- A cell line is a collection of cells originating from one cell.
- Cell lines are typically kept in a growth medium in tubes, flasks, or dishes - called in vitro cell culture. Here, they can continue to divide indefinitely.
- In comparison to freshly derived cells (called “primary” cells), in which gene expression can vary from cell to cell, each cell line comprises many cells that are genetically identical.
- Cell lines are created in two main ways:
They can be developed directly from a living organism (e.g., a patient or an animal); in this case, a single cell may be stimulated to allow it to expand into multiple cells. This is sometimes called “clonal expansion,” although no cloning is used. Here, “clonal” refers to the fact that the cells are all clones of each other (i.e., identical).
They can originate from a living organism but be maintained over many years (e.g., a commercially obtained cell line). These cells are produced similarly to the method described above, but they go through more rounds of cell division to create a stable profile for each cell line.
- Using a cell line allows each cell in an experiment to have a similar response because genetic variation is minimal. This can help researchers to see differences between test groups more clearly.
- Because cell lines are genetically the same, it is easier to replicate experiments across research groups and over multiple experiments in one laboratory, enabling researchers to better validate their results.
- Cell lines are typically easier to grow in the laboratory than primary cells, and it’s easier to obtain a large number of cells from a cell line than from primary cells. Large numbers of cells are needed for many types of functional and genetic experiments - without cell lines, many of these experiments would be nearly impossible.
- It is often easier to obtain cell lines representing a disease than it is to obtain primary cells from patients (e.g., liver cancer cell lines compared to samples from liver biopsies).
- Because they are grown in a laboratory setting after being taken from an individual, cell lines are a somewhat artificial system, and they can accumulate changes over time. Some cell lines are also created by introducing additional DNA to make them continue to grow and divide in culture. These changes mean that they do not always represent what occurs in vivo (i.e., inside an organism).
- Cell culture systems are typically two-dimensional (with the exception of 3D culture systems), and they often lack some of the aspects of life inside an organism, like contact with other cell types or with tissue surfaces.
- Even though cell lines can be obtained commercially from standardized sources, cell lines can be contaminated by other cell lines either before or after they are received by a lab. Contamination can drastically alter results. Cell lines must be frequently tested to make sure that researchers are using the cells they think they are.
- Similarly, cell lines can become contaminated with microorganisms like mycoplasma, which can affect their behavior. Testing for mycoplasma contamination should be performed regularly.
What to watch for
- Consider what type of cell line(s) the researchers used. Does the cell line act as a good model for the topic being studied? For example, do the researchers use breast cancer cell lines for a study on breast cancer, or are they using prostate cancer cells?
- How many cell lines are used? Often, researchers will use more than one cell line to validate the results found in the first cell line.
- Did the researchers confirm the identity of their cell line before conducting experiments?
- Did the researchers routinely test for mycoplasma contamination, and if so, do they confirm that the results were negative?
- Does the culture system resemble the organism of interest? If not, additional experiments with primary cells and/or in vivo might be needed to confirm the results.