WNT pathway and mammary carcinogenesis: Loss of expression of candidate tumor suppressor gene SFRP1 in most invasive carcinomas except of the medullary type

Secreted Frizzled-related protein 1 (SFRP1) encodes a member of a protein f amily that contains a cysteine-rich domain similar to the WNT-binding site of Frizzled receptors and regulates the WNT pathway. The WNT pathway is fre quently altered in human cancers. We have defined the pattern of SFRP1 mRNA expression in the progression of breast cancer. We show that SFRP1 is expr essed in the epithelial component of normal breast, in the in situ componen t of ductal carcinomas and is lost in more than 80% of invasive breast carc inomas except the medullary type. Loss of SFRP1 expression is correlated wi th the presence of hormonal receptors. Conversely, the maintenance of SFRP1 in carcinomas is correlated with the presence of lymphoplasmocytic stroma. No significant association was observed between SFRP1 status and the level of apoptosis in tumoral cells.