The term “immortal nature” in the context of cell biology refers to the ability of certain cells to proliferate indefinitely, bypassing the normal cellular aging process known as senescence. Most normal cells have a limited capacity to divide and will eventually stop growing due to various factors, such as DNA damage, oxidative stress, or the shortening of telomeres, which are protective caps at the ends of chromosomes.
Immortal cells, on the other hand, have acquired genetic or epigenetic changes that enable them to overcome these limitations, allowing them to continue dividing without restrictions. Immortalized cell lines are valuable tools for biomedical research because they can be maintained and propagated in the laboratory for extended periods, providing a consistent and renewable source of cells for various experiments.
Immortalization can occur naturally, as in the case of some cancer cells, or it can be artificially induced in the laboratory. Cancer cells often become immortal due to genetic mutations and alterations in signaling pathways that control cell growth and division. For example, the activation of oncogenes or the inactivation of tumor suppressor genes can lead to uncontrolled cell proliferation and immortality. Additionally, the activation of the enzyme telomerase can prevent the shortening of telomeres, allowing cells to bypass replicative senescence and continue dividing indefinitely.
In the laboratory, immortalization can be achieved by introducing specific genes or viral components into primary cells, such as the simian virus 40 (SV40) large T antigen or the human papillomavirus (HPV) E6 and E7 proteins, which can interfere with cellular growth control mechanisms and promote cell proliferation.
While immortalized cell lines are advantageous for research purposes, their continuous growth and altered genetic makeup can result in differences from the original tissue or cell type, which may limit the relevance of some findings to normal physiology or disease processes. Additionally, the immortal nature of some cell lines, such as HeLa cells, can lead to contamination and cross-contamination issues in the laboratory, as these cells can easily overgrow and outcompete other cell types if proper cell culture practices are not followed.