Overexpression and Amplification of the c‐myc Gene in Mouse Tumors Induced by Chemicals and Radiations

We examined expression of the c‐myc gene by the dot blot hybridization of total cellular RNA from mouse primary tumors induced by chemicals and radiations. Expression of the c‐myc gene was found to be elevated in 69 cases among 177 independently induced tumors of 12 different types. DNA from tumors overexpressing the myc gene was analyzed by Southern blotting. No case of rearrangement was detected. However, amplification of the c‐myc gene was found in 7 cases of primary sarcomas. These included 4 cases out of 24 methylcholanthrene‐induced sarcomas and 3 cases out of 7 α‐tocopherol‐indnced sarcomas. We also analyzed 8 cases of sarcomas induced by radiations, but could not find changes in the gene structure of the c‐myc gene. Thus, our data indicate tumor type specificity and agent specificity of c‐myc gene amplification.