Dysregulated cell proliferation caused by inhibitors of programmed cell death (apoptosis) contributes to tumor progression and spread. Aberrant expression of Bcl-2, the most notable inhibitor of apoptosis, has been well characterized in several human malignancies. Recent studies have described a novel apoptosis inhibitor, survivin, in human carcinomas, although its exact role remains to be characterized.
The purpose of this study was to evaluate the immunohistochemical expression of Bcl-2 and survivin proteins in prostate cancer and to correlate the results with clinicopathologic variables.
Formalin-fixed, paraffin-embedded tissue sections from 138 cases of prostatic adenocarcinomas (PACs) were immunostained by an automated method using specific antibodies against survivin and Bcl-2. Staining was semiquantitatively scored based on both intensity and distribution, and results were correlated with morphologic and prognostic variables.
Of the 138 PACs tested, 113 (82%) expressed survivin. We found no correlation between survivin expression and prognostic variables, including grade, stage, DNA content (ploidy), and recurrence. Bcl-2 expression was positive in 95 (69%) of these 138 cases and correlated with nondiploid DNA content. Fourteen (50%) of 28 nondiploid PACs expressed Bcl-2, compared to 17 (25%) of 68 diploid tumors (P =.02). A trend for association of Bcl-2 expression with tumor stage was noted as follows: 21 (39%) of 54 advanced-stage PACs expressed Bcl-2, in comparison with 20 (24%) of 84 low-stage tumors (P =.07). On univariate analysis, 25 (48%) of the 52 PACs that recurred expressed Bcl-2, as compared with 16 (19%) of the 86 nonrecurrent PACs (P <.001). No correlation was noted between survivin and Bcl-2 expression.
Survivin is expressed in a majority of PACs and is not a prognosis-related marker, but may be a potential target for apoptosis-based therapy. Overexpression of Bcl-2 correlates with other prognostic variables and predicts disease recurrence of PACs. These data also suggest that survivin and Bcl-2 may regulate cell proliferation and cell death through different mechanisms.