A journal published online on October 8th 2015 in the Journal of the American Medical Association has suggested that the low rates of cancer seen in elephants can be explained by the multiple copies of the cancer suppressor gene, TP53.
The theory is that because of the elephants size, it has 100 times as many cells as a person. Therefore, elephants should be 100 times more likely to have the disease. However analysis, published on the Journal of the American Medical Association, showed only 4.8% of elephants die from cancer compared to up to 25% of people. Humans have one copy of TP53 from each parent, and both are needed to prevent cancer development. In contrast, elephants get at least 20 copies of TP53 from each parent. To confirm the effectiveness of the cancer suppressor gene, the study compared 21 human and 8 elephant candidates. This were made up of 2 African elephants, 6 Asian elephants, 10 people with whats know as Li-Fraumeni syndrome and 11 people without. Li-Fraumeni syndrome is the monosomy of this TP53 gene. As a part of the experiment, their red blood cells were exposed to radiation. If a healthy cell is exposed to radiation, TP53 triggers apoptosis of the cell, killing it. This protective mechanism prevents cells likely to develop cancer from spreading throughout the body. As expected people with Li-Fraumeni syndrome had the least cell suicide with just 2.7 percent of their blood cells that died. In the healthy humans, 7.2 percent of the cells died, but in the elephants, 14.6 percent of the cells died, the researchers found. This relates the what we learned in class as TP53 is an example of a "loss of function gene" that can be produced during the G1 checkpoint in interphase. This can either cause the cell to be completely destroyed or slow the cell cycle down to try and resolve the problem. References: http://www.medscape.com/viewarticle/852363 http://www.bbc.co.uk/news/health-34466220 http://www.livescience.com/52432-elephants-cancer-resistance.html
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