S100A4 and neoplasm: To resolve this issue, we recently performed a siRNA-mediated S100A4 knockdown in endothelial cells and revealed a critical role of endothelial S100A4 in in vitro tube formation as well as in tumor angiogenesis in a xenograft cancer model,27 highlighting endothelial S100A4 as a molecular target for inhibiting tumor angiogenesis.