ECM determines fate

Biologists long thought that the extracellular matrix (ECM) provided only support and protection for cells. But from the early 1980s on, Mina Bissell of the Lawrence Berkeley Laboratory in California contended that the ECM was a prime influence on cells, transmitting signals that direct gene expression and differentiation (Bissell et al., 1982). A 1991 paper from her lab (Streuli et al., 1991) clinched the case for this view, showing that single mammary cells growing in ECM could fashion a milk protein without stimulation from other cells. Later studies from her group identified the signal-sending component of ECM and revealed how it affected cancer cells.

By 1991, Bissell's lab and others had demonstrated that mammary cells reared on basement membrane, the ECM underlying epithelial layers, form bulbs—just like those that abound in...