Clinical usefulness of telomerase activation and telomere length in head and neck cancer

TERT Promoter Mutations Are Enriched in Oral Cavity Cancers and Associated With Locoregional Recurrence

Telomerase reverse transcriptase (TERT) promoter mutations are prognostic in many cancers and have been observed in human papillomavirus (HPV)-negative head and neck squamous cell carcinomas (HNSCCs). However, the role of TERT promoter mutations in HPV-negative HNSCCs remains poorly understood in these cancers, which have increased risk for locoregional failure (LRF).

PATIENTS AND METHODS

We retrospectively identified patients who were diagnosed with HNSCC between July 1, 2004, and October 12, 2017, at Memorial Sloan Kettering Cancer Center and whose tumors underwent next-generation sequencing using the MSK-IMPACT panel. Patients with HPV-positive oropharyngeal squamous cell carcinoma (SCC) were excluded. Cumulative incidence of LRF, patterns of failure, and overall survival were measured.

RESULTS

We identified 117 patients with SCC of the oral cavity (OSCC), larynx, hypopharynx, or HPV-negative oropharynx whose tumors underwent next-generation sequencing. Sequencing was performed on 95 tumors that were obtained after recurrence and 22 that were obtained before recurrence. TERT promoter mutations were enriched in OSCC compared with laryngopharyngeal cancers (81.1% v 7.0%; P < .001), which was the largest genetic difference between these anatomic disease subsites. TERT promoter mutations were associated with LRF in OSCCs (Gray's test, P < .001) and in the overall cohort (Gray's test, P < .001). On multivariate analysis, TERT promoter mutations were associated with an increased risk for LRF (subdistribution hazard ratio, 2.82; 95% CI, 1.47 to 5.42; P = .0019), independent of oral cavity primary site and TP53 mutation status.

CONCLUSION

TERT promoter status is associated with the cumulative incidence of LRF and patterns of failure. TERT promoter mutations may define a subset of OSCCs with unique pathogenesis that is associated with an increased risk of LRF. Validation in prospective cohorts is warranted.

The role of m6A, m5C and Ψ RNA modifications in cancer: Novel therapeutic opportunities

RNA modifications have recently emerged as critical posttranscriptional regulators of gene expression programmes. Significant advances have been made in understanding the functional role of RNA modifications in regulating coding and non-coding RNA processing and function, which in turn thoroughly shape distinct gene expression programmes. They affect diverse biological processes, and the correct deposition of many of these modifications is required for normal development. Alterations of their deposition are implicated in several diseases, including cancer. In this Review, we focus on the occurrence of N⁶-methyladenosine (m⁶A), 5-methylcytosine (m⁵C) and pseudouridine (Ψ) in coding and non-coding RNAs and describe their physiopathological role in cancer. We will highlight the latest insights into the mechanisms of how these posttranscriptional modifications influence tumour development, maintenance, and progression. Finally, we will summarize the latest advances on the development of small molecule inhibitors that target specific writers or erasers to rewind the epitranscriptome of a cancer cell and their therapeutic potential.

Change of telomerase activity in peripheral blood of patients with head and neck squamous cell carcinoma pre and post curative treatment

BACKGROUND

There is no clinically applicable tumor marker for head and neck cancers. Telomerase is detected in approximately 90% of all malignant tumors, it may predict poor or favorable outcomes, thus being both a highly attractive biomarker and a target for the development of molecular-based cancer diagnostics, prognostics, and therapeutics.

AIM

Primary aim was to detect a change of telomerase activity before and after curative treatment.

MATERIALS AND METHODS

Patients with biopsy proven head and neck squamous cell carcinoma, stage I-IVB treated with a curative intent, performance status 0-2 and malignancy at one primary site were included in the study. Telomerase levels were tested in tissue biopsy. Plasma telomerase levels were tested at baseline, 5 days and at 3 months after treatment using ELISA.

RESULTS

Raised plasma telomerase activity was seen in all the patients with cancer at baseline. The mean plasma telomerase level at baseline was 861.4522 ng/ml, at 5 days after completion of curative treatment was 928.92 ng/ml and at 3 months of follow up was 898.87 ng/ml. The mean tissue biopsy telomerase level was 19768.53 ng/mg. There was a significant increase in baseline telomerase levels in cancer patients compared to normals (volunteers) (t = -3.52, p = 0.001).There was a significant increase in plasma levels of telomerase at 3 months compared to baseline values (z = -1.98, p = 0.04). The increase in telomerase level did not correlate with the response of the treatment.

CONCLUSION

In patients with head and neck squamous cell carcinomas treated with a curative intent, the change in levels of telomerase correlates neither with the disease status nor with prognostic factors.

Telomerase reverse transcriptase suppression inhibits cell proliferation and promotes cell apoptosis in hepatocellular cancer

We aimed to investigate the role of telomerase reverse transcriptase (TERT) in hepatocellular cancer (HCC) cells. R software was used for differential expressed gene analysis. Western blot and quantitative real time polymerase chain reaction (qRT-PCR), respectively, were used to detect protein expression and mRNA level of TERT in tumor cell lines. Real-time quantitative telomeric repeat amplification protocol assay, MTT assay, colony formation assay, and flow cytometry (FCM) assay were used to analyze the telomerase activity, viability, proliferation, cell cycle progression and apoptosis of HCC cells. The proliferation ratio of HCC cells transfected with TERT-siRNA was significantly decreased compared with control group. Plate clone results suggested that the number of colonies also decreased in TERT-siRNA group. FCM results showed that more cells were arrested in G0/G1 phase and apoptosis rate increased in TERT-siRNA group compared with control group. TERT suppression inhibited cell proliferation but promoted cell cycle arrest and cell apoptosis. © 2018 IUBMB Life, 70(7):642-648, 2018.

Clinical Significance of Telomere Length and Associated Proteins in Oral Cancer

Purpose

Telomere shortening is an important event during carcinogenesis. Although studies suggest role of multiple proteins in telomere length regulation, there is dearth of reports in oral cancer which is a leading malignancy in Asian countries especially in India. Thus the present study was carried out to study these mechanisms and explore the pathways involved in telomere—telomerase regulation and identify possible prognostic markers to understand the biology of oral tumors for better treatment approaches.

Methods

Telomere length was determined by Southern Hybridisation method, telomeric repeat binding factor (TRF) 1 and 2 expression was detected by Western blot method and telomerase activation by telomeric repeat amplification protocol. Statistical analysis was done using SPSS (Version 10) software.

Results

Significant shortening of telomeres was seen in the tumor tissues as compared to normal tissues. Poor prognosis was observed in the patients with higher telomere length in malignant tissue, higher tumor to normal telomere length ratio (T/N TRF LR). Expression of TRF-2 but not TRF-1 protein was significantly higher in the malignant tissues. We also observed telomerase activation in 75 malignant tissues.

Conclusions

Our results reveal significant clinical usefulness of telomere length, T/N TRF LR and telomerase activation in the prognosis of oral cancer patients. TRF-2 overexpression in malignant tissues appears to play an important role in telomere length shortening in oral cancer.

Telomeres and telomerase in head and neck squamous cell carcinoma: from pathogenesis to clinical implications

Strongly associated with tobacco use, heavy alcohol consumption, and with high-risk human papillomavirus (HPV) infection, head and neck squamous cell carcinoma (HNSCC) is a frequently lethal, heterogeneous disease whose pathogenesis is a multistep and multifactorial process involving genetic and epigenetic events. The majority of HNSCC patients present with locoregional advanced stage disease and are treated with combined modality strategies that can markedly impair quality of life and elicit unpredictable results. A large fraction of those who undergo locoregional treatment and achieve a complete response later develop locoregional recurrences or second field tumors. Biomarkers that are thus able to stratify risk and enable clinicians to tailor treatment plans and to personalize post-therapeutic surveillance strategies are highly desirable. To date, only HPV status is considered a reliable independent predictor of treatment response and survival in patients with HNSCC arising from the oropharyngeal site. Recent studies suggest that telomere attrition, which may be an early event in human carcinogenesis, and telomerase activation, which is detected in up to 90 % of malignancies, could be potential markers of cancer risk and disease outcome. This review examines the current state of knowledge on and discusses the implications linked to telomere dysfunction and telomerase activation in the development and clinical outcome of HNSCC.

Quantification of telomerase activity in normal oral mucosal tissue and oral squamous cell carcinoma

BACKGROUND AND OBJECTIVE

The role of telomeres and telomerase in oral cancer is an area of much recent interest. The understanding of the role of telomere biology, the end replication problem leading to genomic instability and the reactivation of telomerase, is absolutely critical to our understanding of oral cancer, and more so, to our ability of early diagnosis and developing novel therapies and cancer prevention approaches. The aim of the present study was to quantify telomerase activity (TA) in oral squamous cell carcinoma (OSCC) and normal oral mucosa and assess the role of telomerase as diagnostic and prognostic marker of oral malignancy.

MATERIALS AND METHODS

We quantified TA in 45 patients with OSCC and 20 normal oral mucosal specimens using polymerase chain reaction-based telomeric repeat amplification protocol assay and compared it with the clinical status and grade of malignancy.

RESULTS

TA was detected in 89% of malignant and 5% of normal oral mucosal tissue. The TA levels ranged from 0.28 to 6.91 (mean 2.05, standard deviation [SD] 1.33) in OSCC and 0.21 to 1.09 (mean 0.54, SD 0.27) in normal oral mucosa. There was no relationship between TA levels and clinical stages, site of the lesion, history of adverse habits, or sex of the patient. However, under the WHO classification, there were significant differences (P < 0.00) between Grades I, II, and III. Furthermore, increasing age of the patient significantly correlated with TA.

INTERPRETATION AND CONCLUSION

The results of the present study indicate that activation of TA is frequent in OSCC. Statistically significant difference in quantified telomerase levels of OSCC and normal oral mucosa (P < 0.00) demonstrates the significant clinical usefulness of telomerase activation as a valuable marker for diagnosis while significant correlation of TA with grades of malignancy indicates its effectiveness as marker for prognosis of OSCC.

Association between telomere length and survival in cancer patients: a meta-analysis and review of literature

The relationship between telomere length and cancer survival has been widely studied. To gain a deeper insight, we reviewed the published studies. A total of 29 studies evaluated telomere length in the peripheral blood; 22 studies evaluated telomere length in the tumor tissue. First, in the peripheral blood studies, for solid tumor patients with shortened telomere length, the combined hazard ratios (HRs) for mortality and tumor progression were 1.21 (95%CI, 1.10-1.32) and 1.71 (95%CI, 1.37-2.13), respectively. Meanwhile, in hematology malignancy, the combined HRs for mortality and tumor progression were 2.83 (95%CI, 2.14-3.74) and 2.65 (95%CI, 2.18-3.22), respectively. Second, in the studies that use tumor tissue, for patients with shortened telomeres, the combined HRs for mortality and tumor progression were 1.26 (95%CI, 0.95-1.66) and 1.65 (95%CI, 1.26-2.15), respectively. In the studies that calculate the telomere length ratios of tumor tissue to adjacent normal mucosa, for patients with lower telomere length ratios, the combined HRs were 0.66 (95%CI, 0.53-0.83) and 0.74 (95%CI, 0.41-1.32) for mortality and tumor progression, respectively. In conclusion, shortened telomere in peripheral blood and tumor tissue might indicate poor survival for cancer patients. However, by calculating the telomere length ratios of tumor tissue to adjacent normal mucosa, the lower ratio might indicate better survival.

Telomere length, genetic variants and risk of squamous cell carcinoma of the head and neck in Southeast Chinese

Telomere dysfunction participates in malignant transformation and tumorigenesis. Previous studies have explored the associations between telomere length (TL) and cancer susceptibility; however, the findings are inconclusive. The associations between genetic variants and TL have been verified by quite a few genome-wide association studies (GWAS). Yet, to date, there was no published study on the relationship between TL, related genetic variants and susceptibility to squamous cell carcinoma of the head and neck (SCCHN) in Chinese. Hence, we detected relative telomere length (RTL) by using quantitative PCR and genotyped seven selected single nucleotide polymorphisms by TaqMan allelic discrimination assay in 510 SCCHN cases and 913 controls in southeast Chinese. The results showed that RTL was significantly associated with SCCHN risk [(adjusted odds ratio (OR) = 1.19, 95% confidence interval (CI) = 1.08–1.32, P = 0.001]. Furthermore, among seven selected SNPs, only G allele of rs2736100 related to RTL in Caucasians was significantly associated with both the decreased RTL (P = 0.002) and the increased susceptibility to SCCHN in Chinese (additive model: adjusted OR = 1.17, 95%CI = 1.00–1.38, P = 0.049). These findings provide evidence that shortened TL is a risk factor for SCCHN, and genetic variants can contribute to both TL and the susceptibility to SCCHN in southeast Chinese population.

miR-512-5p suppresses tumor growth by targeting hTERT in telomerase positive head and neck squamous cell carcinoma in vitro and in vivo

Telomerase activation has very important implications for head and neck squamous cell carcinoma (HNSCC), but the regulatory mechanisms of telomerase in HNSCC remain unclear. In our present study, we found that miR-512-5P was markedly downregulated in telomerase-positive HNSCC cell lines. Both in vitro and in vivo assays revealed that miR-512-5P mimic attenuated HNSCC cell proliferation, and tumor growth in nude mice, which exerts its tumor suppressor function through elevated apoptosis, inhibition of the telomerase activity, decrease of telomere-binding proteins and shortening of telomere length by human telomerase reverse transcriptase (hTERT) downregulation. Furthermore, the dual-luciferase reporter gene assay results demonstrated that hTERT was a direct target of miR-512-5P. We conclude that the frequently miR-512-5P overexpression can regulate hTERT and function as a tumor suppressor in HNSCC. Therefore, miR-512-5P may serve as a potential therapeutic agent for miR-based HNSCC therapy.

Telomere shortening in mucosa surrounding the tumor: biosensor of field cancerization and prognostic marker of mucosal failure in head and neck squamous cell carcinoma

OBJECTIVES

The aim of the present study was to investigate the pattern of telomere length and telomerase expression in cancer tissues and the surrounding mucosa (SM), as markers of field cancerization and clinical outcome in patients successfully treated for with head and neck squamous cell carcinoma (HNSCC).

MATERIALS AND METHODS

This investigation was a prospective cohort study. Telomere length and levels of telomerase reverse transcriptase (TERT) transcripts were quantified by real-time PCR in cancer tissues and SM from 139 and 90 patients with HNSCC, respectively.

RESULTS

No correlation was found between age and telomere length in SM. Patients with short telomeres in SM had a higher risk of mucosal failure (adjusted HR=4.29). Patients with high TERT levels in cancer tissues had a higher risk of regional failure (HR=2.88), distant failure (HR=7.27), worse disease-specific survival (HR for related death=2.62) but not mucosal failure. High-risk patients having both short telomeres in SM and high levels of TERT in cancer showed a significantly lower overall survival (HR=2.46).

CONCLUSIONS

Overall these findings suggest that telomere shortening in SM is a marker of field cancerization and may precede reactivation of TERT. Short telomeres in SM are strongly prognostic of mucosal failure, whereas TERT levels in cancer tissues increase with the aggressiveness of the disease and are prognostic of tumor spread.

Predicting clinical outcome in feline oral squamous cell carcinoma: tumour initiating cells, telomeres and telomerase

Feline oral squamous cell carcinoma (SCC) has very poor prognosis. Here, a retrospective pilot study was conducted on 20 feline oral SCC patients who underwent stereotactic radiation therapy (SRT), to evaluate: (1) the value of putative tumour initiating cell (TIC) markers of human head and neck SCC (CD44, Bmi-1); (2) telomere length (TL) specifically in putative TICs; and (3) tumour relative telomerase activity (TA). Significant inverse correlations were found between treatment outcomes and Bmi-1 expression, supporting the predictive value of Bmi-1 as a negative prognostic indicator. While TL exhibited a wide range of variability, particularly in very short fractions, many tumours possessed high levels of TA, which correlated with high levels of Bmi-1, Ki67 and EGFR. Taken together, our results imply that Bmi-1 and telomerase may represent novel therapeutic targets in feline oral SCC, as their inhibition - in combination with SRT - would be expected to have beneficial treatment outcome.

Telomere length, TERT and shelterin complex proteins in hepatocellular carcinomas expressing "stemness"-related markers

BACKGROUND & AIMS

Hepatocellular carcinomas (HCCs) expressing "stemness"-related markers have been associated with aggressive biological behavior and poor prognosis. We examined the relationship between "stemness"-related protein expression and telomere length, hTERT and shelterin complex protein expression and chromosomal instability.

METHODS

Quantitative fluorescent in situ hybridization for telomere length, immunohistochemistry for K19, EpCAM, CD133, c-kit, HepPar1, hTERT, TRF1, TRF2, POT1, RAP1 and TPP1, and TUNEL assay were performed in 137 HCCs, and array comparative genomic hybridization was performed with 24 HCCs.

RESULTS

Telomeres were significantly longer in HCCs expressing "stemness"-related proteins (K19: p < 0.001, EpCAM: p = 0.002, CD133: p = 0.002). On analyzing different tumor cells within EpCAM-expressing HCCs, EpCAM-positive tumor cells showed longer telomeres (1.329 ± 0.246) compared to EpCAM-negative tumor cells (0.996 ± 0.381) within the same HCCs (p = 0.031). Telomeres were significantly longer in HCCs expressing hTERT (p = 0.048) and RAP1 proteins (p = 0.031). K19-expressing HCCs expressed hTERT (p = 0.002), TRF2 (p = 0.001) and TPP1 (p = 0.013) more frequently compared to K19-negative HCCs. EpCAM-positivity was associated with more frequent hTERT (p = 0.028), TPP1 (p = 0.017), TRF2 (p = 0.027) and POT1 (p = 0.004) expression. Copy number alterations were more frequent in K19 and EpCAM-expressing HCCs compared to HCCs without these markers (K19: p = 0.038, EpCAM: p = 0.009). HCCs with longer telomeres were associated with a shorter overall (p = 0.019) and disease-free survivals (p = 0.049), and decreased disease-free survivals were seen in TRF2-positive HCCs (p = 0.018).

CONCLUSIONS

HCCs expressing "stemness"-related proteins are characterized by increased telomere length, increased expression of hTERT and shelterin complex proteins, and increased chromosomal instability compared to conventional HCCs. Longer telomeres and TRF2 expression in HCCs are associated with poor patient outcomes.

Telomere length modulation in human astroglial brain tumors

Background

Telomeres alteration during carcinogenesis and tumor progression has been described in several cancer types. Telomeres length is stabilized by telomerase (h-TERT) and controlled by several proteins that protect telomere integrity, such as the Telomere Repeat-binding Factor (TRF) 1 and 2 and the tankyrase-poli-ADP-ribose polymerase (TANKs-PARP) complex.

Objective

To investigate telomere dysfunction in astroglial brain tumors we analyzed telomeres length, telomerase activity and the expression of a panel of genes controlling the length and structure of telomeres in tissue samples obtained in vivo from astroglial brain tumors with different grade of malignancy.

Materials and Methods

Eight Low Grade Astrocytomas (LGA), 11 Anaplastic Astrocytomas (AA) and 11 Glioblastoma Multiforme (GBM) samples were analyzed. Three samples of normal brain tissue (NBT) were used as controls. Telomeres length was assessed through Southern Blotting. Telomerase activity was evaluated by a telomere repeat amplification protocol (TRAP) assay. The expression levels of TRF1, TRF2, h-TERT and TANKs-PARP complex were determined through Immunoblotting and RT-PCR.

Results

LGA were featured by an up-regulation of TRF1 and 2 and by shorter telomeres. Conversely, AA and GBM were featured by a down-regulation of TRF1 and 2 and an up-regulation of both telomerase and TANKs-PARP complex.

Conclusions

In human astroglial brain tumours, up-regulation of TRF1 and TRF2 occurs in the early stages of carcinogenesis determining telomeres shortening and genomic instability. In a later stage, up-regulation of PARP-TANKs and telomerase activation may occur together with an ADP-ribosylation of TRF1, causing a reduced ability to bind telomeric DNA, telomeres elongation and tumor malignant progression.

Molecular and cellular processes underlying the hallmarks of head and neck cancer

The hallmarks of cancer were updated by Hanahan and Weinberg in 2011. Here we discuss the updated hallmarks in relation to what is known of the molecular and cellular processes underlying the development of head and neck squamous cell carcinoma (HNSCC). Several mechanisms are described, and recent surveys of HNSCC suggest a limited number of mutations, from which more mechanisms may emerge. There are also epigenetic changes to the control of normal processes. More than one mechanism underlies each hallmark. Processes essential to the development of HNSCC need not be essential to the proliferation of the fully developed tumour. Attention is paid to the emerging hallmarks, deregulation of cellular energy metabolism and evasion of immune destruction, and enabling characteristics, genome instability and mutation and tumour-promoting inflammation. HNSCC may adapt to hypoxia, suppress HLA expression, and express Toll-like receptors to facilitate inflammation, which support the proliferation of the tumour.

Molecular changes in the multistage pathogenesis of head and neck cancer

Head and neck squamous cell carcinomas (SCCHN) arise in the mucosa of the upper aerodigestive tract at multiple anatomic sites. While tobacco and alcohol exposure remain the primary risk factors for this malignancy, infection with the human papilloma virus is emerging as a major contributing factor to cancers that arise primarily in the oropharynx. Despite therapeutic advances, survival has remained relatively unchanged over the past few decades. Increased understand of the cellular and molecular biology of these cancers will improve our understanding of this malignancy and facilitate the development of more effective therapeutic strategies. Alterations that have been studied to date include genetic and epigenetic changes. While the epidermal growth factor receptor (EGFR) is the only established molecular therapeutic target, other proteins and pathways are under active investigation to determine their contribution to SCCHN carcinogenesis and progression.

Change of telomerase activity in peripheral whole blood of head and neck squamous cell carcinoma patients before and after surgery: a pilot study

BACKGROUND The purpose of this study was to evaluate telomerase activity in peripheral whole blood from head and neck squamous cell carcinoma (HNSCC) patients as a biomarker for diagnosis of HNSCC or detection of recurrence during follow-up. MATERIALS AND METHODS Telomerase activity was measured from peripheral whole blood extracts by telomerase repeat amplification protocol (TRAP) in HNSCC patients before and after surgery and in a control group. Sixty-two HNSCC patients and 42 control subjects were included. RESULTS Telomerase activity was found in 41 out of 62 (66.1%) HNSCC patients before surgery and in 8 out of 42 (19.0%) controls (p<0.001). Among 41 HNSCC patients who showed positive telomerase activity before surgery, 32 (78.1%) showed a conversion of telomerase activity to negative after surgery. In follow-up, 6 out of 8 (75%) showed conversion of telomerase activity from negative to positive after recurrence. Telomerase activity was changed to negative in 4 out of 6 (66%) recurred patients with positive telomerase activity after second surgery. CONCLUSION The telomerase activity in peripheral whole blood extracts of HNSCC patients might be a useful biomarker for detecting recurrence after treatment. Further study with larger sample size using a more sensitive detection method of telomerase activity is necessary to verify these results.

Alterations of telomere length in human brain tumors

Telomeres at the ends of human chromosomes consist of tandem hexametric (TTAGGG)n repeats, which protect them from degradation. At each cycle of cell division, most normal somatic cells lose approximately 50-100 bp of the terminal telomeric repeat DNA. Precise prediction of growth and estimation of the malignant potential of brain tumors require additional markers. DNA extraction was performed from the 51 frozen tissues, and a non-radioactive chemiluminescent assay was used for Southern blotting. One sample t-test shows highly significant difference in telomere length in meningioma and astrocytoma with normal range. According to our results, higher grades of meningioma and astrocytoma tumors show more heterogeneity in telomere length, and also it seems shortening process of telomeres is an early event in brain tumors.

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 dysfunction promotes metastasis in a TERC null mouse model of head and neck cancer

Squamous cell carcinoma arises from highly proliferative basal layer epithelial cells, which normally divide for a short time before detaching from the basement membrane and undergoing terminal differentiation. Basal layer cells in stratified epithelia express the reverse transcriptase known as telomerase. Most human cells do not express telomerase and therefore are subject to loss of telomeric DNA with age due to the inability of lagging strand synthesis to completely replicate chromosomal ends. Late generation telomerase deficient mice exhibit signs of premature aging including reduced function of proliferating cellular compartments. We examined development of squamous cell carcinoma in a telomerase deficient murine background with long and short telomeres. G1 Terc-/- mice (long telomeres) had fewer lymph node metastases, which correlated with increased numbers of apoptotic cells in these tumors compared with wild-type mice. However, G5 Terc-/- mice with short telomeres had increased metastatic tumor burden similar to wild type mice. This increased metastasis correlated with genomic instability and aneuploidy in tumor cells from G5 Terc-/- mice. A number of similarities with human SCC were noted in the mouse model, and dramatic differences in global gene expression profiles were shown between primary and metastatic tumors. We concluded that telomere shortening promotes metastatic tumor development in a Terc null mouse model of head and neck cancer.

Telomeres and telomerase in normal and malignant B-cells

The telomeric checkpoint is emerging as a critical sensor of cellular damage, playing a major role in human aging and cancer development. In the meantime, telomere biology is rapidly evolving from a basic discipline to a translational branch, capable of providing major hints for biomarker development, risk assessment and targeted treatment of cancer. These advances have a number of implications in the biology of lymphoid tumours. Moreover, there is considerable interest in the potential role of telomeric dysfunction in the wide array of immunological abnormalities, grouped under the definition of 'immunosenescence'. This review will summarize the impact of recent advances in telomere biology on the physiology and pathology of the B lymphocyte, with special interest in immunosenescence and lymphomagenesis.

Correlation of dyskerin expression with active proliferation independent of telomerase

BACKGROUND

Dyskerin, which is an important component of the telomerase complex and is needed for normal telomerase activity, is frequently overexpressed in neoplasia. Dyskerin also plays an essential role in ribosome biogenesis. Because protein synthesis increases during tumorigenesis, this led us to hypothesize that dyskerin expression would be upregulated independently of the cell immortalization mechanism.

METHODS

Dyskerin and telomerase reverse transcriptase (TERT) expression were examined in oral squamous cell carcinomas (OSCC) and patient-matched controls, as well as in a panel of telomerase-positive and telomerase-negative cells. Antisense inhibition of TERT was used to test the effects of downregulation of telomerase on dyskerin expression.

RESULTS

Dyskerin was frequently overexpressed in OSCC and in immortalized and transformed keratinocytes relative to primary cells, independently of TERT and telomerase activity. Instead, dyskerin expression strongly correlated with cell proliferation rates.

CONCLUSIONS

The role of dyskerin in tumorigenesis does not correlate with its function within the telomerase complex.

Telomere length as a biological marker in malignancy

Telomere maintenance is important for tumor cell growth and survival. Telomere length (TL) is determined by the balance between positive and negative factors impacting telomere homeostasis. In the last decade, TL has emerged as a promising clinical marker for risk and prognosis prediction in patients with malignant disorders. Tumor TL, as well as TL in healthy tissues such as peripheral blood, may carry valuable information for future treatment strategies. Here we discuss the present status of TL as a biological marker in cancer patients.

Effects of telomerase activity on carcinogenesis and survival in laryngeal carcinoma

This study aimed to look at whether a correlation exists between telomerase activity and survival of laryngeal carcinoma patients. Telomerase activity was measured by telomerase repeat amplification protocol in 31 laryngeal carcinomas and adjacent normal tissues, and in 21 vocal cord polyps (controls). Follow-up was for at least 60 months. Telomerase activity in tissues adjacent to laryngeal carcinomas was significantly higher than in the carcinomas which was, in turn, significantly higher than in vocal cord polyps. There was no significant difference between telomerase activity in carcinomas or adjacent tissues and clinicopathological characteristics. Patients with high telomerase activity in carcinoma tissue had significantly shorter survival times than those with low activity, but no significance difference was observed between survival time and telomerase status in adjacent tissues. Linear regression showed significant association between telomerase activity levels in carcinoma tissues and survival time, but this was not observed in adjacent tissues. This study suggests that telomerase activation probably takes place before the cancer phenotype develops and has prognostic significance for survival of patients with laryngeal carcinoma.

Telomeric 3' overhangs in chronic HBV-related hepatitis and hepatocellular carcinoma

Telomeric 3' overhang is a key component of telomere structure, but little is known about its role in hepatocarcinogenesis. We examined the 3' overhang and telomere length, mRNA levels of hTERT, POT1, TRF1 and cytokeratin 19 (CK19) in 41 hepatitis B virus (HBV)-related hepatocellular carcinomas (HCCs) and adjacent non-HCCs of B viral chronic hepatitis/cirrhosis. 3' overhang length was positively correlated with telomere length (p < 0.001). In non-HCCs, the 3' overhang shortened with increasing age (p = 0.043). Twenty-six HCCs had shorter and 15 HCCs had longer 3' overhangs than the adjacent non-HCCs. The mRNA levels of hTERT, POT1 and TRF1 were upregulated in HCCs than in non-HCCs. HCCs with lengthened 3' overhangs expressed higher hTERT mRNA levels than those with shortened 3' overhangs, when compared to 3' overhangs in non-HCCs (p = 0.044). POT1 and TRF1 showed no significant difference according to the 3' overhangs. HCCs with long 3' overhangs had higher mitosis (p = 0.046) and more frequent multipolar mitosis compared to those with short 3' overhangs (p = 0.034). HCCs with high cytokeratin 19 mRNA levels, a marker for hepatic progenitor cells, had longer 3' overhangs than HCCs with low cytokeratin 19 mRNA levels (p= 0.019). In conclusion, the 3' overhang erosion might be closely related to the number of cell divisions in telomerase-negative hepatocytes of chronic hepatitis/cirrhosis. In telomerase-positive HCCs, an altered 3' overhang are involved in HBV-related hepatocarcinogenesis and hTERT might be involved in regulation of 3' overhang.

Gene therapy in head and neck cancer: a review

Gene therapy for cancer is a rapidly evolving field with head and neck squamous cell cancer being one of the more frequently targeted cancer types. The number of clinical trials in the UK is growing and there is already a commercially available agent in China. Various gene therapy strategies along with delivery mechanisms for targeting head and neck cancer are reviewed.

High telomerase activity and long telomeres in advanced hepatocellular carcinomas with poor prognosis

Telomerase reactivation and telomere maintenance are crucial in carcinogenesis and tumor progression. In this study, the relationships between telomere parameters, chromosomal instability and clinicopathological features were evaluated in hepatocellular carcinomas (HCCs). Telomere length (TL), telomerase activity (TA) and human telomerase reverse transcriptase (hTERT) mRNA levels were measured in 49 hepatitis B virus (HBV)-related HCCs and corresponding non-tumorous tissues. The results were compared with clinicopathological data, including differentiation, multipolar mitosis (MM), anaphase bridge, immunohistochemical stain results for cytokeratin 19 (CK19) and patient outcome. TL of HCCs ranged from 4.7 to 13.1 kb, and 44.4% of HCCs showed telomere lengthening. hTERT mRNA levels and TA were closely related (P=0.008), and were significantly higher in HCCs than non-tumorous tissues. TL was significantly higher in HCCs with strong TA (P=0.048), high hTERT mRNA levels (P=0.001) and poor differentiation (P=0.041). Frequent MM was associated with poor differentiation (P=0.007) and advanced stage (P<0.001). TA was positively correlated with MM, anaphase bridges and advanced stage (P=0.019, P=0.017 and P=0.029). Thirteen (28.3%) HCCs were CK19+ and demonstrated longer telomeres than CK19- HCCs (P=0.046). Overall survival was poor in HCCs with MM >0.4 per field (P=0.016), high TA (P=0.009) and high TL ratio (HCC/non-HCC) >0.8 (P=0.044). Our results show that long telomeres, high TA and high mitotic instability are poor prognostic markers for HBV-related HCCs and their close association suggests that telomere maintenance may be important for the progression of HCCs with high chromosomal instability to more aggressive ones.

Short telomeres: a novel potential predictor of relapse in Ewing sarcoma

PURPOSE

Despite advances in therapy, >50% of patients with Ewing sarcoma will relapse. The current prognostic factors are not optimal for risk prediction. Studies have shown that telomere length could predict outcome in different malignancies. Our aim was to evaluate whether telomere length could be a better prognostic factor in Ewing sarcoma and correlate the results with clinical variables, outcome, and chromosomal instability.

EXPERIMENTAL DESIGN

Telomere length was determined in the primary tumor and peripheral blood of 32 patients with Ewing sarcoma. Chromosomal instability was evaluated by combining classical cytogenetics, comparative genomic hybridization and random aneuploidy. Telomere length was correlated to clinical variables, chromosomal instability, and outcome.

RESULTS

In 75% of the tumors, changes in telomere length, when compared with the corresponding peripheral blood lymphocytes, were noted. The majority of changes consisted of a reduction in telomere length. Patients harboring shorter telomeres had a significantly adverse outcome (P = 0.015). Chromosomal instability was identified in 65% of tumors, significantly correlating with short telomeres (P = 0.0094). Using multivariate analysis, telomere length remained the only significant prognostic variable (P = 0.034). Patients with short telomeres had a 5.3-fold risk of relapse as compared to those with unchanged or longer telomeres.

CONCLUSION

We have shown that tumors with telomere length reduction result in genomic instability. In addition, telomere length reduction was the only significant predictor of outcome. We suggest that reduction of telomere length in tumor cells at diagnosis could serve as a prognostic marker in Ewing sarcoma.

Clinical relevance of ceramide metabolism in the pathogenesis of human head and neck squamous cell carcinoma (HNSCC): attenuation of C(18)-ceramide in HNSCC tumors correlates with lymphovascular invasion and nodal metastasis

It has been documented previously that defects in the generation of C(18)-ceramide, a product of ceramide synthase 1 (CerS1), also known as longevity assurance gene 1 (hLASS1), play important roles in the pathogenesis and/or progression of HNSCC. However, whether altered levels of ceramide generation in HNSCC tumors have any clinical relevance remains unknown. In this study, the levels of endogenous ceramides were measured in tumor tissues of 45 HNSCC patients as compared to their normal tissues using high-pressure liquid chromatography/mass spectrometry (LC/MS), and then possible link between ceramide levels and the clinical parameters of HNSCC were examined. The data showed that the levels of C(16)-, C(24)-, C(24:1)-ceramides were significantly elevated in the majority of tumor tissues compared to their normal tissues, while the levels of only C(18)-ceramide were significantly decreased in HNSCC tumors, especially in tumor tissues of male patients. Importantly, it was also shown here that decreased C(18)-ceramide levels in HNSCC tumor tissues were significantly associated with the higher incidences of lymphovascular invasion, and pathologic nodal metastasis. Importantly, attenuation of C(18)-ceramide was also positively linked to the higher overall stages of the primary HNSCC tumors. Therefore, these data suggest, for the first time, that the defects in the generation/accumulation of C(18)-ceramide might have important clinical roles in HNSCC, especially in lymphovascular invasion and nodal disease.

Telomeres: prognostic markers for solid tumors

Solid tumors continue to affect millions of people worldwide. Increasingly sophisticated diagnostic tools contribute to the high incidence rates for some tumor types, and treatment options continue to expand. However, the progression of solid tumors represents a challenge for the appropriate treatment of individual patients because of the relative inaccuracy of current prognostic markers, including the widely used Tumor-Nodes-Metastasis (TNM) staging system, to predict the course of disease. As a result, both over- and undertreatment are clinical realities in the management of patients diagnosed with solid tumors. Therefore, population-based screening programs that increase the overall cancer incidence rates are controversial, as they may do little to improve the patient's quality of life. Consequently, there is a strong need to develop novel and independent markers of prognosis. In this context, we review the use of telomeres as prognostic markers for solid tumors, including cancers from lung, breast, prostate, colon, brain and head and neck. Telomeric sequences, the repetitive DNA at the end of human chromosomes, are mediators of genomic stability and can undergo length alterations during tumor initiation and progression. In a number of studies reviewed here, these alterations, measured as telomere attrition and elongation, have been shown either to be associated with clinical markers of disease progression or to be independent markers of cancer prognosis. We conclude from these studies that careful assessment of telomere length or its proxies, such as telomere DNA content, will be part of novel risk assessment and prognostic modalities for patients with solid tumors.

The prognostic value of telomerase expression in peripheral blood mononuclear cells of head and neck cancer patients

OBJECTIVE

This study investigates the expression of telomerase in the peripheral blood mononuclear cells (PBMCs) of head and neck cancer patients and the relationship between the telomerase expression in PBMCs and clinicopathological features with prognosis.

METHODS

Peripheral blood samples were collected from 100 head and neck squamous cell cancer patients and 20 normal control group. The telomerase activity in peripheral blood mononuclear cells was measured by telomerase rapid amplification protocol (TRAP) assay using TRAPeze telomerase detection kit. Pearson chi test was used to analyze the correlation of telomerase expression with clinicopathologic parameters. Kaplan-Meier method and Cox proportional hazards model were used for prognostic analysis.

RESULTS

Regarding the expression of telomerase in PBMCs of patients, 73 out of 100 (73.0%) were found to be positive, and the remaining 27 cases (27.0%) were negative. The difference to the telomerase expression of PBMCs in the normal and cancer patients was significant (P < 0.001). The expression of telomerase in PBMCs of patients was significant correlated with T classification (P = 0.005), N classification (P = 0.002), and AJCC stages (P < 0.001). On multivariate analysis, N classification (P = 0.007), AJCC stages (P = 0.02), and telomerase expression (P = 0.017) showed independent factors associated with poor survival.

CONCLUSION

The detection of telomerase expression in PBMCs of head and neck cancer patients is a simple and very useful molecular marker for the progression and prognosis of head and neck cancer.

Correlations of telomere length, telomerase activity, and telomeric-repeat binding factor 1 expression in colorectal carcinoma

BACKGROUND

Telomere maintenance has been proposed as an essential step for tumor cell immortalization. The objectives of the current study were to investigate the mechanisms implicated in telomere length in colorectal carcinoma (CRC) and to evaluate the prognostic impact of telomere status.

METHODS

Ninety-one colorectal carcinoma samples that were obtained from patients who underwent surgery were analyzed to investigate the factors related to telomere function. The authors studied telomerase activity, terminal restriction fragment (TRF) length, and telomeric-repeat binding factor (TRF1) expression and analyzed the prognostic implications of those factors.

RESULTS

Most tumors (81.3%) displayed telomerase activity. Overall, telomeres in CRC specimens were significantly shorter compared with telomeres in normal, adjacent specimens (P=0.02). Moreover, tumors that demonstrated shortened telomeres displayed higher TRF1 levels than tumors without telomere shortening. In relation to patient prognosis, a significantly poor clinical course was observed in the group of patients who had tumors with longer telomeres (P=0.02), and this finding emerged as an independent prognostic factor in a Cox proportional hazards model (P=0.04; relative risk, 6.48). Among patients with tumors classified as telomerase-positive, telomere length ratios (the ratio of tumor tissues to normal tissues)<or=0.66 or TRF1 over-expression conferred a favorable outcome (P=0.03 and P=0.05, respectively).

CONCLUSIONS

The majority of CRC specimens in the current study displayed telomerase reactivation. However, only those tumors that displayed telomere elongation conferred a poor prognosis. Conversely, colorectal tumors that over-expressed TRF1 demonstrated telomere shortening, and patients with those tumors had a better clinical course.

Potent antitumor activity of a novel cationic pyridinium-ceramide alone or in combination with gemcitabine against human head and neck squamous cell carcinomas in vitro and in vivo

In this study, a cationic water-soluble ceramide analog L-threo-C6-pyridinium-ceramide-bromide (L-t-C6-Pyr-Cer), which exhibits high solubility and bioavailability, inhibited the growth of various human head and neck squamous cell carcinoma (HNSCC) cell lines at low IC50 concentrations, independent of their p53 status. Consistent with its design to target negatively charged intracellular compartments, L-t-C6-Pyr-Cer accumulated mainly in mitochondria-, and nuclei-enriched fractions upon treatment of human UM-SCC-22A cells [human squamous cell carcinoma (SCC) of the hypopharynx] at 1 to 6 h. In addition to its growth-inhibitory function as a single agent, the supra-additive interaction of L-t-C6-Pyr-Cer with gemcitabine (GMZ), a chemotherapeutic agent used in HNSCC, was determined using isobologram studies. Then, the effects of this ceramide, alone or in combination with GMZ, on the growth of UM-SCC-22A xenografts in SCID mice was assessed following the determination of preclinical parameters, such as maximum tolerated dose, clearance from the blood, and bioaccumulation. Results demonstrated that treatment with L-t-C6-Pyr-Cer in combination with GMZ significantly prevented the growth of HNSCC tumors in vivo. The therapeutic efficacy of L-t-C6-Pyr-Cer/GMZ combination against HNSCC tumors was approximately 2.5-fold better than that of the combination of 5-fluorouracil/cis-platin. In addition, liquid chromatography/mass spectroscopy analysis showed that the levels of L-t-C6-Pyr-Cer in HNSCC tumors were significantly higher than its levels in the liver and intestines; interestingly, the combination with GMZ increased the sustained accumulation of this ceramide by approximately 40%. Moreover, treatment with L-t-C6-Pyr-Cer/GMZ combination resulted in a significant inhibition of telomerase activity and decrease in telomere length in vivo, which are among downstream targets of ceramide.

New molecular diagnostic methods in head and neck cancer

Initial cancer evaluation includes assessment of histologic appearance, tumor grading, assessment of lymph node status, and presence of metastasis. However, traditional diagnostic methods such as histopathology and radiology are not sensitive enough to detect small numbers of cancer cells and are limited in their ability to predict response to treatment. Recently, there has been considerable progress in molecular diagnostics in these areas. Using molecular-based technologies, it is now possible to detect cancer early in asymptomatic individuals, identify minimal residual disease at histopathologic normal surgical margins, more precisely assess tumor burden in cancer patients, and more accurately assess the prognosis of the patients. Examples of these applications in the evaluation of head and neck cancer are reviewed here. However, despite the great promise of these new molecular approaches for cancer detection, much of the current technology limits their implementation into routine clinical use.

Telomerase as an independent prognostic factor in head and neck squamous cell carcinoma

BACKGROUND

Telomerase activity has been found to be associated with many cancers, including head and neck squamous cell carcinoma (HNSCC). We examined the association of telomerase activity with the clinical outcome of patients with HNSCC.

METHODS

A PCR-based enzyme immunoassay method was used to measure telomerase activity in 217 matched (grossly normal and cancerous) tissues from patients with HNSCC. Pearson chi-square test was used to analyze the correlation of telomerase activity with clinicopathologic parameters. Kaplan-Meier method and Cox logistic regression model were used for prognostic analysis.

RESULTS

Of the 217 tissues assayed, 4.1% of the normal and 63.3% of the cancer tissues had high levels of telomerase activity. Telomerase activity was shown to be statistically correlated with extracapsule spreading (ECS) of lymph nodes (p =.005) and overall survival (p =.003). On multivariant analysis, overall stage (p =.007), tumor depth (p =.045), and telomerase activity (p =.008) showed independent variables associated with poor survival.

CONCLUSIONS

Telomerase activity has been shown to be an independent prognostic factor for survival in cases of HNSCC. Telomerase may be a potential molecular target for clinical use in prognostication and therapy in cases of the disease.

Defects in Cell Growth Regulation by C18:0-Ceramide and Longevity Assurance Gene 1 in Human Head and Neck Squamous Cell Carcinomas

In this study, endogenous long chain ceramides were measured in 32 human head and neck squamous cell carcinoma (HNSCC) and 10 nonsquamous head and neck carcinoma tumor tissues, as compared with adjacent noncancerous tissues, by liquid chromatography/mass spectroscopy. Interestingly, only one specific ceramide, C(18:0)-ceramide, was selectively down-regulated in the majority of HNSCC tumor tissues. On the other hand, in nonsquamous tumor tissues, this selectivity for C18-ceramide was not detected. These data suggested the hypotheses that decreased levels of C18-ceramide might impart a growth advantage to HNSCC cells and that increased generation of C18-ceramide may be involved in the inhibition of growth. These roles were examined by reconstitution of C18-ceramide at physiologically relevant concentrations in UM-SCC-22A cells (squamous cell carcinoma of hypopharynx) via overexpression of mammalian upstream regulator of growth and differentiation factor 1 (mUOG1), a mouse homologue of longevity assurance gene 1 (mLAG1), which has been shown to specifically induce the generation of C18-ceramide. Liquid chromatography/mass spectroscopy analysis showed that overexpression of the mLAG1/mUOG1 resulted in increased levels of only C(18:0)-ceramide by approximately 2-fold, i.e. concentrations similar to those of normal head and neck tissues. Importantly, increased generation of C18-ceramide by mLAG1/mUOG1 inhibited cell growth (approximately 70-80%), which mechanistically involved the modulation of telomerase activity and induction of apoptotic cell death by mitochondrial dysfunction. In conclusion, this study demonstrates, for the first time, a biological role for LAG1 and C18-ceramide in the regulation of growth of HNSCC.