High telomerase activity is associated with cell cycle deregulation and rapid progression in endometrioid adenocarcinoma of the uterus

Review of Mendelian Randomization Studies on Endometrial Cancer

Endometrial cancer (EC) is a common gynecological cancer. In some parts of the world, the incidence and mortality of EC are on the rise. Understanding the risk factors of EC is necessary to prevent the occurrence of this disease. Observational studies have revealed the association between certain modifiable environmental risk factors and EC risk. However, due to unmeasured confounding, measurement errors, and reverse causality, observational studies sometimes have limited ability to judge robust causal inferences. In recent years, Mendelian randomization (MR) analysis has received extensive attention, providing valuable insights for cancer-related research, and is expected to identify potential therapeutic interventions. In MR analysis, genetic variation (alleles are randomly assigned during meiosis and are usually independent of environmental or lifestyle factors) is used instead of modifiable exposure to study the relationship between risk factors and disease. Therefore, MR analysis can make causal inference about exposure and disease risk. This review briefly describes the key principles and assumptions of MR analysis; summarizes published MR studies on EC; focuses on the correlation between different risk factors and EC risks; and discusses the application of MR methods in EC research. The results of MR studies on EC showed that type 2 diabetes, uterine fibroids, higher body mass index, higher plasminogen activator inhibitor-1 (PAI-1), higher fasting insulin, early insulin secretion, longer telomere length, higher testosterone and higher plasma cortisol levels are associated with increased risk of EC. In contrast, later age of menarche, higher circulatory tumor necrosis factor, higher low-density lipoprotein cholesterol, and higher sex hormone-binding globulin levels are associated with reduced risk of EC. In general, despite some limitations, MR analysis still provides an effective way to explore the causal relationship between different risk factors and EC.

Telomerase and Telomeres in Endometrial Cancer

Telomeres at the termini of human chromosomes are shortened with each round of cell division due to the “end replication problem” as well as oxidative stress. During carcinogenesis, cells acquire or retain mechanisms to maintain telomeres to avoid initiation of cellular senescence or apoptosis and halting cell division by critically short telomeres. The unique reverse transcriptase enzyme complex, telomerase, catalyzes the maintenance of telomeres but most human somatic cells do not have sufficient telomerase activity to prevent telomere shortening. Tissues with high and prolonged replicative potential demonstrate adequate cellular telomerase activity to prevent telomere erosion, and high telomerase activity appears to be a critical feature of most (80–90%) epithelial cancers, including endometrial cancer. Endometrial cancers regress in response to progesterone which is frequently used to treat advanced endometrial cancer. Endometrial telomerase is inhibited by progestogens and deciphering telomere and telomerase biology in endometrial cancer is therefore important, as targeting telomerase (a downstream target of progestogens) in endometrial cancer may provide novel and more effective therapeutic avenues. This review aims to examine the available evidence for the role and importance of telomere and telomerase biology in endometrial cancer.

Telomerase Inhibitors from Natural Products and Their Anticancer Potential

Telomeres and telomerase are nowadays exploring traits on targets for anticancer therapy. Telomerase is a unique reverse transcriptase enzyme, considered as a primary factor in almost all cancer cells, which is mainly responsible to regulate the telomere length. Hence, telomerase ensures the indefinite cell proliferation during malignancy—a hallmark of cancer—and this distinctive feature has provided telomerase as the preferred target for drug development in cancer therapy. Deactivation of telomerase and telomere destabilization by natural products provides an opening to succeed new targets for cancer therapy. This review aims to provide a fundamental knowledge for research on telomere, working regulation of telomerase and its various binding proteins to inhibit the telomere/telomerase complex. In addition, the review summarizes the inhibitors of the enzyme catalytic subunit and RNA component, natural products that target telomeres, and suppression of transcriptional and post-transcriptional levels. This extensive understanding of telomerase biology will provide indispensable information for enhancing the efficiency of rational anti-cancer drug design.

Knockdown of hTERT and Treatment with BIBR1532 Inhibit Cell Proliferation and Invasion in Endometrial Cancer Cells

Telomerase activity and expression of the catalytic protein hTERT are associated with cell proliferation and advanced stage in endometrial cancer. Our objective was to evaluate the effect of inhibition of hTERT by siRNA and BIBR1532 on cell growth, apoptosis and invasion in endometrial cancer cells. Knockdown of hTERT or treatment of the cells with BIBR1532 decreased telomerase activity, inhibited cell proliferation, induced apoptosis, and reduced cell invasion in Ishikawa and ECC-1 cells. Either hTERT siRNA or BIBR1532 in combination with paclitaxel promoted a synergistic inhibitory effect on cell growth through induction of Annexin V expression and a remarkable reduction in cell invasion through reduction of protein expression of MMP9, MMP2, and MMP3. Increased telomerase activity and hTERT protein expression by transfections enhanced the protein expression of MMPs and increased the cell invasion ability. BIBR1532 significantly antagonized cell invasion induced by increased hTERT expression. These findings suggest that telomerase and hTERT facilitate cell invasion via MMP family in human endometrial cancer cells.

Expression of human telomerase reverse transcriptase in vulvar intraepithelial neoplasia and squamous cell carcinoma: an immunohistochemical study with survivin and p53

CONTEXT

Human telomerase reverse transcriptase (hTERT), an enzyme that enables cells to overcome replicative senescence and to divide indefinitely, is overexpressed in many cancers and their precursor lesions.

OBJECTIVE

To test whether hTERT expression is related to neoplastic progression and resistance to apoptosis in vulvar epithelia.

DESIGN

Immunoexpression of hTERT was evaluated in 101 formalin-fixed, paraffin-embedded archival vulvar epithelia consisting of normal squamous vulvar epithelia (n  =  25), lichen sclerosus (n  =  10), high-grade classic vulvar intraepithelial neoplasia (n  =  16), differentiated vulvar intraepithelial neoplasia (n  =  18), and vulvar invasive keratinizing squamous cell carcinoma (n  =  32) and related to survivin and p53 expression. Immunostaining for all factors was scored for moderate and strong intensities with regard to quantity to determine upregulation and overexpression (score 0, 0% immunoreactive cells; score 1+, <5% immunoreactive cells; score 2+, 5% to 50% immunoreactive cells; score 3+, >50% immunoreactive cells). Score 3+ was considered as overexpression.

RESULTS

Nuclear hTERT immunoexpression was closely related to survivin reactivity, increased from normal vulvar squamous epithelia to lichen sclerosus and to high-grade classic vulvar intraepithelial neoplasia, differentiated vulvar intraepithelial neoplasia, and invasive keratinizing squamous cell carcinoma (P < .001), and followed the morphologic distribution of atypical squamous epithelial cells. Overexpression of hTERT was comparable to that seen for p53 in invasive keratinizing squamous cell carcinoma (P  =  .62); significant differences were calculated for differentiated vulvar intraepithelial neoplasia (P  =  .003) and high-grade classic vulvar intraepithelial neoplasia (P  =  .001).

CONCLUSION

Human telomerase reverse transcriptase is upregulated in vulvar intraepithelial neoplasia and invasive keratinizing squamous cell carcinoma compared with nonneoplastic squamous epithelia of the vulva as an apparently early and preinvasive event in the neoplastic transformation, with development of cellular longevity and resistance to apoptosis by survivin activation as associated features, independent of the etiology of vulvar intraepithelial neoplasia.

Telomerase detection in the diagnosis and prognosis of cancer

Telomerase, a critical enzyme responsible 'for cellular immortality, is usually repressed in somatic cells except for lymphocytes and self-renewal cells, but is activated in approximately 85% of human cancer tissues. The human telomerase reverse transcriptase (hTERT) is the catalytic component of human telomerase. In cancers in which telomerase activation occurs at the early stages of the disease, telomerase activity and hTERT expression are useful markers for the detection of cancer cells. In other cancers in which telomerase becomes upregulated upon tumor progression, they are useful as prognostic indicators. However, careful attention should be paid to false-negative results caused by the instability of telomerase and of the hTERT mRNA and the presence of PCR inhibitors, as well as to false-positive results caused by the presence of alternatively spliced hTERT mRNA and normal cells with telomerase activity. Recently, methods for the in situ detection of the hTERT mRNA and protein have been developed. These methods should facilitate the unequivocal detection of cancer cells, even in tissues containing a background of normal telomerase-positive cells.

Telomere length and genetic analyses in population-based studies of endometrial cancer risk

BACKGROUND

Telomeres are protective structures at the ends of linear chromosomes, regulated by a host of associated proteins. When telomeres become dysfunctional, genomic instability ensues. The vast majority of cells undergo apoptosis, although a rare cell may survive and become tumorigenic.

METHODS

The authors used conditional logistic regression to examine relative telomere length in peripheral blood leukocytes, genetic variants at telomere maintenance gene loci (TERT, TNKS2, POT1, TERF1, TERF2), and endometrial cancer risk in case-control studies nested within the Nurses' Health Study and the Women's Health Study.

RESULTS

Relative telomere length was significantly inversely correlated with body mass index and weight gain since age 18 years. The authors did not observe a relationship between relative telomere length and endometrial cancer risk. Women in the shortest quartile had a multivariate-adjusted odds ratio (OR) of 1.20 (95% confidence interval [95% CI], 0.73-1.96; P for trend = .37) compared with women in the longest quartile. The authors found an elevation in endometrial cancer risk among women carrying at least 1 minor allele of RS2736122 (TERT; OR, 1.18; 95% CI, 1.01-1.38) or RS12412538 (TNKS2; OR, 1.16; 95% CI, 1.00-1.34).

CONCLUSIONS

Relative telomere length was not associated with endometrial cancer risk. Other aspects of telomere maintenance remain to be explored.

Irradiation-induced telomerase activity and gastric cancer risk: a case-control analysis in a Chinese Han population

BACKGROUND

Telomerase expression is one of the characteristics of gastric cancer (GC) cells and telomerase activity is frequently up-regulated by a variety of mechanisms during GC development. Therefore, we hypothesized that elevated levels of activated telomerase might enhance GC risk due to increased propagation of cells with DNA damage, such as induced by gamma-radiation.

METHODS

To explore this hypothesis, 246 GC cases and 246 matched controls were recruited in our case-control study. TRAP-ELISA was used to assess the levels of telomerase activity at baseline and after gamma-radiation and the gamma-radiation-induced telomerase activity (defined as after gamma-irradiation/baseline) in cultured peripheral blood lymphocytes (PBLs).

RESULTS

Our data showed that there was no significant difference for the baseline telomerase activity between GC cases and controls (10.17 +/- 7.21 vs. 11.02 +/- 8.03, p = 0.168). However, after gamma-radiation treatment, gamma-radiation-induced telomerase activity was significantly higher in the cases than in the controls (1.51 +/- 0.93 vs. 1.22 +/- 0.66, p < 0.001). Using the median value of gamma-radiation-induced telomerase activity in the controls as a cutoff point, we observed that high gamma-radiation-induced telomerase activity was associated with a significantly increased GC risk (adjusted odds ratio, 2.45; 95% confidence interval, 1.83-3.18). Moreover, a dose response association was noted between gamma-radiation-induced telomerase activity and GC risk. Age, but not sex, smoking and drinking status seem to have a modulating effect on the gamma-radiation-induced telomerase activities in both cases and controls.

CONCLUSION

Overall, our findings for the first time suggest that the increased gamma-radiation-induced telomerase activity in PBLs might be associated with elevated GC risk. Further confirmation of this association using a prospective study design is warranted.

Radiation-induced effects on telomerase in gynecological cancer cell lines with different radiosensitivity and repair capacity

PURPOSE

Telomerase activation in response to irradiation might enhance the radioresistance of cells. Thus, we have investigated radiation-induced effects on telomerase in six gynecological cancer cell lines, with different intrinsic radiosensitivity and capacity for sublethal damage repair (SLDR).

MATERIALS AND METHODS

Three endometrial adenocarcinoma (UM-EC-1, UT-EC-2B and UT-EC-3) and three vulvar squamous cell carcinoma (A431, UM-SCV-2 and UM-SCV-7) cell lines were irradiated with doses of 5, 10 and 25 Gy and the effects on telomerase were evaluated at 0.5, 6, 24 and 48 h post-irradiation. Telomerase activity was quantitatively measured by SYBR Green real-time telomeric repeat amplification protocol.

RESULTS

The most radioresistant cell line A431 had the strongest stimulatory effects (approximately 2.0 - 2.5-fold) on telomerase activity 24 and 48 h post-irradiation with the highest radiation doses. In contrast to that, telomerase activities in the highly radiosensitive cell line UT-EC-2B remained below the basal level throughout the 48-h period of post-irradiation with the highest doses, and even a decline to approximately 50% of the basal level was found 24 h after exposure. In other cell lines being either moderately or highly radiation resistant, telomerase activity levels in response to irradiation remained mainly at the basal level or gradually increased.

CONCLUSIONS

The present findings indicate that there might be a connection between the radiation-induced telomerase response and radiosensitivity. However, no correlation was found between the radiation-induced effects on telomerase and the sublethal damage repair capacity of the cells.

Immunoexpression and prognostic role of hTERT and cyclin D1 in urothelial carcinoma

The aim was to investigate the expression of human telomerase reverse transcriptase (hTERT) and cyclin D1 in correlation with clinicopathologic features of urothelial carcinoma (UC). Tissue microarrays (TMA) were constructed from paraffin-embedded specimens of 94 UC patients and immunohistochemical staining was used. High hTERT expression was found in 50 (53%) of the 94 tumors and was significantly associated with tumor invasiveness and tumor grade (P=0.008 and 0.0190, respectively). High cyclin D1 expression was found in 69 (73%) of the 94 tumors and was significantly associated with non-invasiveness and smaller tumor size, but there was no correlation with tumor grade. Kaplan-Meier analysis indicated that patients with low hTERT and high cyclin D1 levels had longer local recurrence-free survival (P=0.0482 and 0.0123, respectively). In addition, patients with high cyclin D1 levels had longer disease-free survival (P=0.0195). In conclusion, this study demonstrated that hTERT and cyclin D1 may be of recurrence predictive value for UC, thus providing clinicians with ancillary information when deciding on suitable therapeutic strategies in UC.

Differential induction in telomerase activity among bladder cancer patients and controls on gamma-radiation

Expression of telomerase is one of the hallmarks of tumor cells and has been used as a diagnostic biomarker and a therapeutic target in cancer. Novel findings have shown that telomerase activation in normal human epithelial cells may affect expression of several cancer-related genes, such as growth-related genes and c-myc gene, suggesting a possible role of telomerase in tumor initiation. Therefore, we hypothesized that individuals who are sensitive to mutagen challenge in terms of induced telomerase activity might have increased cancer risk. We tested this hypothesis in a bladder cancer case-control study (51 cases and 51 matched controls) by measuring baseline and gamma-radiation-induced telomerase activities in peripheral blood lymphocytes. We found a significantly higher gamma-radiation-induced telomerase activity in bladder cancer cases compared with the controls (1.34 versus 1.23; P = 0.044). A similar finding was also observed using the normalized telomerase activity (ratio of gamma-radiation induced versus baseline; 1.49 versus 1.19; P < 0.001). In further categorizing the telomerase activity using 75% of the normalized value in the controls as a cutoff point, we found a significantly increased risk for bladder cancer associated with higher induced telomerase activity (adjusted odds ratio, 3.62; 95% confidence interval, 1.38-9.51). In quartile analysis, a dose-response association was noted between the induced telomerase activity and increased bladder cancer risk (P(trend) = 0.005). Our findings provide the first evidence linking the mutagen-induced telomerase activity in peripheral blood lymphocytes to the risk of bladder cancer, which warrants further investigation in large-sized studies and other cancer types.

Claudin 1 differentiates endometrioid and serous papillary endometrial adenocarcinoma

OBJECTIVE

The expression of claudins, the main tight junction proteins involved in cell adhesion and carcinogenesis, was studied in endometrioid (type I) and seropapillary (type II) endometrial adenocarcinoma. The characteristics and possible diagnostic potential of claudin expression pattern were investigated in the two cancer types having different prognosis.

METHODS

Protein and mRNA expression of claudins was evaluated in 17 endometrioid carcinomas and 15 seropapillary adenocarcinomas by immunohistochemistry and real-time PCR in comparison with 38 cases of hyperplasia, normal proliferative and secretory endometrium samples. Further, protein expressions used in diagnostics (estrogen and progesterone receptors, p53, PCNA and beta-catenin) were also studied.

RESULTS

In endometrioid carcinoma and hyperplasia low claudin 1 and high claudin 2 protein contents, whereas in seropapillary adenocarcinoma high claudin 1 and low claudin 2 levels were detected. Intense protein expression was noted for claudins 3, 4, 5, and 7, without significantly different patterns in carcinoma, hyperplasia, secretory, and proliferative endometrium. Real-time PCR results confirmed differences in claudin 1 but not claudin 2 mRNA expression, whereas some minor discrepancies were observed in comparison with immunohistochemistry patterns.

CONCLUSION

The two types of endometrial adenocarcinomas were well distinguished by claudins 1 and 2 by immunohistochemistry, claudins 3, 4, and 7, however, did not prove useful in distinguishing the two entities. The similar claudin pattern seen in hyperplasia and endometrioid carcinoma and the differences regarding seropapillary adenocarcinoma support the dualistic model of endometrial carcinogenesis. The claudin pattern of the two tumor types might reflect a different cellular or pathogenetic pathway as well as a different cell adhesion behavior explaining the invasive properties.

Immunohistochemical detection of human telomerase reverse transcriptase (hTERT) and c-kit in serous ovarian carcinoma: A clinicopathologic study

OBJECTIVE

This study investigated the expression of human telomerase reverse transcriptase (hTERT) and c-kit in a cohort of serous ovarian carcinomas by immunohistochemistry with regard to outcome and clinicopathologic variables.

METHODS

Formalin-fixed, paraffin-embedded archival tissue sections of 10 benign serous cystadenomas, 10 serous neoplasms of low malignant potential (LMP), and 41 serous ovarian carcinomas were immunostained with antibodies to hTERT and c-kit. Immunostaining was scored with regard to quantity and intensity of positively stained cells as negative or weak, moderate, and strong. Mitotic activity was determined as mitotic figures per 10 high power fields.

RESULTS

hTERT expression was negative in serous cystadenomas; 70% of LMP showed strong nuclear immunoreactivity. In serous carcinomas, nuclear and sometimes cytoplasmic immunoreactivity was observed; 14% of cases were scored as negative, 42% as moderate, and 44% as strong. hTERT immunoreactivity increased with grade (P < 0.0192) and mitotic activity (P = 0.0018), but not with FIGO stage (P = 0.2752), and was related with outcome (P = 0.0477). No c-kit immunoreactivity was observed in serous cystadenomas and LMP; 27% of serous carcinomas were negative, 46% showed moderate, and 27% strong immunostaining. c-kit immunoreactivity was positively correlated with grade (P = 0.0008) and FIGO stage (P = 0.0247), but not with mitotic activity (P = 0.1433) and outcome (P = 0.1145); however, c-kit expression was positively related with poor outcome in FIGO II and III stages (P = 0.0105).

CONCLUSIONS

hTERT and c-kit are frequently up-regulated in serous ovarian carcinomas; c-kit immunoexpression may serve as a marker of aggressive behavior in high stage tumors.

Telomerase activity is correlated with lower grade and lower stage bladder carcinomas

BACKGROUND

Telomerase is a ribonucleoprotein enzyme that compensates for the progressive erosion of telomeres. The increasing interest in telomerase is motivated by the demonstration that most human carcinomas are telomerase positive. The potential use of telomerase activity in bladder carcinomas using a urine sample has been reported in several studies. However, little is known about the detection of telomerase activity in bladder carcinoma tissues. Herein, we investigate telomerase activity in bladder carcinoma tissues according to grade (G) and stage.

MATERIAL AND METHODS

Telomerase activity was assayed by polymerase chain reaction enzyme-linked immunosorbent assay methods. Malignant lesions were assessed in 37 patients with bladder carcinoma and no malignant lesions were assessed in five patients with dysplasia or inflammatory bladder lesions.

RESULTS

Twenty-three out of 37 carcinoma samples were telomerase-positive and one out of five control samples without carcinoma was telomerase-positive. The positive rates according to stage and grade were 83.3% for superficial and 42.1% for invasive stages and 83.3% for G1, 66.7% for G2 and 40.0% for G3. Telomerase activity was correlated with lower grade and lower stage bladder carcinomas.

CONCLUSION

These results strongly suggest that reactivation of telomerase may differ between superficial and invasive bladder carcinomas and also between low grade and high grade bladder carcinomas.

Immunohistochemical Detection of Human Telomerase Reverse Transcriptase (hTERT), Topoisomerase II?? Expression, and Apoptosis in Endometrial Adenocarcinoma and Atypical Hyperplasia

This study evaluated the immunohistochemical expression of human telomerase reverse transcriptase (hTERT) in endometrial carcinoma and atypical endometrial hyperplasia, and related it to the expression of topoisomerase (TP)IIalpha (a proliferation associated enzyme); apoptosis as determined by the frequency of apoptotic bodies (ABI); mitotic counts; and other clinicopathologic variables. Immunoreactivity for hTERT and TPIIalpha as well as ABI were assessed in 57 endometrial samples (12 atypical hyperplasias, 33 endometrioid carcinomas, 12 serous/clear cell carcinomas). hTERT immunoreactivity, TPIIalpha labeling indices (LI), ABI, and ratios of the indices (ABI/TPIIalpha LI) increased from atypical hyperplasias to endometrioid carcinomas to serous/clear cell carcinomas (p < 0.0001 for each variable). hTERT expression increased with ABI (p < 0.0001), TPIIalpha LI (p = 0.0019), ABI/TPIIalpha ratios (p < 0.0001), and grade (p = 0.0005), but not with FIGO stage (p = 0.2775). TPIIalpha LI, ABI, and ratios were related to high grade (p = 0.0001 for each variable), but not with FIGO stage (p = 0.7362, p = 0.7554, and p = 0.7405, respectively). TPIIalpha LI and ABI were significantly correlated in atypical hyperplasias (p = 0.0004), endometrioid carcinomas (p < 0.0001), and serous/clear cell carcinomas (p = 0.024). Immunostaining levels for hTERT were similar in atypical hyperplasias and grade 1 endometrioid carcinomas (p = 0.1956). These results suggest that hTERT expression is closely related to proliferation, apoptosis, and high grade in endometrial carcinomas, reflecting cell cycle deregulation in endometrial carcinogenesis.

Correlation analysis of cyclin D1 aberrant expression and telomerase activity during hepatocellular canceration and its significance

AIM

To explore the relationship between cyclin D₁ aberrant expression and telomerase activity during hepatocellular canceration and its significance.

METHODS

0.5 g/L 2-AAF was used to induce rat (Wistar) hepatocellular carcinoma. Cyclin D₁ and telomerase were examined respectively by in situ hybridization techniques and PCR-TRAP-ELISA.

RESULTS

Eight rats in control group showed normal expression of cyclin D₁ and negative telomerase activity. In 16 rats with liver cirrhosis, 12 showed overexpression of cyclin D₁ and 9 showed positive telomerase activity. In 11 rats with hepatocellular carcinoma, 4 showed overexpression of cyclin D₁ and 10 showed positive telomerase activity.

CONCLUSION

Expression of cyclin D₁ and telomerase activity in liver cirrhosis and hepatocellular carcinoma were higher than those in control group. Cyclin D₁ overexpression was associated with a high telomerase activity in liver cirrhosis. There was a negative correlation between cyclin D₁ expression and telomerase activity in hepatocellular carcinoma.

Telomerase as tumor marker

Telomerase, a critical enzyme responsible for continuous cell growth, is repressed in most somatic cells except proliferating progenitor cells and activated lymphocytes, and activated in approximately 85% of human cancer tissues. Telomerase activity is a useful cancer-cell detecting marker in some types of cancers in which almost all cases show telomerase activation. In other types in which telomerase becomes upregulated according to tumor progression, it is a useful prognostic indicator. Detection of human telomerase reverse transcriptase (hTERT) mRNA or protein in various clinical samples is also applicable. However, careful attention should be paid to the false negative results due to the instability of this enzyme or hTERT mRNA and the existence of polymerase chain reaction inhibitors as well as the false-positive results due to the contamination by normal cells with telomerase activity. If these pitfalls are avoided, in situ detection of hTERT mRNA or protein will facilitate the reliability of telomerase as a tumor marker.

Repp86 expression and outcome in patients with neuroblastoma

PURPOSE

Given the well-known challenges of neuroblastoma prognosis, we investigated whether the expression of restrictedly expressed proliferation-associated protein of 86 kDa theoretical molecular mass (repp86), a proliferation-associated protein expressed in S, G2, and M phases of the cell cycle, correlates with the clinical outcome in patients with neuroblastoma.

PATIENTS AND METHODS

161 children with different stages of neuroblastoma were studied; the median follow-up time was 72.8 months. The patients were staged according to the International Neuroblastoma Staging System, and histologic grading of the tumors was performed according to the criteria of Hughes and those of the International Neuroblastoma Pathology Classification. The MYCN gene copy number was determined by Southern blot analysis or fluorescence in situ-hybridization, and repp86 expression was assessed immunohistochemically by means of monoclonal antibody Ki-S2 on paraffin sections from archival tumor samples.

RESULTS

A repp86 labeling index (RI) of more than 10% positive tumor cells significantly predicted a shortened disease-free interval and an increased tumor mortality (both P <.0001). Moreover, the RI allowed the identification of patients with favorable and adverse prognosis in subsets defined by stage, grade, age, and MYCN status. In a multivariate analysis, the RI emerged as the most important predictor of event-free and disease-specific survival with hazard ratios of 11.7 and 10.5, respectively (both P <.0001).

CONCLUSION

It seems that repp86 expression is closely associated with the biologic behavior of neuroblastoma. Assessment of the RI might, therefore, considerably refine prognostic models.

Full-length telomerase reverse transcriptase messenger RNA is an independent prognostic factor in neuroblastoma

Telomerase activity (TA) is the most recently recognized prognostic factor in neuroblastoma, and its outstanding predictive power was documented by several studies. However, TA measurements require fresh tumor tissue that is not always available in daily clinical practice. We previously described a reverse transcriptase-polymerase chain reaction assay that we used to investigate the possible prognostic relevance of the telomerase catalytic subunit, hTERT, at the mRNA level. Because hTERT mRNA undergoes alternative splicing as a regulatory mechanism of TA, we discriminated between truncated and full-length hTERT transcripts. In a retrospective study on 124 neuroblastomas, 56 (45.2%) tumors showed spliced hTERT transcripts, whereas 30 (24.2%) contained full-length hTERT transcripts. The presence of both spliced and full-length hTERT transcripts was significantly associated with MYCN amplification. hTERT in general showed no correlation to other prognostic factors, ie, International Neuroblastoma Staging System stage, International Neuroblastoma Pathology classification grade, or age at diagnosis, whereas the presence of full-length transcripts was significantly associated with higher stages. The presence of any hTERT transcripts carried no significant prognostic information, yet full-length hTERT transcripts were highly predictive of poor outcome (P < 0.0001). In a multivariate analysis, full-length hTERT transcripts and International Neuroblastoma Pathology classification grade emerged as the sole independent predictors of event-free survival, with relative risks of 10.0 and 3.9, respectively. The strong statistical correlation of full-length hTERT transcripts with clinical outcome in neuroblastoma suggests that the reverse transcriptase-polymerase chain reaction analysis of hTERT transcripts may be equatable to TA measurements. Because this assay is well suited for archival material, it could become a useful adjunct in evaluating the prognosis of individual neuroblastoma cases.

Telomeres, telomerase, and telomerase inhibition: clinical implications for cancer

Telomeres are located at the ends of eukaryotic chromosomes. The enzyme telomerase synthesized them, and they are responsible for maintaining the lengths of chromosomes. Absence of telomerase is associated with telomere shortening and aging of somatic cells, but high telomerase activity is observed in over 90% of human cancer cells. Although the disappearance of telomerase with aging is considered a natural defense against development of cancer, it is not known what triggers the reappearance of telomerase in cancer cells. Telomerase activity is directly correlated with the expression of its active catalytic component, the human telomerase reverse transcriptase (hTERT), which is controlled primarily at the level of transcription. An earlier paper discussed the relationship of telomerase with aging. In this article, the contemporary literature is reviewed to explore the associations between telomerase, telomerase inhibition, and cancer. Because most cancers occur in old age, with the aging of the population, the number of people suffering from cancer is expected to increase in the coming decades. It is not known what roles telomerase and hTERT play in the complex relationship between aging and cancer. Data from experimental studies suggest that telomerase assay could potentially play a role in the diagnosis and prognosis of cancers. There is also evidence that telomerase inhibitors might be used as anticancer agents. As the knowledge of the relationships between telomerase and cancer and between telomerase and aging advances, it is hoped that more about the interacting relationships between telomerase, aging, and cancer will be learned.

Clinical utility of telomerase in cancer

This review will focus on the clinical utilities of telomerase for human cancer diagnosis. Much attention has been focused on detection of telomerase activity and its essential components (hTR and hTERT) in cancer and noncancerous tissues. Expression of hTR and hTERT is upregulated in almost all human malignant tumors but not in benign or normal tissues with the exception of germline cells, proliferative stem cells, activated lymphocytes, and certain benign tumors. Thus, telomerase is a useful marker for cancer diagnosis and in some instance as a prognostic indicator of outcome. Telomerase detection in cells derived from breast fine needle aspirates, bronchial washes, and pancreatic juices show high sensitivity and specificity for cancer detection. In tissue samples, the level of telomerase activity is a useful prognostic indicator in certain adult cancers such as gastric and colon cancers and in neuroblastomas. Immunohistochemical detection of hTERT will facilitate exact diagnosis of the telomerase positive cells and expand the application of telomerase in cancer diagnosis.

Regulation of telomerase activity by alternate splicing of human telomerase reverse transcriptase mRNA in a subset of neuroblastomas

It has been proposed that the regulation of telomerase takes place at the transcriptional level, the expression of the catalytic subunit human telomerase reverse transcriptase (hTERT) being crucial for telomerase activity (TA). Recently, differential splicing of hTERT mRNA has been demonstrated in various tissues during embryonal development, and it has been suggested that only full-length transcripts translate into functionally active telomerase. With this in view, we analyzed the different hTERT transcripts by reverse transcriptase-polymerase chain reaction in neuroblastic tumors and compared the results with the TA, the tumor growth fraction, and the MYCN status. In a series of 38 neuroblastic tumors, high TA and full-length hTERT transcripts were found in nine samples, whereas nine samples showed absence of both enzymatic activity and hTERT transcripts. Interestingly, in another eight samples, low or absent TA coincided with a lack of full-length hTERT transcripts. Eleven samples contained hTERT transcripts with low or undetectable TA and one sample had low TA but no hTERT transcripts. TA correlated with MYCN amplification and was weakly associated with the proliferative activity. Moreover, a significant correlation with tumor progression was observed. Our findings point at a posttranscriptional regulation of TA in a subset of neuroblastic tumors. Because high TA was detected only in tumors with full-length hTERT transcripts, reverse transcriptase-polymerase chain reaction analysis of archival neuroblastic tumor samples might help to appraise the malignant potential in individual cases.