These results suggest that if tumor-secreted MMP-1 contributes to the metastatic phenotype of breast and prostate cancer cells, and is regulated by RANKL-RANK pathway, there may be a novel opportunity for the indirect targeting of MMP-1 in bone metastases by targeting the bone microenvironment, namely RANKL. The gene discussed is TNFRSF11A; the disease is prostate carcinoma.