Secreted Frizzled Related Proteins (sFRPs) modulate WNT signaling by binding directly to WNT proteins in a manner that affects their receptor binding and signaling capabilities. sFRP-1 is a widely distributed protein that can bind directly to WNT1, WNT2, and possibly other WNT proteins, and generally exerts anti-proliferative effects consistent with activity as a WNT antagonist. It also inhibits apoptosis, and has been found to be down-regulated in many solid tumors, but up-regulated in uterine leiomyomas. Recombinant Human sFRP-1 is a glycosylated 283 amino acid protein containing a cysteine-rich Frizzled homologous domain. The calculated molecular weight of Recombinant Human sFRP-1 is 32.5 kDa.