A novel clonality assay for the mouse: application to hepatocellular carcinomas induced with diethylnitrosamine

A polymerase chain reaction-based clonality assay was developed for mouse tumors and cellular proliferations of the mouse. This assay was based on a polymorphism of the phosphoglucokinase-1 (Pgk-1) gene on the X chromosome between two different mouse subspecies and the different methylation patterns of active and inactive X chromosomes. All 15 tumor cell lines examined showed one of the two allelic bands on gel electrophoresis, which is consistent with the theory that tumor cell lines are monoclonally derived. This suggests that the Pgk-1 system is useful for clonality studies that will give insight into cancer development. With this method, nine hepatocellular carcinomas were examined, and eight showed monoallelic patterns. The remaining tumor exhibited a biallelic pattern, which is suggestive of polyclonal origin; however, other possibilities are discussed.