Common cancer treatments may create dangerous cancer stem cells

By Charles Q. Choi Published September 27, 2012| MyHealthNewsDaily


Radiation  therapy and chemotherapy aimed at killing cancer cells may have the undesirable  effect of helping to create cancer stem cells, which are thought to be  particularly adept at generating new tumors and are especially resistant to  treatment, researchers say.

The  finding might help explain why late-stage  cancers are often resistant to both radiation therapy and  chemotherapy, and it could point to new strategies to fight tumors.

Past  studies hint that cancer  stem cells give rise to new  tumors. Researchers suggest they are ultimately responsible for the recurrence  of cancers and the dangerous spread of a cancer throughout the body. Scientists  also have found that cancer stem cells are more likely than other cancer cells  to survive chemotherapies and radiation therapies, probably becausetheir  “stemness” allows them to self-replenish by repairing their damaged DNA and  removing toxins.

The  exact origin of cancer stem cells is debated. One possibility is that normal  stem cells — which are valued for their ability to give rise to other cell types  in the body — mutate to become cancerous. Another is that regular cancer cells  somehow acquire stem cell properties.

The  new study suggests regular cancer cells can indeed give  rise to cancer stem cells, and that the radiation commonly used to  treat cancer can trigger their stemness.

“Radiotherapy  has been a standard treatment for cancer for so long, so we were quite surprised  that it could induce stemness,” said study researcher Dr. Chiang Li, of Harvard  Medical School in Boston.

The  scientists exposed regular cancer cells to gamma-rays, one form of ionizing  radiation. They found that under the conditions that normally foster stem cell  growth, regular cancer cells formed balls of cells — a hallmark  of cancer stem cells.

Additionally,  analysis of these irradiated cancer cells revealed activity of genes linked with  stem cell behaviors, according to the findings the scientists detailed online  Aug. 21 in the journal PLoS ONE.

Chemotherapy  may have similar effects, according to previous findings that Li and his  colleagues detailed in July in the journal Cell Cycle.

“So  radiation and chemotherapy not only might create cancer stem cells, any  pre-existing cancer stem cells in a tumor were veryresistant  to radiation and chemotherapy, so they remain as well,” Li said. “This could  help explain why these therapies are sometimes not as effective as we might  hope.”

Li  cautioned these lab findings might not prove relevant in patients in real life.  “This was all carried out in the petri dish,” he said. “There is a long way we  have to go before we can be sure about its clinical implications for patients,  if any.”

Still,  this research suggests that if scientists find a way to inhibit stemness in  cancers, radiation therapy and chemotherapy then might cleanly finish off  tumors.

“There  are lots of projects both in academia and industry right now to develop cancer  stem cell inhibitors, although those are still in early stages,” Li said.

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