[p53 overexpression as independent prognostic marker in soft tissue sarcomas is antibody dependent]

Most changes in p53 result in a protein with prolonged half life. This permits immunohistochemical detection. P53-overexpression seems to have prognostical relevance in soft tissue sarcomas (STS). The goal of this study was to compare the prognostic relevance of five different p53 antibodies in immunohistochemistry of primary STS using a Cox regression model with adjustment to staging, localization, tumor type, and surgical therapy. We investigated 198 primary STS of six different tumor types for p53-overexpression using the antibodies DO-1, DO-7, Pab1801, Pab240, and CM-1. The rate of positivity (cut of point 10% positive tumor cells) was between 36.2% and 62.6% dependent on the applied antibody. Prognostic significance could be determined only for the N-terminal binding monoclonal antibodies (DO-1, p = 0.0014; DO-7, p = 0.005; Pab1801, p = 0.02) with the highest level for combination of DO-7 and Pab1801 positivity (RR = 2.57, p = 0.0098). Pab240 (epitope amino acids 213-217) and CM-1 (polyclonal) showed no prognostic relevance in the multivariate analysis. We therefore suggest that for immunohistochemical evaluation of p53-overexpression in STS a pannel of two N-terminal antibodies should be used at least.