Mutation and abnormal expression of the p53 gene in the viral skin carcinogenesis of epidermodysplasia verruciformis

The cutaneous beta human papillomavirus type 8 E6 protein induces CCL2 through the CEBPα/miR-203/p63 pathway to support an inflammatory microenvironment in epidermodysplasia verruciformis skin lesions

Human papillomavirus type 8 (HPV8), a cutaneous genus beta HPV type, has co-carcinogenic potential at sun-exposed sites in patients suffering from the inherited skin disease epidermodysplasia verruciformis (EV). We had previously shown that Langerhans cells responsible for epithelial immunosurveillance were strongly reduced at infected sites and that the HPV8 E7 protein interferes with the CCAAT/enhancer-binding protein (C/EBP)β to suppress the Langerhans cell chemokine CCL20. At the same time, however, we observed that EV lesions are heavily infiltrated with inflammatory immune cells, which is similar to the situation in HPV8 E6 transgenic mice. To identify critical inflammatory factors, we used a broad multiplex approach and found that the monocyte attracting chemokine CCL2 was significantly and strongly induced by HPV8 E6 but not E7-expressing HaCaT cells, which were used as a model for UV-damaged skin keratinocytes. Conditioned media from HPV8 E6-expressing keratinocytes enhanced CCL2-receptor (CCR2)-dependent monocyte recruitment in vitro, and macrophages predominated in the stroma but were also detected in the epidermal compartment of EV lesions in vivo. CCL2 induction by HPV8 E6 was even stronger than stimulation with the proinflammatory cytokine TNF-α, and both HPV8 E6 and TNF-α resulted in substantial suppression of the transcription factor C/EBPα. Using RNAi-mediated knockdown and overexpression approaches, we demonstrated a mechanistic role of the recently identified C/EBPα/miR-203/p63 pathway for HPV8 E6-mediated CCL2 induction at protein and transcriptional levels. Epithelial co-expression of p63 and CCL2 was confirmed in HPV8 E6-expressing organotypic air-liquid interface cultures and in lesional EV epidermis in vivo. In summary, our data demonstrate that HPV8 oncoproteins actively deregulate epidermal immune homeostasis through modulation of C/EBP factor-dependent pathways. While HPV8 E7 suppresses immunosurveillance required for viral persistence, the present study provides evidence that E6 involves the stemness-promoting factor p63 to support an inflammatory microenvironment that may fuel carcinogenesis in EV lesions.

Human Papillomaviruses and Skin Cancer

Human papillomaviruses (HPVs) infect squamous epithelia and can induce hyperproliferative lesions. More than 220 different HPV types have been characterized and classified into five different genera. While mucosal high-risk HPVs have a well-established causal role in anogenital carcinogenesis, the biology of cutaneous HPVs is less well understood.From patients with the rare genetic disorder epidermodysplasia verruciformis (EV) and animal models, evidence is accumulating that cutaneous PV of genus β synergize with ultraviolet (UV) radiation in the development of cutaneous squamous cell carcinoma (cSCC). In 2009, the International Agency for Research on Cancer (IARC) classified the genus β-HPV types 5 and 8 as "possible carcinogenic" biological agents (group 2B) in EV disease. Epidemiological and biological studies indicate that genus β-PV infection may also play a role in UV-mediated skin carcinogenesis in non-EV patients. However, they rather act at early stages of carcinogenesis and become dispensable for the maintenance of the malignant phenotype, compatible with a "hit-and-run" mechanism.This chapter will give an overview on genus β-PV infections and discuss similarities and differences of cutaneous and genus α mucosal high-risk HPV in epithelial carcinogenesis.

Cross-talk of cutaneous beta human papillomaviruses and the immune system: determinants of disease penetrance

Human papillomaviruses (HPVs) infect the epithelia of skin or mucosa, where they can induce hyperproliferative lesions. More than 220 different HPV types have been characterized and classified into five different genera. Mucosal high-risk HPVs are causative for cancers of the anogenital region and oropharynx. Clinical data from patients with the rare genetic disorder epidermodysplasia verruciformis (EV) indicate that genus beta-HPVs cooperate with ultraviolet (UV) radiation in the development of cutaneous squamous cell carcinoma. In addition, epidemiological and biological findings indicate that beta-HPV types play a role in UV-mediated skin carcinogenesis also in non-EV individuals. However, the mechanisms used by these cutaneous viruses to promote epithelial carcinogenesis differ significantly from those of mucosal HPVs. Recent studies point to a delicate cross-talk of beta-HPVs with the cell-autonomous immunity of the host keratinocytes and the local immune microenvironment that eventually determines the fate of cutaneous HPV infection and the penetrance of disease. This review gives an overview of the critical interactions of genus beta-HPVs with the local immune system that allow the virus to complete its life cycle, to escape from extrinsic immunity, and eventually to cause chronic inflammation contributing to skin carcinogenesis. This article is part of the theme issue 'Silent cancer agents: multi-disciplinary modelling of human DNA oncoviruses'.

The transmembrane channel-like protein family and human papillomaviruses: Insights into epidermodysplasia verruciformis and progression to squamous cell carcinoma

Epidermodysplasia verruciformis (EV) is a rare genodermatosis characterized by increased sensitivity to infection by the β-subtype of human papillomaviruses (β-HPVs), causing persistent, tinea versicolor-like dermal lesions. In a majority of affected individuals, these macular lesions progress to invasive cutaneous squamous cell carcinoma (CSCC) in sun-exposed areas. While mutations in transmembrane channel-like 6 (TMC6 / EVER1) and 8 (TMC8 / EVER2) have been causally linked to EV, their molecular functions are unclear. It is likely that their protective effects involve regulation of the β-HPV life cycle, host keratinocyte apoptosis vs. survival balance and/or T-cell interaction with infected host cells.

The p53-microRNA-34a axis regulates cellular entry receptors for tumor-associated human herpes viruses

A growing number of reports indicate the frequent presence of DNA sequences and gene products of human cytomegalovirus in various tumors as compared to adjacent normal tissues, the brain tumors being studied most intensely. The mechanisms underlying the tropism of human cytomegalovirus to the tumor cells or to the cells of tumor origin, as well as the role of the host's genetic background in virus-associated oncogenesis are not well understood. It is also not clear why cytomegalovirus can be detected in many but not in all tumor specimens. Our in silico prediction results indicate that microRNA-34a may be involved in replication of some human DNA viruses by targeting and downregulating the genes encoding a diverse group of proteins, such as platelet-derived growth factor receptor-alpha, complement component receptor 2, herpes simplex virus entry mediators A, B, and C, and CD46. Notably, while their functions vary, these surface molecules have one feature in common: they serve as cellular entry receptors for human DNA viruses (cytomegalovirus, Epstein-Barr virus, human herpes virus 6, herpes simplex viruses 1 and 2, and adenoviruses) that are either proven or suspected to be linked with malignancies. MicroRNA-34a is strictly dependent on its transcriptional activator tumor suppressor protein p53, and both p53 and microRNA-34a are frequently mutated or downregulated in various cancers. We hypothesize that p53-microRNA-34a axis may alter susceptibility of cells to infection with some viruses that are detected in tumors and either proven or suspected to be associated with tumor initiation and progression.

Dermoscopy for the pediatric dermatologist, part ii: dermoscopy of genetic syndromes with cutaneous manifestations and pediatric vascular lesions

Genetic syndromes including basal cell nevus syndrome (BSNS), xeroderma pigmentosum (XP), and epidermodysplasia verruciformis (EV) predispose the individual to skin cancer. Basal cell carcinomas (BCCs) often develop in patients with BCNS and XP. One of the aims of surveillance examination in these patients is to detect BCC while the tumors are still small and easy to manage. Dermoscopy, by allowing the visualization of arborizing vessels, ovoid nests, nonaggregated blue-gray globules, and spoke-wheel and leaf-like structures, can facilitate in the early detection of BCC. Patients with XP are also at risk for developing squamous cell carcinoma (SCC). Dermoscopy can assist in the early detection of these cancers by allowing the observer to visualize focal glomerular vessels, which is a common feature seen in SCC. This feature can also assist in detecting SCC developing in other syndromes such as EV and epidermolysis bullosa (EB). In addition to helping in the detection of BCC and SCC, dermoscopy can also help detect melanoma in individuals with XP and evaluate nevi developing in those with EB. This review will discuss how dermoscopy can be used in the management of patients with BSNS, XP, EV, and EB and will discuss the dermoscopic findings of vascular lesions, including pyogenic granuloma, hemangioma, port-wine stain, and lymphangioma circumscriptum.

HPV 5 and 8 E6 abrogate ATR activity resulting in increased persistence of UVB induced DNA damage

The role of the E6 oncoprotein from high-risk members of the α human papillomavirus genus in anogenital cancer has been well established. However, far less is known about the E6 protein from the β human papillomavirus genus (β-HPVs). Some β-HPVs potentially play a role in non-melanoma skin cancer development, although they are not required for tumor maintenance. Instead, they may act as a co-factor that enhances the carcinogenic potential of UV damage. Indeed, the E6 protein from certain β-HPVs (HPV 5 and 8) promotes the degradation of p300, a histone acetyl transferase involved in UV damage repair. Here, we show that the expression of HPV 5 and 8 E6 increases thymine dimer persistence as well as the likelihood of a UVB induced double strand break (DSB). Importantly, we provide a mechanism for the increased DNA damage by showing that both extended thymine dimer persistence as well as elevated DSB levels are dependent on the ability of HPV 8 E6 to promote p300 degradation. We further demonstrate that HPV 5 and 8 E6 expression reduces the mRNA and protein levels of ATR, a PI3 kinase family member that plays a key role in UV damage signaling, but that these levels remain unperturbed in cells expressing a mutated HPV 8 E6 incapable of promoting p300 degradation. We confirm that the degradation of p300 leads to a reduction in ATR protein levels, by showing that ATR levels rebound when a p300 mutant resistant to HPV 8 mediated degradation and HPV 8 E6 are co-transfected. Conversely, we show that ATR protein levels are reduced when p300 is targeted for degradation by siRNA. Moreover, we show the reduced ATR levels in HPV 5 and 8 E6 expressing cells results in delayed ATR activation and an attenuated ability of cells to phosphorylate, and as a result accumulate, p53 in response to UVB exposure, leading to significantly reduced cell cycle arrest. In conclusion, these data demonstrate that β-HPV E6 expression can enhance the carcinogenic potential of UVB exposure by promoting p300 degradation, resulting in a reduction in ATR levels, which leads to increased thymine dimer persistence and increased UVB induced DSBs.

Human papillomaviruses are a large family of viruses that can cause ailments ranging from benign warts to anogenital cancer. Recently, interest has increased for a subgroup of these viruses, the β-HPVs, because of their potential involvement in squamous cell skin cancer. In this work, we show that the E6 protein from two of these viruses (HPV 5 and 8) is able to increase the damage that UV exposure causes to the host cell's DNA. The E6 protein from these viruses promotes the degradation of p300, a cellular protein involved in DNA damage repair. This in turn reduces amounts of another cellular protein, ATR, which facilitates the process of signaling the cell to repair its damaged DNA. The decrease in ATR levels delays the cell's recognition of the damaged DNA, allowing thymine dimers to remain unrepaired longer and more often leading to a double strand break in the DNA. Together, our data show that the β HPVs can cause UV exposures to be more deleterious to host cell DNA, potentially increasing the likelihood that these cells become cancerous.

Lewandowsky and lutz dysplasia: report of two cases in a family

Lewandowsky and Lutz dysplasia, also known as epidermodysplasia verruciformis (EV), is an inherited disorder in which there is widespread and persistent infection with human papilloma virus, defect in cell-mediated immunity and propensity for malignant transformation. Differential clinical and histopathologic evolutions of lesions in two cases of familial EV are compared and discussed in detail. Cases were followed up for 7 years. Detailed history, clinical features and investigations, including skin biopsy from different sites at different times, were examined. Generalized pityriasis versicolor like hypopigmented lesions in both the cases, together with variable pigmented nodular actinic keratosis like lesions on sun-exposed areas, were present. Multiple skin biopsies done from various sites on different occasions revealed features typical of EV along with lesions, i.e., actinic keratosis, Bowen's disease, basal and squamous cell carcinoma, in the elder sibling. However, skin biopsy of the other sibling showed features of EV and seborrheic keratosis only till date. This study reveals that the disease progression is variable among two individuals of the same family. Malignant lesions were seen only on sun-exposed areas and may be associated with other skin lesions or infections such as angiokeratoma of Fordyce and tinea cruris, as seen in this report.

Epidermodysplasia Verruciformis Associated with Myelodysplastic Syndrome: An Intriguing Association

Background:

Epidermodysplasia verruciformis (EV) is a rare genodermatosis characterized by massive infection with human papillomaviruses (HPVs) and development of skin cancer. Myelodysplastic syndromes (MDSs) are a group of chronic conditions that involve dysplastic hematopoiesis, peripheral blood cytopenias, and a high incidence of progression into leukemia.

Methods:

We describe the intriguing association of these two premalignant conditions (EV and MDS) in one patient. These diagnoses were confirmed by histopathologic examination and cytogenetic abnormalities of bone marrow cells.

Results:

The patient presented initially with clinical features typical of EV and impairment of cell-mediated immunity. In the skin lesions, HPVs 23 and 25 were identified by nested polymerase chain reaction. Six years later, he had recurrent episodes of mucosal bleeding with fever, weakness, and fatigue. At this time, severe refractory anemia and neutropenia were observed, and bone marrow smears showed hypercellularity with abnormal dysplastic megakaryocytes. The cytogenetic pattern showed abnormalities involving trisomy of chromosomes 8 and 21. The patient received a diagnosis of the indolent subtype of MDS.

Conclusions:

Through the observation of our patient and review of the literature, we hypothesized that the pathomechanisms, including the role of oncogenes and cytokines, are connected to the progression to malignancy in these settings.

Genetics of epidermodysplasia verruciformis: Insights into host defense against papillomaviruses

Epidermodysplasia verruciformis (EV) is a rare autosomal recessive genodermatosis associated with a high risk of skin carcinoma. EV results from an abnormal susceptibility to infection by specific human papillomavirus (HPV) genotypes (beta-papillomaviruses) which include the potentially oncogenic HPV5. EV-specific HPVs are considered as harmless for the general population. EV was recently found to be caused by invalidating mutations in two adjacent, related, novel genes, EVER1/TMC6 and EVER2/TMC8. EVER genes encode transmembrane proteins located in the endoplasmic reticulum, which are likely to function as modifiers of ion transporters or channels and to be involved in signal transduction. It was proposed that EV was a primary defect of innate immunity. Our hypothesis is that EVER proteins act as restriction factors for EV-specific HPVs in keratinocytes, and that EV represents a primary deficiency of intrinsic immunity against certain papillomaviruses.

Epidermodysplasia Verruciformis: An Unusual Presentation

BACKGROUND Epidermodysplasia verruciformis (EV) is a rare autosomal recessive genetic disorder of the immune system manifested by increased susceptibility to cutaneous human papillomavirus (HPV) infection beginning from the early years of life, and compromising lesions resembling flat warts, especially on the distal extremities and the face; but malignant transformation occurs in sun-exposed areas within the third or fourth decade of life. OBJECTIVE We describe two case reports of epidermodysplasia verruciformis, one of which was onset and had more aggressive features than the usual presentation. METHODS Intermittent surgical excision of the tumoral lesions were performed in the first case, whereas only one surgical intervestion was sufficient in the second case. RESULTS The early onset case was more aggressive, and new tumoral lesions were seen, whereas the other patients was free of the disease for 2 years.CONCLUSION Epidermodysplasia verruciformis possess multi factorial etiologies, and the main prognostic factor of the behavior of the disease may be the family history and genetic susceptibility.

The Effect of Ultraviolet Radiation on Human Viral Infections

Exposure to UV radiation is recognized to suppress cell-mediated immunity and therefore could adversely affect the course of a viral infection. Rodent models of viral infection confirm this possibility but the situation in human subjects is not so clear, apart from two exceptions. These are herpes simplex, in which sunlight exposure can cause reactivation, and certain papillomavirus types in which sunlight exposure can lead to the development of nonmelanoma skin cancer. In both cases, there are UV response elements in the viral genomes that alter the normal interactions between the viruses and the host following exposure, and UV-induced effects on the immune response occur in addition. These complex mechanisms are discussed, and the situation regarding UV radiation and viral exanthems plus other viruses, including the retroviruses, summarized. Finally viral vaccination is considered in the context of UV exposure and the importance of the host's genetic background emphasized. Further research is required to evaluate whether sunlight can significantly affect the resistance to common viral infections and vaccines.

Human papillomaviruses and skin cancer

Cutaneous epidermodysplasia verruciformis (EV)-associated human papillomaviruses (HPVs) are found frequently in skin cancers especially in immunosuppressed people. They are also detectable in the normal skin and hair follicles of a proportion of individuals who have no immune defect. The available evidence to link HPVs causally with skin carcinogenesis is not conclusive, but includes epidemiological, molecular and immunological studies.

INK4-ARF and p53 mutations in metastatic cutaneous squamous cell carcinoma: case report and archival study on the use of Ink4a-ARF and p53 mutation analysis in identification of the corresponding primary tumor

So far, histopathologic, immunohistochemical and molecular properties of metastatic cutaneous squamous cell carcinomas (CSCCs) are relatively unexplored. In patients with multiple CSCCs, as for instance renal transplant recipients (RTRs), it might prove difficult to identify the primary tumor responsible for metastasis. We report a case of an RTR with multiple CSCCs, one of which metastasized. By using p53 and INK4a-ARF mutation analysis, we identified the responsible primary tumor due to an identical mutation in exon 2 of the INK4a-ARF locus. Archival study yielded 14 cases of metastatic CSCC (present case included). In only 8 of 14 metastases, DNA quality was sufficient to perform PCR reactions. In 7 of 8 metastases, either an INK4a-ARF (6 of 8 cases) and/or p53 (3 of 8 cases) mutation was present. In 6 of 7 cases, the corresponding primary could be identified by an identical mutation in p53 and/or INK4a-ARF. In conclusion, molecular analysis using a combination of p53 and INK4a-ARF mutation analysis can identify the corresponding primary skin tumor in case of CSCC metastases in the majority of cases. This is facilitated by the high frequency of these mutations in metastatic CSCC when compared with frequency spectra reported in the literature in primary CSCCs. The major limitation was formed by insufficient DNA quality in archival tissue.

Giant basal cell carcinoma associated with human papillomaviruses infection

Different criteria have been used to define giant basal cell carcinoma (BCC). However, the majority of tumors of 10 cm or greater in diameter have a characteristic clinical and histopathologic presentation. As a group, these tumors often show metastatic spread as opposed to all other BCCs that rarely metastasize. We present an additional patient with a giant BCC greater than 100 cm2. This tumor had a characteristic location and infiltrative growth pattern. Unusual features of this tumor included a lack of expression of BCL-2 with a greater proportion of cycling tumor cells expressing proliferation markers than conventional BCC, as well as expression of anogenital human papillomaviruses (HPV) subtypes with oncogenic potential. The association of HPV with BCCs has rarely been studied and may not be identical to HPV-induced genital squamous cell carcinomas. However, the findings in this patient suggest that HPV may play a role in the development of some chronic giant BCCs.

Pigmented Epidermal Plaques in Three Dogs

Papillomavirus was identified in pigmented epidermal plaques (PEP) from three dogs: a miniature schnauzer with hyperadrenocorticism and hypoglobulinemia, an American Staffordshire terrier with hypoglobulinemia, and a Pomeranian with unconfirmed hypothyroidism. Squamous cell carcinoma (SCC) arose within several plaques in the Pomeranian. Clinical improvement coincided in the first two cases with treatment of the concurrent disease and the administration of low-dose oral interferon-α. This is the first report of PEP in an American Staffordshire terrier and a Pomeranian. The potential for malignant transformation of PEP to SCC emphasizes the need for recognition and clinical management of PEP.

Possible involvement of epidermodysplasia verruciformis human papillomaviruses in the immunopathogenesis of psoriasis: a proposed hypothesis

We have shown previously in psoriasis a very high prevalence of epidermodysplasia verruciforms-associated human papillomavirus 5 (EVHPV5) DNA and antibodies to human papillomavirus 5 (HPV5) virus-like particle (VLP) L1, and we suggested that this benign hyperproliferative disorder could be a reservoir for EVHPVs. Here we provide new data confirming the expression of EVHPVs in psoriasis and present our hypothesis on their possible involvement in the immunopathogenesis of the disorder. The new important finding was detection by radioimmunoprecipitation assay of a very high prevalence of antibodies to E6/E7 HPV5 oncoproteins, known to enhance keratinocyte proliferation. More recently, EV genes were identified, EVER1 and EVER2, whose mutations are responsible for epidermodysplasia verruciformis. Eidermodysplasia verruciforms-associated human papillomaviruses are harmless to the general population as a result of genetic restriction, which in psoriasis appears to be partly alleviated, and this may allow the viral gene expression. We hypothesize that induction of keratinocyte proliferation in psoriasis by various stimuli initiates the EVHPV life cycle with expression of early (E6/E7) and late (L1) viral proteins. The early proteins may, in turn, enhance the keratinocyte proliferation, and the late proteins could serve as target for specific-B- and T-cell-mediated responses. Immune responses against the viral antigens in the epidermis may result in the chemoattraction of leukocytes and Munro abscess formation, as well as in production of the psoriatic process. The novel immunomodulatory therapies could also inhibit immune responses against EVHPV proteins, leading to decreased cytokine production, keratinocyte proliferation and EVHPV expression. Thus the beneficial effect of these therapies is not discordant with the propose hypothesis of possible involvement of EVHPVs in the immunopathogenesis of psoriasis.

p53 mutations are common in human papillomavirus type 38-positive non-melanoma skin cancers

In cervical cells, the E6 protein of the oncogenic human papillomavirus (HPV) types inactivates p53, promoting its degradation. Consequently, mutations of the p53 gene are rarely seen in these cancers. Our recent data indicate that the cutaneous HPV38 is involved in skin carcinogenesis. In this study, we have determined the presence of HPV38 and the status of p53 gene in 32 non-melanoma skin cancers. We found that p53 gene is frequently mutated in HPV38-positive skin cancers and that HPV38 E6 does not promote p53 degradation. Thus, different mechanisms appear to be involved in the development of HPV-positive cervical and skin cancers.

Association of p53 arginine polymorphism with skin cancer

BACKGROUND

The presence of arginine at codon 72 in p53 protein is proposed to be a genetic risk factor in human papillomavirus (HPV)-related carcinogenesis.

OBJECTIVE

To study the prevalence of p53 polymorphism at codon 72 in skin biopsies of epidermodysplasia verruciformis (EV) patients compared to DNA samples from healthy individuals.

PATIENTS AND METHODS

DNA samples extracted from normal skin and tumor biopsies of 22 Brazilian patients with EV and blood samples from 27 healthy Brazilian individuals were studied for p53 codon 72 polymorphisms using restriction fragment length polymorphism (RFLP) analysis.

RESULTS

All EV patients with the malignant form of EV were homozygous for arginine (Arg/Arg) at codon 72 of the p53 gene, in contrast to none with the benign form (P < 0.0001).

CONCLUSIONS

p53 arginine polymorphism is likely to be associated with the development of skin malignancies in EV patients from Brazil.

Squamous cell carcinoma in situ of the skin: History, presentation, biology and treatment

Squamous cell carcinoma in situ (SCCIS) of the skin is a problem commonly dealt with by dermatologists. The classic presentation, originally described by Bowen, is easily recognized, but presentation on some anatomical surfaces may be associated with less than typical features. Major aetiological factors for this disease are UV light, human papillomavirus infection and immunosuppression. The natural course of SCCIS is usually prolonged, with treatment being appropriate, but not urgent. The choice of therapy requires consideration of the location of the lesion, and a desire for a high cure rate without causing loss of form, function or cosmesis. The immunomodulatory agent imiquimod has offered a significant advance for the topical treatment of SCCIS. Our improved understanding of the underlying biology of SCCIS permits us to make rational choices of treatment. In the future we may be able to determine which of these lesions may progress to invasive disease, and help us select the most effective therapy.

Treatment of Bowen's disease and erythroplasia of Queyrat

Bowen's disease of the skin may have differing clinical presentations depending on the skin surface on which it presents, but has the same histologic features of squamous cell carcinoma in situ wherever it occurs. The etiologic factors include ultraviolet light and human papillomavirus infection. The choice of therapy requires a consideration for retention of form, function and cosmosis while offering a high cure rate. The immunodualtory agent imiquimod has been shown to be an effective treatment on a variety of skin surfaces.

Chapter 8: Human papillomavirus and skin cancer

A high prevalence of human papillomavirus (HPV) DNA, particularly in squamous cell skin carcinoma of immunosuppressed but also of immunocompetent patients, has renewed great interest in a possible etiologic role of HPV in nonmelanoma skin cancer. It is difficult, however, to interpret these findings against a background of low-level infections with multiple HPV types from supergroup B (HPV4-related and epidermodysplasia verruciformis [EV] HPV), probably acquired by everyone early in and throughout life. Thus far, no high-risk HPV types have been identified. Because of the low copy numbers of HPV DNA in skin cancers, probably not every tumor cell contains a viral genome, which is compatible with cutaneous HPV being possibly important for tumor initiation and progression, but not for maintenance of the malignant phenotype. The question with regard to high-risk types should, therefore, be readdressed in case-control studies on the basis of serology, which can reveal viral activities over years. The viruses lingering in all people are apparently activated by sunlight (UV) exposure, by immunosuppression, and by hyperproliferation of the epithelium (psoriasis) and/or in the specific genetic background of the host (EV). It is intriguing that most of these factors are established risk factors in skin carcinogenesis. The weak transforming activity of cutaneous HPV in vitro compared with the transforming activity of genital HPV may explain the need for activators and synergistic factors. The antiapoptotic activities of E6 proteins of cutaneous HPV could be relevant to oncogenesis in the interplay with UV exposure. Prospective studies should determine the kinetics of HPV activation relative to tumor development.

Dual role of tumor suppressor p53 in regulation of DNA replication and oncogene E6-promoter activity of epidermodysplasia verruciformis-associated human papillomavirus type 8

Human papillomavirus 8 (HPV8) is a representative of Epidermodysplasia verruciformis (EV)-associated viruses. Transient assays in the human skin keratinocyte cell line RTS3b have shown that its replication depends in trans on expression of the viral proteins E1 and E2, similarly to other HPVs. Using deletion mutants and cloned subfragments of the noncoding region (NCR) of HPV8 we identified a 65-bp sequence in the 3' part of the NCR to be necessary and sufficient to support replication in cis. The origin of replication (ori) of HPV8 is composed of the sequence motifs "CCAAC" (nt 57-73) and M29 (nt 84-112), which are highly conserved among the majority of EV HPVs. Analysis of M29 revealed an unconventional binding site of the E2 protein and an overlapping DNA recognition site of the tumor suppressor protein p53. Both these factors competitively bind to M29. In transient replication assays p53 acted as a potent inhibitor of ori activity, most probably in a DNA-binding-dependent fashion. The minimal ori sequences are also functionally critical for the E6 oncogene promoter P(175). In contrast to its effect on replication, p53 stimulated promoter activity depending on its interaction with M29. Our observations suggest that p53 is involved in controlling the balance between DNA replication and gene expression of HPV8.

Human papillomaviruses and non-melanoma skin cancer

Epidemiological and experimental studies have overwhelmingly confirmed human papillomaviruses as important causal agents in anogenital carcinogenesis. A role for human papillomaviruses has also been proposed in a diverse range of other malignancies, and particular interest has focused on non-melanoma skin cancer, the commonest malignancy in fair-skinned populations worldwide. Although the evidence for this is considerably less convincing than for anogenital cancer, important epidemiological and functional data have emerged over the past year that have furthered our understanding of the possible contribution of human papillomaviruses to skin cancer. Epidemiological human papillomavirus DNA detection studies have shown associations with non-melanoma skin cancer, but have also emphasized the ubiquity of epidermodysplasia verruciformis human papillomavirus types in normal skin, hair follicles and benign hyperproliferative disorders, as have seroepidemiological approaches. Functional investigations have demonstrated mechanistically relevant interactions between the virus and ultraviolet radiation, host cytokines and cellular proteins including p53 and the pro-apoptotic protein Bak. Taken together, these data have advanced our understanding of the contribution of human papillomaviruses to malignant transformation in cutaneous keratinocytes, but further research is required before a causal association between human papillomaviruses and skin cancer is reliably confirmed.