Detection and Measurement of α-Fetoprotein in Human Breast Cancer Cytosol after Treatment with 0.4 m Potassium Chloride

The mean concentration of total α-fetoprotein (AFP) measured in 51 primary breast cancer cytosols from postmenopausal women by radioimmunoassay after treatment with 0.4 m KCI was 87.2 IU AFP per ml. Little or no AFP was measured in these same cytosols before KCI treatment. After labeling KCI-treated human breast cancer cytosols with ¹²⁵I, double immunodiffusion, immunoelectrophoresis, and autoradiography revealed that radiolabeled AFP codiffused and comigrated with α₁ electrophoretic mobility in a manner identical to that of added carrier cord serum AFP. These results indicate that human breast cancer cytosol contains appreciable amounts of a previously undetected AFP component that was initially nonimmunoreactive but became immunoreactive and measurable after KCI treatment. No positive correlation was found between the initial estrogen receptor content and AFP concentrations measured either before or after KCI treatment of breast cancer cytosols.