Pomeroy's team has been able to identify the origin of cancer stem cells in medulloblastomas based on their genetic "signatures." They are now using this information to better understand these cells' properties, hoping to attack their vulnerabilities. The team has already identified a molecular pathway that is critical for sustaining growth of cancer stem cells in about 25 percent of medulloblastomas. “Instead of using toxic means like radiation or chemotherapy to kill cancer cells, we could develop a therapy that turns off the growth-promoting mechanism," says Pomeroy. At left: The cells from a medulloblastoma look similar to one another, but Pomeroy can identify the cancer stem cell cohort based on its genetic blueprint.