WEDNESDAY, Aug. 1 (HealthDay News) -- While scientists hotly debate the existence of cancer stem cells, three related new studies, all conducted on mice, provide some supporting evidence.
Stem cells are the foundation for healthy cell growth in the body. Some researchers believe that malignant stem cells also exist -- so-called cancer stem cells that generate tumors and resist treatment by simply re-growing afterward.
"Cancer stem cells are still controversial, but with progress in studies like these, it's less about whether they exist and more about 'what does this mean?'" said Dr. Max Wicha, director of the University of Michigan Comprehensive Cancer Center, who is familiar with the new findings.
Appearing online Aug. 1 in the journal Nature, one study involved mice with glioblastoma, the most common malignant brain tumor in adults and a particularly lethal cancer.
Researchers led by Luis Parada, a professor and chairman of developmental biology at University of Texas Southwestern Medical Center in Dallas, genetically engineered mice so they would develop glioblastoma.
Then they developed a "transgene" designed only to be active in stem cells in healthy adult brains. They marked this transgene with a green fluorescent protein so the researchers would see it wherever it appeared.
To this transgene they added a virus gene that would self-destruct if treated with the drug acyclovir.
Next, they put the transgene into the mice, which developed tumors. In every mouse, a subset of cells in the malignant brain tumor cells was green.
"The next obvious question was: Since the 'transgene' was designed to be active in stem cells, might these be stem cells?" Parada said.
The researchers gave the drug acyclovir to mice that had tumors. "And when we did that, the tumors stopped growing," he said.
The investigators also looked at "regu
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