Soluble frizzled-related proteins (sFRPS) function as modulators of Wnt signaling through direct interaction with Wnts. They have a role in regulating cell growth and differentiation in specific cell types. SFRP1 decreases intracellular beta-catenin levels (By similarity). Has antiproliferative effects on vascular cells, in vitro and in vivo, and can induce, in vivo, an angiogenic response. In vascular cell cycle, delays the G1 phase and entry into the S phase (By similarity). In kidney development, inhibits tubule formation and bud growth in metanephroi (By similarity). Inhibits WNT1/WNT4-mediated TCF-dependent transcription. Interacts with WNT1, WNT2 and FRZD6. Interacts with WNT4, WNT8 and MYOC (By similarity). Cell membrane or extracellular matrix-associated. Released by heparin-binding. Widely expressed. Absent from lung, liver and peripheral blood leukocytes. Highest levels in heart and fetal kidney. Also expressed in testis, ovary, fetal brain and lung, leiomyomal cells, myometrial cells and vascular smooth muscle cells. Expressed in foreskin fibroblasts and in keratinocytes. Down-regulated in colorectal and breast tumors. Up-regulated in uterine leiomyomas under high estrogenic conditions. Expression, in leiomyomal cells, also increased both under hypoxic and serum deprivation conditions. The FZ domain is involved in binding with Wnt ligands. May have therapeutic use in cardiac surgery. Belongs to the secreted frizzled-related protein (sFRP) family.