Papillomavirus sequences integrate near cellular oncogenes in some cervical carcinomas

Distinct patterns of alteration of myc genes associated with integration of human papillomavirus type 16 or type 45 DNA in two genital tumours

We previously described two genital carcinomas (IC2, IC4) containing human papillomavirus type 16 (HPV-16)- or HPV-18-related sequences integrated in chromosomal bands containing the c-myc (8q24) or N-myc (2p24) gene, respectively. The c-myc gene was rearranged and amplified in IC2 cells without evidence of overexpression. The N-myc gene was amplified and highly transcribed in IC4 cells. Here, the sequence of an 8039 bp IC4 DNA fragment containing the integrated viral sequences and the cellular junctions is reported. A 3948 bp segment of the genome of HPV-45 encompassing the upstream regulatory region and the E6 and E7 ORFs was integrated into the untranslated part of N-myc exon 3, upstream of the N-myc polyadenylation signal. Both N-myc and HPV-45 sequences were amplified 10- to 20-fold. The 3' ends of the major N-myc transcript were mapped upstream of the 5' junction. A minor N-myc/HPV-45 fusion transcript was also identified, as well as two abundant transcripts from the HPV-45 E6-E7 region. Large amounts of N-myc protein were detected in IC4 cells. A major alteration of c-myc sequences in IC2 cells involved the insertion of a non-coding sequence into the second intron and their co-amplification with the third exon, without any evidence for the integration of HPV-16 sequences within or close to the gene. Different patterns of myc gene alterations may thus be associated with integration of HPV DNA in genital tumours, including the activation of the protooncogene via a mechanism of insertional mutagenesis and/or gene amplification.

A highly sensitive nonisotopic detection method for in situ hybridization

In situ hybridization is a technique that allows detection of specific DNA and RNA sequences in tissue sections. Nonisotopic techniques are fast and give a precise localization of the hybridization product, but a drawback is the low sensitivity. However, the sensitivity is dependent on the detection system used. To evaluate a sensitive in situ hybridization method with nonradioactive probes we compared three different detection systems, using biotin-labeled human papillomavirus (HPV) 16 probes. The three detection systems included (i) STAV-FITC method (streptavidin-fluorescein isothiocyanate/alkaline phosphatase anti-FITC), (ii) APAAP method (mouse anti-biotin/anti-mouse IgG/alkaline phosphatase mouse anti-alkaline phosphatase), and (iii) tyramide signal amplification (TSA) method (STAV-horseradish peroxidase (HRP)/biotinyl tyramide/STAV-HRP). The in situ hybridization methods were tested on CaSki and SiHa cells and two cervical carcinomas known to be HPV16 positive. The cells and tissues and been fixed in 4% buffered formalin and paraffin embedded. The three different detection systems gave satisfactory nuclear staining in CaSki cells (CaSki cells contain > 500 copies of HPV16 DNA) and the two cervical carcinomas. However, demonstration of HPV16 DNA in SiHa cells (SiHa cells contain one to two HPV16 genome copies) was possible only by use of the APAAP method. It was concluded that the APAAP method provides the best sensitivity among the nonisotopic detection systems and can detect single viral copies in formalin-fixed and paraffin-embedded material.

Cloning and characterization of a novel caprine genomic repetitive element that hybridizes with papillomavirus DNA

A goat genomic library was screened by Southern blot hybridization at reduced stringency with a bovine papillomavirus type 5 (BPV 5) DNA probe in order to identify potential cellular and viral sequences related to the papillomavirus genome. A recombinant clone with an 8.5 kb genomic insert was found to contain a 1.3 kb PstI subfragment (designated as P1-1) that hybridized with the DNA of BPV 5, two murine papillomaviruses and human papillomavirus types 5 and 8, but not with DNA from another eight human and bovine papillomavirus types. Southern blot hybridization of the goat P1-1 DNA probe was restricted to a single 1.0 kb subfragment within the E1 open reading frame (ORF) of BPV 5 but produced multiple bands ranging between 1.0 and 9.0 kb when hybridized under stringent conditions with PstI-digested DNA obtained from different goat tissues. The genomic sequence of P1-1 has direct repeats of 10 and 13 nucleotides flanking 153 nucleotides, and 889 nucleotides of sequence, respectively, and an inverted repeat sequence of 11 nucleotides flanking a major ORF potentially coding for 244 residues. Potential splice acceptor and donor sites capable of joining with upstream and downstream exons are present within the major ORF. Sequence similarity between P1-1 and BPV 5 DNA at the nucleotide and amino acid level was limited to a stretch of 58 nucleotides which includes an oligopurine/pyrimidine tract. This region of similarity contains a predicted glutamic acid-rich domain. The P1-1 sequence is a novel repetitive element within the goat genome that is unrelated in sequence to papillomavirus DNA and to genomic sequences of mouse and man.

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.

Repression of the integrated papillomavirus E6/E7 promoter is required for growth suppression of cervical cancer cells

The human papillomavirus (HPV) E2 protein is an important regulator of viral E6 and E7 gene expression. E2 can repress the viral promoter for E6 and E7 expression as well as block progression of the cell cycle in cancer cells harboring the DNA of "high-risk" HPV types. Although the phenomenon of E2-mediated growth arrest of HeLa cells and other HPV-positive cancer cells has been well documented, the specific mechanism by which E2 affects cellular proliferation has not yet been elucidated. Here, we show that bovine papillomavirus (BPV) E2-induced growth arrest of HeLa cells requires the repression of the E6 and E7 promoter. This repression is specific for E2TA and not E2TR, a BPV E2 variant that lacks the N-terminal transactivation domain. We demonstrate that expression of HPV16 E6 and E7 from a heterologous promoter that is not regulated by E2 rescues HeLa cells from E2-mediated growth arrest. Our data indicate that the pathway of E2-mediated growth arrest of HeLa cells requires repression of E6 and E7 expression through an activity specified by the transactivation domain of E2TA.

Human papillomaviruses and cervical neoplasia: a model for carcinogenesis

Human papillomaviruses are etiologic for cervical cancers and their pathologic precursors. As presented in this review, pathologic, epidemiologic, and molecular data all support a working model that accounts for the pathogenetic role of these viruses in cervical neoplasia. Diagnostic criteria and classification systems are discussed in light of this model. These insights point to a potential change in clinical screening systems for cervical cancer. In addition, vaccine trials for oncogenic HPVs have begun. In the long term, these trials may hold promise as truly specific preventive therapy for this common human cancer.

The molecular genetics of cervical carcinoma

In the pathogenesis of cervical carcinoma there are three major components, two of them related to the role of human papillomaviruses (HPV). First, the effect of viral E6 and E7 proteins. Second, the integration of viral DNA in chromosomal regions associated with well known tumour phenotypes. Some of these viral integrations occur recurrently at specific chromosomal locations, such as 8q24 and 12q15, both harbouring HPV18 and HPV16. And third, there are other recurrent genetic alterations not linked to HPV. Recurrent losses of heterozygosity (LOH) have been detected in chromosome regions 3p14-22, 4p16, 5p15, 6p21-22, 11q23, 17p13.3 without effect on p53, 18q12-22 and 19q13, all of them suggesting the alteration of putative tumour suppressor genes not yet identified. Recurrent amplification has been mapped to 3q+ arm, with the common region in 3q24-28 in 90% of invasive carcinomas. The mutator phenotype, microsatellite instability, plays a minor role and is detected in only 7% of cervical carcinomas. The development of cervical carcinoma requires the sequential occurrence and selection of several genetic alterations. The identification of the specific genes involved, and their correlation with specific tumour properties and stages could improve the understanding and perhaps the management of cervical carcinoma.

Characterization of the C-MYC amplicon in a case of acute myeloid leukemia with double minute chromosomes

We have characterized the double minute chromosomes in a case of acute myeloid leukemia (AML). Southern blot analysis showed that the C-MYC was amplified. Further analysis with probes located both 3' and 5' of MYC indicated that the amplicon was at least 700 kb in size, extending from the papilloma virus integration site situated 500 kb 5' of MYC to the PVT gene located 280 kb 3' of MYC. This appears to be the largest MYC-containing amplicon in human leukemia.

Pathogenesis of non-AIDS-defining cancers: a review

As the AIDS epidemic advances, the number of HIV-infected subjects developing AIDS-related neoplasms is rapidly increasing, and the spectrum of malignancies encountered is expanding. Several non-AIDS-defining cancers are being reported at an increasing incidence in HIV-infected individuals, including anal, skin, oral mucosa, head and neck and lung carcinomas, testicular tumors, and pediatric soft-tissue sarcoma. There appears to be an emerging role for various concurrent viral infections in the HIV-infected host that are likely implicated in the pathogenesis of some nondefining-AIDS neoplasms. Our recent findings in HIV-associated lung cancers and in the precursor lesions of cervical carcinoma suggest that wide-spread genomic instability, as manifested by the development of increased numbers of microsatellite alterations (MAs), may occur frequently in HIV-associated tumors and they may play an important role in the pathogenesis of those neoplasms. Although the mechanism underlying the development of increased MAs is unknown, it may play a crucial role in the development of many HIV-associated tumors. It will be important to track the epidemiological and biological features of non-AIDS-defining cancers in HIV-infected patients, and compare them to those tumors in the general population. It is likely that further clues about malignant transformation and oncogenesis unraveled in the HIV setting will have broad clinical implications.

Detection of p16 gene alteration in cervical cancer using tissue microdissection and LOH study

The p16 gene was identified as cyclin-dependent kinase inhibitor (CDKI) and this may negatively regulate the cell cycle by acting as a tumor suppressor. Using tissue microdissection, the molecular changes at p16 and Rb genes were analysed in the spectrum of disease from dysplasia to invasive cancer of the uterine cervix. Six of 27 (22%) cases informative for D9S171 and IFNA of 9p21-22 marker (p16INK4a) showed loss of one or both alleles in at least one of these loci. LOH of pRb was detected in 29% (5/17). Gene alterations at p16 and pRb loci were only detectable in some cases of HPV-16/18 DNA positive cervical cancer. Three cases demonstrated mutational changes of p16INK4a, and the alterations were determined to be G to T shift, suggesting transitional missense mutation. In summary, the inactivation of the p16/cdk-cyclin/Rb cascade may play an additional role during the malignant progression in HPV-16/18 positive cervical cancers.

Human papilloma virus type 16 E6 gene expression in oral exophytic epithelial lesions as detected by in situ rtPCR

OBJECTIVE

We adopted an in situ reverse transcriptase polymerase chain reaction method of detecting and determining the frequency of early (E6) gene expression of human papilloma virus type 16 at the individual cell level in a sample of oral exophytic lesions with various degrees of epithelial hyperplasia and dysplasia in immunosuppressed and immunocompetent patients.

STUDY DESIGN

The significance of differences between the study groups was determined by Mantel-Haenszel chi-square analysis and calculation of odds ratios, accounting for immunosuppression and degree of dysplasia, respectively.

RESULTS

Grouped together, the lesions of dysplasia (mild to severe) and squamous cell carcinoma were found to be 16 times more likely to express human papilloma virus E6 mRNA than the benign lesions (P = .0013); in the lesions of immunosuppressed patients, human papilloma virus 16 E6 was roughly 10 times more likely to be expressed than in those of the immunocompetent patients (P = .0008, accounting for dysplasia).

CONCLUSIONS

Our data indicate that human papilloma virus 16 E6 gene expression, and perhaps integration of the virus in the host genome, might play a role in the development of oral neoplasia in association with immunosuppression.

Endocrine tumors of the cervix: morphologic assessment, expression of human papillomavirus, and evaluation for loss of heterozygosity on 1p,3p, 11q, and 17p

BACKGROUND

Cervical endocrine tumors are rare lesions, with a varied diagnostic nomenclature. A recent consensus meeting proposed a standardized terminology. This study evaluated: 1) applicability of histopathologic guidelines; 2) evidence of loss of heterozygosity (LOH) at selected sites; and 3) the presence of human papillomavirus (HPV) detected by nonisotopic in situ hybridization (ISH).

METHODS

Thirty-eight cases (patient age range, 19-88 years; mean, 48 years) were retrieved. Outcome data were available for 32 patients. Classification was based on architectural and cytologic features. Tissue was available from 15 cases for LOH analysis with D3S1234(3p14), D3S1289(3p21), THRB(3p24), TP53(17p13), D1S468(1p36), and INT-2(11q13). In ten cases, tissue was analyzed by nonisotopic ISH with HPV probes for types 6/11, 16/18, and 31/33.

RESULTS

Tumors were divided into four groups: small cell carcinoma (SCC) (n=25); large cell neuroendocrine carcinoma (LCNC) (n=5); SCC with focal LCNC differentiation (n=3), and carcinoid tumor (n=5). Tumors defined as exclusively or predominantly SCC had a particularly poor prognosis, with 20 patients dead of disease (<6 years after diagnosis) and 6 alive with disease (after <3 years of follow-up). LOH at various 3p loci (3p14, 3p21, and 3p24) was observed in eight cases. One patient demonstrated LOH on 17p(TP53). Eight of ten cases assessed by ISH showed nuclear staining using a combined HPV-16/18 probe.

CONCLUSIONS

Cervical endocrine tumors are highly aggressive and can be subdivided into definable categories. LOH at 3p loci is a frequent finding, as is nuclear staining with a combined HPV-16/18 probe. LOH at 17p(TP53 locus) appears to be relatively uncommon, suggesting that p53 mutations may not be developmentally significant.

Expression of ras, c-myc, and p53 proteins in cervical intraepithelial neoplasia

BACKGROUND

The development of cervical carcinoma is influenced by multiple factors, including the presence of certain high risk types of human papillomavirus. The purpose of the current study was to investigate possible cooperating genetic changes by examining the expression of p53, p62 myc, and p21 ras in cervical biopsy specimens.

METHODS

Three hundred and ninety-five cervical biopsy specimens representing normal through high grade cervical intraepithelial neoplasia (CIN) were screened by immunohistochemistry for expression of p53, p62myc, and p21ras.

RESULTS

Neither the proportion of tissues staining positive for a given protein nor the staining patterns within the epithelial layers differed significantly among normal or CIN biopsy samples. However, grade specific nuclear staining of p21ras was found in the cells of 10 lesions that were classified as CIN I by histology.

CONCLUSIONS

These results established the normal distribution and expression patterns of p53, p62myc, and p21ras within 395 cervical biopsy samples representing normal through CIN III histology. The expression of these proteins (e.g., staining intensity and layer of epithelium staining positive) is similar in normal tissues and those demonstrating all grades of CIN.

Recurrent integration of papillomavirus DNA within the human 12q14-15 uterine breakpoint region in genital carcinomas

Genital carcinomas are associated with human papillomaviruses, and the viral DNA is frequently integrated in the host cell genome. Recurrent chromosomal alterations are genetic markers for specific tumor phenotypes. To demonstrate that papillomavirus DNA integration is indeed a recurrent chromosomal aberration, we mapped two independent papillomavirus integration sites in the human 12q14-15 region, one containing HPV16 DNA and the other HPV18 DNA. The two HPV integration sites map approximately 10 kbp from each other within the cosmid LLNL12NCO1-196E1 clone. The integration site corresponding to HPV16 DNA in SK-v cells is proximal to the 5' end of a DNA segment known to be rearranged by integration of HPV18 DNA in another cervical carcinoma cell line, SW756. Both integrations are located in the PAL2 locus within the uterine leiomyoma cluster region of translocation.

Current perspectives on the molecular pathogenesis of virus-induced cancers in human immunodeficiency virus infection and acquired immunodeficiency syndrome

A distinct group of cancers particularly threaten human immunodeficiency virus (HIV)-infected people. Most HIV/acquired immunodeficiency syndrome (AIDS)-associated cancers have a substantial component of viral etiology. Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpesvirus (HHV8), human papillomavirus (HPV), and HIV have been implicated in the etiology of cancers in AIDS. The molecular mechanisms by which HPV, EBV, HHV8, and HIV persist and cause cancer are summarized. The viral etiology of AIDS-associated cancers is important because pharmacologic and immunologic strategies to prevent or attack persistent or latent virus infection and cell growth transformation may be useful in preventing and treating these cancers. Effective immune attack on latent and persistent virus infection will require enhanced cellular immune responses. Such responses may be achievable through active immunization or by in vitro expansion of viral and host specific cytotoxic and helper T lymphocytes. Enhanced knowledge of clinically applied T-cell immunology may also be useful in preventing and treating HIV infection and other opportunistic infections in HIV-infected people.

Cancer chemoprevention. A new way to treat cancer before it happens

Cancer chemoprevention uses noncytotoxic drugs or nutrients to prevent, retard, or delay carcinogenesis. The future of cancer chemoprevention depends on understanding key cellular growth and proliferation-controlling events, developing markers of molecular carcinogenesis, surrogate endpoint biomarkers, and targeted chemopreventive approaches.

Malignant transformation of recurrent respiratory papillomatosis associated with integrated human papillomavirus type 11 DNA and mutation of p53

Recurrent respiratory papillomatosis (RRP), usually confined to the nasopharynx, trachea, and larynx, occasionally can progress to extensive bronchopulmonary disease. Most cases of bronchopulmonary and laryngeal papillomatosis are cytologically benign and do not undergo malignant transformation; however, squamous cell carcinoma (SCC) can arise in RRP in the absence of known risk factors such as radiation and smoking. In this study, the authors investigated molecular genetic alterations occurring in a case of metastasizing SCC that arose in long-standing bronchopulmonary papillomatosis. Genomic DNA from tracheal papillomata, tracheobronchial papillomata, SCC of the lung, and a lymph node metastasis was extracted. The physical state of the human papillomavirus type 11 (HPV-11) DNA was investigated by two-dimensional gel electrophoresis. Molecular genetic alterations of the host genome were studied by direct sequencing of polymerase chain reaction-amplified gene fragments and restriction fragment length polymorphism (RFLP) analysis. Episomal and integrated forms of HPV-11 sequences were detected in histologically benign tumors, but only the integrated form of the viral DNA could be found in malignant tissue samples. Molecular genetic studies revealed that an allelic loss of the interferon-beta gene (IFNbeta-1) and an endogenous type of mutation of the p53 antioncogene were found only in the malignant lesions. Mutations were not observed in the ras, neu, or multiple tumor suppressor (MTS1/p16) genes in any specimens. The authors' data indicated that the p53 genetic mutation was associated with integration of HPV-11 in histologically malignant lesions. This association may promote a progressive genetic instability that can lead to the development and clonal expansion of malignant lesions in RRP.

Antibodies against early proteins of human papillomaviruses as diagnostic markers for invasive cervical cancer

Cervical cancer is the most prevalent tumor in developing countries and the second most frequent cancer among females worldwide. Specific human papillomaviruses (HPVs) and, most notably, HPV types 16 and 18 are recognized as being causally associated with this malignancy. Antibodies against early HPV proteins E6 and E7 have been found more often in patients with tumors than in controls. Existing peptide enzyme-linked immunosorbent assays (ELISAs) for the detection of anti-E6 and anti-E7 antibodies in human sera have low levels of sensitivity and specificity and thus are not suitable for use as diagnostic tools. Based on highly purified recombinant native proteins, we developed four sandwich ELISAs for the detection of antibodies against HPV type 16 and 18 E6 and E7 proteins. We demonstrate their sensitivities and high degrees of specificity for cervical cancer. Among a total of 501 serum specimens from unselected patients with invasive cervical cancer, 52.9% reacted positively in at least one of the four assays. In contrast, among 244 serum specimens from control subjects without cervical cancer, only 2 reactive serum specimens (0.8%) were found. For 19 of 19 antibody-positive patients, the HPV type indicated by seroreactivity was identical to the HPV DNA type found in the tumor, which also indicates a high degree of specificity for antibody detection with respect to HPV type. In a direct comparison of 72 serum specimens from patients with cervical cancer, 56% of the specimens reacted in at least one of the four protein ELISAs, whereas 40% reacted in at least one of seven peptide ELISAs covering the four antigens. These assays could be of value for the detection of invasive cervical cancer in settings in which cytology-based early tumor screening is not available, for the clinical management of patients diagnosed with cervical cancer, and for the immunological monitoring of E6 and E7 vaccination trials.

Nuclear RNA accumulations contain released transcripts and exhibit specific distributions with respect to Sm antigen foci

RNA polymerase II transcripts accumulate within mammalian nuclei at distinct sites and exhibit varying morphology. Certain RNA species are organized in elongated structures, whereas others appear as dot-like concentrations. To analyze the status of the RNA within these accumulations, we investigated the composition of accumulations derived from Epstein-Barr virus (EBV) genes, human papilloma virus 18 (HPV18) open reading frames E6 and E7, as well as heat shock protein 89a (hsp89alpha) and 89beta (hsp89beta) genes. No differential distribution of exon and intron sequences within concentrations of EBV RNA could be observed. Whereas accumulations of hsp89alpha and hsp89beta always coincided with Sm antigen foci, the RNA of EBV and HPV18 never co-localized with these foci. This excludes Sm antigen foci as the only sites of splicing and suggests gene-specific variation in the nuclear localization of transcripts. Two sets of experiments were performed to assess whether transcripts in the RNA accumulations are in statu nascendi or products released from a discrete gene locus. Because RNA transcripts derived from EBV genes, which are located on both ends of the genome, were all distributed along the entire length of the RNA signals, they cannot be derived from a highly decondensed genomic DNA extending throughout elongated RNA accumulations. Furthermore, removal of labeled RNA sequences and subsequent visualization of DNA confirmed the confinement of the genomic sequences to a small subregion of the area occupied by accumulated RNA. Therefore, this study supports the view of RNA accumulations as a stream of molecules that delineate a path from a dot-like gene locus toward the nuclear envelope for export into the cytoplasm.

Complex genomic rearrangement within the 12q15 multiple aberration region induced by integrated human papillomavirus 18 in a cervical carcinoma cell line

Human papillomavirus (HPV) DNA is integrated into the host genome in cervical cancer. The cervical carcinoma cell line SW756 has integrated HPV-18 DNA in chromosome region 12q15, in the papillomavirus-associated locus-2 (PAL2). By polymerase chain reaction and hybridization of an arrayed cosmid library with oligonucleotides from the rearranged allele, we determined the pre-integration germline structure of the region. PAL2 was located approximately 10 kb from sequence-tagged site marker U27131, which was the marker most proximal to the 3' flank of the integrated viral DNA. HPV-18 DNA integration induced a complex genomic rearrangement resulting in inversion and deletion of cellular sequences. PAL2 is within the multiple aberration region, which has been shown to be affected in several types of benign tumors of mesenchymal origin. The integrated viral DNA was located 50 kb from a CpG island and 150 kb upstream of the high-mobility group I-C (HMGI-C) gene. The HMGI-C gene and the integrated HPV-18 DNA had opposite transcriptional orientations. No overexpression or altered message of the HMGI-C gene was detected in three cervical carcinoma cell lines. The integrated viral DNA did not affect any other known gene in the region and may be a marker for an unknown gene associated with malignant tumor phenotypes.

Identification and location of human papillomavirus type 16 antisense early promoter and characterisation of antisense RNA

Antisense RNA sequences of various regions of human papillomavirus type 16 (HPV 16) were previously found in a number of cervical lesions, but the viral or cellular promoter has not been identified. HPV 16 E7 oncogene antisense transcripts expressed from an antisense promoter in viral DNA were found in the present study by RNase protection assays for total and cytoplasmic RNA. The antisense promoter for these transcripts was located within HPV 16 nt 4030-4230 by deletion analyses. The results also suggested that most of the antisense RNA was relatively short. The antisense promoter of HPV 16 was functional for expression of antisense RNA of a heterologous gene. Antisense-sense double-stranded E7 RNA was detected, and the sense RNA of this duplex was apparently inefficient for splicing or cleavage/poly(A) addition. These results show that HPV 16 can produce early region antisense RNA, which is from a promoter within a defined region of the viral genome. The possible importance of these transcripts for the regulation of episomal HPV 16 gene expression in infected and premalignant lesions and the possible importance of their deregulation for expression in malignant lesions are discussed.

Detection of human papillomavirus in esophageal squamous cell carcinoma

BACKGROUND

Human papillomavirus (HPV) DNA has been identified in esophageal carcinomas. However, the incidence of HPV varies significantly in different geographic locations. In the current study, neoplasms from two separate geographic regions were analyzed for the presence of HPV DNA:

METHODS

One hundred and ten esophageal squamous cell carcinomas, 83 from Beijing, China and 27 from Cincinnati, Ohio, were examined for the presence of HPV DNA: In situ hybridization and polymerase chain reaction (PCR) using both consensus primers for the HPV L1 gene and type specific primers for the E6 gene of HPV types 6, 16, and 18 were performed.

RESULTS

In situ hybridization failed to demonstrate any HPV type (6, 11, 16, 18, 31, 33, or 35) in any tumor specimen. Likewise, PCR using consensus primers for the HPV L1 gene was negative in all samples. Three of the Chinese specimens (4.29%) were positive for HPV using E6 type specific primers. One tumor contained HPV type 6 DNA, whereas the other 2 contained HPV type 16 DNA. One Cincinnati tumor (4.35%) was positive for HPV 16 by type specific primer. None of the specimens contained HPV 18 DNA.

CONCLUSIONS

The incidence of HPV DNA in esophageal carcinoma specimens from Beijing, China and Cincinnati, Ohio is similar. The incidence of HPV in tumors from Beijing is significantly lower than that reported for those from other regions of China where the incidence of esophageal cancer is higher. Thus, although HPV may play a role in esophageal carcinogenesis, this role may be more pronounced in those regions of the world with a high incidence of the disease, and may be less important in areas with moderate or low risks for esophageal cancer.

Detection of human papillomavirus in esophageal squamous cell carcinoma

BACKGROUND

Human papillomavirus (HPV) DNA has been identified in esophageal carcinomas. However, the incidence of HPV varies significantly in different geographic locations. In the current study, neoplasms from two separate geographic regions were analyzed for the presence of HPV DNA:

METHODS

One hundred and ten esophageal squamous cell carcinomas, 83 from Beijing, China and 27 from Cincinnati, Ohio, were examined for the presence of HPV DNA: In situ hybridization and polymerase chain reaction (PCR) using both consensus primers for the HPV L1 gene and type specific primers for the E6 gene of HPV types 6, 16, and 18 were performed.

RESULTS

In situ hybridization failed to demonstrate any HPV type (6, 11, 16, 18, 31, 33, or 35) in any tumor specimen. Likewise, PCR using consensus primers for the HPV L1 gene was negative in all samples. Three of the Chinese specimens (4.29%) were positive for HPV using E6 type specific primers. One tumor contained HPV type 6 DNA, whereas the other 2 contained HPV type 16 DNA. One Cincinnati tumor (4.35%) was positive for HPV 16 by type specific primer. None of the specimens contained HPV 18 DNA.

CONCLUSIONS

The incidence of HPV DNA in esophageal carcinoma specimens from Beijing, China and Cincinnati, Ohio is similar. The incidence of HPV in tumors from Beijing is significantly lower than that reported for those from other regions of China where the incidence of esophageal cancer is higher. Thus, although HPV may play a role in esophageal carcinogenesis, this role may be more pronounced in those regions of the world with a high incidence of the disease, and may be less important in areas with moderate or low risks for esophageal cancer.

Molecular analysis of cellular loci disrupted by papillomavirus 16 integration in cervical cancer: frequent viral integration in topologically destabilized and transcriptionally active chromosomal regions

To discern the structural features of cellular loci that are disrupted by type 16 human papillomavirus (HPV-16) integration in cervical cancer, a polymerase chain reaction (PCR)-based strategy was employed for direct amplification and sequence analysis of four such cellular loci in cancer biopsy samples. One of the HPV-16-disrupted loci was found to be the microtubule-associated protein (MAP-2) gene and the other three loci were uncharacterized and were designated PID-1 to -3 (for papillomavirus integration-disrupted). The junctional sequences of the viral integration sites in the four loci analyzed are bracketed by long tracts of homogeneous purine or pyrimidine or alternating purine-pyrimidine which are known to destabilize the B-form conformation of the DNA structure. Using a panel of human/hamster hybrid cell DNAs and PCR analysis, the four loci were assigned to chromosomes 2 (MAP-2), 9 (PID-1), 1 (PID-2) and 8 (PID-3), respectively. These chromosomes carry numerous other previously determined viral integration and chromosomal fragile sites and the myc oncogenes. The PID-1 locus was further found in Southern analysis to be rearranged and amplified in another cervical cancer biopsy and a cervical carcinoma cell line (CaSki). On Northern analysis, the PID-1 and -3 probes detected a 3.0- and a 3.6-kb transcript, respectively, in normal cervical cells and in cervical cancer cell lines. The findings suggest that HPV-16 genome integrates frequently into topologically destabilized and transcriptionally active chromosomal sites. It remains to be elucidated whether the MAP-2 and the PID loci contribute to the pathogenesis of cervical cancer.

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.

Normal human chromosome 2 induces cellular senescence in the human cervical carcinoma cell line SiHa

For identification of the chromosome carrying cellular senescence-inducing activity, normal human chromosome 2, 3, 6, 7, 9, 11, or 12 tagged with a selectable marker gene (neo) was introduced into the human cervical carcinoma cell line SiHa via microcell-mediated chromosome transfer. Seventy-six percent (158/207) of the G418-resistant clones obtained by the transfer of chromosome 2 showed a remarkable change in morphology (cells were flat), and 93% (147/158) of them ceased to divide (senesced) prior to 6-9 population doublings, whereas most of the clones generated by the transfer of other chromosomes exhibited a morphology similar to that of the parental cells and continued to grow. Chromosome analyses suggested that cells which escaped from senescence contained only a small fragment derived from the transferred chromosome 2, whereas the transferred chromosomes were apparently intact in most of the continuously growing microcell hybrids with introduction of other chromosomes. These results indicate that the normal human chromosome 2 carries a gene or genes that induce cellular senescence in SiHa cells.

Clinical application of HPV typing in cervical cancer

Certain human papaillomavirus (HPV) types are major risk factors for the development of cervical neoplasia. The value of HPV DNA testing in the management of patients with disease and in population screening is a subject of controversy. Since the introduction of molecular biology into the HPV field, there have been rapid advances and improvements in HPV diagnosis. The various molecular diagnostic methods for detection of HPV DNA (dot blot hybridization, Southern blot hybridization, in situ hybridization, Hybrid Capture Test, and polymerase chain reaction; PCR) could be selected by taking into consideration some factors such as characteristics of sample, sensitivity of HPV test and expenses. The HPV DNA testing would be a clinically useful diagnostic method, when used in conjunction with the Pap smear in population screening or in conjunction with cytology and colposcopy to identify the women infected with high-risk HPVs or women who had equivocal cervical lesions. Despite the confusion, a multitude of reports demonstrate that HPV DNA testing has the clinical utility, and future investigations should be directed at more accurately delineating its role in human health care.

Detection of human papillomavirus DNA in colorectal carcinomas by polymerase chain reaction

Human papillomaviruses (HPVs) are associated with a number of benign and malignant neoplasms. To substantiate the relationship between HPV DNA and colorectal carcinomas, 70 carcinomas and 37 adenomas were analysed in this study. Specific types of HPV DNA in colorectal tumours were detected by polymerase chain reaction (PCR) and Southern blot hybridisation. HPV DNA was detected in 11 of 37 (29.7%) adenomas and in 52.9% 37 of 70 (52.9%) of carcinomas. The expression of HPV DNA in adenomas and carcinomas, especially that of HPV 16 in HPV positive cases (4 of 11 v 26 of 37), was significantly different (p < 0.05). There was no correlation, however, between HPV and the location, differentiation, stage, or survival of malignant neoplasms. These data suggest that HPV DNA, especially type 16, is associated with colorectal carcinogenesis.

Nuclear proto-oncogene products transactivate the human papillomavirus type 16 promoter

Human papillomavirus (HPV) type 16 and 18 viral genomes are frequently detected in cervical and penile cancer biopsies. Although this strongly suggests a prominent role for HPV infection in the development of genital cancer, other genetic or environmental factors are also involved. Genital cancer is postulated to result from loss of cellular control functions, which leads to an unregulated expression of HPV oncogenic proteins. In our study, we determined the trans-activating properties of nuclear proto-oncogene proteins c-Fos, c-Jun and c-Myc on P97 enhancer/promoter activity of HPV16. Using a CAT-reporter construct containing the HPV16 enhancer/promoter element, we investigated the trans-activating effects of c-Fos, c-Jun, c-Myc, and E2 in cervical HT-3 cells. c-Fos and c-Jun overexpression resulted in a 3.3- and 3.1-fold up-regulation of CAT activity. Only 2-fold induction was determined by co-transfection with c-myc and the viral transcription factor E2. Based on these findings, we investigated the expression of HPV DNA (16 and 18) as well as nuclear proto-oncogenes (c-fos, c-jun and c-myc) in nine cervical cancers by in situ hybridisation. In six out of nine carcinomas, HPV16 and/or HPV18 DNA was detectable. All tumours showed an intense and homogeneous expression of c-fos and c-jun mRNA, while the signal for c-myc was detectable only in four specimens. These data suggest that deregulation of nuclear proto-oncogene expression may contribute to an overexpression of HPV-derived oncogenic proteins (E6 and E7), which is generally hypothesised to be an important step in the malignant transformation of HPV-associated tumours.

Recurrent anaplastic ependymoma with an abnormal karyotype and c-myc proto-oncogene overexpression

Cytogenetic analysis on a supratentorial, recurrent, anaplastic ependymoma from a 29-year-old female disclosed the presence of an abnormal clone with the karyotype 46,XX,der(8)t(8;11)(q24;p11),-11,add(?)t(?;11)(?;q13). By the Northern hybridization assay and immunohistochemical staining, tumor cells revealed overexpression of c-myc proto-oncogene, although no evidence of amplification or structural rearrangement of this gene was found.

The relationship of human papillomavirus to proliferation and ploidy in carcinoma of the anus

BACKGROUND

Human papillomavirus (HPV) infections have been implicated in anogenital neoplasia in both sexes. In this study, the authors postulated that HPV infections induce squamous epithelium to become hyperproliferative and aneuploid.

METHODS

To test this hypothesis, formalin fixed, paraffin embedded tissues were analyzed for the presence of HPV by in situ hybridization. S-phase fraction and DNA content were evaluated by flow cytometry. Proliferative indices also were analyzed using an antibody to proliferating cell nuclear antigen (PCNA).

RESULTS

Human papillomavirus DNA was present in 48.1% of the carcinomas. All but one HPV-positive tumor contained HPV 16/18 DNA. The remaining tumor contained only HPV 6/11. No correlation was found between HPV status, patient age, or tumor differentiation. Thirty-three percent of tumors were aneuploid. Only two patients had aneuploid tumors that were HPV-negative; these patients received preoperative radiotherapy. The average S-phase fraction was significantly higher (P < 0.01) in HPV-positive versus HPV-negative lesions. The PCNA index for HPV positive tumors was also significantly higher than that observed in negative tumors (p < 0.003).

CONCLUSION

The presence of HPV in tumor cells is significantly associated with an increased proliferative rate and aneuploid status of tumors compared with HPV-negative tumors. These findings are consistent with the fact that viral proteins binding to tumor suppressor gene proteins can deregulate the cell cycle and lead to genomic instability.

Detection of human papillomavirus in oral lesions using commercially developed typing kits

Biopsy material from 20 oral lesions (19 condylomas and 1 squamous papilloma) previously shown to contain human papillomavirus (HPV) 6 and HPV 11 sequences by in situ hybridization were examined using 3 commercially available HPV typing kits. Sensitivity and specificity were compared with in-house methods. Previous in situ hybridization had detected HPV 6b in 11 (55%) of the biopsies, HPV 6 and 11 in 7 (53%) and HPV 11 alone in 1 biopsy. Only one of the commercial assays (assay 1) detected HPV in all 20 biopsies (11 positive for HPV 6b only, 1 for HPV 11 only and 7 for HPV 6b and 11). The wide spectrum probe of assay 2 detected HPV in only 10 (50%) of the biopsies, and in a further 2 biopsies the hybridization results were difficult to interpret because of background staining. Assay 3 used a combined HPV 6/11 probe and detected HPV in 15 (75%) of the biopsies. Clear hybridization signals were demonstrated in the intermediate and upper layers only of squamous epithelium, as expected from the known association of HPV replication with epithelium differentiation. In most specimens background levels were not a problem, and all commercial assays were easy to use. The findings are discussed in the context of the digestion procedures, sensitivity of the probes provided and the conditions of hybridization, all of which would influence the detection of HPV.

Surrogate endpoint biomarkers for cervical cancer chemopreventive trials

Cervical intraepithelial neoplasia (CIN) represents a spectrum of epithelial changes that provide an excellent model for developing chemopreventive interventions for cervical cancer. Possible drug effect surrogate endpoint biomarkers are dependent on the agent under investigation. Published and preliminary clinical reports suggest retinoids and carotenoids are effective chemopreventive agents for CIN. Determination of plasma and tissue pharmacology of these agents and their metabolites could serve as drug effect intermediate endpoints. In addition, retinoic acid receptors could serve a both drug and biological effect intermediate endpoints. Possible biological effect surrogate endpoint biomarkers include cytomorphological parameters, proliferation markers, genomic markers, regulatory markers, and differentiation. Given the demonstrated causality of human papillomavirus (HPV) for cervical cancer, establishing the relationship to HPV will be an essential component of any biological intermediate endpoint biomarker. The pathologic effect surrogate endpoint biomarker for cervical cancer is CIN, used clinically for years. The desired effect for chemopreventive trials is complete regression or prevention progression. In planning chemoprevention trials, investigators need to consider spontaneous regression rates, the subjective nature of detecting CIN, and the impact of biopsy on regression. If intermediate endpoint biomarkers that met the above criteria were available for cervical cancer, then new chemopreventive agents could be rapidly explored. The efficacy of these new agents could be determined with a moderate number of subjects exposed to minimal risk over an acceptable amount of time. The impacts on health care for women would be significant.

Detection of human herpesvirus 6 and human papillomavirus 16 in cervical carcinoma

A subset of human papillomaviruses (HPVs) is associated with the majority of cervical cancers; however, cofactors appear to be required for carcinogenic progression of HPV-induced neoplasia. As human herpesvirus-6 (HHV-6) was recently shown to infect cervical epithelial cells in vitro and activate transcription of HPV-transforming genes, human cervical dysplasia and cancers were analyzed for the presence of HHV-6 by multiple methods, including polymerase chain reaction, slot blot, Southern blot, and in situ hybridization. HHV-6 DNA sequences were detected in 6 of 72 cases of squamous cervical carcinoma and cervical intraepithelial neoplasia. HPV-16 was found in four of the HHV-6-positive cases (two squamous cervical carcinomas and two cervical intraepithelial neoplasias). None of the 30 normal cervices and biopsies of patients with cervicitis was positive for HHV-6 DNA. These results are the first suggestion of an in vivo association between HHV-6 and some cervical neoplasia.

Analysis of deletion of the integrated human papillomavirus 16 sequence in cervical cancer: a rapid multiplex polymerase chain reaction approach

A protocol for a rapid physical mapping of the integrated type 16 human papillomavirus (HPV16) sequences in biopsied and paraffin-embedded archival cervical cancer samples is described. The procedure involves the use of an anchor primer and a mixture of indicator primers in a multiplex polymerase chain reaction (PCR). A minimal conserved region of viral integration of 2,745 bp in length has been mapped between nucleotide (nt) 6102-941, containing the entire regulatory region and the E6 and E7 open reading frames (ORFs). A general deletion domain of 1,465 bp in the integrated viral genome has been defined between nt 1417-2881, covering most of the E1 ORF at the 3'-half and 60 bp at the 5' terminus of the E2 ORF. This common deleted sequence contains an ATPase active domain speculated to be associated with a DNA helicase function essential for the viral replication, and it also falls within the actively spliced E1-E2 segment of the primary RNA transcripts. Detection of the loss of the 3'-half of the E1 ORF would be an ideal marker for PCR-based rapid determination of HPV integration in cervical cancer cells.

Global DNA hypomethylation increases progressively in cervical dysplasia and carcinoma

BACKGROUND

Global DNA hypomethylation has been observed in some human neoplasms and has been implicated as an important factor in carcinogenesis. The current study was designed to assess whether DNA hypomethylation occurs in cervical dysplasia and cancer, and to determine the relationship between the degree of DNA hypomethylation and the grade of neoplasia.

METHODS

Cervical biopsy specimens were obtained from colposcopically identifiable lesions in 41 patients with abnormal Pap smear results. The extent of global DNA methylation was assessed by incubating the extracted DNA with [3H]-S-adenosylmethionine and Sss1 methyltransferase, an enzyme that specifically catalyzes the transfer of methyl groups to cytosine residues in the cytosine-guanine doublet. The degree of exogenous 3H-methyl group incorporation into the DNA therefore is related reciprocally to the extent of endogenous DNA methylation. These data were compared with the histopathologic classification of the lesions.

RESULTS

The extent of 3H-methyl group incorporation was increased threefold and sevenfold in the DNA from cervical dysplasia and cancer, respectively, compared with the DNA from normal cervical tissue (P = 0.006, analysis of variance). Significant incremental increases in DNA hypomethylation were observed in the progression from normal and low grade squamous intraepithelial lesions (SIL) to high grade SIL and to cancer (P < 0.0001, trend).

CONCLUSIONS

These data show that global DNA hypomethylation is a significant epigenetic event in cervical carcinogenesis and that the degree of DNA hypomethylation increases with the grade of cervical neoplasia. These data suggest that global DNA methylation may serve as a biochemical marker of cervical neoplasia.

Laser scanning confocal microscopy and quantitative microscopy with a charge coupled device camera improve detection of human papillomavirus DNA revealed by fluorescence in situ hybridization

Epithelial cervical CaSki, SiHa and HeLa cells containing respectively 600 copies of human papillomavirus (HPV) DNA type 16, 1-2 copies of HPV DNA type 16 and 10-50 copies of HPV DNA type 18 were used as model to detect different quantities of integrated HPV genome. The HPV DNA was identified on cell deposits with specific biotinylated DNA probes either by enzymatic in situ hybridization (EISH) or fluorescence in situ hybridization (FISH) involving successively a rabbit anti-biotin antibody, a biotinylated goat anti-rabbit antibody and streptavidin-alkaline phosphatase complex or streptavidin-fluorescein isothiocyanate complex. With brightfield microscopy and EISH, hybridization spots were observed in CaSki and HeLa cells but hardly any in SiHa cells. With fluorescence microscopy and FISH, hybridization spots were clearly seen only on CaSki cell nuclei. In an attempt to improve the detection of low quantities of HPV DNA signals revealed by FISH, laser scanning confocal microscopy (LSCM) and quantitative microscopy with an intensified charge coupled device (CCD) camera were used. With both LSCM and quantitative microscopy, as few as 1-2 copies of HPV DNA were detected and found to be confined to cell nuclei counterstained with propidium iodide. Under Nomarski phase contrast, a good preservation of the cell structure was observed. With quantitative microscopy, differences in the number, size, total area and integrated fluorescence intensity of hybridization spots per nucleus were revealed between CaSki, SiHa and HeLa cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined effects of human papillomavirus-18 and N-methyl-N'-nitro-N-nitrosoguanidine on the transformation of normal human oral keratinocytes

We immortalized oral keratinocytes by transfecting them with recombinant human papillomavirus (HPV) type 18 DNA and established three cell lines. These lines were morphologically different from their normal counterpart, contained integrated entire HPV-18 DNA, and expressed the viral E6/E7 genes. The cells contained less p53 protein and more c-myc mRNA than normal cells. However, they proliferated only in keratinocyte growth medium (KGM) containing low calcium and were not tumorigenic in nude mice. To test the hypothesis that tumors result from the combined effect of a "high-risk" HPV and chemical carcinogens in the human oral cavity, we exposed the immortalized cells to the chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine. Three chemically transformed cell colonies were isolated. These cells (a) proliferated well in both KGM and Dulbecco's modified minimum essential medium containing physiological levels of calcium; (b) were capable of proliferating in nude mice; (c) contained intact, integrated HPV-18 sequences; (d) transcribed substantially more HPV-18 E6/E7, transforming growth factor-alpha, and c-myc than the immortalized counterpart; and (e) contained, like the immortalized counterpart, less wild-type p53 protein and DCC message. These data indicate that human oral keratinocytes can be transformed by sequential exposure of normal keratinocytes to a "high-risk" HPV and chemical carcinogens.

Transgenic models of retinoblastoma: what they tell us about its cause and treatment

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Integration site of human papillomavirus type-18 DNA in chromosome band 8q22.1 of C4-I cervical carcinoma: DNase I hypersensitivity and methylation of cellular flanking sequences

The C4-I cell line derived from a non-keratinizing squamous cell carcinoma of the uterine cervix contains integrated human papillomavirus-18 DNA. Fluorescence in situ hybridization of C4-I cells demonstrated a single viral integration site at 8q22.1 on a derivative chromosome originating from an 8q;12q translocation. 8q22 is a site of chromosome fragility and is also recombinogenic in several human malignancies. DNase I hypersensitivity of the integration site was studied with a cellular flanking probe. A hypersensitive site was detected within 3 kb from viral DNA. The integration sites are undermethylated in C4-I and HeLa cells and fully methylated in tumor cell lines of other origin, such as lymphoid cells.

Human papillomavirus 16 DNA in NIH3T3 cells transformed by colonic cancer cellular DNA

Human papillomavirus (HPV) 16 DNA is closely associated with human cancers. It has been identified as an aetiological agent in cervical cancers and, recently, in colonic neoplasms. To further understand the role of HPV 16 DNA in colorectal carcinogenesis, NIH3T3 cells were transformed with high molecular weight DNA from colonic cancer cells and the expression of HPV 16 DNA detected. Both human Alu and HPV 16 DNA sequences were found in the type II foci of CC-M2T cells by Southern blot hybridisation. Additionally, 100% tumorigenicity in nude mice was seen. This study shows the transfection of HPV DNA from colonic cancers into NIH3T3 mouse cells and suggests that HPV type 16 might be associated with the malignant transformation of colonic cells.

Partial phenotypic reversion of HeLa cells by long-term interferon-alpha treatment

Human papillomaviruses (HPV) are associated with malignant cervical neoplasia. Several HPV-related diseases have been shown to be sensitive to interferon (IFN) treatment. HeLa cells contain and express the HPV type 18 genome and were used as a model for the evaluation of the viral expression regulation and the effect on the malignant phenotype during IFN treatment. Cells were treated continuously with 200 IU/ml IFN-alpha 2b or natural leukocyte INF-alpha for six passages (42 days). Some IFN-induced changes were observed: decrease of HPV-18 mRNA expression, changes of cell morphology, and reduction of clonogenicity in soft agar. Tumorigenicity in nude mice was not modified. Other targets of the IFN system were analyzed, and an increase of the 2',5'-oligoadenylate synthetase mRNA level and a down-regulation of type I IFN receptor were found. These results demonstrate that long-term IFN-alpha treatment induces a partial phenotypic reversion of HeLa cells to a more differentiated stage were down-regulation of HPV-18 expression could play a central role. It therefore confirms that the IFN-alpha treatment may be therapeutically useful in cervix cancer produced by HPV-18.

Characterization of human bone marrow-derived closed circular DNA clones

Because of interest in mechanisms of recombination involved in chromosomal deletions in neoplastic disease, and their relation to possible rearrangements in normal tissues, we are studying circular DNA molecules from human tissue with a long-term goal of investigating them as possible by-products of physiologically relevant intrachromosomal recombination events. Covalently closed circular (ccc) DNA from human bone marrow was cloned in bacteriophage vectors, and fourteen clones chosen randomly from the cccDNA-derived library were characterized. Five clones originated from chromosome-specific centromeric alpha-satellite DNA; two clones carried highly repetitive sequences probably derived from interspersed repetitive elements; six clones were derived from single-copy chromosome-specific sequences which detected homologous rodent sequences; and one clone (EPM10) was derived from a small chromosome 11-specific sequence family which localized to chromosome regions 11cen and 11q14. Oligonucleotide primers derived from the cccDNA clones were used in polymerase chain reaction studies to show that (1) the EPM10 clone carried the circular junction, (2) several of the single-copy products could be detected in three different bone marrow cccDNA preparations, and (3) the Alu-PCR profile for bone marrow cccDNA showed distinct bands which were similar in four bone marrow cccDNA preparations.