Immortalization

Immortalization refers to the process by which cells acquire the ability to proliferate indefinitely, a characteristic of most cancer cells. This process is often associated with telomere lengthening and the activation of telomerase, an enzyme that adds DNA sequence repeats to the 3' end of DNA strands in the telomere regions.

Mechanism

Immortalization is typically achieved through the activation of telomerase, a ribonucleoprotein enzyme that adds the telomere repeat TTAGGG to the ends of chromosomes. This prevents the DNA from being degraded during replication, allowing the cell to divide indefinitely without losing genetic information.

In normal cells, telomeres shorten with each cell division due to the end-replication problem. Once the telomeres reach a critically short length, the cell enters a state of senescence or apoptosis. However, in immortalized cells, telomerase prevents this telomere shortening, allowing the cell to bypass senescence and continue dividing.

Role in Cancer

Immortalization is a key step in the development of cancer. Most human cancers have upregulated telomerase activity, which allows them to divide indefinitely and form tumors. In addition, some cancer cells can achieve immortalization through alternative lengthening of telomeres (ALT), a mechanism that involves recombination-mediated telomere elongation.

Immortal Cell Lines

Immortal cell lines, such as the HeLa cell line, are often used in scientific research. These cell lines have undergone immortalization, either naturally or artificially, and can be cultured indefinitely in the lab. They provide a valuable tool for studying cell biology, genetics, and disease.

See Also

• Cell senescence
• Telomere
• Telomerase
• Cancer
• HeLa