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

Focal p53 protein expression and lymphovascular invasion in primary prostate tumors predict metastatic progression

TP53 is one of the most frequently altered genes in prostate cancer. The precise assessment of its focal alterations in primary tumors by immunohistochemistry (IHC) has significantly enhanced its prognosis. p53 protein expression and lymphovascular invasion (LVI) were evaluated for predicting metastatic progression by IHC staining of representative whole-mounted prostate sections from a cohort of 189 radical prostatectomy patients with up to 20 years of clinical follow-up. Kaplan–Meier survival curves were used to examine time to distant metastasis (DM) as a function of p53 expression and LVI status. TP53 targeted sequencing was performed in ten tumors with the highest expression of p53 staining. Nearly half (49.8%) of prostate tumors examined showed focal p53 expression while 26.6% showed evidence of LVI. p53(+) tumors had higher pathologic T stage, Grade Group, Nuclear Grade, and more frequent LVI. p53 expression of > 5% and LVI, individually and jointly, are associated with poorer DM-free survival. TP53 mutations were detected in seven of ten tumors sequenced. Four tumors with the highest p53 expression harbored likely pathogenic or pathogenic mutations. High levels of p53 expression suggest the likelihood of pathogenic TP53 alterations and, together with LVI status, could enhance early prognostication of prostate cancer progression.

Immunohistochemical correlates of TP53 somatic mutations in cancer

Despite controversy on the correlation between p53 accumulation and TP53 mutational status, immunohistochemical (IHC) detection of overexpressed protein has long been used as a surrogate method for mutation analysis. The aim of our study was to characterise the IHC expression features of TP53 somatic mutations and define their occurrence in human cancers. A large-scale database analysis was conducted in the IARC TP53 Database (R17); 7878 mutations with IHC features were retrieved representing 60 distinct tumour sites. The majority of the alterations were immunopositive (p <0.001). Sex was known for 4897 mutations showing a female dominance (57.2%) and females carrying negative mutations were significantly younger. TP53 mutations were divided into three IHC groups according to mutation frequency and IHC positivity. Each group had female dominance. Among the IHC groups, significant correlations were observed with age at diagnosis in breast, bladder, liver, haematopoietic system and head & neck cancers. An increased likelihood of false negative IHC associated with rare nonsense mutations was observed in certain tumour sites. Our study demonstrates that p53 immunopositivity largely correlates with TP53 mutational status but expression is absent in certain mutation types.Besides, describing the complex IHC expression of TP53 somatic mutations, our results reveal some caveats for the diagnostic practice.

Cancer biomarker discovery: the entropic hallmark

Background

It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods.

Methodology/Principal Findings

Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer.

Conclusions/Significance

We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-througput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases.

Gemcitabine in patients with non-small-cell lung cancer previously treated with platinum-based chemotherapy: a phase II California cancer consortium trial

A phase II trial was designed to evaluate the efficacy and toxicity of gemcitabine in patients with non-small-cell lung cancer (NSCLC) previously treated with platinum-containing regimens and prospectively categorized for platinum response status. Treatment consisted of gemcitabine 1000 mg/m2 given intravenously on days 1 and 8 of a 21-day cycle. The status of p53 in pretreatment tumor tissue was assessed by immunohistochemistry (IHC). Sixty-one patients who progressed or recurred following platinum-based therapy were enrolled, 26 platinum-sensitive and 35 platinum-refractory. A median of 4 treatment courses (range, 2-7 courses) was delivered. Of the 55 patients assessable for response, there was 1 confirmed complete response and 3 with a confirmed partial response for an overall response proportion of 7%. Twenty-one patients had stable disease while 28 progressed and 2 patients had an unconfirmed partial response. Three of the responders (2 confirmed, 1 unconfirmed) were platinum-refractory. Median progression-free survival (PFS) and overall survival for all patients were 4.1 months and 8.6 months, respectively. Median PFS and overall survival for the platinum-sensitive and platinum-refractory cohorts were 5.4 months versus 3.1 months, and 11.9 months versus 7.1 months, respectively. Toxicity was principally hematologic with grade 3/4 neutropenia in 21% and grade 4 platelets in 8%. There were no treatment-related deaths. Twenty-four of 33 patients (73%) had p53-positive tumors. Although no significant association between platinum sensitivity and p53 status was seen, patients with platinum-sensitive disease and negative p53 by IHC had a trend toward longer survival compared to those with platinum-refractory disease and/or p53 positivity (P = 0.06). We concluded that salvage gemcitabine in this dose and schedule is safe and tolerable in previously platinum-treated patients with NSCLC.

Blastic mantle cell lymphoma developing concurrently in a patient with chronic myelogenous leukemia and a review of the literature

Non-Hodgkin's lymphoma (NHL) occurring as a synchronous malignancy with chronic myelogenous leukemia (CML) is rare. To our knowledge, this is the first case reported of a patient who developed mantle cell lymphoma (MCL) after therapy with imatinib mesylate for CML. After a 3-year history of CML, the patient developed a lymphocytosis associated with diarrhea, anorexia, and weight loss. Imaging studies revealed abdominal adenopathy and extensive lymphomatous infiltration of the liver, stomach, pancreas, and kidneys. Flow cytometric and cytogenetic studies were consistent with MCL. Fluorescence in situ hybridization (FISH) of the bone marrow revealed a genetically distinct lymphoid neoplasm rather than an extramedullary blast crisis of CML. The development of lung cancer, prostate cancer, CML and MCL in this patient suggests a genetic predisposition, although other factors, including environmental exposures and therapy with imatinib mesylate could have had a contributory or synergistic role in the development of MCL.

The role of p53 in radiation therapy outcomes for favorable-to-intermediate-risk prostate cancer

PURPOSE

Some prostate cancers may have molecular alterations that render them less responsive to radiation therapy; identification of these alterations before treatment might allow improved treatment optimization. This study investigated whether p53, a potential molecular determinant, could predict long-term radiation therapy outcome in a restricted group of relatively favorable-risk prostate cancer patients treated uniformly with irradiation alone.

METHODS AND MATERIALS

This study included 53 patients previously treated with radiotherapy for favorable-to-intermediate-risk prostate cancer. These patients were selected for relatively low pretreatment PSAs (< or =21 ng/mL) and Gleason scores (< or =7) to decrease the likelihood of nonlocalized disease, because disease localization was necessary to examine the efficacy of localized radiation therapy. The status of p53 was immunohistochemically assessed in paraffin-embedded pretreatment biopsy specimens, along with appropriate controls. This marker was selected based upon a usable mutation prevalence in early-stage prostate cancer and its potential linkage with radiation response via cell cycle, DNA repair, and cell death pathways. Correlation between p53 mutation and clinical outcome was analyzed in univariate and multivariate fashion and included conventional prognosticators, such as stage, grade, and PSA. Freedom from biochemical failure was determined using American Society for Therapeutic Radiology and Oncology criteria. Limitations of prior studies were potentially avoided by requiring adequate posttreatment follow-up (median follow-up in nonfailing patients of 5.1 years), as well as pretreatment PSA and Gleason scores that suggested localized disease, and uniformity of treatment.

RESULTS

The total group of 53 favorable-to-intermediate-risk patients demonstrated an actuarial biochemical failure rate of 35% at 5 years. Forty percent of all specimens had a greater than 10% labeling index for p53 mutation, and actuarial biochemical control was found to strongly and independently correlate with p53 status. Patients with higher p53 labeling indices demonstrated significantly higher PSA failure rates (p < 0.001). In contrast, p53 status did not correlate with pretreatment PSA, grade, or tumor stage. Similarly, pretreatment PSA (log-rank 0.22), Gleason score (log-rank 0.93), and T stage (log-rank 0.15) were not prognostic for outcome in this group of patients selected for their relatively favorable clinical characteristics.

CONCLUSIONS

(1) p53 status in pretreatment biopsies strongly predicted for long-term biochemical control after radiation therapy in favorable-to-intermediate-risk prostate cancer patients. (2) If validated in other independent clinical data sets, p53 status should be considered as a stratification factor in future clinical trials and could be useful in guiding treatment. Abnormal p53 status might favor surgical management, aggressive dose escalation, or p53-targeted therapy.

P53 gene mutations: case study of a clinical marker for solid tumors

P53 is a tumor-suppressor gene that codes for a multifunctional DNA-binding protein involved in cell cycle arrest, DNA repair, differentiation, and apoptosis. The P53 gene is mutated in approximately 50% of human cancers and in germline DNA of families with inherited cancer syndromes. The role of P53 mutations in the program of carcinogenic genetic alterations differs among tumor sites ranging from the earliest mutations that can be detected in premalignant cells to mutations that trigger malignant transformation of a benign neoplasm. P53 mutations can cause expression of abnormal proteins or result in complete absence of P53 expression. For these reasons the role of P53 genetic disruption has different implications in different tumor types and may vary depending on the effect of the mutation on P53 protein function. Immunohistochemical detection of P53, commonly used as a surrogate for identification of a mutant gene, has imperfect sensitivity and specificity, further complicating correlations between P53 gene status and clinical outcomes. The presence of P53 mutations has been shown to affect prognosis of some cancers. The identity of P53 mutations can be used to determine tumor clonality. The detection of P53 mutations suggests the severity of premalignant lesions. Evolving technology for more accurate identification of P53 mutations, better understanding of the function of mutant P53 protein, and more detailed analysis of individual tumor types may expand the relevance of P53 gene analysis for clinical outcomes and therapeutic response.

p53 Alteration and chromosomal instability in prostatic high-grade intraepithelial neoplasia and concurrent carcinoma: analysis by immunohistochemistry, interphase in situ hybridization, and sequencing of laser-captured microdissected specimens

p53 mutation has been shown to be associated with chromosomal instability (CI) in many human dysplastic and neoplastic lesions. However, the precise role of p53 in the pathogenesis of prostate carcinoma (Pca) is unknown. Topographic analysis of p53 alteration using immunohistochemistry (IHC) was performed on 35 archived prostatectomy specimens containing Pca foci; high-grade prostate intraepithelial neoplasia (HPIN) foci intermingled with cancer (HPINI) and situated away (HPINA). Specimens from 2 patients were topographically genotyped using laser capture microdissection, PCR amplification, and direct sequencing of p53 exons 5-9. CI was evaluated in the same tissue foci by interphase in situ hybridization (IFISH) using centromere probes for chromosomes 7, 8, and Y. p53 immunoreactivity was found in 20%, 17%, 0, and 0 in Pca, HPINI, HPINA, and benign epithelium, respectively. p53 molecular analysis in the specimens examined confirmed the IHC findings. IFISH revealed numerical chromosomal alterations in keeping with CI in 71% and 25% of p53+ and p53- Pca, respectively (P =.1), 67% and 0 of p53+ and p53- HPIN, respectively (P <.02), and in 27% and 0 of HPINI and HPINA, respectively. We concluded that p53 mutation is an early change in at least a subset of Pca. HPINI foci tend to have higher overall p53 immunoreactivity and CI than HPINA. The presence of p53 mutation in HPIN was associated with the presence of CI as determined by IFISH. Our study also provided additional evidence in support of the concept that HPIN might be the earliest precursor of cancer. Furthermore, our studies identify genomic similarities in HPINI and Pca, implying that carcinoma may arise from progression of certain HPIN foci that most likely harbor p53 mutation and/or more CI.

Mutations within the tumour suppressor gene p53 are not confined to a late event in prostate cancer progression. a review of the evidence

Mutations in the p53 tumour suppressor gene are generally believed to be a late event in the progression of prostate cancer, and are associated with androgen independence, metastasis, and a worse prognosis. In this review, we examine the current literature available on p53 mutations and focus on stages A (T1) and B (T2) of prostate cancer. We report here that p53 mutations can be found in approximately one third of prostate cancers that are clinically localized to the prostate. In addition, high levels of p53 mutation are found in normal prostate tissue of prostate cancer patients, prostatic intraepithelial neoplasia, and benign prostatic hyperplasia. The limitations of techniques used to determine p53 mutations are discussed, as well as other modes of p53 loss in early stage prostate cancer.

Phase I/II study of paclitaxel, carboplatin, and methotrexate in advanced transitional cell carcinoma: a well-tolerated regimen with activity independent of p53 mutation

OBJECTIVES

To evaluate the feasibility and activity of paclitaxel, carboplatin, and methotrexate in advanced transitional cell carcinoma (TCC) of the urothelium and to relate the activity of this combination to the mutational status of p53.

METHODS

In the Phase I portion, paclitaxel 200 mg/m(2) (3-hour infusion), carboplatin dosed to an area under the curve (AUC) of 6 mg/mL. min, and methotrexate 10 mg/m(2), increasing in 10-mg/m(2) increments, were administered on day 1 and every 21 days thereafter with granulocyte colony-stimulating factor (G-CSF) and leucovorin support. Subsequently, a Phase II study was initiated in which the carboplatin dose was lowered to an AUC of 5 to allow treatment without G-CSF. p53 expression was evaluated using immunohistochemistry.

RESULTS

Thirty-three patients were accrued. Median age was 66 years. No dose-limiting toxicities were seen in the Phase I portion despite escalation of the methotrexate to 60 mg/m(2). Principal toxicities were myelosuppression and neuropathy. The overall response rate (Phase I and II) was 56% (95% confidence interval 38% to 74%). Median survival was 15.5 months; 88% of patients overexpressed p53 at the primary site.

CONCLUSIONS

Paclitaxel, carboplatin, and methotrexate were well tolerated and active in advanced TCC. The high response rate to this regimen despite frequent p53 mutation is consistent with the p53-independent mechanism of paclitaxel. Whether this regimen is superior to methotrexate/vinblastine/doxorubicin/cisplatin, other paclitaxel-based regimens, or to paclitaxel alone will require comparative trials.

Proliferation- and apoptosis-associated factors in advanced prostatic carcinomas before and after androgen deprivation therapy: prognostic significance of p21/WAF1/CIP1 expression

The molecular mechanisms leading to androgen-independent growth in prostate cancer (PC) are poorly understood. Androgen deprivation therapy (ADT) results physiologically in a decrease in proliferation and an increase in programmed cell death (PCD)/apoptosis. The aim of our study was to get more insight into these processes in prostatic carcinomas before and after ADT. For this purpose, immunohistologic staining for the androgen receptor (AR) molecule, the Ki-67 antigen, the bcl-2 oncoprotein, the p53 protein and its physiologic effector, p21/WAF1, was performed on archival material. PCD was visualized by enzymatic detection of DNA fragmentation. Specimens from 69 PC patients after ADT were studied in correlation to histopathology and prognosis. In 42 cases, corresponding tumour tissue from the untreated primary tumours could be analysed comparatively. Before ADT, histologic grade was associated with Ki-67 index (P < 0.0001, Spearman correlation) and PCD rate (P < 0.05, Spearman correlation). Ki-67 index correlated with PCD rate (P < 0.05, Spearman correlation) and p21/WAF1 expression (P < 0.01, Fisher's exact test). p21/WAF1 expression was the only statistically significant prognostic factor for shorter survival (P < 0.002, log-rank test). All p21/WAF1-positive cases showed high Ki-67 index and high histologic grade. After ADT, loss of AR expression was associated with high Ki-67 index, whereas histologic signs of regression correlated negatively with Ki-67 index (P < 0.001, Pearson chi2 test). p21/WAF1 expression increased significantly (P < 0.02, McNemar test) and correlated with p53 accumulation (P < 0.0001, Pearson chi2 test). Most significant prognostic parameter after conventional ADT was high-rate p21/WAF1 expression (> 50% of tumour cells; P < 0.00001, log-rank test). This study demonstrates that p21/WAF1 overexpression before and after ADT characterizes a subgroup of advanced PC with paradoxically high proliferation rate and significantly worse clinical outcome. This finding might be clinically useful for planning therapy in these patients.

Mutation and expression analysis of the p73 gene in prostate cancer

BACKGROUND

p53 is the most highly mutated tumor suppressor gene in human cancers. Recently, p73, a first homologue of p53, was identified and considered to be an imprinted tumor suppressor gene. Thus, we analyzed the possible role of p73 in human prostate cancers.

METHODS

We investigated the expression levels and expressed allelotypes and searched for mutations in the p73 gene in 27 primary prostate cancers with matched normal tissues as well as in four prostate cell lines.

RESULTS

Allelic expression analysis using polymorphisms in exons 2 and 5 revealed that p73 is biallelically expressed in both normal and tumor tissues, suggesting that p73 is not imprinted in prostate tissues. Quantitative PCR demonstrated that p73 expression is the same in both normal and tumor prostate tissues. Denaturing high-performance liquid chromatography and DNA sequencing revealed that there were no tumor-specific mutations in the p73 gene at the genomic level.

CONCLUSIONS

These data indicate that alterations of p73, including mutations, changes in message abundance, and changes in allelic expression, are likely to be rare in early-stage prostate cancer, and that p73 could be a tissue-specific imprinting gene.

Expression of Bcl-2, Bax, and p53 in high-grade prostatic intraepithelial neoplasia and localized prostate cancer: relationship with apoptosis and proliferation

BACKGROUND

Apoptosis-regulating genes have been shown to be important in the biology of prostate cancer. The aim of this study was to examine and correlate the expression of the apoptosis-regulating genes bcl-2, bax, and p53 with the frequency of apoptosis and rate of proliferation in benign prostatic epithelium (BP), prostate cancer, and high-grade prostatic intraepithelial neoplasia (HGPIN), which is currently considered the most likely precursor of prostate cancer.

METHODS

Forty-four patients with histologically proven prostate cancer were investigated. All the men underwent radical prostatectomy. Immunohistochemistry was performed to assess expression of bcl-2, bax, and p53, and proliferation rate, as measured by the Ki-67 index. The frequency of apoptotic bodies was assessed by morphological criteria.

RESULTS

The apoptotic index (AI) was highest in prostate cancer, and was significantly greater in HGPIN compared to benign prostate. The Ki-67 index was greatest in cancer, intermediate in HGPIN, and lowest in BP. The AI was increased in areas of BP in patients treated with neoadjuvant androgen ablation. No change in AI was seen in treated cases of HGPIN or cancer. Accumulation of p53 protein was infrequent in prostate cancer (2/43: 4.6%), and was absent in HGPIN. Bcl-2 overexpression was present in 2.3% of cancers (1/43) and in 34.9% of cases of HGPIN (15/43). Bax expression was seen in all cases of cancer and HGPIN. There was no correlation between bcl-2 expression and the apoptotic and Ki-67 indices in HGPIN.

CONCLUSIONS

p53 and bcl-2 expression is infrequent in clinically organ confined prostate cancer. Bcl-2 expression is significantly higher in HGPIN than in both the associated prostate cancer and BP. The AI and Ki-67 index appeared intermediate in the putative precursor lesion HGPIN compared to prostate cancer and BP.

Racial differences in clinically localized prostate cancers of black and white men

PURPOSE

Tumor grade, deoxyribonucleic acid (DNA) ploidy, proliferation, p53 and bcl-2 expression were examined in clinically localized prostate cancers of black and white American men to learn whether these features showed racial differences.

MATERIALS AND METHODS

A total of 117 prostate cancers (43 black and 74 white patients) obtained at radical prostatectomy for clinically localized disease were assigned Gleason scores by a single pathologist. Enzymatically dissociated nuclei from archival prostate cancers were examined by DNA flow cytometry using propidium iodide staining and the multicycle program to remove debris and sliced nuclei and to perform cell cycle analysis. For immunostaining after microwave antigen retrieval we used a DO-1/DO-7 monoclonal antibody cocktail for p53 and the clone 124 antibody for bcl-2.

RESULTS

Significantly more black than white men had Gleason score 7 tumors. The DNA ploidy distribution of Gleason 6 or less tumors was similar for both races. As anticipated, the ploidy distribution of higher grade prostate cancer in white men was more abnormal but, unexpectedly, this was not found for higher grade prostate cancer in black men. No significant racial differences were found in S phase fractions, p53 or bcl-2 immunopositivity. However, for prostate cancer in black men there was a significant association between bcl-2 immunopositivity and higher S-phase fractions.

CONCLUSIONS

The aggressive prostate cancers of black men may be characterized by the 2 features of high proliferation and a block to programmed cell death.

Hippocampal Myc and p53 expression following transient global ischemia

The proto-oncogene c-myc, and the tumor suppressor gene p53, encode proteins which function as transcriptional regulating factors governing cell proliferation, differentiation, and apoptosis. Recent evidence suggests that the delayed neuronal death which follows an episode of transient forebrain ischemia may involve apoptotic processes. We have therefore utilized immunohistochemistry to investigate the effects of transient global ischemia on neuronal expression of p53- and Myc-like immunoreactivities in the rodent forebrain 2, 12, 24, 48, and 72 h following reperfusion. Transient global ischemia (20 min), produced by four vessel occlusion (4-VO), initially elevated p53-like immunoreactivity in both CA1 and CA3 hippocampal subfields at 24 h of recirculation. However, distinct patterns of gene expression became evident in these regions at later time points. A pivotal difference was the persistence of ischemia-induced increases of p53- and Myc-like immunoreactivity in the CA1 region of the hippocampus. Unlike CA3 neurons where p53-like immunoreactivity subsided to basal levels by 48 h of survival, CA1 neurons continued to display increased p53-immunoreactivity 48 h post-ischemia, while Myc-like immunoreactivity was selectively elevated in CA1 neurons at this time point. Ischemia-induced increases in p53-like immunoreactivity were also detected in vulnerable regions of the amygdala, thalamus, and cortex 12 to 48 h after recirculation. Given that both p53 and Myc have been implicated in gene signalling pathways which mediate programmed cell death, our findings which demonstrate that 4-VO produces persistent elevations of p53- and Myc-like immunoreactivities in vulnerable neurons suggest that these proteins may also contribute to delayed neuronal death following an episode of transient forebrain ischemia.

p53 and bcl-2 immunohistochemical alterations in prostate cancer treated with radiation therapy

OBJECTIVES

Radiation therapy is definitive treatment for localized prostate cancer. It causes cellular deoxyribonucleic acid (DNA) damage, which, if irreparable, results in apoptosis or programmed cell death. Overexpression of mutant p53 and/or bcl-2 proteins prolongs cell survival despite exposure to damaging agents. We examined whether abnormal expression of either gene could help to explain radiation therapy failures in prostate cancer.

METHODS

Archival tissue from patients who had failed radiation therapy as treatment for prostate cancer was obtained before and after treatment. These cancer samples were examined immunohistochemically for accumulation of p53 and bcl-2 proteins. Comparison was made with specimens from patients who had no evidence of recurrent or persistent disease at least 3 years following radiation therapy.

RESULTS

High rates of p53 immunopositivity were found in the prostate tissue from all groups studied. More patients who had failed radiation therapy were found to have bcl-2 immunopositive specimens than were those without evidence for recurrent disease (41% preradiation and 61% postradiation versus 8%, P <0.05). More patients who failed radiation therapy had both p53 and bcl-2 immunopositive prostate tissue than did those who were treated successfully (32% preradiation and 48% postradiation versus 8%).

CONCLUSIONS

bcl-2 immunopositivity, with or without concomitant detection of p53, was found in significantly more cancers of patients who failed radiation therapy. Positive staining for bcl-2 may serve as a marker for determining the radiation sensitivity of a tumor and thus may help to guide treatment options. It is also notable that a high proportion of the prostate cancers examined were immunopositive for p53.