Syndecan-1 is a single-pass type I membrane protein that belongs to the syndecan proteoglycan family. The syndecans mediate cell binding, cell signaling, and cytoskeletal organization and syndecan receptors are required for internalization of the HIV-1 tat protein. Human SDC1 is synthesized as a 310 amino acid precursor that contains a 22 amino acid signal sequence, and a 288 amino acid mature chain. The Syndecan-1 protein functions as an integral membrane protein and participates in cell proliferation, cell migration and cell-matrix interactions via its receptor for extracellular matrix proteins. Altered Syndecan-1 expression has been detected in several different tumor types.