Protein expression of p53, bcl-2, and KI-67 (MIB-1) as prognostic biomarkers in patients with surgically treated, clinically localized prostate cancer

Abstract

Background: Protein expression in the primary tumor of the tumor suppressor gene p53 and the proto-oncogene bcl-2 have been shown to be prognostic biomarkers of cancer recurrence after radical prostatectomy in patients with clinically localized prostate cancer. Cancer cell proliferation as measured by immunohistochemical markers such as the MIB-1 antibody for Ki-67 has recently been suggested to be of prognostic value in prostate cancer. The goal of this study was to determine the clinical use of p53, Ki-67 (MIB-1), and bcl-2 immunohistochemical protein expression in the primary tumor as combined predictors of disease progression after radical prostatectomy (RP).

Methods: Protein expressions of p53, Ki-67, and bcl-2 were evaluated in archival paraffin-embedded RP specimens from 162 patients monitored from 1 to 10 years (mean, 4.5 years) and correlated to stage, grade, race, and serologic (prostate-specific antigen) recurrence after operation.

Results: Expression was detected in 112 (69.1%), 44 (27.2%), and 62 (38.3%) of 162 patients for p53 (1+ or greater), bcl-2 (1+ or greater), and Ki-67 (2+ or greater), respectively. Biomarker expressions were not correlated to age and race; however, all increased with increasing stage and grade. The degree of expression by percentage of malignant cells staining correlated to recurrence for p53 and Ki-67 but not for bcl-2. All three markers were correlated to raw and Kaplan-Meier recurrence by means of univariate analysis with recurrence estimates at 6 years of 60.7% versus 24.2%, 84.2% versus 38.6%, and 72.4% versus 30.6% comparing positive versus negative expression of p53, bcl-2, and Ki-67, respectively. p53 and bcl-2 remained as independent prognostic markers by Cox multivariate regression analysis. Although Ki-67 did not remain an independent marker, it added prognostic use in certain subsets of patients.

Conclusions: p53, bcl-2, and Ki-67 (MIB-1) appear to be important biomarkers to predict recurrence in patients with clinically localized prostate cancer after RP, and all three biomarkers deserve further study.