p53 status in multiple human urothelial cancers: Assessment for clonality by the yeast p53 functional assay in combination with p53 immunohistochemistry

Multifocal synchronous or metachronous tumor development is a common observ ation in human urothelial cancer cases. However, the underlying mechanism h as remained obscure. We have employed a new tool to investigate the p53 gen e status, the yeast p53 functional assay, in combination with immunohistoch emistry in a total of 50 tumor samples from 32 cases with urothelial cancer s, including 8 with multiple synchronous tumor development and 2 demonstrat ing metachronous tumors. p53 mutations were found in 13 cases (9 with misse nse mutations, 3 with deletion, 1 with splicing mutation) by the yeast p53 functional assay, p53 protein overexpression was seen in all 9 cases with m issense mutations, but in only one of the 4 cases with nonsense mutations. Two tumors without p53 mutation also showed positive p53 immunoreactivity, Overall, p53 abnormalities including mutations and/or protein overexpressio n were found in 15 (47%) cases. p53 abnormalities were significantly more f requent in non-papillary and in high grade tumors. Loss of the wild type al lele in addition to a p53 mutation was suggested in 8 of the 15 (53%) cases . All 4 cases with mutations in multiple synchronous tumors had identical p 53 mutations in the separate urothelial cancers, strongly suggestive of mon oclonality, The one case with multiple metachronous tumors, in contrast, wa s characterized by variation in the p53 status, indicative of different clo nal origins, In conclusion, combined assessment for p53 status as used here (yeast p53 functional assay plus immunohistochemistry) may provide insight s into the molecular mechanisms of urothelial carcinogenesis.