The role of viruses in human tumors

[The clinical aspects of HPV-positive cancer of the oral cavity and oropharynx]

This review was designed to focus on the prevalence and the magnitude of infection with human papilloma virus (HPV) among healthy subjects and patients presenting with cancer of the oral cavity and oropharynx. We compare the data on the relative frequency of HPV-positive and HPV-negative cancer of the oral cavity and oropharynx in different populations, peculiarities of the clinical course of this pathology, and methods of its treatment. Much emphasis is placed on the specific clinical and morphological features of HPV-positive cancer of the oral cavity and oropharynx. The general and relapse-free survival rates are considered with special reference to the outcome and prognosis of this disease. The currently accepted approaches to the treatment of HPV-positive cancer of the oral cavity and oropharynx are discussed. It is concluded that HPV-positive cancer of the oral cavity and oropharynx should be regarded as an autonomous pathological condition requiring specific approaches to its management, such as the application of adequate treatment schemes and algorithms.

HPV type 16 in conjunctival and junctional papilloma, dysplasia, and squamous cell carcinoma

AIMS

To clarify the role of human papillomavirus (HPV) infection in the development of papilloma, dysplasia, squamous cell carcinoma, and basal cell epithelioma arising from the eyelids, including the tunica conjunctiva palpebrum (conjunctiva), its junction to epidemis of eyelid skin (junction), and eyelid skin.

METHODS

Sixteen cases of papilloma, four of dysplasia, four of squamous cell carcinoma, and 12 of basal cell epithelioma were examined using formalin fixed and paraffin embedded samples. Detection of HPV-DNA was performed by PCR-RFLP and in situ hybridisation (ISH) methods.

RESULTS

HPV-16 was detected in 12/16 papillomas (75%), 2/4 dysplasias (50%), and 1/4 squamous cell carcinomas (25%) but in none of the basal cell epitheliomas. No other HPV subtypes were found. ISH assay showed positive signals in only two cases of dysplasia and squamous cell carcinoma. The mean age of HPV-16 positive dysplasia and squamous cell carcinoma cases (81.7 years) was significantly higher than that of HPV-16 positive papilloma cases (p < 0.01).

CONCLUSIONS

Based on the presence of HPV-16 in both benign and malignant lesions and the age distribution, it seems likely that HPV-16 alone may be incapable of causing development of conjunctival and junctional dysplasia and squamous cell carcinoma, and that any correlation between the papilloma-squamous cell carcinoma sequence and HPV infection may be due to rare events.

Detection of Epstein-Barr virus and human papillomavirus in head and neck tumors

The presence of Epstein-Barr virus (EBV) DNA and human papillomavirus (HPV) DNA in 74 head and neck tumor tissues was examined by the polymerase chain reaction and DNA sequencing analysis. EBV DNA sequence was detected in all 30 nasopharyngeal-carcinoma tissue samples and in 30 of 44 other head and neck tumor samples. HPV DNA sequence was detected in 14 of 30 nasopharyngeal-carcinoma tissue samples and in 11 of 44 other tumor samples. Coinfection of both viruses was observed in 14 nasopharyngeal-carcinoma tissue samples but only in 5 other head and neck tumor samples including 3 hypopharyngeal-carcinoma tissue samples. Our data indicate that EBV is closely associated with nasopharyngeal- carcinoma and may also be related to hypopharyngeal-carcinoma. In addition, a relatively high percentage of EBV-positive nasopharyngeal- and hypopharyngeal-carcinoma tissue specimens contained HPV sequence. The significance of the coexistence of EBV and HPV in these tumor tissues requires further study.

Infectious agents in the etiology of esophageal cancer

Extensive epidemiological and experimental studies have suggested that some chemical agents, nutritional deficiencies, and physical factors are associated with the development of esophageal cancer (EC). Recent evidence also suggests an etiologic role of certain microorganisms in esophageal carcinogenesis either by producing carcinogens or promotors or by acting directly on the host cells. The mutagenic and carcinogenic effects of several fungi and bacteria isolated from the grains and foodstuffs in high-risk areas have been shown by in vitro and in vivo studies. Certain viruses, e.g., human papillomavirus, herpes simplex virus, cytomegalovirus, and Epstein-Barr virus, have been implicated in the pathogenesis of a variety of human cancers, and all of them are known to produce tumors in animals and cell transformation in vitro. These viruses also have been shown to infect the esophageal epithelium. Therefore, although many of the key issues of their mechanisms of action are unclear as yet, they should be considered potential etiologic agents of EC. The present review summarizes the data available on the etiology of EC, emphasizing the current evidence implicating an etiologic role of microorganisms in the pathogenesis of this malignancy.

Human papillomavirus involvement in esophageal precancerous lesions and squamous cell carcinomas as evidenced by microscopy and different DNA techniques

A series of 71 surgically resected esophageal squamous cell carcinomas, including 51 cases of formalin-fixed samples and 20 cases of fresh biopsy specimens derived from the high-incidence area of esophageal cancer in China, were systematically analyzed for the presence of human papillomavirus (HPV) infections by light microscopy, electron microscopy (TEM), in situ DNA hybridization, Southern blot hybridization, and polymerase chain reaction (PCR) techniques. On light microscopy, HPV-suggestive lesions were found in a total of 49.0% (25 of 51) of the specimens, including the flat type (22 of 51) and, less frequently, an inverted one (2 of 51). Of the 51 formalin-fixed, paraffin-embedded specimens, 43.1% (22 of 51) contained HPV DNA sequences by in situ hybridization. Of the positive cases, HPV 6 was present in three (5.9%), HPV 11 in three (5.9%), HPV 16 in eight (15.7%), HPV 18 in six (11.8%), double infections with HPV 11/18 in one (2.0%), and HPV 16/18 in one. In most cases the HPV-positive signals were localized in the hyperplastic and/or dysplastic epithelium adjacent to invasive carcinomas. In two specimens, however, HPV DNA sequences were found in the frankly invasive lesions, one being HPV 6 and the other HPV 18. On TEM, HPV-like particles located in the nuclei of koilocytotic cells were demonstrated in two of the five specimens previously shown to be HPV-positive by in situ hybridization. By means of the PCR technique, all specimens positive for HPV by in situ hybridization also contained amplified HPV sequences. Moreover, three additional samples negative by in situ hybridization were found to contain HPV 11 DNA sequences. Of the 20 DNA samples extracted from the fresh carcinoma samples (containing some surrounding tissues as well) 9 were shown to contain HPV DNA sequences by Southern blot hybridization under low-stringency conditions. Of these, eight samples remained positive when hybridized with the probe cocktail of HPV 11, 16, 18, and 30 DNA under high-stringency conditions. HPV DNA sequences in these carcinoma specimens appeared to be present mainly in an integrated form. The present results confirm the HPV involvement in esophageal squamous cell lesions and suggest that HPV infection might be an important etiologic factor in the pathogenesis of esophageal cancer, most probably acting synergistically with other carcinogenic factors.

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.

Viruses and chronic disorders involving the human oral mucosa

Viruses have been implicated in the etiology of several chronic disorders of the oral mucosa. Most of these associations have been with DNA viruses, particularly certain herpesviruses, which are associated, for example, with some cases of erythema multiforme and with hairy leukoplakia. Papillomaviruses are associated with various papillomatous lesions, focal epithelial hyperplasia, and possibly with some carcinomas. Viruses may possibly be associated with recurrent aphthae, Behçet's syndrome, and some dermatoses. The literature concerning these possible associations is reviewed. However, much more research needs to be done before the full story of viral associations with oral mucosal disorders can be written.

Viruses and oral cancer

Oral cancer is a disease with a complex etiology. There is evidence for important roles of smoking, drinking, and genetic susceptibility, as well as strong indications that DNA viruses could be involved. The herpes simplex virus type 1 has been associated with oral cancer by serological studies, and animal models and in vitro systems have demonstrated that it is capable of inducing oral cancer. Papillomaviruses are found in many oral cancers and are also capable of transforming cells to a malignant phenotype. However, both virus groups depend on co-factors for their carcinogenic effects. Future research on viruses and oral cancer is expected to clarify the role of these viruses, and this will lead to improvements in diagnosis and treatment of the disease.

Peripheral blood lymphocyte subpopulations in Indian women with cervical intraepithelial neoplasia and invasive cancer--an immunocytochemical study using monoclonal antibodies

The peripheral blood lymphocyte subpopulations in Indian women with various grades of cervical intraepithelial neoplasia [33], invasive cancer [22] and matched controls [30] were studied using specific monoclonal antibodies and biotin avidin immunofluorescence technique. Our results showed a significant fall in peripheral T (CD2) B(CD22) cells in patients with CIN III and invasive cervical cancer lesions compared to controls (P less than 0.001). Similarly the quantum of T helper cells (CD4) decreased according to the severity of cervical lesions (P less than 0.01 - P less than 0.001), whereas the T suppressor cells (CD8) depicted an increasing trend in patients with higher grade of cervical lesions (CIN III and invasive cancer, P less than 0.001) as compared to controls. Further, the CD4/CD8 ratio showed a significant downfall with the severity of cervical lesions (P less than 0.01 - P less than 0.001), indicating a perturbance in the homeostasis of host cellular immunity.

Inhibition of N-methyl-N'-nitro-N-nitrosoguanidine-induced methotrexate and adriamycin resistance in CHO cells by adeno-associated virus type 2

We studied the effects of helper-dependent parvovirus AAV [adeno-associated virus] type 2 on carcinogen-inducible resistance to methotrexate (MTX) and adriamycin (ADR) in Chinese hamster ovary cells. Both types of drug resistance were monitored by determination of the number of drug-resistant colonies normalized for the respective value of plating efficiency under non-selective conditions. Treatment of cells with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) drastically enhanced the frequency of resistance to MTX and ADR. By contrast, infection of cells with AAV-2 prior to treatment with MNNG markedly inhibited carcinogen-induced drug resistance. Infection by AAV alone did not exert any effect. Analysis of the dihydrofolate reductase (dhfr) gene copy numbers of individual MTX-resistant clones derived from MNNG-treated and non-treated cultures revealed similar frequencies (60-80%) and amplitudes of dhfr gene amplification (2- to 8-fold) irrespective of prior AAV treatment. Hence, carcinogen-induced enhancement of MTX-resistance could reflect an increase in the frequency of dhfr gene amplification among the survivors of MNNG treatment. On the other hand, inhibition of carcinogen-inducible drug resistance by AAV suggests an interference of the virus with cellular responses to genotoxic stress, thus leading to enhanced cell killing under altered growth conditions. Possible mechanisms responsible for the inhibitory effect of AAV and its relevance in relation to tumor chemotherapy are discussed.

A subset of herpes simplex virus replication genes induces DNA amplification within the host cell genome

Herpes simplex virus (HSV) induces DNA amplification of target genes within the host cell chromosome. To characterize the HSV genes that mediate the amplification effect, combinations of cloned DNA fragments covering the entire HSV genome were transiently transfected into simian virus 40 (SV40)-transformed hamster cells. This led to amplification of the integrated SV40 DNA sequences to a degree comparable to that observed after transfection of intact virion DNA. Transfection of combinations of subclones and of human cytomegalovirus immediate-early promoter-driven expression constructs for individual open reading frames led to the identification of six HSV genes which together were necessary and sufficient for the induction of DNA amplification: UL30 (DNA polymerase), UL29 (major DNA-binding protein), UL5, UL8, UL42, and UL52. All of these genes encode proteins necessary for HSV DNA replication. However, an additional gene coding for an HSV origin-binding protein (UL9) was required for origin-dependent HSV DNA replication but was dispensible for SV40 DNA amplification. Our results show that a subset of HSV replication genes is sufficient for the induction of DNA amplification. This opens the possibility that HSV expresses functions sufficient for DNA amplification but separate from those responsible for lytic viral growth. HSV infection may thereby induce DNA amplification within the host cell genome without killing the host by lytic viral growth. This may lead to persistence of a cell with a new genetic phenotype, which would have implications for the pathogenicity of the virus in vivo.

Risk factors in the development of cervical intraepithelial neoplasia in women with vulval warts

Of 59 women referred with vulval warts whose cervices were assessed colposcopically for the presence of cervical intraepithelial neoplasia (CIN) before local treatment of the wart lesions, 17 had histologically proved CIN, 12 had histologically proved cervical wart virus infection, and 30 had abnormality on colposcopy or cytology. Seven of the 17 with CIN had no abnormality on cervical cytology. No differences in sexual behaviour, smoking habit, or oral contraceptive use were seen between women with CIN and those with no cervical abnormality. Viral DNA typing of the vulval lesions was carried out, but there were no differences in the distribution of viral types between the three different histological groups. Of the 30 women with no abnormality at the initial visit, 23 were followed up colposcopically and cytologically for one to two years. Three of them developed CIN after adequate treatment of the vulval lesions despite the absence of cervical abnormalities on colposcopy at the time of treatment. Studying the known factors linked with CIN failed to show why some women with vulval warts develop CIN, even after treatment of the warts, and others do not. The large number of false negative results on cervical cytology in our patients suggests that women presenting with vulval warts should be screened colposcopically in the first instance. Close follow up of women whose warts are treated and who are thought to have no cervical abnormality at that assessment is essential.

Mechanisms of carcinogenesis with particular reference to the oral mucosa

Three types of stimulus, chemical, physical and viral, are known to be carcinogenic to susceptible animals. This review considers these stimuli and their possible mechanisms in general terms and their possible relevance to the induction of oral mucosal carcinoma in particular.

Chromosomal insertion of human papillomavirus 18 sequences in HeLa cells detected by nonisotopic in situ hybridization and reflection contrast microscopy

Genomic insertion of human papillomavirus (HPV) sequences is associated with the genesis of cervical carcinoma, and HPV-induced incipient cellular alterations may also present a requisite for the establishment of cell lines such as HeLa. Considering the theoretical importance of specific viral integration sites, we attempted to detect in HeLa cells the chromosomal location of DNA sequences homologous to HPV-16 and HPV-18 sequences by a nonisotopic high resolution in situ hybridization technique. Chromosome identification following in situ hybridization was possible by counterstaining of the same preparation with Chromomycin A3, Distamycin A, and DAPI. Using this approach, we have assigned HPV-18 integration in HeLa cells to band 8q24 (a site including the locus of the myc-protooncogene), to an abnormal chromosome 22, and to a not yet identified marker chromosome possibly neighboring other oncogenic or activating sites. The sensitive detection technique described in this study presents a new approach involving in situ chromosome hybridization with biotinylated DNA probes in combination with reflection contrast microscopy and subsequent fluorescent R- and C-banding. The method allowed the assignment of a 7-kb HPV-18 DNA probe to human chromosomal sites important in growth regulation and cancerogenesis. It should prove useful in a number of similar studies using other viral and oncogenic DNA probes.

Hepatocellular carcinoma and hepatitis B virus infection: molecular evidence for monoclonal origin and expansion of malignantly transformed hepatocytes

The clonality of tumor cells was studied in a patient with metastasizing hepatocellular carcinoma (HCC). Using hepatitis B virus (HBV) DNA as a genetic marker, the pattern of integration of viral DNA into the tumor cell genome was determined by Southern blot analyses of DNAs extracted from different HCC lesions in the liver and both lungs. All tumor tissues examined were found to have viral DNA integrated into the same site(s) of the cellular genome. This finding provides direct molecular evidence for a monoclonal origin and expansion of malignantly transformed hepatocytes during tumor growth and metastasis. This characteristic is similar to other human cancers associated with viral infections, such as adult T-cell leukemia, Burkitt's lymphoma, or cervical cancer, and is important for our understanding of viral oncogenesis in man.

Herpes simplex virus type 2 mutagenesis: characterization of mutants induced at the hprt locus of nonpermissive XC cells

In a previous report, herpes simplex virus type 2 (HSV-2) was shown to increase the frequency of mutation at the hypoxanthine phosphoribosyltransferase (hprt) locus of nonpermissive rat XC cells (L. Pilon, A. Royal, and Y. Langelier, J. Gen. Virol. 66:259-265, 1985). A series of 17 independent mutants were isolated after viral infection together with 12 spontaneous noninfected mutants to characterize the nature of the mutations induced by the virus at the molecular level. The DNA of the mutants isolated after viral infection was probed with cloned HSV-2 fragments representing the entire genome. In these mutants, no authentic HSV-2 hybridization could be detected. This was indicative of a mechanism of mutagenesis which did not require the permanent integration of viral sequences in the host genome. The structure of the hprt gene was determined by the method of Southern (J. Mol. Biol. 98:503-517, 1975), and the level of hprt mRNA was analyzed by Northern blots. Except for the identification of one deletion mutant in each of the two groups, the HPRT- clones showed no evidence of alteration in their hprt gene. A total of 7 of 12 spontaneous mutants and 11 of 15 mutants isolated from the infected population transcribed an hprt mRNA of the same size and abundance as did the wild-type cells. Thus, the majority of the mutants seemed to have a point mutation in their hprt structural gene. Interestingly, the proportion of the different types of mutations was similar in the two groups of mutants. This analysis revealed that HSV-2 infection did not increase the frequency of rearrangements but rather that it probably induced a general increase of the level of mutations in the cells. This type of response is thought to be compatible with the biology of the virus, and the possible mechanisms by which HSV-2 induces somatic mutations in mammalian cells are discussed.

Intracellular surveillance of persisting viral infections. Human genital cancer results from deficient cellular control of papillomavirus gene expression

A model is proposed to explain basic features of viral oncogenesis in man such as the long interval between primary infection and tumour appearance, the small number of infected individuals in whom cancer develops, and the monoclonality of the tumours. These cancers are viewed as the result of failing intracellular control of persisting viral genomes in proliferating cells. This type of intracellular surveillance is regarded as a defence mechanism ancestrally older than immunological control, protecting the host at cellular level against potentially lethal effects of coevolving persisting viruses.

Herpes simplex virus type 2 mutagenesis: characterization of mutants induced at the hprt locus of nonpermissive XC cells

In a previous report, herpes simplex virus type 2 (HSV-2) was shown to increase the frequency of mutation at the hypoxanthine phosphoribosyltransferase (hprt) locus of nonpermissive rat XC cells (L. Pilon, A. Royal, and Y. Langelier, J. Gen. Virol. 66:259-265, 1985). A series of 17 independent mutants were isolated after viral infection together with 12 spontaneous noninfected mutants to characterize the nature of the mutations induced by the virus at the molecular level. The DNA of the mutants isolated after viral infection was probed with cloned HSV-2 fragments representing the entire genome. In these mutants, no authentic HSV-2 hybridization could be detected. This was indicative of a mechanism of mutagenesis which did not require the permanent integration of viral sequences in the host genome. The structure of the hprt gene was determined by the method of Southern (J. Mol. Biol. 98:503-517, 1975), and the level of hprt mRNA was analyzed by Northern blots. Except for the identification of one deletion mutant in each of the two groups, the HPRT- clones showed no evidence of alteration in their hprt gene. A total of 7 of 12 spontaneous mutants and 11 of 15 mutants isolated from the infected population transcribed an hprt mRNA of the same size and abundance as did the wild-type cells. Thus, the majority of the mutants seemed to have a point mutation in their hprt structural gene. Interestingly, the proportion of the different types of mutations was similar in the two groups of mutants. This analysis revealed that HSV-2 infection did not increase the frequency of rearrangements but rather that it probably induced a general increase of the level of mutations in the cells. This type of response is thought to be compatible with the biology of the virus, and the possible mechanisms by which HSV-2 induces somatic mutations in mammalian cells are discussed.

Condylomas of the uterine cervix initially interpreted as squamous carcinoma: a report of four cases including a lesion resembling the Buschke-Loewenstein giant condyloma

The recognition of human papilloma virus (HPV)-induced cervicovaginal condylomatous lesions is in a period of dynamic development. It is estimated that condylomatous involvement of the uterine cervix is epidemic and that is particularly true in the younger, more sexually active woman. While cervical condylomas are often associated with cervical dysplasia, carcinoma in situ, or even invasive carcinoma, they are sometimes misdiagnosed as these entities. Four cases of cervical condylomas are presented that were clinically suspicious for malignancy and initially interpreted as squamous carcinomas on the basis of the histopathological findings.

Human papillomavirus (HPV) DNA sequences demonstrated by in situ DNA hybridization in serial paraffin-embedded cervical biopsies

An in situ DNA hybridization technique was used to identify various types of Human papillomavirus (HPV) in paraffin sections of serial punch biopsies taken from 64 patients having colposcopy because of abnormal smears. There women were in fact 64 consecutive patients out of 505 attending our clinic (at 6-month intervals) since 1981 for HPV infections. HPV 6 DNA sequences were found in 20%, HPV 11 in 17%, HPV 16 in 8% and HPV 18 in 5% of the 64 biopsies analysed with this method so far. More than 60% of HPV 6-positive lesions belong to HPV-NCIN (HPV lesion without concomitant CIN) or HPV-CIN I categories, as contrasted with HPV 16-positive lesions, 80% of which belong to HPV-CIN II and III categories. None of the HPV 16- or HPV 18-infected lesions regressed, as contrasted with 23% and 45% in those infected with HPV 6 and HPV 11, respectively (P less than 0.01). The rate of progression (38.4% and 45.5%, respectively) was markedly lower in HPV 6- and HPV 11 lesions as compared with that (80%) of HPV 16 lesions. The present results while supporting the concept on HPV 16 and HPV 18 as the high risk HPV types in cervical carcinogenesis also emphasize the applicability of the in situ DNA hybridization as a powerful tool in analysis of the specific HPV DNA sequences in routinely progressed biopsies of these lesions.

Virus-related pathology: is the continued presence of the virus necessary?

This chapter examines the effect of viruses in inducing modifications in chromosomes, immune system interactions, and cell metabolism to support such a hypothesis that virus may no longer be present when the pathology appears. When vaccines were available to protect the population against the major epidemics, then chronic, recurrent, or persistent infections came into focus. Viruses are everywhere and all organisms are permanently exposed to them. The result of this contact depends on the particular moment a t which a given cell is exposed to the virus. Rubella, for example, provokes a very benign disease in adults, but can induce abnormalities in the differentiating fetus. Although interferon is active against virus aggression, excess interferon has a toxic effect and can block differentiation. The capacity of several viruses to act as cellular mutagens by modifying chromosomes is well established, whatever the molecular mechanism may be. Mutations at the cellular level were carefully analyzed for their tumorigenic potential.

Human papillomavirus (HPV) type as an important determinant of the natural history of HPV infections in uterine cervix

The present report summarizes our current observations on the natural history of cervical HPV (Human papillomavirus) infections, based on data from 418 women prospectively followed-up in our clinic for a mean of 20 +/- 15 (M +/- SD) months. On each attendance at the clinic (at 6-month intervals), the patients are subjected to colposcopy accompanied by PAP smears and/or punch biopsy, both being analysed for the cytopathic changes of HPV, and for concomitant CIN (cervical intraepithelial neoplasia). In the biopsies, the expression of HPV structural proteins was assessed using an indirect immunoperoxidase (IP-PAP) technique. HPV typing was accomplished by spot hybridization with the DNA probes for HPV 6, 11, 16 and 18. During the follow-up, 24% of the HPV lesions regressed, 55% remained persistent, and 21% progressed, 10.6% having been coned due to progression into CIS. The clinical progression was significantly associated with the grade of HPV-associated CIN. On DNA hybridization, HPV 6 was found in 8%, HPV 11 in 36%, HPV 16 in 11% and HPV 18 in 8% of the 103 lesions typed for HPV DNA so far. HPV-CIN lesions were more frequently than HPV-NCIN associated with HPV 16 and HPV 18, as was the expression of HPV structural proteins. The progression rate was highest (45.5%) in HPV 16 lesions, followed by that (27.3%) in HPV 18 lesions, as contrasted to 0% and 13.3% for HPV 6 and 11, respectively. The natural history of cervical HPV lesions seems to be identical with that of classical CIN lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Persistent Epstein-Barr virus infection and a histiocytic sarcoma in a renal transplant recipient

Lymphomas occurring in renal transplant recipients are mostly large cell non-Hodgkin's lymphomas (B-cell-derived). A sarcoma with all morphologic, immunohistochemical, and ultrastructural characteristics of a tumor of the mononuclear phagocytic system (MPS) developed in a 23-year-old woman 1 year after renal transplantation. Anti-Epstein-Barr-virus antibody titers proved to be exceptionally high, even in pretransplant sera. Tumor-derived cells proved to be positive for Epstein-Barr nuclear antigen (EBNA), and hybridization showed multiple copies of Epstein-Barr virus (EBV)-DNA, suggesting a relationship between this tumor and EBV. More widespread use of immunochemical and histochemical diagnostic techniques might detect more cases, which, until now, have probably been diagnosed as B-cell-derived immunoblastic lymphomas.

Burkitt's lymphoma in the Sudan

Burkitt's lymphoma is the commonest of the jaw tumours affecting children in some parts of the tropical Africa. In the Sudan, the tumour appears to be relatively uncommon and our study showed only 7 cases during a 5-year period from December 1975 through to December 1980. The clinical features, aetiology, histopathology and the treatment of the tumour are discussed and the literature briefly reviewed.

Occurrence of papillomavirus structural antigens in oral papillomas and leukoplakias

Six oral papillomas and 7 oral leukoplakias were studied with genus-specific antibodies against detergent-disrupted papillomaviruses. Indirect immunofluorescence staining was applied to frozen sections. Distinct nuclear staining of superficial keratinocytes was seen in 5 of 6 oral papillomas, 2 of 5 homogenous leukoplakias, and in 2 cases of nodular leukoplakia, one of these showing transition into an invasive carcinoma. Papillomavirus antibodies offer a new way to detect and localize papillomaviruses in epithelial hyperplasias. The relevance of the immunomorphological identification of papillomavirus-associated antigens is discussed with special reference to the molecular hybridization technique.

Immunological surveillance of tumors in the context of major histocompatibility complex restriction of T cell function

The immunological surveillance hypothesis was formulated prior to the realization of the fact that an individual's effector T cells generally only see neoantigen if it is appropriately presented in the context of self MHC glycoproteins. The biological consequence of this mechanism is that T lymphocytes are focused onto modified cell-surface rather than onto free antigen. The discovery of MHC-restricted T cell recognition, and the realization that T cell-mediated immunity is of prime importance in promoting recovery from infectious processes, has thus changed the whole emphasis of the surveillance argument. Though the immunological surveillance hypothesis generated considerable discussion and many good experiments, there is no point in continuing the debate in the intellectual context that seemed reasonable in 1970. It is now much more sensible to think of "natural surveillance" and "T cell surveillance," without excluding the probability that these two systems have elements in common. We can now see that T cell surveillance probably operates well in some situations, but is quite ineffective in many others. Part of the reason for this may be that the host response selects tumor clones that are modified so as to be no longer recognized by cytotoxic T cells. The possibility that this reflects changes in MHC phenotype has been investigated, and found to be the case, for some experimental tumors. In this regard, it is worth remembering that many "mutations" in MHC genes that completely change the spectrum of T cell recognition are serologically silent. The availability of molecular probes for investigating the status of MHC genes in tumor cells, together with the capacity to develop cloned T cell lines, monoclonal antibodies to putative tumor antigens, and cell lines transfected with genes coding for these molecules, indicates how T cell surveillance may profitably be explored further in both experimental and human situations.

The oncogenic potential of herpes simplex viruses: evidence for a 'hit-and-run' mechanism

Experiments to determine the mechanism of transformation of herpes simplex virus (HSV) have identified fragments of viral DNA which are able to initiate transformation. No set of viral genes seems to be consistently retained or expressed in the transformed cells or in human cervical tumours, suggesting that viral DNA is not needed to maintain the transformed phenotype. In fact there is no conclusive evidence that initiation of neoplasia is mediated by a viral protein. Here we revisit the 'hit-and-run' hypothesis and its implications for HSV-induced tumorigenicity.

A second look at intraepithelial Langerhans cells in mycosis fungoides and related disorders. Ultrastructural study with special reference to Langerhans granules and virus-like particles

Skin biopsies of patients with small and large plaque parapsoriasis, premycotic lesions and mycosis fungoides in different stages were examined. Special attention was paid to the relationships between Langerhans cells (LC) and the neighbouring keratinocytes and lymphocytes. At the contact areas of LC and keratinocytes as well as LC and lymphocytes, particular cell membrane phenomena were observed. Aggregations of Langerhans granules and fusions of granules with LC plasma membranes were found exclusively at LC-keratinocyte interfaces. At LC-lymphocyte contact zones cell membrane appositions were seen. In all cases investigated, virus-like particles were mainly found in LC and indeterminate cells (IDC). In 3 cases lymphocytes also contained these particles. It was of particular interest that virus-like particles were observed in skin specimens of all diseases investigated. Discrimination of these particles from other cellular organelles - especially lysosomes - was difficult, however. The significance of our findings, particularly regarding to the supposed virus aetiology of cutaneous T cell lymphomas, is discussed.

Analysis of human genital warts (condylomata acuminata) and other genital tumors for human papillomavirus type 6 DNA

32P-labelled cloned HPV 6 DNA was used as probe to analyze human genital tumors for DNA sequences homologous to HPV 6 DNA. Ninety three percent of all condylomata acuminata (41 out of 44) were found to harbor HPV 6 DNA. Of the remaining three, one contained HPV 1 DNA. No papillomavirus DNA was identified in the two other tumors. All three invasively growing giant condylomata acuminata (Buschke-Löwenstein tumors) investigated also contained HPV 6 DNA. Two out of six atypical condylomata of the cervix hybridized with HPV 6 DNA under stringent conditions, one only under conditions of low stringency. All DNA preparations from malignant tumors studies (54 cervical carcinomas, 10 penile carcinomas, two vulvar carcinomas) failed to anneal with HPV 6 DNA, even under conditions of low stringency. Although all HPV 6-positive condylomata acuminata analyzed in this study revealed HPV 6 DNA of regular molecular weight (5.1 x 10(6)), two of the Buschke-Löwenstein tumors, as well as one of the two positive atypical condylomata of the cervix, contained HPV 6 DNA with a remarkable size classes occurred in a supercoiled form without evidence for integration into host cell DNA.

Papovavirus-related RNA sequences in human neurogenic tumours

Thirty-two human brain tumours were investigated for the presence of papovavirus-related RNA sequences. Radiolabelled viral DNAs isolated from SV40, BKV, HDV, and BPV were hybridized in-situ on to tumour kryostat sections under conditions that detect complementary RNA. SV40-related RNA was detectable in 34% of all tumours tested but was not found in normal human brain tissue. SV40-positive tumours included 1/1 angiofibroma, 1/4 astrocytomas, 2/4 metastatic brain tumours, 1/1 melanoma, 3/7 meningiomas, 2/4 neurinomas, 1/2 oligodendrogliomas. Bovine papilloma virus-, BKV-, and HDV-related RNAs were absent from all tissues tested. The presence of SV40-related nucleic acids in a large number of human neurogenic tumours may reflect a viral involvement in the etiology of these tumours.