At the heart of their argument, outlined in the Nov. 18 issue of Nature, are two key chemical signals, called Hedgehog and Wnt ("wint"), that are active in the stem cells that repair damaged tissue. Recently and unexpectedly, the signals also have been found in certain hard to treat cancers, supporting an old idea that some cancers may start from normal stem cells that have somehow gone bad.
Over the last 10 years, researchers have found examples of these so-called cancer stem cells -- the cells within a tumor that are capable of regrowing the tumor -- in certain malignancies of the blood, breast and brain. In most cases, however, it's not clear whether these cancer stem cells came from the tissue's normal, primitive stem cells or from the tissue's mature cells.
"Cancers associated with chronic irritation may be a good setting in which to determine whether stem cells are the starting place of tumors," says Phil Beachy, Ph.D., professor of molecular biology and genetics in Hopkins' Institute for Basic Biomedical Sciences and a Howard Hughes Medical Institute investigator. "Successful therapy depends on targeting the cells that drive cancer's growth and its spread, so we have to know which cells are important."
Chronic irritation damages tissues -- Helicobacter infection in the stomach leads to ulcers, for example, and chronic acid reflux (heartburn) erodes the lining of the esophagus. That damage triggers a repair process that requires tissue-specific stem cells to gather, multiply and eventually replace the damaged cells.
However, if recurring irritation and damage prevent the repair's completion, those helpful stem cells, in theory, could accumulate mutations that
Contact: Joanna Downer
Johns Hopkins Medical Institutions