Myofibroblast and concurrent ED-B fibronectin phenotype in human stromal cells cultured from non-malignant and malignant breast tissue

Primary cultures of stromal cells from non-malignant and malignant breast tissues contained myofibroblasts based on immunoreactivity to α-smooth muscle (α-sm) actin. The proportions of these cells were variable among cultures from non-malignant origin while consistently high in cultures from carcinomas. High expression of ED-B fibronectin and of type V collagen was observed in myofibroblast-containing cultures. While cells from non-malignant tissues grew relatively steadily, the proliferation of carcinoma-derived cells declined during serial subculturing. In both types of cultures, α-sm actin and Ed-B fibronectin expression decreased with increasing passage numbers. Epidermal growth factor (EGF), fibroblast growth factor b (FGFb), transforming growth factor α (TGFα) and platelet-derived growth factor (PDGF) showed consistent mitogenic effects. Addition of FGFb prolonged culture growth and allowed α-sm actin and ED-B fibronectin expression to persist. These results demonstrate similar phenotypic modulations in stromal cells from non-malignant and malignant breast tissues that may reflect a common stromal response to various tissue injuries, including neoplasia.