Killing Breast Cancer Stem Cells

Researchers at the Broad Institute and Whitehead Institute (both in Cambridge, Massachusetts) have discovered a chemical that kills breast cancer stem cells in mice. These cells are believed to be the cause of the spread of cancer and also of the recurrence of some cancers that previously appeared to be eradicated. By killing these stem cells, both the spread and reappearance of cancers could be decreased and, ultimately, prevented.
 The chemical structure of salinomycin (Source: Wikimedia/Edgar181)
The chemical structure of salinomycin
(Source: Wikimedia/Edgar181)

Cancer stem cells are largely resistant to current cancer treatments so new treatments targeting these cells are important. However, growing them in laboratory settings for further study has proven difficult; the cells tend to lose their stem-cell like properties when grown artificially. The researchers drew on a new method developed by Robert Weinberg of the Whitehead Institute to create large numbers of cells with many of the same properties as cancer stem cells. They were able to generate enough cells to test their interactions with 16,000 different chemical compounds.

An automated testing process identified 30 candidate chemical compounds for further testing with the stem-like cells. From that group, they discovered a compound called salinomycin that was particularly potent. It not only kills the laboratory-created cancer stem cells but naturally occurring ones as well. Salinomycin kills more than 100 times the number of cancer stem cells than the common current breast cancer treatment paclitaxel. It also has reduced tumor growth in mice.

The team also examined the effect of salinomycin on groups of genes known to be active in cancer stem cells. These same genes are often present in the most aggressive tumors and in patients with the poorest prognoses for recovery. The salinomycin decreased the activity of these genes which could explain its effectiveness in killing the stem cells.

The salinomycin research is still in its early stages. Researchers have no idea whether the same effects seen in the laboratory and in mice will be seen in humans and they still need to definitively discover why the treatment works so well (the gene activity is just one possible explanation but the specific link between the chemical and the decrease in gene activity is still unknown). There are also plans to expand the testing beyond the initial 16,000 chemical compounds in the initial study in hopes of finding additional chemicals capable of killing breast cancer stem cells.

TFOT has previously reported on other innovative cancer research including the use of a virus to attach fluorescent genes to cancer cells, the development of gold nanorods capable of seeking out cancer cells, a blood test capable of detecting cancer in even its earliest stages, and a sensitive electronic nose that can sniff out cancer cells by analyzing the chemicals it encounters.

Read more about the search for chemicals that kill cancer stem cells in this Broad Institute press release.

Image icon credit: Dr. Raowf Guirguis/National Cancer Institute