p53 Protein and Gene Alterations in Pathological Stage C Prostate Carcinoma

Clinical significance of p53 alterations in surgically treated prostate cancers

Despite the high number of previous studies, the role of p53 alterations in prostate cancer is not clearly defined. To address the role of p53 alterations in prostate cancer biology, a total of 2514 cancers treated by radical prostatectomy were successfully analyzed by immunohistochemistry in a tissue microarray format. Overall a low rate of p53-positive tumors was found (2.5%). A significant underestimation of p53-positive cases was excluded by subsequent large section analyses and direct sequencing of the p53 gene in subsets of our patients. Large section analysis of 23 cases considered negative on the tissue microarray yielded only one weakly p53-positive tumor. Only 4 out of 64 (6.4%) high-grade tumors, that were considered negative for p53 by immunohistochemistry, presented exon 5-8 mutations. These data suggest a high sensitivity of our immunohistochemistry approach and confirm the overall low frequency of p53 alterations in clinically localized prostate cancer. A positive p53 immunostaining was strongly associated with presence of exon 5-8 mutations (P<0.0001), advanced pT-stage (P<0.0001), high Gleason grade (P<0.0001), positive surgical margins (P=0.03) and early biochemical tumor recurrence (P<0.0001). A higher rate of positive p53 immunostaining was detected in late-stage diseases including metastatic prostate cancer (P=0.0152) and hormone-refractory tumors (P=0.0003). Moreover, p53 expression was identified as an independent predictor of biochemical tumor recurrence in the subgroup of low- and intermediate-grade cancers. In summary, the results of this study show that p53 mutations characterize a small biologically aggressive subgroup of prostate cancers with a high risk of progression after prostatectomy. The rate of p53 alterations increases with prostate cancer progression.

Thrombospondin-1 expression in patients with pathologic stage T3 prostate cancer undergoing radical prostatectomy: association with p53 alterations, tumor angiogenesis, and tumor progression

OBJECTIVES

To investigate thrombospondin-1 (TSP) expression in patients with prostate cancer undergoing radical prostatectomy. TSP is a p53-dependent inhibitor of tumor angiogenesis. Previous studies have demonstrated that TSP expression is significantly associated with the microvessel density (MVD) count, p53 expression, and disease-specific and overall survival in patients with invasive bladder cancer undergoing radical cystectomy.

METHODS

Radical prostatectomy specimens from 85 patients with pathologic Stage T3 disease were analyzed for TSP expression, p53 nuclear reactivity, and MVD using antigen-retrieval immunohistochemistry. The median follow-up after surgery was 10.6 years (range 1.8 to 15.4). Disease recurrence was defined as a prostate-specific antigen level of 0.2 ng/mL or greater on two consecutive occasions after surgery. TSP expression was graded as present or absent on the basis of the immunoreactivity in the extracellular matrix by persons unaware of the clinical outcome. Specimens were considered p53 positive (altered) if more than 10% of the tumor cells demonstrated nuclear reactivity. The chi-square test was used to determine whether the associations were significant between the pathologic tumor characteristics and the immunohistochemical findings. The log-rank test was used to determine the associations between the immunohistochemical findings and disease recurrence.

RESULTS

TSP and p53 were graded as positive in 21 (26%) and 16 (19%) tumors, respectively. The median MVD count was 111.5. No significant associations were found among p53 status, TSP expression, and MVD. Seminal vesicle invasion and Gleason pattern 4 or 5 disease were significant predictors of disease recurrence. A trend was noted toward a higher rate of disease recurrence for patients with altered p53 expression (p53 positive) or increased MVD. TSP expression was not associated with disease recurrence.

CONCLUSIONS

We found no significant association between TSP expression and p53 status, MVD count, or outcome after radical prostatectomy for patients with pathologic Stage T3 prostate cancer. Our data suggest that p53 and MVD may be associated with outcome in these patients. Additional studies are needed to identify reliable molecular markers of outcome for patients with this disease.

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.

Limiting the location of putative human prostate cancer tumor suppressor genes on chromosome 18q

We studied loss of heterozygosity (LOH) on the long arm of human chromosome 18 in prostate cancer to determine the location of a putative tumor suppressor gene (TSG) and to correlate these losses with the pathological grade and stage of the cancer. Of 48 specimens analysed 17 (35.4%) lost at least one allele on chromosome 18q. All the specimens with allelic losses lost at least one allele within chromosomal region 18q21. Allelic losses picked at D18S51 (19%) and D18S858 (17%). A 0.58 cM DNA segment that includes the D18S858 locus and is flanked by the microsatellite loci D18S41 and D18S381, was lost in eight (47%) of 17 specimens with allelic losses. This segment was designated as a LOH cluster region 1 (LCR 1). Although Smad2 resides within LCR 1, it was not mutated in any of the six prostate cell lines (five prostate cancer cell lines and one immortalized prostate epithelial cell line) analysed, suggesting that it is not a candidate TSG in prostate cancer. A second LCR at 18q21, LCR 2, includes the D18S51 locus and is flanked by the D18S1109 and D18S68 loci, which are separated by 7.64 cM. LCR 2 was lost in six (35%) of the 17 specimens with chromosome 18q losses. These results suggest that chromosome 18q21 may harbor two candidate prostate cancer TSGs. The candidate TSGs DCC and Smad4 are located centromeric to the LCRs. No alleles were lost within or in close proximity to these genes, suggesting that they are not targets for inactivation by allelic losses in prostate cancer. Although there was no obvious correlation between chromosome 18q LOH and the pathological grade or stage, three (37.5%) of eight low-grade cancers and nine (32.1%) of 28 organ-confined cancers lost alleles at 18q21, suggesting that allelic losses are relatively early events in the development of invasive prostate cancer.

Vascular endothelial growth factor and its correlation with angiogenesis and p53 expression in prostate cancer

BACKGROUND

Previously it was demonstrated that in prostate tumors, angiogenesis measured as microvessel density (MVD) is associated with tumor stage as well as WHO grade and is an independent predictor of clinical outcome. Vascular endothelial growth factor (VEGF) is a major inducer of angiogenesis. There is some evidence that P53 mutations cause overexpression of VEGF. We studied VEGF expression, p53 overexpression, and P53 mutations in prostate cancer (PCA) to investigate the role of VEGF as an angiogenic marker and the possible deregulation of VEGF as a result of P53 mutations in PCA.

METHODS

Immunohistochemical staining with a polyclonal VEGF antibody was performed in 55 paraffin-embedded PCA, in which MVD had previously been determined, as well as in 5 prostatic adenomas (PA) and 20 adjacent normal prostate tissues. In addition, 37 PCA and 5 PAs were examined for p53 expression by immunohistochemistry. Temperature gradient gel electrophoresis (TGGE) was performed in 13 of these PCA to screen for P53 mutations. VEGF expression, p53 expression, and mutations were then correlated with tumor stage, grade, MVD, and clinical outcome.

RESULTS

While PA and normal prostate tissue generally showed no or only low VEGF expression, there was a significant increase in VEGF expression with tumor stage, grade, and MVD in PCA. During clinical follow-up (mean, 31.9 months), 9 of 55 patients had tumor progression. Significant differences in VEGF expression were found between patients with tumor progression and those without (P = 0.0004). Of the 37 PCA evaluated for p53 expression, 12 exhibited p53 overexpression. TGGE revealed P53 mutations in 3 of 13 PCA. However, there was no correlation between VEGF expression, p53 overexpression, and P53 mutation, respectively.

CONCLUSIONS

VEGF seems to be an important, clinically relevant inducer of angiogenesis in PCA. VEGF expression was shown to correlate positively with tumor stage, grade, MVD, and clinical outcome. However, regulation of VEGF in PCA appears to be independent of p53 expression.

Outcome prediction with p53 immunostaining after radical prostatectomy in patients with locally advanced prostate cancer

PURPOSE

Conventional pathological variables in prostate cancer may not provide optimal prediction of patient outcome. Pathological findings and p53 immunostaining were measured prospectively in radical prostatectomy specimens to determine the incremental improvement in prediction of patient outcome over clinical findings.

MATERIALS AND METHODS

From a previous prospective study of 392 consecutive patients with prostate cancer who did not receive preoperative therapy and were treated with radical prostatectomy 25 had pathological stage pT3aN0M0, 24 had pT3bN0M0, 2 had pT2bN1M0, 7 had pT3aN1M0 and 14 had pT3bN1 prostate cancer. These locally advanced stage cases comprise the current study population and further analysis was done with p53 immunostaining. All prostate specimens were totally embedded, serially sectioned and whole mounted. We examined pathological, clinical and laboratory findings as well as p53 immunostaining.

RESULTS

Median followup was 5.4 years (range 0.5 to 6.4). Univariate analysis revealed that pathological stage, 10% or greater immunostaining for p53, area and length of extraprostatic cancer extension, and cancer volume (all p </=0.03) were associated with biochemical (prostate specific antigen) or clinical failure. When all variables were considered in stepwise multivariate analysis none attained statistical significance after p53 status entered the model (p <0.01, risk ratio 2.9 for 10% or greater versus less than 10%, 95% confidence interval 1.4-6.2). The concordance index analysis for the predictive ability of prostate specific antigen, stage, grade and ploidy (c = 0.66) was inferior to the predictive ability of a statistical model also including p53 status (c = 0.71).

CONCLUSIONS

In cases of locally advanced stage cancer p53 immunoreactivity after radical prostatectomy improves outcome prediction. Addition of this variable to those routinely determined may identify a subset of patients who would benefit from more intensive postoperative surveillance and adjuvant therapy.

A novel association between the human heat shock transcription factor 1 (HSF1) and prostate adenocarcinoma

A search for differentially expressed genes in a pair of nonmetastatic (PC-3) versus metastatic variant (PC-3M) human prostate carcinoma cell lines led to identification of the human heat shock factor (HSF1) as an overexpressed gene product in PC-3M cells. Analysis of primary prostate cancer specimens indicated that HSF1 is generally up-regulated in most of the malignant prostate epithelial cells relative to the normal prostate cells. Among the known effectors of HSF1 action, constitutive levels of HSP70 and HSP90 are not significantly altered by the naturally elevated expression of HSF1 as in PC-3M cells or by transduced overexpression of HSF1 in PC-3 cells. The basal levels of HSP27 in both cases are, however, consistently increased by two- to threefold. With respect to response to heat shock, high basal concentration of HSP90 is not further enhanced in these cells, and HSP70 is up-regulated irrespective of HSF1 level. Heat shock, however, causes an increase in HSP27 when HSF1 is up-regulated, except when the expression of HSF1 is already too high. These results document for the first time that HSF1 is overexpressed in human prostate cancer cells, at least one consequence of which in the prostate cancer cell lines tested is stimulation of both basal and stress-induced expression of HSP27, an important factor in cell growth, differentiation, or apoptosis.

Limiting the location of a putative human prostate cancer tumor suppressor gene at chromosome 13q14.3

We studied loss of heterozygosity (LOH) on human chromosome 13q in prostate cancer specimens to determine the location of a putative tumor suppressor gene (TSG) and to correlate these losses with the clinicopathological stage of the disease. Overall 13 (21%) of 61 specimens analysed had an allele loss on the long arm of chromosome 13. The most frequent (37%) LOH among the informative cases with allele losses was detected at the D13S284 locus on chromosome 13q14. 3. A portion of the DNA segment that spans this locus and is flanked by the microsatellite loci D13S153 and D13S163 was lost in 85% of the specimens with allele losses and was designated as a LOH cluster region (LCR). The LCR spans more than 6 Mbp of DNA. The results suggest that a TSG relevant for the development of prostate cancer is located telomeric to the RB locus. There was a significant correlation (P=0.0024) between chromosome 13q LOH and advanced metastatic disease, suggesting that loss of 13q14.3 region is associated with prostate cancer progression. However, further research must be conducted to establish the identity and function of this putative TSG.

Loss of cell cycle regulators p27(Kip1) and cyclin E in transitional cell carcinoma of the bladder correlates with tumor grade and patient survival

The cyclin-dependent kinase inhibitor p27(Kip1) is a powerful molecular determinant of cell cycle progression. Loss of expression of p27(Kip1) has been shown to be predictive of disease progression in several human malignancies. In this study we investigated the expression of two key cell cycle regulators, p27(Kip1) and cyclin E, in the progression of transitional cell carcinoma of the bladder. An immunohistochemical analysis was conducted in a series of 50 bladder tumor specimens, including 3 metastatic lymph nodes, and 7 normal bladder specimens, using specific antibodies against the two regulators of the cell cycle, p27(Kip1) and cyclin E. The degree of immunoreactivity was correlated with the pathological tumor grade, stage, and patient survival. A uniformly intense immunoreactivity for p27(Kip1) and cyclin E was observed in epithelial cells of normal bladder tissue. Malignant bladder tissue demonstrated a heterogeneous pattern of significantly reduced p27(Kip1) and cyclin E immunoreactivity, compared with normal urothelium (P < 0.01). In addition, there was progressive loss of expression of both cell cycle proteins with increasing tumor grade and pathological stage. Expression of p27(Kip1) was significantly lower in the poorly differentiated tumors (grades III) compared to well and moderately differentiated (grades I and II) tumors (P = 0.004). Moreover, the expression of cyclin E was lower in grade III tumors compared to grade I and II lesions, although this difference failed to reach statistical significance. Most significantly, Kaplan-Meier plots of patient survival show increased mortality risk associated with low levels of p27(Kip1) (P = 0.001) and cyclin E (P = 0.002) expression. This is the first evidence that loss of expression of p27(Kip1) and cyclin E in human bladder transitional cell carcinoma cells correlates with advancing histological aggressiveness and poor patient survival. These results have clinical importance, because they support a role for p27(Kip1) and cyclin E as novel predictive markers of the biological potential of bladder tumors that will enable identification of those tumors most likely to progress to muscle invasive disease and of patient survival.

Distinct altered patterns of p27KIP1 gene expression in benign prostatic hyperplasia and prostatic carcinoma

BACKGROUND

The p27KIP1 gene, whose protein product is a negative regulator of the cell cycle, is a potential tumor suppressor gene; however, no tumor-specific mutations of this gene have been found in humans. This study was undertaken to identify and to assess potential alterations of p27KIP1 gene expression in patients with benign prostatic hyperplasia (BPH) and patients with prostate cancer.

METHODS

We analyzed 130 prostate carcinomas from primary and metastatic sites, as well as prostate samples from normal subjects and from patients with BPH. Immunohistochemistry and in situ hybridization were used to determine the levels of expression and the microanatomical localization of p27 protein and messenger RNA (mRNA), respectively. Immunoblotting and immunodepletion assays were performed on a subset of the prostate tumors. Associations between alterations in p27KIP1 expression and clinicopathologic variables were evaluated with a nonparametric test. The Kaplan-Meier method and the logrank test were used to compare disease-relapse-free survival. Prostate tissues of p27Kip1 null (i.e., knock-out) and wild-type mice were also evaluated.

RESULTS

Normal human prostate tissue exhibited abundant amounts of p27 protein and high levels of p27KIP1 mRNA in both epithelial cells and stromal cells. However, p27 protein and p27KIP1 mRNA were almost undetectable in epithelial cells and stromal cells of BPH lesions. Furthermore, p27Kip1 null mice developed enlarged (hyperplastic) prostate glands. In contrast to BPH, prostate carcinomas were found to contain abundant p27KIP1 mRNA but either high or low to undetectable levels of p27 protein. Primary prostate carcinomas expressing lower levels of p27 protein appeared to be biologically more aggressive (two-sided P = .019 [Cox regression analysis]).

CONCLUSIONS/IMPLICATIONS

On the basis of these results, we infer that loss of p27Kip1 expression in the human prostate may be causally linked to BPH and that BPH is not a precursor to prostate cancer.

Association of p27Kip1 levels with recurrence and survival in patients with stage C prostate carcinoma

BACKGROUND

There are few biologic determinants that are prognostic for patients with localized prostate cancer. We examined whether cellular levels of the cyclin-kinase inhibitor p27Kip1 (also known as p27) in prostate tumors could be used to predict progression of this disease.

METHODS

Levels of p27 in tumor cell nuclei were assessed by immunohistochemical analysis of tissue sections from the primary tumors of 96 patients with stage C prostate carcinoma who had been treated by radical prostatectomy. Tumors were classified into one of the following three groups on the basis of the percentage of tumor cells showing nuclear p27 reactivity: low (0%-10%), moderate (11%-50%), and high (>50%). The Mantel-Haenszel test, Kaplan-Meier analysis, and the logrank test were used to calculate the probability that nuclear p27 levels were associated with tumor grade and substage, with a serum prostate-specific antigen (PSA) recurrence (defined as the finding of a detectable level [0.4 ng/mL or greater] of serum PSA following radical prostatectomy), with the recurrence of clinically evident disease, and with survival. All reported P values are two-sided.

RESULTS

Luminal cells and basal cells of normal prostate glands showed high levels of nuclear p27 immunoreactivity in all tissue sections examined. Fifty-three tumors showed high p27 reactivity, 31 showed moderate reactivity, and 12 showed low or no detectable reactivity. Decreased levels of p27 were associated with tumor grade (P = .004). Tumor levels of p27 were not associated with preoperative prostate-specific antigen levels (P = .360) or with tumor substage (P = .320). However, decreased p27 reactivity was significantly associated with an increased probability of recurrence (P = .004) and decreased survival (P = .010). The median recurrence-free interval for patients with tumors showing high, moderate, or low p27 reactivity was 13.7 years, 8.4 years, and 4.7 years, respectively. Median survival times were more than 14 years, more than 13.5 years, and 8.1 years for patients in the high, moderate, and low p27 reactivity groups, respectively.

CONCLUSION

Levels of nuclear p27 immunoreactivity in the primary tumor can be used to predict recurrence and survival among patients with localized prostate cancer.