- Cell immortalization is a biological process where normal cells, which typically have a limited lifespan, are transformed into cells that can divide indefinitely. This process occurs naturally in cancer cells and can be induced artificially in laboratory settings for research purposes. Normal cells undergo a finite number of divisions (known as the Hayflick limit) before entering cellular senescence, but immortalized cells bypass this limitation.
- The key mechanisms of cell immortalization often involve the activation of telomerase, an enzyme that maintains telomere length. Telomeres are protective sequences at the ends of chromosomes that naturally shorten with each cell division. When telomeres become too short, cells typically stop dividing and enter senescence. Immortalized cells maintain their telomere length, allowing continuous cell division without triggering senescence.
- Several methods exist for artificial cell immortalization in laboratory settings. One common approach involves viral transformation, using viruses like Epstein-Barr virus (EBV) or Simian Virus 40 (SV40). These viruses contain genes that can override cellular checkpoints and prevent senescence. Another method involves the introduction of specific genes, such as human telomerase reverse transcriptase (hTERT), which enables continuous telomere maintenance.
- Immortalized cell lines have become invaluable tools in biological research and biotechnology. The HeLa cell line, derived from cervical cancer cells of Henrietta Lacks in 1951, is one of the most famous examples. These cells have contributed significantly to numerous scientific discoveries, including the development of the polio vaccine and understanding of cancer biology. Immortalized cells provide consistent, renewable sources of biological material for experiments.
- The process of immortalization often involves changes in cell cycle regulation and DNA damage response pathways. Key tumor suppressor genes like p53 and pRb are frequently inactivated, while oncogenes may be activated. These changes can affect cellular behavior and metabolism, making immortalized cells somewhat different from their normal counterparts. This is an important consideration when using these cells for research.
- Cell immortalization has significant implications for cancer biology. Understanding how cells become immortal has provided crucial insights into cancer development and potential therapeutic targets. Cancer cells often achieve immortalization through similar mechanisms, making the study of artificially immortalized cells valuable for cancer research.
- Despite their research value, immortalized cells also present challenges. They may accumulate genetic changes over time, potentially becoming less representative of their tissue of origin. Additionally, the immortalization process can alter cellular properties and behavior, requiring careful validation when using these cells as experimental models.
