Periostin was originally isolated as an osteoblast-specific factor that functions as a cell adhesion molecule for pre-osteoblasts and is thought to be involved in osteoblast recruitment, attachment and spreading. Additionally, periostin expression has previously been shown to be significantly increased by both transforming growth factor beta1 (TGF-beta1) and bone morphogenetic protein 2 (BMP-2). Abnormal expression of periostin is also linked to angiogenesis and metastasis in epithelial tumors.