Abstract: Methods and composition for detecting the presence of human ras oncogene related malignancies are provided, where a biological sample is assayed for protein(s) specific to a DNA sequence. In the methods of this invention, the test reaction involves admixing a biological sample from cancer patients or control donors with labelled ras oncogene promoter DNA. The admixture is incubated under conditions favorable for promoting specific interactions between proteins and the labelled DNA. Thereafter, the admixture is separated by charge and size in an electrophoretic field and the protein-DNA interactions are identified depending on the method of label employed. Bands migrating at a slower rate than the uncomplexed DNA are indicative of a protein-DNA interaction (i.e. circulating serum protein(s) from cancer patients interacting specifically with a region(s) of the ras oncogene promoter DNA).