p53 expression in incidental prostatic cancer

p53 nuclear accumulation as an early indicator of lethal prostate cancer

Background

After radical prostatectomy (RP) for prostate cancer (PC), p53 alterations predict biochemical relapse (BCR), however, recent evidence suggests that metastatic relapse (MR) not BCR is a surrogate for PC specific mortality (PCSM). This updated analysis of a previously published study investigated the association between p53 aberrations, MR and PCSM in men with localised PC.

Methods

Two hundred and seventy-one men with localised PC treated with RP were included. RP specimens stained for p53 by immunohistochemistry were scored as (a) percentage of p53-positive tumour nuclei; and (b) clustering, where ≥12 p53-positive cells within a ×200 power field was deemed ‘cluster positive’. Associations between p53 status and clinical outcomes (BCR, MR and PCSM) were evaluated.

Results

Increasing percentage of p53-positive nuclei was significantly associated with shorter time to BCR, MR and PCSM (All p < 0.001). Half of the patients were p53 cluster positive. p53 cluster positivity was significantly associated with poorer outcomes at all clinical endpoints (BCR: HR 2.0, 95% CI 1.51–2.65, p < 0.001; MR: HR 4.1, 95% CI 2.02–8.14, p < 0.001; PCSM: HR 12.2, 95% CI 1.6–93; p = 0.016). These associations were independent of other established prognostic variables.

Conclusions

p53 aberrations in radical prostatectomy tissue predict clinically relevant endpoints of MR and PCSM.

p53 selectively regulates developmental apoptosis of rod photoreceptors

Retinal cells become post-mitotic early during post-natal development. It is likely that p53, a well-known cell cycle regulator, is involved in regulating the genesis, differentiation and death of retinal cells. Furthermore, retinal cells are under constant oxidative stress that can result in DNA damage, due to the extremely high level of metabolic activity associated with phototransduction. If not repaired, this damage may result in p53-dependent cell death and ensuing vision loss. In this study, the role of p53 during retinal development and in the post-mitotic retina is investigated. A previously described super p53 transgenic mouse that expresses an extra copy of the mouse p53 gene driven by its endogenous promoter is utilized. Another transgenic mouse (HIP) that expresses the p53 gene in rod and cone photoreceptors driven by the human interphotoreceptor retinoid binding protein promoter was generated. The electroretinogram (ERG) of the super p53 mouse exhibited reduced rod-driven scotopic a and b wave and cone-driven photopic b wave responses. This deficit resulted from a reduced number of rod photoreceptors and inner nuclear layer cells. However, the reduced photopic signal arose only from lost inner retinal neurons, as cone numbers did not change. Furthermore, cell loss was non-progressive and resulted from increased apoptosis during retinal developmental as determined by TUNEL staining. In contrast, the continuous and specific expression of p53 in rod and cone photoreceptors in the mature retinas of HIP mice led to the selective loss of both rods and cones. These findings strongly support a role for p53 in regulating developmental apoptosis in the retina and suggest a potential role, either direct or indirect, for p53 in the degenerative photoreceptor loss associated with human blinding disorders.

RNA silencing of checkpoint regulators sensitizes p53-defective prostate cancer cells to chemotherapy while sparing normal cells

p53 is frequently mutated in patients with prostate cancer, especially in those with advanced disease. Therefore, the selective elimination of p53 mutant cells will likely have an impact in the treatment of prostate cancer. Because p53 has important roles in cell cycle checkpoints, it has been anticipated that modulation of checkpoint pathways should sensitize p53-defective cells to chemotherapy while sparing normal cells. To test this idea, we knocked down ataxia telangiectasia mutated (ATM) gene by RNA interference in prostate cancer cell lines and in normal human diploid fibroblasts IMR90. ATM knockdown in p53-defective PC3 prostate cancer cells accelerated their cell cycle transition, increased both E2F activity and proliferating cell nuclear antigen expression, and compromised cell cycle checkpoints, which are normally induced by DNA damage. Consequently, PC3 cells were sensitized to the killing effects of the DNA-damaging drug doxorubicin. Combining ATM knockdown with the Chk1 inhibitor UCN-01 further increased doxorubicin sensitivity in these cells. In contrast, the same strategy did not sensitize either IMR90 or LNCaP prostate cancer cells, both of which have normal p53. However, IMR90 and LNCaP cells became more sensitive to doxorubicin or doxorubicin plus UCN-01 when both p53 and ATM functions were suppressed. In addition, knockdown of the G(2) checkpoint regulators ATR and Chk1 also sensitized PC3 cells to doxorubicin and increased the expression of the E2F target gene PCNA. Together, our data support the concept of selective elimination of p53 mutant cells by combining DNA damage with checkpoint inhibitors and suggest a novel mechanistic insight into how such treatment may selectively kill tumor cells.

Incidental carcinoma of the prostate: clinicopathological, stereological and immunohistochemical findings studied with logistic regression and self-organizing feature maps

OBJECTIVE

To identify significant predictive factors determining category T1a and T1b in incidental prostatic carcinoma with classical and neural multivariate data analysis methods.

MATERIALS AND METHODS

Incidental prostatic carcinomas diagnosed in our department during 1990-99 (66 cases) were re-examined. Besides acquiring routine clinical and pathological data the tumours were assessed by scoring immunohistochemistry for proliferative activity and p53-overexpression. Tumour vascularization (angiogenesis) and epithelial texture variables were investigated by quantitative stereology. The data were evaluated by classical statistical methods (t-test, correlation analysis, logistic regression). Moreover, self-organizing feature maps (SOMs) were applied as an exploratory approach to unsupervised data analysis by artificial neural networks.

RESULTS

The proliferative fraction, p53 overexpression of tumour cell nuclei, preoperative prostate-specific antigen value and density of capillary vascularization correlated with the Gleason score in incidental prostatic carcinoma. In a stepwise logistic regression analysis with the tumour categories T1a and T1b as dependent variables, the Gleason score and the volume fraction of epithelial cells were significant independent predictors of the tumour category. The cases could be grouped into clusters of different degrees of malignancy using SOMs.

CONCLUSIONS

Texture variables of tumour cells are of central importance for the extent of propagation in the prostate in incidental prostatic adenocarcinomas. Gleason score and quantitative stereological estimates of the volume fraction of tumour cells are significant predictors of T1a and T1b categories of incidental prostatic carcinoma. Unsupervised clustering of T1 prostate carcinoma cases by SOMs correlates well with the dichotomous classification into T1a and T1b according to the UICC.

[Clinical and biological progression of incidental prostatic cancer ( Stage T 1a)]

OBJECTIVES

To analyze the biological and clinical progression of the prostate cancer stage T1a.

MATERIAL AND METHODS

Retrospective study of 44 patients diagnosed of T1a prostate carcinoma between 1985 and 2001. We value biological and clinical progression, time up to the progression, mortality for tumour reason and survival, with the following stratification: patients without initial treatment and patients treated by means of external radiotherapy or radical prostatectomía.

RESULTS

Of all 44 patients biological progression was observed in 5 (11.36%) and clinical progression in 4 (9.09%). The mortality to 5 years for tumour reason was of 2 (4.54%). Of all 38 patients without initial treatment biological progression was observed in 5 (13.15%), in an average time of 25.8 months and clinical progression in 4 (10.52%), in an average time of 34.5 months. The mortality to 5 years was of 2 (5.26%). In all 6 patients to whom radical treatment carried out them progression was not observed and they all live. There are no statistically significant differences between both groups of patients (p = NS).

CONCLUSIONS

The biological and clinical progression of the T1a prostate cancer is low, 11.36% and 9.09%, respectively. The mortality to 5 years is of 4.54%. Differences of survival do not exist, statistically significant, between treated and not treated.

Cell proliferation, apoptosis, oncogene, and tumor suppressor gene status in adenosis with comparison to benign prostatic hyperplasia, prostatic intraepithelial neoplasia, and cancer

There is scant information on the cell proliferation, apoptosis, oncogenes, and tumor suppressor genes status in adenosis. Forty-eight foci of adenosis were studied with immunohistochemistry for MIB-1; c-erbB-2, c-erbB-3, bcl-2 oncogenes; and p53. To evaluate apoptosis, the TdT dUTP nick end labeling (TUNEL) method was applied. Results were compared with the same studies on benign prostatic hyperplasia (BPH) (n = 20), low-grade prostatic intraepithelial neoplasia (PIN) (n = 10); high-grade PIN (n = 20), Gleason sum 2 to 6 cancer (n = 16); and Gleason sum 7 to 10 cancer (n = 22). MIB-1 proliferation index was lowest in BPH, followed by adenosis, low-grade prostatic intraepithelial neoplasia (PIN), low-grade cancer, high-grade PIN, and high-grade cancer. The apoptotic rate was generally low in all groups, although it was higher in PIN and cancer. In BPH and adenosis, bcl-2 was absent in luminal cells. In low- and high-grade PIN, both basal and luminal cells expressed bcl-2, whereas in cancer, expression was found in only 1 case (3%). C-erbB-2 showed absent or low values for cancer and adenosis, whereas it was commonly expressed in BPH and low- and high-grade PIN. Low expression in adenosis was also found with c-erbB-3 (6%) compared with all other groups. Expression of p53 was confined to cancer. Despite a significantly higher proliferation index rate compared with BPH, adenosis showed a markedly lower proliferating index when compared with low-grade PIN, high-grade PIN, and cancer. Expression of the oncogenes c-erbB-2 and cerbB-3 was very low in adenosis, and the staining pattern for bcl-2 was similar to that of BPH. These results provide additional evidence to that of prior studies that adenosis is a histological small acinar proliferation more akin to BPH than high-grade PIN or adenocarcinoma.

Assessment of the biologic markers p53, Ki-67, and apoptotic index as predictive indicators of prostate carcinoma recurrence after surgery

BACKGROUND

This study was designed to evaluate the potential of the molecular and cellular markers p53, Ki-67, and apoptotic index (AI) as adjuncts to the commonly available variables of tumor grade, clinical stage, and serum prostate specific antigen to predict prostate carcinoma recurrence after radical prostatectomy.

METHODS

Representative punch biopsy specimens of prostate carcinoma from whole mount paraffin blocks were evaluated from 47 men who underwent radical prostatectomy. Two groups were defined: those without evidence of prostate carcinoma recurrence after 5 years of follow-up (N = 30) and those with carcinoma recurrence (N = 17). Gleason grade, clustered p53 immunostaining, Ki-67 immunostaining, and AI were determined by standard techniques.

RESULTS

All variables tested were associated with disease recurrence by univariate analysis: AI (P = 0.005), clustered p53 immunostaining (P = 0.0070), and Ki-67 immunostaining (P = 0.0390). Using multivariate analyses that included each biomarker with routinely available features, only AI (P = 0.0234) and clustered p53 immunostaining (P = 0.0389) added independent prognostic information (Ki-67 immunostaining, P = 0.1285). In the final logistic regression model that included standard variables with AI and p53, only AI reached statistical significance (P = 0.0332).

CONCLUSIONS

The continued assessment of additional biomarkers for prostate carcinoma recurrence is important to identify better those patients who may be candidates for early adjuvant therapy and also to further our understanding of the neoplastic potential of a particular malignancy.

Involvement of the multiple tumor suppressor genes and 12-lipoxygenase in human prostate cancer. Therapeutic implications

We performed a detailed and comprehensive study of the involvement of tumor suppressor genes in human prostate cancer. We utilized primers flanking either the restriction fragment length polymorphism (RFLP) or variable number of tandem repeat [VNTR; microsatellite or simple repeat site (SRS)] polymorphic sites to polymerase chain reaction (PCR) amplify the genomic DNA and detect loss of heterozygosity of the target genes. Quantitative reverse transcription (RT)-PCR was performed to measure the mRNA expression levels and PCR/single strand conformational polymorphism (SSCP) and DNA sequencing carried out to detect mutation of the tumor suppressor genes. We found that multiple tumor suppressor genes (e.g., p53, DCC, APC, MCC, BRCA1, and WAF1/CIP1) were inactivated at different frequencies via various mechanisms [e.g., loss of heterozygosity (LOH), loss of expression (LOE), mutation, and inactivation by cellular binding protein]. Several important and novel findings are as following: LOH and LOE of the DCC gene, LOH, LOE, and possible mutation of the APC/MCC genes, LOH of the BRCA1 locus, and mutation of the WAF1/CIP1 gene. For p53 tumor suppressor gene alone, multiple inactivation mechanisms (i.e., LOH, LOE, mutation, and amplification of the cellular inactivating protein MDM2) were identified. A possible involvement of genomic instability or mutator phenotype in human prostate cancer was investigated by microsatellite typing using PCR. A high frequency of microsatellite instability was detected and the microsatellite instability found to correlate with advanced stage and poor differentiation of prostate cancer, suggesting that genes functioning in DNA mismatch repair or general stabilization of the genome may be involved in prostate cancer. The results obtained in this study suggested that multiple tumor suppressor genes (both known and unknown genes) may share the role in prostate cancer; a pattern which has been found in a number of human malignancies such as cancers of the esophagus, colon and breast. In fact, we performed deletion studies aimed at localizing potential tumor suppressor loci on various chromosomal regions. A number of chromosomal regions (i.e., 6p12-24 and 17q21) were found to potentially harbor unidentified tumor suppressor genes. Detailed deletion mapping has localized the potential tumor suppressor loci to a < 2 Mb region centromeric to the BRCA1 gene on chromosome 17q. In addition, we identified a number of novel mechanisms of tumor suppressor gene inactivation, in prostate cancer such as loss of mRNA expression of the DCC, APC, MCC and p53 gene, and mutator phenotype. And for the very first time, we identified somatic mutations of the WAF1/CIP1 gene in primary human malignancy-human prostate cancer. This finding provides the first evidence in primary tumor that the WAF1/CIP1 gene may be a tumor suppressor gene and may be involved in prostate cancer. We identified 12-lipoxygenase (12-LOX) as a potential prognostic marker for human prostate cancer. mRNA expression levels of the 12-LOX gene was measured by quantitative reverse transcription-polymerase chain reaction (RT-PCR) and semi-quantitative in situ hybridization (ISH) in 122 pairs of matched normal and tumor tissues from prostate cancer patients. We found that 12-LOX expression levels were elevated in approximately half of the patients analyzed and the 12-LOX elevation correlates with advanced stage, poor differentiation, and surgical margin positivity. Our data suggest that 12-LOX may serve as a correlative marker for a more aggressive phenotype of prostate cancer and therefore for poor prognosis. We are currently refining our assays for possible clinical applicability. Since not all patients with loss of expression of the DCC gene showed LOH of the DCC locus, there must be other mechanism(s) responsible for loss of expression of the DCC gene. When we analyzed the relationship between DCC loss of expression and 12-LOX elevation in prostate cancer pati

Prognostic significance of cytoplasmic p53 overexpression in colorectal cancer. An immunohistochemical analysis

p53 overexpression was studied by immunohistochemistry in 96 consecutive colorectal cancer patients, subdividing positive specimens according to two staining patterns: cytoplasmic or nuclear. Forty-seven per cent of the cases were p53 positive, a significant correlation being found with Dukes' stage (P = 0.0036). A prevalence of nuclear staining was observed in Dukes' B and cytoplasmic in Dukes' D stages. After 36 months, 23% of the patients had a recurrence, and 45% were p53 positive, all Dukes' C-D stage with cytoplasmic staining. The Kaplan-Meier curve showed a significant correlation between p53 cytoplasmic staining and disease-free survival period (P = 0.002). With respect to disease-free survival, the Cox proportional hazard regression test, comparing p53 positivity with Dukes' stage, showed the latter to be the most significant variable. In our series of patients, advanced Dukes' stage tumours were localised in the right colon, where a higher percentage of p53 positivity (67% versus 40% of the left side), as well as a higher frequency of cytoplasmic staining was observed. In conclusion, from the data obtained, a strong correlation between p53 cytoplasmic staining and patient prognosis is clearly indicated.

Immunoreactive p53 protein in high-grade prostatic intraepithelial neoplasia

p53 protein accumulation in the nuclei of prostatic carcinoma cells, as detected by immunohistochemistry, has been associated with increased cell proliferation rate, increased histologic grade and stage, androgen independence and decreased patient survival. Little is known, however, of p53 in prostatic intraepithelial neoplasia (PIN), the putative precursor proliferation for moderately to poorly differentiated peripheral zone carcinoma of the prostate. In this investigation, we utilized a panel of antibodies reactive with p53 protein to assess p53 protein accumulation in prostatic epithelial hyperplasia, PIN and prostatic carcinoma. Forty patients who had undergone radical prostatectomy were selected for study based on the presence of high grade PIN and carcinoma in the same prostate tissue block. Tissue sections were treated with microwave irradiation for antigen retrieval, and antibodies DO-7, PAb1801 and CM-1 were used for immunohistochemical analysis. An intense signal for immunoreactive p53 was identified in the nuclei of 7/40 (17.5%) clinically-localized prostatic carcinomas. In all 7 cases, high grade PIN also exhibited intense p53 immunoreactivity, whereas only one case of hyperplasia contained immunoreactive p53 protein. These findings support a close relationship between high grade PIN and carcinoma in a subset of primary prostatic carcinomas with high-level p53 protein accumulation.

Frequency and characterization of p53 mutations in clinically localized prostate cancer

OBJECTIVES

To determine the frequency of abnormal p53 expression and to characterize confirmed p53 mutations in tumors from patients with clinically localized adenocarcinoma of the prostate.

METHODS

p53 protein nuclear accumulation was determined immunohistochemically in the initial diagnostic tumor specimens from 37 patients with clinically localized prostate carcinoma. Two primary antibodies were used on all specimens. Structural analysis of the p53 gene was performed using the methods of polymerase chain reaction (PCR)/single-strand conformation polymorphism (SSCP) and DNA sequencing.

RESULTS

In 1 of the 37 (2.7%) tumor specimens, intense p53 nuclear staining was demonstrated using either antibody PAb 1801 or CM-1. The staining in this case was heterogeneous, with approximately 40% of tumor nuclei staining for p53. This tumor specimen was microdissected and DNA was extracted. Following PCR amplification, abnormally migrating bands were noted on SSCP analysis of exon 8. DNA sequencing confirmed the mutation as a C-->A transversion in codon 281 (asp-->glu). PCR/SSCP analysis of exons 5 through 8 was also performed for seven additional tumors that were negative for p53 nuclear accumulation by immunohistochemical (IHC) methods. All of these specimens demonstrated wild-type p53.

CONCLUSIONS

The results of this study confirm and extend our previous findings that p53 mutations are rare in clinically localized adenocarcinoma of the prostate. In detecting clonal p53 mutations, standard immunohistochemical technique correlates reliably with structural p53 gene analysis of the evolutionary conserved domains encompassing exons 5-8. Importantly, most reports have demonstrated that p53 mutations detected by IHC are a late step in the progression of prostate cancer and are associated with advanced disease, dedifferentiation, and the acquisition of androgen independence.

Immunohistochemical detection of p53 protein in human prostatic cancer

Tissue sections from 73 radical-prostatectomy specimens were studied immunohistochemically for the presence of p53 protein. In seven specimens numerous tumor cells showed a strong nuclear immunostaining. An additional 27 revealed a more discrete and focal accumulation of p53 protein. Comparison of the pathologic characteristics of the p53-negative and -positive groups showed that the presence of p53 protein closely correlated with more advanced tumor stages (p < 0.00001), with higher primary (p = 0.0004), combined (p < 0.0001) and worst (p < 0.0001) Gleason grades, and with larger total (p = 0.0001) and high-grade (p < 0.0001) tumor volumes. No staining was found in areas of benign hyperplasia or in well-differentiated tumor zones. Our results suggest that the accumulation of p53 protein to immunohistochemically detectable concentrations is not a feature of low-grade cancer. This finding implies that abnormal p53 accumulation might be involved in the process of prostatic cancer progression.