PRIMARY HUMAN PROSTATE-CANCER CELLS HARBORING P53 MUTATIONS ARE CLONALLY EXPANDED IN METASTASES

Recent studies suggest a role for p53 in prostate cancer progression, Although p53 mutations in primary prostate cancer tissues are relative ly infrequent, they occur at significant levels in metastatic disease, Here we describe a novel approach to the molecular analysis of p53 in paired specimens of primary and metastatic prostate cancer that resul ts in quantitative estimates of the extent of clonal expansion. In 20 pairs with 1 or both specimens p53 immunopositive and in 6 pairs with both specimens immunonegative, the frequency of mutations was estimate d by microdissection of the cancer from fixed and sectioned tissues, i solation of the DNA followed by PCR amplification of p53 genomic fragm ents, and cloning of the PCR products into plasmid vectors, At least 9 0 clones/tissue specimen were screened for mutations by single-strand conformational polymorphism analysis, DNA from abnormally migrating si ngle-strand conformational polymorphism samples was sequenced to confi rm mutations, Missense mutations in exon 5, 7, or 8 mere detected in 9 of 20 immunopositive pairs and in 1 of 6 immunonegative pairs, A mark ed heterogeneity of mutations in primary prostate cancer was apparent, The frequency of p53 mutations was greater in the metastases than in the primary tumors, In three immunopositive pairs, the same p53 mutati on was demonstrated at a low frequency in the primary tumor but was de monstrated at a greater frequency in the metastasis, indicating relati vely limited clonal expansion of cells harboring specific p53 mutation s in the primary tumor, get significant clonal growth at metastatic si tes as determined by this novel method.