Expression of the RNA component of human telomerase (hTR) in prostate cancer, prostatic intraepithelial neoplasia, and normal prostate tissue

Telomere Maintenance Pathway Activity Analysis Enables Tissue- and Gene-Level Inferences

Telomere maintenance is one of the mechanisms ensuring indefinite divisions of cancer and stem cells. Good understanding of telomere maintenance mechanisms (TMM) is important for studying cancers and designing therapies. However, molecular factors triggering selective activation of either the telomerase dependent (TEL) or the alternative lengthening of telomeres (ALT) pathway are poorly understood. In addition, more accurate and easy-to-use methodologies are required for TMM phenotyping. In this study, we have performed literature based reconstruction of signaling pathways for the ALT and TEL TMMs. Gene expression data were used for computational assessment of TMM pathway activities and compared with experimental assays for TEL and ALT. Explicit consideration of pathway topology makes bioinformatics analysis more informative compared to computational methods based on simple summary measures of gene expression. Application to healthy human tissues showed high ALT and TEL pathway activities in testis, and identified genes and pathways that may trigger TMM activation. Our approach offers a novel option for systematic investigation of TMM activation patterns across cancers and healthy tissues for dissecting pathway-based molecular markers with diagnostic impact.

Telomerase RNA Expression and DNA Ploidy as Prognostic Markers of Prostate Carcinomas

Aims and Background

The objective of this study was to determine whether there was a correlation between telomerase RNA expression and DNA ploidy status with clinicopathological parameters and biochemical recurrence after radical prostatectomy.

Study Design

Telomerase RNA expression and DNA ploidy were evaluated in imprint smear samples obtained from 112 prostates after radical prostatectomy. The results were correlated with pathological stage, Gleason score and serum PSA.

Results

Positive telomerse RNA expression was detected in 67.8% of prostate carcinomas. The multiple linear regression model showed a statistically significance increase in telomerase RNA expression with increased Gleason score ( P <0.0001) and preoperative serum PSA values ( P = 0.0125). DNA ploidy status also varied significantly with Gleason score ( P <0.0001) and preoperative serum PSA values ( P = 0.0110). Five patients with diploid tumors and negative telomerase RNA expression developed a recurrence. However, recurrence was associated with DNA aneuploidy ( P = 0.001) as well as with high telomerase RNA overexpression ( P = 0.001).

Conclusions

We conclude that telomerase RNA expression and DNA ploidy could be additional markers in the field of prognosis of prostate carcinomas.

MYC drives overexpression of telomerase RNA (hTR/TERC) in prostate cancer

Telomerase consists of at least two essential elements, an RNA component hTR or TERC that contains the template for telomere DNA addition and a catalytic reverse transcriptase (TERT). While expression of TERT has been considered the key rate-limiting component for telomerase activity, increasing evidence suggests an important role for the regulation of TERC in telomere maintenance and perhaps other functions in human cancer. By using three orthogonal methods including RNAseq, RT-qPCR, and an analytically validated chromogenic RNA in situ hybridization assay, we report consistent overexpression of TERC in prostate cancer. This overexpression occurs at the precursor stage (e.g. high-grade prostatic intraepithelial neoplasia or PIN) and persists throughout all stages of disease progression. Levels of TERC correlate with levels of MYC (a known driver of prostate cancer) in clinical samples and we also show the following: forced reductions of MYC result in decreased TERC levels in eight cancer cell lines (prostate, lung, breast, and colorectal); forced overexpression of MYC in PCa cell lines, and in the mouse prostate, results in increased TERC levels; human TERC promoter activity is decreased after MYC silencing; and MYC occupies the TERC locus as assessed by chromatin immunoprecipitation (ChIP). Finally, we show that knockdown of TERC by siRNA results in reduced proliferation of prostate cancer cell lines. These studies indicate that TERC is consistently overexpressed in all stages of prostatic adenocarcinoma and that its expression is regulated by MYC. These findings nominate TERC as a novel prostate cancer biomarker and therapeutic target. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Targeting strategies of adenovirus‑mediated gene therapy and virotherapy for prostate cancer (Review)

Prostate cancer (PCa) poses a high risk to older men and it is the second most common type of male malignant tumor in western developed countries. Additionally, there is a lack of effective therapies for PCa at advanced stages. Novel treatment strategies such as adenovirus-mediated gene therapy and virotherapy involve the expression of a specific therapeutic gene to induce death in cancer cells, however, wild-type adenoviruses are also able to infect normal human cells, which leads to undesirable toxicity. Various PCa-targeting strategies in adenovirus-mediated therapy have been developed to improve tumor-targeting effects and human safety. The present review summarizes the relevant knowledge regarding available adenoviruses and PCa-targeting strategies. In addition, future directions in this area are also discussed. In conclusion, although they remain in the early stages of basic research, adenovirus-mediated gene therapy and virotherapy are expected to become important therapies for tumors in the future due to their potential targeting strategies.

Widespread telomere instability in prostatic lesions

A critical function of the telomere is to disguise chromosome ends from cellular recognition as double strand breaks, thereby preventing aberrant chromosome fusion events. Such chromosome end-to-end fusions are known to initiate genomic instability via breakage-fusion-bridge cycles. Telomere dysfunction and other forms of genomic assault likely result in misregulation of genes involved in growth control, cell death, and senescence pathways, lowering the threshold to malignancy and likely drive disease progression. Shortened telomeres and anaphase bridges have been reported in a wide variety of early precursor and malignant cancer lesions including those of the prostate. These findings are being extended using methods for the analysis of telomere fusions (decisive genetic markers for telomere dysfunction) specifically within human tissue DNA. Here we report that benign prostatic hyperplasia (BPH), high-grade prostatic intraepithelial neoplasia (PIN), and prostate cancer (PCa) prostate lesions all contain similarly high frequencies of telomere fusions and anaphase bridges. Tumor-adjacent, histologically normal prostate tissue generally did not contain telomere fusions or anaphase bridges as compared to matched PCa tissues. However, we found relatively high levels of telomerase activity in this histologically normal tumor-adjacent tissue that was reduced but closely correlated with telomerase levels in corresponding PCa samples. Thus, we present evidence of high levels of telomere dysfunction in BPH, an established early precursor (PIN) and prostate cancer lesions but not generally in tumor adjacent normal tissue. Our results suggest that telomere dysfunction may be a common gateway event leading to genomic instability in prostate tumorigenesis. .

The risk of second cancers after diagnosis of primary thyroid cancer is elevated in thyroid microcarcinomas

BACKGROUND

Thyroid cancers have increased dramatically over the past few decades. Comorbidities may be important, and previous studies have indicated elevated second cancer risk after initial primary thyroid cancers. This study examined the risk of second cancers after development of a thyroid cancer, primary utilizing the Surveillance, Epidemiology, and End Results (SEER) program database.

METHODS

The cohort consisted of men and women diagnosed with first primary thyroid cancer who were reported to a SEER database in 1973-2008 (n=52,103). Standardized incidence ratios (SIR) were calculated for all secondary cancers. Confidence intervals and p-values are at 0.05 significance alpha level and are two-sided based on Poisson exact methods.

RESULTS

In this cohort, 4457 individuals developed second cancers. The risk of developing second cancers after a primary thyroid cancer varied from 10% to 150% depending on different cancer types. Cancers in all sites, breast, skin, prostate, kidney, brain, salivary gland, second thyroid, lymphoma, myeloma, and leukemia were elevated. The magnitude of the risk varied by histology, tumor size, calendar year of first primary thyroid cancer diagnosis, and the treatment of the primary thyroid cancer. The risk of a second cancer was elevated in patients whose first primary thyroid carcinomas were small, or were diagnosed after 1994, or in whom some form of radiation treatment was administered.

CONCLUSIONS

This large population-based analysis of second cancers among thyroid cancer patients suggests that there was an increase of second cancers in all sites, and the most commonly elevated second cancers were the salivary gland and kidney. Additionally, the increase in second cancers in patients with recently diagnosed thyroid microcarcinomas (<10 mm) suggests that aggressive radiation treatment of the first primary thyroid cancer, the environment, and genetic susceptibility, may increase the risk of a second cancer.

A novel biomarker TERTmRNA is applicable for early detection of hepatoma

Backgrounds

We previously reported a highly sensitive method for serum human telomerase reverse transcriptase (hTERT) mRNA for hepatocellular carcinoma (HCC). α-fetoprotein (AFP) and des-γ-carboxy prothrombin (DCP) are good markers for HCC. In this study, we verified the significance of hTERTmRNA in a large scale multi-centered trial, collating quantified values with clinical course.

Methods

In 638 subjects including 303 patients with HCC, 89 with chronic hepatitis (CH), 45 with liver cirrhosis (LC) and 201 healthy individuals, we quantified serum hTERTmRNA using the real-time RT-PCR. We examined its sensitivity and specificity in HCC diagnosis, clinical significance, ROC curve analysis in comparison with other tumor markers, and its correlations with the clinical parameters using Pearson relative test and multivariate analyses. Furthermore, we performed a prospective and comparative study to observe the change of biomarkers, including hTERTmRNA in HCC patients receiving anti-cancer therapies.

Results

hTERTmRNA was demonstrated to be independently correlated with clinical parameters; tumor size and tumor differentiation (P < 0.001, each). The sensitivity/specificity of hTERTmRNA in HCC diagnosis showed 90.2%/85.4% for hTERT. hTERTmRNA proved to be superior to AFP, AFP-L3, and DCP in the diagnosis and underwent an indisputable change in response to therapy. The detection rate of small HCC by hTERTmRNA was superior to the other markers.

Conclusions

hTERTmRNA is superior to conventional tumor markers in the diagnosis and recurrence of HCC at an early stage.

Quantitative measurement of telomerase activity and localization of its catalytic subunit (hTERT) in chronic inflammation of capsule formation around various model implants and in sarcomas in a rat model

Telomerase is upregulated in some preneoplastic lesions and overexpressed in the majority of malignant tumors, but absent in most nonneoplastic somatic tissues. We analyzed telomerase activity using TRAP-assay in capsule tissues in a rat model with chronic inflammation and in tumor, and visualized the catalytic subunit of telomerase (hTERT) by immunhistochemistry. Significant elevated telomerase activity was found in tumor tissue compared with nonneoplastic tissue (p = 0.047). Cases with a strong inflammation in capsule tissue showed a specific telomerase activity. In these cases, there were no significant differences in telomerase activities compared with malignant tumor tissue. We demonstrate elevated telomerase activity and its diagnostic limits around model implants in a rat model, and visualize its expression not only in malignant tissue but also in inflammatory cells. So the quantitative measurement of telomerase activity should not be applied in general as a marker for malignancy in capsule tissue.

Increased copy number of the TERT and TERC telomerase subunit genes in cancer cells

Telomerase is a ribonucleoprotein enzyme complex that adds telomeric repeats to the ends of chromosomes. The core telomerase components are the telomerase reverse transcriptase (TERT) catalytic subunit, and the telomerase RNA (TR) template subunit. In most cancers, telomerase is expressed at levels that are substantially higher than in normal cells. A known consequence of telomerase up-regulation which is considered to play a critical role in oncogenesis is maintenance of telomere length, and thus evasion by cancer cells of the normal limits on proliferation that are associated with the steady decrease in telomere length that accompanies proliferation of normal cells. It has also been suggested that telomerase up-regulation confers other advantages on cancer cells independent of its enzymatic activity. The mechanisms responsible for up-regulation of telomerase in cancer are incompletely understood. Here we review evidence suggesting that this frequently results from increased copy number of the genes encoding telomerase components. The TERT gene is located at human chromosome band 5p15.33, and the telomerase RNA component (TERC) gene that encodes TR is at 3q26.3. Chromosomal gains and gene amplifications involving chromosome arms 5p and 3q are among the most frequent in human tumors. Increased TERT and TERC gene dosage has been detected frequently in a variety of human cancers, and clonal evolution of cells with increased TERT or TERC copy number has been observed, suggesting a growth advantage in cells with increased TERT or TERC gene dosage.

Telomeres and telomerase in prostatic intraepithelial neoplasia and prostate cancer biology

Telomeres are terminal, repeated deoxyribonucleic acid (DNA) sequences that stabilize and protect the ends of the chromosomes. Mounting evidence indicates that by initiating chromosomal instability, short dysfunctional telomeres may be involved in prostate carcinogenesis. Although the exact cause of the telomere shortening observed in prostate cancer remains a mystery, telomere loss is known to occur during cell division and oxidative DNA damage, 2 byproducts of chronic inflammation, which is a common histologic finding in the prostate. In addition to prostate cancer causation, telomeres may also play a role in disease progression, and there are indications that tumor telomere content may prove useful as a prognostic marker. Once established, prostate cancer cells almost invariably activate the telomeric DNA polymerase enzyme telomerase, the detection of which may prove useful for diagnostic purposes. Interestingly, telomerase activity is suppressed in prostate cancer cells after androgen withdrawal, raising the possibility that androgen ablative therapies may re-instigate telomere loss, and consequent genetic instability, in surviving cancer cells, thus contributing to the emergence of an androgen-independent, lethal phenotype. A more thorough understanding of telomere biology as it relates to prostate cancer should provide new opportunities for disease prevention, diagnosis, prognostication, and treatment.

Prostate cancer stem cells

Prostate cancer is the most frequently diagnosed cancer in men. Despite recent advances in the detection of early prostate cancer there is little effective therapy for patients with locally advanced and/or metastatic disease. The majority of patients with advanced disease respond initially to androgen ablation therapy. However, most go on to develop androgen-independent tumours that inevitably are fatal. A similar response is seen to chemotherapeutic and radiotherapy treatments. As a result, metastatic prostate cancer remains an incurable disease by current treatment strategies. Recent reports of cancer stem cells have prompted questions regarding the involvement of normal stem/progenitor cells in prostate tumour biology, their potential contribution to the tumour itself and whether they are the cause of tumour initiation and progression. Although still controversial, the cancer stem cell is likely to be the most crucial target in the treatment of prostate cancer, and a thorough understanding of its biology, particularly of how the cancer stem cell differs from the normal stem cell, might allow it to be targeted selectively and eliminated, thus improving therapeutic outcome.

Identification of a stem cell candidate in the normal human prostate gland

Stem cells of the human prostate gland have not yet been identified utilizing a structural biomarker. We have discovered a new prostatic epithelial cell phenotype-expressing cytokeratin 6a (Ck6a+ cells). The Ck6a+ cells are present within a specialized niche in the basal cell compartment in fetal, juvenile and adult prostate tissue, and within the stem cell-enriched urogenital sinus. In adult normal prostate tissue, the average abundance of Ck6a+ cells was 4.9%. With proliferative stimuli in the prostate organ culture model, in which the epithelial-stromal interaction was maintained, a remarkable increase of Ck6a expression was noticed to up to 64.9%. The difference in cytokeratin 6a expression between the normal adult prostate and the prostate organ culture model was statistically significant (p<0.0001). Within the prostate organ culture model the increase of cytokeratin 6a-expressing cells significantly correlated with increased proliferation index (r = 0.7616, p = 0.0467). The Ck6a+ cells were capable of differentiation as indicated by their expression of luminal cell markers such as ZO-1 and prostate specific antigen (PSA). Our data indicate that Ck6a+ cells represent a prostatic epithelial stem cell candidate possessing high potential for proliferation and differentiation. Since the development of benign prostatic hyperplasia and prostate carcinogenesis are disorders of proliferation and differentiation, the Ck6a+ cells may represent a major element in the development of these diseases.

Serum human telomerase reverse transcriptase messenger RNA as a novel tumor marker for hepatocellular carcinoma

PURPOSE

We previously reported the usefulness of a qualified highly sensitive detection method for human telomerase reverse transcriptase (hTERT) mRNA in serum with 89.7% sensitivity for hepatocellular carcinoma (HCC). In this study, we developed a quantitative detection method for serum hTERT mRNA and examined the clinical significance in HCC diagnosis. EXPERIMENTAL BACKGROUND: In 64 patients with HCC, 20 with liver cirrhosis, 20 with chronic hepatitis, and 50 healthy individuals, we measured serum hTERT mRNA by using the newly developed real-time quantitative reverse transcription-PCR with SYBR Green I. We examined its sensitivity and specificity in HCC diagnosis, clinical significance in comparison with other tumor markers, and its correlations with the clinical variables by using multivariate analyses.

RESULTS

Serum hTERT mRNA showed higher values in patients with HCC than those with chronic liver diseases. hTERT mRNA expression was shown to be independently correlated with clinical variables such as tumor size, number, and degree of differentiation (P < 0.001, each). The sensitivity/specificity of hTERT mRNA and alpha-fetoprotein (AFP) mRNA in HCC diagnosis were 88.2%/70.0% for hTERT and 71.6%/67.5% for AFP, respectively. hTERT mRNA proved to be superior to AFP mRNA, AFP, and des-gamma-carboxy prothrombin in HCC diagnosis. Furthermore, hTERT mRNA in serum was associated with that in HCC tissue.

CONCLUSIONS

The usefulness of hTERT mRNA expression in HCC diagnosis and its superiority to conventional tumor markers were shown. Therefore, serum hTERT mRNA is a novel and available marker for HCC diagnosis.

Detection of Prostate Cancer and Predicting Progression

Carcinoma of the prostate is the second leading cause of male cancer-related death in the United States. Better indicators of prostate cancer presence and progression are needed to avoid unnecessary treatment, predict disease course, and develop more effective therapy. Numerous molecular markers have been described in human serum, urine, seminal fluid, and histological specimens that exhibit varying capacities to detect prostate cancer and predict disease course. However, to date, few of these markers have been adequately validated for clinical use. The purpose of this review is to examine the current status of these markers in prostate cancer and to assess the diagnostic potential for future markers from identified genes and molecules that display loss, mutation, or alteration in expression between tumor and normal prostate tissues. In this review we cite 91 molecular markers that display some level of correlation with prostate cancer presence, disease progression, cancer recurrence, prediction of response to therapy, and/or disease-free survival. We suggest criteria to consider when selecting a marker for further development as a clinical tool and discuss five examples of markers (chromogranin A, glutathione S-transferase pi 1, prostate stem cell antigen, prostate-specific membrane antigen, and telomerase reverse transcriptase) that fulfill some of these criteria. Finally, we discuss how to conduct evaluations of candidate prostate cancer markers and some of the issues involved in the validation process.

Androgen ablation therapy for prostate carcinoma suppresses the immunoreactive telomerase subunit hTERT

BACKGROUND

Telomerase is a ribonucleoprotein complex that protects the ends of chromosomes from degradation. Its catalytic subunit, hTERT, controls its activity. Prior data in prostate carcinoma cases indicated that immunohistochemical hTERT reactivity increases with tumor grade and may be absent in lower grade cases. The effect of complete androgen ablation (CAA) on tumor hTERT expression was uncertain.

METHODS

hTERT immunostaining was performed on the cancerous pretreatment biopsy tissue of 30 men who consecutively underwent CAA with bicalutamide and goserelin acetate for 30 days prior to undergoing radical prostatectomy, and on their tumor tissue from radical prostatectomy. As controls, biopsy and prostatectomy samples from 30 untreated men were studied. Nuclear staining was evaluated by two observers, and the change in staining between biopsy and prostatectomy samples was evaluated using the Student t test in both groups.

RESULTS

The percent of reactive tumor nuclei in treated men declined from 36.7% to 13.2% (P = 0.0001), and declined from 19.8% to 16.1% in untreated men (P = 0.4). The greater mean hTERT reactivity in the treated men's biopsy specimens was attributed to an increased proportion of higher (Gleason score > or = 7) grade tumors. The decline in hTERT immunostaining remained significant after normalizing it to that of the untreated group (P = 0.002). The original Gleason scores, corresponding declines in the percentage of reactive tumor nuclei, and significance were: Gleason score < or = 6: 11% (P = 0.03); Gleason score of 7: 23% (P < 0.006); and Gleason score > or = 8: 46% (P < 0.005) (from a mean 63% to 17%).

CONCLUSIONS

CAA for prostate carcinoma can be considered an antitelomerase therapy. The steepest reduction in telomerase activity was noted in the highest grade tumors.

Expression-patterns of the RNA component (hTR)and the catalytic subunit (hTERT) of human telomerase in nonneoplastic prostate tissue, prostatic intraepithelial neoplasia, and prostate cancer

BACKGROUND

Telomerase, a ribonucleoprotein, is composed of a RNA component (hTR) and two protein subunits. One of these subunits, the catalytic subunit (human telomerase reverse transcriptase, hTERT), represents a reverse transcriptase. hTERT-expression is closely correlated with telomerase activity. The telomerase is thought to be involved in immortalization process. By adding hexamic repeats to the end of chromosomal DNA, the telomeres, the enzyme is able to stop progresssive telomeric DNA loss that occurs during cell division due to the end replication problem that stops the mitotic clock.

METHODS

Expression-patterns of hTR using radioactive in situ hybridization with (35)S-labelled RNA probes were compared with immunhistochemical staining for hTERT in 14 cases of archival paraffin-embedded samples of normal prostatic tissue, high-grade prostatic intraepithelial neoplasia (PIN), prostatic cancer, and one atypical adenomatous hyperplasia (AAH). Beside the expression-patterns each telomerase component was evaluated semiquantitatively.

RESULTS

hTERT and hTR can be found in nonneoplstic tissue and are upregulated in premalignant transformated lesions. AAH showed no hTERT-expression and low hTR-expression. There is a heterogenous expression within prostatic carcinomas.

CONCLUSIONS

No association was observed between the grade of the tumour differentiation and semiquantitative levels of hTR- or hTERT-expression. Telomerase is of limited value for the diagnostic of malignant or benign lesions in prostate.

Telomerase reverse transcriptase subunit immunoreactivity: a marker for high-grade prostate carcinoma

BACKGROUND

Telomerase, a ribonucleoprotein complex that maintains telomeric DNA, has been detected in 67-93% of prostate carcinomas by telomeric repeat-amplification protocol assay (involving polymerase chain reaction). One study used in situ hybridization in nine patients; however, to date, no immunohistochemical results have been published.

METHODS

From two hospitals, the authors compiled data on 62 patients who underwent prostatectomy from January 1996 to May 2001. Representative tissue sections were immunostained with a polyclonal antibody to telomerase reverse transcriptase (TERT), the catalytic subunit of telomerase. Staining was evaluated by two observers and was correlated with grade, stage, and biochemical failure. There were 28 sections from low-grade to intermediate-grade tumors (Gleason score, 3-6), 14 sections with a Gleason score of 3 + 4 = 7, 9 sections with a Gleason score of 4 + 3 = 7, and 11 sections from high-grade tumors (Gleason score, 8-10).

RESULTS

From low-grade to high-grade tumors, the four groups described above disclosed nuclear reactivity in 64%, 100%, 100%, and 100% of sections, respectively. Mean percentages of 5%, 15%, 40%, and 51% of nuclei were reactive in the respective groups (P < 0.0001) with intratumoral heterogeneity. The percent of reactive tumor nuclei was not correlated with pathologic stage (P = 0.32) or margin status (P = 0.35). The basal cell layer in sections of high-grade prostatic intraepithelial neoplasia (HGPIN) and benign/atrophic acini was reactive; secretory cells were reactive in 13 of 34 HGPIN foci (38%) in 1-20% of nuclei and were never reactive in benign acini. Lymphocytes and skeletal muscle were reactive. Weak, nonspecific, cytoplasmic staining was noted in benign and tumor acini.

CONCLUSIONS

Like cytokeratin 34betaE12, nuclear anti-TERT reactivity is a basal cell marker in nonneoplastic prostatic acini. Anti-TERT reactivity is acquired by secretory cells in tumorigenesis, but consistent reactivity is restricted to high-grade carcinoma (Gleason primary pattern >or=4). This histologic evidence suggests that higher grade tumors have maximally activated telomerase and may be most responsive to antitelomerase therapy.

Telomerase as a prognostic marker in breast cancer: high-throughput tissue microarray analysis of hTERT and hTR

Telomerase activity (TA) has been shown to correlate with poor clinical outcome in various tumour entities, indicating that tumours expressing this enzyme may be more aggressive and that TA may be a useful prognostic marker. For breast cancer, however, TA is a controversial prognostic marker; whereas some studies suggest an association between TA and disease outcome, others do not find this association. This study used tissue microarrays (breast carcinoma prognosis arrays) containing 611 samples (each 0.6 mm in diameter) from the tumour centre of paraffin-embedded breast carcinomas to analyse the catalytic subunit of telomerase, human telomerase reverse-transcriptase (hTERT), and the internal RNA component (hTR), which are the core components of the telomerase holoenzyme complex. hTERT protein expression was obtained by immunohistochemistry (human anti-telomerase antibody Ab-2, Calbiochem), and hTR RNA was measured by radioactive in situ hybridization. hTERT and hTR expression were determined semi-quantitatively and graded (scores 1-4). Clinical data, such as histological subtype, pT stage, tumour diameter, pN stage, BRE grade, tumour-specific survival (in months), patient's age and others, were available for statistical analysis. A statistically significant correlation was found between tumour-specific survival (overall survival) and hTERT expression (p < 0.0001) or hTR expression (p = 0.00110). Tumours with higher scores (scores 3, 4) for hTR and/or hTERT were associated with a worse prognosis. In multivariate analysis, hTERT expression was an independent prognostic factor. Previous studies, focusing on analysis of TA in smaller numbers of fresh-frozen breast carcinomas by the TRAP assay, gave controversial results with respect to TA as a prognostic marker. Using tissue microarrays from 611 breast carcinomas, this study has demonstrated that increased expression levels of the telomerase core components, hTERT and hTR, are associated with lower overall survival. These findings suggest that TA should be included in future validation studies as a prognostic marker in breast cancer.

Human prostate epithelial cell-type cDNA libraries and prostate expression patterns

BACKGROUND

Transcriptome analysis is a powerful approach to uncovering genes responsible for diseases such as prostate cancer. Ideally, one would like to compare the transcriptomes of a cancer cell and its normal counterpart for differences.

METHODS

Prostate luminal and basal epithelial cell types were isolated and cell-type-specific cDNA libraries were constructed. Sequence analysis of cDNA clones generated 505 luminal cell genes and 560 basal cell genes. These sequences were deposited in a public database for expression analysis.

RESULTS

From these sequences, 119 unique luminal expressed sequence tags (ESTs) were extracted and assembled into a luminal-cell transcriptome set, while 154 basal ESTs were extracted and assembled into a basal-cell set. Interlibrary comparison was performed to determine representation of these sequences in cDNA libraries constructed from prostate tumors, PIN, cell lines.

CONCLUSIONS

Our analysis showed that a significant number of epithelial cell genes were not represented in the various transcriptomes of prostate tissues, suggesting that they might be underrepresented in libraries generated from tissue containing multiple cell types. Although both luminal and basal cell types are epithelial, their transcriptomes are more divergent from each other than expected, underscoring their functional difference (secretory vs. nonsecretory). Tumor tissues show different expression of luminal and basal genes, with perhaps a trend towards expression of basal genes in advanced diseases.

Expression of telomerase subunits in normal and neoplastic prostate epithelial cells isolated by laser capture microdissection

BACKGROUND

Vertebrates have special structures at the ends of their chromosomes, known as telomeres, which may provide the chromosomes with stability and protect them from exonucleolytic degradation. The shortening of telomeric DNA with each cell division may lead to cell cycle arrest and/or apoptosis of a normal human somatic cell. Telomerase, an RNA-dependent DNA polymerase, elongates the 3'-ends of telomeric DNA. Thus, the presence of telomerase activity may reflect a cell's potential immortal state. The telomerase complex is comprised of several subunits. In the current study, the authors describe the use of laser capture microdissection (LCM) to procure pure matched tumor and normal cell populations from histologic sections and to determine the expression of telomerase subunits in these purified samples.

METHODS

Pure matched tumor and normal prostate epithelial cells were procured by LCM using fresh frozen tissue samples obtained from patients undergoing radical prostatectomy. RNA was extracted from LCM captured cells, and the subunits for telomerase were assayed by reverse transcriptase-polymerase chain reaction.

RESULTS

In 18 samples that were captured with LCM, only the catalytic subunit of telomerase, or hTERT, was found to be discriminatory between tumor cells (17 of 18 specimens, 94.4%) and nontumor cells (none of 18 specimens). TP1, a protein that has been shown to be associated with telomerase activity, was expressed in 3 of 18 normal cells (16.7%) and 15 of 18 tumor cells (83.3%). The RNA subunit of telomerase, or hTR, was expressed in 10 of 18 normal cells (55.6%) and 18 of 18 tumor cells (100%). There was no apparent correlation between telomerase subunit(s) expression and Gleason sum score.

CONCLUSIONS

Molecular analyses of LCM cells from prostate carcinoma patient samples demonstrated transcriptional up-regulation of all telomerase subunits in the prostatic epithelium. However, only the catalytic subunit of telomerase, hTERT, was found to be discriminatory between neoplastic versus normal cells (94.4% vs. 0%). This finding suggests that the hTERT subunit may be a useful marker for the detection of prostate carcinoma and/or a potential target for therapy.

Telomerase in endocrine and endocrine-dependent tumors

Telomerase, the ribonucleoprotein enzyme that elongates chromosomal ends, or telomeres, is repressed in most normal somatic cells but reactivated in transformed cells to compensate for the progressive erosion of the telomeres during cell divisions. In accordance with this hypothesis, the presence of telomerase activity has been reported in more than 90% of human cancers, whereas most normal tissues or benign tumors contain low or undetectable telomerase activity. Reactivation of telomerase has also been widely reported in endocrine neoplasms and in hormone-related cancers. In the present study, we review the most recent publications on telomerase in these types of tumors. The hormonal regulation of telomerase activity and the possible strategies for cancer therapy based on the inhibition of telomerase has also been discussed.

Histological markers of risk and the role of high-grade prostatic intraepithelial neoplasia

The marked discrepancy between the prevalence of preclinical prostate cancer and the incidence of clinically manifest disease indicates a long latency phase and significant heterogeneity in the progression potential of early neoplastic lesions. There are a variety of histologic changes within prostatic epithelium that have been termed atypical or dysplastic. The 2 most widely studied of these lesions are prostatic intraepithelial neoplasia (PIN) and atypical adenomatous hyperplasia (AAH). Although associations between AAH and adenocarcinoma are spurious, those linking high-grade PIN (HGPIN) to cancer are far more established. There is a significantly increased risk for patients with isolated HGPIN to have prostate cancer confirmed on subsequent biopsy, suggesting that HGPIN is a marker for prostate carcinoma in addition to its potential role as a premalignant lesion. Autopsy studies reveal that HGPIN is found in association with cancer in 63% to 94% of malignant and 25% to 43% of benign prostates. Data on age and race reveal that African American men develop more extensive HGPIN at a younger age than white men. A wide spectrum of molecular/genetic abnormalities appears to be common to both HGPIN and prostate cancer. Data loss of 8p, 10q, 16q, 18q, and gain of 7q31, 8q, multiple copies of the c-myc genes, along with changes in chromatin texture, telomerase activity, cell cycle status, and proliferative indices collectively suggest that HGPIN is intermediate between benign epithelium and prostatic carcinoma with respect to these markers. These data indicate that HGPIN is important in neoplastic progression, and may present an appropriate target/marker for chemoprevention.

Telomerase activity modulation in the prevention of prostate cancer

Telomerase is a ribonucleoprotein that stabilizes chromosomes by maintaining their telomeric ends. Although telomerase is normally expressed in reproductive tissues, it is virtually absent in most normal somatic tissues. During carcinogenesis, cells activate telomerase to protect chromosomal ends from the telomere erosion that occurs with replication. Prevention of telomere loss by activation of telomerase allows for the cellular immortalization that is a characteristic of cancer cells. Recent studies have shown that genetic instability arising from critical telomere shortening is a mechanism through which cancer cells attain multiple genetic aberrations that characterize a malignant clone. Thus, the timing of telomerase activation during carcinogenesis is likely to play an important role in modulating the genetic instability that determines the malignant phenotype. Earlier activation of telomerase should minimize genetic aberrations in neoplastic cells and lead to less aggressive tumors, or may prevent carcinogenesis. In this article, we discuss recent data on telomerase expression in prostate cancer, propose a model that relates the dynamics of telomerase activation to the evolution of different prostatic malignancies, and discuss the potential application of telomerase activation as a strategy for the prevention of prostate cancer.

Cellular and molecular pathology of prostate cancer precursors

Prostate cancer is usually heterogeneous and multifocal, with diverse clinical and morphologic manifestations. Current understanding of the molecular basis for this heterogeneity is limited, particularly for prostatic intraepithelial neoplasia (PIN), the only putative precursor which can be identified according to morphologic criteria. However, it is likely that prostatic adenocarcinoma might arise from precursor lesions other than PIN, although these cannot be recognized with certainty at the present time. In this review, we summarize the current state of knowledge regarding the cell-biological and genetic bases for linking PIN and prostatic adenocarcinoma. It is conceivable that a stem cell of basal phenotype, or an amplifying cell, is the target of prostatic carcinogenesis. Prominent genetic heterogeneity is characteristic of both PIN and carcinoma; and multiple foci of PIN arise independently within the same prostate. This observation suggests that a field effect probably underlies prostatic neoplasia. Multiple foci of cancer also often arise independently, lending additional support to this hypothesis. The strong genetic similarities between PIN and cancer strongly suggest that evolution and clonal expansion of PIN, or other precursor lesions, may account for the multifocal etiology of carcinoma. Uncertainties with respect to identification of those precursor lesions which are most likely to progress to invasive and metastatic prostate cancer reinforce the requirement for objective immunohistochemical or molecular biological markers of the aggressive phenotype.

Expression of telomerase genes correlates with telomerase activity in human colorectal carcinogenesis

The human telomerase enzyme is composed of two essential components, hTR, which acts as a template for reverse transcription, and hTERT, which is the putative catalytic subunit for the enzyme. Recent studies have demonstrated a good correlation between hTERT expression and telomerase activation, whereas RT-PCR results seemed to reveal that hTR is ubiquitously expressed in all cells. These observations left unclear the role of hTR, and to a lesser extent hTERT, in the regulation of telomerase activation. In the present study, the correlation of telomerase activity and the expression of these genes was examined in a total of 70 colorectal tissues (25 adenocarcinomas, 30 adenomas, and 15 samples of normal colorectal mucosa). Total RNA for RT-PCR analysis and cell extracts for TRAP assay were obtained from consecutive sections and histological control was simultaneously performed. To avoid false-positive results, due to the fact that hTR cDNA and genomic hTR DNA are identical (the gene has no introns), extensive DNase digestion was performed before cDNA synthesis. RT-PCR analysis revealed that hTERT mRNA was expressed in all cancers and in 13 of 14 telomerase-positive adenomas, but never in telomerase-negative colorectal tissues. hTR transcripts were observed in all telomerase-positive samples but also in three telomerase-negative samples, two adenomas, and one normal colonic mucosa. It is concluded that hTERT and hTR expression is strongly correlated with telomerase activity. hTR transcripts, however, also occur in some telomerase-negative tissues and these results are in keeping with the concept that hTERT expression is a major regulator of telomerase activity.

Overexpression of human telomerase RNA in Helicobacter pylori-infected human gastric mucosa

Telomerase, an enzyme associated with cellular immortality and malignancy, plays an important role in cellular immortalization and tumorigenesis. Furthermore, overexpression of the RNA component of the telomerase, called human telomerase RNA (hTR), has been demonstrated in various human cancers as an early event. The pattern of hTR expression following Helicobacter pylori (H. pylori) infection in human gastric mucosa was investigated by a radioactive in situ hybridization (ISH) assay. Paraffin-embedded sections of 50 biopsy specimens taken from the gastric antrum of individual patients infected to different extents with H. pylori, as well as normal gastric mucosa, were studied. In normal gastric mucosa, only weak hTR expression was noted and the expression was limited to basal cells of the gastric glands. However, the degree of hTR expression gradually increased in parallel with the degree of H. pylori infection. The mean scores of gastric mucosa with mild, moderate and severe degrees of H. pylori infection were 2.3, 2.8, and 3.7 times higher than that of normal gastric mucosa, respectively. The results of this study suggested that up-regulation of hTR expression is a frequent and early event associated with H. pylori infection in the gastric mucosa and may play some role in gastric carcinogenesis. Sufficient synthesis of hTR during this early stage may be a prerequisite for telomerase reactivation to occur in gastric cancer.