Both long and short telomeres are associated with increased telomere length, but how meaningful is this link?
Telomere length is a significant hallmark of the aging process, whether simply a byproduct of other processes ongoing during the aging process or a cause in itself. Given that many cancers do indeed upregulate the enzyme telomerase to extend their telomeres, many researchers are concerned there is a link between cancer and telomere length.
A large research project involving data from 28,000 Chinese people enrolled in the Singapore Chinese Health Study has revealed that the group with the longest telomeres had a 33% larger risk of developing cancer than the group with short telomeres. This figure reveals that to a certain extent, telomere shortening may offer a slight protective edge as we get older. Pancreatic cancer risk was most affected by telomere length, with those with the highest one-fifth for telomere length having an almost 2.6 times higher risk of developing pancreatic cancer compared to those in the lowest one-fifth for telomere length.
However, overall cancer risk was highest in those with the longest and shortest telomeres, with significantly increased risk of a number of cancer including stomach, bladder and leukaemia.
"Telomeres and cancer clearly have a complex relationship. Our hope is that by understanding this relationship, we may be able to predict which people are most likely to develop certain cancers so they can take preventive measures and perhaps be screened more often, as well as develop therapies to help our DNA keep or return its telomeres to a healthy length"
What does this really tell us?
As extending telomeres is a prospective rejuvenation strategy, it's important for us to gauge how important telomere length is when it comes to cancer. Upon further analysis and rumination this data reveals what might be expected to an extent. We know that short telomeres can in some instances lead genetically unstable cells to enter growth arrest or commit suicide. We also know that short telomeres in itself makes chromosomal DNA unstable and vulnerable to mutation, while also leading to the creation of senescent cells; raising inflammation and in turn potentially driving cancer risk in some cases. Overly long telomeres on the other hand may be a marker of unusual goings on, and may make newly formed cancerous populations more stable for a time - enabling them to grow more.
What can we take away from this? Well, essentially having telomeres at a healthy length was the best option for reducing cancer risk. This means that avoiding short telomeres is still very important, and that long telomeres in themselves are probably not the biggest concern here. If they are extended alone, with no other regenerative strategy, it may not be a good thing. But we should remember that children and young adults have relatively long telomeres and have extremely low cancer risk, so telomere length in itself probably doesn't cause cancer - it merely helps it along when other damaging processes are going on or cells have already undergone several mutations.
Cancer isn't everything
While cancer is a terrifying disease, it's far from the only cause of mortality. Short telomeres have been associated with a whole plethora of other diseases, so increasing cancer risk slightly may be a trade off that can be offset by more regular and comprehensive cancer testing for example. Older individuals will inevitably have cells with more mutations, but this shouldn't put us off bold rejuvenation strategies. Ensuring a healthy immune system, lowering inflammation and implementing better cancer monitoring and prevention strategies for example, could ameliorate cancer risk to a great extent.
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