FREQUENCY AND CHARACTERIZATION OF P53 MUTATIONS IN CLINICALLY LOCALIZED PROSTATE-CANCER

Objectives. To determine the frequency of abnormal p53 expression and to characterize confirmed p53 mutations in tumors from patients with c linically localized adenocarcinoma of the prostate. Methods. p53 prote in nuclear accumulation was determined immunohistochemically in the in itial diagnostic tumor specimens from 37 patients with clinically loca lized prostate carcinoma. Two primary antibodies were used on all spec imens. Structural analysis of the p53 gene was performed using the met hods of polymerase chain reaction (PCR)/single-strand conformation pol ymorphism (SSCP) and DNA sequencing. Results. In 1 of the 37 (2.7%) tu mor specimens, intense p53 nuclear staining was demonstrated using eit her antibody PAb 1801 or CM-1. The staining in this case was heterogen eous, with approximately 40% of tumor nuclei staining for p53. This tu mor specimen was microdissected and DNA was extracted. Following PCR a mplification, abnormally migrating bands were noted on SSCP analysis o f exon 8. DNA sequencing confirmed the mutation as a C --> A transvers ion in codon 281 (asp --> glu). PCR/SSCP analysis of exons 5 through 8 was also performed for seven additional tumors that were negative for p53 nuclear accumulation by immunohistochemical (IHC) methods. All of these specimens demonstrated wild-type p53. Conclusions. The results of this study confirm and extend our previous findings that p53 mutati ons are rare in clinically localized adenocarcinoma of the prostate. I n detecting clonal p53 mutations, standard immunohistochemical techniq ue correlates reliably with structural p53 gene analysis of the evolut ionary conserved domains encompassing exons 5-8. Importantly, most rep orts have demonstrated that p53 mutations detected by IHC are a late s tep in the progression of prostate cancer and are associated with adva nced disease, dedifferentiation, and the acquisition of androgen indep endence.