Unique link found between mad cow disease and cancer
Angela Mulholland, CTV.ca News Staff
Published Monday, August 2, 2010 4:05PM EDT
Researchers led by University of British Columbia researcher Neil Cashman say they've made a surprise find about human cancer and brain-wasting diseases in animals that could pave the way for vaccines to halt all the diseases.
Cashman, a neurologist and researcher, was working on therapies for preventing transmissible spongiform encephalopathies, a group of animal brain-wasting diseases that include BSE in cows, scrapie in sheep, and chronic wasting disease in deer and other cervids.
Though the illnesses each affect different animals they are all caused by prions, which are unique infectious agents that cause the normal prion protein to go "rogue."
Cashman explains that a protein is a chain of amino acids that only acquires its function by being folded properly. When a prion protein becomes misfolded after contact with another misfolded prion protein, it exposes certain regions in the normal prion protein, technically called "epitopes".
His team had identified a group of antibodies they thought could target these epitopes, and thus halt the disease. But in order to test the antibodies, using a technique called "immunostaining," they needed a line of easy-to-grow, regular cells to act as "negative controls."
"And lo and behold, we found a few that stained intensely with these antibodies," Cashman explained to CTV.ca.
Quite to Cashman's surprise, some of the cancer cell lines reacted to the same antibody he was testing on prion-infected brain cells.
"We realized that if these [cancer] tumour cells stain for these antibodies, [the epitopes] could be a target for cancer immunotherapies," Cashman said.
"We spent months trying to disprove the findings, thinking perhaps it was some kind of mistake. And eventually, we proved to our satisfaction that this antibody staining was real."
He says teams at UBC and B.C. Cancer Research Centre are now testing how these antibodies can be used to develop a vaccine to treat cancer in mice.
If all goes well, it's possible a vaccine could one day be tested on human cancers too, though Cashman cautions these are still "very early days."
One aspect that makes dreams of a vaccine against cancer exciting is that the therapy would target only "misfolded" prion proteins, while sparing normal prion proteins. So unlike chemotherapies that kill off healthy cells along with cancer, therapies that target misfolded prion protein would attack only rogue cells, sparing the healthy ones.
Cashman said it's possible that the same immunotherapy could also work in human prion diseases, such as "mad cow disease" and classical Creutzfeldt-Jakob Disease – but only if there were a way to identify infections in their earliest stages, before the illness caused symptoms.
"CJD is a very rapidly progressive disease, so by the time you make a definitive diagnosis, usually the patient has only a few weeks to live," Cashman explained.
"Perhaps if we had a good diagnostic for the incubating phase [of CJD], then yes, it's possible that a vaccine against these epitopes could block the infection before it gets to the brain. But that's theoretical," he said.
This new area of research is being funded under PrioNet Canada's Bootstrap program and with the assistance of two industry partners: Amorfix Life Sciences Ltd.; and Saskatoon-based PREVENT – the Pan Provincial Vaccine Initiative.
Cashman is the scientific founder and board member of Amorfix, and is the scientific director of PrioNet Canada.