The promoter of a novel human papillomavirus (HPV77) associated with skin cancer displays UV responsiveness, which is mediated through a consensus p53 binding sequence

UVB irradiation reduces the half-life and transactivation potential of the human papillomavirus 16 E2 protein

Human papillomaviruses (HPV) are causative agents of human cancers including those of the cervix and also of the head and neck; HPV16 is the most commonly found type in these diseases. The viral E2 protein regulates transcription from the viral genome by interacting with DNA-binding sequences in the HPV transcriptional control region; it also regulates replication by interacting with and recruiting the HPV replication factor E1 to the viral origin. Therefore, E2 is essential for the viral life cycle. The E2 protein interacts with several proteins involved in the cellular response to DNA damage including p53, TopBP1, and PARP. We therefore set out to establish whether DNA-damaging agents can regulate E2 activity. Here we show that UVB irradiation downregulates transcriptional activity of both HPV16 and HPV8 E2, while hydroxyurea and etoposide do not. This downregulation of E2 activity is independent of p53 function as it occurs in p53 wild type and null cell types as well as in the presence of functional HPV16 E6 that degrades p53. Using stable cell lines expressing E2 we show that this downregulation of E2 function by UVB is due to a reduction of the E2 protein half-life. The identification of the pathway(s) through which UVB downregulates E2 transcriptional activity and protein levels will present a novel target for the treatment of HPV-related diseases.

A broad spectrum of human papillomavirus types is present in the skin of Australian patients with non-melanoma skin cancers and solar keratosis

BACKGROUND

Human papillomavirus (HPV) may play a role in the pathogenesis of non-melanoma skin cancer (NMSC) in epidermodysplasia verruciformis (EV) patients, but in the general population no specific HPV types have been associated with these lesions. Objectives To examine the spectrum of HPV types present in the skin and tumours of Australian patients with NMSC or solar keratosis (SK).

METHODS

Biopsies from tumours, and cotton swab samples of perilesional skin and buttock skin from each of 59 Australian patients with basal cell carcinoma (BCC), squamous cell carcinoma (SCC) or SK were tested for HPV DNA by polymerase chain reaction (PCR) using HPV consensus (FAP) primers and by type-specific primers for HPV 38 and candidate HPV 92. The identification of HPV type from consensus PCR was performed by sequencing and comparison with GenBank.

RESULTS

In total, 49 of 59 (83%) patients harboured HPV DNA, which was detected in 28 of 64 (44%) biopsies, 48 of 64 (75%; P < 0.001) perilesional swabs and 36 of 59 (61%; P = 0.04) buttock swabs. Forty-five different HPV types/putative types were detected: 15 were previously characterized HPV types, 17 were earlier described putative types and 13 were new putative types. In addition, six subtypes and four variants of HPV sequences were identified. HPV types within the B1 group (EV HPV types) were found in 26 of 64 (40%) lesions, 44 of 64 (69%) perilesional swabs and 35 of 59 (59%) buttock swabs. HPV 38 was detected in 23 of 59 (39%) patients, and was found in seven of 16 (43%) SKs, but was less common in SCCs [three of 23 (13%); P = 0.037] and BCCs [four of 25 (16%); P = 0.056]. Candidate HPV 92 was found in seven of 59 (12%) patients.

CONCLUSIONS

A broad spectrum of HPV types, the majority from the B1 group, was found in skin of Australian patients with skin tumours. HPV 38 was found significantly more often in SK than in SCC. However, the role of cutaneous HPV infection in the pathogenesis of NMSC remains elusive.

The role of p53 in the immunobiology of cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma is typically characterized by the over-expression of the tumour suppressor protein p53. Considerable evidence suggests that immune competence is important in the control of cutaneous SCC. We discuss the immunobiology of p53 and its relevance to cutaneous SCC, including the potential interaction with human papillomavirus.

Epithelial malignancies in organ transplant patients: clinical presentation and new methods of treatment

Transplantation of solid organs has been well established as a mode of therapy for the treatment of various end-stage organ diseases for many years. Up to now, it has benefited more than 1 million patients worldwide. The long-term success of organ transplantation depends particularly on the prevention of allograft rejection. Various regimens have been used to suppress hosts' cellular immune responsiveness to the grafted organs. Nowadays immunosuppressive therapies consist mainly in prednisolone, azathioprine, cyclosporine, anti-T-lymphocyte-globulin (ATG), anti-CD 3 antibody (OKT3) and substances of a new generation, such as tacrolimus or mycophenolic acid. However, not only the patient's reactivity to the graft is impaired, but also that to infectious organisms. Chronically altered immune responsiveness is especially associated with a dramatically increased risk of malignancy, most frequently non-Hodgkin's lymphoma and skin cancer. Within the first 5 years of immunosuppression 40% of transplant recipients experience premalignant skin tumors such as actinic keratoses and Bowen's disease, and also such skin cancers as squamous cell carcinomas and basal cell carcinomas. Quite often these have an aggressive biology and an uncommon morphology. Cancer is now responsible for a mortality rate of 5-8% in organ transplant patients. Various risk factors, such as exposure to sun and infections with oncogenic viruses (e.g. HPV) contribute to the already increased risk of dysplasia when lifelong immunosuppression is required. Prophylactic strategies therefore include the development of virus-like particles (VLPs) as anticancer vaccines, which might become a very interesting approach to preventing HPV-associated cancer. The prevention of precancerous conditions and mature skin cancers in grafted patients includes protective clothing and adequate protection of UV-exposed skin regions, including lips, from sunlight with appropriate sunscreen. Close dermatological surveillance through a specialized outpatient department should be ensured to detect potentially fatal skin malignancies at an early stage. Early treatment of precancerous lesions includes topical retinoids, such as tretionin, tazarotene or adapalene. A 5% fluorouracil cream is widely used but shows variable effects on manifest actinic keratoses. As cellular immunity seems to play the major part in the prevention and cure of malignant and premalignant cutaneous neoplasias as well as viral infections, a specific enhancement of the local immunity would be desirable. Imiquimod is one of a class of agents known as immune response modifiers. The drug has been shown to have both antiviral and antitumor activity. Application of immune response activators or modifiers such as imiquimod might be premising in the case of transplant recipients.

Papillomaviruses: death-defying acts in skin cancer

Ultraviolet (UV) radiation is an environmental agent that has a major impact on humans, and cumulative exposure poses a serious risk in terms of developing skin cancer. Acute doses of UV induce apoptotic cell death in the skin via signalling pathways that are, in part, dependent on the p53 tumour suppressor protein. However, p53-independent mechanisms have also been described. Recent findings show that a high proportion of non-melanoma skin cancers contain human papillomavirus. The viral E6 protein effectively blocks the epidermal apoptotic response to UV and might play a key role in promoting tumour development in cooperation with the mutagenic effects of UV.

Skin cancer in organ transplant recipients: Epidemiology, pathogenesis, and management

In the United States more than 100,000 people are living with solid organ transplants. The intense immunosuppressive regimens necessary for prolonged survival of allografts significantly increase the rates of both internal and cutaneous malignancies in recipients of solid organ transplants. Skin cancer is the most common cancer in patients after transplantation. Because of the early onset and high tumor burden in transplant recipients, dermatologists have significant challenges in managing the treatment of these patients. This article describes the epidemiology and clinical presentation of skin cancer during posttransplantation immunosuppression, discusses pathogenic cofactors, and reviews the optimal management for mild and severe skin cancer in transplant recipients.

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.

Association between epidermodysplasia verruciformis-associated human papillomavirus DNA in plucked eyebrow hair and solar keratoses

Epidermodysplasia-verruciformis-associated human papillomavirus DNA has been demonstrated in squamous cell carcinomas and plucked hair from immunocompetent patients and renal transplant recipients. This study investigated the association between infection with epidermodysplasia-verruciformis-associated human papillomavirus, identified by the detection of viral DNA in plucked eyebrow hairs, and solar keratoses. These lesions are strongly predictive of squamous cell carcinoma. In a cross-sectional study 518 individuals were enrolled from a randomly selected sample of a subtropical Australian community. Epidermodysplasia-verruciformis-associated human papillomavirus DNA in eyebrow hair was detected using a nested polymerase chain reaction specific for epidermodysplasia-verruciformis-associated human papillomavirus types. Epidermo dysplasia-verruciformis-associated human papillomavirus DNA was present in 121 (49%) of 245 men and 116 (44%) of 262 women. There was a strongly significant increase in epidermodysplasia-verruciformis-associated human papillomavirus infection with age (p < 0.00001), with prevalences of 29% in the 25-39 y age group, 42% at 40-59 y and 65% in the 60-79 y age group. Among men there was a strong association between epidermodysplasia-verruciformis-associated human papillomavirus and solar keratoses with an odds ratio, adjusted for age, skin color, and occupational sun exposure, of 3.40 (95% confidence interval, 1.77-6.53). No such association was found among women [odds ratio 1.03 (95% confidence interval 0.59-1.77, after adjustment for the same factors)]. Differences in occupational sun exposure and smoking histories could not explain these apparently different associations between epidermodysplasia-verruciformis-associated human papillomavirus infection and solar keratoses in men and women. In conclusion, epidermodysplasia-verruciformis-associated human papillomavirus infection is associated with solar keratoses in men suggesting that epidermodysplasia-verruciformis-associated human papillomavirus infection, in conjunction with sex specific factors (like androgens), may be involved in neoplastic changes of keratinocytes.

Role of Bak in UV-induced apoptosis in skin cancer and abrogation by HPV E6 proteins

Ultraviolet B (UVB) damage is recognized as the most important etiological factor in the development of skin cancer. Human papillomaviruses (HPV) have also been implicated in the disease, although the mechanism of action of these viruses remains unknown. We present evidence here that Bak protein is involved in signaling apoptosis in the skin in response to UVB damage, and that cutaneous HPV E6 proteins target and abrogate Bak function by promoting its proteolytic degradation both in vitro and in regenerated epithelium. Additionally, HPV positive skin cancers had undetectable levels of Bak in contrast to HPV negative cancers, which expressed Bak. This study supports a link between the virus and UVB in the induction of HPV-associated skin cancer and reveals a survival mechanism of virally infected cells.

Papillomaviruses in non-melanoma skin cancer: epidemiological aspects

Worldwide, non-melanoma skin cancers (NMSCs), which include squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), are the most commonly diagnosed cancers among Caucasians. It is well established that ultraviolet radiation (UVR) plays a central role in the development of these cancers, and more recently, a role for specific genetic mutations in the pathogenesis of BCC has been identified. The possibility that certain types of HPV, either alone or in conjunction with UVR, may play a role in the pathogenesis of these cancers is suggested by several lines of evidence reviewed below.*9 @2depidemiology / non-melanoma skin cancer / papillomavirus

Human papillomaviruses in non-melanoma skin cancer

Recent data suggest that additional factors, other than UV radiation, are involved in the etiology of non-melanoma skin cancer. These include alterations in the tumor suppressor genes, p53, p16$L*I*U$LINK4a$L*I$L/CDKN2A, p21$L*I*U$LWAF1/CIP1$L*I$L and the PTCH gene, as well as cytokines. Papillomavirus infections have been implicated in the etiology of non-melanoma skin cancer. The interaction of tumor suppressor genes and cytokines with the oncoproteins of high-risk mucosal HPV types have been studied in detail, but very little is known about the cutaneous HPV types. We have studied the effect of UV radiation on the URRs of HPV 1, 2, 3, 5, 7, 20, 23, 27, 38, 41, and 77. Neither the CAT-expression and promoter activity of these HPV types, nor presence or absence of wild-type or mutated p53 in the cell lines used, could be related to the DNA sequence homology between the different HPV types or their biological behavior.