Runt-related gene 2 in endothelial cells: Inducible expression and specific regulation of cell migration and invasion

Understanding the regulation of endothelial cell (EC) gene expression has i mportant implications for angiogenesis, tumor growth, and metastasis. The t ranscription factor runt-related gene 2 (RUNX2)/core binding factor alpha - 1/afute myeloid leukemia 3/polyoma enhancer-binding protein 2 alphaA/osteob last-spefific transcription factor 2 regulates osteoblast differ; entiation , increases lymphomagenesis in transgenic mice, and is expressed in murine ECs. Here, we report on RUNX2 expression in human bone marrow EC (HBME-1) a nd ifs role in EC differentiation. Expression of RUNX2 occurred in HBME-1 c ultured on extracellular matrix (ECM substrates that stimulate irt vitro di fferentiation (tube formation). Neutralizing anti-insulin-like growth facto r (IGF)-I-receptor antibody inhibited tube formation as well as activation of RUNX2 expression in HBME-1 cultured on ECM. IGF-I treatment also increas ed both RUNX2 mRNA and protein expression. HBME-1 transfectants expressing dominant-negative (DN) RUN were established to address the role of RUNX2 in these processes. HBME/DN cells exhibit ed reduced tube formation activity relative to control transfectants and less ability to growth arrest and dif ferentiate on ECM. DNRUNX expression also inhibited HBME-1. migration and i nvasion, which are necessary for tube formation. The urokinase-type plasmin ogen activator and membrane-type MMP-1 genes were consistently down-regulat ed in DNRUNX transfectants. The results suggest that RUNX2 is important in IGF-I and ECM-regulated EC migration and differentiation. RUNX2 effects on HBME-1 migration and invasion may occur through activation of? protease exp ression, events that regulate angiogenesis, and tumor growth.