Friday January 17 2014
Blind mole rats could prove useful in cancer research
"A cure for all cancers is on the way" was the frankly bizarre claim on the front page of the Daily Express, not least because the study it was "reporting" on involved blind mole rats, not humans.
Admittedly, the blind mole rat (Spalax) is an intriguing creature worthy of study. It spends its life underground, is tolerant of very low oxygen levels, has a lifespan of more than 20 years, and, most importantly, doesn't seem to develop cancer.
In this study researchers gave blind mole rats potent cancer-causing chemicals either through injections or applied directly to the skin, but the animals didn't develop cancer.
Remarkably, connective tissue cells (fibroblasts) taken from the blind mole rat even prevented the growth of human cancer cells when they were grown together in the laboratory.
The blind mole rat clearly has some unique anti-cancer properties. Some suggest these are related to how it survives in a low oxygen environment.
Similar studies in a closely related species, the naked mole rat, have demonstrated similar cancer protection properties. As yet, the biology of these anti-cancer properties has not been uncovered and we do not know whether they could be used to treat human cancers.
The claims made in the press that a universal cure for human cancers is "on the way" are entirely unsupported by the results of this study, however.
Where did the story come from?
The study was carried out by researchers from the University of Haifa, Israel, and was funded by the Israel Cancer Association, the Caesarea Edmond Benjamin de Rothschild Foundation Institute for Interdisciplinary Science, the Ministry of Immigration Absorption of Israel, and the Council for Higher Education of Israel Planning and Budgeting Committee.
It was published in the peer-reviewed scientific journal BMC Biology.
The Daily Express' coverage of this study rather unfairly offered false hope to cancer sufferers, suggesting that "a cure for ALL cancers is on the way", a statement that certainly cannot be made given the current stage of research.
This study has only confirmed the unique abilities of the mole rat to resist cancer – there are no current implications for human cancer treatment.
The Mail Online's reporting of the study is more restrained, but it still takes the researchers' statement that this is a "breakthrough" study at face value, without considering that this research is still in its very early stages.
Nobody knows how long it will take to uncover the secrets of the mole rat, and still fewer whether this understanding will eventually help humans.
What kind of research was this?
This was animal research examining the resistance subterranean blind mole rats (Spalax) have to cancers. Blind mole rats are one of a unique group of animals that spend their lives underground, are tolerant of very low oxygen levels (down to only 3% concentration – levels that would kill a human), have a long lifespan of more than 20 years, which is exceptional for a small rodent, and show no clear signs of ageing or age-related diseases.
Unlike other small rodents, mole rats have never been observed to get cancer. Researchers say that in 50 years of examining thousands of mole rats, they have never observed a single spontaneously growing cancer.
This research carried out various experiments with the aim of seeing whether:
- the blind mole rat is resistant to chemically-induced cancer growth
- fibroblasts (connective tissue cells that play a role in wound healing) from the blind mole rat demonstrate cancer-killing properties
What did the research involve?
The researchers compared the anti-cancer properties of a group of mole rats with a group of rats and mice.
The animals were first treated with two potent cancer-causing chemicals – DMBA/TPA (7,12-Dimethylbenz(a)anthracene/12-O-tetradecanoylphorbol-13-acetate) and 3MCA (3-Methylcholantrene).
Eight mole rats and six mice were treated with DMBA/TPA. A solution of this chemical was applied to the shaved backs of the animals to try to induce skin cancer.
3MCA was given by injection to 12 mole rats, six mice and six rats. In previous studies, rodents given this chemical have developed connective tissue tumours called fibrosarcomas.
The researchers wanted to look at the action of fibroblast cells, so they extracted cells from the arms and lungs of mole rats, mice and rats. In the laboratory, the fibroblasts were cultured with human-derived cancer cells from human breast and liver tissue.
What were the basic results?
After skin treatment with DMBA/TPA, none of the mole rats developed tumours. They had signs of skin damage and ulceration where the chemicals had been applied, but the wounds healed within seven to nine weeks, and no later skin tumours were observed up to six months.
Meanwhile, all the mice developed blisters within the skin that turned into cancerous tumours within two to three months.
After treatment with 3MCA, fibrosarcomas developed as expected within two to three months in mice, and within four to six months in rats.
In the blind mole rats, 2 out of 12 showed signs of proliferation of fibroblast cells, but no cancers developed. However, one of the older blind mole rats did later develop a cancer 18 months after treatment. All others remained healthy up to 30 months after treatment.
In the laboratory, isolated fibroblasts taken from the blind mole rats prevented growth of human cancer cells, either directly or by releasing soluble factors into the culture medium.
The researchers observed decreased viability of the cancer cells, reduced colony sizes, and disturbed cell cycle progression. Meanwhile, fibroblasts from the rats and mice had no effect on the human cancer cells.
They similarly found that cells from another subterranean mammal with similar characteristics – the naked mole rat (Heterocephalus glaber) – also demonstrated anti-cancer activity.
How did the researchers interpret the results?
The researchers concluded that, "This report provides pioneering evidence that Spalax [the blind mole rat] is not only resistant to spontaneous cancer, but also to experimentally induced cancer, and shows the unique ability of Spalax fibroblasts to inhibit growth and kill cancer cells, but not normal cells, either through direct fibroblast-cancer cell interaction or via soluble factors."
They continue that, "Obviously, along with adaptation to hypoxia [low oxygen levels], Spalax has evolved efficient anti-cancer mechanisms yet to be elucidated. Exploring the molecular mechanisms allowing Spalax to survive in extreme environments and to escape cancer, as well as to kill [its own and other] cancer cells, may hold the key for understanding the molecular nature of host resistance to cancer and identify new anti-cancer strategies for treating humans."
This research has demonstrated the unique abilities of the blind mole rat to resist cancer, even when directly given potent cancer-causing chemicals.
In the laboratory, the researchers also demonstrated how connective tissue cells called fibroblasts taken from the animal seem to play an important role in this cancer resistance. These cells prevented the growth of human cancer cells when the two types of cells were grown together in the laboratory.
A similar study in a closely related species – the naked mole rat – has also demonstrated similar cancer protection.
Scientists have been studying the mole rat for many years. However, the biological underpinnings of the cancer resistance remain unclear. This serves as a reminder that these developments take time and persistence, and that the road to scientific breakthrough is typically long and incremental.
This is a useful piece of research that could lead to potentially exciting new avenues of research. It is true that, as the researchers say, this is "pioneering" work, but it is a little too early to suggest that their findings present a "genuine breakthrough".
Many discoveries in animal studies fail to show similar effects in humans, so even if the anti-cancer properties of the mole rat are discovered, there is no guarantee they will be useful or applicable to humans.
Nonetheless, there remains optimism that understanding the anti-cancer mechanisms of mole rats may one day help inform further cancer treatments for humans, but a lot more research – and probably a significant amount of time – is needed before this can be considered.
For now, the best ways to try to reduce your risk of cancer are through regular exercise, following a healthy diet, avoiding smoking and moderating your alcohol consumption. Read more about cancer prevention.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.