Patients may be able to keep cancerous tumors in check for their whole lives, according to findings by a Washington University School of Medicine team of researchers.
While doctors have long known that cancer can stay dormant for years before coming out of remission, they did not fully understand what made this possible.
“We’ve been interested for a while in answering the question that has been controversial for a hundred years,” said Robert Schreiber, professor by pathology and immunology and leader of the research team. “Can the immune system see a developing cancer?”
Schreiber and his team showed that when disrupting the immune systems in cancerous mice, the cancer was more likely to come out of remission when the immune systems were disrupted.
This line of study first started in the 1970s when two researchers came up with the theory of immuno-surveillance, which refers to the immune system’s capability of recognizing cells as soon as they become cancerous and killing them.
The theory was wildly popular, but disappeared after a failed experiment.
Where that experiment failed, however, another one conducted 12 years ago by Schreiber and University M.D.-Ph.D. students succeeded.
The 1970s experiment compared tumor emergence in mice with normal immune systems to tumor emergence in mice whose systems had been depleted. However, the mice’s immune systems could not be totally destroyed at the time, due to technological restraints.
The research done 12 years ago was repeated recently with the mice with destroyed immune systems. Ultimately, these immunodeficient mice did produce more tumors.
A large problem remained in the research, however. The research failed to prove the theory of equilibrium, that is, the theory that the immune system keeps cancer dormant.
Schreiber’s most recent research, published in Nature, argues that this equilibrium can be attributed at least in part to the immune system.
He exposed two groups of mice to carcinogens such that 20 percent of each group developed detectable cancer.
He then took the remaining 80 percent of each group, wiping out the immune systems of one set and leaving the control set unharmed. The results showed that the latter group had a significantly higher rate of tumor emergence.
While the research was only conducted on mice and with one form of cancer, Schreiber hopes it will stimulate future research across the globe. He also says his current research offers two important ideas.
“Currently, we use immunotherapy as a mechanism to cure cancer,” said Schreiber. “Perhaps new work can be done to drive it into a dormant state if it can’t be eliminated completely, making it chronic but controllable.”
Secondly, Schreiber hopes it will change the method with which oncologists classify a substance as carcinogenic. His research shows that some substances, which did not initially appear to cause cancer, may indeed cause cancer-but only after a certain span of time after exposure.
Possible carcinogens, he said, should be tested by his method of disrupting the immune systems in mice to see whether tumors ultimately surface.