Elephants are large animals with many more cells than humans and therefore should experience DNA damage as a precursor to cancer at a higher rate compared to humans. As a long-living animals elephant cells also undergo many cycles of cell division throughout their lives which could potentially lead to mutations that could lead to cancer. Yet cancer does not seem to be an issue for these lovable giants. This lack of correlation between size and cancer in large animals like elephants and whales is called Peto’s paradox (after the cancer researcher Sir Richard Peto).
Until recently little was known about how elephants fended off cancer. A paper published in the Journal of American Medical Association begins to shed light on that mystery. Dr. Joshua Schiffman from the University of Utah and his colleagues determined that elephants carry 40 copies of the gene for tumor protein p53. Humans carry two copies of the gene for this important tumor-fighting protein. TP53 binds directly to damaged DNA (damaged by toxins, UV radiation, or other known cancer-causing culprits) in the cell and determines if it can be repaired or not. If the DNA can be repaired the TP53 protein activates the repair process. If the DNA cannot be repaired the TP53 protein signals programed cell death or apoptosis. In elephants TP53 proteins tend to veer toward apoptosis which stops any possibility of tumor growth due to uncontrolled cell division.
There is hope that with these new findings we can come closer to reducing cancer rates in humans, particularly for those who have a mutated copy of the TP53 gene. Individuals with mutated copies of the TP53 gene are diagnosed with Li-Fraumeni Syndrome and have a higher risk of developing certain cancers (breast cancer and leukemia among other types).
No wonder elephants are considered symbols of good luck.
About this Illustration: An acrylic painting with chromosomes at the bottom (as vegetation) of the painting, followed by abstract TP53 in silver as the horizon, and above are cells (as clouds) undergoing apoptosis. The elephant is obvious…
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