Figure 1.

Astrocytes impact both early and late stage brain metastasis progression. Circulating tumor cells producing ST6GALNAC5 bypass the BBB and seed the brain parenchyma. Tumor L1CAM and SERPIN expression is required for colonization and expansion in the brain. This sequence of events suggests that the astrocyte response selects for cancer cells with the best survival potential in the brain microenvironment. Chen et al.'s findings reveal that enduring cancer cells in turn instruct astrocytes to promote survival signaling.