AbstractBACKGROUNDp73 and p51 are genes possessing amino‐acid similarities to p53. We previously found no mutation in p73 in prostatic carcinoma, but did find abnormal expression of the gene. Involvement of these genes in prostatic carcinogenesis is still poorly understood.METHODSMutation analysis of the p51 gene and allelotyping of 3q28, on which p51 lies, were performed. Expression of p53, p73, and p51 was examined using reverse transcription–polymerase chain reaction, and expression levels were compared.RESULTSNo mutation in p51 was found (0/55 cases). Loss of heterozygosity at 3q28 was detected in 6 of 28 cases (21.8%). By expression analysis we found that in p53, 4 of 38 cases (10.5%) showed downregulation. No cases showed upregulation of p53. In contrast, p73 and p51 were downregulated in 42.1 and 39.5% of cases, respectively, and upregulated in 31.5 and 34.2% of cases, respectively. Expression levels of p51 corresponded with those of p73 in 25 of 38 cases (65.8%).CONCLUSIONSSomatic mutations in p73 and p51 are not important in prostatic carcinogenesis. These genes may be associated with tumors by expression levels and may have roles in addition to tumor suppresson. Prostate 47:85–90, 2001. © 2001 Wiley‐Liss, Inc.