Tissue rigidity might help promote tumor progression, scientists report today in this month's Cancer Cell. These findings help demonstrate how stiff surfaces can lead to malignant growth, and could help explain why continued culturing of normal cells for many passages on rigid plastic dishes often leads to spontaneous transformation, Don Ingber at Harvard Medical School, who did not participate in this study, told The Scientist.

Tumors are stiffer than normal tissue. To determine if that stiffness contributes to a tumor's malignancy, Valerie Weaver at the University of Pennsylvania in Philadelphia and her colleagues added cells to a three-dimensional gel culture designed to mimic the extracellular matrix, made of synthetic acrylamide or a mix of natural basement membrane and collagen. The researchers increased stiffness of the matrix by boosting either acrylamide cross-linking or collagen levels. When normal mammary epithelial cells were raised in a culture whose stiffness matched a...