Autocrine/Paracrine Secreted Frizzled-related Protein 2 Induces Cellular Resistance to Apoptosis A POSSIBLE MECHANISM OF MAMMARY TUMORIGENESIS*

Abnormal regulation of apoptosis and cell prolifera-tion is thought to be involved in tumor formation. The secreted Frizzled-related protein 2 (SFRP2) was de-tected in primary culture of canine mammary gland tu-mors but not in normal mammary tissues. Thus, to elu-cidate the role of SFRP2 in mammary tumorigenesis, we overexpressed SFRP2 in mammary gland tumor and MCF7 cells. The results indicated that SFRP2 is secreted and incorporated into the extracellular matrix (ECM) of the tumor and normal cells. In an attempt to understand the molecular basis underlying the interaction between SFRP2 and ECM, co-immunoprecipitation and cell ad-hesion assays were carried out. SFRP2 was found to be associated with the fibronectin-integrin protein com-plex and could promote cell adhesion. DNA fragmenta