BACKGROUND: Researchers at St. Jude Children's Hospital have found that brain tumors appear to arise from cancer stem cells that live inside tiny protective 'niches' formed by blood vessels in the brain. Breaking down these niches is a promising strategy for eliminating the tumors and preventing them from regrowing.
ABOUT CANCER STEM CELLS: Scientists previously believed that tumors are lumps of cancerous tissue that must be completely removed or destroyed to cure a patient. But over the last five years, cancer researchers have learned that not all cancer cells are created equal. In the same way that normal tissue in the body is generated from stem cells, so is cancer. CSCs are the ultimate source of the tumor, consistently supplying it with new cells. Researchers have identified the CSCs for acute myeloma leukemia, four types of brain cancer, and breast cancer. So it is possible that we need not kill all cancer cells to rid a patient of the disease. Targeting the CSCs specifically might be much more efficient.
CANCER'S ACHILLES HEEL: To find a weakness for CSCs, neurobiologists at St. Jude compared them to noncancerous neural stem cells. These neural tissue generators are concentrated in regions rich in blood vessels. The vessels are lined with endothelial cells, which secrete chemical signals that help stem cells survive. CSCs, they discovered, required similar conditions to flourish: in over 70 human brain tumors, the CSCs were frequently located close to tiny vessels called capillaries. When the researchers injected mice with a mix of stem and endothelial cells from human brain tumors, those animals sprouted larger tumors than the mice that received stem cells alone.
NEW DRUG THERAPY: The new findings from St. Jude indicates that it is possible to kill the cancer by disrupting the shielded compartments in the small capillaries of the brain where CSCs reside. Anti-angiogenic drugs, such as Avastin, block the formation of new blood vessels. In tests with mice, those same drugs cause a significant drop in cancer stem cells and slow tumor growth. Human clinical trials are currently in progress at St. Jude to determine the effectiveness of Avastin and another anti-angiogenic drug in eliminating tumors and preventing their recurrence in children with brain cancers.
The Biophysical Society contributed to the information contained in the TV portion of this report.