Papillomavirus infection of the cervix. III: Relationship of the presence of viral structural proteins to the expression of involucrin

Characterization of human papillomavirus type 16 activity in separate biopsies from a carcinoma of the cervix uteri

Human papillomavirus (HPV) 16-specific nucleic acid sequences were analysed in separate biopsies taken from a patient with a poorly differentiated squamous cell carcinoma of the uterine cervix. Biopsies were obtained from histopathologically normal epithelium adjacent to the carcinomatous epithelium, the primary carcinoma and a metastatic lymph node. Signals characterizing viral DNA and oncogene transcription were obviously differentiation dependent as shown by in situ hybridization of viral nucleic acids and immunofluorescence of epithelial differentiation specific proteins. In histologically normal parts of the epithelium viral DNA was amplified at the transition from basal to maturing cells, whereas E6/E7 genes were actively transcribed mainly in maturing epithelial cells following the basal cell layer. Some of the cells in the primary carcinoma and in the metastatic lymph node expressed involucrin at increased levels. Signals for viral DNA and HPV 16-specific E6/E7 transcripts decreased in intensity during differentiation in an inverse relationship to the observed involucrin increase in those cells. The absence of Ki67 in cells expressing large amounts of involucrin as revealed by immunostaining, support the inverse correlation between differentiation of cancer cells, HPV 16 replication and E6/E7 transcription. The changes in cytokine expression may indicate an HPV 16 associated disruption of normal cytokine expression pattern in the carcinoma.

Characterisation of eight monoclonal antibodies to involucrin

Involucrin is a precursor of the insoluble protein envelope that is assembled in the outermost layers of the epidermis. The coding sequence of the protein contains a number of short tandem repeats that have been greatly altered during mammalian evolution. We have characterised eight mouse monoclonal antibodies raised against human involucrin, all of which bind to the protein in immunoprecipitation, immunoblot and immunohistochemical preparations. Each antibody was screened for cross-reactivity with gorilla, owl monkey, dog and pig involucrin and with a fragment of the human protein, expressed in lambda gt 11, that includes the entire early region of the modern segment of repeats. Three antibodies recognised involucrin in all of these assays. Four antibodies recognised primate involucrins and the lambda gt 11 fragment. One antibody, which showed cross-reactivity with lower molecular weight proteins, only recognised primate involucrins and therefore bound outside the early region of the modern segment. Since the antibodies can be used to detect involucrin both biochemically and histologically, in a range of species, they will have applications in further studies of the expression, function and evolution of the protein.

Transforming growth factors beta 1 and 2 transcriptionally regulate human papillomavirus (HPV) type 16 early gene expression in HPV-immortalized human genital epithelial cells

Human papillomavirus type 16 (HPV16) early proteins E6 and E7 have been implicated in maintenance of the malignant phenotype in cervical cancer. Transforming growth factors beta one and two (TGF betas 1 and 2), polypeptides that regulate cellular growth and differentiation, reversibly inhibited expression of the HPV16 E6 and E7 genes in several immortal genital epithelial cell lines. Loss of E6 and E7 protein expression followed a dramatic time- and dose-dependent decrease in E6 and E7 RNA levels and was accompanied by cessation of cell proliferation. TGF betas 1 and 2 inhibited HPV16 RNA expression at the transcriptional level; inhibition was dependent upon ongoing protein synthesis. TGF betas 1 and 2 also induced a six- to sevenfold increase in TGF beta 1 RNA. Cells became partially resistant to the inhibitory effects of TGF beta 1 on cell growth and HPV early gene expression after prolonged cultivation in vitro or after malignant transformation. Thus, TGF beta 1 may function as an autocrine regulator of HPV gene expression in infected genital epithelial cells.

Distribution of involucrin in normal and pathological human uterine cervix

A study was undertaken to determine the potential value of involucrin immunostaining, a protein synthesized by mature squamous epithelial cells, in distinguishing benign from neoplastic lesions in cervical pathology. A total of 146 cervical biopsies were analyzed using an indirect immunoperoxidase method and polyclonal antibody. A suprabasal homogeneous cytoplasmic staining pattern was consistently observed in normal squamous cervical epithelium. In contrast, 43.7% of cervical condylomas showed involucrin at all levels of the epithelium including the basal layer. Variable patterns were seen in cervical intraepithelial neoplasia (CIN), with 46% of full-thickness stainings, although no significant difference was obtained among the different grades of CIN lesions. Distribution of involucrin was correlated (P less than 0.05) with the degree of tumor differentiation in squamous cell carcinomas, being absent in 71.4% of poorly differentiated carcinomas and focally present in 75% of well-differentiated carcinoma. Lesions of endocervical origin, either benign or malignant, were entirely negative for involucrin. It is concluded that involucrin seems unable to establish a reliable differential diagnosis between benign and neoplastic conditions in cervical pathology, and should therefore be considered only a specific marker of squamous differentiation in both normal and pathological human uterine cervix.

Distribution of epithelial antigens in the human uterine cervix: a review

Epithelial antigen immunostaining in the uterine cervix has been claimed to be helpful in the identification and classification of rare lesions, evaluation of basement membrane integrity, study of atypical condylomas, immunodetection of proliferating processes and early diagnosis of malignant transformation. The present review attempts to demonstrate the potential value of immunohistological techniques as a means of identifying normal and abnormal patterns of antigenic expression in cervical epithelium.

Morphologic and immunohistochemical evidence of human papillomavirus capsid antigen in smokeless tobacco keratoses from juveniles and adults

Seventy-seven tissue samples from patients with either degree I, II, or III smokeless tobacco keratoses were examined. The tissues were evaluated for the presence of human papillomavirus (HPV) antigen by immunocytochemical staining. Capsid antigen could be identified in sixteen cases (20.78%). This investigation further supports the concept that smokeless tobacco-associated leukoplakias can be correlated with HPV infection.

Altered expression of filaggrin in human papillomavirus (HPV) lesions of the uterine cervix

A series of 64 punch biopsies collected from women prospectively followed-up for cervical Human papillomavirus (HPV) infections (with and without CIN), and 38 control biopsies (normal epithelia, and classical CIN) were analysed for expression of filaggrin (a histidine-rich protein constituent of keratohyalin granules) using the ABC technique and polyclonal antibody. HPV typing was completed using the in situ hybridization technique with DNA probes for HPV 6, 11, 16, 18 and 31. Three patterns of filaggrin distribution were differentiated: pattern I, all layers above the basal cells stained positive regularly; pattern II, all layers above the basal cells stained irregularly, and pattern III, scattered superficial cells stained positive. There was a significant difference between HPV-noCIN and HPV-CIN lesions in their filaggrin patterns, pattern I being present in the majority (77.7%) of HPV-noCIN lesions, as contrasted to HPV-CIN lesions, where pattern III was the predominant one (43.5%), followed by pattern II (32.6%). In HPV-CIN as well as in CIN lesions, pattern I was inversely related to the grade of CIN, being entirely absent in HPV-CIN III and CIN III. A significant difference exists between CIN and HPV-CIN lesions, concerning the presence of pattern III (4.3% and 43.5%, respectively, P less than 0.001). The difference was less dramatic with regard to pattern I (30.4% and 21.7%, respectively, P less than 0.05). In the lesions containing HPV 6, 11 or 31 DNA, filaggrin distribution was shown to be more close to that of the normal epithelium (I 36.7%, and II 34.7%), while in the HPV 16 and 18-infected cases, pattern III was the predominant one (46.7%). The assessment of filaggrin pattern in HPV lesions might be of help in evaluating the severity of the disturbance of keratinocyte differentiation induced by the progression of HPV infections.

Expression of human papillomavirus types 6b and 16 L1 open reading frames in Escherichia coli: detection of a 56,000-dalton polypeptide containing genus-specific (common) antigens

The human papillomavirus (HPV) genome contains two large open reading frames (ORFs), designated L1 and L2. To characterize the antigenic properties of the L1 ORF-encoded proteins, we cloned the L1 ORFs of HPV6b and HPV16 in plasmids, and these were expressed in Escherichia coli. First, the HPV6b DNA, representing 85.2% of the L1 ORF, was cloned in pUC19 and expressed in E. coli JM83 and RB791 as a 160,000-molecular-weight (160K) fusion protein with E. coli beta-galactosidase (6bL1/beta-gal). Second, the HPV16 DNA, representing 89.8% of the L1 ORF, was cloned in pKK233-2 and expressed as a 56K protein (16L1) in strain RB791. Both the 6bL1/beta-gal and 16L1 proteins cross-reacted with anti-bovine papillomavirus type 1 (BPV1) antibody raised against disrupted BPV1 particles. An antibody raised against the 6bL1/beta-gal fusion protein reacted with the 16L1 protein and also with native papillomavirus antigens in human genital condyloma and bovine fibropapilloma tissues, as determined by biotin-streptavidin staining. Furthermore, the anti-6bL1/beta-gal antibody recognized a 54K protein which seemed to be a major capsid protein of BPV1 and also a 56K protein of biopsies harboring HPV6 or HPV11. From these results we concluded that the papillomavirus L1 gene product contains genus-specific (common) antigens and that the HPV6 and HPV11 L1 genes specify the 56K capsid protein.

Involucrin expression in cervical intraepithelial neoplasia: a critical evaluation

Involucrin is a keratinocyte envelope protein precursor which is synthesized at an early stage of differentiation in normal squamous epithelium. Recent studies suggest that this protein may be a marker for neoplastic epithelium. To address this issue, we analyzed involucrin expression in 105 biopsies containing 119 areas of normal, condylomatous, and neoplastic epithelium. Overall, 88, 75, and 55% of condylomata, well-differentiated CIN, and poorly differentiated CIN (carcinoma in situ) contained positive staining for involucrin. Excluding lesions with severe inflammation, 100, 88, and 55% of these lesions, respectively, were positive. Staining patterns in neoplastic lesions differed from those in the normal epithelium and condylomata; the staining in CIN tended to be focal, and intensity of staining varied widely from cell to cell in all layers of the epithelium. In high grade CIN, staining correlated with increases in cell size and cytoplasmic differentiation. These studies suggest that involucrin will not differentiate between lesions of low versus high risk for progressing to invasive carcinoma. However, the patterns of involucrin expression confirm the marked differences in patterns of cellular differentiation between classical condylomata and CIN.

The role of human papillomaviruses in the pathogenesis and histologic classification of precancerous lesions of the cervix

It is clear that the relation between HPV infection and cervical neoplasia is more complex than initially realized. Preliminary molecular virologic data suggest preferential distributions of low- and high-risk HPV types in CIN that tend to correlate with the morphologic appearance. Thus, mild and moderate dysplasias (CIN I and II) contain a diverse distribution of HPV types, including a minority that have a high risk of malignant potential. HPV, therefore, appears to play a major role as a promoter. Neoplastic transformation is probably determined by specific HPV types but, in addition, requires initiation by some other carcinogenic stimulus, e.g., HSV II, cigarette smoking. Despite numerous studies, performed during the past 30 years, the long-term behavior of dysplasia remains uncertain. The natural history of HPV-associated lesions is unknown. Until this information is available, it is recommended that the conventional dysplasia--CIS or CIN nomenclature be used. The presence of associated viral changes can be considered and added to the diagnosis, e.g., "moderate dysplasia (CIN II) with evidence of papillomavirus infection." Treatment should be the same for all intraepithelial lesions, regardless of the presence of morphologic evidence of HPV. In the future, it may be necessary to modify the classification of precancerous lesions of the cervix if it is shown that a specific HPV type induces a characteristic morphologic alteration or that the HPV type, in and of itself, has greater prognostic significance. Until then, confusion will be minimized and management optimized if the conventional dysplasia--CIS or CIN nomenclature is employed.

Papillomavirus infection and squamous neoplasia of the cervix

In the past, the lack of a tissue culture system or an animal model suitable for inducing HPV lesions precluded the study of the role of PV in human disease. The development of a genus-specific cross reacting PV antiserum and molecular hybridization techniques now enables pathologists and molecular virologists to assay tissues for the presence of PV structural antigens and DNA sequences using highly specific and sensitive PV probes. The data that has been generated with these new research tools has far reaching implications. For example, the multifocality of squamous carcinoma of the vulva, vagina and cervix together with their similar histology, epidemiology and relationship to precursor lesions suggests that all of these neoplasms as well as related tumors in males may be caused by HPV. Since the immunoperoxidase technique using the PV antiserum can be performed on formalin-fixed paraffin-embedded tissue, systematic evaluation of these lesions can be done retrospectively. After identifying PV-associated lesions by the immunocytochemical method, prospective studies can be undertaken utilizing molecular hybridization in an effort to detect PV-DNA sequences and thereby to more clearly define the role of HPV in squamous neoplasia of the female genital tract.