A DEVICE that uses lasers to spot cancer cells by testing how stretchy they are is showing early promise in tests. The technique identifies cancer cells quickly and reliably, and could tell doctors in advance whether a tumour is likely to spread to other parts of the body.
Pathologists routinely look for cancer cells in samples taken from patients. Cancer cells are known to stretch and lose their elasticity, and under the microscope appear deformed compared with healthy cells. But it takes a well-trained eye to spot cancer in its early stages.
Jochen Guck, a physicist at Leipzig University in Germany, and his colleagues reasoned that prodding cells would give more information than just looking at them. 鈥淚f you go to a supermarket to buy tomatoes, they may all look round and red,鈥� says Guck. 鈥淚t is only by squeezing them you can tell if they are mushy.鈥�
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The researchers pump cells one at a time through a narrow gap between two laser beams that hold the cell tightly, in a similar way to 鈥渙ptical tweezers鈥� (see Graphic). The beams arrive from opposite directions and are refracted as they enter and leave the cell. That changes their momentum, exerting a force on the cell with the net result that it is stretched in both directions. The more powerful the laser the more the cell stretches before it rebounds. Cancer cells are less elastic and take longer to recover.
鈥淭his stretcher idea with counter-propagating beams is very innovative,鈥� says Kishan Dholakia, an expert in optical tweezers at the University of St Andrews in Scotland. 快猫短视频 first reported on the idea in 2001 (13 October, p 22), but since then the researchers have replaced the expensive laser they were using with optical fibre lasers, as well as incorporating an automated channelling system that lets them test hundreds of cells an hour rather than just a few a day.
The researchers have also found that while healthy fibroblast cells stretch by 4 per cent and quickly spring back to normal when the laser intensity is turned down, malignant fibroblasts stretch by 10 per cent and do not regain their original shape. Guck is hopeful the method will detect differences in elasticity before the cells start to look visibly different, meaning cancers could be picked up earlier.
And in tests with human breast cells, the most aggressive cancer cells stretched nearly three times more than primary tumour cells that are unlikely to spread around the body. Soft cells can squeeze easily through tissue to get into the bloodstream,鈥� says Guck. He has now teamed up with researchers from the University of Leipzig Medical School to carry out trials on patient samples.
