Introduction
The majority of researches on cancer centre their studies on treatment rather than prevention, and this often leads to the repetition of tumors that are difficult to treat. But there is an increase in the attention to cancer prevention so as to avoid this scenario altogether.
Theoretically, if every cell has some chance of becoming cancerous, the threat of developing cancer should expand with both the number of cells and the lifespan of an organism. Nonetheless, large animals(like elephants and whales) do not get more cancers as humans do and that’s what Peto’s Paradox is all about. The absence of correlation between body size, lifespan and cancer risk is known as Peto’s Paradox.
The evolution of multicellular organisms required the suppression of cancer. They had two options: either convert into a lump of cancer or evolve to prevent it.
Hypothesis to resolve Peto’s Paradox
• More Tumour Suppressor gene
Selective pressure might have induced more tumor suppressor genes in large and long lived animals(1). More amount of Tumour suppressor gene can supress cancer in large animals. More tumour suppressor gene means the body requires more amount of mutations to lead to a tumour(2).
• Fewer proto-oncogenes
Some scientists also suggest the theory for fewer proto-oncogenes in the genome of larger and long lived animals(2). Fewer the proto-oncogenes, lesser is the probability of cell resulting in cancer. But this ,ofcourse, comes along with other complications because proto-oncogenes have other functions as well.
• More efficient immune systems
Immune system in opposition to virus-associated cancers might account for some differences observed in cancer rates within individuals(2). Scientists suggest that larger animals might have a more sensitive immune Surveillance than smaller animals.
• More sensitive or efficient apoptotic process
Scientists also suggest that there might be a difference of apoptotic propensity of cells in larger and smaller animals(2). Their bodies could be more sensitive to DNA damage or the activation of an oncogene thereby reaulting in a decreasing cancer risk.
• Formation of Hypertumours
This is another theory given by a scientist nameds Nagy et al. that the whales do produce a lot of tumours but they have something known as a tumour parasite, also known as hypertumour, that helps them to regress the tumour(2). But there is yet no prove for this theory.
This being said, the study of cancer resistance in animals needs a evolutionary perspective(1). Although it is also suggested that these cancer prevention methods would have come along with some other complications(2).
Future Prospect
It is true that earlier the studies mainly focused of the treatment of cancer but things have been changing lately. Scientists are also getting into the very core of cancer, it’s origin, organism’s evolutionary ways to prevent it and ways to prevent it at the first place. These fundamental scientific discoveries could lead to huge advancement in their therapies and treatments.
According to World Health Organisation, around 20% of cancers are caused by infections. It was found that if there is continuous infection ,in a particular area, for an extended duration of time, it could lead to a boost in the mutation rate which could ultimately lead to cancer. Regardless, since the infection is preventable, then so is cancer(3).
Peto’s paradox also showed that certain species are better at deterring cancer than the others. Considering their defences in cancer, it also might be of vast use in combat with cancer in humans as well.
Reference
1) DeGregori J. Evolved tumor suppression: why are we so good at not getting cancer? Cancer Res. 2011;71:3739–3744. doi: 10.1158/0008-5472.CAN-11-0342.
2) Caulin AF, Maley CC. Peto’s Paradox: evolution’s prescription for cancer prevention. Trends Ecol Evol. 2011;26:175–82. doi: 10.1016/j.tree.2011.01.002.
3) Thomas F, Fisher D, Fort P, Marie J-P, Daoust S, Roche B, et al. Applying ecological and evolutionary theory to cancer: a long and winding road. Evol Appl. 2013;6:1–10.
Aesthete 