New tests identify cancer "ringleaders"
来源：未知 作者：真郭 时间：2019-03-02 05:09:05
By Andy Coghlan Cancer treatments could improve by targeting cancer “stem cells” which give birth to all other cells in tumours, say researchers who have devised techniques for identifying and potentially killing two types of cancer stem cell. Killing the stem cells is vital because these cells avoid destruction and trigger regrowth of cancer even when all other cancer cells have been obliterated through standard drug or radiation therapy. By wiping out the stem cell “ringleaders” as well as the other cancer cells, doctors stand a much better chance of eradicating the cancer in a patient for good. Now, new techniques to do this developed at the University of Cambridge, UK, and Kumamoto University, Japan, have been licensed for commercialisation to Stemline, a biotechnology company in New York, US. “Once we have eradicated the cancer stem cells, in essence we have destroyed the engine responsible for treatment failure and disease recurrence, the major problems for fighting cancer,” says Ivan Bergstein, chief executive of Stemline. But it could be five years before the first treatments start to come through, warns Toru Kondo, head of the team at the University of Cambridge which pioneered the two new tests. The first test relies on antibodies which recognise and bind to CD133, a surface protein unusually common on stem cells and already known to orchestrate several human cancers, including those of the blood, prostate and nervous system. The second test relies on a blue dye absorbed without trace by ordinary cancer cells but pumped out again by stem cells found in certain cancers, such those of the breast and aggressive glioma cancers found in the brain. They can do this because, unlike the ordinary cells, they have a transporter protein, ABCG2, which pumps the dye out through the cell membrane. “If you use this special dye to label cells, the cancer stem cells exclude it,” Kondo explains. Stemline is using the tests to find out which cancers depend on which stem cells, and to identify drugs which kill the cancer stem cells but spare healthy stem cells. One possibility, says Kondo, is to target the cancer stem cells with specially generated antibodies loaded with toxins or radioactive elements lethal to the stem cells. But it might first be necessary to identify further telltale markers of the cancer stem cells to make doubly sure that the cancer stem cells alone are killed, says Peter Dirks of the Hospital for Sick Children in Toronto, Canada. Dirks led a team which demonstrated in 2004 that brain cancers transplanted into mice only grew if the transplanted tissue included stem cells bearing the surface marker, CD133. But Dirks warns that some healthy stem cells carry CD133 or ABCG2 on their surfaces too, and so could be accidentally destroyed by drugs targeting the cancer stem cells. “Hopefully, the investigators can find new markers that could be unique to cancer stem cells, enabling safer targeting,” says Dirks. Indeed,