I was kind of surprised to see yet another article confirming (and reaffirming) the correlation between telomere length and cancer mortality. It seems like this has been studied ad nauseum but an article published in JAMA on the 10th July focused on just that.

A little background (for the non-science nerds out there): telomeres are small regions of DNA that protect the end of your chromosomes (these hold your genetic information). A good way of thinking about a telomere is to compare it to that little bit of plastic at the tip of your shoelaces: it kind of just holds everything together and keeps the whole lot from unraveling.

In our genes, telomeres have the important role during replication of our DNA to act as a buffer so that we don’t lose any crucial genetic information. Each time our DNA replicates, a little bit of the genetic information is lost at the end of our chromosomes, but that’s ok, that’s what the telomeres are there for. After replication, an enzyme called telomerase helps rebuild the telomeres.

But, they also serve another important purpose: the telomeres, despite being replenished, shorten after each replication and at one point, when the telomeres are too short, the lifespan of that particular cell is over our body takes care of destroying it. Kind of like spring cleaning. (In fact, this is called cellular senescence, and it basically means the cell has lost the ability to continue dividing.)

Unfortunately, cancer cells have a “defective” overactive telomerase (the enzyme that rebuilds the telomeres after each replication) and this allows for repeated, plentiful cell divisions even after the cell shouldn’t be dividing anymore. That’s where the term “immortal” [cancer] cell comes from. You can read more about that here, Rebecca Skloot wrote a book about the HeLa cell line, a cell line that was harvested in 1951 and continues to be used for research today. One prominent discovery, thanks to the HeLa cell line, was the polio vaccine.

What I found most interesting about this particular article was that it claims that cancers associated with a high fatality rate, like lung cancer, head and neck tumours, bladder cancer, Non-Hodgkin’s Lymphoma and so on showed a more prominent relationship with telomere length while “less aggressive” cancers (colorectal, breast, etc) did not show as strong of an association. And, measuring the length of telomeres in current cancer patients could be used as a new measure of survival.

Oh — and this particularly paper didn’t mention this little fact, but what carcinogen has shown an increased association with shortened telomeres? Nicotine. Bad, bad, bad.

Citation: Willeit Peter, Willeit Johann, Mayr Agnes, Weger Siegfried, et al. Telomere Length and Risk of Incident Cancer and Cancer Mortality JAMA 2010:304(1):69-75