A recent report that 93 per cent of invasive cervical cancers worldwide contain human papillomavirus (HPV) may be an underestimate, due to sample inadequacy or integration events affecting the HPV L1 gene, which is the target of the polymerase chain reaction (PCR)‐based test which was used. The formerly HPV‐negative cases from this study have therefore been reanalysed for HPV serum antibodies and HPV DNA. Serology for HPV 16 VLPs, E6, and E7 antibodies was performed on 49 of the 66 cases which were HPV‐negative and a sample of 48 of the 866 cases which were HPV‐positive in the original study. Moreover, 55 of the 66 formerly HPV‐negative biopsies were also reanalysed by a sandwich procedure in which the outer sections in a series of sections are used for histological review, while the inner sections are assayed by three different HPV PCR assays targeting different open reading frames (ORFs). No significant difference was found in serology for HPV 16 proteins between the cases that were originally HPV PCR‐negative and ‐positive. Type‐specific E7 PCR for 14 high‐risk HPV types detected HPV DNA in 38 (69 per cent) of the 55 originally HPV‐negative and amplifiable specimens. The HPV types detected were 16, 18, 31, 33, 39, 45, 52, and 58. Two (4 per cent) additional cases were only HPV DNA‐positive by E1 and/or L1 consensus PCR. Histological analysis of the 55 specimens revealed that 21 were qualitatively inadequate. Only two of the 34 adequate samples were HPV‐negative on all PCR tests, as against 13 of the 21 that were inadequate ( p< 0·001). Combining the data from this and the previous study and excluding inadequate specimens, the worldwide HPV prevalence in cervical carcinomas is 99·7 per cent. The presence of HPV in virtually all cervical cancers implies the highest worldwide attributable fraction so far reported for a specific cause of any major human cancer. The extreme rarity of HPV‐negative cancers reinforces the rationale for HPV testing in addition to, or even instead of, cervical cytology in routine cervical screening. Copyright © 1999 John Wiley & Sons, Ltd.

Notch proteins are important in binary cell-fate decisions and inhibiting differentiation in many developmental systems, and aberrant Notch signaling is associated with tumorigenesis. The role of Notch signaling in mammalian skin is less well characterized and is mainly based on in vitro studies, which suggest that Notch signaling induces differentiation in mammalian skin. Conventional gene targeting is not applicable to establishing the role of Notch receptors or ligands in the skin because Notch1-/- embryos die during gestation. Therefore, we used a tissue-specific inducible gene-targeting approach to study the physiological role of the Notch1 receptor in the mouse epidermis and the corneal epithelium of adult mice. Unexpectedly, ablation of Notch1 results in epidermal and corneal hyperplasia followed by the development of skin tumors and facilitated chemical-induced skin carcinogenesis. Notch1 deficiency in skin and in primary keratinocytes results in increased and sustained expression of Gli2, causing the development of basal-cell carcinoma-like tumors. Furthermore, Notch1 inactivation in the epidermis results in derepressed beta-catenin signaling in cells that should normally undergo differentiation. Enhanced beta-catenin signaling can be reversed by re-introduction of a dominant active form of the Notch1 receptor. This leads to a reduction in the signaling-competent pool of beta-catenin, indicating that Notch1 can inhibit beta-catenin-mediated signaling. Our results indicate that Notch1 functions as a tumor-suppressor gene in mammalian skin.

Several autoinflammatory disorders such as Muckle-Wells syndrome are characterized by mutations in the NALP3/cryopyrin gene. NALP3 and NALP1 proteins can assemble to inflammasomes that activate caspase-1, resulting in the processing of pro-inflammatory cytokines IL-1beta and IL-18. The present study was designed to determine which cells and tissues express NALP1 and NALP3. Monoclonal antibodies were developed and their use revealed distinct distribution profiles of NALP1 and NALP3. Granulocytes, monocytes (very weakly), dendritic cells, and B and T cells all express NALP1 and NALP3. Highest levels of NALP1 are found in T cells and Langerhans cells. Furthermore, NALP1 is present in glandular epithelial structures such as stomach, gut, lung, and, surprisingly, in neurons and testis. In contrast to NALP1, NALP3 shows a more restricted tissue distribution with expression mainly in non-keratinizing epithelia in the oropharynx, esophagus, and ectocervix. Moreover, NALP3 expression is found in the urothelial layer in the bladder. Likewise, a difference in subcellular distribution between NALP1 and NALP3 is observed because NALP1 is localized mainly in the nucleus, whereas NALP3 is predominantly cytoplasmic. We propose that the presence of NALP3 in epithelial cells lining the oral and genital tracts allows the rapid sensing of invading pathogens, thereby triggering an innate immune response.

The inflammasome is a cytosolic protein complex regulating the activation of caspase-1, which cleaves the pro-inflammatory cytokines IL-1beta and IL-18 into their active form. The inflammasome is composed of a NACHT-, LRR- and pyrin (NALP) family member that acts as a sensor for danger signals and the adaptor protein apoptosis-associated speck-like protein containing a CARD domain (ASC), which allows the recruitment of caspase-1 in the complex. In the skin, exposure to contact sensitizers (CS) such as trinitro-chlorobenzene causes an immune response called contact hypersensitivity (CHS) or eczema. In this delayed-type hypersensitivity response, efficient priming of the adaptive immunity depends on the concomitant activation of the innate immune system, including IL-1beta/IL-18 activation in the skin. To determine if the inflammasome contributes to CHS, we have analyzed its capacity to react to CS in vitro and in vivo. We show here that key components of the inflammasome are present in human keratinocytes and that CS like trinitro-chlorobenzene induce caspase-1/ASC dependent IL-1beta and IL-18 processing and secretion. We also show that ASC- and NALP3-deficient mice display an impaired response to CS. These findings suggest that CS act as danger signals that activate the inflammasome in the skin, and reveal a new role of NALP3 and ASC as regulators of innate immunity in CHS.

High-risk human papillomaviruses (HPVs) have been proposed to be associated with a subset of head and neck cancers (HNSCCs). However, clear biological evidence linking HPVmediated oncogenesis to the development of HNSCC is hardly available. An important biological mechanism underlying HPV-mediated carcinogenesis is the inactivation of p53 by the HPV E6 oncoprotein. In the present study we investigated this biological relationship between HPV and HNSCC. In total 84 HNSCC tumors were analyzed for the presence of high-risk HPV nucleic acids by DNA polymerase chain reaction-enzyme immunoassay (PCR-EIA) and E6 reverse transcriptase (RT)-PCR as well as for the presence of mutations in the p53 gene. We found 20/84 HPV16 DNA-positive cases with one or more DNA assays, 10 of which were consistently positive with all assays. Only 9/20 cases showed E6 mRNA expression, indicative for viral activity. Only these nine E6 mRNA-positive cases all lacked a p53 mutation, whereas both the other HPV DNA-positive and HPV-DNA negative tumors showed p53 mutations in 36% and 63% of the cases, respectively. Moreover, only in lymph node metastases of HPV E6 mRNA-positive tumors both viral DNA and E6 mRNA were present. Our study provides strong biological evidence for a plausible etiological role of high-risk HPV in a subgroup of HNSCC. Analysis of E6 mRNA expression by RT-PCR or alternatively, semiquantitative analyses of the viral load, seem more reliable assays to assess HPV involvement in HNSCC than the very sensitive DNA PCR analyses used routinely. © 2001 Wiley-Liss, Inc. Key words: papillomavirus; head and neck cancer; squamous cell carcinoma; p53 mutations; E6 oncoproteinMucosotropic high-risk human papillomaviruses (HPVs), known to cause cervical and other anogenital cancers, have been proposed to play a role in the etiology of head and neck squamous cell carcinomas (HNSCCs). 1 The presence of high-risk HPV DNA in a subgroup of HNSCCs has supported this hypothesis. [2][3][4][5] Molecular studies have provided important data on the role and oncogenic mechanism of high-risk HPV in carcinogenesis. 6 -8 By expression of the viral oncoproteins E6 and E7, the virus dysregulates crucial cellular mechanisms such as the cell cycle and the apoptotic pathway. The E6 oncoprotein specifically inactivates wild-type p53, and the E7 oncoprotein inactivates Rb. In this way the high-risk HPV E6-mediated degradation of the p53 protein should be considered an alternative pathway for "classical" mutation to knock-out the p53 regulated pathways; it provides the biological basis to expect that tumors originating from HPV infection will show wild-type p53. Indeed, this general biological mechanism is supported by the finding that p53 mutations hardly occur in cervical carcinomas. 9,10 However, in most studies on head and neck cancer, HPV DNA presence and p53 mutations were overlapping, 2,11,12 an observation that gave rise to a long debate as to whether HPV is causally related to the development of a subset of these tumors.On the other hand, the inconsi...