ROCK and Rho in 3D

Breast cells pull on their surroundings to sense whether to proliferate or differentiate, according to Wozniak et al. on page 583. This matrix-sensing pathway may explain why carcinoma risk is increased in women with fibrous breast tissue.

Differentiation of breast epithelial cells into tubules occurs in vitro if the cells are cultured in a 3D collagen matrix floating in medium. If the same matrix is made more rigid by attachment to a surface, tubulogenesis is disrupted, indicating that breast cells sense the flexibility of their surroundings. Wozniak et al. now find that the small GTPase Rho and its effector, ROCK, are essential for the cells to pull against the matrix and to respond to the resistance encountered.

^{The breast epithelial cells attach to their collagenous matrix via...}