Is telomere shortening the answer to curing cancer?
Before I begin to try to answer or give my opinion on this question, an understanding of what telomeres are and their importance in organisms is required. Telomeres are the end-cap sections of DNA on chromosomes. Telomeres are present in all living organisms and have the same sequence of bases repeated many times. In humans this repeated sequence is TTAGGG.1 Chromosomes generally have around 10,000 base pairs in length at birth, but as cells replicate, about 100 chromosomes are lost in each replication cycle. The purpose of telomeres is to prevent the DNA in the chromosomes being damaged, with only the telomeres losing genetic material. After a certain number of replications, telomeres shorten to a critical length, when the chromosome can no longer be replicated, preventing cell replication, as well as resulting in the cell carrying out apoptosis. If enough cells in the body carry out apoptosis as a result of this, death occurs, which is one of the main reasons for death in old people.
Although this article focuses on the benefits of telomere shortening, it is useful to know why telomere extension has been seen as so positive in recent times. Telomere extension can be done through the use of telomerase. This is an enzyme which in the body increases the sequence of TTAGGG in telomeres, increasing its length, resulting in the gene expression changing to a younger phenotype, making the body function as it did when it was younger. Telomeres are in low quantities in somatic cells (most body cells), so by extending the telomeres of the chromosomes in these cells, somatic cells can divide more times, delaying apoptosis and therefore death. Telomere extension can be also done by using modified RNA, which encodes a telomere-extending protein to cells. This results in telomere length increasing by about 1000 nucleotides, which can have a huge effect on the life expectancy of populations.2 Telomere extension, by the same logic, can be used to mass-produce cells in the form of organs and more, for transplantation, destroying the sickening black market organ transplantation business in many countries. Furthermore, for people with burns which struggle to heal naturally, telomeres can increase cell replication in these areas repairing burns.
Now that we know this, we can move onto the effect of telomeres on cancer. To start, what is the relation between telomeres and cancer incidence? Cancer is one of the most common and dangerous diseases prevalent today. In 2017, more than 1.7 million people developed cancer, with 0.6 million deaths from cancer. Most ‘potential treatments’ stay in the testing phase, as either the treatment, is too expensive on a large scale, the treatment has too many side effects or is not effective enough. This means that, in hospitals, there has not been much change in the standard treatments offered to cancer patients e.g. chemotherapy, radiotherapy, surgical removal of tumour etc. Cancer occurs as mutations of DNA in cells results in uncontrolled cell division, forming either malignant or benign tumours. Benign tumours are quite harmless in contrast to their counterpart as they grow in the same part of the body and do not spread across the body (so they are not cancerous), making them easier to remove through conventional methods like surgical removal. However, malignant tumours are cancerous and are harder to remove fully as they spread quickly, through the use of the bloodstream to many different areas of the body. This makes malignant tumours very hard to control or treat by conventional methods.
This leads to the question of why tumours divide uncontrollably. I have already said that DNA mutations cause this uncontrollable cell division, but more specifically, these mutations result in telomerase being activated in large quantities in cells, extending the telomeres of chromosomes of cancer cells, resulting in cancer cells being “immortal” as they can theoretically divide forever because of the high production of telomerase. Doctors at Radboud University Medical Center, Holland, found that a large proportion of people are higher risk of cancer had very long telomeres due to a mutation in the TINF2 gene which controls the TIN2 protein, the proteins responsible for telomere lengths. This mutation in the gene has its cancer-promoting effects, mainly in the early stages of life in the womb. As a result, when gene editing in humans becomes more effective and accepted, cancer can be prevented in people with the TINF2 gene mutation, by changing this gene back to how it should be through the use of CRISPR in IVF3. It should be noted that these telomeres in people with the gene mutation, were extremely long and does not mean that telomere extension in the future will be dangerous, just that telomere extension should not be too extreme as that can lead to cancer.
Therefore, to conclude, telomere extension may be the key to increasing life expectancy in humans, but targeted telomere shortening in those of higher risk of cancer, through the editing of genes in IVF, will most likely be the key way of preventing and treating cancer in the future.
- Blau, H., 2015. Telomere Extension Turns Back Aging Clock In Cultured Human Cells, Study Finds. [online] Stanford Medicine. Available at: <https://med.stanford.edu/news/all-news/2015/01/telomere-extension-turns-back-aging-clock-in-cultured-cells.html> [Accessed 28 December 2020].
- T.A. Sciences®. n.d. Telomerase Enzyme | Telomere Shortening | TA 65 Supplement. [online] Available at: <https://www.tasciences.com/telomeres-and-cellular-aging.html> [Accessed 28 December 2020].
- Watts, E., 2020. Could Telomere Shortening Protect Against Cancer?. [online] Medicalnewstoday.com. Available at: <https://www.medicalnewstoday.com/articles/could-telomere-shortening-protect-against-cancer> [Accessed 28 December 2020].