The synthesis of the male rat hepatic protein .alpha.2U-globulin was examined in Morris hepatoma 5123D and male host liver using pulse incorporation of labeled amino acids in vivo, followed by immunoprecipitation of the newly synthesized .alpha.2U-globulin from the soluble protein fraction of liver and hepatoma tissue. No .alpha.2U-globulin synthesis occurs in hepatoma tissue, whereas host liver synthesizes .alpha.2U-globulin at a normal level (0.9-1.0% of total hepatic protein synthesis). A variety of liver derived cell culture lines also did not have .alpha.2U-globulin synthesis. The level of the specific mRNA coding for .alpha.2U-globulin can be quantitated using in vitro translation of polyadenylate-containing RNA in a Krebs II ascites [mouse] cell free translational system, followed by immunoprecipitation of the .alpha.2U-globulin synthesized in vitro. Using this technique, host liver contained .alpha.2U-globulin mRNA at normal levels, whereas hepatoma tissue contained no detectable mRNA coding for this protein. .alpha.2U-Globulin synthesis is deleted in the minimal deviation hepatoma 5123D as a consequence of the inability of that tissue to produce functional mRNA coding for .alpha.2U-globulin. The implications for the regulation of gene expression in malignant cells are discussed.