Understanding how this gene evolved and works in elephants may help researchers develop ways to treat human cancer patients, the researchers said.
In the study, the researchers focused on the so-called “guardian of the genome” — a gene called TP53. Normally, this gene encodes a protein that suppresses tumors. In the majority of human cancers, this gene is mutated, leading to increased cell reproduction (a hallmark of cancer) and genomic instability (mutations in the genome), the researchers said.
Humans inherit one copy of TP53 from each parent, and both are needed to prevent cancer development. People who inherit one copy that doesn’t work may develop a condition called Li-Fraumeni syndrome, which gives them a greater than 90 percent risk of getting cancer during their lifetime, according to the study, published online today (Oct. 8) in the journal JAMA.
In contrast, elephants get at least 20 copies of TP53 from each parent, which may explain their low rate of cancer, the researchers said.
“Compared with other mammalian species, elephants appeared to have a lower-than-expected rate of cancer, potentially related to multiple copies of TP53,” they said in the study. “These findings, if replicated, could represent an evolutionary-based approach for understanding mechanisms related to cancer suppression.”
The researchers began their experiments by comparing cancer rates in 36 mammals, including elephants. By looking at 14 years of data collected by the San Diego Zoo during necropsies (the animal version of an autopsy), they found that animals’ cancer risk did not increase with body size or with long life spans.
This finding was surprising, because having a greater number of body cells, and a higher number of cell divisions, usually increases the chance of accumulating the mutations that can lead to cancer, according to the researchers, who were led by Lisa Abegglen, an oncology researcher at the University of Utah School of Medicine in Salt Lake City.