E5 protein of human papillomavirus type 16 protects human foreskin keratinocytes from UV B-irradiation-induced apoptosis

UVB-induced senescence in human keratinocytes requires a functional insulin-like growth factor-1 receptor and p53

To cope with the frequent exposure to carcinogenic UV B (UVB) wavelengths found in sunlight, keratinocytes have acquired extensive protective measures to handle UVB-induced DNA damage. Recent in vitro and epidemiological data suggest one these protective mechanisms is dependent on the functional status of the insulin-like growth factor-1 receptor (IGF-1R) signaling network in keratinocytes. During the normal UVB response, ligand-activated IGF-1Rs protect keratinocytes from UVB-induced apoptosis; however, as a consequence, these keratinocytes fail to proliferate. This adaptive response of keratinocytes to UVB exposure maintains the protective barrier function of the epidermis while ensuring that UVB-damaged keratinocytes do not replicate DNA mutations. In contrast, when keratinocytes are exposed to UVB in the absence of IGF-1R activation, the keratinocytes are more sensitive to UVB-induced apoptosis, but the surviving keratinocytes retain the capacity to proliferate. This aberrant UVB response represents flawed protection from UVB damage potentially resulting in the malignant transformation of keratinocytes. Using normal human keratinocytes grown in vitro, we have demonstrated that activation of the IGF-1R promotes the premature senescence of UVB-irradiated keratinocytes through increased generation of reactive oxygen species (ROS) and by maintaining the expression of the cyclin-dependent kinase inhibitor p21(CDKN1A). Furthermore, IGF-1R-dependent UVB-induced premature senescence required the phosphorylation of p53 serine 46. These data suggest one mechanism of keratinocyte resistance to UVB-induced carcinogenesis involves the induction of IGF-1R-dependent premature senescence.

Genes involved in cell adhesion, cell motility and mitogenic signaling are altered due to HPV 16 E5 protein expression

We investigated the effects of the human papillomavirus type 16 E5 oncogene on cellular gene expression in human epithelial cells using cDNA microarray. In a genome-wide microarray assay, the expression of 179 genes was found to be significantly altered due to E5 expression. The expression of lamin A/C was downregulated at protein level. The expression of protein kinase C-delta and phosphoinositide-3-kinase proteins was found to be upregulated. We also observed increased motility of E5-expressing cells. We conclude that the E5 protein affects several cellular pathways involved in cell adhesion, cell motility and mitogenic signaling. These alterations may together lead to inhibition of apoptosis and facilitate the establishment of persistent infection in the epithelium.

Human papillomaviruses and cervical cancer

Carcinoma of the uterine cervix, a leading cause of cancer death in women worldwide, is initiated by infection with high-risk types of human papillomaviruses (HPVs). This review summarizes laboratory studies over the past 20 years that have elucidated the major features of the HPV life cycle, identified the functions of the viral proteins, and clarified the consequences of HPV infection for their host cells. This information has allowed the development of various strategies to prevent or treat infections, including prophylactic vaccination with virus-like particles, therapeutic vaccination against viral proteins expressed in cancer cells, and antiviral approaches to inhibit virus replication, spread, or pathogenesis. These strategies have the potential to cause a dramatic reduction in the incidence of cervical carcinoma and serve as the prototype for comprehensive efforts to combat virus-induced tumors.

Human papillomaviruses: basic mechanisms of pathogenesis and oncogenicity

Human papillomaviruses (HPVs) are small double-stranded DNA viruses that infect the cutaneous and mucosal epithelium. Infection by specific HPV types has been linked to the development of cervical carcinoma. HPV infects epithelial cells that undergo terminal differentiation and so encode multiple mechanisms to override the normal regulation of differentiation to produce progeny virions. Two viral proteins, E6 and E7, alter cell cycle control and are the main arbitrators of HPV-induced oncogenesis. Recent data suggest that E6 and E7 also play a major role in the inhibition of the host cell innate immune response to HPV. The E1 and E2 proteins, in combination with various cellular factors, mediate viral replication. In addition, E2 has been implicated in both viral and cellular transcriptional control. Despite decades of research, the function of other viral proteins still remains unclear. While prophylactic vaccines to block genital HPV infection will soon be available, the widespread nature of HPV infection requires greater understanding of both the HPV life cycle as well as the mechanisms underlying HPV-induced carcinogenesis.

The E7 proteins of low- and high-risk human papillomaviruses share the ability to target the pRB family member p130 for degradation

High-risk human papillomaviruses (HPVs) (e.g., HPV-16) cause anogenital and head and neck cancers, and low-risk HPVs (e.g., HPV-6) cause benign hyperproliferative disease. The E7 protein of HPV-16 binds all retinoblastoma tumor suppressor protein (pRB) family members with higher affinity than HPV-6E7. The HPV-16 E7 protein has been reported to target pRB family members for degradation and to immortalize cells. Here we tested the hypothesis that the low-risk E7 protein has an intrinsic ability to decrease expression of pRB family members. First, we introduced a high-affinity pRB-binding site into HPV-6 E7 (6E7G22D) and showed that, in human foreskin keratinocytes, HPV-6 E7G22D decreased the level of pRB protein but not pRB mRNA. Second, we analyzed the ability of wild-type HPV-6 E7 to destabilize the other pRB family members, p107 and p130. HPV-6 E7, like HPV-16 E7, decreased the level of p130 protein. This decrease was inhibited by MG132, a proteasome inhibitor. Binding of HPV-6 E7 to p130 was necessary but not sufficient to decrease the level of p130. Furthermore, the destabilization of p130 correlated with a decrease in the expression of involucrin, a differentiation marker. We suggest that the shared activity of HPV-16 E7 and HPV-6 E7 to destabilize p130 and decrease or delay differentiation may be related to the role of E7 in the HPV life cycle. The added ability of HPV-16 E7 to regulate pRB and p107 may be related to oncogenic activity.

Prevalence of high-risk human papillomavirus DNA in nonkeratinizing (cylindrical cell) carcinoma of the sinonasal tract: a distinct clinicopathologic and molecular disease entity

Carcinomas of the nose and paranasal sinuses are a heterogeneous group of neoplasms that differ histologically, biologically, and clinically. Some of these tumors are known to harbor high-risk human papillomavirus (HPV) DNA. In an attempt to identify specific phenotypes associated with HPV infection, 39 cases of sinonasal carcinomas were evaluated by PCR for the presence of HPV DNA. The tumors were also studied with a panel of immunohistochemical stains, including p16, p53, and Ki-67 antibodies. Twenty-one cases were identified as keratinizing squamous cell carcinoma (KSCC) with a male-to-female ratio of 3:1. Eight cases were nonkeratinizing (cylindrical cell) carcinoma (NKCa) with a male-to-female ratio of 1:1. Ten cases were sinonasal undifferentiated carcinoma (SNUC), and 9 of these patients were men. HPV DNA, particularly type 16, was detected in 9 cases: 4 of 21 (19%) of KSCC, 4 of 8 (50%) of NKCa, and 1 of 10 (10%) of SNUC. In addition to a higher prevalence of HPV DNA in NKCa, the tumors also showed a distinct immunophenotype characterized by strong and diffuse staining for p16, high labeling scores for Ki-67, and negative or low reactivity to p53. On the other hand, KSCC and SNUC were either negative or weakly reactive to p16 antibodies. KSCC cases were more likely to be positive and more strongly reactive to p53 stain. Unlike KSCC, SNUC had high Ki-67 labeling scores. These observations suggest that NKCa of the sinonasal tract is a distinct histopathologic and molecular disease entity, which should be added to the list of upper aerodigestive tract tumors with strong etiologic relationship to high risk HPV.

Endoplasmic reticulum-localized human papillomavirus type 16 E5 protein alters endosomal pH but not trans-Golgi pH

The human papillomavirus type 16 (HPV-16) E5 protein is a small, hydrophobic polypeptide that is expressed in virus-infected keratinocytes and alters receptor signaling pathways, apoptotic responses, and endosomal pH. Despite its ability to inhibit endosomal acidification, the HPV-16 E5 protein is found predominantly in the endoplasmic reticulum (ER), suggesting that its effect may be indirect and perhaps global. To determine whether E5 alters the pHs of additional intracellular compartments, we transduced human keratinocytes with a codon-optimized E5 vector and then quantified endosomal and trans-Golgi pHs using sensitive, compartment-specific, ratiometric pHluorin constructs. E5 protein increased endosomal pH from 5.9 to 6.9 but did not affect the normal trans-Golgi pH of 6.3. Confirming the lack of alteration in trans-Golgi pH, we observed no alterations in the acidification-dependent processing of the proH3 protein. C-terminal deletions of E5, which retained normal expression and localization in the ER, were defective for endosomal alkalization. Thus, E5 does not uniformly alkalinize intracellular compartments, and its C-terminal 10 amino acids appear to mediate interactions with critical ER targets that modulate proton pump function and/or localization.

HPV16 E5 protein disrupts the c-Cbl-EGFR interaction and EGFR ubiquitination in human foreskin keratinocytes

The E5 protein of human papillomavirus type 16 (HPV16) is a small hydrophobic protein, which localizes to the cell membrane, Golgi apparatus and endosomes. HPV16 E5 enhances the activation of the epidermal growth factor (EGFR). The activated EGFR is downregulated through the endocytic pathway, where E5 has been shown to inhibit endosomal acidification and trafficking. Ubiquitination of the activated EGFR plays a role in this downregulation. c-Cbl is a ubiquitin ligase that associates with the activated EGFR and targets it for degradation. Since E5 has been shown to form a complex with the EGFR, we tested the hypothesis that E5 affects the interaction of c-Cbl with the EGFR. We found a significant decrease of c-Cbl bound to the EGFR and of ubiquitinated EGFR in the presence of E5. E5 did not affect c-Cbl steady-state level, phosphorylation or translocation to the membrane. This novel result suggests that HPV16 E5 may, at least in part, upregulate EGFR-mediated signal transduction by inhibiting the interaction of c-Cbl with the EGFR, thereby decreasing c-Cbl-mediated degradation of the EGFR.

Detection of epidermodysplasia verruciformis-associated human papillomavirus DNA in nongenital seborrhoeic keratosis

BACKGROUND

DNA of epidermodysplasia verruciformis (EV)-associated human papillomaviruses (HPVs) has been widely detected in lesions of malignant skin tumours, benign tumours and other proliferative diseases of epithelial origin.

OBJECTIVES

To investigate the presence of EV-associated HPV DNA in nongenital seborrhoeic keratosis (SK) and to elucidate the prevalence of distinct HPV genotypes.

METHODS

We investigated HPV DNA in 55 nongenital SK biopsies, which were compared with 48 normal skin biopsies (healthy controls) using a nested polymerase chain reaction (PCR) using consensus primers CP65/CP70 and CP66/CP69. The positive PCR products were retracted and used to prepare recombination clones with T-vector. Distinct clones were analysed with endonucleases, and HPV genotypes were identified by direct sequencing.

RESULTS

EV-associated HPV DNA was detected in 42 of 55 (76%) nongenital SK biopsies vs. only 13 of 48 (27%) healthy controls (chi2 = 22.087; P < 0.005). The prevalence was higher in patients with more than five lesions than in those with only one lesion (P < 0.05). Ten distinct HPV genotypes were detected in the nongenital SK biopsies: HPV 20, 23, 5, renal transplant recipient (RTR) X7, HPV 17, 37, 17b, RTRX4, RTRX4b and strain SK3. HPV 20 was found in 26 of 42 (62%) positive specimens, followed by HPV 23 (11 of 42, 26%) and HPV 5 (six of 42, 14%). Existence of multiple HPV genotypes was observed in 12 of 42 (29%) positive specimens. In healthy controls, five genotypes of EV-associated HPV (HPV 20, 23, 5, 17 and RTRX4) were detected, with the same predominant genotype of HPV 20 (five of 13, 38%). Several distinct HPV genotypes were found to coexist in four of 13 (31%) positive specimens.

CONCLUSIONS

This study provides some evidence that EV-associated HPVs might play a part in the pathogenesis of nongenital SK.

Role of infectious diseases in human carcinogenesis

The burden of human infectious diseases remains a public health problem worldwide. At least 2 billion people are affected by viral infections, and a similar number by bacteria or helminths. The long-term effects of these maladies have raised particular concern since some infectious agents have been associated with chronic human diseases, especially cancer. It is estimated that 13-20% of the world cancer cases are associated with some virus, bacteria, or helminth, e.g., human papillomavirus, Helicobacter pylori, and Schistosoma haematobium that cause cervical, stomach, and urinary bladder cancer, respectively. Certain associations between infection and malignancy are strong and irrefutable; others are still speculative. This article reviews the infectious agents that have been associated with cancer and current knowledge about the mechanisms underlying these associations.

Human papillomavirus type 16 in head and neck carcinogenesis

The aetiology of squamous cell carcinomas of the head and neck (HNSCC) is multifactorial. Oncogenic human papillomaviruses (HPVs), a causative agent in uterine cervical cancer, have also been repeatedly detected in HNSCC, especially in squamous cell carcinomas of tonsils. Approximately half the HPV DNA-positive HNSCC contain detectable E6/E7 transcripts with wild-type p53, reduced pRb and overexpressed p16 in the tumours. HPV-16 is the predominant type and exists in episomal, integrated, or mixed forms. Tonsillar carcinomas have a remarkably higher viral load than carcinomas at other sites of the head and neck region. HPV-16 DNA has also been detected in tumour-free tonsils. Infection by oncogenic HPVs is a necessary but not a sufficient cause of cancers. Studies on the molecular mechanisms underlying HPV-associated carcinogenesis are difficult, because HPV is not easy to propagate in vitro. HPV-immortalised human tonsillar epithelial cell lines may provide an in vitro model to study co-factors for the HPV-associated tonsillar cancers and to test the effects of anti-viral and anti-tumour agents.

Mucosal human papillomaviruses encode four different E5 proteins whose chemistry and phylogeny correlate with malignant or benign growth

We performed a phylogenetic study of the E2-L2 region of human mucosal papillomaviruses (PVs) and of the proteins therein encoded. Hitherto, proteins codified in this region were known as E5 proteins. We show that many of these proteins could be spurious translations, according to phylogenetic and chemical coherence criteria between similar protein sequences. We show that there are four separate families of E5 proteins, with different characteristics of phylogeny, chemistry, and rate of evolution. For the sake of clarity, we propose a change in the present nomenclature. E5alpha is present in groups A5, A6, A7, A9, and A11, PVs highly associated with malignant carcinomas of the cervix and penis. E5beta is present in groups A2, A3, A4, and A12, i.e., viruses associated with certain warts. E5gamma is present in group A10, and E5delta is encoded in groups A1, A8, and A10, which are associated with benign transformations. The phylogenetic relationships between mucosal human PVs are the same when considering the oncoproteins E6 and E7 and the E5 proteins and differ from the phylogeny estimated for the structural proteins L1 and L2. Besides, the protein divergence rate is higher in early proteins than in late proteins, increasing in the order L1 < L2 < E6 approximately E7 < E5. Moreover, the same proteins have diverged more rapidly in viruses associated with malignant transformations than in viruses associated with benign transformations. The E5 proteins display, therefore, evolutionary characteristics similar to those of the E6 and E7 oncoproteins. This could reflect a differential involvement of the E5 types in the transformation processes.

Human papillomavirus type 16 E7 protein increases acetylation of histone H3 in human foreskin keratinocytes

Histone acetylation plays an important role in chromatin remodeling and transcription control. Acetylation of histones is regulated by histone acetyltransferases and histone deacetylases (HDACs). Human papillomavirus type 16 (HPV16) E7 can inactivate retinoblastoma protein (pRB), which recruits histone deacetylases, and also physically interacts with histone acetyltransferases and histone deacetylases, suggesting E7 may affect histone acetylation. To test this, we have analyzed the state of acetylation of histone H3 in human foreskin keratinocytes. HPV16 E7 increased acetylation of histone H3 on lysine 9, which is related to transcription activation. The ability to bind both pRB and histone deacetylase was required for HPV16 E7 to increase histone acetylation. Chromatin immunoprecipitations showed HPV16 E7 increases histone acetylation on the E2F1 and cdc25A promoters. Consistent with this, RT-PCR analysis showed an increase in the expression of E2F-responsive genes involved in cell cycle control. HPV16 E7 affected neither the steady-state levels of histone acetyltransferases or deacetylases nor histone deacetylase activity. However, HPV16 E7 did increase the level of methylation of histone H3 on lysine 4, which normally requires displacement of histone deacetylase. In contrast, sodium butyrate, a known inhibitor of histone deacetylases, caused an increase in acetylated but not methylated histone H3. These data suggest HPV16 E7, by increasing histone acetylation, may create a transcriptionally active chromatin structure to promote expression of genes vital for cell cycle progression.

Identification of membrane proteins differentially expressed in human papillomavirus type 16 E5-transfected human keratinocytes by nanoelectrospray ionization mass spectrometry

Membrane proteins differentially expressed in human papillomavirus type 16 (HPV-16) E5-transfected HaCaT cells have been identified. Membrane proteins were isolated and separated by two-dimensional gel electrophoresis. Spots showing quantitative differences between E5-transfected and control cells were extracted and the proteins were identified by nanoelectrospray ionization mass spectrometry. A total of 24 spots was analysed. Among the proteins showing differential expression, a decreased amount of calnexin and increased expression of hsp70, proteins both involved in maturation and transport of MHC class I complexes to the plasma membrane, were noticed. These findings correlate with the decreased surface expression of MHC class I molecules described in E5-expressing cells, HPV-positive cervical lesions and cervical carcinomas. These results stress the value of the proteomic approach, as used here in the experimental design, which allows the correlation of changes in host gene expression with biological functions of viral genes.

The HPV-16 E5 protein inhibits TRAIL- and FasL-mediated apoptosis in human keratinocyte raft cultures

By using raft cultures of the polyclonal HaCaT cell lines stably transfected either with E5 (HaCaT/E5) or the empty vector (HaCaT/pMSG) as reference, we investigated the effect of the human papillomavirus type 16 (HPV-16) E5 protein on apoptosis. In comparison to conventional monolayer cultures this model system allows analysis of apoptosis under more tissue-like conditions by mimicking the stratified organization of a normal surface epithelium. Apoptosis was triggered either by FasL or TRAIL. Execution of the death program was checked at early and late stages by monitoring procaspase-3 cleavage and DNA fragmentation, respectively. Rafts of E5-expressing keratinocytes were completely protected from apoptosis and showed a background of apoptotic cells as low as the untreated cultures. In contrast, the HaCaT/pMSG cultures revealed a dramatic increase in apoptotic cells upon ligand treatment throughout the epithelial compartment. We conclude that the presence of the HPV-16 E5 protein in our tissue-like model prevents FasL- or TRAIL-mediated apoptosis.

The human papillomavirus HPV2a E5 protein localizes to the Golgi apparatus and modulates signal transduction

The low-risk human papillomavirus type 2a (HPV2a) has been found associated with benign skin epithelial tumors and has only been very rarely identified in malignized epithelia. Here we report the identification of the E5 gene of HPV2a and demonstrate that the protein is mainly expressed in the Golgi apparatus of transfected cells, similar to the known high-risk types E5 proteins. Further, we present experimental evidence demonstrating that HPV2a E5, similar to HPV16 E5, is able to modulate EGF-mediated erk1/2 MAP kinase activation and to down-regulate the expression of MHC class I molecules at the plasma membrane. Thus, the E5 gene of at least one cutaneous low-risk HPV type displays similar biological characteristics to those described for the high-risk type HPV16.

Codon optimization of the HPV-16 E5 gene enhances protein expression

The human papillomavirus type 16 (HPV-16) E5 protein is an 83-amino-acid, hydrophobic polypeptide that has been localized to intracellular membranes when overexpressed in COS-1 cells. While the HPV-16 E5 protein appears to modulate endosomal pH and signal transduction pathways, genetic analysis of its biological activities has been hampered by low (usually nondetectable) levels of expression in stable cell lines. Sequence analysis of the native HPV-16 E5 gene revealed that infrequent-use codons are used for 33 of its 83 amino acids and, in an effort to optimize E5 expression, we converted these codons to those more common in mammalian genes. The modified gene, 16E5*, generated protein levels that were six- to ninefold higher than those of wild-type HPV-16 E5, whereas the levels of mRNA were unchanged. 16E5* protein was detectable in keratinocytes by immunoblotting, immunoprecipitation, and immunofluorescence techniques and formed disulfide-dependent dimers and higher-order oligomers. Unlike the bovine papillomavirus E5 protein, which is present in the Golgi, 16E5* was localized primarily to the endoplasmic reticulum and its expression reduced the in vitro life span of keratinocytes.

The E5 protein of human papillomavirus type 16 perturbs MHC class II antigen maturation in human foreskin keratinocytes treated with interferon-gamma

Major histocompatibility complex (MHC) class II antigens are expressed on human foreskin keratinocytes (HFKs) following exposure to interferon gamma. The expression of MHC class II proteins on the cell surface may allow keratinocytes to function as antigen-presenting cells and induce a subsequent immune response to virus infection. Invariant chain (Ii) is a chaperone protein which plays an important role in the maturation of MHC class II molecules. The sequential degradation of Ii within acidic endocytic compartments is a key process required for the successful loading of antigenic peptide onto MHC class II molecules. Since human papillomavirus (HPV) 16 E5 can inhibit the acidification of late endosomes in HFKs, the E5 protein may be able to affect proper peptide loading onto the MHC class II molecule. To test this hypothesis, HFKs were infected with either control virus or a recombinant virus expressing HPV16 E5 and the infected cells were subsequently treated with interferon-gamma. ELISAs revealed a decrease of MHC class II expression on the surface of E5-expressing cells compared with control virus-infected cells after interferon treatment. Western blot analysis showed that, in cells treated with interferon gamma, E5 could prevent the breakdown of Ii and block the formation of peptide-loaded, SDS-stable mature MHC class II dimers, correlating with diminished surface MHC class II expression. These data suggest that HPV16 E5 may be able to decrease immune recognition of infected keratinocytes via disruption of MHC class II protein function.

The human papillomavirus type 16 E5 protein impairs TRAIL- and FasL-mediated apoptosis in HaCaT cells by different mechanisms

The effect of the human papillomavirus type 16 (HPV-16) E5 protein on apoptosis was investigated by using the polyclonal HaCaT-cell lines stably transfected either with E5 (HaCaT/E5) or the empty vector (HaCaT/pMSG) as reference. Apoptosis was triggered either by Fas ligand (FasL) or by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and was monitored by detection of cleavage of procaspase-8 and procaspase-3, as well as their substrate poly(ADP-ribose) polymerase (PARP). In contrast to the HaCaT/pMSG control cells we found that apoptosis induced by either of the two ligands is strongly suppressed in the E5-expressing keratinocytes. Fas expression is reduced by about a factor of two in HaCaT/E5 cells, which could be part of the mechanisms that protect the cells from FasL-induced apoptosis. For the TRAIL receptors, no such downregulation was observed. Here, E5 impairs the formation of the death-inducing signaling complex triggered by TRAIL. Apparently, E5 employs different mechanisms to inhibit death receptor signaling. This effect is not restricted to HaCaT/E5 cells since we found that the mouse fibroblast cell line A31-E5 is protected from TRAIL-induced apoptosis, as well but not the E5-lacking control cells A31-Neo. However, no such protection was observed upon FasL-induced apoptosis. Presumably, some of the antiapoptotic mechanisms employed by E5 of the human pathogenic HPV-16 are cell type specific. We propose that inhibition of ligand-mediated apoptosis in human keratinocytes is a primary function of the HPV-16 E5 protein needed to prevent apoptosis at early stages of viral infection.

Intracutaneous DNA vaccination with the E8 gene of cottontail rabbit papillomavirus induces protective immunity against virus challenge in rabbits

The cottontail rabbit papillomavirus (CRPV)-rabbit model has been used in several studies for testing prophylactic and therapeutic papillomavirus vaccines. Earlier observations had shown that the CRPV nonstructural genes E1, E2, and E6 induced strong to partial protective immunity against CRPV infection. In this study, we found that CRPV E8 immunization eliminated virus-induced papillomas in EIII/JC inbred rabbits (100%) and provided partial protection (55%) against virus challenge in outbred New Zealand White rabbits. CRPV-E8 is a small open reading frame, coding for a 50-amino-acid protein, that is colinear with the CRPV E6 gene and has features similar to those of the bovine papillomavirus and human papillomavirus E5 genes. Papillomas that grew on E8-vaccinated outbred rabbits were significantly smaller than those on vector-vaccinated rabbits (P < 0.01; t test). Delayed-type hypersensitivity skin tests showed that some of the E8-vaccinated rabbits had positive responses to E8-specific peptides.

Papillomaviruses and cancer: from basic studies to clinical application

Links between human papillomaviruses (HPVs) and cervical cancer were first suspected almost 30 years ago. DNA of specific HPV types has since been found in almost all cervical cancer biopsies. HPV oncogenes that are expressed in these cells are involved in their transformation and immortalization, and are required for the progression towards malignancy. Epidemiological studies have underlined that HPVs are the main aetiological factor for cervical cancer. But how has this knowledge been translated into the clinic to allow the prevention, screening and treatment of cervical cancer?