Tumor suppressor gene p53 mutations in human prostate cancer

TP53, SPOP and PIK3CA Genes Status in Prostate Cancer

Recent advances in molecular biology make the identification of prostate cancer (PC) subsets a priority for more understanding of the molecular pathogenesis and treatment options. Genetic alterations in many genes such as TP53, SPOP and PIK3CA genes have been reported in PC with variable frequencies worldwide. We aimed to investigate genetic alterations in the hotspot lesions of TP53, SPOP and PIK3CA genes by direct sequencing and the expression of TP53 and PIK3CA by RT-PCR in prostate cancer, and to explore the correlation between TP53, SPOP and PIK3CA alterations and tumorigenesis of prostate cancer. Seventy-nine FFPE prostate samples from patients who underwent radical prostatectomy were obtained, subjected to genomic DNA extraction and sequenced for mutations in exons 5, 6, 7 and 8 of TP53 gene, exons 4 and 5 of SPOP gene and exons 9 and 20 of PIK3CA gene. RT-PCR was performed for the expression evaluation of the PIK3CA gene. Our results showed a high frequency of TP53 mutations (11/79, 13.9 %) in the selected population. On the other hand, SPOP and PIK3CA genes did not show any genetic alteration in the sequenced exons. PIK3CA gene overexpression was detected in 6% of the cohort by RT-PCR. TP53 mutation is the most frequent genetic alteration and likely has a major role in the pathogenesis of PC in the Jordanian population.

Identification of novel prostate cancer drivers using RegNetDriver: a framework for integration of genetic and epigenetic alterations with tissue-specific regulatory network

We report a novel computational method, RegNetDriver, to identify tumorigenic drivers using the combined effects of coding and non-coding single nucleotide variants, structural variants, and DNA methylation changes in the DNase I hypersensitivity based regulatory network. Integration of multi-omics data from 521 prostate tumor samples indicated a stronger regulatory impact of structural variants, as they affect more transcription factor hubs in the tissue-specific network. Moreover, crosstalk between transcription factor hub expression modulated by structural variants and methylation levels likely leads to the differential expression of target genes. We report known prostate tumor regulatory drivers and nominate novel transcription factors (ERF, CREB3L1, and POU2F2), which are supported by functional validation.

Reactivation of mutant p53 by a dietary-related compound phenethyl isothiocyanate inhibits tumor growth

Mutations in the p53 tumor-suppressor gene are prevalent in human cancers. The majority of p53 mutations are missense, which can be classified into contact mutations (that directly disrupts the DNA-binding activity of p53) and structural mutations (that disrupts the conformation of p53). Both of the mutations can disable the normal wild-type (WT) p53 activities. Nevertheless, it has been amply documented that small molecules can rescue activity from mutant p53 by restoring WT tumor-suppressive functions. These compounds hold promise for cancer therapy and have now entered clinical trials. In this study, we show that cruciferous-vegetable-derived phenethyl isothiocyanate (PEITC) can reactivate p53 mutant under in vitro and in vivo conditions, revealing a new mechanism of action for a dietary-related compound. PEITC exhibits growth-inhibitory activity in cells expressing p53 mutants with preferential activity toward p53^R175, one of the most frequent ‘hotspot' mutations within the p53 sequence. Mechanistic studies revealed that PEITC induces apoptosis in a p53^R175 mutant-dependent manner by restoring p53 WT conformation and transactivation functions. Accordingly, in PEITC-treated cells the reactivated p53^R175 mutant induces apoptosis by activating canonical WT p53 targets, inducing a delay in S and G2/M phase, and by phosphorylating ATM/CHK2. Interestingly, the growth-inhibitory effects of PEITC depend on the redox state of the cell. Further, PEITC treatments render the p53^R175 mutant sensitive to degradation by the proteasome and autophagy in a concentration-dependent manner. PEITC-induced reactivation of p53^R175 and its subsequent sensitivity to the degradation pathways likely contribute to its anticancer activities. We further show that dietary supplementation of PEITC is able to reactivate WT activity in vivo as well, inhibiting tumor growth in xenograft mouse model. These findings provide the first example of mutant p53 reactivation by a dietary compound and have important implications for cancer prevention and therapy.

Nuclear iASPP may facilitate prostate cancer progression

One of the major challenges in prostate cancer (PCa) research is the identification of key players that control the progression of primary cancers to invasive and metastatic disease. The majority of metastatic PCa express wild-type p53, whereas loss of p63 expression, a p53 family member, is a common event. Here we identify inhibitor of apoptosis-stimulating protein of p53 (iASPP), a common cellular regulator of p53 and p63, as an important player of PCa progression. Detailed analysis of the prostate epithelium of iASPP transgenic mice, iASPP^Δ8/Δ8 mice, revealed that iASPP deficiency resulted in a reduction in the number of p63 expressing basal epithelial cells compared with that seen in wild-type mice. Nuclear and cytoplasmic iASPP expression was greater in PCa samples compared with benign epithelium. Importantly nuclear iASPP associated with p53 accumulation in vitro and in vivo. A pair of isogenic primary and metastatic PCa cell lines revealed that nuclear iASPP is enriched in the highly metastatic PCa cells. Nuclear iASPP is often detected in PCa cells located at the invasive leading edge in vivo. Increased iASPP expression associated with metastatic disease and PCa-specific death in a clinical cohort with long-term follow-up. These results suggest that iASPP function is required to maintain the expression of p63 in normal basal prostate epithelium, and nuclear iASPP may inactivate p53 function and facilitate PCa progression. Thus iASPP expression may act as a predictive marker of PCa progression.

Molecular pathways and targets in prostate cancer

Prostate cancer co-opts a unique set of cellular pathways in its initiation and progression. The heterogeneity of prostate cancers is evident at earlier stages, and has led to rigorous efforts to stratify the localized prostate cancers, so that progression to advanced stages could be predicted based upon salient features of the early disease. The deregulated androgen receptor signaling is undeniably most important in the progression of the majority of prostate tumors. It is perhaps because of the primacy of the androgen receptor governed transcriptional program in prostate epithelium cells that once this program is corrupted, the consequences of the ensuing changes in activity are pleotropic and could contribute to malignancy in multiple ways. Following localized surgical and radiation therapies, 20-40% of patients will relapse and progress, and will be treated with androgen deprivation therapies. The successful development of the new agents that inhibit androgen signaling has changed the progression free survival in hormone resistant disease, but this has not changed the almost ubiquitous development of truly resistant phenotypes in advanced prostate cancer. This review summarizes the current understanding of the molecular pathways involved in localized and metastatic prostate cancer, with an emphasis on the clinical implications of the new knowledge.

Transgenic models for prostate cancer research

The ability to introduce novel or specifically altered genes into the germ line of mice and directly perturb gene expression in a specific tissue can facilitate characterization of the molecular mechanisms governing transformation of differentiating tissue within the context of an intact developing animal. Transgenics provide a powerful and remarkably flexible system that can be used to study the cooperation between proto-oncogenes, tumor suppressor genes, and other epigenetic factors in the development of cancer.

Mutations in the p53 Tumor Suppressor Gene: Important Milestones at the Various Steps of Tumorigenesis

Inactivation of the p53 tumor suppressor is a frequent event in tumorigenesis. In most cases, the p53 gene is mutated, giving rise to a stable mutant protein whose accumulation is regarded as a hallmark of cancer cells. Mutant p53 proteins not only lose their tumor suppressive activities but often gain additional oncogenic functions that endow cells with growth and survival advantages. Interestingly, mutations in the p53 gene were shown to occur at different phases of the multistep process of malignant transformation, thus contributing differentially to tumor initiation, promotion, aggressiveness, and metastasis. Here, the authors review the different studies on the involvement of p53 inactivation at various stages of tumorigenesis and highlight the specific contribution of p53 mutations at each phase of cancer progression.

Molecular staging of prostate cancer in the year 2007

Numerous attempts towards improving patient management by molecular staging have been fruitless so far. No single molecular parameter is routinely analyzed in prostate cancer tissue. This may be partly due to genuine properties of prostate cancer that may make this tumor a difficult target. Furthermore, inherent logistical problems result in a shortage of prostate cancer tissue for research purposes. For the future, it can be hoped that the availability of more powerful molecular techniques in combination with better tissue archives will allow more rapid progress. Powerful DNA array and proteomics methods allow the systematic analysis of virtually all genes of a cancer on the DNA, RNA, and protein level. Although such approaches are sometimes labeled as "fishing expeditions," it cannot be totally disregarded that the simultaneous analysis of all genes has a high likelihood of identifying significant new information. In future, one of the major scientific challenges will be the validation of several potential biomarkers in large enough and clinically well-characterized patient cohorts. In particular, studies on needle core biopsies and hormone refractory cancers are imperatively needed for investigating the natural history of the disease or to discover potential predictive markers for radiation therapy and new therapeutic target genes to answer the clinically most important questions for optimal clinical decision making in prostate cancer patients: which patients will not require local therapy? If local therapy is needed, what is the treatment of choice? What medications should be given if metastases are present?

Lunasin: a cancer-preventive soy peptide

Lunasin is a novel, cancer-preventive peptide whose efficacy against chemical carcinogens and oncogenes has been demonstrated in mammalian cells and in a skin cancer mouse model. Isolated and characterized in soy, lunasin peptide is also documented in barley. Lunasin is found in all of the genotypes analyzed from the US soy germ plasm collection and in commercially available soy proteins. Pilot studies show that lunasin is bioavailable in mice and rats when orally ingested, opening the way for dietary administration in cancer prevention studies. Lunasin internalizes into mammalian cells within minutes of exogenous application, and localizes in the nucleus after 18 hours. It inhibits acetylation of core histones in mammalian cells. In spite of its cancer-preventive properties, lunasin does not affect the growth rate of normal and established cancer cell lines. An epigenetic mechanism of action is proposed whereby lunasin selectively kills cells being transformed or newly transformed by binding to deacetylated core histones exposed by the transformation event, disrupting the dynamics of histone acetylation-deacetylation and leading to cell death.

Transgenic mouse with human mutant p53 expression in the prostate epithelium

BACKGROUND

Apoptosis is disrupted in prostate tumor cells, conferring a survival advantage. p53 is a nuclear protein believed to regulate cancer progression, in part by inducing apoptosis. To test this possibility in future studies, the objective of the present study was to generate a transgenic mouse model expressing mutant p53 in the prostate (PR).

METHODS

Transgene incorporation was tested using Southern analysis. Expression of mutant p53 protein was examined using immunofluorescence microscopy. Apoptosis in the PR was evaluated using the Tunnel method.

RESULTS

A construct, consisting of the rat probasin promoter and a mutant human p53 fragment, was prepared and used to generate transgenic mice. rPB-mutant p53 transgene incorporation, as well as nuclear accumulation of mutant human p53 protein, was demonstrated. Prostatic intraepithelial neoplasia (PIN) III and IV were found in PR of 52-week old transgenic mice, whereas no pathological changes were found in the other organs examined. PR ability to undergo apoptosis following castration was reduced in rPB-mutant p53 mice as compared to non transgenic littermates.

CONCLUSIONS

Transgenic rPB-mutant p53 mice accumulate mutant p53 protein in PR, resulting in neoplastic lesions and reduced apoptotic potential in the PR. Breeding rPB-mutant p53 mice with mice expressing an oncogene in their PR will be useful in examining interactions of multiple genes that result in progression of slow growing prostate tumors expressing oncogenes alone to metastatic cancer.

Muscarinic receptors in cell lines from ovarian carcinoma: negative correlation with survival of patients

OBJECTIVES

Tumor cells are similar in many respects to embryonic cells, indicating that embryonic genes are reactivated during malignant growth. In previous studies, we observed muscarinic acetylcholine receptors, which are expressed in embryonic cells during morphogenesis and are also found in human melanomas and melanoma cell lines. We determined the presence of muscarinic receptors in a collection of ovarian tumor cell lines for which clinical data were available.

METHODS

Muscarinic receptor status of 39 cell lines derived from 34 patients was determined by Western blotting.

RESULTS

Twenty-three cell lines were receptor positive, and 16, receptor negative. Kaplan-Meier analysis of receptor status of the tumor cell lines and survival time of patients from which the cell lines were established showed that expression of muscarinic receptors was associated with a reduced probability (P = 0.025) of survival: This is within the range of other established prognostic factors reported in the literature.

CONCLUSIONS

A large percentage of ovarian tumor cell lines express muscarinic receptors. Muscarinic receptor expression is an embryonic trait and is correlated with reduced survival of patients. The results from this study provide further evidence of the involvement of muscarinic receptors in the progression of malignant carcinomas.

p53 gene alterations in prostate cancer after radiation failure and their association with clinical outcome: a molecular and immunohistochemical analysis

This study evaluates the prevalence of p53 gene mutations in prostate cancer in salvage prostatectomies after radiation failure using single strand conformational polymorphism (SSCP) and direct sequencing of the polymerase chain reaction (PCR) product. Findings were correlated with immunohistochemically (IHC) detectable p53 expression in residual prostate cancer. The usefulness of p53 as a marker of clinical outcome was evaluated. Thirty-three cases were available for molecular and immunohistochemical analysis. Immunohistochemical stains for p53 were performed with clone DO7. PCR-SSCP for mutations in the coding region of p53 DNA (exons 4-9) was performed on all immunopositive cases and 12 of 23 immunonegative cases. All samples with an SSCP shift were sequenced for the respective exon. Patients were evaluated for biochemical failure for 1-82 months (median 38 months) following surgery. Immunohistochemical p53 reactivity was noted in 10 of 33 (30%) patients. Among p53 immunopositive cases SSCP shifts were seen in 7 of 10 (70%) samples with 5 of the 7 (71%) showing p53 mutations. Univariate analysis revealed abnormal expression of p53 protein by immunohistochemistry to be a significant predictor of poorer outcome (p = 0.025, log rank), however this was not independent of pathologic stage, surgical margin status and Gleason score. The presence of p53 gene mutations by PCR-SSCP and direct sequencing did not predict for outcome. In our study 30% of prostate cancers at the time of salvage prostatectomy after radiation failure expressed immunohistochemically detectable p53. PCR-SSCP and sequencing shows that not all of these cases have detectable mutations in the most frequent mutation sites (exons 4-9). Clinical failure is more common in the group of prostate cancer patients with abnormal p53 immunoreactivity.

Prostate Cancer - Old Problems and New Approaches. (Part II. Diagnostic and Prognostic Markers, Pathology and Biological Aspects)

Diagnostic and prognostic markers for prostatic cancer (PCa) include conventional protein markers (e.g., PAP, PSA, PSMA, PIP, OA-519, Ki-67, PCNA, TF, collagenase, and TIMP 1), angiogenesis indicator (e.g., factor VIII), neuroendocrine differentiation status, adhesion molecules (E-cadherin, integrin), bone matrix degrading products (e.g., ICPT), as well as molecular markers (e.g., PSA, PSMA, p53, 12-LOX, and MSI). Currently, only PSA is used clinically for early diagnosis and monitoring of PCa. The histological differential diagnosis of prostatic adenocarcinoma includes normal tissues such as Cowper's gland, paraganglion tissue and seminal vesicle or ejaculatory duct as well as pathological conditions such as atypical adenomatous hyperplasia, atrophy, basal cell hyperplasia and sclerosing adenosis. A common PCa is characterized by a remarkable heterogeneity in terms of its differentiation, microscopic growth patterns and biological aggressiveness. Most PCa are multifocal with signi ficant variations in tumor grade between anatomically separated tumor foci. The Gleason grading system which recognizes five major grades defined by patterns of neoplastic growth has gained almost uniform acceptance. In predicting the biologic behavior of PCa clinical and pathological stages are used as the major prognostic indicators. Among the cell proliferation and death regulators androgens are critical survival factors for normal prostate epithelial cells as well as for the androgen-dependent human prostatic cancer cells. The androgen ablation has been shown to increase the apoptotic index in prostatic cancer patients and castration also promotes apoptotic death of human prostate carcinoma grown in mice. The progression of PCa, similarly to other malignancies, is a multistep process, accompanied by genetic and epigenetic changes, involving phenomenons as adhesion, invasion and angiogenesis (without prostate specific features).

The use of multicolor fluorescence technologies in the characterization of prostate carcinoma cell lines: a comparison of multiplex fluorescence in situ hybridization and spectral karyotyping data

Recent studies have identified several chromosome regions that are altered in primary prostate cancer and prostatic carcinoma cell lines. These targeted regions may harbor genes involved in tumor suppression. We used multiplex fluorescence in situ hybridization (M-FISH) to screen for genetic rearrangements in four prostate cancer cell lines, LNCaP, LNCaP.FCG, DU145, and PC3, and compared our results with those recently obtained using spectral karyotyping (SKY). A number of differences was noted between abnormalities characterized by SKY and M-FISH, suggesting variation in karyotype evolution and characterization by these two methodologies. M-FISH analysis showed that hormone-resistant cell lines (DU145 and PC3) contained many genetic alterations (> or =15 per cell), suggesting high levels of genetic instability in hormone-refractory prostate cancer. Most chromosome regions previously implicated in prostate cancer were altered in one or more of these cell lines. Several specific chromosome aberrations were also detected, including a del(4)(p14) and a del(6)(q21) in the hormone-insensitive cell lines, a t(1;15)(p?;q?) in LNCaP, LNCaP, and PC3, and a i(5p) in LNCaP.FCG, DU145, and PC3. These clonal chromosome abnormalities may pinpoint gene loci associated with prostate tumourigenesis, cancer progression, and hormone sensitivity.

Signaling for the caspases: their role in prostate cell apoptosis

PURPOSE

The caspases are an evolutionary conserved family of cell death proteases. Their activation during apoptosis is an important underlying theme in prostate cancer therapy. We summarize the signaling pathways leading to the recruitment of the caspases and address the importance of recent therapeutic strategies aimed at specifically targeting these proteases in relation to prostate cancer.

MATERIALS AND METHODS

We present a background introduction into the role of the caspases in apoptosis and how failure to signal effectively their activation may contribute to prostate cancer progression. Key studies aimed at specifically targeting the caspases as cancer therapy are discussed.

RESULTS

Prostate carcinogenesis and apoptosis are related. The deregulation of apoptosis contributes to tumor initiation, metastasis and progression to the androgen insensitive state. Conversely the effectiveness of therapy often depends on its ability to induce apoptosis in prostate cancer cells. Identifying abnormalities in the apoptotic signaling pathway has greatly contributed to understanding the biology of prostate cancer. Elucidating caspase regulation has contributed to the design of novel therapies for prostate cancer.

CONCLUSIONS

We summarize the physiological and pathological pathways leading to caspase activation in the prostate and describe novel approaches that target these proteases.

Use of a yeast assay to detect functional alterations in p53 in prostate cancer: review and future directions

BACKGROUND

While many studies have suggested that p53 mutations are common in human cancers, the functional activity of these mutant alleles has not yet been fully addressed. We believe that information about the functional status of individual p53 mutants will prove to be important for a better understanding of the role of p53 in tumor development and progression. Ultimately, this information could also influence treatment decisions for individual cancer patients.

METHODS

A recently developed yeast functional assay can be used to assess the transactivational activity of p53 mutants. Furthermore, this assay is more sensitive than single strand conformational polymorphism (SSCP) for detection of p53 mutations. In this review, we summarize the mechanism of this new technique and describe its applications in cancer research, with an emphasis on prostate cancer.

RESULTS

The use of the yeast functional assay provides a simple, sensitive, and reproducible method for detecting p53 mutations and for determining the transactivational activity and dominant-negative role of individual p53 mutants.

CONCLUSIONS

This method may be adapted to analyze other transcriptional factors, including the human androgen receptor.

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.

Cyclin D1 expression in human prostate carcinoma cell lines and primary tumors

BACKGROUND

The cyclin D1 gene is amplified and/or overexpressed in several types of human cancer, including cancers of the breast, esophagus, head, and neck. However, the role of cyclin D1 in prostate cancer has not been previously studied in detail.

METHODS

Six human prostate cancer cell lines and cultures of normal human prostate cells were examined by Western and Northern blot analyses for levels of expression of the cyclin D1 protein and mRNA, respectively. Southern blot analyses were performed to examine possible amplification of this gene. Immunostaining for cyclin D1 was performed on 50 primary prostate cancer samples.

RESULTS

Cyclin D1 protein was expressed at relatively high levels in all of the six human prostate cancer cell lines examined, but was not detected in the cultures of normal human prostate cells. The ALVA 41 cell line expressed the highest level of this protein. Relatively high levels of cyclin D1 mRNA were also found in all of the prostate cancer cell lines. Nevertheless, none of these cell lines revealed amplification of the cyclin D1 gene. Twelve of the 50 primary prostate cancer samples (24%) revealed regions of moderate to strongly positive staining for cyclin D1.

CONCLUSIONS

The increased expression of cyclin D1 in several prostate cancer cell lines and in a subset of primary prostate cancer samples suggests that further studies on the expression of this gene and related genes may be of interest in understanding the pathogenesis of prostate cancer.

The prognostic value of p53 for long-term and recurrence-free survival following radical prostatectomy

In the present study, 76 specimens (T1-T4) from 76 randomly selected patients undergoing radical prostatectomy at Hannover University as well as in the Josef Hospital Regensburg (13 patients) between 1980 and 1992 for whom tissue sections for immunohistochemical investigation were available, were investigated for different biological and clinical characteristics as predictors for long-term and recurrence-free survival: age, depth of tumour infiltration, histological grade, lymph node status, as well as overexpression of the p53 protein (monoclonal antibody DO-1). After a median follow-up of 50 months, 6 of 18 patients (33%) with more than 20% of tumour cells stained positively for p53 died from tumour progression compared with 9 of 58 patients (16%) with less than 20% of tumour cells positive for p53. During univariate analysis, p53 overexpression (P = 0.011), histological grading (P = 0.009) and tumour stage (P = 0.024) were significant prognostic factors for survival, among which only p53 overexpression (P = 0.026) remained an independent significant predictor in multivariate analysis. Additionally, 18 of 66 patients (27%) with less than 40% positivity for p53 suffered tumour recurrence in contrast to 6 of 10 patients (60%) with more than 40% tumour cells exhibiting a positive staining reaction. In multivariate analysis, p53 overexpression was identified as the only prognostic parameter for recurrence-free survival (P = 0.005). Prospective studies are needed to confirm the independent prognostic potential of p53 overexpression in patients with localised prostate cancer. The availability of more refined prognostic factors should assist decision making regarding the value of radical prostatectomy versus a surveillance strategy for prognostically defined subgroups of patients.

Nuclear p53 overexpression in bladder, prostate, and renal carcinomas

BACKGROUND

The aim of this study was to examine nuclear p53 overexpression in transitional cell carcinoma of the bladder, adenocarcinoma of the prostate, and renal cell carcinoma.

METHODS

Forty-four pathologic specimens from 39 bladder cancer patients, 41 prostatic adenocarcinoma, and 39 renal cell carcinoma specimens were analyzed immunohistochemically with D07 monoclonal antibody to detect the expression of the mutant p53 gene. Overexpression was said to occur when the number of positively-stained tumor nuclei were > or = 10% in each specimen. p53 overexpression was correlated with the clinical and histopathological features of these cancers.

RESULTS

Nuclear p53 overexpression occurred in 18.2% of transitional cell bladder cancer specimens, 12.2% of prostate cancer specimens, and 17.9% of renal cell cancer specimens. Statistical analyses showed that grade, vascular invasion, and necrosis in bladder cancer, a high Gleason score in prostate cancer, and the 1-year mortality rate in renal cancer were significantly related with p53 nuclear overexpression (P < 0.05).

CONCLUSION

Using the D07 monoclonal antibody, nuclear p53 overexpression is relatively uncommon in urologic malignancies, and moderately correlates with several histopathological and clinical features of urologic malignancies.

Abnormal p53 expression is rare in clinically localized human prostate cancer: comparison between immunohistochemical and molecular detection of p53 mutations

BACKGROUND

We assessed the frequency and molecular basis of p53 mutations in clinically localized prostatic adenocarcinoma.

METHODS

Prostate specimens were examined from 100 patients with clinically localized prostatic adenocarcinoma and 13 patients with benign prostatic hyperplasia (BPH). Mutations producing nuclear accumulation of p53 were detected immunohistochemically. Exon-specific mutations were analyzed by polymerase chain reaction amplification and single strand conformation polymorphism (PCR-SSCP) and sequenced.

RESULTS

p53 accumulation was detected in 5 tumors using antibody DO-1, and in 4 of these using antibody PAb 1801, but not in BPH. PCR-SSCP detected mutations in all 5 tumors, with alterations in exon 5 for 1 tumor, exon 6 for 3 tumors, and exon 7 for 1 tumor. An exon 6 mutation was also found in a tumor with no anti-p53 staining.

CONCLUSIONS

p53 mutations are uncommon in clinically localized prostatic adenocarcinoma and absent from BPH. 5 of the 6 mutations were derived from locally invasive, prostate carcinomas, supporting the hypothesis that mutation of p53 is a late event in prostate carcinoma progression.

Diagnostic and prognostic markers for human prostate cancer

BACKGROUND

The incidence and mortality of prostate cancer are increasing at alarming rates, partially due to an aging population. Early detection of prostate cancer, using clinically sensitive procedures and/or tumor markers (e.g., prostate-specific antigen [PSA]), is of prime importance. However, the choice of therapeutic interventions for prostate cancer at the time of diagnosis is largely dependent on clinical and pathologic staging and prediction of the degree of aggressiveness of the disease. Clinically applicable prognostic markers are urgently needed to assist in the selection of optimal therapy.

METHODS

Literature review of the potential diagnostic and prognostic markers for human prostate cancer.

RESULTS

Well-established tissue prognostic indicators, including histologic grade, margin positivity, pathologic stage, intraglandular tumor extent, and DNA ploidy, are not reviewed in this paper. Recently, a number of novel markers have been identified. In this paper, we begin with a discussion of a number of well-established as well as investigational diagnostic markers and then focus on evaluation of prognostic markers. Diagnostic markers that have prognostic value and investigational prognostic markers are also discussed.

CONCLUSIONS

Currently, only PSA is utilized for early diagnosis and monitoring of prostate cancer. A number of potential prognostic markers warrant further investigation. Multimarker analysis is implicated.

Immortalized and tumorigenic adult human prostatic epithelial cell lines: characteristics and applications. Part 3. Oncogenes, suppressor genes, and applications

This is Part 3 of a three-part review. It deals with the possible role of oncogenes and suppressor genes in human prostate carcinoma as well applications of nontumorigenic and tumorigenic human prostate cell lines described in Parts 1 and 2 [1,2]. Several immortalized and malignant adult human prostatic epithelial cell lines have recently been developed. The three most widely used carcinoma cell lines, DU-145, PC-3, and LNCaP, developed between 1977 and 1980, have greatly contributed to our present understanding of prostate cancer. Before a cell line can be accepted as having prostatic epithelial origin, some basic characteristics must be established. Expression of specific cytokeratins but absence of desmin and factor VIII should be first determined to establish epithelial origin. Responsiveness to androgens and expression of androgen receptor and prostate-specific antigen should be examined under stringent culture conditions to establish prostatic epithelial origin. Response to growth factors and expression of their receptors facilitates further characterization of cell behavior. Cell lines immortalized by human papillomaviruses (HPVs) are of special interest because HPVs are involved in a variety of anogenital cancers and may also play a role in prostate carcinogenesis. Malignant transformation of HPV-18 immortalized cells with the ras oncogene provides cell systems for investigating the multistep process of carcinogenesis. Each cell line has some unique characteristics, whether it arose directly from a carcinoma or resulted from immortalization with simian virus 40 (SV40) or HPV, or was transformed in vitro by oncogenes. Comparisons of these characteristics should facilitate elucidation of the mechanisms involved in initiation, promotion and progression of prostate cancer. These cell lines will further serve as useful models for investigating tumor progression, invasion, metastasis, new therapeutic strategies, drug resistance and its reversal and chemoprevention. This review summarizes some applications of the currently available immortalized, non-tumorigenic as well as the tumorigenic adult human prostatic epithelial cell lines.

Molecular biology of prostatic intraepithelial neoplasia

High-grade PIN is the most likely precursor of prostatic adenocarcinoma, according to virtually all available evidence to date. The clinical importance of recognizing PIN is based on its strong association with prostatic carcinoma. PIN has a high predictive value as a marker for adenocarcinoma. Its identification in biopsy specimens of the prostate warrants further search for concurrent invasive carcinoma. PIN is associated with progressive abnormalities of phenotype and genotype intermediate between normal prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of prostatic carcinogenesis. There is progressive gain or loss of a wide variety of biomarkers, including morphometric markers, differentiation markers, stromal markers, growth factors and associated receptors, oncogenes, tumor suppressor genes, and chromosomes. Abnormalities in expression of most biomarkers are amplified in the progression from high-grade PIN to localized cancer, metastatic cancer, and hormone-refractory cancer. Oncogenesis of prostatic carcinoma probably occurs through the selection of several genetic changes, each modifying the expression or function of genes controlling cell growth and differentiation. Further studies are needed to evaluate the function and prognostic value of oncogene expression in the normal, preneoplastic, and neoplastic prostate.

Retinoblastoma gene mutations in primary human prostate cancer

Structural alterations in the entire coding regions (exons 1 to 27) of the retinoblastoma (RB) gene in primary human prostate cancers were investigated, using polymerase chain reaction and single strand conformational polymorphism analysis of RNA. Of 25 samples obtained from patients, four (16.4%) were found to have RB alterations. DNA sequencing of the PCR products revealed point mutations resulting in single amino-acid substitutions of exons 6 and 19 in two cases, and base deletions of exons 8 and 17 in two cases. Two of four cases with RB mutations were moderately differentiated localized tumors and other two with RB mutations were poorly differentiated tumors with metastases. Our results suggest that RB gene mutation is involved in progression steps of prostate carcinogenesis.