P53 IN PROSTATE-CANCER - FREQUENT EXPRESSED TRANSITION MUTATIONS

Background: Carcinoma of the prostate is the second most common cause of cancer deaths in men. Little is known about the pathogenesis of thi s disease and the molecular genetic events that contribute to its deve lopment. Molecular studies have begun to reveal biologic characteristi cs of this disease, notably, the loss of genetic material as determine d by studies of restriction fragment length polymorphism, oncogene act ivation, and production and response to growth factors. Purpose: Our g oal was to characterize p53 gene mutations in human carcinoma of the p rostate and to analyze base-pair changes within the coding regions of p53 mRNA (exons 4 through 11). Methods: Forty-four prostate tissue spe cimens and four metastatic lesions were obtained from 48 prostate carc inoma patients who had surgical resection. RNA was either immediately extracted or the specimens were snap-frozen in liquid N-2 and stored a t -70 degrees C until used. Total RNA was extracted from tumor specime ns. Expression of p53 was analyzed by polymerase chain reaction (PCR) analysis of mRNA (RNA/PCR). Following confirmation of the RNA/PCR prod ucts by Southern blotting, quantitation of message levels was performe d by laser densitometry. Absolute area integrations of the curves repr esenting each tissue mere then compared after adjustment for the house keeping gene c-N-ras. Two overlapping regions (exons 4-6 and 6-11) wer e examined by a nonisotopic PCR single-strand conformation polymorphis m (SSCP) analysis system. All specimens displaying SSCP abnormalities were sequenced in both directions to confirm the findings. Results: Of the 48 prostate specimens, three (6%) (two primary and one metastatic ) displayed nearly undetectable expression of p53 mRNA (samples PS-70, L113, and PS-95) and 17 (35%) of 48 expressed mutant p53 mRNA encodin g amino acid substitutions within exons 4-11 (14 of 17) and/or deletio ns within the p53 transcripts (three of 17). Overall, the frequency of p53 gene abnormalities that would result in altered protein expressio n was 20 (42%) of 48 in the tissue samples from prostate carcinoma pat ients. Nucleotide base-pair transitions of A-->G or T-->C were the mos t frequent. Conclusions: p53 mutations are common in prostate cancer. The patterns of p53 gene mutations are dramatically different from dat a obtained on other cancers and indicate the possible involvement of a carcinogenic agent(s). Implications: Further studies are required to determine the biologic role of p53 gene alterations in the development and progression of this disease and to determine whether p53 mutation s can be useful as prognostic markers or for the selection of better t reatments for prostate cancer patients.