Ectopic production of placenta-"specific" tissue proteins (PP5 and PP11) by malignant breast tumors

With use of an enzyme-bridge immunoperoxidase (PAP) technique, an immunohistochemical localization of the two new placenta-"specific" tissue proteins, PP5 and PP11, was investigated in 16 cases of breast cancer. PP5 was localized in the cytoplasm of breast cancer cells in 62.5% of cases examined and PP11, in 46.7%. Thus PP5 and PP11 may be markers for breast cancer and the detection of these proteins in sera from breast cancer patients may be more reliable and useful in the detection and monitoring of breast cancer patients than the determination of SP1, PP10, or PP12, other pregnancy "specific" proteins.