Making an Entrance

Before a tumour sends its cells around the body to find new sites to invade and colonise – a process known as metastasis – it sends packages of proteins to prime those areas. In this section of mouse lung, for example, such packages have caused the blood vessels (cyan) to become leaky – shown by the presence of a red marker in the surrounding tissue. And this leakiness would subsequently enable tumour cells to exit the bloodstream and invade. The packages (or vesicles) contain the protein ITGα5, but interestingly it doesn’t affect the blood vessels directly. Instead, the ITGα5-filled vesicles activate local macrophages, prompting them to release inflammatory signals, which in turn promotes vessel leakiness. During an infection, increased vessel permeability allows immune cells to gain access to infected tissues. The cancer cells, then, have simply hijacked that same system to gain access for themselves.

Written by Ruth Williams

Ruth Williams

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Ruth is a freelance science journalist based in the US. She's a regular correspondent for The Scientist, and her work has appeared in The Lancet, Nature, Scientific American Mind, BBC Focus and elsewhere. Twitter @rooph

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• Image from work by Shani Dror and colleagues
• Children’s Cancer and Blood Foundation Laboratories, Departments of Pediatrics, and Cell and Developmental Biology, Drukier Institute for Children’s Health, Meyer Cancer Center, Weill Cornell Medicine, New York, NY, USA
• Image originally published with a Creative Commons Attribution – NonCommercial – NoDerivs (CC BY-NC-ND 4.0)
• Published in Nature Cancer, August 2026