c-myc gene product in rat azo-dye-induced hepatocarcinogenesis

Changes of c-myc gene-product levels were examined in liver extracts of rats having 3'-methyl-4-diaminoazobenzene-induced rat hepatocarcinogenesis, using an antibodies directed against a synthetic pentadecapeptide corresponding to the C-terminal 423-437 sequence of the predicted c-myc oncogene protein. After a 4 weeks treatment with 3'-methyl-4-diamino azobenzene (3'-Me-DAB), c-myc oncogene product-like immunoreactivity (c-myc-P-IR) was significantly increased as demonstrated by radioimmunoassay of rat liver extracts. In addition, immunohistochemical results of surviving and regenerating hepatocytes of 3 weeks and thereafter of 3-DAB-treated rats supported observations obtained by the radioimmunoassay. Hepatocytes of hyperplastic foci or neoplastic nodules were immunostained at about 80% in frequency. Foci of atypical hepatocellular proliferation less than 1 mm in diameter, which appeared from the 21st week after the start of treatment, harbored no or if present, a few immunoreactive cells, at 2.6% in frequency. Larger foci of atypical hepatocytes including cancer nodules had few or no immunoreactive cells. The present immunochemical approach which makes use of a synthetic peptide related to a functional protein (i.e. c-myc protein) is a worthwhile technique for detection of a wide range of functional proteins.