Different mechanisms of extracellular matrix remodeling by fibroblasts in response to human mammary neoplastic cells.

Human breast tumors are often associated with a fibrotic reaction termed desmoplasia. Tumor cells may indirectly modulate the composition of the extracellular matrix by influencing fibroblast properties. They may also directly interact with collagen fibrils leading to retraction of the matrix. We have studied in vitro the influence of various human mammary tumor cells on the proliferation rate of normal human fibroblasts and on their level of collagen synthesis, as well as their release of collagenase activity. Interactions between neoplastic cells and collagen matrix were investigated by incorporation of tumor cells in collagen gels (lattices) and measurement of their retraction. All cells tested (HBL100, SW613, SA52, MDA-MB-231, MCF7, MCF7/6, MCF7 ras, BT20 and T47D) were able to modulate the composition of the extracellular matrix by one or several of the mechanisms investigated. Our results also demonstrate an opposite regulation of collagen and collagenase production. The effects on the collagen metabolism and on fibroblast proliferation are probably mediated by soluble cytokines since they are reproduced by incubating the fibroblasts in the presence of medium conditioned by tumor cells. The desmoplastic reaction may thus result from different mechanisms dependent upon tumor cell types.