Cancer-related genes allow deer to grow a new pair of antlers every year but the animals rarely die of the disease thanks to tumour-suppressing genes that keep the aggressive cells in check, an international study led by Chinese researchers has found.
The researchers also found that while some deer might have tumours all over their body, the growths do almost no harm and disappear with time.
The findings, published in the latest issue of the journal Science, could open up new directions in organ regeneration and cancer treatments, according to the researchers.
Wang Wen, the study's lead author and professor of biology at Northwestern Polytechnical University in Xian, Shaanxi province, said deer were unique for their ability to regrow antlers - complex organs of bones, blood vessels, nerves, muscle, skin and even fur, known as velvet.
"Deer can completely regenerate an organ. No other mammal has that ability," Wang said.
Antlers grow rapidly - up to 2.5cm (one inch) a day in the case of red deer - and Wang's team identified nine genes involved in antler cell growth.
All of those genes were oncogenes, or related to cancer, with some accelerating cell proliferation and differentiation, some are responsible for tumour formation in bones and skin, and some prolonging the cancer cells' life.
The team also identified another 19 genes that act as tumour suppressors, stopping the antler growth going out of control, according to the Science paper.
Breast cancer breakthrough uses molecular data to predict whether tumours will come backThe genes work together to allow the antler cells to thrive without developing into cancer in other parts of the body.
"To the deer, [cancer] is not a disease - it's a part of life," Wang said.
The researchers said the genes might have been the product of random mutation, probably as early as 20 million years ago, giving rise to a group of stags with bigger antlers, according to the researchers.
The larger appendages might have been more attractive to female deer, despite the risk of cancerous tumours. Over time, natural selection favoured deer with stronger resistance to the tumours, according to the researchers.
In a commentary article in the same issue of Science, Stanford University professor Yunzhi Peter Yang and Dai Fei Elmer Ker, assistant professor at Chinese University of Hong Kong's Institute for Tissue Engineering and Regenerative Medicine, said the discovery would help scientists find ways to regrow damaged or missing organs and develop new drugs to battle cancer.
"Studies of deer antlers offer attractive approaches for tissue engineering and regenerative medicine. For instance, deer antlers have inspired a commercially promising prosthesis for amputees," they wrote.
They said the animals' ability to grow large amounts of "innervated bone with low tumour and infection incidence" could be useful in treating skeletal defects, regenerating nerves, and possibly even limiting cancer growth.
The study is part of the Ruminant Genome Project, a research programme led by Chinese scientists to sequence and analyse the genes of all grazing mammal families.
Other discoveries from the project include a big decline in the ruminant population between 100,000 and 50,000 years ago, which coincides with the expansion of the human population as people left Africa. The decline was recorded in numerous genetic code variants and provided new evidence on the impact of human activities on the global ecological system.
The researchers also found the genes that allow reindeer to thrive in Arctic environments.
These genes not only allow the animal to adapt to extreme cold but help maintain body functions in the absence of sunlight.
These discoveries will lead to new drugs or treatments for many human diseases such as insomnia and bone loss, according to the scientists.
- South China Morning Post