Stable Cell Lines
Stable cell lines are crucial laboratory tools that over-express a protein of interest in order to screen experimental drugs, study gene functions or produce therapeutic proteins (including recombinant antibodies). The cell lines indefinitely reproduce and continue to express the transgene consistently during that time period.
Generation of a stable cell line refers to the process of developing homogenous populations of cells that demonstrate expression of a transfected gene insert. The transfected gene integrates into the genome of the host cell, and as a result, are able to express the transfected genetic material. This is opposite of transient transfected cells that express the transfected DNA for a short time (e.g. 8 to 96 hours).
Broadly, the generation of stable cell lines is a two step procedure. First, exogenous plasmid DNA is transfected into the host cell line. This is followed by applying antibiotics to select only those cells exhibiting the desired plasmid DNA expression. Nucleic acids to be inserted can be in the form of plasmid DNA, and encode microRNA (miRNA), short interfering RNA (siRNA) or full length mRNA transcripts.
There are many attributes to developing stable cell lines, such as the DNA vector used, the protein to be studied, the cell line selected, reagents used and the transfection method. Also, certain cell lines respond better to specific transfection methods, culture media or reagents. Identification of positive clones exhibiting the desired phenotype is extremely laborious and characterization of clonal cell lines takes many weeks. Also, toxicity due to the protein being expressed may make it impossible to develop a stable cell line. There are several companies that specialize in generating stably expressing cell lines and provide commercially available service with a relatively short turnaround period (4-6 weeks).
Utilizing a stable mammalian cell line for production of target molecules may increase the acceptability of the final gene product as pipeline development nears production. However, the production of these stable cell lines can be expensive, complex and time-consuming. Biology contract research organizations provides specialized development of stable cell line services, with some companies even providing a 28-day day generation of stable cell line service (see description here). Scientists use stable cell lines for diverse applications, ranging from studying cell differentiation, gene expression, cellular events, toxicity and production of recombinant antibodies and proteins.