Tissue proteins in breast cancer, as studied by use of two-dimensional electrophoresis.

Proteins from 25 specimens of malignant breast tissue were separated by "high-resolution" two-dimensional gel electrophoresis. The number of polypeptide spots detectable in individual gels varied from 259 to 471 (mean 347; SD 68) per milligram of wet tissue. Many polypeptide spots were not consistently present in all malignant tissues. Ten different in vivo polypeptides, observed neither in five non-malignant breast tissues nor in human milk, were present in more than 22 of the 25 cases of breast tumor tissues examined. Five of these polypeptides appeared to be identical to five in vitro polypeptides found in separations from cultured human ductal carcinoma cells. Further studies are required to verify the specificity of these tumor-associated proteins before they can be considered for breast tumor-specific in vitro diagnostic testing or targeting in selective in vivo anti-cancer therapy.