Nicolas Wentzensen

Type-Dependent Integration Frequency of Human Papillomavirus Genomes in Cervical Lesions

Chromosomal integration of high-risk human papillomavirus (HR-HPV) genomes is believed to represent a significant event in the pathogenesis of cervical cancer associated with progression from preneoplastic lesions to invasive carcinomas. This hypothesis is based on experimental data suggesting that integration-dependent disruption of HR-HPV E2 gene functions is important to achieve neoplastic transformation and on clinical data gathered by analyzing lesions induced by human papillomavirus (HPV) 16 and 18 that revealed integrated viral genome copies in the vast majority of cervical cancer cells. However, a substantial fraction of cervical cancers is associated with other HR-HPV types for which virtually no data concerning their integration status have been reported so far. Here, we compared integration frequencies of the five most common oncogenic HPV types (HPV16, 18, 31, 33, and 45) in a series of 835 cervical samples using a specific mRNA-based PCR assay (Amplification of Papillomavirus Oncogene Transcripts). Most precancerous lesions displayed exclusively episomal viral genomes, whereas 62% of the carcinomas had integrated viral genomes. However, the frequency of integrated HR-HPV genomes showed marked differences for individual HR-HPV types. HPV16, 18, and 45 were found substantially more often in the integrated state compared with HPV types 31 and 33. The analysis of the median age of patients with high-grade precancerous lesions and invasive cancers suggests that precancers induced by HPV types 18, 16, and 45 progress to invasive cervical cancer in substantially less time compared with precancers induced by HPV types 31 and 33. These findings suggest that integration of oncogenic HPV genomes in cervical lesions is a consequence rather than the cause of chromosomal instability induced by deregulated HR-HPV E6-E7 oncogene expression. Distinct HR-HPV types apparently provoke chromosomal instability in their host cells to a different extent than is reflected by their integration frequencies in advanced lesions and the time required for CIN 3 lesions to progress to invasive cancer.

Biomarkers in Cervical Cancer Screening

In industrialized countries, population wide cytological screening programs using the Pap test have led to a substantial reduction of the incidence of cervical cancer. Despite this evident success, screening programs that rely on Pap-stained cytological samples have several limitations. First, a number of equivocal or mildly abnormal test results require costly work up by either repeated retesting or direct colposcopy and biopsy, since a certain percentage of high grade lesions that require immediate treatment hide among these unclear test results. This work up of mildly abnormal or equivocal cytological tests consumes a large amount of the overall costs spent for cervical cancer screening. Improved triage of these samples might substantially reduce the costs. Cervical cancer is induced by persistent infections with oncogenic human papilloma viruses (HPV). While HPV infection is an indispensable factor, it is not sufficient to cause cancer. The majority of acute HPV infections induce low grade precursor lesions that are cleared spontaneously after several months in more than 90% of cases, and less than 10% eventually progress to high grade lesions or invasive cancer. Progression is characterized by the deregulated expression of the viral oncogenes E6 and E7 in infected basal and parabasal cells. Novel biomarkers that allow monitoring these essential molecular events in histological or cytological specimens are likely to improve the detection of lesions that have a high risk of progression in both primary screening and triage settings. In this review, we will discuss potential biomarkers for cervical cancer screening with a focus on the level of clinical evidence that supports their application as novel markers in refined cervical cancer screening programs.

A comprehensive analysis of HPV integration loci in anogenital lesions combining transcript and genome-based amplification techniques

Persistent infections with high-risk human papillomaviruses (HPVs) induce dysplastic lesions of the lower genital tract. Some of these lesions eventually progress to invasive cancers, particularly of the uterine cervix. In many advanced preneoplastic cervical lesions and most derived carcinomas, HPV genomes are found to be integrated into the host cell chromosomes. Although HPV integration seems to play an important role in the progression of cervical dysplasia, the underlying mechanisms are still unclear. To investigate the pathogenic role of genomic integration of HPV genomes in greater detail, we analysed integration sites of HPV16 and 18 genomes in 21 anogenital precancerous and cancerous lesions using a ligation-mediated chain reaction (DIPS) and the recently described amplification of papilloma virus oncogene transcripts (APOT) assay. On the genomic level, only singular integration events were observed in individual neoplastic cell clones. At many integration sites, a short overlap between HPV and genomic sequences was observed, suggesting that the integration of HPV genomes is mediated by nonhomologous sequence-specific recombination. APOT analysis revealed that the majority of integrated HPV genomes was actively transcribed. These data suggest that in the progression of cervical preneoplasia to invasive carcinomas, integration of viral genomes occurs only at single or few chromosomal loci in a given cell clone. Disruption of cellular genes might support malignant transformation in rare cases; however, it is not a pathogenic prerequisite. The main function of HPV integration seems to be the stabilization of oncogene transcription.

Characterization of viral-cellular fusion transcripts in a large series of HPV16 and 18 positive anogenital lesions.

Persistent high risk type human papillomavirus (HR–HPVs) infections induce dysplasia or cancer of the anogenital tract, most notably of the uterine cervix. The viral genome usually persists and replicates as an episomal molecule in early dysplasia, whereas in advanced dysplasia or cervical cancer HPV genomes are frequently integrated into the chromosomal DNA of the host cell. Previous studies suggested that modification of critical cellular sequences by integration of HPV genomes might significantly contribute to the neoplastic transformation of anogenital epithelia (insertional mutagenesis). This prompted us to characterize the integration loci of high risk HPV genomes in a large set of genital lesions. We amplified E6/E7 oncogene transcripts derived from integrated HPV16 and HPV18 genomes and characterized in detail the co-transcribed cellular sequences of 64 primary genital lesions and five cervical cancer cell lines. Database analyses of the cellular parts of these fusion transcripts revealed 51 different integration loci, including 26 transcribed genes (14 known genes, 12 EST sequences with unknown gene function). Seventeen sequences showed similarity to repetitive elements, and 26 sequences did not show any database match other than genomic sequence. Chromosomal integration loci were distributed over almost all human chromosomes. Although we found HPV sequences integrated into cancer related genes and close to fragile sites, no preferential site or integration motif could be identified. These data demonstrate that target directed insertional mutagenesis might occur in few HPV-induced anogenital lesions, however, it is rather the exception than the rule.

DNA Aneuploidy and Integration of Human Papillomavirus Type 16 E6/E7 Oncogenes in Intraepithelial Neoplasia and Invasive Squamous Cell Carcinoma of the Cervix Uteri

Purpose: Increasingly deregulated expression of the E6-E7 oncogenes of high-risk human papillomaviruses (HR-HPVs) has been identified as the major transforming factor in the pathogenesis of cervical dysplasia and derived cancers. The expression of these genes in epithelial stem cells first results in chromosomal instability and induces chromosomal aneuploidy. It is speculated that this subsequently favors integration of HR-HPV genomes into cellular chromosomes. This in turn leads to expression of viral cellular fusion transcripts and further enhanced expression of the E6-E7 oncoproteins. Chromosomal instability and aneuploidization thus seems to precede and favor integration of HR-HPV genomes. Experimental Design: To prove this sequential concept, we analyzed here the sequence of events of DNA aneuploidization and integration in a series of HPV-16-positive cervical dysplastic lesions and carcinomas. Eighty-five punch biopsies of HPV-16-positive cervical lesions (20 CIN1/2, 50 CIN3, and 15 CxCa) were analyzed for DNA ploidy by DNA flow cytometry and for integration of HPV E6/E7 oncogenes using the amplification of papillomavirus oncogene transcripts assay, a reverse transcription-PCR method to detect integrate-derived human papillomavirus oncogene transcripts. Results: DNA aneuploidy and viral genome integration were both associated with increasing dysplasia (P < 0.001, χ2 test for trend). In addition, DNA aneuploidy was associated with increased viral integration (P < 0.01, Fisher’s exact test). Nineteen of 20 (95%) lesions with integrated viral genomes had aneuploid cell lines; however, only 19 of 32 (59%) lesions with aneuploid cell lines had integrated viral genomes. Conclusions: These data support the hypothesis that aneuploidization precedes integration of HR-HPV genomes in the progression of cervical dysplasia. Accordingly, deregulated viral oncogene expression appears to result first in chromosomal instability and aneuploidization and is subsequently followed by integration of HR-HPV genomes in the affected cell clones.

Triage of women with ASCUS and LSIL cytology : Use of qualitative assessment of p16INK4a positive cells to identify patients with high-grade cervical intraepithelial neoplasia

The identification of a small percentage of high‐grade cervical intraepithelial neoplasias (HGCIN) among patients with minor cytological abnormalities (atypical squamous cells of undetermined significance [ASCUS] and/or low‐grade squamous intraepithelial lesions [LSIL] group) is a major problem in cytology‐based cervical cancer screening. The authors investigated the efficacy of p16INK4a as a biomarker to identify samples of patients with HGCIN among those with an ASCUS or LSIL result in Papanicolaou cytology.

High density of FOXP3-positive T cells infiltrating colorectal cancers with microsatellite instability.

High-level microsatellite instability (MSI-H) in colorectal cancer accounts for about 12% of colorectal cancers and is typically associated with a dense infiltration with cytotoxic CD8-positive lymphocytes. The role of regulatory T cells that may interfere with the hosts antitumoural immune response in MSI-H colorectal cancers has not been analysed yet. Using an antibody directed against the regulatory T-cell marker transcription factor forkhead box P3 (FOXP3), regulatory T cells were examined in 70 colorectal cancers with known MSI status (MSI-H, n=37; microsatellite stable, n=33). In MSI-H colorectal cancers, we found a significantly higher intraepithelial infiltration with FOXP3-positive cells (median: 8.5 cells per 0.25 mm2 vs 3.1 cells per 0.25 mm2 in microsatellite stable, P<0.001), and a significantly elevated ratio of intraepithelial to stromal infiltration (0.05 vs 0.01 in microsatellite stable, P<0.001). CD8-positive cell counts were related positively to the number of FOXP3-positive cells (Spearmans ρ=0.56 and 0.55, respectively). Our results show that the elevated number of CD8-positive lymphocytes found in MSI-H colorectal cancers is paralleled by an enhanced infiltration with CD8-negative FOXP3-positive cells. These data suggest that FOXP3-positive cells may play a role in the regulation of the immune response directed against MSI-H colorectal cancers at the primary tumour site.

Performance of p16INK4a-cytology, HPV mRNA, and HPV DNA testing to identify high grade cervical dysplasia in women with abnormal screening results

OBJECTIVE The prognostic value of dysplastic lesions of the uterine cervix cannot be adequately determined by Pap cytology alone. Detection of HPV DNA increases the diagnostic sensitivity. However, due to the very high prevalence of transient HPV infections, HPV DNA testing suffers from poor diagnostic specificity. Biomarkers that highlight the shift from self limited transient to potentially dangerous transforming HPV infections may improve the accuracy of cervical cancer screening. We evaluated HPV E6/E7 mRNA detection (APTIMA), p16(INK4a)-immunocytology (CINtec), and HPV DNA testing (HC2) to identify women with high grade cervical neoplasia in a disease-enriched cross-sectional cohort. METHODS Liquid based cytology specimens were collected from 275 patients. All assays were performed from these vials. Detection rates of each test were evaluated against conventional H&E based histopathology alone and stratified by p16(INK4a)-immunohistochemistry (IHC). RESULTS All assays yielded a high sensitivity for the detection of CIN3+ (96.4% (95% CI, 90.4-98.8) for HC2, 95.5% (89.2-98.3) for APTIMA and CINtec) and CIN2+ (91.5% (85.8-95.1) for HC2, 88.4% (82.3-92.7) for APTIMA, 86.6% (80.2-91.2) for CINtec). The specificity to detect high grade dysplasia was highest for CINtec p16(INK4a)-cytology (60.6% (52.7-68.0) in CIN3+ and 74.8% (65.5-82.3) in CIN2+), followed by APTIMA (56.4% (48.4-64.0) in CIN3+ and 71.2% (61.7-79.2) in CIN2+) and HC2 (49.1% (41.3-56.9) in CIN3+ and 63.4% (53.7-72.1) in CIN2+). All tests had higher sensitivity using p16(INK4a)-IHC-positive CIN2+ lesions as endpoint. CONCLUSIONS Biomarkers that detect HPV induced dysplastic changes in the transforming stage are promising tools to overcome the current limitations of cervical cancer screening.

Characterization of humoral immune responses against p16, p53, HPV16 E6 and HPV16 E7 in patients with HPV-associated cancers

The cellular tumor suppressor p16 is strongly overexpressed in cervical cancers and precancers. We have previously demonstrated that infiltrating T lymphocytes reactive against p16 can be found in cervical cancer patients. Here, we analyzed whether p16 induces humoral immune responses. Sera of patients with cervical cancer, oropharyngeal cancer, colorectal cancer and autoimmune disease were included. A total of 919 sera were analyzed, including 486 matched sera from a cervical cancer case control study. p16 antibodies were analyzed in Western blot and a newly developed peptide ELISA covering the complete p16 protein. In addition, a Luminex‐based multiplex assay was used for simultaneous detection of antibodies directed against p16, p53, HPV16 E6 and HPV16 E7. In all entities, only low p16 antibody reactivity was observed. Epitope mapping revealed 2 predominant epitope regions of the p16 protein. No significant difference in p16 antibody frequency (OR = 0.9; 95% CI = 0.6–1.3) and p53 antibody frequency (OR = 0.6; 95% CI = 0.3–1.2) was found between patients and healthy controls in the cervical cancer case control study. Antibodies against the HPV16 oncoproteins E6 and E7 were detected more frequently in cervical cancer patients when compared with healthy controls (E6 OR = 27.8; 95% CI = 11.1–69.7, E7 OR = 5.7; 95% CI = 2.9–11.1). In conclusion, despite the strong expression of p16 and the observed induction of cellular immune responses, antibody reactivity against p16 was observed only at very low levels independent of the disease background.

A Study of Genotyping for Management of Human Papillomavirus-Positive, Cytology-Negative Cervical Screening Results

ABSTRACT The effective management of women with human papillomavirus (HPV)-positive, cytology-negative results is critical to the introduction of HPV testing into cervical screening. HPV typing has been recommended for colposcopy triage, but it is not clear which combinations of high-risk HPV types provide clinically useful information. This study included 18,810 women with Hybrid Capture 2 (HC2)-positive, cytology-negative results and who were age ≥30 years from Kaiser Permanente Northern California. The median follow-up was 475 days (interquartile range [IQR], 0 to 1,077 days; maximum, 2,217 days). The baseline specimens from 482 cases of cervical intraepithelial neoplasia grade 3 or cancer (CIN3+) and 3,517 random HC2-positive noncases were genotyped using 2 PCR-based methods. Using the case-control sampling fractions, the 3-year cumulative risks of CIN3+ were calculated for each individual high-risk HPV type. The 3-year cumulative risk of CIN3+ among all women with HC2-positive, cytology-negative results was 4.6%. HPV16 status conferred the greatest type-specific risk stratification; women with HC2-positive/HPV16-positive results had a 10.6% risk of CIN3+, while women with HC-2 positive/HPV16-negative results had a much lower risk of 2.4%. The next most informative HPV types and their risks in HPV-positive women were HPV33 (5.9%) and HPV18 (5.9%). With regard to the etiologic fraction, 20 of 71 cases of cervical adenocarcinoma in situ (AIS) and adenocarcinoma in the cohort were positive for HPV18. HPV16 genotyping provides risk stratification useful for guiding clinical management; the risk among HPV16-positive women clearly exceeds the U.S. consensus risk threshold for immediate colposcopy referral. HPV18 is of particular interest because of its association with difficult-to-detect glandular lesions. There is a less clear clinical value of distinguishing the other high-risk HPV types.