When scientists from the University of Copenhagen tested a malaria vaccine in pregnant women, they found that it might be used to treat cancer instead. The findings are published in Cancer Cell.
Malaria parasites infecting 2 blood cells. Photo credits: Lennart Nilsson / Scanpix.
The researchers set out to develop a malaria vaccine by combining a toxin and a protein used by the malaria parasite to adhere to the placenta. They then discovered that the end result was similar to a carbohydrate found in cancer cells.
Following the astonishing “plot-twist”, scientist Ali Salanti informed cancer researcher Mads Daugaard from the University of British Columbia. The two groups then put their minds together to dig deeper. When the protein-toxin combo was added to cell cultures and in mice with cancer, it was observed that it would enter cancer cells after identifying them and kill the cells by releasing the toxin inside.
Now, what is the link between the placenta and tumours, if any, since the protein can adhere to both types of cells? One of the researchers explains the similarity.
“For decades, scientists have been searching for similarities between the growth of a placenta and a tumor. The placenta is an organ, which within a few months grows from only few cells into an organ weighing approx. two pounds, and it provides the embryo with oxygen and nourishment in a relatively foreign environment. In a manner of speaking, tumors do much the same, they grow aggressively in a relatively foreign environment,” says Ali Salanti from the immunology and microbiology department at the University of Copenhagen.
The malaria parasite seems to react to cancer cells in a similar way it does to the placenta.
“We examined the carbohydrate’s function. In the placenta, it helps ensure fast growth. Our experiments showed that it was the same in cancer tumors. We combined the malaria parasite with cancer cells and the parasite reacted to the cancer cells as if they were a placenta and attached itself,” Salanti explains.
The team now believe their findings can be used to develop a drug against cancer since the malaria protein was also found to attack over 90 % of all types of tumours; the researchers had tested thousands of samples including leukemias and brain tumours. The protein was administered to mice with 3 types of human tumours and the tumours were later found to be relatively smaller from those of a control group. As for prostate cancer, the tumours disappeared in 2 of 6 mice treated with the protein.
“It appears that the malaria protein attaches itself to the tumor without any significant attachment to other tissue. And the mice that were given doses of protein and toxin showed far higher survival rates than the untreated mice. We have seen that three doses can arrest growth in a tumor and even make it shrink,” says PhD student Thomas Mandel Clausen from the team.
On the other hand, the treatment would not be safe for pregnant women themselves.
“Expressed in popular terms, the toxin will believe that the placenta is a tumor and kill it, in exactly the same way it will believe that a tumor is a placenta,” explains Salanti.
As for other patients, the researchers are positive.
“The earliest possible test scenario is in four years time. The biggest questions are whether it’ll work in the human body, and if the human body can tolerate the doses needed without developing side effects. But we’re optimistic because the protein appears to only attach itself to a carbohydrate that is only found in the placenta and in cancer tumors in humans,” Salanti says.