Why Whales Not Developing Cancer Has Relevance10 months, 3 weeks ago
Posted on May 15, 2019, 6 p.m.
Risk of cancer increases with age and weight, yet the world’s largest mammals do not experience this correlation and they are some of the animals that are the least likely to get cancer.
Cancer begins when cells mutate abnormally and start growing and dividing uncontrollably in manners that disrupt normal functioning of their biological environments. Cancer is a leading cause of death around the globe that affects millions of people of all ages; it is also a leading cause of death in cats, dogs, and in some birds, reptiles, and fish. Recent discoveries even suggest that some dinosaurs developed cancer.
Cancers are argued to have become more widespread in the modern world due to factors such as pollution and other man made environmental changes, but many studies show that cancer occurred thousands of years ago. The earliest case of cancer documented occurred in a hominin whose remains dated back to 1.7 million years which was located in a South African cave, and evidence was found of osteosarcoma bone cancer.
Weight and age can increase risk of developing cancer: with age cells may be more susceptible to mutations which have had more time to mutate, and with weight the more cells there are that can mutate. However this does not apply evenly across all species as some animals are unlikely to develop cancer despite being long lived and very large.
Whales, porpoises, and elephants have incredibly low rate of cancer, as such researchers wonder whether their resistance to cancer could help gain better understandings to the disease and how best to fight it.
In the case of elephants, these large pachyderms have a tumor suppressing gene that allows their bodies to stop cancer from forming. Human also have this gene, but humans only have one copy whereas elephants have as many as 20 copies.
According to a study published in the journal Molecular Biology and Evolution which had permission to analyze skin samples from an adult female humpback whale which has been followed since the 1970s the answer to cancer may lie in these aquatic mammal genes.
DNA and RNA sequencing was conducting on the skin sample to assemble a genome map which was compared with information on the genetic makeup of various mammals which included 10 other cetacean species. Certain genomic loci were revealed to have evolved at a faster rate in whales than in other mammals, specifically those containing genes that regulate cell cycle, proliferation, and the process of in cell DNA repair.
Genes responsible for cell maintenance processes mutate in human cancers, but whales have many duplications of tumor suppressing genes that prevent cancer from developing and growing which sets them apart from other mammals.
"This suggests that whales are unique among mammals, in that in order to evolve their gigantic sizes, these important 'housekeeping' genes, that are evolutionarily conserved and normally prevent cancer, had to keep up in order to maintain the species' fitness. We also found that despite these cancer-related parts of whale genomes evolving faster than [in] other mammals, on average, whales have accumulated far fewer DNA mutations in their genomes over time, compared to other mammals, which suggests they have slower mutation rates.” explains Marc Tollis, Ph.D.
In more ways than one this information suggests that many species of the world have evolved on their own a way to keep cancer at bay. By understanding the mechanisms in play researchers may be able to come up with preventive strategies and anticancer therapies in the future which may be effective for humans to fight off cancer. Mapping out how different animal species develop cancer as well as antioncogenic mechanisms may allow researchers to learn how these diseases have been present all along.
"Nature is showing us that these changes to cancer genes are compatible with life. The next questions are, which of these changes is preventing cancer, and can we translate those discoveries into preventing cancer in humans?"
“Our goal is not only to get nature to inform us about better cancer therapies, but to give the public a new perspective of cancer. The fact that whales and elephants evolved to beat cancer, and that dinosaurs suffered from it as well, suggests that cancer has been a selective pressure across many millions of years of evolution, and it has always been with us. Our hope is that this may change people's relationship with the disease, which can be painful and personal. It also helps provide even better appreciation for biodiversity. In our current, sixth, mass extinction, we need all the reasons for conservation that we can get.”
The team hopes to experiment on whale cell lines in future lab work in efforts to develop prototypical cancer drugs based on these mammal’s biological self defense mechanisms.
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