But Gorbunova and colleagues showed that it was not life expectancy, but body mass that regulated the expression of telomerase. Simply having more cells increases the likelihood that one will become cancerous. We humans, as large animals, would likely develop cancer much more often and much earlier if we didn't suppress our telomerase.
While the findings were a surprise, they revealed another question: What about small animals like the common grey squirrel that live for 24 years or more? With telomerase fully active over such a long period, why isn't cancer rampant in these creatures?
Gorbunova found that the squirrel, naked mole-rat, chipmunk, muskrat, and chinchilla express high levels of telomerase, which would be expected to increase their cancer risk over their long lifetimes. But these species have developed a mechanism to counteract the high telomerase activity and remain cancer free for the duration of their lifespans.
"Squirrels know a cure for cancer," says Gorbunova. "Short-lived small species display continuous rapid proliferation of their cells, but these long-lived rodents have somehow found a way to slow down that proliferation when they need to."
Gorbunova thinks that squirrels and similar rodents have evolved a strict monitoring function within their cells that may be able to sense appropriate and inappropriate cell divisioni.e., healthy reproduction and runaway cancerous reproductionand slow or inhibit the division if necessary.
Gorbunova is now looking to isolate and understand this mechanism with the hope that it may be applicable to help human cells thwart the onset of tumor growth.
|Contact: Jonathan Sherwood|
University of Rochester