The apparent parallels between aggressive tumor development and the way a placenta grows inside a pregnant woman have intrigued cancer researchers for years. Evolving from only a small number of cells into several-pound organ in the space of a few months, scientists have long suspected that the placenta could hold clues to understanding and ultimately beating cancer. Now the ongoing search for a malaria vaccine has inadvertently uncovered one of its more promising secrets that holds potential for the development of a treatment for the deadly disease.

Scientists from the University of Copenhagen happened upon their discovery when testing a vaccine against malaria for pregnant women, revealing that the carbohydrate the malaria parasite attaches itself to in the placenta is identical to one found in cancer cells that drives their growth. The scientists then took to the lab to recreate the protein that the malaria parasite uses to latch onto the placenta, and then mixed it with a toxin.

This forms a deadly combination for tumors, as the addition of the toxin sees the protein drawn toward the cancer cells. Here it attaches itself and is absorbed to release the toxin inside and bring about cell death.

"We examined the carbohydrate’s function," says Ali Salanti from the Faculty of Medical Health and Science at the University of Copenhagen. "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 collaborated with scientists from Canada's University of British Columbia as part of the research and the two groups proceeded to test thousands of samples of cancer. The results indicated that the malaria protein will attack more than 90 percent of all tumor types.

The technique was observed in both cell cultures and in mice. The researchers found that in mice with non-Hodgkin's lymphoma, the tumors of treated mice shrunk to about a quarter the size of those that went untreated. Tumors also disappeared in two of six mice with prostate cancer one month after their first dose. Five out of six treated mice with metastatic bone cancer were alive after almost eight weeks, while none of the control group survived.

Armed with its promising results, the researchers are now eyeing human trials, which they say are at least four years away. The approach would be unsuitable for pregnant women, however, because if administered the protein would attach itself to the placenta as normal and the toxin would kill it, in much the same way it mistakes the tumor for the placenta in other subjects.

The research is published in the journal Cancer Cell.