Prognostic Significance of p 53 Nuclear Accumulation in Localized Prostate Cancer Treated with Radical Prostatectomy 1

The role of p53 in the pathogenesis of, and as a predictive biomarker for, localized prostate cancer (PCa) is contested. Recent work has suggested that patterns of p53 nuclear accumulation determined by immunohistochemistry are prognostic, whereas studies using other methods question the role ofp53 mutations in predicting outcome. We studied 263 men with localized PCa treated with radical prostatectomy to determine whether p53 nuclear accumulation predicts relapse and disease-specific mortality. We combined two p53 immunohistochemistry scoring systems: (a) percentage of p53-positive tumor nuclei in all major foci of cancer within the prostate; and (b) clustering, where the presence of 12 or more p53-positive cells within a3200 power field was deemed “cluster positive. ” Analysis was undertaken usingx, KruskalWallis, and Mann-Whitney tests for clinicopathological variables and the Kaplan-Meier method, log-rank test, and univariate and multivariate Cox regression modeling for evaluation of contribution to relapse and disease-specific survival. At mean follow-up of 55.1 months (range, 4.9 –123.0 months), 39% (102 of 263) of patients had relapsed and 2.3% (6 of 253) had died of PCa. Pretreatment serum prostate-specific antigen concentration, pathological tumor stage, lymph node involvement, Gleason score, and p53 nuclear accumulation, as determined by either percentage score or cluster status, were independent predictors of relapse in multivariate analysis. Clustering of p53-positive cells distinguished between favorable and poor prognosis patients within the lowest p53-positive stratum (>0 to <2%) and was the most discriminatory threshold for predicting relapse in the entire cohort. p53 status predicted outcome in patients with a Gleason score of 5 and above but not those with a score of 4 and below. In patients treated with neoadjuvant hormonal therapy, p53 cluster positivity carried a 90% (19 of 21) risk of relapse by 36 months. All six patients who died from PCa in the period of the study exhibited p53 nuclear accumulation in 20% or more tumor nuclei. This study demonstrates strong relationships between p53 nuclear accumulation and relapse and disease-specific mortality in a large series of localized PCas. Furthermore, the presence of clusters of p53-positive nuclei delineates a group of patients with poor prognosis not identified by traditional scoring methods and supports the hypothesis that p53 dysfunction within PCa may exist in foci of tumor cells that are clonally expanded in metastases. INTRODUCTION PCa is the most common male cancer in industrialized societies and represents a serious public health problem. Identification of patients with aggressive rather than indolent PCa is a major challenge for optimal management and is only partially met by current prognostic parameters. Delineation of patterns of gene expression in early PCa that correlate with an aggressive phenotype is a priority and may allow radical treatment to be offered on a more selective basis to those patients with clinically localized yet aggressive disease. Inactivation of the tumor suppressor gene p53 is implicated in tumorigenesis for . 50% of all human cancers (1). p53 functions as a transcriptional regulator involved in G 1 phase growth arrest of cells in response to DNA damage as well as having roles in the regulation of the spindle checkpoint, centrosome homeostasis, and G 2-M phase transition (2). p53 also induces apoptosis by transcription-dependent and -independent mechanisms in many cell types (1–3) and regulates tumor angiogenesis and expression of the Kai1 metastasis suppressor gene (1, 4–6). Nuclear accumulation of p53 detected by IHC typically indicates the presence of p53 gene mutations (7, 8), although the correlation between nuclear accumulation of p53 and the presence of p53 gene mutations can vary (9). Nuclear accumulation of p53 is a prognostic indicator in several human cancers, including breast (4, 10, 11), lung (12), and colorectal carcinoma (13). The value of p53 nuclear accumulation as a prognostic factor in localized PCa is controversial. A number of studies have shown that p53 nuclear accumulation detected by IHC is prognostic at a variety of dichotomizing cutoff points based on the number of p53-positive nuclei. These studies describe either a group of poor prognosis patients with 20% p53-positive nuclei (14, 15) or a group of patients with lower percentages of positive cells in a heterogeneous, focal staining pattern where either the presence of any nuclear accumulation or the presence of clusters of cells showing nuclear accumulation is adversely prognostic (16–18). However, other studies comparing p53 nuclear accumulation with assessment of p53 gene mutations have failed to provide conclusive evidence for the importance of p53 in localized PCa or a strong correlation between nuclear accumulation andp53gene mutation (19–22). One study suggested that a chromosome 17p locus close to the p53 gene was an important prognostic feature when both alleles at the site were lost but found that p53 IHC is noncontributory in predicting prognosis and concluded that another gene or genes on chromosome 17p may be involved in PCa progression (19). In studying other cancers, several authors have suggested that assessment of p53gene mutations and p53 expression in combination may more accurately define prognostically important p53 dysfunction (9, 23, 24). Comparison of PCa metastases with primary PCas in the same Received 9/27/99; accepted 1/19/00. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 This research was supported by grants from the National Health and Medical Research Council of Australia, RT Hall Trust, Laurence Freedman Trust, New South Wales Cancer Council, Leo and Jenny Leukemia, and Cancer Foundation of Australia, St. Vincent’s Clinic Foundation, and Merck Sharp and Dohme Research Foundation. D. Q. is a National Health and Medical Research Council of Australia Medical Postgraduate Research Scholar and recipient of the Vincent Fairfax Family Foundation Fellowship from the Royal Australasian College of Physicians. 2 Deceased. 3 To whom requests for reprints should be addressed, at Cancer Research Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW 2010, Australia. Phone: 612-9295-8322; Fax: 612-9295-8321; E-mail: r.sutherland@garvan. unsw.edu. au. 4 The abbreviations used are: PCa, prostate cancer; IHC, immunohistochemistry; PSA, prostate-specific antigen; RP, radical prostatectomy; NHT, neoadjuvant hormonal therpy; DRE, digital rectal examination; TNM, Tumor-Node-Metastasis; SVI, seminal vesicle involvement.