Human Papillomavirus Integration Sites Research Articles

HPV DNA integration site as proof of the origin of ovarian metastasis from endocervical adenocarcinoma: three case reports

BackgroundMost endocervical adenocarcinomas are human papillomavirus (HPV)-related cancers associated with p16 immunostaining. Ovarian metastasis from cervical cancer is a rare phenomenon, the mechanism of dissemination remains unclear. The diagnosis of metastasis may be difficult to establish when the ovarian neoplasm presents features consistent with primary tumor. Immunohistochemical expression of p16 in ovarian tumors can guide the diagnosis of metastasis from HPV-related cervical cancer, but p16 positivity is nonspecific. Identical HPV genotype in the paired endocervical and ovarian tumors is a better marker for cervical origin, which may also be confirmed by identical HPV integration site.Case presentationTwo women presented with HPV18 cervical adenocarcinoma. No signs of disease were visible on MRI after treatment. After several years of follow-up, mucinous ovarian tumors were discovered in both patients. Molecular analyses showed that the ovarian lesions were HPV18-positive; indicating a primary cervical origin. A third woman was diagnosed with grade 1 ovarian endometrioid carcinoma with no peritoneal carcinomatosis. Final histological examination and HPV genotyping revealed HPV18-related in situ endometrioid adenocarcinoma in the endocervix and HPV18-related invasive endometrioid adenocarcinoma in the endometrium and both ovaries. Additional molecular analyses performed in two patients identified the same HPV integration sites in both the ovarian and cervical tumors, confirming that the ovarian mass was a metastasis from the cervical adenocarcinoma.ConclusionWe report three new cases of ovarian neoplasia in which the diagnosis of metastasis from cervical cancer was supported by the same HPV genotype and the same integration site in the paired cervical and ovarian tumors. To our knowledge, this is the first report of molecular evidence of the cervical origin of an ovarian metastasis. HPV screening should be performed in ovarian tumors for all patients with history of cervical neoplasia.

Single-cell whole-genome sequencing identifies human papillomavirus integration in cervical tumour cells prior to and following radiotherapy.

Single-cell sequencing technology is a promising systematic and comprehensive approach to delineate clonal associations between cells. The present study collected 13 and 12 cervical cells from fresh tumour tissue prior to and following radiotherapy, respectively, from a 46-year-old female patient with exogenous-type cervical carcinoma. Next, single-cell whole-genome sequencing analysis was performed on each cell. Examination revealed that normal cells could be clearly distinguished from tumour cells among the 25 cells. Tumour cells prior to and following radiotherapy almost represented two independent clones, with the main subpopulation prior to radiotherapy being killed and the minor subpopulation prior to radiotherapy becoming the main subpopulation following radiotherapy. A human papillomavirus (HPV) integration site was detected in POU class 5 homeobox 1B (POU5F1B) in tumour cells following radiotherapy, which has been reported to be a frequent HPV integration site in cervical carcinoma. These results indicate that tumour cells with HPV integration in POU5F1B survive radiotherapy, and that tumour cells prior to and following radiotherapy exhibit distinct characteristics.

Mapping of microRNAs related to cervical cancer in Latin American human genomic variants

Background: MicroRNAs are related to human cancers, including cervical cancer (CC), which is mainly caused by human papillomavirus (HPV) infection. In 2012, approximately 70000 cases and 28000 deaths from this cancer were registered in Latin America according to GLOBOCAN reports. The most frequent genotype worldwide is HPV-16. The main molecular mechanism of HPV in CC is related to integration of viral DNA into the hosts’ genome. However, the different variants in the human genome can result in different integration mechanisms, specifically involving microRNAs (miRNAs). Methods: miRNA sequences associated with CC and four human genome variants from Latin American populations were obtained from miRBase and the 1000 Genomes Browser, respectively. HPV integration sites near cell cycle regulatory genes were identified. miRNAs were mapped on human genomic variants. miRSNPs (single nucleotide polymorphisms in miRNAs) were identified in the miRNA sequences located at HPV integration sites on the human genomic Latin American variants. Results: Two hundred seventy-two miRNAs associated with CC were identified in 139 reports from different geographic locations. By mapping with the Blast-Like Alignment Tool (BLAT), 2028 binding sites were identified from these miRNAs on the human genome (version GRCh38/hg38); 42 miRNAs were located on unique integration sites; and miR-5095, miR-548c-5p and miR-548d-5p were involved with multiple genes related to the cell cycle. Thirty-seven miRNAs were mapped on the human Latin American genomic variants (PUR, MXL, CLM and PEL), but only miR-11-3p, miR-31-3p, miR-107, miR-133a-3p, miR-133a-5p, miR-133b, miR-215-5p, miR-491-3p, miR-548d-5p and miR-944 were conserved. Conclusions: 10 miRNAs were conserved in the four human genome variants, and in the remaining 27 miRNAs, substitutions, deletions or insertions were observed in the nucleotide sequences. This variability can imply differentiated mechanisms towards each genomic variant in human populations, relative to specific genomic patterns and geographic features. These findings may be decisive in determining susceptibility to the development of CC. Further identification of cellular genes and signalling pathways involved in CC progression could lead to the development of new therapeutic strategies based on miRNAs.

Next generation sequencing and its applications in HPV-associated cancers.

Approximately 18% of all human cancers have a viral etiology, and human papillomavirus (HPV) has been identified as one of the most prevalent viruses that plays causative role in nearly all cervical cancers and, in addition, in subset of head and neck, anal, penile and vulvar cancers. The recent introduction of next generation sequencing (NGS) and other omics approaches have resulted in comprehensive knowledge on the pathogenesis of HPV-driven tumors. Specifically, these approaches have provided detailed information on genomic HPV integration sites, disrupted genes and pathways, and common and distinct genetic and epigenetic alterations in different human HPV-associated cancers. This review focuses on HPV integration sites, its concomitantly disrupted genes and pathways and its functional consequences in both cervical and head and neck cancers. Integration of NGS data with other omics and clinical data is crucial to better understand the pathophysiology of each individual malignancy and, based on this, to select targets and to design effective personalized treatment options.

Tandemly Integrated HPV16 Can Form a Brd4-Dependent Super-Enhancer-Like Element That Drives Transcription of Viral Oncogenes.

ABSTRACTIn cancer cells associated with human papillomavirus (HPV) infections, the viral genome is very often found integrated into the cellular genome. The viral oncogenes E6 and E7 are transcribed from the viral promoter, and integration events that alter transcriptional regulation of this promoter contribute to carcinogenic progression. In this study, we detected highly enriched binding of the super-enhancer markers Brd4, MED1, and H3K27ac, visible as a prominent nuclear focus by immunofluorescence, at the tandemly integrated copies of HPV16 in cells of the cervical neoplasia cell line W12 subclone 20861. Tumor cells are often addicted to super-enhancer-driven oncogenes and are particularly sensitive to disruption of transcription factor binding to the enhancers. Treatment of 20861 cells with bromodomain inhibitors displaced Brd4 from the HPV integration site, greatly decreased E6/E7 transcription, and inhibited cellular proliferation. Thus, Brd4 activates viral transcription at this integration site, and strong selection for E6/E7 expression can drive the formation of a super-enhancer-like element to promote oncogenesis.

Abstract 1515: Identification and characterization of HPV-host fusion transcripts in HNSCCs

Abstract Introduction Head and neck squamous cell carcinoma (HNSCC) is the sixth most incident cancer worldwide. Human papillomavirus (HPV) is implicated in at least 70% of oropharyngeal squamous cell carcinomas in the US. HPV genomic integration events are a likely critical step in progression to cancer and occur as a consequence of HPV oncogene-induced chromosomal instability. The majority of viral integration events in the human genome appear to occur within or near genic regions. Identified HPV integration events in HNSCC were associated with alterations in DNA copy number, mRNA transcript abundance and splicing, and inter-/intrachromosomal rearrangements. Materials and methods We analyzed 84 HPV-positive HNSCC samples collected at the University of Michigan (18 tumors) and from The Cancer Genome Atlas (66 tumors). We used VirusSeq software for detection of integration events. Integrations were evidenced by host-virus fusion transcripts in RNA-seq, considering only breakpoints supported by at least four discordant read pairs and at least one junction spanning read. Results We identified 50 integration-positive tumors, which consisted of 41 with HPV16, one tumor with HPV18, 5 tumors with HPV33 and 3 with HPV35. We found an overall 271 breakpoints of integration within or near 83 human genes. Fusion virus-host transcripts with breakpoints within E6 and E7 HPV oncogenes were more common (59.3%) compared with breakpoints into other viral genes: E1 and E2 (19%), E4 and E5 (16.8%), L1 and L2 (4.7%). The detected viral integration events were widespread across the human genome with a few hotspots of recurrent integrations in genic regions at 1p36, 9p24, and 13p22. After accounting for regions covered by the data, we did not find an association of integration sites with aphidicolin-induced common fragile sites (CFSs), as observed for HPV integration sites in cervical cancer. Analysis of the protein interaction network constructed from the 83 host genes harboring viral integrants showed that 56 of them were linked into a highly connected sub-network with direct interactions. ETS2, TP63, FOXA1, CTGF and KLF5 were hubs in this network. The genes were statistically enriched for cancer genes known as important in “Head and Neck Neoplasms”(p = 1.74E-11). Conclusion HPV integration events in HNSCC are largely different from those common to cervical cancers. While TP63 appears to be a recurrent target in both cervical cancer and HNSCC, HNSCCs have a surprisingly high percent of integration events in known HNSCC-related genes. Overall, our results suggest that there is strong selective pressure for integration events that occur in HNSCC relevant genes. Citation Format: Lada A. Koneva, Yanxiao Zhang, Pelle Hall, Shama Virani, Alisha Virani, Thomas E. Carey, Laura S. Rozek, Maureen A. Sartor. Identification and characterization of HPV-host fusion transcripts in HNSCCs. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1515.

Comprehensive mapping of the human papillomavirus (HPV) DNA integration sites in cervical carcinomas by HPV capture technology.

Integration of human papillomavirus (HPV) DNA into the host genome can be a driver mutation in cervical carcinoma. Identification of HPV integration at base resolution has been a longstanding technical challenge, largely due to sensitivity masking by HPV in episomes or concatenated forms. The aim was to enhance the understanding of the precise localization of HPV integration sites using an innovative strategy. Using HPV capture technology combined with next generation sequencing, HPV prevalence and the exact integration sites of the HPV DNA in 47 primary cervical cancer samples and 2 cell lines were investigated. A total of 117 unique HPV integration sites were identified, including HPV16 (n = 101), HPV18 (n = 7), and HPV58 (n = 9). We observed that the HPV16 integration sites were broadly located across the whole viral genome. In addition, either single or multiple integration events could occur frequently for HPV16, ranging from 1 to 19 per sample. The viral integration sites were distributed across almost all the chromosomes, except chromosome 22. All the cervical cancer cases harboring more than four HPV16 integration sites showed clinical diagnosis of stage III carcinoma. A significant enrichment of overlapping nucleotides shared between the human genome and HPV genome at integration breakpoints was observed, indicating that it may play an important role in the HPV integration process. The results expand on knowledge from previous findings on HPV16 and HPV18 integration sites and allow a better understanding of the molecular basis of the pathogenesis of cervical carcinoma.

Abstract 2184: Gene expression analysis of human papillomavirus positive head and neck cancer primary tumor samples reveals two distinct subgroups

Abstract Introduction: Human Papillomavirus (HPV) infection is recognized as a major cause for an increasing percent of oropharyngeal squamous cell carcinomas (OPSCC). Patients with HPV-induced OPSCC have a better prognosis than those who are HPV-negative, which implies distinct molecular mechanisms. However, predicting prognosis with the HPV-positive population remains elusive. In this study, we aimed to characterize molecular aspects of HPV expression, HPV integration, and host gene expression to later correlate with survival and recurrence as those data become available for our study population. Materials and methods: Thirty-six primary head and neck SCC (HNSCC) tumor samples were collected between 2011-2013 at University of Michigan hospital, of which 18 were determined to be HPV+ (type16, 18 or 35). Paired-end RNA-Seq libraries were generated using Illumina HiSeq for all samples. The sequences were aligned to both the human and HPV genome. Gene expression levels were quantified for both human and HPV genes using TopHat2 and HTSeq, and HPV integration events were determined using Virus-seq. Results: Hierarchical clustering of the gene expression levels showed three distinct clusters among the samples. The HPV- samples were first separated from the HPV+ samples, and then there were two robust subgroups within the HPV+ samples. Subsequent analysis revealed one subgroup had significantly higher HPV expression levels than the other (p-value: 0.03; Wilcoxon test). The subgroups were also highly correlated with HPV-integration status (8 of the 16 tumors had at least one identified HPV integration event). Differentially expressed genes between HPV-integration positive and negative samples were found to be enriched for interesting pathways, including “keratinocyte differentiation”, “cell adhesion” and “growth factor binding”, suggesting possible differences in carcinogenesis We also examined the HPV integration sites and found the majority of them were transcription factors. These also include several cancer-related genes, such as “BIRC3”, “CD274” and “PBX1”. One gene, KLF12, contained an integration event in one of our tumors and in one of the 36 HPV+ tumors from The Cancer Genome Atlas (TCGA). Network analysis of the genes harboring an integration event in our population or the TCGA HNSCC population (38 total genes) revealed interactions around p63 and ETS. Conclusion: Our data is an important addition to TCGA HNSCC cohort data, because as opposed to TCGA, we did not enforce selection bias towards large tumor size. With our data, we identified two distinct HPV+ subgroups characterized by RNA-Seq expression levels and strongly correlated with HPV viral expression levels and integration status. A significant portion of the HPV+ tumors (50%) had integrated HPV genome, implying important oncogenic potentials for integration events. Citation Format: Yanxiao Zhang, Lada A. Koneva, Shama Virani, Alisha Virani, Katie M. Rentschler, Thomas E. Carey, Laura S. Rozek, Maureen A. Sartor, the University of Michigan Head and Neck SPORE. Gene expression analysis of human papillomavirus positive head and neck cancer primary tumor samples reveals two distinct subgroups. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2184. doi:10.1158/1538-7445.AM2015-2184

Oncogenic human papillomavirus imposes an instructive pattern of DNA methylation changes which parallel the natural history of cervical HPV infection in young women

The contribution of early virus-induced epigenetic changes to human papillomavirus (HPV)-associated carcinogenesis is poorly understood. Using genome-wide methylation array profiling and a cell-based model, which supports replication of HPV episomes, we found that transfection of primary human foreskin keratinocytes with episomal forms of high-risk HPV types was followed by upregulation of the DNA methyltransferases, DNMT1 and DNMT3B, and changes in the methylation status of cellular genes many of which are reported to be differentially methylated in cervical neoplasia. HPV16- and HPV18-associated changes were not randomly distributed across the genome, but clustered at specific chromosomal locations which mapped on to known HPV integration sites and to chromosomal regions lost and gained in high-grade cervical neoplasia. Methylation changes were directed in part by the same cis-acting factors that appear to direct methylation changes in cancer, the presence of a bivalent chromatin mark in human embryonic stem cells and promoter CpG content; these associations explain much of the ontological profile of genes found to have increased methylation following HPV16 transfection. We were also able to show, using sequential samples from a cohort of young women with incident HPV16 infections, that the detection in cervical samples of methylated forms of the tumour suppressor gene, RARB, often parallels the natural history of cervical HPV infection. Our findings suggest that further investigation of the distribution and determinants of early virus-induced epigenetic reprogramming will provide important insights into the pathogenesis of virus-associated malignancy.

MYC activation associated with the integration of HPV DNA at the MYC locus in genital tumors

To determine whether integration of human papillomavirus (HPV) DNA sequences could lead to the deregulation of genes implied in oncogenesis, we analysed the HPV integration sites in a series of nine cell lines derived from invasive genital carcinomas. Using in situ hybridization, HPV16 or 18 sequences were found at chromosome band 8q24, the localization of MYC, in IC1, IC2, IC3, IC6 and CAC-1 cells and at other sites in IC4, IC5, IC7 and IC8 cells. We then localized viral sequences at the molecular level and searched for alterations of MYC structure and expression in these cells. MYC genomic status and viral integration sites were also analysed in primary tumors from which IC1, IC2, IC3 and IC6 cells were derived. In IC1, IC2 and CAC-1 cells, HPV DNA was located within 58 kb of MYC, downstream, upstream, or within MYC. In IC3 and IC6 cells, HPV DNA was located 400-500 kb upstream of MYC. Amplification studies showed that, in IC1, IC2 and IC3, viral and MYC sequences were co-amplified in an amplicon between less than 50 and 800 kb in size. MYC amplification was also observed in primary tumors, indicating that this genetic alteration, together with viral insertion at the MYC locus, had already taken place in vivo. MYC was not amplified in the other cell lines. MYC mRNA and protein overexpression was observed in the five cell lines in which the HPV DNA was inserted close to the MYC locus, but in none of the lines where the insertion had occurred at other sites. MYC activation, triggered by the insertion of HPV DNA sequences, can be an important genetic event in cervical oncogenesis.

Positioning of cervical carcinoma and Burkitt lymphoma translocation breakpoints with respect to the human papillomavirus integration cluster in FRA8C at 8q24.13

Molecular cytogenetic analysis frequently shows human papillomavirus (HPV) integration near translocation breakpoints in cervical cancer cells. We have recently described a cluster of HPV18 integrations in the distal end of the common fragile site FRA8C at 8q24 in primary cervical carcinoma samples. Chromosome band 8q24 contains the MYC gene (alias c- MYC), FRA8C, and FRA8D. The MYC gene is frequently deregulated—usually by translocation or amplification—in various tumor types. In the present study, we performed a molecular cytogenetic analysis of HPV18 integration patterns and the 8q24 translocation in a primary cervical carcinoma and in HeLa cells using combined binary ratio–fluorescence in situ hybridization. Our aim was to determine how the chromosomal breaks involved in these events relate physically to the MYC gene; whether they map to the FRA8C site, the FRA8D site, or both; and how they correlate with the occurrence of DNA flexibility domains. The 8q24 translocation breakpoints mapped between stretches of integrated HPV18 sequences in the distal end of FRA8C. This region contained DNA helix flexibility clusters, several of which mapped in the vicinity of HPV integration sites and translocation breakpoints in cervical carcinomas. DNA helix flexibility clusters were also found near known MYC translocation breakpoints in Burkitt lymphomas (BL), but most BL breakpoints mapped clearly outside FRA8C. Our data revealed that FRA8C is involved in HPV integration and chromosomal translocations in cervical carcinoma; however, this fragile site is not involved in classical MYC translocations in most BLs. In the context of the familial nature of cervical cancer, FRA8C may be considered a candidate susceptibility region for cervical carcinoma.

Mapping and analysis of HPV16 integration sites in a head and neck cancer cell line.

Human papillomavirus (HPV) is a circular double-stranded DNA virus implicated in at least 90% of cervical and anogenital cancers and has been observed in approximately 20% of squamous cell carcinomas of the head and neck (SCCHN). Transcription of the viral oncogenes E6 and E7 is regulated by expression of the E2 protein. Disruption of the E2 gene sequence due to viral integration results in upregulation of E6 and E7, which promote tumorigenesis by abrogating p53 and pRb functions. HPV integration sites in cervical and anogenital cancers have been mapped primarily to chromosomal fragile sites and in some cases have been shown to integrate within tumor suppressor genes or other cancer-related genes. To study viral integration sites in SCCHN, we examined an HPV16-infected SCCHN cell line cultured from a tongue-base tumor. HPV fluorescence in situ hybridization (FISH) revealed multiple integrated viral DNA copies in blocks throughout the genome. Sequential FISH and spectral karyotyping identified integration sites on chromosomes 3, 6, 9q, 13q and t(1;8)(q;?). Restriction site-polymerase chain reaction (RS-PCR) was performed to identify the viral-cellular junctions. Sequence analyses confirmed integration sites at 9q31.1 and 6p21 and revealed a novel junction at 16p12.3. Subsequent chromosome breakage studies suggested that the observed viral-cellular integration sites may have occurred within common fragile sites. Additional studies using RT-PCR for E6--E7 viral transcripts showed oncoprotein expression from episomal and integrated viral sequences. Our results suggest that viral integration of HPV in SCCHN appears to occur nonrandomly through targeting specific chromosomal sequences prone to breakage.

Simultaneous mapping of human papillomavirus integration sites and molecular karyotyping in short-term cultures of cervical carcinomas by using 49-color combined binary ratio labeling fluorescence in situ hybridization

Infection with high-risk type human papillomavirus (HPV) is a necessary causal factor in the pathogenesis of cervical carcinoma. In most invasive cervical cancers, HPV is integrated in the host cell genome, and additional genetic aberrations are observed among which are chromosomal aberrations. To analyze in detail such often complex chromosomal changes and simultaneously map HPV integration sites, we extended the multiplicity of the combined binary ratio labeling fluorescence in situ hybridization (COBRA-FISH) technique to 49 by inclusion of a large Stokes' shift fluorochrome as the third binary label. The technique allows mapping of the integrated HPV genome in the context of p- and q-arm COBRA-FISH, with a sensitivity of one copy of the HPV genome as tested for HPV 16 in SiHa cells. We investigated the molecular karyotypes and integration patterns of HPV types 16 and 18 in metaphase spreads from short-term cultures of primary cervical carcinomas (n=5). Of the tested cervical carcinomas, two contained integrated HPV at 8q24, one of which in addition harbored the integrated virus near a translocation breakpoint. Two carcinomas had integrated HPV at 17q21∼23 in a morphologically normal chromosome 17. One carcinoma contained HPV at 1q42 in a morphologically normal chromosome 1. Our data illustrate the efficacy of 49-color COBRA-FISH to resolve complex karyotypes and simultaneously map specific sequences in metaphases obtained from short-term solid tumor cultures.

A repetitive DNA sequence that characterizes human papillomavirus integration site into the human genome is present in vulvar vestibulitis

Objective: To determine the DNA sequence of polymerase chain reaction (PCR) products obtained from surgical specimens of patients with severe vulvar vestibulitis, in order to identify and type the human papillomavirus (HPV)-DNA associated with vulvar vestibulitis. Study Design: Fifty three women, referred for dyspareunia and diagnosed as having severe vestibulitis, underwent perineoplasty operation consisting of surgical removal of the sensitive vestibule. PCR analysis using L1 HPV primer was performed, and DNA sequencing of the samples that were found to contain HPV-DNA was undertaken, using the dideoxy chain termination method. Results: Using PCR, HPV-DNA was detected in 31 of 53 tissue specimens (58%). DNA sequencing of 12 HPV-positive PCR products revealed extensive homology to human Alu consensus sequence, albeit not to any known HPV sequence. Conclusions: The presence of interspersed, repetitive-DNA sequence Alu, which is known to be the preferred site for HPV integration into human genome, in the PCR product reinforces previous observations, suggesting that HPV may have a role in the pathogenesis of vulvar vestibulitis. It further implies a possible integration of the HPV into human DNA in these cases.

Human papilloma virus status and chromosomal imbalances in primary cervical carcinomas and tumour cell lines

Human papilloma virus (HPV) infection is the crucial step in the initiation of cervical carcinomas. In addition, HPV18 has been implicated in tumour progression and adverse clinical outcome. We determined the HPV types in 12 primary cervical carcinomas and 12 cell lines and compared the findings with the comparative genetic hybridisation (CGH) pattern of chromosomal alterations. The most frequent alteration was the deletion at 3p14 followed by the loss of 2q34-q36 along with 3q gain. High risk HPV types were detected in all samples except one primary tumour. In contrast to the normal distribution, HPV18 was present in 75% of cases including all cell lines. The cell lines carried a higher number of genetic alterations and a different CGH pattern for several chromosomes than the primary tumours, despite microdissection. Purely HPV18 positive cases indicated a high incidence of imbalances at specific loci with peaks of the histogram coinciding with known HPV integration sites. The study suggests that HPV infection is associated with a recurrent pattern of chromosomal changes in cervical carcinomas and that the development and progression of these alterations is triggered by integration into the host genome.

Herpes simplex virus and human papillomavirus sites correlate with chromosomal breakpoints in human cervical carcinoma

The distribution of 1,912 breakpoints observed in a series of 148 cervical cancers was analyzed. Fifty bands were shown to be nonrandomly involved in chromosome structural rearrangements. One hundred thirty-three breaks were noted in bands known to contain a human papillomavirus integration site, and 454 breaks were noted in bands containing a herpes simplex virus breakage site. We suggest that herpes simplex viruses and, possibly, papillomaviruses play an important role in the carcinogenesis and/or development of cytogenetic abnormalities in cervical cancers.

Gene mapping of human papillomavirus integration sites

Gene mapping of human papillomavirus integration sites