Do Squirrels hold the Secret to Fighting Cancer?

Scientists at the University of Rochester have been investigating squirrels, and have made an interesting discovery which may have implications in the prevention or treatment of human cancers. The team has discovered a previously unknown biological mechanism which, in squirrels and certain other rodents, helps prevent the development of cancer.

Led by Professor Gorbunova of the University of Rochester, the research team has been investigating links between lifespan and body size in rodents. Rodents range in size very widely: from tiny field mice, to the capybara of Brazil which almost approach human size (albeit on four legs rather than two).

During their investigation, the team discovered that telomerase activity varies widely in various rodents, with smaller rodents having a much higher rate of telomerase activity than larger rodents.

Telomerase and Cancer

Telomerase is an enzyme with one basic function: to add nucleotide repeats to the ends of chromosomes. This is necessary because the ends of chromosomes (called telomeres) shorten as cells divide. If the telomeres become too short, they can become unstable, leading to mutations which may cause the cell to die, or may even turn a normal cell into a cancerous one.

Telomerase, therefore, has an important role in the cell cycle. However, too much telomerase activity is associated with increased cancer risk, because it allows cells to continue dividing regardless of age. Older cells may collect mutations which may lead to the development of cancer by other mechanisms. Telomerase activity is therefore a fine line, as both too much and too little can be problematic.

In humans telomeres shorten with age (and in fact, certain premature-aging disorders are associated with abnormally shortened telomeres).

The activity of telomerase has implications not only in aging, but also in cancer protection, as around 90% of human cancers have cells in which telomerase activity is greatly increased. These increased levels of telomerase are a crucial aspect of cancer cell survival: telomerase activity ensures that cancer cells can continue to divide without restraint.

The interesting aspect is that prior to this research, it had been generally assumed that any animal with a lifespan approaching that of humans would need to have a similar level of telomerase activity to provide protection against cancer.

But when it comes to rodents, this is apparently not the case.

Additional Anti-Cancer Mechanism in Rodents

Small rodents actually have a much higher level of telomerase than expected – and yet they can live relatively long lifespans without developing cancer. Some types of squirrel, for example, can live 20 years or longer.

Certain other types of rodent, including the chipmunk, chinchilla, muskrat, and naked mole-rat, all express much higher levels of telomerase than expected – levels which should increase their cancer risk significantly over their lifespans (given what is currently known about how telomerase works in humans), but which somehow do not.

And according to Professor Gorbunova, these rodents have likely developed another mechanism by which cancer cells are detected and checked. For example Gorbunova has surmised that these rodents may have cellular “monitors” which can detect and suppress inappropriate cell division, and slow down or inhibit this when necessary.

The next step is to attempt to determine what this mechanism is, how it works, and whether it has any applications for preventing or treating cancer in humans.