Presence of human papillomavirus type-16 and type-18 DNA sequences and their expression in cervical cancers and cell lines from Japanese patients

Head and neck cancer: from research to therapy and cure

Cumulative findings from many research groups have identified new signaling mechanisms associated with head and neck cancers. We summarize these findings, including discussion of aberrant NOTCH, PI3K, STAT3, immune recognition, oxidative pathway, and regulation of cell cycle and cell death. The genomic landscape of head and neck cancers has been shown to differ depending on human papillomavirus (HPV) status. We discuss studies examining the integration of HPV into genomic regions, as well as the epigenetic alterations that occur in response to HPV infection, and how these may help reveal new biomarker and treatment predictors. The characterization of premalignant lesions is also highlighted, as is evidence indicating that the surgical removal of these lesions is associated with better clinical outcomes. Current surgical methods are also discussed, including several less aggressive approaches such as minimal invasive robotic surgery. While much remains to be done in the fight against head and neck cancer, continued integration of basic research with new treatment options will likely lead to more effective therapeutic strategies directed against this disease.

Cervical human papillomavirus screening by PCR: advantages of targeting the E6/E7 region

PCR is a promising method for detection of human papillomavirus (HPV), the high-risk forms of which are responsible for cervical cancer. PCR primers that target the L1 or E1 region can be unreliable and may miss more advanced disease, whereas those directed at the E6 or E7 regions, which encode oncogenic products, are preferable because 1) the LI/E1 regions, but never the E6/E7 regions, are lost during integration of viral DNA into host genomic DNA, a process that can represent an integral component of progression from infection to tumorigenesis; and 2) the E6/E7 nucleotide sequence exhibits less nucleotide variation. The choice of region used for PCR has implications for HPV screening strategies in the clinical diagnosis and management of cervical cancer.

Pharmacotherapy of recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) is a disease which affects both children (juvenile-onset RRP) and adults (adult-onset RRP). While a greater amount of information is known about the epidemiology of juvenile-onset than adult-onset RRP, fundamental work is still needed to more fully describe areas such as the mode of transmission. The primary management approach focuses on the removal of the papillomas by surgical debulking, although persistence of the human papillomavirus genome and subsequent recurrence of disease is the typical outcome. In a minority of patients, surgical management must be supplemented with adjuvant medical therapy, with IFN being the best studied and most commonly used. Other adjuvant treatments being employed include photodynamic therapy, indole-3-carbinol, ribavirin and cidofovir. Large controlled trials are lacking for all but IFN, making it extremely difficult to assess clinical benefit and risk in a systematic fashion at the current time. As with surgical management, viral persistence occurs following treatment with these adjuvant modalities, further contributing to the challenge of managing patients with this potentially devastating disease.

Involvement of herpes simplex type 2 in modulation of gene expression of human papillomavirus type 18

Human papillomaviruses (HPVs) and herpes simplex virus type 2 (HSV-2) can establish latent or persistent infections in the host, and are involved in the aetiology of benign and/or malignant lesions of the urogenital tract. To investigate the putative interaction between these DNA viruses when a double infection occurs, we have studied the effect of HSV-2 infection in HeLa 229 cells containing 10-50 copies of HPV type 18 genomic DNA. Twenty hours post HSV-2 infection, the analysis of mRNA transcripts from E1, E2, E6 early and L1 late HPV18 genes was performed in HeLa cells by a semi-quantitative RT-PCR assay. A modulation of HPV18 E1 and E6 early genes was observed, resulting in a 9-fold and 3-fold increased transcription respectively.

Juvenile onset recurrent respiratory papillomatosis: possibilities for successful antiviral therapy

Recurrent respiratory papillomatosis (RRP) is a potentially devastating disease that can have significant morbidity, and can even result in mortality due to airway compromise or, less commonly, malignant transformation. Two distinct types of RRP exist: adult-onset RRP (AO-RRP) and juvenile-onset RRP (JO-RRP). Acquisition of human papillomavirus (HPV), the causative agent of RRP, is believed to occur in the peripartum period in the case of JO-RRP, with disease symptoms (primarily hoarseness) becoming apparent during the first several years of life. Treatment currently consists of surgical debulking of the papillomas to relieve airway obstruction. However, numerous antiviral therapies have also been evaluated, albeit primarily under uncontrolled settings. This article will review the biology, natural history and management of HPV infection, with particular emphasis on JO-RRP.

Analysis by multiplex PCR of the physical status of human papillomavirus type 16 DNA in cervical cancers

Integration of human papillomavirus (HPV) DNA occurs early in cancer development and is an important event in malignant transformation of cervical cancer. Integration of HPVs preferentially disrupts or deletes the E2 open reading frame, which results in the loss of its expression. The preferential disruption of the E2 gene causes the absence of the E2 gene sequences in the PCR product following integration. Twenty-two carcinomas positive for HPV type 16 (HPV-16) DNA were first tested for the disruption of the E2 gene by PCR. A specific fragment of the E2 gene was not amplified in 10 cases, suggesting integration of HPV DNA into the host genome. Next, multiplex PCR for the HPV E2 and E6 genes was carried out in the remaining 12 cases. Copy numbers of both genes should be equivalent in episomal forms, while the E2 gene copy number will be smaller than that for E6 following the preferential disruption of the E2 gene in concomitant forms. Although relative ratios of HPV E2 to E6 PCR products (E2/E6 ratios) ranged from 1.40 to 2.34 in 10 of 12 cases, multiplex PCR products from 2 cases displayed extremely low ratios of 0.69 and 0.61. Southern blot hybridization with an HPV-16 probe revealed that only in these two cases was both episomal and integrated HPV DNA being carried simultaneously. Thus, multiplex PCR for the E2 and E6 genes of HPV-16 DNA following PCR for the E2 gene can distinguish the pure episomal form from a mixed form of episomal and integrated HPV DNA. Clinical application of this technique will help researchers to understand the implication of the integration of HPV DNA for cervical carcinogenesis and cervical cancer progression.

Human papillomavirus and mixed epithelial tumors of the endometrium

Strong epidemiological evidence links human papilloma viruses (HPV) with the development of cervical intraepithelial neoplasia (CIN) and invasive cancers of the uterine cervix. The localization of HPV DNA sequences high up in the female genital tract (in benign and malignant lesions) is not that uncommon, but its precise significance is uncertain. In particular, the detection of HPV DNA sequences by polymerase chain reaction (PCR) needs careful interpretation, because the source of the amplicon may emanate from tumor cells, direct contamination from the cervix, or possibly from extratumoral sites in the endometrium. We have previously reported the identification of koilocyte-like changes in the squamous epithelium of some endometrial adenoacanthomas. Adenoacanthomas (adenocarcinoma with squamous metaplasia) are mixed epithelial tumors arising in the endometrium composed of malignant glandular areas admixed with benign metaplastic squamous epithelium. The rarer adenosquamous carcinoma containing both malignant glandular and squamous areas is also described. The origin of benign/malignant squamous epithelial islands in endometrial tumors has been the subject of speculation, with some investigators considering an origin from metaplastic glandular endometrial cells. In this study, we examined 10 normal endometrial samples, 20 adenocarcinomas, 41 adenocarcinomas with squamous metaplasia, and two adenosquamous carcinomas, (including control cervical material where possible) for the presence of HPV DNA sequences using nonisotopic in situ hybridization (NISH), type-specific HPV PCR, general primer PCR (to detect sequenced and unsequenced HPVs), and PCR in situ hybridization (PCR-ISH). We did not identify HPV DNA sequences in normal endometrial tissue. In adenocarcinomas (endometrioid type), HPV was only identified in 2 of 20 cases by PCR, both of which were HPV 11 positive. We were unsuccessful in identifying HPV in endometrial carcinomas by NISH or by PCR-ISH, raising the possibility of contamination from the cervix in the two positive cases. In adenoacanthomas, a low-risk HPV type (HPV 6) was found in 19 of 41 cases. NISH signals were intranuclear in location in squamous regions of adenoacanthomas. Additional positive nuclei were uncovered using PCR-ISH, which increases the sensitivity of standard NISH detection. HPV DNA sequences were located in some malignant endometrial glandular epithelial cells, but this accounted for a minority of samples. HPV DNA sequences were not detected in extraepithelial sites. Mixed infection by two different HPV types was identified in two cases. Most cases showed similar HPV types in cervical and endometrial lesions, although discordant cases were uncovered. In adenosquamous carcinomas, one case showed mixed infection with HPV 6 and 33 by PCR. The apparent segregation of low-risk HPV type (HPV 6) with benign squamous metaplastic epithelium in adenocarcinoma with squamous metaplasia, and high-risk type (HPV 33) with malignant squamous epithelium in adenosquamous carcinoma, raises important questions in relation to the role of HPVs in mixed epithelial tumors of the endometrium and their interplay in the pathogenesis of squamous metaplasia at extracervical sites.

The high risk human papillomaviruses and oral cancer: evidence for and against a causal relationship

Oncogenic human papillomaviruses (HPVs) have been detected in oral squamous cell carcinoma (SCC). HPV16 is the most frequently detected HPV type in oral SCC and is present in up to 22% of cases, either alone or in combination with other HPV types. HPV18 is present in up to 14% of cases. HPV16 and HPV18 are present together in approximately 6% of cases. However, HPV16 and 18 are also detected in normal oral mucosae (10% and 11% of subjects, respectively). These data suggest that high risk HPV infection may be a co-factor in oral carcinogenesis and that latent HPV infection of the oral mucosa is common. A role for HPV infection in oral carcinogenesis is supported by the ability of high risk HPVs to immortalize oral keratinocytes in vitro. Immortalization may involve (i) deactivation of pre-formed tumor-suppressor proteins by viral oncoproteins, (ii) blocking of tumor-suppressor gene transcription as a result of HPV oncogene insertion or (iii) stimulation of cellular oncogene transcription by the upstream insertion of HPV-derived transcription activating sequences. Hence, infection of oral keratinocytes with high risk HPV may be involved in the pathogenesis of some oral SCCs although the evidence implicating HPV in oral carcinogenesis is, at present, mainly circumstantial.

Prevalence of human papillomavirus DNA in cervical tissue. Retrospective analysis of 855 cervical biopsies

The histopathologic features of 855 cervical biopsies were correlated with the presence of human papillomavirus DNA using in situ hybridization (ISH) with biotin labeled type specific probes for Human Papilloma Virus (HPV) types 6, 11, 16, 18, 31, 33 and 51. HPV-DNA was found in 18% (13/72) of cervical intraepithelial neoplasia I (CIN I), 30% (35/115) of CIN II, 28% (57(206) of CIN III, in 84% (21/25) of flat condyloma and in 13% (15/112) of normal cervical tissue. HPV DNA was detectable in 11% (5/46) of cervical adenocarcinoma and in 21% (59/279) of squamous cell carcinoma (SCC) of the cervix. High risk HPV types were identified more often than low risk HPV types in CIN I, CIN II, CIN III and SCC. HPV type 16/18 predominates over HPV types 31/33/51 in CIN I, flat condyloma and in SCC. The prevalence of HPV was strongly associated with the grade of differentiation of SCC. It was identified in 59% (23/39) of well differentiated SCC, in 18% (25/142) of moderately differentiated and in 11% (11/98) of poorly differentiated SCC.

Genomic organization of human papillomavirus type 18 in cervical cancer specimens

It has been reported that cervical cancers positive for human papillomavirus (HPV) 18 have a poorer prognosis than those with other HPV types. To gain a better understanding of the aggressive character of HPV 18-positive cancers, we examined the difference in genomic organization between HPV 18 and HPV 16 harbored in cervical cancers. We amplified E1 and E2 genes from 9 HPV 18-positive and 31 HPV 16-positive cervical cancers by polymerase chain reaction (PCR). At least one of the two early genes was missing in 3 out of 9 HPV 18-positive cancers, while both PCRs were positive in all 31 HPV 16-positive cancers (P < 0.05). We then analyzed the 9 HPV 18-positive cancers by 15 contiguous polymerase chain reactions covering collectively the whole HPV 18 genome. In addition to the three with a deletion of the E1 or E2 gene, one had a deletion in the E5 and L2 genes and one had an insertion in the long control region. The frequent alterations in genomic organization, especially preferential deletion of the E1 or E2 gene, may be related to the more aggressive properties of HPV 18-positive cervical cancers.

Association of human papillomavirus with malignant and premalignant lesions of the uterine endometrium

The possible association of human papillomavirus (HPV) with endometrial hyperplasia and endometrial adenocarcinoma was investigated. DNA from frozen tissues of 30 endometrioid carcinomas of Japanese patients was tested for HPV DNA by Southern blot hybridization analysis. Screening with HPV type 58 probe under low stringency conditions showed the presence of HPV DNA in two of 30 endometrioid carcinomas. High stringency hybridization identified HPV type 16 in the two positive specimens. The presence of HPV was further analyzed by polymerase chain reaction (PCR)-Southern blot analysis of DNA from archival tissue blocks of the initial 30 endometrioid carcinomas as well as an additional 17 endometrioid carcinomas and 13 atypical hyperplasias of the endometrium from Japan and 38 endometrioid carcinomas from the United States. Polymerase chain reaction amplification using type 16-specific HPV primers for a portion of the E6 open reading frame was positive in six of 47 (13%) endometrioid carcinomas from Japan, including two in which HPV 16 was not detected by Southern blot analysis and two of 38 (5%) endometrioid carcinomas from the United States. Polymerase chain reaction amplification using L1 consensus sequence primers was positive for HPV in two of 13 (15%) endometrial hyperplasias, 13 of 47 (28%) endometrioid carcinomas from Japan, and six of 38 (16%) endometrioid carcinomas from the United States. Slot blot hybridization identified HPV type 16 in seven of the L1 PCR products, including all but one specimen testing positive for HPV type, 16 using E6 type specific primers. In situ hybridization was positive for HPVs 16/18 in glandular epithelial tumor cells in six of the PCR-positive specimens. An additional specimen showed staining for HPVs 16/18 in acellular luminal debris in association with squamous metaplasia of the tumor, but staining was negative in the glandular cells of the tumor. Human papillomavirus was not detected by in situ hybridization in the remaining specimen, which was PCR positive for HPV 16. In situ hybridization was weakly positive for HPVs 31/33/35 in one specimen and was weakly positive for HPVs 6/11 in benign endometrial epithelial cells but not in tumor cells of another specimen that tested positive for HPV by L1 PCR. Two dimensional gel electrophoresis performed on two specimens showed that HPV DNAs were integrated into cellular DNA with no episomal coexistence. These findings suggest that HPV, especially HPV 16, may play an etiologic role in a fraction of endometrioid adenocarcinomas.

Sequence variation of human papillomavirus type 16 E7 in preinvasive and invasive cervical neoplasias

Variation in the nucleotide sequence of the HPV 16 E7 gene in preinvasive cervical intraepitherial neoplasia (CIN) and invasive cervical carcinoma specimens was analyzed. Direct DNA sequencing of PCR-amplified products with primers different from those used for PCR with 5'-end labeling generated distinct sequence ladders with a low background, even in specimens containing relatively low copy numbers of HPV. Of 14 cervical neoplasias, 11 cases showed sequence diversity from prototype HPV16, and a total of 22 nucleotide exchanges were detected. Nine of these led to single amino acid exchanges: [Thr5] to [Lys5] in one case and [Asn29] to [Ser29] in eight cases. The [Ser29] E7 was distributed uniformly among invasive carcinomas and precancerous legions, and was also found in a normal cervix. The [Lys5] E7 and [Ser29] E7 had transforming potential similar to the prototype E7 assessed by cooperation with the activated ras gene in rat embryo fibroblasts.

Oncogenes, tumor suppressors and viruses in oral squamous carcinoma

The pathogenesis of oral squamous cell carcinoma involves recognised carcinogens in tobacco and/or alcohol but other factors, including viruses, may also have a role. This paper reviews the gene changes revealed in oral carcinoma, the evidence implicating viruses, and mechanisms whereby viruses may affect gene function.

Human papillomavirus detection in cervical adenocarcinoma by polymerase chain reaction

Twenty-five primary cervical adenocarcinomas and five cervical infiltrates from endometrial or rectal adenocarcinomas were analyzed for human papillomavirus (HPV) DNA by polymerase chain reaction with consensus and type-specific primers. Sixty-four percent (16 of 25) of the primary carcinomas and 20% (one of five) of the secondary infiltrates were positive for HPV types 16 and/or 18 DNA. Among the primary tumors HPV DNA was found in 80% of the endocervical cell-type tumors and in 60% of the endometrioid tumors, whereas two undifferentiated scirrhous carcinomas, one clear cell carcinoma, and one serous-papillary tumor were HPV negative. Human papillomavirus-positive patients were younger than HPV-negative patients (mean ages, 49.2 v 64.2 years). Our results indicate that papillomavirus play a major role in the etiology of cervical adenocarcinomas, at least in premenopausal women. However, in contrast to other studies, HPV type 18 was not the predominant type of HPV, HPV types 16 and 18 occurring with similar frequency in our patients.

Simultaneous in situ hybridization for DNA and RNA reveals the presence of HPV in the majority of cervical cancer cells

Thirteen cases of invasive squamous cell carcinoma of the uterine cervix containing HPV types 16 or 18 DNA sequences, as detected by Southern blot analysis, were investigated by in situ hybridization on routine paraffin sections, using 35S nick-translated DNA probes. Simultaneous in situ hybridization for DNA and RNA showed that in ten out of 13 cases (77%) the percentage of tumor cells containing HPV 16 or 18 varied from 75 to 100%. In one case, harboring both in situ and invasive carcinoma, the same type of HPV DNA was detected in both components. This finding suggests that neoplastic cells retained the viral genome during progression to invasiveness.

Viruses in the aetiology of oral carcinoma? Examination of the evidence

This paper examines the evidence for an aetiological role for viruses in the development of oral carcinoma. Several viruses have been sought in oral cancer and evidence found for some, particularly herpes simplex and human papillomavirus. However, the evidence also suggests that these viruses are ubiquitous agents and a number of criteria must be met before these potentially oncogenic agents can reliably be implicated in human carcinogenesis. In contrast, there is no evidence that viruses such as adenovirus, Epstein-Barr virus, and retroviruses play any role in oral carcinogenesis.

Genital-type human papillomavirus infection is not associated with surface epithelial ovarian carcinoma

Tumor tissues from 29 women with borderline or malignant epithelial ovarian tumors were examined for the presence of human papillomavirus (HPV) DNA by the polymerase chain reaction (PCR). The PCR analysis used a set of consensus primers that are complementary to highly conserved sequences in the genital HPVs (M. M. Manos, Y. Ting, D. K. Wright, A. J. Lewis, T. R. Broker, and S. M. Wolinsky, Cancer Cells 7, 209-214, 1989). Amplification products were detected by Southern hybridization with consensus oligonucleotide probes. A total of 70 paraffin-embedded tissue sections from ovarian carcinomas were tested and we did not detect genital-type HPV DNA sequences in any of these specimens. However, all of the tissue specimens were considered adequate for PCR analysis because a human cellular gene (beta-globin) was successfully amplified in each tissue specimen. In addition, HPV 16 DNA was found in a concurrent invasive squamous-cell carcinoma of the cervix from one ovarian cancer patient, indicating that the PCR was able to detect HPV in the lower genital tract of this individual. We conclude that there is no association between infection with the most common genital HPVs and borderline and malignant epithelial ovarian tumors.

Human papillomavirus and c-myc/c-erbB2 in uterine and vulvar lesions

The aim of this study was to investigate papillomavirus (HPV)-DNA in precancer and cancer of the cervix, vulva, and endometrium by in situ/dot blot/Southern blot hybridization and polymerase chain reaction (PCR). Myc/erbB-2 expression was examined by Northern blot analysis. PCR was the most sensitive HPV detection method, demonstrating HPV-DNA in all pre-invasive and invasive cervical lesions (n = 21) and most (3 of 4) vulvar carcinomas in contrast to an overall rate of 60% with other techniques. Particular phenotypes (adenoid cystic/basal cell carcinoma of the vulva, cervical adenocarcinoma) were found to contain HPV. Endometrium harboured HPV not only in two cases of cervical cancer, but also in 3 of 8 primary endometrial carcinomas and 3 of 8 non-malignant conditions. Myc activation was confined to three squamous cell carcinomas, most markedly in one HPV-6-positive verrucous variant. ErbB-2 over-expression was only seen in one HPV-18 infected advanced endometrial tumour. Our findings point to a range of HPV-infected lesions broader than previously supposed and possible contributions of HPV-independent molecular events to carcinogenesis in this field.

Newly established uterine cervical carcinoma cell line with co-amplification of human papillomavirus DNA and c-myc gene

A new human tumor cell line, NCC-c-CX-1 (CX-1), was established from a uterine cervical cancer xenografted in nude mice. This cell line harbored approximately 50 to 100 copies of human papillomavirus (HPV) type 18 DNA per haploid genome, and contained about 16-fold-amplified c-myc gene with rearrangement. These genomic alterations found in CX-1 cells were also present in both primary tumor and xenografted tumor. Histopathologically, original and xenografted tumors were poorly differentiated cancer and were characterized by neuroendocrine features such as positive neuron-specific enolase and chromogranin A by immunohistochemistry and abundant neurosecretory-type granules in the cytoplasm by electron microscopy. However, the established cell line had lost the neuroendocrine features. This cervical cancer cell line may be a useful model for studying cervical carcinogenesis, especially the interaction between HPV and c-myc oncogene.

Purification and characterization of human papillomavirus type 16 E7 protein with preferential binding capacity to the underphosphorylated form of retinoblastoma gene product

Human papillomavirus type 16 E7 is considered to be a major viral oncoprotein playing an important role(s) in cervical cancers. E7 protein was shown to bind to the protein product of the retinoblastoma gene (RB), while simian virus 40 large T and adenovirus E1A were also shown to possess binding activity to RB protein. The RB protein is a cell cycle regulator that is highly phosphorylated specifically in S, G2, and M, whereas it is underphosphorylated in G0 and G1. Recently, large T was demonstrated to bind preferentially to the underphosphorylated RB protein, which is considered to be an active form restricting cell proliferation. However, it is not known whether E7 can bind to phosphorylated RB protein. We successfully purified large quantities of unfused human papillomavirus type 16 E7 protein expressed in Escherichia coli by using a T7 promoter-T7 RNA polymerase system. The purified E7 protein was demonstrated to bind preferentially to the underphosphorylated RB protein.

Human papillomavirus infection and other risk factors for cervical neoplasia: a case-control study

A case control design has been used to investigate risk factors associated with the development of cervical squamous intraepithelial lesions (SIL) in a population of urban women in which non-affluent minority groups were heavily represented. Eighty-five women with histologically confirmed SIL were compared to a control group of 70 cytologically normal women. HPV infection was determined using both Southern blot hybridization and polymerase chain reaction (PCR) amplification specific for HPV types 16, 18, and 33. When Southern blot was used to detect HPV, logistic regression analysis identified HPV infection (odds ratio (OR) = 17.9, 95% confidence interval (CI) = 6.2-51.6) and low educational achievement (OR = 3.4, 95% CI = 1.2-10.1) as major independent risk factors. When PCR was employed to detect HPV, the logistic regression model suggested that HPV infection (OR = 10.4, 95% CI = 3.6-30.4) and Hispanic ethnicity (OR = 5.0, 95% CI = 1.2-20.5) represented independent risk factors; low educational achievement and Black ethnicity were risk factors of borderline significance. PCR detection of simultaneous co-infection with more than one HPV type was associated with a very high risk of SIL (OR for one type = 7.2, 95% CI = 2.4-21.9; OR for greater than I type = 43.0, 95% CI = 6.9-266.6). Furthermore, increased viral load determined by either method carried an increased risk of disease. HPV infection with viral types previously reported to be related to neoplastic or dysplastic lesions carried the highest risk of SIL. The association of HPV detected by Southern blot and SIL in women less than 35 years old had an OR of 10.1, whereas in women greater than or equal to 35 the OR was 74.5 (p = 0.09 for homogeneity of ORs). We conclude that infection with HPV is the major risk factor for cervical SIL and suggest that targeted HPV screening of women over age 35 may represent an innovative strategy to detect women at high risk of cervical neoplasia.

Identification of human papillomavirus type 16 in primary and recurrent cervical cancer following radiation therapy

Formalin-fixed, paraffin-embedded tissue blocks from 13 women with cervical carcinoma that recurred following radiation therapy were evaluated for the presence of human papillomavirus (HPV) by in situ hybridization using ribonucleic acid 35S-labeled probes for HPV types 6, 11, 16, and 18. Ten of thirteen patients also had pretreatment biopsies from their primary tumors available for analysis. HPV 16 was detected in both primary and recurrent lesions in 4 women. In 1 case, HPV was detected in the primary tumor and not in the recurrence. HPV 16 was also present in three recurrent cancers from which primary lesions were not available for probing. Radiation therapy did not alter the hybridization signal strength or pattern, suggesting that the HPV genome copy number was not significantly affected. The persistence of HPV 16 in recurrent cervical carcinoma is consistent with the theory that HPV plays a role in maintaining the malignant state.

The prevalence of human papillomavirus type 16 and 18 DNA in cervical cancer in different age groups: a study on the incidental cases of cervical cancer in Norway in 1983

In a study carried out to estimate the prevalence of genital Human Papilloma Virus (HPV) infection among cervical cancer patients in Norway, the following values were recorded using the southern blot hybridization method: 54.1% HPV 16, 9.5% HPV 18, 0% HPV 11, and 1.4% HPV 16 and 18 coinfection, yielding a total of 62.2% HPV positive cases in the study. An attempt to include a normal biopsy as "internal control" from each patient failed, as macroscopically normal tissue was often histologically abnormal. HPV infection did not relate to stage of disease, age, or 5-year survival, whereas the classic relationship between stage and survival was observed. A very high percentage of HPV positive cases occurred among older women, a fact which does not support the existence of a new HPV epidemic. The studied population is unique, as it represents 75 cases which comprise a representative sample of the 372 incidental cases of cervical cancer in Norway in 1983. To our knowledge this is the first study of its kind.

Detection of transcripts of human papillomaviruses 16 and 18 in cancer-derived cell lines and cervical biopsies by enzyme immunoassay for DNA-RNA hybrids following solution hybridization

mRNAs of human papillomaviruses (HPV) 16 and 18 were detected in cancer-derived cell lines and genital tract biopsy specimens by a novel hybridization assay. Biotinylated whole genomic HPV DNA probes were hybridized in solution to extracted total nucleic acids. Hybrids between the labeled probes and RNA transcripts were captured on a microplate coated with an antibiotin antibody. Bound hybrids were incubated with a beta-galactosidase-labeled monoclonal antibody to DNA-RNA hybrids and measured by the addition of a fluorogenic substrate. HPV 18 and HPV 16 mRNAs were detected in nucleic acids from 2.3 x 10(3) HeLa cells and 10(4) SiHa cells, respectively. The specificity of the assay for mRNA was demonstrated by the low reactivity of nucleic acids from SiHa cells after treatment with T1 RNase and by the selective reactivity of cellular nucleic acids which bound to an oligo(dT) column. With HPV 16 subgenomic probes, E6-E7 transcripts but not L1-L2 transcripts were detected in SiHa cells. Tests of 58 biopsy specimens from 31 patients showed that the detection of HPV 16 and HPV 18 transcripts in tissue specimens was feasible. Analysis of biopsy specimens with subgenomic probes revealed HPV 16 E6-E7 transcripts in all specimens that reacted with the whole genomic probe, while L1-L2 transcripts were found infrequently.

Nonisotopic human papillomavirus DNA typing of cervical smears obtained at the initial colposcopic examination

To determine the prevalence of human papillomavirus (HPV) infection in 401 patients attending colposcopy for the first time, scraped cervical cells were investigated using dot blot hybridization and biotinylated DNA probes to HPV 6 and 11 (low-risk types) and 16, 18, and 33 (high-risk types). The HPV DNA was isolated from 52% of patients (low-risk types = 4%, high-risk types = 48%). Seventy-five percent had a cervical intraepithelial neoplasia (CIN)-condyloma. Low-risk types were infrequent (7%) and high-risk types (41%) predominant in condyloma/CIN I lesions when converse rates were expected. As CIN I lesions harboring high-risk types are at some risk of progressing to a higher grade dysplasia, colposcopic examination and treatment of this subgroup would seem justified. As expected, high-risk types were statistically associated with increasing grades of dysplasia. This hybridization method identified typeable HPV DNA in 60% of patients with a CIN-condyloma, and highlighted a unique HPV profile for this patient cohort.

Selective suppression of human papilloma virus type 18 mRNA level in HeLa cells by interferon

We have studied the effect of IFN on the transcription of integrated HPV 18 DNA in HeLa cells. We found that the amount of cytoplasmic HPV 18 mRNA was markedly reduced in HeLa cells treated with 10(3) IU/ml of IFN alpha or gamma, and that the inhibitory effect was dose dependent and was detectable by 12h after the addition of IFN. Furthermore, northern blot analysis indicated that IFN remarkably reduced 3.4 kb mRNA species of HPV 18 transcripts in HeLa cells. In contrast, the level of beta-actin mRNA was found to increase in IFN treated cells. The results suggest that IFN alpha and gamma selectively inhibited HPV 18 gene expression at the level of transcription.

Human papillomavirus type 16/18 in uterine cervical adenocarcinoma in situ and adenocarcinoma. A study by in situ hybridization with biotinylated DNA probes

The distribution of human papillomavirus (HPV) DNA type 16/18 in the paraffin sections of 11 adenocarcinomas (AC), 4 adenocarcinomas in situ (AIS), and 2 adenosquamous carcinomas (AC/SCC) of the cervix was examined by in situ hybridization (ISH) with biotinylated DNA probes (B-probes). Four AC, four AIS, and one AC/SCC were positive. These results show that B-probes are an acceptable alternative to both ISH with radiolabeled probes and Southern blot hybridization (SBH), which are difficult to apply in routine pathologic laboratories. Cervical tissues infiltrated with endometrial AC were negative for HPV DNA 16/18, and it is suggested that the presence of HPV DNA 16/18 in uterine AC may be helpful in discriminating cervical AC from endometrial AC.

Purification and DNA-binding properties of human papillomavirus type 16 E6 protein expressed in Escherichia coli

Unfused human papillomavirus type 16 (HPV 16) E6 protein was expressed in Escherichia coli using a lambda PL promoter system. The protein was isolated from the cells as inclusion bodies, extracted by 6 M guanidine-HCl, and purified by chromatography. The purified protein had high affinity to DNA and was demonstrated for the first time to bind to a specific sequence within the long control region of HPV 16.

Trans-regulation and differential cell specificity of human papillomavirus types 16, 18, and 11 cis-acting elements

The noncoding region (ncr) of human papillomavirus (HPV) types 16, 18, and 11 contains promoter and/or enhancer function. We have localized the sequence containing the constitutive enhancers of HPV types 16, 18, and 11 to 315, 230, and 213 bp fragments, respectively, for comparative studies. The region of homology shared between the enhancers of the three viruses is limited to the sequence ATTTTTGGCTT, which is also present in the ncr of HPV 6b and 33. We have also examined the enhancer activity of the HPV ncrs in three human cervical carcinoma cell lines, one noncervical human carcinoma cell line, and one monkey kidney established cell line. We observed cell-specific differences in the constitutive expression of the enhancers in the various cell lines. The conditional enhancer activity of the ncr of the viruses is increased in trans by the E2 gene product of HPV 16. Transactivation by E2 is mediated through the E2 binding motif on HPV enhancer plasmids with a heterologous but not with a homologous promoter. Our preliminary studies also indicate a repressor function for the E7 gene of HPV 16.

Human papillomavirus and epithelial ovarian neoplasia

In contrast to the strong association between human papillomavirus (HPV) and squamous cell carcinoma of the lower female genital tract, no viral DNA had been found in epithelial ovarian carcinoma. Recently, however, R. H. Kaufman, J. Bornstein, A. N. Gordon, E. Adam, A. L. Kaplan, and K. Adler-Storthy [Gynecol. Oncol. 27, 340-349 (1987)] reported the detection of HPV-6 DNA by in situ hybridization in 10 of 12 patients with advanced epithelial ovarian carcinoma. To further investigate the possible association between HPV and epithelial ovarian neoplasia, tumor from 12 patients with epithelial ovarian adenocarcinoma, 3 with epithelial ovarian tumors of low malignant potential, and 3 with epithelial ovarian tumors of low malignant potential, and 3 with epithelial ovarian adenomas was examined for HPV DNA by the Southern hybridization technique. All the tissues were tested under low stringency for HPV-6 and under high stringency for HPV-6, HPV-16, HPV-18, HPV-31, and HPV-35. In addition, all tissues were tested by polymerase chain reaction for the presence of HPV-6 and HPV-11. Of the 12 patients with adenocarcinoma, 5 were poorly differentiated, 4 serous, 1 endometrioid, 1 mucinous, and 1 mixed. The neoplasms were of grades 2-4 with a predominance of stages III and IV (83%). Of the 3 patients with tumors of low malignant potential, all were serous and stage I. Of the 3 patients with adenomas, 1 was mucinous, 1 serous, and 1 Brenner. We were unable to detect HPV-related sequences in any of the specimens. On the basis of these findings, there appears to be no association between HPV and epithelial ovarian neoplasia.

A unique verrucous anogenital tumor associated with type 6b-related human papillomavirus

Multiple dark brown papillomatous tumors, showing some histological features of verrucous carcinoma or giant condyloma, developed mainly in the anogenital region of a Japanese woman. The tumors first appeared when she was 51 years old and annoyed her for over 20 years with several recurrences without any frank malignant transformation, after surgery. Immunohistochemically, papillomavirus genus-specific antigen was demonstrated only in small foci of the lesions resected at first operation. Southern blot analysis revealed human papillomavirus type 6b-related DNA in a surgically resected specimen. The possible role of the human papillomavirus in the genesis of this unique tumor is discussed.

Human papillomavirus infection and anal cancer

To study the association of human papillomavirus (HPV) infection with anal cancer, we examined tissue specimens from 126 patients with malignant lesions of the anal skin or mucosa. The patients were enrolled in a population-based, case-control study of ano-rectal cancer which is being conducted in the state of Washington and the Province of British Columbia. Histologic sections from formalin-fixed, paraffin-embedded tissues were tested for the presence of HPV DNA by in situ hybridization with biotin-labelled HPV 6, 11, 16, 18 and 31 DNA probes. HPV DNA sequences were found in tumor tissues from 24 of the 126 subjects (19.0%). When only squamous neoplasms are considered, 23 of 70 subjects (32.9%) had lesions which contained detectable HPV DNA. One HPV-positive patient had a cloacogenic carcinoma that contained regions of squamous differentiation and it was in these squamous cells that HPV DNA was localized. Of the 23 squamous lesions that harbored detectable HPV DNA, 8 contained HPV 6, 10 contained HPV 16, 1 contained HPV 18 and 4 contained an unclassified virus type(s). HPV DNA was found in tissues from 14 patients with carcinoma-in situ and 10 subjects with invasive carcinoma. These results demonstrate that some malignant tumors of the anus, in both men and women, are associated with HPV infection. We conclude that the anal squamous epithelium is another site where infection with the common genital tract HPVs may carry a risk of malignant transformation.

Human papillomaviruses: are we ready to type?

The issue of determining which human papillomavirus (HPV) is present in a clinical specimen (typing specimens for HPVs) is receiving attention because HPVs cause condyloma acuminata and are associated with the continuum of disease which ranges from dysplasia to invasive genital cancer. Morphological inspection of precancerous lesions is not sufficient to determine which lesions will progress and which will not. A number of research tools based primarily on deoxyribonucleic acid hybridization have been developed. These permit identification and typing of HPV in genital tract scrapings or biopsies. Some HPV types (e.g., HPV-16 and HPV-18) have been identified in high-grade dysplasias and carcinomas more commonly than other types (e.g., HPV-6) and have been designated "high risk" types for cervical cancer. Thus, the question arises whether HPV typing would improve patient management by providing increased sensitivity for detection of patients at risk or by providing a prognostic indicator. In this review, the available typing methods are reviewed from the standpoint of their sensitivity, specificity, and ease of application to large-scale screening programs. Data implicating HPVs in the genesis of genital tract cancers are reviewed, as is the association of specific HPV types with specific outcomes. We conclude that there is currently no simple, inexpensive assay for HPV types, although such assays may be developed in the future. Analysis of the typing data indicates that, while HPV types can be designated high risk and low risk, these designations are not absolute and thus the low-risk group should not be ignored. In addition, interpretation of the data is complicated by finding high-risk types in individuals with no indication of disease. Insufficient data exist to indicate whether knowledge of the presence of a given HPV type is a better prognostic indicator than cytological or histological results. Thus, more research is needed before it can be determined whether typing information will augment the method currently in use for deciding treatment regimen and whether it warrants widespread use.

Occult human papillomavirus infection of the uterine cervix in postmenopausal women

Occult infection is assumed when human papillomavirus is detected in the absence of unequivocal cytologic or histologic changes. In this study occult human papillomavirus infection in postmenopausal women was examined to determine if the histologic findings with such infections were indeed nondiagnostic and to compare the rate of occult human papillomavirus infection in this group with that in a younger age group. In five of 43 cases (12%) sequences homologous to human papillomavirus deoxyribonucleic acid were detected in biopsy specimens from the cervices of hysterectomy specimens of postmenopausal women who had no history of abnormal Papanicolaou smears or genital tract neoplasms. This rate was not significantly different from that found in a premenopausal group of women (8%, n = 60) studied concurrently. Except for one case in which human papillomavirus type 11 was detected, the human papillomavirus types in the occult infections were distinct from those commonly associated with the genital tract. The histologic features of human papillomavirus infection were not found in the human papillomavirus-positive cases, except for one case of cervical intraepithelial neoplasia. The similar rates of occult infection in the two age groups suggests that about 10% of women over a wide range of ages may be infected by human papillomavirus but have no clinical or pathologic evidence of the infection.

Presence of catenated human papillomavirus type 16 episomes in a cervical carcinoma cell line

Human papillomavirus (HPV) is frequently associated with cervical carcinoma and derived cell lines. In primary tissues of the carcinoma, the viral genome may be present in episomal or integrated configuration. In cell lines, however, only integrated HPV sequences have been reported. In this article, we describe the presence of episomal type 16 HPV (HPV16), demonstrated by electron microscopy and two-dimensional agarose gel electrophoresis, in a cervical carcinoma cell line, CC7T/VGH, established in 1980 in Taiwan. In CC7T/VGH, the HPV16 sequences are transcriptionally active, and at least three major HPV16 RNA species were detected in Northern blots. Results from restriction enzyme and S1 nuclease analysis suggest a composition of oligomeric HPV16 molecules in dimeric repeats. In addition, the HPV16 oligomers exist as catenated molecules of interlocking rings instead of concatemers. A monomeric copy of the HPV16 episome was cloned from a Hirt supernatant of CC7T/VGH by using a plasmid vector. Mapping and partial sequencing studies revealed an internal deletion of 163 base pairs within the L1 open reading frame. However, insertion of an A.C nucleotide pair at the deletion junction restored the otherwise frame-shifted L1 open reading frame. Two base transitions were also found within the E7 and the E1 open reading frames. Our findings suggest the need for closer examination for HPV episomal catenation in other cervical carcinoma cell lines as well as in primary carcinoma tissues of the uterine cervix and the anogenital tract. With CC7T/VGH, a way is now available for studies of many important aspects of the biology of HPV such as replication and gene expression of the extrachromosomal viral genome.

Nucleic acid hybridization as a diagnostic tool for the detection of human papillomaviruses

At this time nucleic acid hybridization tests are the most sensitive and reproduceable methods for the detection and differentiation of HPV types in clinical samples. The hybridization method of choice depends on the information desired and the availability of the proper diagnostic nucleic acid probes. Assuming most of the HPV nucleic acid probes become readily available in the near future, then the most sensitive test for screening clinical specimens--albeit the most laborious--will be the Southern blot procedure. As more information covering the involvement of HPV infections with the progression of lesions from benign to malignant is compiled, the need to know the particular subtype or status of HPV integration may become more or less important in the screening of clinical samples. If this information becomes less important, or unnecessary for a simple screening procedure, then dot blot hybridization may prove to be a much easier method for obtaining the information desired. If the sensitivity of in-situ hybridization using non-radioactive probes increases, then this method would become the fastest, easiest, and cleanest technique for the screening of a large number of clinical samples where limited information is desired. The ideal test for the future would be automated. In order to automate a test for HPV infections, the test design must become much simpler, and in order to design a simpler test, more information will be needed concerning the biology of HPV infections, how they cause benign or malignant cellular proliferation, and how the host immune system responds to HPV infections.

Human papillomaviruses and carcinomas

The recognition of multiple types of human papillomaviruses has resulted in remarkable progress in the detection of persisting viral nucleic acid sequences in carcinomas. The consistent transcription in tumors of two early open reading frames, E6 and E7, with few exceptions (Lehn et al., 1985), indicates a role for the products of these genes in the induction and/or maintenance of the transformed state. A number of studies have shown that in vitro transformation can be achieved by transfection of E6/E7 DNA, and proteins encoded by these DNA sequences can be demonstrated in primary human keratinocytes immortalized by this DNA (Kaur et al., 1989). Mutagenesis experiments are needed to determine the absolute requirement for and function of these genes in transformation. A preferential association of some types with benign lesions while others may be frequently found in malignant tumors has been observed. HPV types 5 and 8 in epidermodysplasia verruciformis patients and types 16, 18, 31, 33, etc. in genital lesions are most frequently associated with progression to malignancy, whereas other types, such as HPV-6,-10, -11, and -20, are regularly identified in benign warts. Such distinctions are not absolute but provide the initial steps toward establishing a causal role for some human papillomaviruses in carcinomas. The need for well-designed epidemiological studies in concert with optimum molecular and serologic evaluations is evident (Armstrong et al., 1988). The data from human and animal studies indicate that papillomaviruses contribute significantly to the development of many, if not all, carcinomas, but we do not yet have a clear understanding of the importance of other interacting viral, chemical, or cellular factors. The application of gene cloning and non-stringent hybridization (Law et al., 1979) has provided us with an apparently ever-increasing catalog of human papillomaviruses. More effort is now required to establish their prevalence, the natural history of infection, and the mechanism of neoplastic transformation.

Detection of human papillomavirus deoxyribonucleic acid in the female genital tract

A total of 336 biopsies, scrapes and exfoliated cells from the cervix and from the lower genital tract were screened for human papilloma (HP) viral sequences of types 6, 11, 16 and 18 by Southern blot, dot blot and filter in situ (FISH) hybridizations with cloned 32P-radiolabeled HPV DNA probes. The specimens included cervical intraepithelial neoplasias (CIN I-III), carcinoma in situ and invasive carcinoma of the cervix and vagina, adenocarcinomas, vulvar and vaginal condylomata acuminata and healthy epithelial samples. The oncogenic HPV 16 was found in 46% of the cervical carcinomas. Most of the type 16 occurrences (75%) represented the third stage of inoperable cases. Similarly, HPV 18 was also most frequently present in this stage as well as in carcinoma in situ and in CIN III (25%, 18%). At the same time, in condylomata acuminata, types 6 and 11 were detectable in 88.7% of cares. In all, 13.5% of the normal samples harboured HPV DNA.

Human papillomavirus in dysplasia and carcinoma of the cervix in Singapore

A prospective study was conducted in Singapore in 1985 where 107 women with abnormal cervical smears were studied for cervical neoplasia and its association with the human papillomaviruses (HPV), using HPV 11, 16 and 18 DNA as probes. Cervical biopsies were performed for histology as well as for DNA Southern Blot hybridization studies to detect the presence of HPV 11, 16 or 18 genome. The prevalence of the various types of papillomavirus DNA in cervical tissue samples from cervical carcinoma and dysplasias is presented. HPV types 16 and 18 were found in 5 of 8 (63%) cases of invasive squamous cell carcinoma (SCC), in 12 of 41 (29%) cases of squamous carcinoma-in-situ (CIN 3) and in 3 of 48 (6%) cases of lower grade dysplasia. None of our cases of SCC were associated with unknown HPV types detected using a mixture of HPV 16 or 18 DNA under conditions of low stringency. These unknown HPV types were present in approximately one quarter of our cases of dysplasia of all grades.

Human papillomaviruses and cervical cancer: analysis of histopathologic features associated with different viral types

The histopathologic features of 41 cervical carcinomas were correlated with the presence of human papillomavirus (HPV). Southern blots of DNA extracted from the tumors were hybridized with 32P-labeled type specific probes for HPV 6, 11, 16, 18, and 31. HPV was found in 26/41 (63%) of the tumors. The HPV types were: HPV 16 in 17 tumors (41%), HPV 18 in six tumors (15%) and HPV 31 in two tumors (5%). No tumor hybridized to either HPV 6 or HPV 11. HPV was identified in all histologic subtypes of cervical carcinoma; however, different HPV types were associated with specific histologic features. HPV 18 was identified in four of eight adenocarcinomas, while HPV 16 was found in only one. HPV 16 was most strongly associated with the keratinizing tumors. It was found in 10/13 (77%) of the large cell keratinizing (LCK) and in only 4/16 (25%) of the large cell nonkeratinizing cervical carcinomas (LCNK). A mucoepidermoid with extensive keratinization and pearl formation also contained HPV 16. One of three additional adenosquamous carcinomas had HPV 31, as did one LCNK tumor. In one LCK tumor, a HPV was identified that hybridized to both HPV 16 and 18. The LCNK group contained the highest percentage of tumors in which no papillomavirus DNA was identified (9/16 lacked HPV DNA). No papillomavirus was detected in six tumors from other sites or in five cervical specimens with no histologic evidence of HPV infection. These data indicate that HPV is involved in all major histologic types of cervical carcinoma, and suggest that the different HPV types transform slightly different cell populations, or that transformation by HPV 18 tends to induce adeno-differentiation while HPV 16 leads to squamous maturation.

Sequence duplication and internal deletion in the integrated human papillomavirus type 16 genome cloned from a cervical carcinoma

Integrated human papillomavirus type 16 (HPV16) sequences were cloned from a cervical carcinoma and analyzed by restriction mapping and nucleotide sequencing. The viral integration sites were mapped within the E1 and E2 open reading frames (ORFs). The E4 and E5 ORFs were entirely deleted. An internal deletion of 376 base pairs (bp) was found disrupting the L1 and L2 ORFs. Sequencing analysis showed that an AGATGT/ACATCT inverted repeat marked the deletion junction with two flanking direct repeats 14 and 8 bp in length. A 1,330-bp sequence duplication containing the long control region (LCR) and the E6 and E7 ORFs was also found. The duplication junction was formed by two 24-bp direct repeats with 79% (19 of 24) homology located within the LCR and the E2 ORF of the prototype viral genome, respectively. This observation leads us to propose that the initial viral integration involved an HPV16 dimer in which the direct repeats in tandem units recombined, resulting in reiteration of only a portion of the original duplication. A guanosine insertion between nucleotides 1137 and 1138 created a continuous E1 ORF which was previously shown to be disrupted. Results from this study indicate that sequence reiteration and internal deletion in the integrated, and possibly in the episomal, HPV16 genome are influenced by specific nucleotide sequences in the viral genome. Moreover, reiteration of the LCR/E6/E7 sequences further supports the hypothesis that the E6/E7 ORFs may code for oncogenic proteins and that regulatory signals in the LCR may play a role in cellular transformation.

Papillomaviruses: the current status in relation to oral disease

Human papillomaviruses of different types are associated with a variety of benign oral lesions and may be associated with some premalignant and malignant oral lesions. However, since it is now clear that a variant of human papillomavirus 16 is harbored by normal oral mucosa, as well as by premalignant and malignant lesions, such associations may not necessarily always be causal. The rapid progress of recent research in this field is reviewed, with particular reference to oral disease, and the current status is discussed.

Nucleotide sequences of cDNAs for human papillomavirus type 18 transcripts in HeLa cells

HeLa cells expressed 3.4- and 1.6-kilobase (kb) transcripts of the integrated human papillomavirus (HPV) type 18 genome. Two types of cDNA clones representing each size of HPV type 18 transcript were isolated. Sequence analysis of these two types of cDNA clones revealed that the 3.4-kb transcript contained E6, E7, the 5' portion of E1, and human sequence and that the 1.6-kb transcript contained spliced and frameshifted E6 (E6*), E7, and human sequence. There was a common human sequence containing a poly(A) addition signal in the 3' end portions of both transcripts, indicating that they were transcribed from the HPV genome at the same integration site with different splicing. Furthermore, the 1.6-kb transcript contained both of the two viral TATA boxes upstream of E6, strongly indicating that a cellular promoter was used for its transcription.

Sensitivity of in situ hybridization techniques using biotin- and 35S-labeled human papillomavirus (HPV) DNA probes

In order to evaluate the sensitivity of our modified in situ DNA hybridization technique using biotinylated probes, formalin fixed, paraffin embedded biopsies from 20 cervical lesions known to contain human papillomavirus (HPV) DNA were re-examined by the technique using both 35S-labeled- and biotinylated HPV DNA probes. The probe concentrations as well as the detection limits of biotin probing were screened by spotting known amounts of HPV 16 DNA on nylon filter, and allowed to hybridize with biotinylated HPV 16 DNA probe. By this method, 4 pg of HPV 16 DNA could be detected using a probe concentration of 0.2 micrograms/ml. HPV DNA could be demonstrated in all 20 biopsies with both hybridization techniques. However, signals in subrabasal cells were detected more frequently with biotin- than with 35S-labeled probes. Additional experiments were performed using three cervical cancer cell lines (with known copy numbers of HPV DNA), to assess the detection limits of HPV infections by the in situ hybridization techniques. The CaSki cells (500-600 HPV 16 copies/cell) were unequivocally positive with both labelling systems. HeLa cells (10-50 HPV 18 copies/cell) were positive with the biotin probing in 10/10 smears, as compared to 7/10 smears when 35S-labeled probes were used. Radioactive probing was inferior to biotinylated probing in detecting the signals in SiHa cells (1-2 HPV 16 copies/cell). This is because even weak background signals could mask true positive signals when 35S-labeled probes are used. In contrast, no background is generated with the biotinylated probes, detected with streptavidin-biotinylated alkaline phosphatase complex. In situ hybridization with biotinylated DNA probes is as sensitive as techniques using 35S-labeled probes for detecting HPV infections in routine cervical biopsies or smears.

Transcriptional differences of the human papillomavirus type 16 genome between precancerous lesions and invasive carcinomas

Human papillomavirus type 16 (HPV16) genome DNA and its transcripts in biopsied cervical neoplasias were analyzed by simultaneous extraction of DNA and RNA from one biopsied sample. Southern blot analysis revealed that 5 of 20 cervical intraepithelial neoplasias (CINs) contained HPV16 DNAs existing primarily as episomes and two of seven invasive carcinomas harbored HPV16 genome sequences integrated into the host DNA. Northern (RNA) blot analysis showed that the HPV16 genome sequences were transcriptionally active in the five CINs, as well as in the two invasive carcinomas. The pattern of HPV16-specific transcripts in the CINs was uniform, and the major transcripts were 4.2, 2.2, 1.6, and 1.4 kilobases in size. However, the pattern of HPV16-specific transcripts in the invasive carcinomas was variable and different from that in CINs, suggesting that the alteration of transcriptional pattern might play a key role in the development of malignancy.

Progression of the phenotype of transformed cells after growth stimulation of cells by a human papillomavirus type 16 gene function

Alteration of the growth properties of the established murine fibroblast cell lines NIH 3T3 and 3Y1 was studied in monolayer cultures and in cells suspended in semisolid medium after introduction of a cloned human papillomavirus type 16 (HPV16) DNA. HPV 16 DNA stimulated both cell lines to grow beyond their saturation densities in monolayer cultures without any apparent morphological changes or tendency to pile up. These cells were also stimulated to grow in soft agar. Since essentially all the cells that received the viral gene were stimulated to grow, the growth-stimulatory activity of HPV16 appeared to be due to the direct effect of a viral gene function. The NIH 3T3 cells showed an additional change in growth properties upon prolonged incubation of dense monolayers of cells containing the HPV16 DNA; morphologically recognizable dense foci appeared at a frequency of about 10(-3). These cells, when cloned from the foci, grew more rapidly in soft agar than the parental cells and were morphologically transformed. In other words, there were two sequential steps in cell transformation induced by HPV16. Practically all the viral DNAs were present in the cells as large rearranged multimers and were integrated into host chromosomal DNA. There was no obvious difference in the state of viral DNA in the cells of the original clone or the three subclones derived from it as dense foci. There was no difference in the amount or the number of viral RNA species expressed in the cells at these two stages. The secondary changes in the growth properties of NIH 3T3 cells appear to be due to some cellular alterations.