In situ detection of telomerase catalytic subunit mRNA in glioblastoma multiforme

Therapeutic targeting of telomerase ameliorates experimental choroidal neovascularization

Choroidal neovascularization (CNV) is the principal driver of blindness in neovascular age-related macular degeneration (nvAMD). Increased activity of telomerase, has been associated with endothelial cell proliferation, survival, migration, and invasion in the context of tumor angiogenesis. Expanding on this knowledge, we investigated the role of telomerase in the development of CNV in mouse model. We observed increased gene expression and activity of telomerase in mouse CNV. Genetic deficiency of the telomerase components, telomerase reverse transcriptase (Tert) and telomerase RNA component (Terc) suppressed laser-induced CNV in mice. Similarly, a small molecule inhibitor of TERT (BIBR 1532), and antisense oligonucleotides (ASOs) targeting Tert and Terc reduced CNV growth. Bone marrow chimera studies suggested that telomerase activity in non-bone marrow-derived cells is crucial for the development of CNV. Comparison of BIBR 1532 with VEGF neutralizing therapeutic strategy in mouse revealed a comparable level of angiosuppressive activity. However, when BIBR and anti-VEGF antibodies were administered as a combination at sub-therapeutic doses, a statistically significant suppression of CNV was observed. These findings underscore the potential benefits of combining sub-therapeutic doses of BIBR and anti-VEGF antibodies for developing newer therapeutic strategies for NV-AMD. Telomerase inhibition with BIBR 1532 suppressed induction of multiple cytokines and growth factors critical for neovascularization. In conclusion, our study identifies telomerase as a promising therapeutic target for treating neovascular disease of the eye and thus provides a proof of principle for further exploration of telomerase inhibition as a novel treatment strategy for nvAMD.

Synthesis and Characterization of Chrysin-loaded PCL-PEG-PCL nanoparticle and its effect on breast cancer cell line

BACKGROUND

Nano-therapy exhibit the potential of revolutionizing cancer therapy. This field introduces nanovectors/nanocarriers for anticancer drugs targeted delivery, and also finds application in imaging. Chrysin, a natural flavonoid, was recently studied as having important biological roles in chemical defenses, nitrogen fixation, anti-inflammatory, and anti-oxidant properties. We aim at studying the effect of nano-chrysin on breast cancer cell line.

METHODS

The effect of chrysin loaded PCL-PEG-PCL was studied on T47D breast cancer cell line. The structure and drug-loading of chrysin were characterized using ¹H NMR, FT-IR and SEM. The in vitro cytotoxicity of pure and nano-chrysin was tested by the MTT assay. Gene expression of FTO, hTERT, and BRCA1 were evaluated using Real-time PCR.

RESULTS

Data analysis from MTT assay showed that chrysin has a time-dependent cytotoxic effect on T47D cell line. Furthermore, the results of Real-time PCR suggested that encapsulated chrysin have higher antitumor effect on gene expression of FTO, BRCA1 and hTERT than free chrysin.

CONCLUSION

Combined nano-chrysin therapy will not only improve cancer cell cytotoxicity, but also be a complementary and potential complex in breast cancer therapy.

Genetic variations in TERT-CLPTM1L genes and risk of lung cancer in a Chinese population

BACKGROUND

This study was conducted to investigate the association between single nucleotide polymorphisms (SNPs) in telomerase reverse transcriptase (TERT) and cleft lip and palate transmembrane1-like (CLPTM1L) and lung cancer risk in a Chinese population.

METHODS

We performed a hospital-based case-control study, including 980 lung cancer cases and 1000 cancer-free controls matched for age and sex. Each case and control was interviewed to collect information by well-trained interviewers. A total of 5 ml of venous blood was collected for genotype testing of TERT rs2736098 and CLPTM1L rs401681 using TaqMan methodology.

RESULTS

The results revealed that the variant homozygote TERT rs2736098TT was associated with an increased risk of lung cancer (OR=2.017, 95%CI=1.518-2.681), especially lung adenocarcinoma (OR=2.117, 95%CI=1.557-3.043) and small cell carcinoma (OR=1.979, 95%CI: 1.174-3.334), compared with the TERT rs2736098CC genotype. Similar results were observed in non-smokers.

CONCLUSION

The TERT rs2736098 polymorphism might affect the susceptibility to lung cancer in Chinese populations. The associations need to be verified in larger and different populations.

Radiation-induced upregulation of telomerase activity escapes PI3-kinase inhibition in two malignant glioma cell lines

Tumor relapse after radiotherapy is a great concern in the treatment of high-grade gliomas. Inhibition of the PI3-kinase/AKT pathway is known to radiosensitize cancer cells and to delay their DNA repair after irradiation. In this study, we show that the radiosensitization of CB193 and T98G, two high-grade glioma cell lines, by the PI3K inhibitor LY294002, correlates with the induction of G1 and G2/M arrest, but is inconsistently linked to a delayed DNA double-strand break (DSBs) repair. The PI3K/AKT pathway has been shown to activate radioprotective factors such as telomerase, whose inhibition may contribute to the radiosensitization of cancer cells. However, we show that radiation upregulates telomerase activity in LY-294002-treated glioma cells as well as untreated controls, demonstrating a PI3K/AKT-independent pathway of telomerase activation. Our study suggests that radiosensitizing strategies based on PI3-kinase inhibition in high-grade gliomas may be optimized by additional treatments targeting either telomerase activity or telomere maintenance.

Overexpression of hTERT in potentially malignant colorectal laterally spreading tumors

Human telomerase reverse transcriptase (hTERT) is the main subunit of the core enzyme telomerase, which consists of three subunits. Telomeres are essential for chromosomal stability and integrity, protecting the ends of chromosomes from degradation and preventing chromosomal end fusions and recombination. A loss of telomere function is a major mechanism for the generation of chromosomal abnormalities. Telomere shortening leads to mutations, chromosome rearrangements and translocations. Colorectal laterally spreading tumors (LSTs) are a special type of superficial colorectal tumor. They are considered to have a high malignancy potential. The aim of the present study was to characterize the expression of hTERT in an LST cell line and paraffin sections. Immunohistochemistry was utilized to examine the protein expression of hTERT in the LST cell line, 48 resected LSTs, 48 protruded-type colorectal adenomas (PAs) and 48 normal mucosa samples. Statistical analyses were applied to test the associations between hTERT expression and clinicopathological parameters. The present study demonstrated that the positive expression levels of hTERT in LSTs, PAs and normal mucosa were 60.4, 22.9 and 10%, respectively. Compared with polypi and normal mucosa, the expression levels of hTERT were significantly increased in LSTs. The expression of hTERT was also observed in the LST cell line. The expression of hTERT was significantly higher in LSTs, which may indicate a potential for malignancy.

Fine-mapping of a region of chromosome 5p15.33 (TERT-CLPTM1L) suggests a novel locus in TERT and a CLPTM1L haplotype are associated with glioma susceptibility in a Chinese population

Two genome-wide association studies (GWAS) have identified 5p15.33 (TERT-CLPTM1L) as one of the susceptible regions for glioma in European background. A replication research of our group highlighted the association signals in the TERT gene of this region in a Chinese Han population. To comprehensively explore the region of glioma association at 5p15.33 and to refine the potential causal variants to a smaller critical region, we conducted a fine-mapping association study among 983 cases and 1,024 controls in a Chinese Han population. Using Hapmap3 datasets as a reference, we genotyped 16 tag SNPs across this 87.9-kb region encompassing TERT. Significant association with glioma risk was observed for rs2853677 [GG vs. GA: adjusted OR = 1.46, p = 5.51 × 10(-6), GG vs. AA: adjusted OR = 1.72, p = 7.64 × 10(-6), GG vs. GA and AA: adjusted OR = 1.96, p = 6.8 × 10(-6)] in TERT and an uncommon CLPTM1L haplotype G-T-A of rs4635969, rs6554759 and rs414965 (haplotype frequency = 0.07) was associated with higher glioma risk compared with the most common G-C-G haplotype (adjusted OR = 1.44, simulated p = 6.00 × 10(-3) under additive model). Our results indicate that sequence variants in the region flanking rs2853677 may account for the GWAS and replication signals identified in 5p15.33 for glioma susceptibility in Chinese population; besides, haplotype G-T-A in CLPTM1L also confers a risk to glioma suggesting CLPTM1L is also involved in the etiology of glioma. Additional studies especially those taking advantage of sequencing platforms are warranted to further confirm the conclusions and go deeper with our findings.

Genetic variations in TERT-CLPTM1L genes and risk of squamous cell carcinoma of the head and neck

Single-nucleotide polymorphisms (SNPs) of TERT-rs2736098 (C > T) and CLPTM1L-rs401681(C > T) at the 5p15.33 locus are significantly associated with cancer risk as reported in genome-wide association studies (GWAS), but there are no reported studies for squamous cell carcinoma of the head and neck (SCCHN). In a case-control study of 1079 SCCHN cases and 1115 cancer-free controls of non-Hispanic whites who were frequency matched by age and sex, we genotyped for these two SNPs and assessed their associations with SCCHN risk. Compared with the CC genotypes of each polymorphism, the associations of a slightly reduced risk of SCCHN with the variant genotypes of CT + TT of both polymorphisms were approaching statistical significance [Odds ratio (OR) = 0.90, 95% confidence interval (CI) = 0.76-1.08 for TERT-rs2736098 and OR = 0.86, 95% CI = 0.71-1.04 for CLPTM1L-rs401681, respectively]. When the two SNPs were combined, the variant genotypes of the two SNPs were significantly associated a moderately reduced risk of SCCHN (OR = 0.82, 95% CI = 0.67-0.99), and the number of variant genotypes was associated with a significantly reduced risk in a dose-response manner (P = 0.028). Furthermore, the reduced risk was more pronounced in ever smokers, ever drinkers and patients with oropharyngeal cancer. Our results suggested that these two SNPs at the 5p15.33 locus may be associated with a reduced risk of SCCHN, particularly for their combined effect. Although we added additional evidence for the association of the two SNPs with cancer risk as reported in GWAS, additional studies are needed to replicate our findings.

Thymoquinone induces telomere shortening, DNA damage and apoptosis in human glioblastoma cells

Background

A major concern of cancer chemotherapy is the side effects caused by the non-specific targeting of both normal and cancerous cells by therapeutic drugs. Much emphasis has been placed on discovering new compounds that target tumour cells more efficiently and selectively with minimal toxic effects on normal cells.

Methodology/Principal Findings

The cytotoxic effect of thymoquinone, a component derived from the plant Nigella sativa, was tested on human glioblastoma and normal cells. Our findings demonstrated that glioblastoma cells were more sensitive to thymoquinone-induced antiproliferative effects. Thymoquinone induced DNA damage, cell cycle arrest and apoptosis in the glioblastoma cells. It was also observed that thymoquinone facilitated telomere attrition by inhibiting the activity of telomerase. In addition to these, we investigated the role of DNA-PKcs on thymoquinone mediated changes in telomere length. Telomeres in glioblastoma cells with DNA-PKcs were more sensitive to thymoquinone mediated effects as compared to those cells deficient in DNA-PKcs.

Conclusions/Significance

Our results indicate that thymoquinone induces DNA damage, telomere attrition by inhibiting telomerase and cell death in glioblastoma cells. Telomere shortening was found to be dependent on the status of DNA-PKcs. Collectively, these data suggest that thymoquinone could be useful as a potential chemotherapeutic agent in the management for brain tumours.

Telomerase activity and telomerase reverse transcriptase catalytic subunit expression in canine lymphoma: correlation with Ki67 immunoreactivity

Increased telomerase activity (TA) has been found in human and canine solid tumours, stem cells and somatic tissues with enhanced proliferative potential. The relationship between TA in normal and malignant lymphoid tissues remains unclear. The TA and the expression of canine telomerase reverse transcriptase catalytic subunit (dogTERT) messenger RNA (mRNA) were analyzed in malignant lymph nodes from 30 dogs with lymphoma, from two dogs with non-neoplastic illness and from two clinically normal dogs, demonstrating a statistically significant difference between TA in lymphoma lymph nodes (n = 30) and normal nodes (n = 4) but no significant difference in dogTERT mRNA expression. In addition, the expression of telomerase reverse transcriptase catalytic subunit (TERT) protein and Ki67 was analyzed in malignant lymph nodes from 10 dogs with lymphoma and from two clinically normal dogs by immunohistochemistry. TERT expression was associated with Ki67 in all lymphoma nodes (n = 10), and differences were illustrated between TERT and Ki67 expression between lymphoma (n = 10) and non-lymphoma (n = 2) nodes. This data support further investigation of telomerase in canine haematopoietic neoplasia through large-scale prospective studies.

The promise of telomere length, telomerase activity and its regulation in the translocation-dependent cancer ESFT; clinical challenges and utility

The Ewing's sarcoma family of tumours (ESFT) are diagnosed by EWS-ETS gene translocations. The resulting fusion proteins play a role in both the initiation and maintenance of these solid aggressive malignant tumours, suppressing cellular senescence and increasing cell proliferation and survival. EWS-ETS fusion proteins have altered transcriptional activity, inducing expression of a number of different target genes including telomerase. Up-regulation of hTERT is most likely responsible for the high levels of telomerase activity in primary ESFT, although telomerase activity and expression of hTERT are not predictive of outcome. However levels of telomerase activity in peripheral blood may be useful to monitor response to some therapeutics. Despite high levels of telomerase activity, telomeres in ESFT are frequently shorter than those of matched normal cells. Uncertainty about the role that telomerase and regulators of its activity play in the maintenance of telomere length in normal and cancer cells, and lack of studies examining the relationship between telomerase activity, regulators of its activity and their clinical significance in patient samples have limited their introduction into clinical practice. Studies in clinical samples using standardised assays are critical to establish how telomerase and regulators of its activity might best be exploited for patient benefit.

A tandem repeat of human telomerase reverse transcriptase (hTERT) and risk of breast cancer development and metastasis in Chinese women

Telomerase reactivation, which prevents telomere shortening and maintains cell viability, is crucial for the continued growth or progression of cancer cells. A minisatellite tandem repeat, MNS16A, located in the downstream of the human telomerase reverse transcriptase (hTERT) gene was recently identified and reported to have an effect on hTERT expression and telomerase activity. The aim of this study was to test the hypothesis that the MNS16A variant is associated with risk of breast cancer development and metastasis. We genotyped MNS16A variant in hTERT in a case-control study of 1029 histologically confirmed breast cancer patients and 1107 cancer-free controls in Chinese women. The variant genotypes (302/271, 302/243 and 243/243) of MNS16A were associated with a significantly increased risk of breast cancer [adjusted odds ratio (OR) = 1.50, 95% confidence interval (CI) = 1.15-1.96], compared with the wild-type 302/302 genotype. In stratified analyses, we found that the 302/271 genotype was associated with a significantly increased risk of axillary lymph nodes metastasis (adjusted OR = 2.13, 95% CI = 1.05-4.33) compared with wild-type 302/302 genotype. These findings indicate that the MNS16A variant in the hTERT gene may contribute to the risk of breast cancer development and metastasis in Chinese women.

Telomerase: is it the future diagnostic and prognostic tool in human cancer?

A number of methods exist to detect levels of telomerase activity and the presence of telomerase subunits in a variety of tissues. As telomerase activation seems to be an important step in tumorigenesis, accurate detection of the presence and activity of the enzyme and its subunits is vital. The original method of detecting telomerase activity was developed by Kim and coworkers in 1994, and was termed the telomeric repeat amplification protocol. This assay led to a staggering increase in the number of telomerase-associated publications in scientific journals (85 publications from 1974-1994, 5063 publications from 1994-2004). A number of methods have been described to detect telomeres and to measure their length, with the standard measurement of telomere length performed using a modification of the Southern blot protocol. RNA in situ hybridization can be performed to detect levels of the RNA component of telomerase, and standard in situ hybridization and immunohistochemistry can be applied to examine expression levels and localization of the catalytic subunit of the enzyme. Reverse transcriptase PCR has also been applied to assess expression levels of the telomerase components in various tissues. This review provides a synopsis of telomeres, telomerase, telomerase and cancer, and finally, methods for the detection of telomerase in cancer.

Telomerase reverse transcriptase (TERT) expression and proliferation in canine brain tumours

Telomerase is a ribonucleoprotein enzyme complex that synthesizes telomere DNA. It is detected in 85-90% of malignant tumours in humans, but not in most somatic cells. Because telomerase plays a critical role in cell immortality, it represents an important target for anticancer therapies. We have previously shown that the dog is a potentially useful model for evaluating telomerase-based therapeutics. In this present study we analysed 93 canine brain tumours for telomerase reverse transcriptase (TERT) expression by immunohistochemistry. TERT immunoreactivity was detected in 16 of 50 grade 1 (32%) and 29 of 43 grade 2 tumours (67.4%), demonstrating a statistically significant association with histological grade (P = 0.00012). A subset of 51 tumours was also assessed for MIB-1 expression. The MIB-1 labelling index (LI) was found to correlate significantly with tumour grade, with a mean MIB-1 LI of 1.5% for grade 1 tumours, as compared with a mean MIB-1 LI of 21.7% for grade 2 tumours (P << 0.001). The MIB-1 LI was also significantly associated with TERT expression in all brain tumours (P << 0.001). These data further support the dog as a model for the preclinical development of telomerase-based therapeutics in brain tumours.

In situ detection of hTERT variants in anaplastic large cell lymphoma

The expression of hTERT and its isoforms is difficult to assess in lymphoma tissues with the commonly used reverse transcription-polymerase chain reaction (RT-PCR) methods, because non-neoplastic lymphocytes expressing hTERT are always present in the lymphomatous infiltrates. The present study aimed to investigate hTERT mRNA variants in anaplastic large cell lymphoma (ALCL) (n = 38) with in situ hybridization (ISH), along with the immunodetection of hTERT protein. Probes for the identification of mRNAs containing (Bplus) and lacking (Bdel) exons 7 and 8 of the hTERT mRNA were used. Normal lymphocyte populations equally expressed both Bplus and Bdel mRNAs. Although all ALCL examined were found positive for hTERT expression with RT-PCR, hTERT mRNAs were identified in 68% of these tumors with ISH, with a higher incidence in the group bearing ALK translocations (10 out of 11; 90.9%) compared to the ALK negative group (17 out of 27; 59.3%) (PPearson's = 0.002). The same results were obtained with immunohistochemistry for hTERT. In approximately 50% of cases, only Bplus positive cells were identified, again with a higher incidence in the ALK positive compared to the ALK negative group (PPearson's = 0.016). In conclusion, ISH for hTERT mRNAs appears to be a valuable tool for the investigation of hTERT expression in lymphomas. Aberrations in hTERT variant profiles and a decline in the expression of the B deleted isoform may be associated with the pathogenesis of ALCL, especially with respect to ALK positive tumors.

Establishing tumor cell lines from aggressive telomerase-positive chordomas of the skull base

✓ Permanent cell cultures are invaluable tools for understanding the biological characteristics of tumors. In the present study the authors report on the establishment of permanent human cell lines from three cases of aggressive chordomas of the clival region. All of the parental tumors showed telomerase activity. Cultured chordoma cells had a doubling time of 5 to 7 days and grew as a monolayer of cells that retained both the immunophenotype and the p53 status of the parental tumor. In vitro, chordoma cells overexpressed telomerase, supporting the hypothesis that this enzyme is required for the immortalization process.

hTERT immunopositivity patterns in the normal brain and in astrocytic tumors

Accumulating data about the impact of hTERT in astrocytic tumor carcinogenesis and recent evidence about its association with disease outcome prompt the evaluation of this molecule with methods applicable in routine pathology practice. In this study, we investigated hTERT protein expression with immunohistochemistry (IHC) and the NCL-hTERT antibody in 49 astrocytic tumors. Results were validated with the assessment of hTERT mRNA (relative quantification, identification of splice variants, in situ hybridization). Specific nuclear hTERT immunostaining patterns (IPs) were characterized as patterns As (single large dot) and Am (multiple dots) without nucleoplasm staining and pattern B (nucleoplasm staining with or without dots), corresponding to low and high relative hTERT expression values (P<0.0001). Low- and high-grade astrocytic tumors were found positive for hTERT in 74 and 85% of cases, respectively. Heterogeneity in the distribution of hTERT-positive cells was observed in all tumors. The prevailing nuclear IPs differed significantly between pilocytic astrocytomas (pattern As) and the rest of histologic types up to glioblastoma (patterns Am and B) (P<0.0001). The described nuclear IPs were also observed in non-neoplastic cells. Positive endothelial cells were found in astrocytic tumors of all grades, even when tumor cells showed no hTERT immunoreactivity. A subset of mature normal neurons was positive for hTERT (pattern As), suggesting a role for this molecule in neuronal maintenance in the adult brain. The nuclear hTERT IPs described here may reflect the functional status of non-neoplastic brain and neoplastic astrocytic cells and support the model of a continuum in the development of glioblastomas from diffuse fibrillary astrocytomas.

Survival prediction in patients with glioblastoma multiforme by human telomerase genetic variation

PURPOSE

Glioblastoma multiforme (GBM) is the most common and aggressive glioma with the poorest survival. Use of biomarkers for screening patients with GBM may be used to modify treatments and improve outcomes. The level of human telomerase (hTERT) expression is an independent predictor of outcome of many cancers, and a functional variant of hTERT MNS16A (shorter tandem repeats or short [S] allele) is associated with increased hTERT mRNA expression. We investigated whether hTERT MNS16A variant genotype predicted survival in GBM patients.

PATIENTS AND METHODS

We genotyped hTERT MNS16A in 299 GBM patients using polymerase chain reaction and determined hTERT genotype by classifying the DNA band of 243 or 272 base pairs (bp) as S allele and 302 or 333 bp as long (L) allele. We compared overall survival using Kaplan-Meier estimates and equality of survival distributions using the log-rank test, and we computed univariate and multivariate Cox proportional hazards models to estimate the effects of selected variables.

RESULTS

Overall survival differed significantly by hTERT MNS16A genotype, with median survivals of 25.1, 14.7, and 14.6 months for the SS, SL, and LL genotypes, respectively. Compared with the SS genotype, the hazard ratios for the SL and LL genotypes were 1.69 and 1.87, respectively, after adjustment for other factors. Multivariate Cox regression analysis showed an independent statistically significant association between the hTERT MNS16A variant genotype and outcome.

CONCLUSION

A functional hTERT MNS16A genotype is a potential biomarker for assessment of survival outcome of GBM. Larger studies are needed to verify these findings.

Telomerase inhibition by stable RNA interference impairs tumor growth and angiogenesis in glioblastoma xenografts

Telomerase is highly expressed in advanced stages of most cancers where it allows the clonal expansion of transformed cells by counteracting telomere erosion. Telomerase may also contribute to tumor progression through still undefined cell growth-promoting functions. Here, we inhibited telomerase activity in 2 human glioblastoma (GBM) cell lines, TB10 and U87MG, by targeting the catalytic subunit, hTERT, via stable RNA interference (RNAi). Although the reduction in telomerase activity had no effect on GBM cell growth in vitro, the development of tumors in subcutaneously and intracranially grafted nude mice was significantly inhibited by antitelomerase RNAi. The in vivo effect was observed within a relatively small number of population doublings, suggesting that telomerase inhibition may hinder cancer cell growth in vivo prior to a substantial shortening of telomere length. Tumor xenografts that arose from telomerase-inhibited GBM cells also showed a less-malignant phenotype due both to the absence of massive necrosis and to reduced angiogenesis.

Glioblastoma cells deficient in DNA-dependent protein kinase are resistant to cell death

DNA-dependent protein kinase (DNA-PK), a nuclear serine/threonine kinase, is responsible for the DNA double-strand break repair. Cells lacking or with dysfunctional DNA-PK are often associated with mis-repair, chromosome aberrations, and complex exchanges, all of which are known to contribute to the development of human cancers including glioblastoma. Two human glioblastoma cell lines were used in the experiment, M059J cells lacking the catalytic subunit of DNA-PK, and their isogenic but DNA-PK proficient counterpart, M059K. We found that M059K cells were much more sensitive to staurosporine (STS) treatment than M059J cells, as demonstrated by MTT assay, TUNEL detection, and annexin-V and propidium iodide (PI) staining. A possible mechanism responsible for the different sensitivity in these two cell lines was explored by the examination of Bcl-2, Bax, Bak, and Fas. The cell death stimulus increased anti-apoptotic Bcl-2 and decreased pro-apoptotic Bcl-2 members (Bak and Bax) and Fas in glioblastoma cells deficient in DNA-PK. Activation of DNA-PK is known to promote cell death of human tumor cells via modulation of p53, which can down-regulate the anti-apoptotic Bcl-2 member proteins, induce pro-apoptotic Bcl-2 family members and promote a Bax-Bak interaction. Our experiment also demonstrated that the mode of glioblastoma cell death induced by STS consisted of both apoptosis and necrosis and the percentage of cell death in both modes was similar in glioblastoma cell lines either lacking DNA-PK or containing intact DNA-PK. Taken together, our findings suggest that DNA-PK has a positive role in the regulation of apoptosis in human glioblastomas. The aberrant expression of Bcl-2 family members and Fas was, at least in part, responsible for decreased sensitivity of DNA-PK deficient glioblastoma cells to cell death stimuli.

A Robust Assay for Alternative Lengthening of Telomeres in Tumors Shows the Significance of Alternative Lengthening of Telomeres in Sarcomas and Astrocytomas

Purpose and Experimental Design: Telomeres of tumor cells may be maintained by telomerase or by alternative lengthening of telomeres (ALT). The standard ALT assay requires Southern analysis of high molecular weight genomic DNA. We aimed to establish and validate an ALT assay suitable for archived paraffin-embedded tumors and to use it to examine the prevalence and clinical significance of ALT in various types of tumors that are often telomerase negative.

Results: To assay for ALT, we detected ALT-associated promyelocytic leukemia (PML) bodies (APBs) by combined PML immunofluorescence and telomere fluorescence in situ hybridization. APBs are PML nuclear domains containing telomeric DNA and are a known hallmark of ALT in cell lines. The APB assay concurred with the standard ALT assay in 62 of 62 tumors and showed that 35% of 101 soft tissue sarcomas (STS), 47% of 58 osteosarcomas (especially younger patients), 34% of 50 astrocytomas, and 0% of 17 papillary thyroid carcinomas were ALT positive (ALT+). The prevalence of ALT varied greatly among different STS subtypes: malignant fibrous histiocytomas, 77%; leiomyosarcomas, 62%; liposarcomas, 33%; synovial sarcomas, 9%; and rhabdomyosarcomas, 6%. ALT correlated with survival in glioblastoma multiforme and occurred more often in lower-grade astrocytomas, but ALT+ and ALT− sarcomas were equally aggressive in terms of grade and clinical outcome.

Conclusion: The APB assay for ALT is suitable for paraffin-embedded tumors. It showed that a substantial proportion of STS, osteosarcomas, and astrocytomas, but not papillary thyroid carcinomas use ALT. APB positivity correlated strongly with survival of patients with astrocytomas.

Tumor cells fail to trans-induce telomerase in human umbilical vein endothelial cell cultures

The shortening of the telomeres that occurs in most somatic cells and untransformed cell cultures is considered a hallmark of cellular senescence. Re-activation of telomerase, which is usually present in immortal cells, avoids telomere shortening and considerably extends the culture life span. Normal human endothelial cells are characterized by an accelerated rate of telomere shortening and reach replicative senescence after a limited number of cell divisions. It has recently been reported that human telomerase reverse transcriptase expression may be strongly up-regulated in human endothelial cells cocultivated with tumor cells. Due to the important implications of this finding on tumor progression, we have extensively analyzed for the presence of telomerase in primary human endothelial cells either cocultivated with tumor cells or grown with tumor-conditioned medium. We found modest, but readily detectable, amounts of telomerase in all human endothelial cell cultures analyzed that disappeared as the cultures approached senescence. Quantitative reverse transcription-PCR also showed a direct correlation between human telomerase reverse transcriptase expression and the proliferative index of the cultures. Nevertheless, we did not find any evidence of induction of telomerase activity by tumor cells in any of the tested conditions. All data indicate that telomerase in human endothelial cells follows an activation program that is strictly associated to the culture growth rate.

Prognostic Factors in Resected Stage I Non–Small-Cell Lung Cancer: A Multivariate Analysis of Six Molecular Markers

Purpose

To analyze the prognostic significance of six molecular biomarkers (death-associated protein kinase [DAPK] promoter methylation, interleukin-10 [IL-10] protein expression, cyclooxygenase-2 [COX-2] mRNA expression, human telomerase reverse transcriptase catalytic subunit [hTERT] mRNA expression, retinoic acid receptor-beta [RAR-β] mRNA expression, and K-ras mutational status) in stage I non–small-cell lung cancer (NSCLC) patients.

Patients and Methods

Biomarker analyses were performed on tumors from 94 patients with stage I NSCLC who underwent surgical resection at our institution. A minimum follow-up period of 5 years was required. DAPK methylation was assessed by methylation-specific polymerase chain reaction (PCR). RAR-β, COX-2, and hTERT mRNA levels were determined by in situ hybridization with digoxigenin-labeled antisense riboprobes. K-ras mutation status was determined by the PCR–primer introduced restriction with enrichment for mutant alleles method. IL-10 protein expression was analyzed by immunohistochemistry using a polyclonal antihuman IL-10 antibody. Cancer-specific survival was analyzed with a Cox proportional hazards model. To identify independent prognostic factors, a stepwise selection method was used.

Results

DAPK methylation, IL-10 lack of expression, COX-2 expression, hTERT expression, RAR-β expression, and K-ras mutations were observed in 46.8%, 29.8%, 59.6%, 34.0%, 23.4%, and 34.0% of patients, respectively. In the final model, DAPK methylation and IL-10 lack of expression were significant negative prognostic factors for cancer-specific survival, whereas COX-2 expression was of borderline significance.

Conclusion

In this cohort of resected stage I NSCLC patients, molecular markers that independently predict cancer-specific survival have been identified. The prognostic roles of DAPK methylation, IL-10, and other biomarkers in NSCLC merit further investigation.

Nuclear telomerase is less accessible to antibody probing than known nuclear antigens: retrieval with new immunostaining buffer

Telomerase is an important tumor marker but few antibodies to the enzyme have been described or used without difficulty in histochemical detection. Here we report specific detection of the enzyme in cell and tissue preparations using a new monoclonal antibody (mAb 476) and a new antigen-retrieval buffer (Enhancing buffer). When used to detect telomerase under normal immunostaining conditions in HL-60 cells or tissue sections of hepatocellular carcinoma or metastatic choriocarcinoma, unexpectedly, the antibody stained the cytoplasm rather than the nucleus. Nuclear staining, however, was revealed using the Enhancing buffer. Since other nuclear antigens in the HL-60 cell could be stained both ordinarily and in the Enhancing buffer, nuclear telomerase appears to be shrouded by the nuclear matrix or blocked by accessory proteins. The cytoplasmic activity seen in normal buffer but absent largely from the Enhancing buffer may be an artifact or the nascent, "naked" enzyme. With a known cytoplasmic antigen (proteinase-3) chosen arbitrarily for comparison, the antigenicity was found enhanced, instead, by the Enhancing buffer. The mode of action of the Enhancing buffer differs from that of microwave irradiation or the signal amplification (CSA) used by some investigators. The latter was found to enhance the cytoplasmic reactivity rather than the nuclear reactivity of mAb 476.

Correlation between the expression of telomerase reverse transcriptase and proliferative activity in breast cancer cells using an immunocytochemical restaining method

Telomerase activity is thought to contribute to the immortality of cancers. Recently, some investigators described a correlation between the activity of telomerase and the proliferative activity of cancer cells. The aim of this study was to evaluate the correlation between the expression of telomerase-associated protein and proliferative activity. Telomerase reverse transcriptase (TERT) is one of the proteins that correlates with telomerase activity. We investigated TERT protein and its mRNA, and examined the correlation between the TERT protein and Ki-67, which reflects proliferative activity with immunostaining, and its mRNA, which correlates with telomerase activity, using in situ hybridization. Imprint smears from 17 invasive ductal adenocarcinomas were investigated. In most cases positive for TERT mRNA, the percentage of TERT protein-positive cells was also high and was closely related to mRNA (P = 0.024). The positive rates of TERT for the cases with lymph node metastasis were significantly higher than those for the cases without metastasis (P = 0.046). The positivity of TERT protein also correlated significantly with the Ki-67-positive rate (r = 0.82). As the proliferation activity increased, the number of cells positive for both proteins also increased (r = 0.89). In conclusion, it was suggested that the expression of TERT protein is associated with the expression of Ki-67, and is concerned with maintenance of the high proliferative activity in cancer cells with aggressive proliferation.

The diagnostic and prognostic relevance of human telomerase reverse transcriptase mRNA expression detected in situ in patients with nonsmall cell lung carcinoma

BACKGROUND

The objectives of this study were to evaluate the diagnostic and prognostic relevance of human telomerase reverse transcriptase (hTERT) detected in situ in patients with nonsmall cell lung carcinoma (NSCLC) and to investigate the possible correlations between hTERT mRNA in NSCLC and the patients' clinicopathologic features, including survival.

METHODS

hTERT mRNA was detected by in situ hybridization in 146 samples from patients with NSCLC. The signal intensity of hTERT mRNA expression was evaluated by two independent observers. The expression level was defined subjectively as strong, moderate, or weak.

RESULTS

hTERT mRNA was detected mainly in the cytoplasm of tumor cells. It was detected in the cytoplasm of 100% of samples from patients with NSCLC but was not detected in normal lung tissue, except in activated lymphocytes. There was a significant correlation between hTERT mRNA expression and pathologic tumor status, pathologic disease stage (pStage), and Ki-67 labeling index. There was no significant correlation between hTERT mRNA expression and age, gender, pathologic lymph node status (pN), histology, or tumor differentiation. The 5-year survival rates for patients with strong and moderate hTERT mRNA expression levels were 46.9% and 77.9%, respectively; the difference was statistically significant (P = 0.0001). A multivariate analysis of survival using a stepwise procedure revealed that hTERT mRNA expression, pN status, pStage, and age were statistically significant prognostic factors (P = 0.0029, P = 0.0012, P = 0.0237, and P = 0.0496, respectively).

CONCLUSIONS

The findings suggested that hTERT mRNA expression may be useful for the diagnosis of NSCLC and also may be an independent prognostic factor for patients with NSCLC.

Chordoma of the skull base: predictors of tumor recurrence

OBJECT

Chordomas of the skull base are generally regarded as slow-growing tumors; however, approximately 20% of these lesions have been shown to recur as early as 1 year postsurgery. The classic pathological paradigms are poor predictors of outcome, and additional markers are needed to identify patients at risk for early tumor recurrence. In this study the authors describe such a marker.

METHODS

In a series of 26 patients with chordomas of the skull base, the authors investigated the relationship between the biological behavior of the tumor, which was determined according to the interval for its recurrence and volume doubling time, and several pathological and molecular features, which included the histological variant, proliferative activity, mutation of p53 protein, expression of human telomerase reverse transcriptase (hTERT) messenger (m)RNA, loss of heterozygosity (LOH), and microsatellite instability. The major finding in this study was that hTERT mRNA expression in chordoma cells identifies those tumors that exhibit unusually fast rates of growth. The expression of hTERT mRNA was frequently associated with mutation of p53 protein, indicating that telomerase dysfunction combines with abnormal p53 function to initiate the unrestrained clonal expansion of the tumor cells. In cases in which the tumor was partially removed, mutation of p53 protein and expression of hTERT mRNA predicted increased doubling time for residual tumor as well as the probability of tumor recurrence. Cell proliferation, as investigated using the Ki-67 method, was significantly related to the tumor doubling time; however, the authors found that the pattern of cell proliferation was not homogeneous throughout the chordoma tissue, and that the proliferative index might change by a factor as high as 8 among different regions of the same tumor. The LOH and microsatellite instability do not seem to affect the prognosis of skull base chordomas.

CONCLUSIONS

Reactivation of telomerase in chordomas is a reliable predictor of outcome. The ability to predict the biological behavior of chordomas might have immediate implications in the management of this disease in patients who undergo surgery.

Analysis of telomerase activity and detection of its catalytic subunit, hTERT

The discovery of the enzyme telomerase and its subunits has led to major advances in understanding the mechanisms of cellular proliferation, immortalization, aging, and neoplastic transformation. The expression of telomerase in more than 85% of tumors provides an excellent tool for the diagnosis, prognosis, and treatment of cancer. However, the techniques employed in its detection appear to play a significant role in the interpretation of the results. The telomeric repeat amplification protocol (TRAP assay) has been the standard assay in the detection of telomerase activity and many variations of this technique have been reported. Recent advances in the development of the TRAP assay and the incorporation of techniques that provide a quantitative and qualitative estimate of telomerase activity are assessed in this review. In addition to histological and cytological examination of tissues, distribution patterns of the catalytic subunit of telomerase, hTERT, are frequently used in the prognosis of tumors. The methods involved in the detection of hTERT as a biomarker of cellular transformation are also analyzed.

Effects of N-(4-hydroxyphenyl)retinamide on hTERT expression in the bronchial epithelium of cigarette smokers

BACKGROUND

Telomerase activation plays a critical role in tumorigenesis. To determine the role of telomerase in early lung carcinogenesis and as a potential biomarker in chemoprevention trials, we analyzed the expression of the human telomerase reverse transcriptase catalytic subunit (hTERT) in bronchial biopsy specimens from cigarette smokers who were enrolled in a randomized, double-blinded, placebo-controlled chemoprevention trial of N-(4-hydroxyphenyl)retinamide (4-HPR).

METHODS

We obtained biopsy specimens from six predetermined sites in the bronchial tree from the 57 participants, before treatment and 6 months after treatment with 4-HPR or placebo. We used in situ hybridization to examine hTERT messenger RNA (mRNA) expression in 266 pretreatment (baseline) and post-treatment site-paired biopsy specimens from 27 patients in the 4-HPR-treated group and from 30 patients in the placebo-treated group. All statistical tests were two-sided.

RESULTS

At baseline, 62.4% (95% confidence interval [CI] = 53.9% to 71%) of the biopsy specimens obtained from the group treated with 4-HPR and 65.2% (95% CI = 57.4% to 73.1%) of the biopsy specimens obtained from the placebo-treated group expressed hTERT mRNA. After 6 months, 45.6% (95% CI = 36.9% to 54.3%) of the biopsy specimens obtained from the 4-HPR-treated group and 68.1% (95% CI = 60.4% to 75.8%) of the biopsy specimens obtained from the placebo-treated group expressed hTERT mRNA. The reduction in hTERT expression observed between the two treatment groups over time was statistically significant (P =.01) when we used the biopsy site as the unit of analysis, but not when we used the individual as the unit of analysis (P =.37).

CONCLUSIONS

Telomerase is frequently reactivated in the lungs of cigarette smokers. The modulation of hTERT expression in 4-HPR-treated smokers suggests that a novel molecular mechanism underlies the potential chemopreventive properties of 4-HPR. hTERT expression is a promising potential biomarker for risk assessment and for the evaluation of the efficacy of chemopreventive agents in lung carcinogenesis.