The Need for Custom Cell Lines
Even with the wide number of cell lines available for research purposes today, there are still times when the exact cell line you need isn’t available. This means you may want or need to develop a custom cell line for your study.
However, developing stable cell lines can be time consuming and complex. Therefore, many researchers turn to commercial vendors to develop stable cell lines for cell-based assays such as drug screening, and protein production.
Here we review the key features to consider before starting the custom cell line development process.
Custom Cell Line Key Features
Host Cell Line
Most commonly, custom cell lines are created in easy-to-transfect mammalian cell lines e.g. CHO, HEK 293, HCT 116, and HeLa. Hard-to-transfect options include fibroblasts, endothelium-derived cells, and bone marrow–derived cells lines. You may already know what background you need, and if not a selected vendor should be able to advise on the best route to take for optimum results.
Your target will depend on your research need, but it’s important to know there’s a wide variety of custom cell lines that can be created, including
- Knock-in, including adding tags/reporter molecules to your gene of interest
- Knockout, removing an endogenous gene
- Gene activation, with endogenous gene expression activated
- Gene repression, the reverse of above, down regulating or repressing an endogenous gene
- Expression of exogenous genes, including in inducible systems
You may be looking to develop a cell line with a tagged protein of interest, meaning a reporter molecule will need to be introduced. There are a number of common reporter molecules available including fluorescence (e.g. GFP) and luciferase.
A fluorescent reporter, if appropriate, often provides the simpler approach, as you just need to introduce the genetic modification. When using a luciferase system, you will also need to introduce the correct substrate (luciferin) to studies to be able to measure luminescence.
There are multiple methods available for developing custom cell lines, with vendors often offering their own platforms and services. Two common techniques are lentiviral transduction and CRISPR-Cas9, which are also being combined by vendors such as Genscript.
Certain gene editing methods can cause undesired effects on the cell line. For example, when creating isogenic gene edited cell lines, recombinant adeno-associated virus (rAAV) technology is known to leave a “footprint” behind and typically generates a heterozygous mutation. This means that CRISPR is often the preferred option, as it can generate homozygous, footprint free gene edited cell lines.
Timelines and Budget
Timelines and budget will vary greatly dependent on all of the above factors – is your background cell line hard to transfect, what type of cell line are you generating, and which method are you using. Horizon, for example, provides three packages using CRISPR-Cas9 with timelines ranging from 10 to 20 weeks as a baseline.