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.

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Allelic expression was examined by single‐strand conformation polymorphism analysis in murinc fibrosarcomas from inter‐subspecific F1 mice between C57BL/6 and MSM. Ten genes encoding p53, mdni2, E‐cadherin, 72 kD metalloproteinase and its inhibitor (Timp2), thymidine kinasc and four glucose transporters (Gluts) were examined. These genes were chosen because of their probable association with tumor development and progression. In some of the tumors and cell lines, p53, E‐cadherin and Glut3 genes showed remarkable differences in allelic expression, one allele being poorly expressed. The allele‐specificity persisted in nine cell lines obtained by repeated transplantations from one tumor. These results suggest that expression of some genes is allele‐specific in tumor cells and the pattern of specificity is stable. Such a decrease or a loss of expression in one of the alleles may be functionally equivalent to the loss of heterozygosity of the gene, and therefore this may confer malignant properties on tumor cells. It is also suggested that differential expression of two alleles is a common event in tumor cells.

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.

No abstract