(3-D cancer cells; Image courtesy of Vivek Nandakumar, Center for Biosignatures Discovery Automation, Biodesign Institute, Arizona State University)
Cancerous tumors are parasitic organisms, according to a new paper in the journal Cell Cycle that argues cancers are newly evolving species.
Each cancer is a novel species that, like other parasites, depends on its host for food but otherwise operates independently and often to the detriment of its host, according to project leader Peter Duesberg.
Duesberg, a molecular and cell biology professor at the University of California, Berkeley, and his colleagues believe that carcinogenesis—the generation of cancer—is just another form of speciation, the evolution of new species.
“Cancer is comparable to a bacterial level of complexity, but still autonomous, that is, it doesn’t depend on other cells for survival; it doesn’t follow orders like other cells in the body, and it can grow where, when and how it likes,” said Duesberg in a UC Berkeley press release. “That’s what species are all about…Once a cell has crossed that barrier of autonomy, it’s a new species."
The key to this new theory is that he and his team negate the widely held view that tumors begin when a handful of mutated genes send a cell into uncontrolled growth. Instead, they argue that carcinogenesis is initiated by a disruption of the chromosomes, which leads to duplicates, deletions, breaks and other chromosomal damage that alter the balance of tens of thousands of genes. The result is a cell with totally new traits – that is, a new phenotype representing a unique species.
The idea is already gaining support from other experts. Mark Vincent, a medical oncologist at the London Regional Cancer Program and University of Western Ontario, said, "I think Duesberg is correct by criticizing mutation theory, which sustains a billion-dollar drug industry focused on blocking these mutations. Yet very, very few cancers have been cured by targeted drug therapy, and even if a drug helps a patient survive six or nine more months, cancer cells often find a way around it.”
Recently I interviewed Tak Mak, one of the world's leading cancer researchers, and he too expressed frustration over the billion-dollar drug industry that seems to employ many, and yet results in so few effective treatments.
(Breast cancer cells (stained) from a patient's bone marrow; Credit: Washington University School of Medicine)
Duesberg and others hope the new, or revived, way of looking at cancer might yield insights into its growth and spread, leading to better therapies or drug targets. ("Revived" since evolutionary biologist Julian Huxley wrote in 1956 that “Once the neoplastic process has crossed the threshold of autonomy, the resultant tumor can be logically regarded as a new biologic species ….” Other researchers since Huxley have proposed that cancer is more like a parasite than a disease.)
Because the disrupted chromosomes of newly evolved cancers are visible in a microscope, it may be possible to detect cancers earlier. Already, Pap smears rely on changes in the shapes of cervical cells as an indication of chromosomal problems that could lead to cervical cancer.
Cancer should be beatable. As Vincent points out, cancers are likely operating right at the edge of survivability, maintaining genomic flexibility while retaining the ability to divide forever. Driving them to evolve even faster, he said, "might push them over the edge."