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

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.

Biomarkers of cervical dysplasia and carcinoma

Although cervical cytology screening has decreased the incidence of cervical cancer in industrialized countries, HPV-related cervical disease, including premalignant and malignant lesions, continues to represent a major burden on the health care system. Some of the problems include the potential for either under- or overtreatment of women due to decreased specificity of screening tests as well as significant interobserver variability in the diagnosis of cervical dysplastic lesions. Although not completely elucidated, the HPV-driven molecular mechanisms underlying the development of cervical lesions have provided a number of potential biomarkers for both diagnostic and prognostic use in the clinical management of these women.

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.

Genomic amplification of the human telomerase RNA gene for differential diagnosis of cervical disorders

To evaluate genomic amplification of the human telomerase RNA gene (TERC) as a supportive approach to cytopathology or histopathology in diagnosis of low-grade and high-grade uterine cervical lesions, 1,033 Chinese women at three medical centers had liquid-based thin-layer cytopathologic examination and TERC detection by fluorescence in situ hybridization (FISH). Human papillomavirus DNA testing, colposcopy with or without biopsy, and histopathologic examination were conducted as needed. In cytopathologic examination, genomic amplification of TERC was found in 30 of 659 (4.6%) normal or benign cellular changes; in 23 of 170 (13.5%) atypical squamous cells of undetermined significance (ASCUS); in 8 of 28 (28.6%) atypical squamous cells with high-grade squamous intraepithelial lesion possible (ASC-H); and in 26 of 103 (25.2%) low-grade (LSIL) and 64 of 73 (87.7%) high-grade (HSIL) squamous intraepithelial lesions; with pairwise significant difference (P< 0.05) in each, except ASC-H and LSIL (chi(2) = 0.127, P = 0.72). In histopathologic examination, TERC was amplified in 28 of 671 (4.2%) normal, inflammatory, or wart cases; in 17 of 233 (7.3%) cervical intraepithelial neoplasia grade 1 cases (CIN 1); in 27 of 39 (69.2%) CIN 2 cases; in 57 of 67 (85.1%) CIN 3 cases; and in 22 of 23 (95.7%) cervical cancer cases; with pairwise significant difference in each (P < 0.05). The number of cells with abnormal signals increased and the abnormal signal patterns were diversified with increasing severity of cervical dysplasia. FISH detection of TERC amplification may provide an effective, noninvasive approach in conjunction with cytopathologic or histopathologic evaluation for differential diagnosis of low- and high-grade cervical disorders.

Modeling human papillomavirus and cervical cancer in the United States for analyses of screening and vaccination

Background

To provide quantitative insight into current U.S. policy choices for cervical cancer prevention, we developed a model of human papillomavirus (HPV) and cervical cancer, explicitly incorporating uncertainty about the natural history of disease.

Methods

We developed a stochastic microsimulation of cervical cancer that distinguishes different HPV types by their incidence, clearance, persistence, and progression. Input parameter sets were sampled randomly from uniform distributions, and simulations undertaken with each set. Through systematic reviews and formal data synthesis, we established multiple epidemiologic targets for model calibration, including age-specific prevalence of HPV by type, age-specific prevalence of cervical intraepithelial neoplasia (CIN), HPV type distribution within CIN and cancer, and age-specific cancer incidence. For each set of sampled input parameters, likelihood-based goodness-of-fit (GOF) scores were computed based on comparisons between model-predicted outcomes and calibration targets. Using 50 randomly resampled, good-fitting parameter sets, we assessed the external consistency and face validity of the model, comparing predicted screening outcomes to independent data. To illustrate the advantage of this approach in reflecting parameter uncertainty, we used the 50 sets to project the distribution of health outcomes in U.S. women under different cervical cancer prevention strategies.

Results

Approximately 200 good-fitting parameter sets were identified from 1,000,000 simulated sets. Modeled screening outcomes were externally consistent with results from multiple independent data sources. Based on 50 good-fitting parameter sets, the expected reductions in lifetime risk of cancer with annual or biennial screening were 76% (range across 50 sets: 69–82%) and 69% (60–77%), respectively. The reduction from vaccination alone was 75%, although it ranged from 60% to 88%, reflecting considerable parameter uncertainty about the natural history of type-specific HPV infection. The uncertainty surrounding the model-predicted reduction in cervical cancer incidence narrowed substantially when vaccination was combined with every-5-year screening, with a mean reduction of 89% and range of 83% to 95%.

Conclusion

We demonstrate an approach to parameterization, calibration and performance evaluation for a U.S. cervical cancer microsimulation model intended to provide qualitative and quantitative inputs into decisions that must be taken before long-term data on vaccination outcomes become available. This approach allows for a rigorous and comprehensive description of policy-relevant uncertainty about health outcomes under alternative cancer prevention strategies. The model provides a tool that can accommodate new information, and can be modified as needed, to iteratively assess the expected benefits, costs, and cost-effectiveness of different policies in the U.S.

Human papillomavirus testing and molecular markers of cervical dysplasia and carcinoma

Cervical cancer is the second most common cancer in women worldwide. Human papillomavirus (HPV) is the etiologic agent for the vast majority of premalignant and malignant lesions, and high-risk HPV types can be detected in almost all cases of cervical dysplasia and carcinoma. HPV testing has been widely adopted for the triage of patients after a cervical cytology screening test (Papanicolaou smear or liquid-based cervical cytology such as ThinPrep or SurePath) interpretation of atypical squamous cells of undetermined significance (ASCUS), and HPV testing is increasingly used for screening in conjunction with cervical cytology. Although cervical cytology is a highly effective screening test for cancer, it has limited specificity for clinically significant lesions in cases with low-grade cytologic abnormalities. Up to a quarter of all patients may have a false-negative result on the basis of cervical cytology testing alone. This review focuses on HPV testing methods and molecular markers and their clinical relevance. HPV testing and surrogate molecular markers of HPV infection (p16INK4a) may help identify cases that are associated with underlying high-grade premalignant or malignant lesions and may also reduce aggressive treatment of patients with low-grade lesions.

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 in the vaginal margins of radical hysterectomy in patients with carcinoma of the cervix: correlation with histology and human papillomavirus

This study was undertaken to evaluate the telomerase activity both in the tumor and in the vaginal margins of radical hysterectomy in patients with squamous cell carcinoma (SCC) of the cervix. Thirty-three patients with SCC of the cervix (study group) and 13 patients with uterine myoma (control group) were prospectively studied. Tissue samples were taken from the tumor or cervix, anterior vaginal margin (AVM), and posterior vaginal margin (PVM). The specimens were analyzed by histopathology, by a telomerase PCR-TRAP-ELISA kit, and by polymerase chain reaction using human papillomavirus (HPV) DNA. The telomerase activity was significantly higher in the tumor than in the benign cervix (P < 0.001). There was no difference in telomerase activity in the AVM and PVM in patients with cervical carcinoma compared to the control group. Telomerase activity was associated with the presence of histologic malignancy in the PVM of patients submitted to radical hysterectomy (P= 0.03). This association was not observed with the presence of HPV in AVM or PVM in the study group. Telomerase activity is a marker of histologic malignancy in patients with SCC of the cervix. There was no association between the telomerase activity and the presence of HPV in vaginal margins of patients submitted to radical hysterectomy.

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.

Immunocytochemistry in liquid-based cervical cytology: analysis of clinical use following a cross-sectional study

Cytological screening for cervical cancer is hampered by imperfect sensitivity and low inter-observer reproducibility. Human papillomavirus (HPV) testing lacks specificity as a primary screening method. Studies indicate that immunocytochemical detection of alterations caused by HPV in the host cells can optimise screening. Here, the potential of p16(INK4a) (cyclin-dependent kinase inhibitor p16) and MIB-1 (Ki-67 proliferation marker) as adjunct molecular markers for cervical lesions was investigated in a prospective, cross-sectional study of 500 samples in the framework of opportunistic screening in Flanders, Belgium. A consecutive series of 200 samples and 100 samples from the cytological categories ASC, LSIL and HSIL were investigated. Surepath samples were interpreted according to the Bethesda 2001 reporting system. HPV testing was done with MY09/MY11 consensus PCR. Immunocytochemistry for p16(INK4a) and MIB-1 was performed with an automated staining protocol. The number of immunoreactive cells/1,000 cervical cells was assessed. There was a higher mean number of p16(INK4A) and MIB-1 immunoreactive cells/1,000 cells in HSIL (4.06 +/- 1.93 and 11.13 +/- 2.83, respectively) compared to other cytological categories. Both markers showed a large spread in counts, for all categories. In cases of HSIL without immunoreactive cells for either marker, low cellularity and long-term storage in water were often the cause of false negativity. This study confirms that positive staining for p16(INK4a) and MIB-1 is highly correlated with presence of high-grade lesions. These markers could be used as adjuncts to increase the sensitivity of cytological screening as well as the specificity of the HPV test. However, clear methodological standards are needed for optimal performance of immunocytochemistry in a clinical setting.

Human papillomavirus genotype distribution in low-grade cervical lesions: comparison by geographic region and with cervical cancer

Low-grade squamous intraepithelial lesions (LSIL) associated with certain human papillomavirus (HPV) genotypes may preferentially progress to cervical cancer. HPV genotyping may thus have the potential to improve the effectiveness of screening programs and to reduce overtreatment. LSIL cases (n = 8,308) from 55 published studies were included in a meta-analysis. HPV genotype distribution was assessed by geographic region and in comparison with published data on cervical squamous cell carcinoma (SCC). HPV detection in LSIL was 80% in North America but less than 70% in other regions, most likely reflecting regional differences in LSIL diagnosis. Among 5,910 HPV-positive LSILs, HPV16 was the most common genotype (26.3%) followed by HPV31 (11.5%), HPV51 (10.6%), and HPV53 (10.2%). HPV-positive LSILs from Africa were 2-fold less likely to be infected with HPV16 than those in Europe, and HPV-positive LSILs from North America were more likely to be infected with HPV18 than those from Europe or South/Central America. Interpretation for rarer genotypes was hampered by variation in HPV testing methodology. SCC/LSIL prevalence ratios indicated that HPV16 was 2-fold and HPV18 was 1.5-fold more common in SCC than in HPV-positive LSIL, thus appearing more likely to progress than other high-risk genotypes (SCC/LSIL prevalence ratios between 0.05 and 0.85). HPV53 and HPV66 showed SCC/LSIL ratios of 0.02 and 0.01, respectively. HPV genotype distribution in LSIL differs from that in cervical cancer, highlighting the importance of HPV genotype in the risk of progression from LSIL to malignancy. Some regional differences in the relative importance of HPV genotypes in LSIL were noted.

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.

Screening for cervical cancer in the developing world

Cervical cancer remains the most common malignancy amongst females in countries of low income, mainly due to a lack of screening. Responsible factors are centred around inadequacies of the Pap smear: high cost; low sensitivity; the need of a laboratory with high human expertise; and a demanding logistic system for mass screening. No alternative screening method seems to be clearly advantageous. Although combinations of tests have higher sensitivities, they are complex, costly and associated with low specificities. Adding the problem of effective treatment, it seems that mass screening with adequate coverage of the population is an unreachable goal for many developing countries. The most promising development in the control of cervical cancer seems to be vaccination against the human papillomavirus, either as a preventative measure or for stimulating immunity in infected women.

Update on pathophysiologic mechanisms of human papillomavirus

PURPOSE OF REVIEW

The role of the human papillomavirus in the pathogenesis has been the subject of many publications in the recent literature. The physical state of the human papillomavirus and the role of chromosomal aneuploidy has been reported. This review discusses the recent pathological mechanisms described in the genesis of human papillomavirus-related disease.

RECENT FINDINGS

The mere presence of the human papillomavirus is not sufficient for the development of neoplasia. Genetic and other co-factors seem to be necessary for the expression of the invasive phenotype. The expression of human papillomavirus 16 E6-E7 oncogenes results in chromosomal aneuploidy, favouring the integration of high-risk human papillomavirus genomes into cellular chromosomes. The integration of human papillomavirus 16 may not always be required for the progression to the invasive phenotype unlike human papillomavirus 18 DNA. Such integration sites are randomly distributed over the whole genome. The genetic susceptibility of codon 98 of the fragile histadine triad has been elucidated.

SUMMARY

Various molecular mechanisms of human papillomavirus-associated neoplasia are discussed. The interaction between HIV and human papillomavirus are complex and favour the persistence and progression of cervical disease. Future research should pave the way for therapeutic vaccine development.