DETECTION OF RB, P16 CDKN2 AND P15(INK4B) GENE ALTERATIONS WITH IMMUNOHISTOCHEMICAL STUDIES IN HUMAN PROSTATE CARCINOMAS/

To examine the status of cell cycle-inhibitory genes in human prostate carcinoma, we investigated alterations of RE (retinoblastoma), p16/CD KN2 and p15(INK4B) genes in 32 adenocarcinomas with immunohistochemist ry. PCR-single-strand conformation polymorphism (SSCP) was used to exa mine all 27 exons of the RE gene, exons 1 to 3 of the p16/CDKN2 gene a nd exons 1 and 2 of the p15(INK4B) gene for mutations. Loss of heteroz ygosity (LOH) for the RE gene was probed by restriction fragment lengt h polymorphism (RFLP) analysis. In addition, coordinate samples were s ubjected to immunohistochemical studies for reactivity to RE and p16 p rotein. The RE gene alterations were detected in 5 of the 32 tumors (1 6%); of these, only one mutation, a missense substitution, occurred wi thin an exon. The remaining four single base insertions or deletions w ere found within introns of the RE gene and no mutational event was de tected in its promoter region. LOH involving intron 17 of RB was detec ted in three cases of 10 informative tumors (30%). Intragenic mutation s were also present in 3 of the 32 tumors in the p16/CDKN2 gene. In co ntrast, no mutational events were found in the p15(INK4B) gene in the tumors. Only one tumor had both a p16/CDKN2 mutation and LOH of the RE gene. Expression of pRB was absent or reduced in 16 cancers, while p1 6 expression was present in all cases to varying degrees. The results suggest that p16/CDKN2 gene mutations occur rarely and intragenic muta tion, but not LOH,of the RE gene is not required in prostatic tumorige nesis.