Bone extracellular matrix stimulates invasiveness of estrogen-responsive human mammary MCF-7 cells

Bone is the most frequent site of metastasis in breast cancer. This causes destructive osteolytic lesions. To achieve metastasis to bone, breast cancer cells must proliferate in a new microenvironment, arrest on extracellular matrix and invade. Breast cancer cells progress in the invasive processes only if they destroy bone with the assistance of osteoclasts. In this work, we present data suggesting that MCF-7 cells, an estradiol receptor-positive cell line that exhibits modest invasive capacity, proliferate in the presence of soluble factors secreted by the osteogenic cell line SaOS-2. The cells acquire a more aggressive phenotype when cultured on an extracellular matrix produced by the same osseous cell line. Acquisition of the invasive phenotype appears to be related to the capacity of bone extracellular matrix to induce the expression of urokinase-like plasminogen activator by MCF-7 cells, which is specific for MCF-7 cells, given that MDA-231 cells, an estradiol receptor-negative and more aggressive cell line, did not show significant changes when cultured in the presence of soluble and insoluble bone factors.