Drug Compound Discovered That Attacks Cancer Stem Cells
Posted on: Friday, 14 August 2009, 10:40 CDT
U.S. researchers reported on Thursday the discovery of a compound that can kill breast cancer stem cells, a kind of master cancer cell that resists conventional treatment and may explain why many cancers grow back.
Scientists employed a new method of screening for drugs that specifically target and kill cancer stem cells. They also suggested it could be used to find drugs targeting other cancer stem cells as well.
Researches have been attempting to destroy these master cancer cells for some time, in hopes of finding an easier way to cure cancer.
Piyush Gupta of the Massachusetts Institute of Technology and the Broad Institute said there is a lot of evidence to suggest now that these cells are responsible for many of the recurrences that are observed after treatment has stopped.
However, cancer stem cells are rare and difficult to study in the lab because they quickly change into other types of cells. And experts say they are even harder to destroy.
Gupta said it wasn't clear if it would be possible to find compounds that selectively kill cancer stem cells, but that's what they did.
Gupta's team first devised a method for stabilizing cancer stem cells in the lab and multiplying them. The cells were then tested against 16,000 natural and commercial chemical compounds to see which ones were able to kill the cancer stem cells specifically.
Among the initial 32 compounds tested, they narrowed the list down to a handful of chemicals, and tested them in the lab and in mice.
The chemical salinomycin was discovered to be 100 times more potent at killing breast cancer stem cells than Bristol-Myers Squibb Co's cancer drug Taxol, or paclitaxel.
The team found that cancer stem cells treated with salinomycin were far less able to start breast cancers when injected into mice than cancer stem cells treated by paclitaxel. The treatment also seemed to slow the growth of tumors in lab mice.
“But it is not clear if salinomycin will emerge as the best drug compound for killing breast cancer stem cells -- or that it will be safe to use in people with cancer,” Gupta said.
However, the study offers a new roadmap for drug companies to isolate and test compounds capable of killing the cells.
The specific role that cancer stem cells play in promoting different types of cancer is still poorly understood, but many researchers think they may be the reason why so many cancers come back even after powerful chemotherapy and radiation treatment.
Robert Weinberg of MIT, who worked on the study, said the theory is that the cells are self-renewing, which means they can make identical copies of themselves.
"They have the power to generate a new tumor, and they are resistant to existing anti-cancer therapeutics. That suggests the need to develop therapies for cancer stem cells," he said.
While it will likely take several years before therapies targeting cancer stem cells can be used in people, the new finding do hold promise for a new way of looking for cancer treatments, Weinberg said.
"Ideally, if one hit the cancer stem cell, sooner or later the bulk of the cells of the tumor, which lack a self-renewal capability, would gradually poop out and the tumor would eventually die just by attrition," he explained.
The researchers are hopeful that in the near future combination therapies might couple more traditional cancer drugs with those designed to hit the cancer stem cells that would otherwise get left behind.
Dr. Alexis Willett, head of policy at Breakthrough Breast Cancer, said it was important to remember that this is very early research and it will be some time before it is clear whether it will lead to an effective breast cancer treatment.
The American Cancer Society shows that behind heart disease, cancer is the No. 2 killer of Americans, with about 560,000 deaths annually.
The full study was published in the journal Cell.
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Image Caption: In a comparison of a control to the chemical identified by the Weinberg/Lander team, called salinomycin, the tumor cells (stained dark purple in both slides) were unaffected by the control, but salinomycin killed many tumor cells (stained pink).
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Source: redOrbit Staff & Wire Reports
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