Pigment epithelium‐derived factor upregulates collagen I and downregulates matrix metalloproteinase 2 in osteosarcoma cells, and colocalises to collagen I and heat shock protein 47 in fetal and adult bone

Abstract Objective Pigment epithelium‐derived factor ( PEDF ) has proven anti‐osteosarcoma activity. However, the mechanism(s) underpinning its ability to reduce primary bone tumour (osteosarcoma) metastasis is unknown. Methods Adult and fetal murine bone were immunostained for PEDF , collagen I (major protein in bone) and its processing proteins, heat shock protein 47 ( HSP 47, a chaperone protein for collagen I ), membrane type I matrix metalloproteinase ( MT 1‐ MMP , a collagenase), and matrix metalloproteinase 2 ( MMP ‐2, which is activated by MT 1‐ MMP ). Immunoblotting and immunocytochemistry were used to observe levels of the above biomarkers when human osteosarcoma cells were treated with PEDF . Key findings Immunohistochemical staining in adult and fetal bone mirrors collagen I . PEDF localised to ridges of trabecular bone in tibial cortex and to megakaryocytes within bone marrow. Second, we observed that PEDF upregulates collagen I , HSP 47 and MT 1‐ MMP , while downregulating MMP ‐2 in osteosarcoma cells in vitro . Conclusion PEDF is a promising antagonist to osteosarcoma cell metastasis via downregulation of MMP ‐2, and can induce tumour cells to further adopt differentiative properties, thereby possibly reducing their aggressive growth in vitro and in vivo .