Most of us have heard of stem cells. Over the last decade or so, these amazing, changeable cells — among nature's greatest chameleons — have achieved a certain wistful place in medicine. The idea is that if these cells can become, or be turned into, other cells, then maybe one day they could be used to replace vital cells that are tragically missing in such devastating diseases as Alzheimer's.

Stem cells made in the
bone marrow apparently make
house calls. They travel to the
injured organ, and turn into
that organ’s particular cells.
This is not always good.

But new research suggests that stem cells don't always play the hero. Sometimes, when these cells are injured — or maybe even simply inflamed — they can progress to become cancer. "Stem cells are rare, but they're found in each organ in the body," says Ganesh S. Palapattu, M.D., a former postdoctoral fellow in the laboratory of Hopkins scientist William G. Nelson, M.D., Ph.D., and now on the faculty at the University of Rochester. Their main job is to serve as genetic understudies — turning into, and playing the role of, specific cells if needed, so that an organ can keep doing its job. "However, if the stem cells present in an organ suffer genetic damage, these damaged cells may progress to become cancer."

Chameleon cell. This is a prostate epithelial cell — now. But it began its life as a stem cell in the bone
marrow. The green area shows the presence of a protein made only by bone marrow cells. The red shows
a protein made by prostate epithelial cells, and the blue shows the cell’s nucleus.

Stem cells made in the bone marrow appear to be even more versatile and generic pinch-hitters. If tissue in certain organs is injured, bone marrow stem cells apparently make house calls — they travel to the injured organ, and turn into that organ's particular cells. Scientists aren't sure how this phenomenon happens — whether the bone marrow stem cells turn into the specialized cells directly, or whether they fuse to other cells in the organ — but it's been seen in several organs. Can stem cells from the bone marrow form new cells in the prostate? Brady researchers Palapattu, Alan Meeker, Ph.D., Nelson, and colleagues found out that they can. In research published in the Journal of Urology, they found that in mice given a virus that causes inflammatory damage and tissue repair in the prostate, bone marrow stem cells appeared.

Some of the specific cells they produced were epithelial cells — cells of the tissue that lines the prostate, and protects it from the outside. What might these findings tell us about how prostate cancer develops? In 2004, a research team reported that bone marrow cells could give rise to epithelial cells in the stomach, in response to infection with Helicobacter, a form of bacteria that leads to stomach cancer. In their experiments, the bone marrow-derived stomach cells were the cells that progressed to become cancerous. Much of the Brady's research in recent years has turned up increasing evidence that inflammation and infection play a role in prostate cancer. The bone marrow-stem cell link may be another piece in this puzzle. It may be, says Palapattu, "that bone marrowderived prostate cells appearing in infected or inflamed prostates might be at risk to progress to prostate cancer."