Anti-psychotic drug kills cancer stem cells

VANCOUVER - A team of Canadian scientists have discovered that thioridazine, a drug used to treat psychotic disorder, could successfully kill cancer stem cells in humans without the toxic side-effects on normal cells.

The research, published Thursday in the science journal CELL, may pave the way for the development of anticancer drugs for treatment of various cancers.

Conventional cancer treatments, like chemotherapy, work in a way that is toxic to cells, which may also lead to side-effects such as hair loss, nausea and anemia, according to the researchers from McMaster University.

Stem cells have long been believed to be the source of many cancers. In 1997, Canadian researchers first identified cancer stem cells in certain types of leukemia. Cancer stem cells have since been identified in blood, breast, brain, lung, gastrointestinal, prostate and ovarian cancer.

"The unusual aspect of our finding is the way it kills cancer stem cells, by differentiating them and changing them into cells that are non-cancerous," said Mick Bhatia, the principal investigator for the study and scientific director of McMaster's Stem Cell and Cancer Research Institute.

"We think this lack of toxicity is why it doesn't have effects on the normal cells, which would be beneficial to the patients," Bhatia said.

Bhatia said their next step was to test thioridazine in clinical trials, focusing on patients with acute myeloid leukemia whose disease has relapsed after chemotherapy. He wants to find out if the drug can put their cancer into remission, and prevent the cancer from coming back by targeting the root of the cancer (cancer stem cells).

Bhatia's team also found that thioridazine works through the dopamine receptor on the surface of the cancer cells in both leukemia and breast cancer patients.

The finding means it may be possible to use thioridazine as a biomarker that would allow early detection and treatment of breast cancer and early signs of leukemia progression, he said.

The research team would also look into the effectiveness of the drug in other types of cancer. Bhatia said they will collaborate with academic groups as well as industry to move forward.

"The goal for all of the partners is the same - to find unique drugs to change the way we tackle and treat cancer," he said.