Dr. Claude Perreault, professor of hematology at the Université de Montréal and director of the Centre de recherche Guy-Bernier at Maisonneuve-Rosemont Hospital, has succeeded in eliminating 100% of cancerous cells in mice suffering from leukemia, with no toxic side-effects or recurrence. Published in the journal Nature Medicine, the experiment that led to these spectacular results is one of the 10 major scientific discoveries of 2001, according to Québec Science magazine.

The weapon that's so successful consists of plain white globules - more specifically, T lymphocytes, the well-known "killer cells" that attack and destroy cells infected by a foreign body. Of these, the most powerful are the type CD8 or cytotoxic T lymphocytes (CTLs). Their function is to destroy infected cells by recognizing foreign antigens appearing on the surfaces of those cells. "These lymphocytes don't attack cancerous cells because they carry the individual's own 'identity card' and contain no foreign molecules," Dr. Perreault explained. "However, it was known that CD8 lymphocytes taken from a healthy person and injected into a cancer patient could attack the cancerous cells."

Dr. Perreault and his research team wondered if they could exploit this phenomenon. The problem was that the donor lymphocytes would "read" all cells in the recipient as "foreign" cells to be attacked indiscriminately. The toxic reaction was so strong that no treatment could be developed, and medical circles were extremely skeptical about the success of such an approach.

The Maisonneuve-Rosemont team, however, succeeded in "programming" CD8 lymphocytes to attack only cancerous cells. "We selected an antigen that causes a strong immunologic reaction and is highly abundant on the surface of cancerous cells," Dr. Perreault continued. "We then brought this antigen into contact with a particular type of purified CD8 lymphocyte taken from a healthy donor. This contact pre-activates the lymphocytes, which keep this type of antigen in their memory and then act in a selective manner."

The results in mice have been extraordinary: 100% of the cancerous cells (and not only the secondary cancers) were destroyed, and no recurrence has been seen in the six months following the experiment. "Six months in a mouse is equivalent to 20 years in a human," Claude Perreault points out. "And if there had been a recurrence, the lymphocytes would have again recognized the cancer antigens." As the lymphocytes and targeted antigens are identical in humans and mice, there is every reason to hope that similar results will be obtained with humans.

Researcher: Claude Perreault
Phone: (514) 252-3557