligram to gram quantities. The advantages of a transient transfection method lie in the shorter timeframe from DNA delivery to protein harvest.



Transient expression and purification

  • Cloning and expression: Subclone gene of interest into suitable mammalian cell transient expression vector
  • Transient transfection, expression evaluation, and optimization

Stable expression cell lines

  • Transient transfection and selectin for stably transfected cells
  • Cell line development for pools of stable cells
  • Cell line development by screening and expansion of high-expressing single clone


  • Transient expression is easy and rapid
  • Providing all the correct post-translational modifications and proper folding found in mammalian cells
  • Stable transfection results in higher yield, scalability and reproducible production
  • Works well for secreted and membrane proteins


  • Expensive
  • Difficult to scale-up
  • Yields of intracellular proteins are low
  • Length expression time for stable transfection


  • Production of monoclonal antibody
  • Production of urokinase
  • Production of follicle stimulating hormone
  • RNA interference

Mammalian cell  expression systems – HEK293 and CHO Figure 1. Mammalian cell expression systems – HEK293 and CHO

See Creative Biostructure’s cell-free and cell-based expression services.


  1. Scott E. Martin and Natasha J. Caplen. Applications of RNA Interference in Mammalian Systems. 2007.Annual Review of Genomics and Human Genetics. Vol. 8: 81-108. DOI: 10.1146/annurev.genom.8.080706.092424
  2. Kishwar Hayat Khan. Gene Expression in Mammalian Cells and its Applications. Adv Pharm Bull. 2013 Dec; 3(2): 257–263. doi: 10.5681/apb.2013.042
For Research Use Only. Not for use in diagnostic or therapeutic procedures.

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