Evidence both for and against the cancer stem cell hypothesis is arriving rapidly these days. Scientists "have answered a central question in cancer biology: whether normal stem cells can give rise to tumors. Stem cells are immature cells that can renew themselves and give rise to mature differentiated cells that compose the range of body tissues. In recent years, researchers have developed evidence that cancers may arise from mutant forms of stem cells. Like a brand-name product instantly identifiable by its trademarked logo, normal and cancerous stem cells display on their surface characteristic proteins, including Prominin1 or CD133. A key question in cancer biology has been whether these so-called cancer stem cells arise from normal stem cells or more mature cancer cells that somehow reacquire the characteristics of stem cells. ... investigators show that Prominin1 marks normal intestinal stem cells and that these cells, when mutated, give rise to intestinal tumors. The finding could also aid in identifying the source of cancer stem cells in the lung, kidney, brain, pancreas and other tissues." If cancer stem cells are in fact the root of a majority of cancers, then targeted therapies presently in development will ensure that cancer becomes a lot rarer a decade from now.