What are stem cells?

Stem cells are immature cells that develop into specific cells to form organs and tissues in our body. The National Cancer Institute likens them to starter dough in baking. Stem cells help the body repair itself.

Stem cells are different from normal cells in several important ways. They divide, making an exact replica of themselves, and they duplicate to make a copy cell and a cell that continues to divide and become more specialized, eventually differentiating into cells that form tissues and organs. Stem cells can divide indefinitely.

Cancer stem cells share these same properties. However, instead of developing into healthy tissue, cancer stem cells become tumors and may even metastasize, or spread. Once a cancer spreads to other parts of the body, it's much harder to treat. Traditional cancer treatment therapies, such as surgery, chemotherapy and radiation, do not kill these resistant cancer cells. Even after treatment destroys a tumor, cancer stem cells can regenerate. When they return, they're even more resistant to treatment than the original cancer cells. In fact, the American Association for Cancer Research suspects that traditional anti-cancer treatments may actually expand populations of cancer stem cells.

Cancer stem cell research

Stem cell research helps scientists understand how tissues grow and develop so they can determine what goes wrong during disease or injury.

Although cancer stem cells mature into cancer cells, they may also provide a target for effective cancer treatments. Researchers are trying to isolate pure populations of stem cells representing different types of cancer to examine the differences between normal and cancer stem cells, learn how cancer stem cells signal to each other, and develop ways to interrupt the mechanism by which cancer stem cells renew themselves. The goal of new stem cell treatments is to use the body's natural defenses to kill cancer stem cells so they cannot grow, while not harming healthy tissue cells.

Researchers have identified cancer stem cells for breast cancer, pancreatic cancer, colon cancer, bladder cancer and ovarian cancer, and malignant brain tumors. In one study, for example, scientists found that by using stem cells to deliver anticancer treatment agents directly to tumors in mice, they could target and destroy lung metastases from breast cancer.