In a study published in Thursday's edition of the journal Cell, a group of medical researchers said they had discovered that a compound called salinomycin directly targeted cancer stem cells.
"Evidence is accumulating rapidly that cancer stem cells are responsible for the aggressive powers of many tumors," said Robert Weinberg, a member of the Whitehead Institute for Biomedical Research, and one of the study's authors.
Cancer stem cells are rare but aggressive parts of tumors and their ability to seed new tumors while proving largely resistant to chemotherapy and radiotherapy makes them a key component in treating cancer patients.
"Many therapies kill the bulk of a tumor only to see it regrow," said Eric Lander, director of the Broad Institute of the Massachusetts Institute of Technology and Harvard University, another author of the Cell paper.
Previous attempts to study cancer stem cells have been stymied by difficulties in locating the rare cells within tumors, and the tendency of the cells to lose their key properties when grown outside of the body.
To conduct their research, the study group found a novel way to manipulate cultured breast cancer cells into cancer stem cells that retained the tendency to seed tumors and resist anti-cancer treatments.
The researchers then analyzed some 16,000 chemical compounds, looking for one that could target the cancer stem cells, eventually narrowing the field to 32, and then down to one: salinomycin.
The compound showed impressive results, both against naturally-occurring and manipulated cancer stem cells, reducing the proportion of breast cancer stem cells by more than 100-fold compared to a commonly-used breast cancer treatment called paclitaxel.
It also inhibited the ability of the cancer stem cells to seed new tumors when injected into mice, and slowed the growth of existing tumors in the animals.
"It wasn't clear it would be possible to find compounds that selectively kill cancer stem cells," said Piyush Gupta, one of the study's lead authors and a researcher at the Broad Institute. "We've shown it can be done."
The compound even targeted groups of genes, usually linked to particularly aggressive tumors and poor patient prognoses, that are highly active in cancer stem cells, effectively decreasing their activity, the study said.
"Our work reveals the biological effects of targeting cancer stem cells," said Gupta. "Moreover, it suggests a general approach to finding anti-cancer therapies that can be applied to any solid tumor maintained by cancer stem cells."
The researchers are not yet sure how salinomycin works, and there are a number of pharmaceutical steps that would need to be taken before it could be used to treat cancer patients.
However, the study's authors are positive both about the prospects for salinomycin and a number of the other chemical compounds tested, several of which also showed some ability to target cancer stem cells.