Sending the advance party for metastases

Tumor cells induce other cells to act as trailblazers, say Rosandra Kaplan, Rebecca Riba, Shahin Rafii, David Lyden (Weill-Cornell, New York, NY), and colleagues. Those cells set up remote sites to which the tumor cells can subsequently metastasize.

The trailblazers are bone marrow–derived cells (BMDCs) that were earlier implicated in building blood vessels in established tumors. When Kaplan saw the cells in metastases she thought it was the same story. “For a long time we thought the tumor cells got there and then brought the bone marrow cells afterwards,” she says. But careful examination showed that, both in mice and humans, the BMDCs showed up several days before the first tumor cells. Interfering with the trailblazing BMDCs prevented metastasis.

The group now thinks that growth factors from the tumors have two distinct...