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

Correlation of hTERT Expression with Cervical Cytological Abnormalities and Human Papillomavirus Infection

Telomerase Reverse Transcriptase (TERT) is the main catalytic sub-unit of telomerase, a reverse transcriptase enzyme. Telomerase expression is regulated at many levels, with numerous studies suggesting that up-regulation of human TERT gene (hTERT) at transcriptional level results in immortal cell phenotype associated with cancer. The aim of this study is to determine the correlation between hTERT expression and different cervical precursor lesions, as well as with cervical cancer in patients with confirmed Human papillomavirus (HPV) infection. The study included molecular analyzes on cervical samples from 214 women and matched Papanicolaou (Pap) test results. HPV detection and genotyping was performed by polymerase chain reaction (PCR) and genotyping. Quantitative real-time PCR (qRT-PCR) was performed using TaqMan probes and were calculated relative to the reference gene. Results showed significantly increased hTERT mRNA expression levels in high-grade and low-grade lesions compared to normal control samples (p<0.01) associated with 6.31 fold higher risk for developing ASC-US and 9.20 for LSIL. Strong correlation between HPV infection and hTERT expression in the high-grade lesions and cervical cancer was also observed. hTERT relative expression values showed 98% specificity and 100 % sensitivity as indicator of cervical lesions particularly for the ACS-H, HSIL and cervical cancer. In conclusion, hTERT expression correlate with the cytological grade of the cervical lesions and HPV infection and has a potential to be used as a diagnostic and prognostic marker.

Human papillomavirus testing versus repeat cytology for triage of minor cytological cervical lesions

BACKGROUND

Atypical squamous cells of undetermined significance (ASCUS) and low-grade squamous intra-epithelial lesions (LSIL) are minor lesions of the cervical epithelium, detectable by cytological examination of cells collected from the surface of the cervix of a woman.Usually, women with ASCUS and LSIL do not have cervical (pre-) cancer, however a substantial proportion of them do have underlying high-grade cervical intra-epithelial neoplasia (CIN, grade 2 or 3) and so are at increased risk for developing cervical cancer. Therefore, accurate triage of women with ASCUS or LSIL is required to identify those who need further management.This review evaluates two ways to triage women with ASCUS or LSIL: repeating the cytological test, and DNA testing for high-risk types of the human papillomavirus (hrHPV) - the main causal factor of cervical cancer.

OBJECTIVES

Main objective To compare the accuracy of hrHPV testing with the Hybrid Capture 2 (HC2) assay against that of repeat cytology for detection of underlying cervical intraepithelial neoplasia of grade 2 or worse (CIN2+) or grade 3 or worse (CIN3+) in women with ASCUS or LSIL. For the HC2 assay, a positive result was defined as proposed by the manufacturer. For repeat cytology, different cut-offs were used to define positivity: Atypical squamous cells of undetermined significance or worse (ASCUS+), low-grade squamous intra-epithelial lesions or worse (LSIL+) or high-grade squamous intra-epithelial lesions or worse (HSIL+).Secondary objective To assess the accuracy of the HC2 assay to detect CIN2+ or CIN3+ in women with ASCUS or LSIL in a larger group of reports of studies that applied hrHPV testing and the reference standard (coloscopy and biopsy), irrespective whether or not repeat cytology was done.

SEARCH METHODS

We made a comprehensive literature search that included the Cochrane Register of Diagnostic Test Accuracy Studies; the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MEDLINE (through PubMed), and EMBASE (last search 6 January 2011). Selected journals likely to contain relevant papers were handsearched from 1992 to 2010 (December). We also searched CERVIX, the bibliographic database of the Unit of Cancer Epidemiology at the Scientific Institute of Public Health (Brussels, Belgium) which contains more than 20,000 references on cervical cancer.More recent searches, up to December 2012, targeted reports on the accuracy of triage of ASCUS or LSIL with other HPV DNA assays, or HPV RNA assays and other molecular markers. These searches will be used for new Cochrane reviews as well as for updates of the current review.

SELECTION CRITERIA

Studies eligible for inclusion in the review had to include: women presenting with a cervical cytology result of ASCUS or LSIL, who had undergone both HC2 testing and repeat cytology, or HC2 testing alone, and were subsequently subjected to reference standard verification with colposcopy and colposcopy-directed biopsies for histologic verification.

DATA COLLECTION AND ANALYSIS

The review authors independently extracted data from the selected studies, and obtained additional data from report authors.Two groups of meta-analyses were performed: group I concerned triage of women with ASCUS, group II concerned women with LSIL. The bivariate model (METADAS-macro in SAS) was used to assess the absolute accuracy of the triage tests in both groups as well as the differences in accuracy between the triage tests.

MAIN RESULTS

The pooled sensitivity of HC2 was significantly higher than that of repeat cytology at cut-off ASCUS+ to detect CIN2+ in both triage of ASCUS and LSIL (relative sensitivity of 1.27 (95% CI 1.16 to 1.39; P value < 0.0001) and 1.23 (95% CI 1.06 to 1.4; P value 0.007), respectively. In ASCUS triage, the pooled specificity of the triage methods did not differ significantly from each other (relative specificity: 0.99 (95% CI 0.97 to 1.03; P value 0.98)). However, the specificity of HC2 was substantially, and significantly, lower than that of repeat cytology in the triage of LSIL (relative specificity: 0.66 (95% CI 0.58 to 0.75) P value < 0.0001).

AUTHORS' CONCLUSIONS

HPV-triage with HC2 can be recommended to triage women with ASCUS because it has higher accuracy (significantly higher sensitivity, and similar specificity) than repeat cytology. When triaging women with LSIL, an HC2 test yields a significantly higher sensitivity, but a significantly lower specificity, compared to a repeat cytology. Therefore, practice recommendations for management of women with LSIL should be balanced, taking local circumstances into account.

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.

Different amplification patterns of the human telomerase RNA gene in invasive cervical carcinomas and cervical intraepithelial neoplasia grade III

The aim of this study was to compare the amplification patterns of the human telomerase RNA gene (hTERC) in invasive cervical carcinomas (ICC) and cervical intraepithelial neoplasia grade III (CIN III) and to define their potential clinical implications. Cervical liquid-based cytological (LBC) specimens were collected from 53 squamous cell carcinomas (SCC), 14 CIN III, and 20 normal controls. Copy numbers of the hTERC gene were measured by fluorescence in situ hybridization (FISH) using a dual-color probe containing the hTERC probe and the control, chromosome 3 centromere-specific probe (CSP3). Nucleus with abnormal FISH pattern for hTERC was observed in 0.94-90.65% of SCC cells and in 0-85.59% of CIN III cells. Using the threshold of 5.89%, the occurrence of hTERC amplification in SCC and CIN III was similar (90.6% vs. 85.7%, P = 0.630). However, the median percentage of cells with extra gains of hTERC (hTERC:CSP3 > 1) in SCC was higher than in CIN III (64.3% vs. 31.7%, P = 0.001). Among those cells, the 3:2 signal pattern was the leading pattern for both SCC and CIN III; high-level amplification of hTERC was more common in SCC than in CIN III (60.9% vs. 48.9%, P = 0.002). In SCC, it was not found that extra gains of hTERC were associated with any clinicopathological parameters. Thus, hTERC amplification was common in cervical exfoliated cells from SCC and CIN III. More complex amplification patterns of hTERC were present in ICC. Clinical usefulness of hTERC amplification in LBC samples was limited in ICC.

Human telomerase RNA gene amplification detection increases the specificity of cervical intraepithelial neoplasia screening

OBJECTIVES

The purpose of this study was to evaluate the clinical significance of genomic amplification of the human telomerase RNA gene (TERC) for cervical cancer screening and explore whether it can serve as a biomarker to improve the specificity of human papillomavirus (HPV) DNA testing for cervical cancer screening.

METHODS

One hundred twenty women, including 20 cases of normal (control), 14 cases of cervical intraepithelial neoplasia grade I (CIN I), 35 cases of CIN II, 36 cases of CIN III, and 15 cases of squamous cervical cancer diagnosed by histopathologic evaluation, were subjected to cytopathologic examination, TERC detection by fluorescence in situ hybridization (FISH), and HPV DNA testing by Hybrid Capture II.

RESULTS

TERC amplification was significantly associated with cytopathologic diagnosis (P < 0.001) and histopathologic evaluation (P < 0.001). The positive rate of TERC gain was significantly higher in patients with CIN III or squamous cervical cancer than in patients with CIN I or those in the control group (P < 0.001). The specificity and positive predictive value of FISH for detecting CIN II or more severe cervical lesions (> or = CIN II) were obviously higher than those of HPV DNA testing (97.1% vs 52.9%, 98.7% vs 83.8%).

CONCLUSIONS

TERC amplification analyzed by FISH may serve as an adjunctive test to HPV DNA testing for improving the specificity and positive predictive value of cervical cancer screening.

hTERT promoter activity and CpG methylation in HPV-induced carcinogenesis

Background

Activation of telomerase resulting from deregulated hTERT expression is a key event during high-risk human papillomavirus (hrHPV)-induced cervical carcinogenesis. In the present study we examined hTERT promoter activity and its relation to DNA methylation as one of the potential mechanisms underlying deregulated hTERT transcription in hrHPV-transformed cells.

Methods

Using luciferase reporter assays we analyzed hTERT promoter activity in primary keratinocytes, HPV16- and HPV18-immortalized keratinocyte cell lines and cervical cancer cell lines. In the same cells as well as cervical specimens we determined hTERT methylation by bisulfite sequencing analysis of the region spanning -442 to +566 (relative to the ATG) and quantitative methylation specific PCR (qMSP) analysis of two regions flanking the hTERT core promoter.

Results

We found that in most telomerase positive cells increased hTERT core promoter activity coincided with increased hTERT mRNA expression. On the other hand basal hTERT promoter activity was also detected in telomerase negative cells with no or strongly reduced hTERT mRNA expression levels. In both telomerase positive and negative cells regulatory sequences flanking both ends of the core promoter markedly repressed exogenous promoter activity.

By extensive bisulfite sequencing a strong increase in CpG methylation was detected in hTERT positive cells compared to cells with no or strongly reduced hTERT expression. Subsequent qMSP analysis of a larger set of cervical tissue specimens revealed methylation of both regions analyzed in 100% of cervical carcinomas and 38% of the high-grade precursor lesions, compared to 9% of low grade precursor lesions and 5% of normal controls.

Conclusions

Methylation of transcriptionally repressive sequences in the hTERT promoter and proximal exonic sequences is correlated to deregulated hTERT transcription in HPV-immortalized cells and cervical cancer cells. The detection of DNA methylation at these repressive regions may provide an attractive biomarker for early detection of cervical cancer.

Human Telomerase Gene Amplification and High-Risk Human Papillomavirus Infection in Women with Cervical Intra-Epithelial Neoplasia

This study was designed to investigate whether a correlation exists between amplification of the human telomerase gene (human telomerase RNA component [ TERC]) and high-risk human papillomavirus (HR-HPV) infection in 101 women with cervical intra-epithelial neoplasia (CIN). Eight patients (7.9%) had CIN 1, 24 (23.8%) had CIN 2 and 69 (68.3%) had CIN 3. TERC was amplified in 31.7% of all CIN patients. The difference in frequency of TERC amplification between patients with low-grade CIN (CIN 1) and those with high-grade CIN (CIN 2 and CIN 3) was not significant. HR-HPV infection was detected in 88.1% of all CIN cases and was significantly more frequent in patients with CIN 2 and CIN 3 than in patients with CIN 1. There was no significant difference in the frequency of HR-HPV infection between groups of patients with and without TERC amplification. In conclusion, this study found no correlation between TERC amplification and HR-HPV infection in patients with CIN.

Immunohistochemical expression of ubiquitin and telomerase in cervical cancer

Ubiquitin and telomerase immunohistochemical expression patterns in cervical cancer were compared with normal cervical tissue samples. Eighty-one cervical cancer cases and 22 normal exo-endocervical tissue were examined with polyclonal antibody for ubiquitin and 44G12 clone for telomerase using tissue microarrays. The results were interpreted using a semiquantitative scale The average age of patients was 50.67 years. The most frequent histological types were moderately differentiated epidermoid carcinoma (43.5%), according to the degree of differentiation, and endocervical adenocarcinoma (42.1%). Immunohistochemical findings were as follows: 98.7% of cervical cancers showed immunoexpression for ubiquitin and 52.6% for telomerase. Statistically significant differences were found in tumor immunoreactivity when compared with control tissue (p < 0.0007) for both biomarkers. There was no significant difference in biomarker expression at different histological types of tumors, although telomerase was less expressed in endocervical adenocarcinoma. Our findings confirm that abnormal immunoexpression pattern of ubiquitin and telomerase is common in HPV-positive cervical cancer, indicating the existence of an intense degradation of proteins, subsequent cellular immortalization and maintenance of the malignant phenotype.

Clinical significance of hTERC gene amplification detection by FISH in the screening of cervical lesions

This study evaluated the clinical significance of hTERC gene amplification detection by fluorescence in situ hybridization (FISH) in the screening of cervical lesions. Cervical specimens of 50 high risk patients were detected by thin liquid-based cytology. The patients whose cytological results were classified as ASCUS or above were subjected to the subsequent colposcopic biopsies. Slides prepared from these 50 cervical specimens were analyzed for hTERC gene amplification using interphase FISH with the two-color hTERC probe. The results of the cytological analysis and those of subsequent biopsies, when available, were compared with the FISH-detected hTERC abnormalities. It was found that the positive rates of hTERC gene amplification in NILM, ASCUS, LSIL, HSIL, and SCC groups were 0.00, 28.57%, 57.14%, 100%, and 100%, respectively. The positive rates of hTERC gene amplification in HSIL and SCC groups were significantly higher than those in NILM, ASCUS and LSIL groups (all P<0.05). The mean percentages of cells with hTERC gene amplification in NILM, ASCUS, LSIL, HSIL, and SCC groups were 0.00, 10.50%, 36.00%, 79.00%, and 96.50%, respectively. Patients with HSIL or SCC cytological diagnoses had significantly higher mean percentages of cells with hTERC gene amplification than did patients with NILM, ASCUS or LSIL cytological diagnoses (all P<0.05). It was concluded that two-color interphase FISH could detect hTERC gene amplification to accurately distinguish HSIL and ISIL of cervical cells. It may be an adjunct to cytology screening, especially high-risk patients.

Gene expression profiling to identify markers associated with deregulated hTERT in HPV-transformed keratinocytes and cervical cancer

Although high-risk human papillomavirus (HPV) infection plays a major role in the development of cervical cancer, additive oncogenic events are involved as well. One key event involves increased activity of telomerase resulting from a deregulated expression of its catalytic subunit hTERT. Our previous microcell-mediated chromosome transfer studies revealed that introduction of human chromosome 6 in the HPV16-immortalized keratinocyte cell line FK16A and in the HPV16-containing cervical cancer cell line SiHa induced growth arrest, resulting from a repression of hTERT mRNA expression and telomerase activity. Here, this model was used to analyze expression profiles associated with hTERT deregulation in HPV-transformed cells. Microarray expression analysis of 12 FK16A/chromosome 6 hybrids, 4 of which were negative for endogenous hTERT and 8 of which were positive for endogenous hTERT, resulted in the identification of 164 differentially expressed genes. Differential expression of a selection of 5 genes was verified by real-time RT-PCR. Of these 164 genes, 32 were also differentially expressed in other HPV transformed cells with deregulated hTERT. For 2 of these genes, encoding AQP3 and MGP, altered expression in hTERT positive cervical carcinomas was confirmed by real-time RT-PCR and immunohistochemistry, respectively. Moreover, increased MGP protein expression was significantly more frequent in high-grade cervical premalignant lesions with elevated hTERT mRNA expression compared to those without. In summary, we identified 32 candidate biomarkers for deregulated hTERT mRNA expression, which may enable the identification of cervical premalignant lesions that are at highest risk to progress to invasive cancer.

Emerging biomarkers in the detection, diagnosis and management of cervical dysplasia and carcinoma

Despite the success of widespread screening, cervical cancers continue to occur. Recently, the role of human papillomavirus (HPV) in cervical carcinogenesis has been firmly established. HPV prophylactic vaccines are expected to eradicate ∼ 70% of cervical cancers. An HPV test was demonstrated to improve the sensitivity of cytology and prolong the screening interval safely. Type-specific HPV testing will play an important role in the detection and follow up of cervical neoplastic lesions, as well as monitoring the efficacy of HPV vaccines. The combined use of cell proliferation markers with cytology can improve sensitivity, and some molecular markers seem to be related to the degree of dysplasia. Further studies are needed to evaluate the use of biomarkers in clinical settings.

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.

The role of telomeres and telomerase in the pathology of human cancer and aging

Cellular senescence, the state of permanent growth arrest, is the inevitable fate of replicating normal somatic cells. Postulated to underlie this finite replicative span is the physiology of telomeres, which constitute the ends of chromosomes. The repetitive sequences of these DNA-protein complexes progressively shorten with each mitosis. When the critical length is bridged, telomeres trigger DNA repair and cell cycle checkpoint mechanisms that result in chromosomal fusions, cell cycle arrest, senescence and/or apoptosis. Should senescence be bypassed at such time, continued cell divisions in the face of dysfunctional telomeres and activated DNA repair machinery can result in the genomic instability favourable for oncogenesis. The longevity and malignant progression of the thus transformed cell requires coincident telomerase expression or other means to negate the constitutional telomeric loss. Practically then, telomeres and telomerase may represent plausible prognostic and screening cancer markers. Furthermore, if the argument is extended, with assumptions that telomeric attrition is indeed the basis of cellular senescence and that accumulation of the latter equates to aging at the organismal level, then telomeres may well explain the increased incidence of cancer with human aging.

Dynamic behavioural interpretation of cervical intraepithelial neoplasia with molecular biomarkers

The microscopic phenotype of cervical intraepithelial neoplasia (CIN) reflects a fine balance between factors that promote or reduce CIN development. A shortcoming of the current grading system is its reliance on static morphology and microscopic haematoxylin-eosin features of the epithelium alone. In reality, CIN is a dynamic process, and the epithelium may exhibit differing results over time. Functional biomarkers p16, Ki-67, p53, retinoblastoma protein cytokeratin (CK)14 and CK13, help in the assessment of an individual CIN's lesion's potential for progression and regression. The aggregate information provided by these biomarkers exceeds the value of the classic grading system. Consequently, many more CINs that will either regress or progress can be accurately identified. These findings agree with known molecular interactions between HPV and the host. For accurate interpretation of a CIN, it is essential that these biomarkers be determined quantitatively and separately in the superficial, middle and deep layers of the epithelium. Such geography-specific epithelial evaluations of quantitative biomarkers emphasise the dynamic nature of a particular CIN lesion, thereby changing the art of static morphology grading into dynamic interpretation of the diseased tissue, with a strong prognostic effect.

HPV-mediated cervical carcinogenesis: concepts and clinical implications

Persistent infection with a high-risk human papillomavirus (hrHPV) is generally accepted as a necessary cause of cervical cancer. However, cervical cancer is a rare complication of an hrHPV infection since most such infections are transient, not even giving rise to cervical lesions. On average, it takes 12-15 years before a persistent hrHPV infection may ultimately, via consecutive premalignant stages (ie CIN lesions), lead to an overt cervical carcinoma. This argues that HPV-induced cervical carcinogenesis is multi-step in nature. In this review, the data from hrHPV-mediated in vitro transformation studies and those obtained from analysis of clinical specimens have been merged into a cervical cancer progression model. According to this model, a crucial decision maker in the early stages following infection involves individual susceptibility for certain HPV types depending on the genetic make-up of immune surveillance determinants. Once a CIN lesion has developed, altered transcriptional regulation of the viral E6/E7 oncogenes, resulting in genomic instability and distinguishing the process of cell transformation from a productive viral infection, probably provides the subsequent important step towards malignancy. The additional (epi)genetic alterations that subsequently accumulate in high-grade CIN lesions may result in overt malignancy via immortality and growth conditions that gradually become less sensitive to growth-modulating influences mediated by cytokines and cell-cell and cell-matrix adhesions. The potential implications of hrHPV testing and some other biomarkers deduced from this model for cervical screening and the clinical management of CIN disease are also discussed.

Quantitative determination of human telomerase reverse transcriptase messenger RNA expression in premalignant cervical lesions and correlation with human papillomavirus load

Expression of human telomerase reverse transcriptase (hTERT) messenger RNA (mRNA) and human papillomavirus (HPV)-16 load were quantified using real-time polymerase chain reaction and correlated with cytological findings and the presence of HPV infection in cervical specimens. Human telomerase reverse transcriptase mRNA expression was evaluated in 15 (20.5%) of 73 specimens of atypical squamous epithelial cells of undetermined significance, in 62 (39.7%) of 156 low-grade squamous intraepithelial lesions (LGSILs), in 49 (96%) of 51 high-grade squamous intraepithelial lesions (HGSILs), and in 9 (20%) of 45 normal samples, whereas viral load was quantified in 52 (89.6%) of 58 samples infected with HPV-16. The mean levels of hTERT mRNA expression were 0.11 in normal tissue, 0.23 in atypical squamous epithelial cells of undetermined significance, 0.75 in LGSILs, and 2.5 in HGSILs. Thus, a significant increase in hTERT mRNA expression was observed with increasing degrees of cervical dysplasia. The HPV-16 load was significantly higher in samples of HGSIL than in those of LGSILs (P < .001). A significant correlation was observed between viral load and quantitative hTERT mRNA expression (r = 0.65; P < .05). Quantitative hTERT mRNA assessment showed 96% sensitivity and 100% negative predictive value for high-grade dysplasia, whereas the specificity and positive predictive value were 72% and 36.2%, respectively. It is suggested that quantitative hTERT has a very high sensitivity and negative predictive value, whereas the observed specificity was moderate, indicating that it cannot be used as a diagnostic marker but may be an adjunct in the management of women with high-grade cervical dysplasia. However, the final diagnosis must rely on the inclusion of clinical evaluation and additional assessment data.

Potential of telomerase expression and activity in cervical specimens as a diagnostic tool

AIMS

To evaluate the potential use of the immunohistochemical expression of telomerase and the measurement of its activity as diagnostic tools in the uterine cervix.

METHODS

The fluorescent telomeric repeat amplification protocol (TRAP) assay was used to evaluate telomerase activity in a series of 43 cervical scrapings. Twenty five cases were cytologically classified as inflammatory, and/or metaplastic, and/or acanthotic, and 18 cases presented cell alterations compatible with mild, moderate, or severe cervical intraepithelial neoplasia (CIN). Immunohistochemistry was performed on a retrospective series of 86 archival, paraffin wax embedded blocks using a recently developed anti-hTERT (human telomerase reverse transcriptase) monoclonal antibody.

RESULTS

Telomerase activity was expressed as arbitrary enzymatic units (AEU). Median values were 38.0 AEU for inflammatory non-dysplastic cell specimens, 33.5 AEU for CIN I, 41.0 AEU for CIN II, and 28.0 AEU for CIN III. The median percentage of immunoreactive dysplastic cells, as detected by immunohistochemistry, was significantly (p = 0.024) lower in CIN I (45%) than in more severe dysplastic (CIN II 70%, CIN III 80%) lesions. In contrast, no differences were seen in the enzymatic activity detected by the TRAP assay among the different dysplastic lesions.

CONCLUSIONS

These data indicate that, using a molecular extra situ method, the telomerase activity of inflammatory and non-dysplastic elements masks the expected differences between mild and severe dysplasia. Conversely, an in situ approach permits the accurate identification of telomerase positive dysplastic cells.

HPV-mediated transformation of the anogenital tract

Infection with high-risk human papillomavirus (HR-HPV) has been associated with intraepithelial neoplasia and carcinomas at various sites of the anogenital tract, including the cervix, vulva, vagina, penis and anus. Although HR-HPV is a necessary cause for cervical cancer, the majority of anal cancers and a subset of cancers at other genital sites, additional (epi)genetic events are required for malignant transformation. HPV-mediated transformation of human epithelial cells has been recognized as a multi-step process resulting from deregulated transcription of the viral oncogenes E6 and E7 in the proliferating cells. Interference of E6 and E7 with cell cycle regulators induces genetic instability, which drives the continuous selection of oncogenic alterations providing cells with a malignant phenotype. Early genetic events during cervical carcinogenesis associated with immortalization, include deletions at chromosomes 3p, 6 and 10p, whereas amongst others gain of chromosome 3q, loss of chromosome 11 and epigenetic alterations such as inactivation of the TSLC1 tumor suppressor gene represent later events associated with tumor invasion.

The role of human telomerase catalytic subunit mRNA expression in cervical dysplasias

Telomerase activity and human telomerase reverse transcriptase (hTERT) mRNA expression were investigated in cervical specimens and were correlated with cytologic findings and the presence of human papilloma virus (HPV) infection. Telomerase activity was evaluated by the telomeric repeat protocol assay and hTERT mRNA expression was evaluated by reverse transcriptase polymerase chain reaction (PCR). HPV DNA was detected by PCR, as well as restriction endonuclease digestion. HPV DNA was detected in all 82 specimens with abnormal cytologic findings and in 4 of 34 normal samples. Low-grade squamous intraepithelial lesions (LGSILs) were present in 74 of 82 specimens (90.2%) and high-grade squamous intraepithelial lesions (HGSILs) were present in 8 of 82 (9.75%) specimens. Seven of the eight HGSIL (87.5%) and 26 of 74 LGSIL (35.1%) specimens were hTERT positive, whereas all normal specimens were hTERT mRNA negative. Telomerase activity was detected in 21 of 74 (28.4%) LGSIL/atypical squamous epithelial cells of undetermined significance (ASCUS) and in five of eight (62.5%) HGSIL samples. A correlation was observed among telomerase activity, hTERT mRNA expression, and high-risk HPV infection in HGSIL samples (P < 0.001). High-risk HPV infection assessment showed 75% sensitivity and 72.2% specificity for HGSILs. Telomerase activity assessment in cervical smears showed sensitivity and negative predictive value (NPV) for HGSILs 62.5% and 96.7%, whereas specificity and positive predictive value (PPV) were 80.5% and 19.2%, respectively. hTERT mRNA expression assessment showed 87.5% sensitivity and 98.7% NPV for HGSILs, whereas specificity and PPV were 76% and 21.2%, respectively. Based on the above-described telomerase assessment values, it is suggested that the telomerase system might not be an appropriate diagnostic marker for cytology, given that the final evaluation must rely on a combination of all available test assessment data, clinical diagnosis, as well as the follow-up of all LGSIL samples that were positive for telomerase activation.

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.

Human papillomavirus testing as a cytology gold standard: comparing Surinam with the Netherlands

Polymerase chain reaction to detect high-risk human papillomavirus has been suggested as a gold standard for cytology. The Netherlands and Surinam were prospectively compared in regard to the proportions of Negative, Atypical Squamous Cells of Undetermined Significance, and Squamous Intraepithelial Lesion smears that had detectable high-risk human papillomavirus. For the Netherlands, 14 600 negative, 270 Atypical Squamous Cells of Undetermined Significance and 120 Squamous Intraepithelial Lesion smears were evaluated by polymerase chain reaction. For Surinam, 150 negative, 50 Atypical Squamous Cells of Undetermined Significance, and 150 Squamous Intraepithelial Lesion smears were evaluated by polymerase chain reaction. In all, 4% of Dutch and 80% of Surinamese negative smears had detectable high-risk human papillomavirus (chi2=1313, P<0.00001). In total, 41.9% of Dutch and 84% of Surinamese Atypical Squamous Cells of Undetermined Significance smears had detectable high-risk human papillomavirus (chi2=28, P<0.00001). Totally, 67.5% of Dutch and 94% of Surinamese SIL smears had detectable high-risk human papillomavirus (chi2=30, P<0.00001). The Negative: Atypical Squamous Cells of Undetermined Significance odds ratio was 0.058 for the Netherlands and 0.762 for Surinam (chi2homog=31, P<0.00001). The Negative: Squamous Intraepithelial Lesion odds ratio was 0.020 for the Netherlands and 0.255 for Surinam (chi2homog=31, P<0.00001). The Atypical Squamous Cells of Undetermined Significance: Squamous Intraepithelial Lesion odds ratio was 0.347 for the Netherlands and 0.335 for Surinam (chi2homog=0.005, P>0.75). Human papillomavirus DNA testing may not be a suitable gold standard in general because its use would make specificity and sensitivity prevalence-dependent. A new statistic, the percent of Negative pap smears with detectable high-risk human papillomavirus, is posited, which may be important if human papillomavirus DNA testing is used clinically.

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.

Telomerase and human papillomavirus as diagnostic adjuncts for cervical dysplasia and carcinoma

Telomerase and human papillomavirus (HPV) DNA were evaluated as potential markers of high-grade dysplasia in cervical cytological specimens. Cytology specimens were collected from patients at the time of colposcopic evaluation for management of a previous abnormal cytology test result. Telomerase activity was evaluated by the telomeric repeat amplification protocol (TRAP), and HPV DNA was detected by polymerase chain reaction with L1 consensus-sequence primers and filter hybridization genotyping. Telomerase was detected in 8 of 97 (8.2%) cases with normal cytology or benign cellular changes, in 7 of 98 (7.1%) cases of atypical squamous cells of undetermined significance (ASCUS), in 3 of 95 (3.2%) cases of low-grade squamous intraepithelial lesion (LSIL), and in 17 of 48 (35.4%) cases with high-grade squamous intraepithelial lesion (HSIL). High-risk HPVs were detected in 23 of 97 (23.7%) cases with normal/reactive cellular changes (RCC) cytology, in 28 of 98 (28.6%) cases of ASCUS, in 69 of 95 (72.6%) cases of LSIL, and in 35 of 48 (72.9%) cases of HSIL. Telomerase expression did not correlate with the detection of high-risk HPVs in any cytological diagnostic categories. Telomerase and HPV test results of cytological specimens were correlated with the histological diagnoses of concurrent cervical biopsy specimens. Telomerase showed a sensitivity of 29.9% and a specificity of 94.0% for biopsy-confirmed cervical intraepithelial neoplasia (CIN) II/III. In contrast, high-risk HPVs were detected in 70.1% of cases with underlying CIN II/III, with a specificity of 62.5%. A relatively high proportion of normal/RCC or ASCUS cases with telomerase-positive test results had underlying high-grade dysplasia on cervical biopsy. Thus, technical and practical limitations of the TRAP assay in cervical cytology specimens limit the practical application of telomerase as a diagnostic adjunct in cervical cytopathology.

E6 and E7 oncoproteins induce distinct patterns of chromosomal aneuploidy in skin tumors from transgenic mice

Inactivation of the tumor suppressor genes p53 and Rb are two of the most common genetic alterations in cancer cells. We use a mouse model to dissect the consequences of compromising the function of either of these genes on the maintenance of genomic stability. Thirteen cell lines established from skin tumors of mice expressing either the E6 or E7 oncoprotein of the human papillomavirus (HPV) type 16 under control of the keratin 14 promoter were analyzed by comparative genomic hybridization, spectral karyotyping and fluorescence in situ hybridization, reverse transcription-PCR, and mutation analysis. Deducing from the wealth of molecular cytogenetic data available from human cancers, we hypothesized that the more benign tumors in mice expressing E7 would be distinct from the more aggressive lesions in E6 transgenic mice. Tumorigenesis in E6-expressing mice required specifically the selection and maintenance of cells with extra copies of chromosome 6. Aneuploidy of chromosome 6 was independent of activating mutations in H-ras on chromosome 7. Expression of either E6 or E7 resulted in centrosome aberrations, indicating that each viral oncoprotein interferes independently with the centrosome cycle. Although centrosome aberrations are consistent with development of aneuploidy, no direct correlation was evident between the degree of aneuploidy and the percentage of cells with aberrant centrosomes. Our results show that although aneuploidy and centrosome aberrations are present in tumor cells from mice expressing either E6 or E7, tumorigenesis via E6 requires copy number increases of mouse chromosome 6, which is partially orthologous to human chromosome 3q, a region gained in HPV-associated carcinomas.

Epidemiological and clinical aspects of human papillomavirus detection in the prevention of cervical cancer

Cervical cancer is a major cause of death, and the second most frequent cancer in women worldwide. Many studies have indicated a causal relation between genital human papillomavirus (HPV) infections and cervical cancer. High-risk HPV genotypes have been detected in almost 100% of all cervical cancers, and the process of HPV mediated carcinogenesis has been partly clarified. The concept that HPV is a obligatory cause in cervical cancer development has lead to extensive research regarding the incorporation of HPV detection in (1) cervical cancer prevention programs, (2) triage of women with abnormal cervical scrapes in the screening program, and (3) follow-up of patients treated for cervical intraepithelial neoplasia (CIN). Epidemiological studies indicate that 50% of women becoming sexually active contract a genital HPV infection within 2 years. The lifetime risk of a genital HPV infection is estimated to be 80%, but very few of these women will develop cervical cancer. Several studies have shown that the persistence of genital HPV infections is especially related to the development of cervical cancer. As a result, HPV detection at a single moment was shown to be of limited clinical value in the triage of patients with abnormal cervical scrapes, or during follow-up after treatment for CIN. Furthermore, major variations in the sensitivity of different HPV detection methods, as well as differences in HPV detection related to the menstrual cycle, have shown that many facts regarding HPV transmission, replication, and detection need to be clarified, before HPV detection can be of clinical value.

Detection of genomic amplification of the human telomerase gene (TERC) in cytologic specimens as a genetic test for the diagnosis of cervical dysplasia

Invasive cervical carcinomas frequently reveal additional copies of the long arm of chromosome 3. The detection of this genetic aberration in diagnostic samples could therefore complement the morphological interpretation. We have developed a triple-color DNA probe set for the visualization of chromosomal copy number changes directly in thin-layer cervical cytology slides by fluorescence in situ hybridization. The probe set consists of a BAC contig that contains sequences for the RNA component of the human telomerase gene (TERC) on chromosome band 3q26, and repeat sequences specific for the centromeres of chromosomes 3 and 7 as controls. In a blinded study, we analyzed 57 thin-layer slides that had been rigorously screened and classified as normal (n = 13), atypical squamous cells (ASC, n = 5), low-grade squamous intraepithelial lesions (LSIL, n = 14), and high-grade squamous intraepithelial lesions (HSIL) grade 2 (CIN2, n = 8), and grade 3 (CIN3, n = 17). The percentage of tetraploid cells (P(Trend) < 0.0005) and cells with multiple 3q signals increased with the severity of the cytologic interpretation (P(Trend) < 0.0005). While only few normal samples, ASC and LSIL lesions, revealed copy number increases of 3q, 63% of the HSIL (CIN2) lesions and 76% of the HSIL (CIN3) lesions showed extra copies of 3q. We conclude that the visualization of chromosome 3q copy numbers in routinely prepared cytological material using BAC clones specific for TERC serves as an independent screening test for HSIL and may help to determine the progressive potential of individual lesions.