Like some stem cells, cancer cells can grow without pause. Some cancers use stem cells' tricks to do this, and so some cancer researchers study stem cells.
One test to determine whether a cell is an embryonic stem cell is to inject it into a mouse. Mouse tissue and embryonic stem cells will interact so that the embryonic stem cells form a bizarre, non-cancerous tumor, called a teratoma. Teratomas contain all the different tissue types embryonic stem cells can become. Though rare, these tumors occur spontaneously in the testes or ovaries. They can grow hair and even teeth.
Just as no hostess would serve milk with flour and call it cheese with crackers, embryonic stem cell therapies would not use embryonic stem cells directly. Instead, embryonic stem cells would be first grown into more specialized cells, say neurons (for diseases like Parkinson's or multiple sclerosis) or pancreatic cells (for diabetes). Of course, researchers will have to be certain they can select only the types of cells they want, and perhaps invent strategies to kill any transplanted cells that retain the embryonic characteristics after they are transplanted.
Many different types of cells live in a cancerous tumor, even if that tumor is no bigger than a pea. Cancer stem cells have been identified in leukemia, breast and brain cancers. Researchers aren't sure whether cancer stem cells come from stem cells gone bad or if mature cells somehow acquire stem cell–like characteristics. They also aren't sure whether the same mechanisms that allow stem cells to keep dividing are the same mechanisms that allow cancer cells to keep dividing. The answers probably vary by cancer type.
Recently many researchers have come to believe that cancer recurs when most of a tumor is destroyed, but a few cancer stem cells escape. Researchers are trying to work out how cancer stem cells resemble tissue-specific stem cells. One theory is that treatments that can kill cancer stem cells might leave normal cells unharmed but still eradicate cancer. A major worry is that treatments that kill cancer stem cells will also kill healthy tissue-specific stem cells, as now happens in some chemotherapy.
Rights and permissions
About this article
Cite this article
What's the relationship between stem cells and tumors?. Nat Rep Stem Cells (2007). https://doi.org/10.1038/stemcells.2007.25