Comparison of nuclear proteins from DMBA-induced mammary tumors and lactating mammary glands by polyacrylamide gel electrophoresis

Abstract

Nuclear proteins were extracted from purified nuclei of 7,12-dimethylbenz(a)anthracene (DMBA)-induced tumors and normal mammary glands of the rat by enzymatic treatment. Of the 34 bands indicated by onedimensional polyacrylamide gel electrophoresis of nuclear proteins, 6 appeared in high concentration in tumors but were found as traces or undetectable in normal glands; 6 others were clearly shown in the latter but were not detectable or greatly reduced in the former. Two-dimensional electrophoresis identified about 130 and 92 non-histone proteins in normal mammary and tumor cell nuclei respectively. Marked differences in spot density were noted especially in spots (M.W. × 10⁻³/pI) 100/5.7 and 200/5.5 of tumors and 28/7.1, 32/5.4, 36/5.4, 38/6.9, and 68/6.0 of normal tissue. The relationship between these nuclear proteins and the development of mammary tumors is also discussed.