Human papillomavirus type 16 DNA is integrated into chromosome region 12q14-q15 in a cell line derived from a vulvar intraepithelial neoplasia

HPV DNA Integration at Actionable Cancer-Related Genes Loci in HPV-Associated Carcinomas

In HPV-associated carcinomas, some examples of cancer-related genes altered by viral insertion and corresponding to potential therapeutic targets have been described, but no quantitative assessment of these events, including poorly recurrent targets, has been reported to date. To document these occurrences, we built and analyzed a database comprised of 1455 cases, including HPV genotypes and tumor localizations. Host DNA sequences targeted by viral integration were classified as "non-recurrent" (one single reported case; 838 loci), "weakly recurrent" (two reported cases; 82 loci), and highly recurrent (≥3 cases; 43 loci). Whereas the overall rate of cancer-related target genes was 3.3% in the Gencode database, this rate increased to 6.5% in "non-recurrent", 11.4% in "weakly recurrent", and 40.1% in "highly recurrent" genes targeted by integration (p = 4.9 × 10-4). This rate was also significantly higher in tumors associated with high-risk HPV16/18/45 than other genotypes. Among the genes targeted by HPV insertion, 30.2% corresponded to direct or indirect druggable targets, a rate rising to 50% in "highly recurrent" targets. Using data from the literature and the DepMap 23Q4 release database, we found that genes targeted by viral insertion could be new candidates potentially involved in HPV-associated oncogenesis. A more systematic characterization of HPV/host fusion DNA sequences in HPV-associated cancers should provide a better knowledge of HPV-driven carcinogenesis and favor the development of personalize patient treatments.

Identification of Specific Tumor Markers in Vulvar Carcinoma Through Extensive Human Papillomavirus DNA Characterization Using Next Generation Sequencing Method

OBJECTIVES

A subset of vulvar carcinomas (VC) are associated with human papillomavirus (HPV) DNA. This trait can be used to identify tumor markers for patient's follow-up. A large diversity of HPV prevalence in VC has been reported, but no data are available concerning the insertional HPV status in this tumor type. Therefore, we have used an innovative next generation sequencing (NGS)-based CaptHPV method able to provide an extensive characterization of HPV DNA in tumors.

MATERIAL AND METHODS

Tumor tissue specimens from 55 patients with VC were analyzed using p16 immunohistochemistry, in situ hybridization, polymerase chain reaction, and CaptHPV-NGS assays.

RESULTS

Our analyses showed that 8 (14.5%) of 55 cases were associated with HPV 16 DNA. No other HPV genotypes were identified. The HPV genome was in a free episomal state only in one case and both episomal and integrated into the tumor cell genome in 7. There was a single insertion in 5 cases and multiple sites, scattered at different chromosomal loci in two. ISH data suggest that some of these might reflect tumor heterogeneity. Viral integration targeted cellular genes among which were TP63, CCDC148, LOC100133091, PKP1, and POLA2. Viral integration at the PKP1 locus was associated with partial gene deletion, and no PKP1 protein was detected in tumor tissue.

CONCLUSIONS

Using the NGS-based innovative capture-HPV approach, we established a cartography of HPV 16 DNA in 8 VC cases and identified novel genes targeted by integration that may be used as specific tumor markers. In addition, we established a rationale strategy for optimal characterization of HPV status in VC.

Repetitive transcranial magnetic stimulation targeting the insular cortex for reduction of heavy drinking in treatment-seeking alcohol-dependent subjects: a randomized controlled trial

Insula responses to drug cues are correlated with cravings, and lesions in this area reduce nicotine seeking. Here, we investigated the potential efficacy of repetitive transcranial magnetic stimulation (rTMS) targeting the insula in alcohol addiction. Treatment-seeking alcohol-dependent patients (Diagnostic and Statistical Manual of Mental Disorder, Fourth Edition; N = 56) participated in this double-blind, sham-controlled, randomized trial. Participants received 10 Hz rTMS or sham using an H8 coil, 5 days a week for 3 weeks. Stimulation targeted insular cortex and overlaying regions bilaterally, while excluding anterior prefrontal areas. Craving and self-reported as well as biomarker-based drinking measures were collected at baseline, during treatment, and through 12 weeks. Resting-state magnetic resonance imaging (rsMRI) data were collected before and after treatment. Task-based MRI was used to probe brain correlates of reward processing, affective responses, and alcohol following completion of treatment. A marked overall decrease in craving and drinking measures was observed during treatment, but did not differ between rTMS or sham stimulation. Both groups equally increased their alcohol use following completion of treatment and through the 12-week follow-up. Analysis using seeds in the insula identified differences in resting-state connectivity between active and sham groups at completion of treatment, potentially indicating an ability of treatment to modify insula function. However, while each task robustly replicated brain responses established in the literature, no effects of rTMS were found. Collectively, this study does not support efficacy of rTMS targeting the insula in alcohol addiction.

Differential p53-mediated responses to solar-simulated radiation in human papillomavirus type 16-infected keratinocytes

In immunocompromised patients, cooperative effects of human papillomavirus (HPV) and ultraviolet (UV) radiation have been postulated in the development of non-melanoma skin cancers. The tumor suppressor p53 is a key component of the cellular response to genotoxic agents, such as UV radiation. We have previously demonstrated that in HPV16-infected cells, a higher E6* level was associated with a higher resistance to UV and oxidative stress. Using the two same SKv cell lines, the aim of the present study was to investigate p53 and p21 expression and cell death in HPV-infected keratinocytes in response to UV irradiation and to determine the role of HPV oncoprotein levels on the p53-mediated cellular response. We demonstrated that the weakly E6*-expressing level SKv-e cell line presented both higher cytotoxicity and apoptosis to UV. This high sensitivity was associated with both p53 and p21 nuclear accumulation, while a high E6* level and resistance were associated with no p53 accumulation and a p21 nuclear down-regulation after UV. Moreover, in SKv-e cell line, p21 promoter activation was p53 dependent. Our results suggest that an alteration and/or a modulation of the p53-p21 pathway in response to UV could be determinant for HPV-infected keratinocyte survival and HPV-associated carcinogenic process.

E6* oncoprotein expression of human papillomavirus type-16 determines different ultraviolet sensitivity related to glutathione and glutathione peroxidase antioxidant defence

Clinical observations of non-melanoma skin cancer in immunocompromised patients, such as organ transplant recipients, suggest co-operative effects of human papillomavirus (HPV) and ultraviolet (UV) radiation. The aim of the present study is to evaluate UV sensitivity and DNA damage formation according to antioxidant status in HPV16-infected keratinocytes. We used SKv cell lines, infected with HPV16 and well characterized for their proliferative and tumorigenic capacities. We showed that SKv cell lines presented various E6* (a truncated form of E6) RNA levels. We demonstrated that the higher oncoprotein RNA expression level was associated with a higher resistance to solar-simulated radiation, more specifically to UVB radiation and to hydrogen peroxide. Moreover, this high resistance was associated with a low oxidative DNA damage formation after UV radiation and was related to high glutathione content and glutathione peroxidase activities. Therefore, the results of our study suggest that E6* levels could modulate the glutathione/glutathione peroxidase pathway providing a mechanism to protect HPV-infected keratinocytes against an environmental oxidative stress, such as UV radiation.

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.

Human papillomavirus and cervical neoplasia

Cervical cancer accounts for about 10% of all newly diagnosed cancers in women worldwide. The association between HPV infection and cervical neoplasia appears to be stronger than the association between smoking and lung cancer. At least 20 oncogenic HPV types have been identified in > 95% of preinvasive and invasive cervical cancers, HPV type 16 being the most common. HPV detection is important to identify those patients who may be at high risk for the development of cervical neoplasia. Detection techniques include Hybrid Capture (Digene, Silver Springs, MD) and PCR. Viral integration appears to be one of the necessary steps in malignant transformation. Recently, some of the repeated chromosomal alterations and patterns of integration sites have been identified in cervical cancer specimens. The low rate of HPV-negative cancers implies an effective HPV vaccine might have the ability to eradicate cervical cancer worldwide.

Human papilloma viruses and cervical tumours: mapping of integration sites and analysis of adjacent cellular sequences

BACKGROUND

In cervical tumours the integration of human papilloma viruses (HPV) transcripts often results in the generation of transcripts that consist of hybrids of viral and cellular sequences. Mapping data using a variety of techniques has demonstrated that HPV integration occurred without obvious specificity into human genome. However, these techniques could not demonstrate whether integration resulted in the generation of transcripts encoding viral or viral-cellular sequences. The aim of this work was to map the integration sites of HPV DNA and to analyse the adjacent cellular sequences.

METHODS

Amplification of the INTs was done by the APOT technique. The APOT products were sequenced according to standard protocols. The analysis of the sequences was performed using BLASTN program and public databases. To localise the INTs PCR-based screening of GeneBridge4-RH-panel was used.

RESULTS

Twelve cellular sequences adjacent to integrated HPV16 (INT markers) expressed in squamous cell cervical carcinomas were isolated. For 11 INT markers homologous human genomic sequences were readily identified and 9 of these showed significant homologies to known genes/ESTs. Using the known locations of homologous cDNAs and the RH-mapping techniques, mapping studies showed that the INTs are distributed among different human chromosomes for each tumour sample and are located in regions with the high levels of expression.

CONCLUSIONS

Integration of HPV genomes occurs into the different human chromosomes but into regions that contain highly transcribed genes. One interpretation of these studies is that integration of HPV occurs into decondensed regions, which are more accessible for integration of foreign DNA.

Single copy heterozygote integration of HPV 33 in chromosomal band 5p14 is found in an epithelial cell clone with selective growth advantage

Infection with human papillomavirus (HPV) of specific high-risk type triggers a series of events in target cells, which will eventually lead to development of genital neoplasia. The integration of high-risk HPV DNA into the cell genome has been regarded as a crucial event in tumor progression. With respect to different HPV types, the knowledge of HPV integrated loci is still limited. We have now determined the genomic variation and chromosomal location of HPV 33 DNA in the cell line UT-DEC-1, established from a vaginal mild dysplasia lesion. The viral sequence of the cell line was determined, and a variant of the prototype HPV 33 strain was identified, showing nucleotide substitutions resulting in amino acid changes in the E2, L2 and E4 open reading frames. In late passage UT-DEC-1 cells, a deletion of more than half of the 3' part of E1 and major parts of the E2 and E4 genes provided evidence for integration. The flanking sequences of the integration site were completely homologous to published sequences from chromosomal band 5p14, and remained unchanged in all subclones established from late passage cells. There were no chromosomal deletions or gross rearrangements at the integration site, and only a single heterozygotic copy of HPV 33 was detected. The karyotype of late passage cells showed only minor changes compared with early passage cells. During passaging of the cell line, there were progressive changes towards a malignant phenotype, and in parallel to this, the cells carrying episomal HPV 33 of the early passages was completely superseded by cells containing the integrated virus. Thus, our results show that this single copy heterozygote integration of HPV 33 into chromosome band 5p14 appears to be associated with emergence of cells escaping senescence, and with growth advantage compared with cells carrying episomal virus.

Integrated human papillomavirus type 16 is frequently found in cervical cancer precursors as demonstrated by a novel quantitative real-time PCR technique

In contrast to cervical cancer, integration of human papillomavirus (HPV) DNA into the host genome has been considered a rare event in cancer precursor lesions (cervical intraepithelial neoplasia [CIN]). With our new real-time PCR method, we demonstrated that integrated HPV type 16 (HPV16) is already present in CIN lesions. The physical state of HPV16 and the viral load were simultaneously detected. A unique region of the E2 open reading frame (ORF) that is most often deleted during HPV16 integration is targeted by one set of PCR primers and a probe, and another set targets the E6 ORF. In episomal form, both targets should be equivalent, while in integrated form, the copy numbers of E2 would be less than those of E6. The method was tested with DNAs from 31 cervical lesions (non-CIN to CINIII) from 24 women prospectively followed up for 10 years. This report presents viral load and integration results from the largest series of CIN lesions described to date. Only one sample contained exclusively episomal HPV16 DNA, and this lesion regressed spontaneously. Samples from another patient, with only integrated HPV16, rapidly progressed from CINI to CINIII in 2 years. In all other patients, episomal and integrated forms of HPV16 DNA were found to coexist. Rapid progression of the CIN lesions was closely associated with a heavy load of integrated HPV16. Thus, the method described here is a very sensitive tool with which to assess the physical state of HPV, which is useful in predicting disease progression.

Localization of the human stat6 gene to chromosome 12q13.3-q14.1, a region implicated in multiple solid tumors

Stat6 signaling pathways have been correlated with functional responses induced by IL-4 and PDGF that may play a role in human malignancy. Utilizing fluorescence in situ hybridization, we mapped the human Stat6 gene to chromosome 12q bands 13.3-14.1, a breakpoint region implicated in a wide variety of solid tumors. To understand the genesis of three human Stat6 variant cDNAs, including a naturally occurring dominant negative species, we further characterized the genomic structure and flanking regions of the human Stat6 gene. The human Stat6 gene encompassed over 19 kb and contained 23 exons. For promoter studies, we introduced flanking sequence 5' of Stat6 exon 1 into a promoterless luciferase reporter vector and characterized basal promoter activity by deletion analysis. DNA sequence analysis revealed potential transcriptional regulation of the putative promoter through numerous consensus binding elements. Finally, we conclude that selective exon deletion and utilization of alternative donor/acceptor sites appear to explain best human Stat6 variant mRNAs.

Human papillomavirus type 18 DNA sequences in adenocarcinoma and adenosquamous carcinoma of the uterine cervix

Human papillomavirus (HPV) DNA sequences were detected by Southern blot hybridization and polymerase chain reaction (PCR) in 10 out of 19 patients (52.7%) with adenocarcinoma [15] and adenosquamous [4] carcinoma of the uterine cervix. HPV 18 DNA was detected in 8 of these 19 patients (42.1%), HPV 16 DNA in 1 patient (5.3%) and HPV type X (unknown) in another (5.3%). Of the 10 HPV positive samples HPV 18 was found in 6 out of 6 pure adenocarcinomas (100%), and in 2 of 4 (50%) adenosquamous carcinomas. HPV 16 and HPV X were each detected in 1 out of 4 (25%) adenosquamous carcinomas. The physical state of the viral DNA was investigated in 5 of the 10 HPV-positive cases. All the specimens from these 5 cases showed HPV to be integrated into the host genome, except for one adenosquamous specimen, which showed both episomal and integrated forms of HPV 16. Six of 8 HPV 18 DNA positive specimens were from cases of pure adenocarcinoma and it was found by PCR that five of these 6 specimens retained fragments of E6/E7, LCR/E7 and early sequence of E1 fragment (sequence: 1188-1373) but deleted most part of E1.

Progressive growth of human papillomavirus type 16-transformed keratinocytes is associated with an increased release of soluble tumour necrosis factor (TNF) receptor

Analysis of conditioned media generated by weakly and highly tumorigenic SKv-1 keratinocyte lines harbouring integrated human papillomavirus type 16 (HPV16) DNA sequences revealed a factor inhibiting TNF-alpha and TNF-beta cytotoxic activity. This inhibitory activity was specifically blocked by htr-9 monoclonal antibody (MAb) recognising 55/60 kDa type I TNF receptor suggesting that it is related to a soluble form of this particular receptor (sTNF-RI). The presence of sTNF-RI was confirmed by Western blot analysis of SKv-1 cell-conditioned medium showing a band of 31.5 kDa as well as by the specific enzyme-linked immunobiological assay (ELIBA). Release of sTNF-RI was a result of shedding because Northern blot analysis showed that SKv-1 cells expressed a full-length TNF-RI mRNA, and radioimmunoprecipitation of TNF-RI from [32S]cysteine-labelled cell extracts demonstrated the presence of normal 55 kDa molecule. Evaluation by ELIBA showed that highly tumorigenic SKv-12 cells released significantly more sTNF-RI than their weakly tumorigenic SKv-11 parental cells. Furthermore, human recombinant as well as SKv cell-derived sTNF-RI stimulated proliferation of weakly tumorigenic SKv-11 cells. This suggests that a progressive growth of some neoplastic cells may be, at least partially, a result of an increased spontaneous release of sTNF-RI that enables the cells to escape from local TNF-alpha-mediated growth inhibition.

Deletion in human chromosome region 12q13-15 by integration of human papillomavirus DNA in a cervical carcinoma cell line

In human cervical carcinomas papillomavirus DNA is frequently integrated in the cell genome. We have cloned the integration site of human papillomavirus-18 DNA in human chromosome region 12q13-15 present in the SW756 cervical carcinoma cell line. Viral DNA is broken from nucleotides 2643 to 3418 in the E1 and E2 open reading frames, resulting in a deletion of 775 bases of viral DNA. Cloning and sequence analysis of the rearranged and germline alleles shows that there is no homology between the target cellular and viral DNA, suggesting it is a nonhomologous recombination. The target cellular region is called papillomavirus associated locus 2 (PAL2). The 5'- and 3'-flanking probes derived from the hybrid viral-cellular clone detect completely different germline restriction fragments in DNA from cells with normal chromosome 12. There is no overlap between the restriction maps of the target germline clones obtained with 5'- and 3'-flanking probes. Probes from these germline clones beyond the breakpoint position do not detect any DNA rearrangement in SW756 cells DNA. These data prove that there is a deletion of cellular DNA as consequence of the integration, with an estimated minimum size of 14 kilobases. Both cellular flanking probes are outside the amplicon of this chromosome region identified in the OSA and RMS13 sarcoma cell lines, comprising SAS-CHOP-CDK4-MDM2 genes and where translocation breakpoints are located in liposarcomas. The integration at 12q13-15 might have been selected by its contribution to the tumor phenotype.

Increased tumorigenicity of human keratinocytes harboring human papillomavirus type 16 is associated with resistance to endogenous tumor necrosis factor-alpha-mediated growth limitation

The aim of this study was to evaluate the relationship between tumorigenicity of cell sublines derived from weakly tumorigenic SKv-e and SKv-l keratinocytes harboring human papillomavirus type 16 (HPV16) and their susceptibility to autocrine growth limitation mediated by tumor necrosis factor-alpha (TNF-alpha). These sublines displayed different in vitro proliferative potential which correlated with tumorigenicity in nu/nu mice. Recombinant TNF-alpha inhibited in vitro growth of weakly tumorigenic parental SKv cell lines while it did not affect proliferation of their respective highly tumorigenic sublines. Resistance to TNF-alpha correlated with both increased in vitro proliferation and tumorigenicity. Anti-TNF-alpha antibodies (Ab) significantly increased in vitro proliferation of weakly tumorigenic parental SKv cells up to the levels of their highly tumorigenic sublines. Growth of highly tumorigenic SKv cells was not affected. On the other hand, proliferation of SKv cells was affected neither by transforming growth factor-beta (TGF-beta) nor by anti-TGF-beta Ab. All SKv cell sublines tested spontaneously released TNF-alpha, as evaluated by a specific radioimmunoassay; however, the levels of the endogenous cytokine were not related to their proliferative potential and tumorigenicity. An increased resistance to the anti-proliferative effect of TNF-alpha may be associated with decreased expression of TNF-alpha receptors (TNF-alpha R) inasmuch as evaluation of 125I-TNF-alpha binding and Northern-blot analysis of TNF-alpha R-specific mRNA showed that highly tumorigenic SKv cell sublines expressed significantly lower numbers of TNF-alpha R than their respective parental cells. These results show that an increased tumorigenicity of HPV16-harboring SKv keratinocytes may be, at least partially, due to escape from autocrine TNF-alpha-mediated growth limitation.

Chromosome fragility in lymphocytes of women with cervical uterine lesions produced by human papillomavirus

We studied 30 women with cervical lesions that showed human papillomavirus infection (HPV). Cervical HPV infection was diagnosed by cytology, histology, immunohistochemistry, and electron microscopy, as well as by DNA viral hybridization in situ with 6, 11, 16, and 18 HPV types. Three groups of patients were studied: 15 women infected by HPV of 6 and 11 types with koilocytic lesions and benign evolution, 15 women infected by HPV of 16 and 18 types with koilocytic lesions and malignant evolution, and 15 normal women without cervical lesions who served as controls. For each group, chromosome fragility was studied in peripheral blood lymphocytes. Aphidicolin (AP) was used as a clastogenic agent at a concentration of 0.12 microM. There were significant differences (p less than 0.001) between the control population and the patients affected by HPV. There were also significant differences (p less than 0.001) between the two groups infected with HPV. Our findings support the concept that chromosome fragility could serve as a cytogenetic marker to measure evolution, prognosis, and treatment of cervical lesion associated with HPV.

Genetic alterations by human papillomaviruses in oncogenesis

The integration sites in the cellular genome of human papillomavirus are located in chromosomal regions always associated with oncogenes or other known tumor phenotypes. Two regions, 8q24 and 12q13, are common to several cases of cervical carcinoma and can have integrated more than one type of papillomavirus DNA. These two chromosomal regions contain several genes implicated in oncogenesis. These observations strongly imply that viral integration sites of DNA tumor viruses can be used as the access point to chromosomal regions where genes implicated in the tumor phenotype are located, a situation similar to that of non-transforming retroviruses.

Integration of papillomavirus DNA near myc genes in genital carcinomas and its consequences for proto-oncogene expression

DNA sequences of specific human papillomavirus (HPV) types are found integrated in the cell genome in most invasive genital carcinomas. We have determined the chromosomal localization of integrated HPV type 16 (HPV-16) or HPV-18 genomes in genital cancers by in situ hybridization experiments. In three cancers, HPV sequences were localized in chromosome band 8q24.1, in which the c-myc gene is mapped, and in one cancer HPV sequences were localized in chromosome band 2p24, which contains the N-myc gene. In three of the four cases, the proto-oncogene located near integrated viral sequences was found to be structurally altered and/or overexpressed. These data indicate that HPV genomes are preferentially integrated near myc genes in invasive genital cancers and support the hypothesis that integration plays a part in tumor progression via an activation of cellular oncogenes.

Constitutive release of IL6 by human papillomavirus type 16 (HPV16)-harboring keratinocytes: a mechanism augmenting the NK-cell-mediated lysis of HPV-bearing neoplastic cells

In the present study we demonstrate that the cultured human keratinocyte cell line (SK-v cells) harboring and expressing integrated human papillomavirus type 16 (HPV16) DNA sequences constitutively releases IL6, which is known as a pleiotropic immunoregulatory cytokine of potential antitumor properties. The presence of IL6 activity in SK-v cell-conditioned media (SK-v CM) was demonstrated by tritiated thymidine incorporation into IL6-dependent B9 murine plasmacytoma cells. The effect on B9 cells was specific since it could be inhibited by anti-IL6 neutralizing antibodies but not by a normal control serum. IL6 did not affect SK-v cell growth; however, it significantly augmented NK cell activity of human peripheral blood lymphocytes against both K562 erytholeukemic and SK-v cells as assessed by 51Cr release assay. SK-v CM displayed NK cell-augmenting activity that copurified with IL6 activity in both size exclusion and anion-exchange HPLC. Furthermore, SK-v cell-derived NK cell stimulatory activity could be neutralized with anti-IL6 antibodies. These results suggest that HPV-harboring neoplastic cells can release IL6 which may indirectly mediate tumor death by augmentation of NK cell activity.

Chromosomal characterizations of human nasal and nasopharyngeal cells immortalized by human papillomavirus type 16 DNA

Cell lines NW-1 and NPC-N were established by transfection of human nasal and nasopharyngeal epithelial cells, respectively, with human papillomavirus type 16 (HPV-16) DNA. Additional treatment of NPC-N cells with mitomycin C gave rise to the cell line NPC-N-M. Chromosomal analysis showed that 40-47% of NW-1, NPC-N, and NPC-N-M cells had a near-tetraploid number of chromosomes and several chromosomal abnormalities. These cells showed evidence of gene amplification in the form of double minutes (dmins). In situ hybridization with HPV-16 DNA probe demonstrated that the virus was integrated at the 2q21 chromosomal region in NPC-N cells. Multiple integration sites within 1p36, 1q31-q32, 2p25, and 2q21 regions were observed in NW-1 cells. Although all of these immortal cells could grow in methylcellulose, none of them demonstrated tumorigenicity in nude mice.