Regulation of mammary gland branching morphogenesis by the extracellular matrix and its remodeling enzymes

A considerable body of research indicates that mammary gland branching morphogenesis is dependent, in part, on the extracellular matrix, affecting cell survival, polarity, proliferation, differentiation, adhesion, and migration. However, the precise mechanisms of ECM-directed mammary morphogenesis are not well understood and is discussed in this review. Mammary morphogenesis involves epithelial invasion of adipose tissue, a process akin to invasion by breast cancer cells, although the former is a highly regulated developmental process. How these morphogenic pathways are integrated into the normal gland and how they become dysregulated and subverted in the progression of breast cancer also remain largely unanswered questions.