Cancer is at its most deadly when it gets itchy feet. As it spreads around the body (a process called metastasis), it becomes increasingly unmanageable. To leave one tissue, a cancer cell must break through the protective basement membrane that lines the edges like a city wall. They test for weak spots by prodding out microscopic battering rams called invadopodia. Eventually, these make a small hole in the wall, but how the cells then exploit this tiny gap was unclear. By directly filming a single cell over several hours, new research has identified a second protrusion (shown briefly spurting from a cell) that squeezes into the hole, then swells to enlarge the gap sufficiently. It turns out this fleeting bulge is prompted by a chemical cue called netrin, which is common in metastasising cancers. Figuring out how to block netrin just might help keep cancer in its place.
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