Stem cells core of more cancers

A spate of new discoveries about the basic biology of cancer is pushing researchers toward an astonishing conclusion: For decades, efforts to cure the disease may have targeted the wrong cells.

Current therapies treat all cancer cells the same. They're aimed at shrinking tumours on the basis that the various cells within them all have similar powers to spawn new cancers and spread destruction.

But mounting evidence suggests that cancer's real culprits -- the roots of perhaps every tumour -- are actually a small subset of bad seeds known best to the world as stem cells. ...

Dr. Dick, who discovered the first cancer stem cell in 1994 in leukemia, said the new work shows that while current therapies treat colon cancer as a "homogeneous entity, not every colon cancer cell has the ability to keep that tumour going; only one in 60,000."

New research has repeatedly shown that contrary to conventional wisdom, only abnormal stem cells can sprout and sustain tumours by renewing themselves indefinitely. Without signals from cancer stem cells, ordinary tumour cells seem to stop growing.

What's more, some experiments have found these bad seeds to be highly resistant to standard cancer therapies, including radiation, medicine's nuclear weapon.



The findings may explain why cancers come back even after treatments seem to make tumours disappear. Just a small number of mutant stem cells left behind -- invisible to the naked eye or any scan -- may be enough to spark cancer's regrowth.

"Killing 98 per cent of tumour cells on a scan may look good, but that 2 per cent could be enough to grow the cancer back," said Jeremy Rich, a neuro-oncologist and cancer researcher at Duke University in North Carolina. "Maybe one of the reasons we haven't been as good as we thought we could be is because we've been looking at the wrong cells." - globeandmail

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Normal Stem Cells vs. Cancer Stem Cells

The stem cells in tumors discovered by researchers at the University of Michigan are not the same type of stem cells being explored as potential therapies to treat degenerative diseases. Both normal embryonic and adult stem cells are being actively studied for their ability to proliferate and replace damaged cells in diseases such as diabetes, Parkinson's disease, and heart disease.

But stem cells in tumors develop because of mutations that accumulate over years and often decades. The mutations are thought to promote the tumor stem cells' ability to proliferate, eventually leading to cancer. - genomenews