Immortalized cell lines offer the possibility of an inexhaustible supply of cells that can be used as models of animal or human tissues.
Most available cell line models are poor representations of cells found in intact tissues. Cell lines have traditionally been developed from cells isolated from naturally occurring cancers as well as through selection from primary cells that undergo spontaneous immortalization. In addition, researchers often introduce viral genes to disrupt the cell cycle.
These processes allow primary cells to become immortal, but they can also have an impact on cellular functions, resulting in cells that often times behave differently than primary cells.
Exploitation of telomerase activity via introduction of the hTERT gene results in immortalization of cells while retaining more in-vivo like properties. In addition, the use of a temperature dependent, conditional immortalization approach utilizing Large T-Antigen allows the immortalization to be reversed and the cells to revert to their original characteristics.
Both the hTERT as well as SV40 large T-antigen technologies allow development of cell lines from a wide range of human and animal tissues, and of novel models relevant to drug discovery based on lines from people with particular diseases.
Lonza Conditionally Immortalized cells are created using one or both immortalization technologies. Lonza designates cell lines containing SV40 large T-antigen as conditionally immortalized, whereas cell lines containing only hTERT are considered terminally immortalized.
Why conditional immortalization via SV40 large T-antigen?
During recent years increased pressure has been placed on drug development teams to deliver drugs to the market that meet the proscribed claims, have no side effects, and perform no matter the patients genetic background.
To add to the challenge, drug development resourcing is not growing at the same rate as external costs to validate new drugs for the market. Now more than ever drug discovery researchers need tools that facilitate HTS screening of cells earlier in the drug discovery process, eliminate poor drug candidates early and focus on more promising candidates.
To discover a new drug, researchers must evaluate a large number of compounds for efficacy and toxicity. Several accepted models exist using animals or cells, but all have inherent limits for quick evaluation using high throughput screening techniques and require species extrapolation to evaluate the data.
Live animal models yield a rich supply of data but are not cost effective for high throughput screening. Non-immortalized, primary cells may best represent normal physiology, but are typically not available in the large, uniform quantities needed for HTS applications. Though conventionally immortalized cell lines can divide indefinitely into large homogeneous cell populations needed for HTS applications, they do not behave like normal cells.
Conditional immortalization allows, at a permissive temperature, production of high volumes of uniform cell populations. By changing the culture temperature the cells stop dividing, irreversibly, allowing for differentiation so that the cells can express normal function and phenotype once again.