Correlation of genetic and immunodetection of TP53 mutations in malignant and benign prostate tissues

The prognostic value of the p53 gene (TP53), the most commonly mutated gene in human cancers, has been well established for several cancer types. However, because varying frequencies of TP53 mutations have been identified in prostatic adenocarcinoma (CaP) by genetic and immunohistochemical (IHC) studies, the role of TP53 in CaP tumorigenesis is currently unresolved. These experimental discrepancies could be caused by tissue heterogeneity within prostatic neoplasms, variations in experimental protocols, or other factors. Thus, the goal of this study was to develop a reliable IHC approach for the detection of p53 in archival prostate tissue. The authors evaluated four p53 antibodies, CM-1, 1801, DO-1, and DO-7, for their ability to reveal p53. They chose two reference CaP cell lines, 26 patient specimens (including eight benign prostatic hyperplasias (BPHs), 16 CaPs, and two lymph node metastases), one prostate and nine kidney cell lines for p53 analysis. The TP53 status of these samples was characterized using single-strand conformational polymorphism (SSCP) analysis of RNA/PCR products and sequencing. IHC detection of p53 was markedly enhanced by using the combination of microwave heat-induced antigen unmasking and a cocktail of the DO-1 and DO-7 antibodies. This approach identified 14 of 15 (93%) cell lines and patient samples having TP53 missense mutations in the exons 5 to 8 region. Of the 21 patient samples and cell lines that were either normal by SSCP or expressed p53 mutations that are not expected to stain, 18 (86%) were immunonegative. Because of this good correlation between molecular and IHC analysis, this approach may help to resolve the uncertainty about TP53 in CaP tumorigenesis.