Immunofluorometric assay of p53 protein versus sequencing of p53 exons 5 to 9 for the detection of p53 abnormalities in ovarian carcinoma.

p53 alteration, detected as mutation of the p53 gene or as accumulation of mutant p53 protein, is a common feature of most malignancies, including ovarian carcinoma, and may identify patients with unfavorable prognosis and resistance to chemotherapy. Tumor tissues from 55 patients with well or poorly differentiated (grades 1 or 3) primary epithelial ovarian carcinoma were assessed both for p53 protein overexpression by a sensitive time-resolved immunofluorometric assay employing DO-1 and CM-1 antibodies, and for genetic p53 abnormalities by direct sequencing of PCR-amplified exons 5 to 9. Sixteen p53 mutations (29%), including 3 deletions causing frameshifts as well as one nonsense and 12 missense point mutations were found in all exons except exon 9. Overexpression of p53 protein, defined as a concentration exceeding the 75th percentile, was found in 15 cases (27%), 10 of which had missense mutations (P < 0.01). Tumors with nonsense and frameshift mutations were p53-negative by immunoassay. Both p53 mutation (P = 0.04) and p53 protein accumulation (P < 0.01) were associated with stage III-IV disease, while p53 mutation was more closely related to grade 3 lesions (P = 0.04) and serous histotype (P = 0.01). These results indicate that p53 protein accumulation correlates well with missense point mutation in carcinoma of the ovary and, together with other evidence that p53 abnormality may be prognostic of outcome in this disease, suggest that the immunoassay of p53 protein may have clinical value.