Cancer happens when cell divisions go wrong and cells start multiplying uncontrollably, damaging the surrounding tissues. Induction suggests that cancer should be more common in larger animals such as whales, for example, since they require more cell divisions. However, according to this paper,
Evidence from mammals, however, suggests that the cancer risk does not correlate with body size. This observation defines “Peto’s paradox.”
Indeed, intuitively, we would expect finding whales with much less life span dying from all kinds of strange system malfunctioning. Clearly, something about the large size of these animals counteract against the higher probability of carcinogenic cell divisions. One hypothesis is:
[…] that malignant tumors are disadvantaged in larger hosts. In particular, […] natural selection acting on competing phenotypes among the cancer cell population will tend to favor aggressive “cheaters” that then grow as a tumor on their parent tumor, creating a hypertumor that damages or destroys the original neoplasm. In larger organisms, tumors need more time to reach lethal size, so hypertumors have more time to evolve. So, in large organisms, cancer may be more common and less lethal.
Cancer cells of cancer cells, nature’s feedback at work again. I’m curious to see if there’s a universal equilibrium point of cancer rate: i.e. if we plot animals’ size against the rate of lethal cancer, whether the resulting graph would be linear.
At the same time, it begs the question of the value of curing cancer. If indeed there’s a fixed relationship between organism size and rate of cancer, barring artificially introduced carcinogenic factors (nuclear meltdowns, for example), would curing cancer worth the effort?
Cancer could be nature’s way of population control, making sure that it has enough resources to support all its inhabitants. It sounds a bit meta, but the promising cancer treatments such as the <a href=”http://www.uphs.upenn.edu/news/News_Releases/2011/08/t-cells/“>Modified “Serial Killer” T-Cells</a> injects modified T-cells that multiply rapidly to kill natural cancer cells.
I Am Legend much?
It remains to be seen whether the treatment will have side effects, how the body reacts to T-cells capable of rapid divisions. For one, they’re already more susceptible to cancerous growth than the normal cells.