Telomerase activity in Papanicolaou smear-negative exfoliated cervical cells and its association with lesions and oncogenic human papillomaviruses

Evidence for enhanced telomerase activity in Barrett's esophagus with dysplasia and adenocarcinoma

BACKGROUND

Dysplasia and adenocarcinoma developing in Barrett's esophagus (BE) are not always endoscopically identifiable. Molecular markers are needed for early recognition of these focal lesions and to identify patients at increased risk of developing adenocarcinoma. The aim of the current study was to correlate increased telomerase activity (TA) with dysplasia and adenocarcinoma occurring in the setting of BE.

MATERIALS AND METHODS

Esophageal mucosal biopsies were obtained from patients (N=62) who had pathologically verified BE at esophagogastroduodenoscopy (EGD). Mucosal biopsies were also obtained from the gastric fundus as controls. Based on histopathology, patients were divided into three groups: 1) BE without dysplasia (n=24); 2) BE with dysplasia (both high grade and low grade, n=13); and 3) BE with adenocarcinoma (n=25). TA was measured by a PCR-based assay (TRAPeze® ELISA Telomerase Detection Kit). Statistical analyses were performed using one-way ANOVA and post-hoc Bonferroni testing.

RESULTS

TA was significantly higher in biopsies of BE with dyplasia and BE with adenocarcinoma than in BE without dysplasia. Subgroup analyses did not reveal any significant correlations between TA and patient age, length of BE, or presence of gastritis.

CONCLUSIONS

Telomerase activity in esophageal mucosal biopsies of BE may constitute a useful biomarker for the early detection of esophageal dysplasia and adenocarcinoma.

Telomerase Activity as a Tumor Marker in Indian Women with Cervical Intraepithelial Neoplasia and Cervical Cancer

BACKGROUND AND OBJECTIVES

Cervical cancer is the most common cancer in Indian women and is a leading cause of death in women worldwide. Cervical cancer develops from pre-neoplastic cervical intraepithelial neoplasia (CIN). This study was conducted to evaluate telomerase activity as a tumor marker for the detection of cancer in patients with CIN and cervical cancer. The results were compared with human papillomavirus (HPV) status, clinical staging, and histopathologic studies.

METHODS

Telomerase activity was detected using the PCR-based telomeric repeat amplification protocol (TRAP) assay in cervical tissues collected by routine punch biopsy from the uterine cervix of patients with suspected cervical cancer. High-risk (HR) HPV-16 and -18 status was determined in all the study groups, including controls. A total of 125 patients (including 50 patients with CIN and 75 patients with cervical cancer [including nine patients with adeno-squamous disease]) and 22 control subjects were studied. The sensitivity and specificity for detecting CIN and cervical cancer were calculated.

RESULTS

Patients with grade I, II, and III CIN showed 17%, 33%, and 57% positivity for telomerase, respectively. In patients with cervical cancer, those at early clinical stages (Ia-IIb) showed 68% positivity and those at later clinical stages showed 92% positivity for telomerase activity. In the present study, telomerase positivity correlated significantly with the detection of HR HPV-16 and -18 (p < 0.001). As a diagnostic test, none of the described analyses combined a sensitivity of > or =90% with a specificity of > or =90%, except in patients with advanced cancer when telomerase activity was used as a diagnostic test.

CONCLUSION

Our findings suggest that telomerase activation is a relatively early event in cervical carcinogenesis and correlates with the grade of cervical lesion, HR-HPV status (16 and 18 subtypes), and clinical staging. Hence, these associations suggest it as a possible target for detection of cervical cancer.

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.

Detection of TERC amplification in cervical epithelial cells for the diagnosis of high-grade cervical lesions and invasive cancer: a multicenter study in China

Because the activation of telomerase is a relatively early event in the progression of cervical carcinogenesis, the expression of the human telomerase RNA gene, TERC, has the potential to serve as a biomarker for both the diagnosis and prognosis of cervical neoplasias. In total, 83 research centers participated in the study, and 7786 patients were enrolled. TERC amplification was detected using a dual-color fluorescence in situ hybridization (FISH) probe set, and these results were compared with cytological and histological results, testing for high-risk human papillomavirus (HPV) DNA (n = 2316 for the HPV DNA test), as well as patient age. TERC amplification was found to be increased in more advanced cases of cervical carcinogenesis. Moreover, a Youden's index value and the area under the receiver operating characteristic (ROC) curve were also calculated for samples with TERC amplification and found to be higher than the same values calculated for both cytology and high-risk HPV analyses of the same samples. With regard to cytological ASCUS and LSIL findings, the combination of HPV + TERC testing showed the potential to provide effective triaging to detect CIN2(+). Therefore, TERC amplification represents a valuable genetic biomarker, which in combination with an evaluation of cytology or HPV testing, can achieve higher sensitivity and specificity in distinguishing high-grade cervical lesions and invasive cancers from low-grade lesions compared with conventional methods.

Cancer stem cells and telomerase as potential biomarkers in veterinary oncology

Despite advances in chemotherapy and radiotherapy, cancer remains a disease of high morbidity and mortality in domestic animals. In parallel to the development of novel therapeutic interventions, appropriate biomarkers are required to detect early-stage disease and disease remission and relapse at both gross and molecular levels, and the effectiveness of therapy. The field of cancer pathogenesis has grown exponentially over the last decade, both in terms of our understanding of the underlying molecular events, and the technologies available to interrogate the cancer cell. This paper reviews the role of the telomerase enzyme and of telomere length as potential biomarkers in cancer. Furthermore, the potential role of cancer stem cells as biomarkers of malignancy and disease progression is assessed.

Molecular targets in gynaecological cancers

The application of high throughput expression profiling and other advanced molecular biology laboratory techniques has revolutionised the management of cancers and is gaining attention in the field of gynaecological cancers. Such new approaches may help to improve our understanding of carcinogenesis and facilitate screening and early detection of gynaecological cancers and their precursors. Individualised prediction of patients' responses to therapy and design of personalised molecular targeted therapy is also possible. The studies of various molecular targets involved in the various signal pathways related to carcinogenesis are particularly relevant to such applications. At the moment, the application of detection and genotyping of human papillomavirus in management of cervical cancer is one of the most well established appliances of molecular targets in gynaecological cancers. Methylation, telomerase and clonality studies are also potentially useful, especially in assisting diagnosis of difficult clinical scenarios. This post-genomic era of clinical medicine will continue to make a significant impact in routine pathology practice. The contribution of pathologists is indispensable in analysis involving tissue microarray. On the other hand, both pathologists and bedside clinicians should be aware of the limitation of these molecular targets. Interpretation must be integrated with clinical and histopathological context to avoid misleading judgement. The importance of quality assurance of all such molecular techniques and their ethical implications cannot be over-emphasised.

Upregulation of telomerase (hTERT) is related to the grade of cervical intraepithelial neoplasia, but is not an independent predictor of high-risk human papillomavirus, virus persistence, or disease outcome in cervical cancer

Telomerase activation and telomere maintenance are essential for cell immortalization and represent a rate-limiting step in cancer progression. The E6 oncoprotein of high-risk human papillomavirus (HPV) is known to activate telomerase, but its expression in CIN lesions and its prognostic value in cervical cancer (CC) are still incompletely understood. As part of our HPV-PathogenISS study, a series of 150 CCs and 152 CIN lesions were examined using immunohistochemical (IHC) staining for hTERT (telomerase reverse transcriptase), and tested for HPV using PCR with three primer sets (MY09/11, GP5(+)/GP6(+), SPF). Follow-up data were available from all SCC patients, and 67 CIN lesions had been monitored with serial PCR for HPV after cone treatment. Expression of hTERT was increased in parallel with the grade of CIN, with major up-regulation upon transition to CIN3 (OR 18.81; 95% CI 8.48-41.69; P = 0.0001). Positive hTERT expression was 90% specific indicator of CIN, with 98.7% PPV, but suffers from low sensitivity (57.5%) and NPV (14.3%). hTERT expression was also significantly associated to HR-HPV with OR 3.38 (95% CI 1.90-6.02; P = 0.0001), but this association was confounded by the histological grade (Mantel-Haenszel common OR = 1.83; 95% CI 0.92-3.79; P = 0.086). Expression of hTERT did not predict clearance/persistence of HR-HPV after treatment of CIN, and it was not a prognostic predictor in cervical cancer in univariate or multivariate survival analysis. It was concluded that up-regulation of hTERT was closely associated with HR-HPV, due to activation by the E6 oncoprotein. hTERT is a late marker of cervical carcinogenesis, significantly associated with progression to CIN3. Theoretically, a combination of hTERT assay (showing high SP and PPV) with another test showing high SE and high NPV (e.g. Hybrid Capture 2 for HPV), should provide an ideal screening tool capable of high-performance detection of CIN lesions.

Telomerase Activity as a Potential Diagnostic Marker for Triage of Abnormal Pap Smears

OBJECTIVES

To determine whether there is an association between high levels of telomerase and premalignant cervical disease and to provide a preliminary analysis of telomerase activity as a potential triage strategy.

MATERIALS AND METHODS

Premenopausal women were invited to participate in the study during routine gynecologic visits as well as visits where colposcopy was performed. Samples were taken from the cervix using a broom device and placed in cold phosphate-buffered saline. A total of 92 samples were evaluated. Cells were counted and lysed, and a semiquantitative measure of telomerase activity was determined using a commercially available telomerase enzyme-linked immunosorbent assay kit. The presence of human papillomavirus (HPV) types 16 and 18 was assessed by polymerase chain reaction analysis. One-way analysis of variance was used to test for the association of telomerase activity with cytology, HPV type 16 or 18 status, and colposcopy and/or biopsy findings.

RESULTS

When telomerase levels were analyzed according to Pap smear results, there were no differences among four groups of cytology findings (normal, atypical squamous cells of undetermined significance, low-grade squamous intraepithelial lesion, and high-grade squamous intraepithelial lesion). When colposcopy and/or biopsy results were considered, significantly higher levels of telomerase were detected in cervical intraepithelial neoplasia (CIN) 2,3 samples than in normal Pap smear samples and CIN 1 samples (p = .035). There was no significant difference in telomerase levels between samples that tested positive for HPV type 16 or 18 and those that did not (p = .111).

CONCLUSIONS

Telomerase levels were significantly higher in cytologic samples from women with biopsy-proven CIN 2,3 than in samples from women with normal cytology results or CIN 1. These results warrant larger studies to determine whether telomerase activity may be a useful triage tool for abnormal cytologic findings.

Chromosome in situ hybridisation, Ki-67, and telomerase immunocytochemistry in liquid based cervical cytology

AIMS

To assess the potential value of chromosome in situ hybridisation (CISH), Ki-67, and telomerase immunocytochemistry in liquid based cervical cytology to help detect carcinoma cells and precursors.

METHOD

Sixty ThinPrep processed cervical cytology samples were studied: 23 cases within the normal limit, 13 low grade squamous intraepithelial lesions (LSILs), 10 high grade squamous intraepithelial lesions (HSILs), six squamous cell carcinomas, three endocervical adenocarcinomas, two cervical adenosquamous cell carcinomas, and three endometrial adenocarcinomas. CISH was performed with DNA probes specific for the pericentromeric regions of chromosome 11 and 16. Hybridisation signals were visualised with the streptavidin-biotin peroxidase technique. The monoclonal MIB1 and polyclonal TRT-H231 antibodies were used to detect Ki-67 and telomerase immunoreactivity, respectively.

RESULTS

Non-specific background staining was almost absent in CISH slides. Normal squamous and glandular cells showed a diploid chromosomal pattern. A relative gain in chromosomes 11 and 16 (aneusomy) was seen in HSIL and the carcinomas (p<0.0001). In MIB1 stained smears, normal cells and koilocytes showed inconspicuous immunoreactivity, whereas strongly immunoreactive nuclei were found in cancer cells and HSIL (p<0.0001). Not only carcinoma and HSIL cells, but also some normal cells, showed cytoplasmic staining for telomerase.

CONCLUSIONS

These preliminary results indicate that ThinPrep processed cervical smears are suitable for CISH and immunocytochemical studies. The neoplastic squamous and glandular cells were easily identified based on nuclear aneusomy and strong Ki-67 immuoreactivity in the context of abnormal nuclear morphology. This is the first study to apply CISH in cervical cytology using an immunoenzymatic approach.

Chapter 1: Human papillomavirus and cervical cancer--burden and assessment of causality

Cervical cancer remains the second most common cancer in women worldwide and the most frequent in developing countries. Pre-neoplasic cervical lesions represent an additional burden in countries where screening is widespread. The human papillomavirus (HPV) prevalence and type distribution in normal smears and in cancer specimens are being described and show relatively small international variation. State-of-the-art detection techniques have unequivocally shown that HPV-DNA can be detected in 95% to 100% of adequate specimens of cervical cancer, supporting the claim that HPV is the necessary cause. The odds ratios for cervical cancer related to a cross sectional detection of HPV-DNA range from 50 to several hundred in all studies. The risk for any of 15 high-risk types is not statistically different from the risk reported for HPV16. The estimates of the attributable fraction range from 90% to 98%. Additional work should be done in providing information on incidence of cervical cancer and on HPV infection in areas where the disease is common. Theoretical work including modeling of the incidence could be of potential use in the evaluation of the existing and novel preventive strategies. Research is currently being conducted on the mechanisms of HPV carcinogenesis. These include the determinants of the systemic and cellular immune response to the viral infection, the interaction between the host and the virus and the relevance of the different strains and variants of the HPV viral types. Technology developments in this area suitable for epidemiological studies are needed.

Telomerase as tumor marker

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

Role of telomeres and telomerase in the pathogenesis of human cancer

Specialized nucleoprotein structures, termed telomeres, cap the ends of human chromosomes. These terminal structures, composed of repetitive arrays of guanine-rich hexameric DNA together with specific telomere-binding proteins, play essential roles in protecting the chromosome from damage and degradation. In addition, several lines of evidence implicate telomere maintenance as an important regulator of cell life span. Activation of telomerase, a dedicated reverse transcriptase that synthesizes telomeric sequences, is strongly associated with cancer, and recent observations confirm that telomeres and telomerase perform important roles in both suppressing and facilitating malignant transformation. These dual functions of telomere biology are evident in the clinical manifestations of the multisystem syndrome, dyskeratosis congenita, forms of which display defects in telomerase function. Recent advances in our understanding of telomere biology indicate that the manipulation of telomeres and telomerase will lead to clinically significant applications in the diagnosis, prevention, and treatment of neoplastic disease.

Telomerase: a potential diagnostic and therapeutic tool in canine oncology

In recent years there has been considerable interest in telomerase as a target for therapeutic intervention in oncology. This largely stems from the vast number of studies that have demonstrated expression and activity of the enzyme telomerase in the majority of human cancer tissues with little or no activity detectable in normal somatic tissues. These studies have led to an interest in the role of telomerase in cancers associated with domesticated species, in particular tumors that affect dogs. This article reviews the biology of telomerase and the biological significance of telomerase activity in canine tumors and discusses the clinical implications of telomerase expression in canine cancers with regard to therapeutics and diagnostics.

Detection of telomerase, its components, and human papillomavirus in cervical scrapings as a tool for triage in women with cervical dysplasia

AIM

To examine whether the detection of either telomerase and its components or high risk human papillomavirus (HPV) are of value in predicting the presence of cervical intraepithelial neoplasia (CIN) grade II/III in women referred because of cervical cytology reports showing at most moderate dyskaryosis.

METHODS

Cervical scrapings of 50 women referred with cytological borderline, mild, or moderate dyskaryosis were analysed. Telomerase activity was assessed by a commercially available telomere repeat amplification protocol assay and its components human telomerase RNA (hTR) and human telomerase reverse transcriptase (hTERT) were assessed by reverse transcriptase polymerase chain reaction (PCR). HPV was detected by GP5+/6+ PCR enzyme immunosassay. Histological findings on colposcopy guided biopsies or excised cervical tissue were regarded as the final pathological diagnosis. The sensitivity and specificity for detecting CIN II/III were calculated.

RESULTS

Twenty eight women were diagnosed with CIN II/III. Telomerase activity was detected in none, hTR in 88%, hTERT in 23%, and high risk HPV was detected in 79% of these women. As a diagnostic test none of the described analyses combined a sensitivity of at least 90% with a specificity >or= 90%. Despite the small numbers, calculation of the 95% confidence intervals excluded a combined sensitivity and specificity of at least 90% for all of the evaluated parameters.

CONCLUSIONS

Neither detection of telomerase or its components, nor detection of high risk HPV seem suitable for the triage of women with borderline, mild, and moderate cytological dyskaryosis.

Amplification of the telomerase reverse transcriptase (hTERT) gene in cervical carcinomas

The expression of telomerase reverse transcriptase (hTERT), the catalytic component of the telomerase complex, is required for activation of telomerase during immortalization and transformation of human cells. However, the biochemical and genetic mechanisms governing hTERT expression remain to be elucidated. In the present study, we examined hTERT amplification as a potential genetic event contributing to telomerase activation in cervical carcinomas. An amplification of the hTERT gene was found in 1/4 cervical cancer cell lines and 21/88 primary tumor samples derived from the patients with cervical carcinomas. An increase in the hTERT copy number was significantly correlated with higher levels of hTERT protein expression. Moreover, the hTERT alterations with the enhanced hTERT expression were exclusively observed in those tumors with high-risk human papillomavirus infection. Taken together, the hTERT gene amplification, directly or indirectly targeted by human papillomavirus, may be one of the driving forces responsible for upregulation of hTERT expression and activation of telomerase in cervical cancers.

Clinical utility of telomerase in cancer

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

Retinoic acid inhibits telomerase activity and downregulates expression but does not affect splicing of hTERT: correlation with cell growth rate inhibition in an in vitro cervical carcinogenesis/multidrug-resistance model

Telomerase, a ribonucleoprotein complex of hTERT, hTR, and TP1, has been reported to be associated with carcinogenesis and multidrug resistance (MDR). This study used our in vitro human cervical multistep carcinogenesis/MDR model system in which normal human ectocervical and endocervical (HEN) cells were immortalized by HPV18 or 16, respectively, and subsequently transformed. The first evidence was found that immortalization and telomerase activation were correlated with increased expression specifically of two of the hTERT alternatively spliced mRNAs, one encoding wild-type protein containing the full-length functional reverse transcriptase (RT) region and one encoding a defective RT protein. Expression of neither hTERT mRNA containing full-length functional or defective RT motif was affected by transformation/MDR. All-trans-retinoic acid (ATRA) treatment of HPV-immortalized HEN-16-2 cells and transformed/MDR HEN-16-2/CDDP cells inhibited telomerase activity and downregulated expression of hTERT mRNAs containing full-length functional and a defective RT motif, but there were no changes in hTR and TP1 expression. Moreover, ATRA inhibited cell growth rate of HEN-16-2 and HEN-16-2/CDDP cells equally. These results provided the first evidence that ATRA equally in both immortalized and transformed/MDR cell lines inhibits telomerase activity and downregulates expression, but not splicing, of hTERT, and this is correlated with cell growth rate inhibition; the potential is implicated for applying ATRA to hTERT-targeted treatment of cervical cell carcinogenesis/MDR.

Telomerase activation and human papillomavirus infection in invasive uterine cervical carcinoma in a set of Malaysian patients

AIM

Telomerase activity was studied in invasive uterine cervical carcinoma to assess whether it was activated during cervical malignant transformation and to look for a possible association with human papillomavirus (HPV) infection in a set of Malaysian patients.

METHODS

Histologically confirmed invasive cervical carcinoma and benign cervices were assayed for telomerase activity using a commercial telomerase polymerase chain reaction (PCR) enzyme linked immunosorbent assay kit. The same cases were subjected to PCR detection of HPV using type specific (HPV types 6b, 11, 16, and 18) followed by L1 open reading frame (ORF) consensus primers.

RESULTS

HPV was detected in 18 (13 HPV-16, one HPV-6b, four only L1 ORF) of 20 invasive cervical carcinoma and one (only L1 ORF) of 19 benign cervices. Raised telomerase activity (A(450 nm) > 0.215) was detected in 11 cervical carcinomas, with A(450 nm) ranging between 0.238 and 21.790 (mean, 3.952) in positive squamous carcinomas, whereas A(450 nm) was only 0.222 in the one positive adenosquamous carcinoma. Five of 11 cervical carcinomas in stage I, three of six in stage II, both in stage III, and the only case in stage IV showed telomerase activation. Increased telomerase activity was noted in five of the 12 lymph node negative, five of the seven lymph node status unknown cases, and the one case with presumed lymph node metastasis. Ten of 18 HPV positive and one of two HPV negative cervical carcinomas showed telomerase upregulation.

CONCLUSIONS

Telomerase is activated in invasive cervical carcinoma. Although larger studies are needed, there seems to be no clear association between telomerase upregulation and HPV status, although there is a suggestion of increased telomerase activity in squamous carcinomas and late stage disease.

Clinical implications of telomerase detection

In 1994 a sensitive method for the detection of telomerase was described. This assay, which was based on the polymerase chain reaction, suggested that telomerase activity was associated with immortal and cancer cells. Since then more than a thousand studies have documented the expression and activity of the enzyme in diseased tissues, primarily tumours. This review gives an overview of the biological significance of telomerase expression and methods for detecting its activity. This is followed by an organ system-based discussion of expression in normal tissues and disease states. We finish with speculation as to the future role of telomerase detection in diagnostic histopathology.