Detection and measurement of alpha-fetoprotein in human breast cancer cytosol after treatment with 0.4 M potassium chloride.

The mean concentration of total alpha-fetoprotein (AFP) measured in 51 primary breast cancer cytosols from postmenopausal women by radioimmunoassay after treatment with 0.4 M KCl was 87.2 IU AFP per ml. Little or no AFP was measured in these same cytosols before KCl treatment. After labeling KCl-treated human breast cancer cytosols with 125I, double immunodiffusion, immunoelectrophoresis, and autoradiography revealed that radiolabeled AFP codiffused and comigrated with alpha 1 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 KCl treatment. No positive correlation was found between the initial estrogen receptor content and AFP concentrations measured either before or after KCl treatment of breast cancer cytosols.