Researchers find pancreatic cancer stem cells


Feb 1, 2007

WASHINGTON (Reuters) -- Researchers have discovered a small population of stem cells in pancreatic cancer that appear to drive tumor growth, opening the door for a potential new approach for treating this particularly deadly disease.

Writing in the journal Cancer Research on Thursday, University of Michigan scientists said finding cancer stem cells in pancreatic tumors could lead to the development of drugs intended to target and kill these cells.

Scientists have toiled with little success to find better ways to treat cancer of the pancreas, which has the lowest survival rate of any major form of cancer.

It kills 97 percent of people in whom it is diagnosed within five years -- half within six months of diagnosis. Pancreatic cancer spreads quickly and is rarely is detected at an early stage. In the United States alone, it kills 33,000 people a year.

The pancreas is a gland situated behind the stomach that secretes a digestive fluid and the hormone insulin.

"The clinical implications of this work are significant," Dr. Diane Simeone, director of the Gastrointestinal Oncology Program at the University of Michigan Comprehensive Cancer Center and lead author of the study, said in an interview.

"We've made baby steps in improving the survival in these patients -- on the order of a few months (longer to live) -- over the past decade or so. But we really haven't had a major breakthrough in coming up with something that has the potential to provide a cure," she said.

Simeone said there is emerging evidence that within cancers, there is a small subset of cells that are responsible for the growth and propagation of tumors. The idea is that these cells with stem-cell characteristics -- the ability to self-renew and differentiate into other cell types -- are the ones fueling tumor formation.

The root of a weed

Killing these cancer stem cells is akin to yanking out the root of a weed, Simeone said.

Stem cells have been detected in other cancers, including leukemia and breast, brain, central nervous system and colon cancers.

Simeone's team took tissue samples from 10 pancreatic cancer patients. The samples then were divided and implanted into mice to grow new tumors to produce a bigger amount to be examined.

The researchers sorted millions of cancer cells to find those with one or more of three specific characteristics on their cell surface. It turned out that less than 1 percent fell into this category -- the ones thought to be pancreatic cancer stem cells.

The researchers then demonstrated these cells aggressively drove tumor formation by injecting them into mice.

Some cancer experts believe the key to beating cancer is to target these stem cells. That would represent a different approach from the current one of shrinking tumors by killing as many cells as possible. The current approach may be flawed, these experts think, because cancer stem cells may resist standard therapies.