S100A4 and neoplasm: The role of PTHrP in bone metastasis is multifaceted; the autocrine action of PTHrP promotes the proliferation, survival, invasion, and migration of tumor cells, while the paracrine and endocrine action of PTHrP modulates bone-metastatic environments.21 The primary mechanism by which PTHrP modulates the bone microenvironment seems to be indirect stimulation of osteoclastogenesis via induction of RANKL in osteoblasts and osteocytes.21 This indirect mode of action appears to be distinct from the direct stimulation of osteoclastogenesis by S100A4 in our present study.