Breast cancer cells (green) are more likely to metastasize to the lung if MSCs are around (right) to enhance their invasive ability.

KARNOUB/MACMILLAN

Tumors that escape from their original site are associated with a poor prognosis for cancer patients. New research by Antoine Karnoub, Robert Weinberg (Whitehead Institute, Cambridge, MA), and colleagues suggests that the ability to escape may be acquired through the tumor's interactions with normal tissues.

A growing tumor is considered by its surrounding normal tissue to be a bit like a wound. As also occurs during the wound response, tumors recruit mesenchymal stem cells (MSCs)—which are meant to help with repair—from the bone marrow. Karnoub et al. hypothesized that these MSCs, rather than being helpful, may instead advance disease. To investigate this idea, they injected human breast cancer cells, either alone or along with human MSCs, into mice and then looked for...

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