Figure 1.

Hh signaling conditions the milieu to support metastasis of breast cancer cells to the bone. Depicted here is the first of the two microenvironments, the milieu of the primary tumor. Hh signaling in the tumor cells impacts the stromal cells in the environment, which in turn amplify paracrine Hh signaling by producing growth factors that propel epithelial-mesenchymal transition. Concomitantly, secreted, soluble proteins produced by the primary tumor contribute towards conditioning the secondary site for the arrival of the tumor cells.