Darwin was wrong and the fittest mutations may fail when it comes to tumour cells, Chinese scientists say
Team makes bold claim that diverse range of mutations in cancer cells compete among themselves rather than produce dominant winners that can be eradicated as a means of tackling the disease.
Charles Darwin’s theory of evolution by natural selection does not work at a cellular level, a finding that could profoundly influence the battle to find a cure for cancer, according to joint study by a team of researchers from the University of Chicago and the Chinese Academy of Sciences.
The results were published in a paper in the Proceedings of the National Academy of Sciences.
Darwin made a compelling argument for how only the fittest survive and thrive, and this was long believed to be the case with cancerous cells in the human body.
Many in the scientific community thought that stronger, mutant cells breed at an out-of-control rate - much like pesky rabbits in the Australian outback - because they are more able to adapt to their environment, resulting in tumours.
This led to the widespread belief that the key to treating cancer lies in targeting and eliminating these “super cells” using drugs or other methods.
But this may prove far from the mark.
The latest study, which was led by Professor Chung-I Wu at the University of Chicago Medical Centre, found that tumour cells carrying various mutations compete fiercely with one another, rather than any one proving dominant.
Instead of solving the problem by removing the “fittest” mutant cells, doing so could actually upset the delicate balance of power that goes on inside a tumour, they said.
Such treatment could trigger the explosive growth of other cancerous cells, which would then spread to other parts of a patient’s body, according to Wu’s research.
But the study was rebuffed by other scientists.
“It is just another claim to challenge Darwin’s theory, and it is likely to fail,” said Professor Qin Zhihai, principal investigator of tumour microenvironment and tumour immunity at the Institute of Biophysics in Beijing.
“Darwin’s theory is one of the best-tested golden rules in natural science. It explains the phenomenon of life at all levels, from humankind’s position in the universe to the fate of cells,” he added.
But just as Einstein’s grand theory of everything failed to elide with the microscopic world of quantum mechanics, Darwin’s famous theory faced challenges at a molecular level.
According to the English naturalist who helped shape the way we view ourselves, organisms that are better adapted to their environment thrive and produce more offspring.
But in the 1960s, some scientists including Japanese biologist Kimura Motoo observed that the development of life at much smaller - even cellular - scale was driven by random mutations and genetic drift that were neither beneficial nor detrimental to the host organism.
They labelled this phenomenon “neutral evolution”. According to this theory, every organism has the same chance of survival, and those who make it may not be the fittest, just the luckiest.
These counter-Darwinian theories raised heckles and sparked much debate among biologists, especially with the rapid development of molecular science starting in the 1980s.
The latest study has made the issue “suddenly medically relevant,” Wu said in a press release.
Wu, together with a team led by Professor Lu Xuemei at the Beijing Institute of Genomics, carried out the most rigorous genetic sequencing ever on a single tumour.
They examined an ordinary tumour removed from a patient’s liver. Using the latest technology and hardware, they sequenced or genotyped nearly 300 regions in the tumour to search for genetic abnormalities.
They were shocked by the number of mutations they found in the tumor, which measured about 3.5 centimetres in diameter, making it smaller than a ping-pong ball. It contained over a billion living cells, among which were found more than 100 million distinct mutations.
The huge amount of genetic diversity in such cells may explain why many cancer treatments fail.
“With 100 million mutations, and each one capable of altering a protein in some way, a significant minority of tumour cells are still very likely to survive, even after aggressive treatment,” Wu said.
Moreover, such heavy-handed treatment could give them a boost, the team said.
“This could potentially change how we think about tumour growth and [how these] spread, but the direct clinical implications of this study may not be obvious on the surface,” said medical oncologist Daniel Catenacci, an assistant professor of medicine at the University of Chicago. He co-authored the study.
Meanwhile, Qin said evidence showed that some mutations were in fact more deadly than others, adding that cancer may even form a part of Darwin’s theory by weeding out the weaker of the species.