Purpose: To investigate the frequency and prognostic significance of genetic alterations in incidentally diagnosed, transitional zone prostate cancer.
Materials and methods: Twenty-six incidentally diagnosed, transitional zone cancers were examined by the PCR for genetic alterations on chromosomes 8p and 13q and by immunohistochemistry for alterations of the expression of the cell-cycle regulatory proteins RB1 and p53 and of the cell adhesion molecules E-cadherin and alpha-catenin.
Results: All of the tumors had at least one molecular abnormality (median 2.0 range 1 to 4). Allelic loss on 8p occurred in 37% and on 13q in 50% of informative tumors. Abnormal expression of pRb was found in 67%, of p53 in 33%, of E-cadherin in 36% and of alpha-catenin in 43%. In addition microsatellite instability was found in 23% of tumors. Only loss of expression of alpha-catenin was found to have prognostic importance.
Conclusions: Genetic alterations were common, but, apart from alpha-catenin, did not appear to be related to tumor progression. The lack of prognostic significance is likely to be due to the multifocal nature of prostate cancer, but may also relate to qualitative differences between transitional zone and peripheral zone prostate cancers.