Telltale tail

时间:2019-03-07 06:06:06166网络整理admin

By Ian Sample MAKING tumour cells look like microscopic comets could save people with bladder cancer from the trauma of unnecessary surgery or radiotherapy. Some bladder cancers are superficial and can be removed by scraping the suspect cells of the bladder lining. But nearly a third grow into the muscle wall that surrounds the bladder. This necessitates more severe treatments such as surgery, which involves the removal of part or all of the bladder, or radiotherapy which typically lasts six weeks. Choice of treatment depends largely on the location of the tumour and the risks of surgery versus radiotherapy. But half the patients sent for radiotherapy do not respond to the treatment because their tumour resists radiation—allowing it to grow or shed cells that cause secondary tumours to grow elsewhere in the body. Now, researchers in Ulster and Leicester believe a quick test for a bladder tumour’s resistance to radiation could help them decide which is the best therapy. They start by breaking down a sample of the tumour into single cells. These cells are set in a gel called agarose and bombarded with X-rays, equivalent to the dose a patient would receive during radiotherapy. The scientists then treat the cells with detergents to break up the cell membranes. “If you then apply an electric field across the gel, the broken DNA migrates out of the cells and tails out like a comet,” says George Jones of the University of Leicester. The way the negatively charged DNA breaks up shows that radiation is killing the tumour. “The more damage you have done to the DNA, the more you get in the tail.” They have dubbed their test a “comet assay”. Jones and his colleagues in Leicester will begin collecting tumour samples in January. These will then be sent to Valerie McKelvey-Martin at the University of Ulster at Coleraine for testing. If the tests are successful, the assay could be used to assess the radiosensitivity of tumours elsewhere in the body. “This is potentially a very interesting technique,” says Adrian Harris of the Imperial Cancer Research Fund in Oxford. But he warns that the test might not give the full picture. “The comet assay may pick up radiotherapy resistance due to DNA repair, but would miss radiotherapy resistance caused by lack of oxygen,