[A novel oncogene from a human hepatocellular carcinoma]

Primary human hepatocellular carcinomas (HCC) were surveyed for oncogenes by transformation assays using NIH3T3 cells and the calcium phosphate coprecipitation method. High-molecular-weight DNA obtained from the HCC tissues was employed for this purpose. One new transforming DNA, named lca (for liver cancer) was obtained, and its properties were studied in detail. This transforming DNA had a linkage to the Alu sequence and was cloned in lambda phage. Restriction enzyme analyses showed that the minimum size of the lca DNA is about 10.5 kilobase pairs and that its nucleotide sequence is different from that of any known human gene or retroviral oncogene. Southern blot analyses of DNAs from flow-sorted human chromosomes and human-mouse somatic cell hybrids indicated that the lca DNA is located on human chromosome 2. It showed identical restriction enzyme cleavage profiles with its counterpart DNA obtained from normal tissue, indicating that there is no extensive DNA rearrangement associated with the activation process of the lca DNA. The normal counterpart DNA shows no transforming activity. An independently obtained transforming DNA from another HCC exhibited identical restriction enzyme cleavage profiles. Thus, lca DNA is likely to represent a commonly encountered transforming DNA in HCC.