Relationship between telomerase activation and HPV 16/18 oncogene expression in squamous intraepithelial lesions and squamous cell carcinomas of the uterine cervix

A clinicopathological and molecular analysis of cervical carcinomas with basaloid features

AIMS

To investigate the relationship between adenoid basal carcinoma (ABC), adenoid cystic carcinoma (ACC) and squamous cell carcinoma (SCC) in the uterine cervix.

METHODS AND RESULTS

We analysed the clinicopathological and molecular features in two pure ABCs, 15 SCCs with ABC-/ACC-like features and seven basaloid SCCs (BSCCs) by chart review, immunohistochemistry, human papillomavirus (HPV) RNA in-situ hybridisation and fluorescence in-situ hybridisation. All patients were alive with no evidence of disease, except for one patient with ACC-like features who died of disease at 18 months post diagnosis. The mixed carcinomas comprised variable SCCs and ABC-/ACC-like components displaying vague transitional zones. All components consistently showed diffuse p16, p63 and SOX2, variable cytokeratin (CK)7 and CK17 and rare Ber-EP4 and MYB expression; there was a substantially lower Ki67 index in pure ABCs and the ABC-like components. The ACC-like components showed no myoepithelial differentiation (SMA, calponin and S100) and MYB gene fusions. CK7, CK17 and Ber-EP4 were characteristically stronger in BSCCs than in the mixed carcinomas (P < 0.01). High-risk HPV (HR-HPV) E6/E7 mRNA was detected in 12 mixed carcinomas and seven BSCCs, but not in pure ABCs. The HR-HPV mRNA expression was higher in the SCC components and BSCCs than in the ABC-like components of mixed carcinomas (P < 0.05).

CONCLUSIONS

The ACC-like components in mixed carcinomas probably represent the morphological mimics of salivary ACCs. ABC-like components may be the potential precursor of the ACC-like and SCC components. HR-HPV oncogenes may play a role in the pathogenesis of SCCs with ABC-/ACC-like features.

Peroxiredoxin 3 is a novel marker for cell proliferation in cervical cancer

Although peroxiredoxin 3 (Prx3) has been reported to be involved in cervical cancer (CC) carcinogenesis, the significance of Prx3 in CC progression remains unclear. The present study was conducted to investigate the expression features of Prx3 to better understand the mechanism of tumor growth and invasion. Sixty-eight patients with invasive squamous cervical cancer were included in the present study. The status of human papillomavirus (HPV) infection was detected by hybridization and quantitative real-time polymerase chain reaction (qRT-PCR). Immunohistochemistry was performed on paraffin-embedded sections using monoclonal antibodies against Prx3 and Ki67. All samples were positive for high-risk HPV, among which fifty-six samples were positive for HPV16, seven for HPV18 and five for HPV33. The expression of HPV16 E6/E7 was significantly higher in cancer areas compared to the adjacent normal epithelial tissuses. The positive cells for Prx3 and Ki67 were significantly higher in cancer cells compared to normal epitheliums and the staining pattern of Prx3 was consistent with that of Ki67 (Pearson's correlation coefficient was 0.801, P= 0.000). The upregulation of Prx3 might be a protective response to oxidative stress in the cancer microenvironment. The expression consistency of Prx3 and Ki67 suggests Prx3 to be a potential marker for cell proliferation of CC.

A study of association between expression of hOGG1, VDAC1, HK-2 and cervical carcinoma

Background

Human 8-oguanine glycosylase 1(hOGG1), voltage-dependent anion channel 1(VDAC1), hexokinase 2(HK-2), represented the process of oxidative DNA damage, cell apoptosis and glycolysis, respectively. This study aims to explore the association between expression of hOGG1, VDAC1, HK-2 and cervical carcinoma.

Methods

A case-control study was conducted. 65 cervical biopsy samples consist of 20 control and 45 cases. The expression of hOGG1, VDAC1 and HK-2 were examined with immunohistochemistry(IHC), immunolabeling was evaluated with stereological cell counts.

Results

The data showed that the positive proportion of hOGG1 and HK-2 in the case group was higher than that of the control group (P < 0.05). Further, there was an increasing trend for the positive proportion and expression degree of hOGG1 and HK-2 from Control, Mild cervical carcinoma (MCC), Intermediate cervical carcinoma(ICC) to Severe cervical carcinoma(SCC) in order (P < 0.05). To VDAC1, the significant result was not obtained.

Conclusions

The results suggested that there was a close association between expression of hOGG1, HK-2 and cervical cancer. hOGG1 and HK-2 might play a key role at the early stage of cervical cancer, and the findings of hOGG1 and HK-2 should be considered as a significant biomarker at the early stage of cervical cancer.

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.

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.

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.

Promoter hypermethylation of tumor suppressor genes in urine from patients with cervical neoplasia

We examined the feasibility of using detection of high-risk human papillomavirus (HPV) DNA in combination with the presence of aberrantly methylated genes (DAPK1, RARB, TWIST1, and CDH13) for urine-based cervical cancer screening. Urine samples from 129 Senegalese women, aged 35 years or older, 110 with (same day) biopsy-proven cervical neoplasia [cervical intraepithelial neoplasia grade 1 (CIN-1): n = 9; CIN-2-3/carcinoma in situ (CIS): n = 29; invasive cervical cancer (ICC): n = 72], and 19 without cervical neoplasia on biopsy were examined. Hypermethylation of at least one of the four genes identified 62% of ICC and 28% of CIN-2-3/CIS and was present in only 4% of CIN-1 or normal urines. High-risk HPV DNA was detected in urine in 70% of those with biopsy-proven ICC, 59% of those with CIN-2-3/CIS on biopsy, 44% of those with CIN-1 on biopsy, and only 11% of women negative for cervical neoplasia on biopsy. Urine-based detection of either high-risk HPV or hypermethylation of any of the four genes identified 84% of ICC, 64% of CIN-2-3/CIS, 44% of CIN-1, but only 19% of women negative for cervical neoplasia. The sensitivity for detection of CIN-2-3/CIS/ICC by high-risk HPV DNA or aberrant DNA methylation of four genes seems to be comparable to that of an exfoliated cervical cytology. This study shows the potential feasibility of using molecular markers detected in urine for cervical cancer screening.

Integration of the HPV16 genome does not invariably result in high levels of viral oncogene transcripts

Virus integration into the host genome is a characteristic step during cervical carcinogenesis. Experimental data provide evidence that integration could result in increased levels of oncogene (E6/E7) transcripts. This is the first study in which the level of viral transcripts is correlated to the physical state of the viral genome in cervical intraepithelial neoplasia (CIN) and cervical carcinomas (CxCa). Using the APOT-assay integrate-derived transcripts only were detected in 3/28 (11%) CIN and in 28/55 (51%) carcinomas, respectively. The remaining biopsies contained either episome-derived transcripts only or both mRNA species. SybrGreen real time reverse transcriptase-PCR assays were used to quantify viral gene expression for (i) all transcripts initiated from p97, (ii) full-length E6, (iii) E6*I and (iv) E5 transcripts. E6/E7 transcript levels showed a broad distribution but similar median values irrespective of histopathological grading and physical state of the viral genome. Biopsies with integrate-derived transcripts only generally lacked E5-specific mRNA. Our data do not support the hypothesis that HPV integration invariably results in high levels of oncogene transcripts. Instead, constitutive expression of oncogene transcripts rather than the level of expression appears to be decisive for transformation and the maintenance of the malignant phenotype.

Accuracy of telomerase in cervical lesions: a systematic review

The detection of telomerase activity in cervix may provide information on cervical carcinogenesis and may be a marker to monitor cervical intraepithelial neoplasia transition. A quantitative systematic review was performed to estimate the accuracy of telomerase assay in cervical lesions. Studies that evaluated the telomerase test (telomerase repeated amplification protocol) for the diagnosis of cervix lesions and compared it to paraffin-embedded sections as the diagnostic standard were included. Ten studies were analyzed, which included 1069 women. The diagnostic odds ratio (DOR) for a positive telomerase test for low-grade squamous intraepithelial lesions (Lo-SIL) vs normal or benign lesions was 3.2 (95% CI, 1.9-5.6). The DOR for a positive telomerase test for high-grade squamous intraepithelial lesions (Hi-SIL) vs Lo-SIL, normal or benign lesions was 5.8 (95% CI, 3.1-10). For cervix cancer vs Hi-SIL, the DOR for a positive telomerase test was 8.1 (95% CI, 3.2-20.3) and for cervix cancer vs Lo-SIL, normal or benign lesions, it was 40.9 (95% CI, 18.2-91). Our data support the current hypothesis that telomerase may activate an early event in cervical carcinogenesis that could be associated with the initiation and progression of cervical lesions.

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.

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.

Genomic integration of oncogenic HPV and gain of the human telomerase geneTERC at 3q26 are strongly associated events in the progression of uterine cervical dysplasia to invasive cancer

Recently proposed events associated with the progression of cervical intraepithelial neoplasia (CIN) 2/3 to cervical carcinoma include integration of human papillomavirus (HPV) into the host genome, genomic instability, and an increase in chromosome 3q copy number. In particular, the gene coding for the RNA component of telomerase (TERC) at 3q26 has been implicated as a possible candidate gene. Since it is not known to date how these events are temporally related during cervical carcinogenesis, the aim of the present study was to assess the correlation between TERC gene copy number and the physical status of HPV during progression in cervical neoplasia. Solitary precursor lesions of the uterine cervix (CIN 2/3, n = 17), lesions associated with a micro-invasive carcinoma (CIN 3&mCA, n = 13), and advanced invasive carcinomas (invCA, n = 7) were analysed by fluorescence in situ hybridization (FISH) to determine the physical status of the virus and TERC gene copy number. The TERC gene was increasingly gained with progression of CIN 2/3 (3 of 17) through CIN 3&mCA (7 of 13) to invCA (5 of 7). In the lesions exhibiting gain of TERC, the virus was predominantly integrated. This was seen in eight of ten diploid lesions, indicating that these events can occur prior to aneuploidization and are strongly associated with the progression of CIN 3 to mCA and invCA (p < 0.001). With progression to carcinoma, a number of these lesions show polyploidization, resulting in aneuploidy and high TERC gene copy numbers. In conclusion, genomic integration of oncogenic HPV and gain of the human telomerase gene TERC appear to be important associated genetic events in the progression of uterine cervical dysplasia to invasive cancer.

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.

Detection of human telomerase RNA in the tumour-surrounding mucosa of bladder carcinomas as a marker for premalignant transformation

OBJECTIVES

To investigate tumour tissue and non-malignant tumour-surrounding bladder mucosa (NTSBM) for expression of human telomerase RNA (hTR) as a possible marker for premalignant transformation of urothelial cells.

MATERIAL AND METHODS

From 67 patients with superficial transitional cell carcinoma (TCC), sections with representative tumour tissue and NTSBM were selected for evaluation. Sections with moderate or severe dysplasia were omitted from evaluation. hTR expression was detected with in situ hybridization using a 35S-UTP-labelled riboprobe, and analysed semiquantitatively by counting the hybridization signals.

RESULTS

In 45 of the 67 patients hTR expression was moderate or strong in tumour tissue, and in 20 hTR expression was moderate or strong in NTSBM. Moderate or strong hTR expression was detected in the NTSBM from 19 of 60 patients with pTa/pT1 tumours. Of the 56 patients who were treated conservatively, eight had tumour recurrence, of whom five had moderate or strong hTR expression in the TSBM, compared with only 14 of 48 patients without tumour recurrence.

CONCLUSION

Detecting hTR expression and the morphological distribution of hTR hybridization signals in NTSBM by in situ hybridization might indicate premalignant alterations involved in tumour recurrence.

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.

Evaluation of expression of apoptosis-related proteins and their correlation with HPV, telomerase activity, and apoptotic index in cervical cancer

OBJECTIVE

The aim of this study was to examine the expression of apoptosis-related proteins in cervical cancer, and investigate their correlation with the apoptotic index (AI), telomerase activity, human papilloma virus (HPV) infection and clinicopathological characteristics.

METHODS

Fifty cervical cancer samples and 20 normal cervical tissues were assessed for the protein expression of survivin, Bcl-2, Cox-2, p53 and p73 by immunohistochemistry. HPV DNA was detected by PCR, telomerase activity by PCR-ELISA, and AI by TUNEL assay.

RESULTS

46/50 cervical tumors (92%) showed an increased telomerase activity as compared to 3/20 (15%) controls. 45/50 (90%) cervical tumors were positive for HPV, of which 30 were HPV-16 positive and 5 were HPV-18 positive. 24/50 (48%) tumors were positive for survivin, 14 (28%) for Bcl-2, 13 (26%) for Cox-2, 19/45 (42%) for p73, 10/45 (24%) for p53. Telomerase activity was highest in tumors with the poorest grade. A positive correlation was seen between survivin and Bcl-2, survivin and tumor stage, Bcl-2 and Cox-2, p73 and p53 and p73 and the AI. Despite the overexpression of various antiapoptotic proteins, no significant difference was observed in the AI between tumors and controls.

CONCLUSIONS

Since deregulation of the apoptotic pathway appears to occur in cervical cancer, some apoptosis-related proteins could be assessed as potential markers for progression/prognosis in cervical cancer. Additionally, newer proteins such as p73 may play a compensatory role for the nonfunctional proteins such as p53.

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.

Cervical epithelial cells transduced with the papillomavirus E6/E7 oncogenes maintain stable levels of oncoprotein expression but exhibit progressive, major increases in hTERT gene expression and telomerase activity

Cervical carcinoma cells display high telomerase activity and usually contain and express integrated copies of the human papillomavirus (HPV) genome. Recent studies have demonstrated that the E6 oncogene of malignancy-associated HPVs increases cellular telomerase activity, predominantly via transcriptional activation of the catalytic subunit of telomerase, hTERT. To examine the relationship between E6 oncoprotein expression and telomerase expression during cellular immortalization, we transduced primary human cervical epithelial cells with the HPV E6/E7 genes and monitored temporal changes in viral oncoprotein expression, cellular hTERT RNA expression, and cellular telomerase activity. Quantitation of the individual E6 and E7 proteins, using a newly developed immunoprecipitation/immunoblotting technique, demonstrated that both oncoproteins were expressed at stable levels during successive passages of cervical cells. In contrast, the levels of hTERT mRNA and telomerase activity increased progressively and dramatically during passaging. Late-passage immortalized cells (passage 30) showed a 25-fold increase in hTERT mRNA and a 300-fold increase in telomerase activity compared to early-passage (passage 4) cells. Thus, neither hTERT mRNA expression nor telomerase activity are directly proportional to the level of E6 oncoprotein, indicating that E6 is not the sole determinant of the high levels of telomerase in cervical cells during immortalization.

Analysis of telomerase as a diagnostic biomarker of cervical dysplasia and carcinoma

Telomerase expression is a potentially important marker of high-grade cervical dysplasia and squamous cell carcinoma (SCC). The routine practice of cervical cytology is limited by problems of false negative diagnoses as well as by poor specificity for clinically significant lesions in patients with low-grade cytologic abnormalities. Telomerase is widely expressed in most SCCs as well as in a high proportion of high-grade squamous intraepithelial lesions. Histochemical studies have confirmed that telomerase is expressed in the lower portions of normal or metaplastic squamous mucosa but that telomerase positive cells extend into the upper epithelial layers in cases of high-grade dysplasia. Since the cervical smear samples the uppermost cell layers of the cervical mucosa, but does not normally include cells derived from the lower layers of the squamous mucosa, the detection of telomerase in exfoliated cells of the cervical smear may have specificity for clinically significant lesions. The analysis of hTR, hTERT, and telomerase activity are complicated by a number of technical factors that may lead to either false negative or false positive test results. Thus, the practical application of telomerase analysis as a diagnostic adjunct for cervical cytopathology may depend on the development of more reliable and sensitive assay systems, possibly formatted for cytochemical applications.