Is the presence of Merkel cell polyomavirus and human papillomavirus DNA in keratinocyte cancers and precancers associated with HIV status? A case-control study.

The epidemiology and potential pathogenic roles of human papillomavirus (HPV) and Merkel cell polyomavirus (MCV) in keratinocyte cancers (KCs) arising in people living with HIV (PLWH) compared with HIV-negative individuals are poorly understood. These issues were investigated by a case-control study in which the presence of MCV and HPV DNA was identified by polymerase chain reaction in microdissected formalin-fixed paraffin-embedded tissue from PLWH and HIV-negative individuals. The samples comprised 190 cutaneous and genital KCs/precancers (actinic keratoses, n = 43; cutaneous squamous cell carcinoma (cSCC) in situ, n = 24; basal cell carcinoma, n = 78; cSCC, n = 34; penile carcinoma in situ, n = 9; penile SCC, n = 2 from 104 individuals (PLWH, n = 51; HIV-negative, n = 53). Almost one-quarter of samples were positive for MCV: this was not significantly associated with either HIV status (P = 0.06) nor lesion type. Overall, 36% (16/44) of MCV-positive lesions were coinfected with HPV; this was also not associated with HIV status. These findings indicate that if these viruses do contribute to the pathogenesis of KCs, it is likely to be independent of HIV status.

A Unique Panel of Patient-Derived Cutaneous Squamous Cell Carcinoma Cell Lines Provides a Preclinical Pathway for Therapeutic Testing.

BACKGROUND: Cutaneous squamous cell carcinoma (cSCC) incidence continues to rise with increasing morbidity and mortality, with limited treatment options for advanced disease. Future improvements in targeted therapy will rely on advances in genomic/transcriptomic understanding and the use of model systems for basic research. We describe here the panel of 16 primary and metastatic cSCC cell lines developed and characterised over the past three decades in our laboratory in order to provide such a resource for future preclinical research and drug screening. METHODS: Primary keratinocytes were isolated from cSCC tumours and metastases, and cell lines were established. These were characterised using short tandem repeat (STR) profiling and genotyped by whole exome sequencing. Multiple in vitro assays were performed to document their morphology, growth characteristics, migration and invasion characteristics, and in vivo xenograft growth. RESULTS: STR profiles of the cSCC lines allow the confirmation of their unique identity. Phylogenetic trees derived from exome sequence analysis of the matched primary and metastatic lines provide insight into the genetic basis of disease progression. The results of in vivo and in vitro analyses allow researchers to select suitable cell lines for specific experimentation. CONCLUSIONS: There are few well-characterised cSCC lines available for widespread preclinical experimentation and drug screening. The described cSCC cell line panel provides a critical tool for in vitro and in vivo experimentation.

HLA Immunogenotype Determines Persistent Human Papillomavirus Virus Infection in HIV-Infected Patients Receiving Antiretroviral Treatment.

A proportion of human immunodeficiency virus (HIV)-infected patients develop persistent, stigmatizing human papillomavirus (HPV)-related cutaneous and genital warts and anogenital (pre)cancer. This is the first study to investigate immunogenetic variations that might account for HPV susceptibility and the largest to date to categorize the HPV types associated with cutaneous warts in HIV-positive patients. The HLA class I and II allele distribution was analyzed in 49 antiretroviral (ART)-treated HIV-positive patients with persistent warts, 42 noninfected controls, and 46 HIV-positive controls. The allele HLA-B*44 was more frequently identified in HIV-positive patients with warts (P = .004); a susceptible haplotype (HLA-B*44, HLA-C*05; P = .001) and protective genes (HLA-DQB1*06; P = .03) may also contribute. Cutaneous wart biopsy specimens from HIV-positive patients harbored common wart types HPV27/57, the unusual wart type HPV7, and an excess of Betapapillomavirus types (P = .002), compared with wart specimens from noninfected controls. These findings suggest that HLA testing might assist in stratifying those patients in whom vaccination should be recommended.

Novel CARD11 Mutations in Human Cutaneous Squamous Cell Carcinoma Lead to Aberrant NF-κB Regulation.

NF-κB signaling plays a crucial role in regulating proliferation and differentiation in the epidermis. Alterations in the NF-κB pathway can lead to skin pathologies with a significant burden to human health such as psoriasis and cutaneous squamous cell carcinoma (cSCC). Caspase recruitment domain (CARD)-containing scaffold proteins are key regulators of NF-κB signaling by providing a link between membrane receptors and NF-κB transcriptional subunits. Mutations in the CARD family member, CARD14, have been identified in patients with the inflammatory skin diseases psoriasis and pityriasis rubra pilaris. Here, we describe that the gene coding for another CARD scaffold protein, CARD11, is mutated in more than 38% of 111 cSCCs, and show that novel variants outside of the coiled-coil domain lead to constitutively activated NF-κB signaling. CARD11 protein expression was detectable in normal skin and increased in all cSCCs tested. CARD11 mRNA levels were comparable with CARD14 in normal skin and CARD11 mRNA was increased in cSCC. In addition, we identified CARD11 mutations in peritumoral and sun-exposed skin, suggesting that CARD11-mediated alterations in NF-κB signaling may be an early event in the development of cSCC.

Exploiting FOXM1-orchestrated molecular network for early squamous cell carcinoma diagnosis and prognosis.

Histopathological discordance with molecular phenotype of many human cancers poses clinically challenging tasks for accurate cancer diagnosis, which impacts on treatment strategy and patient outcome. Hence, an objective, accurate and quantitative method is needed. A quantitative Malignancy Index Diagnostic System (qMIDS) was developed based on 14 FOXM1 (isoform B)-associated genes implicated in the regulation of the cell cycle, differentiation, ageing, genomic stability, epigenetic and stem cell renewal, and two reference genes. Their mRNA expression levels were translated via a prospectively designed algorithm, into a metric scoring system. Subjects from UK and Norway (n = 299) provided 359 head and neck tissue specimens. Diagnostic test performance was assessed using detection rate (DR) and false-positive rate (FPR). The median qMIDS scores were 1.3, 2.9 and 6.7 in healthy tissue, dysplasia and head and neck squamous cell carcinomas (HNSCC), respectively (UK prospective dataset, p<0.001); 1.4, 2.3 and 7.6 in unaffected, oral lichen planus, or HNSCC, respectively (Norwegian retrospective dataset with up to 19 years survival data, p<0.001). At a qMIDS cut-off of 4.0, DR was 94% and FPR was 3.2% (Norwegian dataset); and DR was 91% and FPR was 1.3% (UK dataset). We further demonstrated the transferability of qMIDS for diagnosing premalignant human vulva (n = 58) and skin (n = 21) SCCs, illustrating its potential clinical use for other cancer types. This study provided evidence that qMIDS was able to quantitatively diagnose and objectively stratify cancer aggressiveness. With further validation, qMIDS could enable early HNSCC detection and guide appropriate treatment. Early treatment intervention can lead to long-term reduction in healthcare costs and improve patient outcome.

Driver gene combinations dictate cutaneous squamous cell carcinoma disease continuum progression.

The molecular basis of disease progression from UV-induced precancerous actinic keratosis (AK) to malignant invasive cutaneous squamous cell carcinoma (cSCC) and potentially lethal metastatic disease remains unclear. DNA sequencing studies have revealed a massive mutational burden but have yet to illuminate mechanisms of disease progression. Here we perform RNAseq transcriptomic profiling of 110 patient samples representing normal sun-exposed skin, AK, primary and metastatic cSCC and reveal a disease continuum from a differentiated to a progenitor-like state. This is accompanied by the orchestrated suppression of master regulators of epidermal differentiation, dynamic modulation of the epidermal differentiation complex, remodelling of the immune landscape and an increase in the preponderance of tumour specific keratinocytes. Comparative systems analysis of human cSCC coupled with the generation of genetically engineered murine models reveal that combinatorial sequential inactivation of the tumour suppressor genes Tgfbr2, Trp53, and Notch1 coupled with activation of Ras signalling progressively drives cSCC progression along a differentiated to progenitor axis. Taken together we provide a comprehensive map of the cSCC disease continuum and reveal potentially actionable events that promote and accompany disease progression.

Metastatic cutaneous squamous cell carcinoma shows frequent deletion in the protein tyrosine phosphatase receptor Type D gene.

Cutaneous squamous cell carcinoma (cSCC) is the second most common form of nonmelanoma skin cancer (NMSC), and its incidence is increasing rapidly. Metastatic cSCC accounts for the majority of deaths associated with NMSC, but the genetic basis for cSCC progression remains poorly understood. A previous study identified small deletions (typically <1 Mb) in the protein tyrosine phosphatase receptor Type D (PTPRD) gene that segregated with more aggressive cSCC. To investigate the apparent association between deletion within PTPRD and cSCC metastasis, a series of 74 formalin-fixed paraffin-embedded tumors from 31 patients was analyzed using a custom Illumina 384 SNP microarray. Deletions were found in 37% of patients with metastatic cSCC and were strongly associated with metastatic tumors when compared to those that had not metastasized (p = 0.007). Subsequent mutation analysis revealed a higher mutation rate for PTPRD than has been reported in any other cancer type, with 37% of tumors harboring a somatic mutation. Conversely, bisulfite sequencing showed that methylation was not a mechanism of PTPRD disruption in cSCC. This is the first report to observe an association between deletion within PTPRD and metastatic disease and highlights the potential use of these deletions as a diagnostic biomarker for tumor progression. Combined with the high mutation rate observed in our study, PTPRD is one of the most commonly altered genes in cSCC and warrants further investigation to determine its significance for metastasis in other tumor types.

The Genomic Landscape of Actinic Keratosis.

Actinic keratoses (AKs) are lesions of epidermal keratinocyte dysplasia and are precursors for invasive cutaneous squamous cell carcinoma (cSCC). Identifying the specific genomic alterations driving the progression from normal skin to skin with AK to skin with invasive cSCC is challenging because of the massive UVR-induced mutational burden characteristic at all stages of this progression. In this study, we report the largest AK whole-exome sequencing study to date and perform a mutational signature and candidate driver gene analysis on these lesions. We demonstrate in 37 AKs from both immunosuppressed and immunocompetent patients that there are significant similarities between AKs and cSCC in terms of mutational burden, copy number alterations, mutational signatures, and patterns of driver gene mutations. We identify 44 significantly mutated AK driver genes and confirm that these genes are similarly altered in cSCC. We identify azathioprine mutational signature in all AKs from patients exposed to the drug, providing further evidence for its role in keratinocyte carcinogenesis. cSCCs differ from AKs in having higher levels of intrasample heterogeneity. Alterations in signaling pathways also differ, with immune-related signaling and TGFß signaling significantly more mutated in cSCC. Integrating our findings with independent gene expression datasets confirms that dysregulated TGFß signaling may represent an important event in AK‒cSCC progression.

Evaluation of a novel broad-spectrum PCR-multiplex genotyping assay for identification of cutaneous wart-associated human papillomavirus types.

A large number of human papillomavirus (HPV) types, distributed over five papillomavirus genera, are detectable in the skin. HPV types belonging to the alpha, gamma, and mu genera have been detected in cutaneous warts. A state-of-the-art HPV genotyping assay for these cutaneous wart-associated HPV types does not exist although warts constitute a highly prevalent skin condition, especially in children (33%) and organ transplant recipients (45%). Cutaneous warts are again the focus of attention as their clinical relevance rises with the increasing number of chronically immunosuppressed patients. The objective of this study was to develop and evaluate a DNA-based genotyping system for all known cutaneous wart-related HPV types using PCR and Luminex xMAP technology. The broad-spectrum PCR amplified DNA of all known wart-associated HPV types from the genera alpha (HPVs 2, 3, 7, 10, 27, 28, 29, 40, 43, 57, 77, 91, and 94), gamma (HPVs 4, 65, 95, 48, 50, 60, and 88), mu (HPVs 1 and 63), and nu (HPV41). The probes were evaluated using plasmid HPV DNA and a panel of 45 previously characterized cutaneous wart biopsy specimens showing high specificity. HPV was also identified in 96% of 100 swabs from nongenital cutaneous warts. HPV types 1, 2, 27, and 57 were the most prevalent HPV types detected in 89% of the swabs. In conclusion, this Luminex-based genotyping system identifies all known cutaneous wart HPV types including phylogenetically related types, is highly HPV type specific, and is suitable for large-scale epidemiological studies.

Epigenetic Regulation of iASPP-p63 Feedback Loop in Cutaneous Squamous Cell Carcinoma.

Keratinocyte skin cancer, comprising cutaneous squamous (cSCC) and basal cell carcinoma, is the most common malignancy in the United Kingdom. P53 is frequently mutated in cSCC. iASPP is a key inhibitor of p53 and NF-κB signaling pathways and has been documented as highly expressed in several types of human cancer. We have previously identified an autoregulatory feedback loop between iASPP and p63, which is critical in epidermal homeostasis. We hypothesized a potential role for dysregulation of this axis in the pathogenesis of keratinocyte malignancies. Immunostaining of 116 cSCC clinical samples revealed increased iASPP and ΔNp63 expression, but also highlighted a significant alteration of iASPP cellular localization, with consequent deregulation of its function. Expression patterns, functionality, and gene and microRNA expression analysis were further investigated in 10 cSCC cell lines. Our data suggest that while direct effects of iASPP and p63 upon each other's expression are maintained in cSCC, epigenetic dysregulation of the feedback loop occurs at the microRNA level by a previously unreported mechanism controlling p63 expression. We demonstrate that this autoregulatory feedback loop controls cell migration in cSCC by blocking epithelial-mesenchymal transition and promoting proliferation, and provides future directions for clinical biomarker and therapeutic target discovery in cutaneous SCC.

The Role of Human Papillomaviruses and Polyomaviruses in BRAF-Inhibitor Induced Cutaneous Squamous Cell Carcinoma and Benign Squamoproliferative Lesions.

Background: Human papillomavirus (HPV) has long been proposed as a cofactor in the pathogenesis of cutaneous squamous cell carcinoma (cSCC). More recently, the striking clinico-pathological features of cSCCs that complicate treatment of metastatic melanoma with inhibitors targeting BRAF mutations (BRAFi) has prompted speculation concerning a pathogenic role for oncogenic viruses. Here, we investigate HPV and human polyomaviruses (HPyV) and correlate with clinical, histologic, and genetic features in BRAFi-associated cSCC. Materials and Methods: Patients receiving BRAFi treatment were recruited at Barts Health NHS Trust. HPV DNA was detected in microdissected frozen samples using reverse line probe technology and degenerate and nested PCR. HPV immunohistochemistry was performed in a subset of samples. Quantitative PCR was performed to determine the presence and viral load of HPyVs with affinity for the skin (HPyV6, HPyV7, HPyV9, MCPyV, and TSPyV). These data were correlated with previous genetic mutational analysis of H, K and NRAS, NOTCH1/2, TP53, CDKN2A, CARD11, CREBBP, TGFBR1/2. Chromosomal aberrations were profiled using single nucleotide polymorphism (SNP) arrays. Results: Forty-five skin lesions from seven patients treated with single agent vemurafenib in 2012-2013 were analyzed: 12 cSCC, 19 viral warts (VW), 2 actinic keratosis (AK), 5 verrucous keratosis/other squamoproliferative (VK/SP) lesions, one melanocytic lesion and 6 normal skin samples. Significant histologic features of viral infection were seen in 10/12 (83%) cSCC. HPV DNA was detected in 18/19 (95%) VW/SP, 9/12 (75%) cSCC, 4/5 (80%) SP, and 3/6 (50%) normal skin samples and in 1/12 cases assessed by immunohistochemistry. HPyV was co-detected in 22/30 (73%) of samples, usually at low viral load, with MCPyV and HPyV7 the most common. SNP arrays confirmed low levels of chromosomal abnormality and there was no significant correlation between HPV or HPyV detection and individual gene mutations or overall mutational burden. Conclusion: Despite supportive clinicopathologic evidence, the role for HPV and HPyV infection in the pathogenesis of BRAFi-induced squamoproliferative lesions remains uncertain. Synergistic oncogenic mechanisms are plausible although speculative. Nonetheless, with the prospect of a significant increase in the adjuvant use of these drugs, further research is justified and may provide insight into the pathogenesis of other BRAFi-associated malignancies.

Reduced SMAD2/3 activation independently predicts increased depth of human cutaneous squamous cell carcinoma.

The incidence of cutaneous squamous cell carcinoma (cSCC) is rising. Whilst the majority are cured surgically, aggressive metastatic cSCC carry a poor prognosis. Inactivating mutations in transforming growth factor beta (TGF-ß) receptors have been identified amongst genetic drivers of sporadic tumours and murine models of cSCC, suggesting a tumour suppressor function for TGF-ß in normal skin. However, paradoxically, TGF-ß acts as a tumour promoter in some murine model systems. Few studies have analysed the role of TGF-ß/activin signalling in human normal skin, hyper-proliferative skin disorders and cSCC. Antibodies recognising phospho-SMAD proteins which are activated during canonical TGF-ß/activin signalling were validated for use in immunohistochemistry. A tissue microarray comprising FFPE lesional and perilesional tissue from human primary invasive cSCC (n=238), cSCC in-situ (n=2) and keratocanthoma (n=9) were analysed in comparison with tissues from normal human scalp (n=10). Phosphorylated SMAD2 and SMAD3 were detected in normal interfollicular epidermal keratinocytes and were also highly localised to inner root sheath, matrix cells and Keratin 15 positive cells. Lesional cSCC tissue had significantly reduced activated SMAD2/3 compared to perilesional tissue, consistent with a tumour suppressor role for SMAD2/3 activators in cSCC. Increased cSCC tumour thickness inversely correlated with the presence of phospho-SMADs in tumour tissue suggesting that a reduction in canonical TGF-ß/activin signalling may be associated with disease progression.

The genomic landscape of cutaneous SCC reveals drivers and a novel azathioprine associated mutational signature.

Cutaneous squamous cell carcinoma (cSCC) has a high tumour mutational burden (50 mutations per megabase DNA pair). Here, we combine whole-exome analyses from 40 primary cSCC tumours, comprising 20 well-differentiated and 20 moderately/poorly differentiated tumours, with accompanying clinical data from a longitudinal study of immunosuppressed and immunocompetent patients and integrate this analysis with independent gene expression studies. We identify commonly mutated genes, copy number changes and altered pathways and processes. Comparisons with tumour differentiation status suggest events which may drive disease progression. Mutational signature analysis reveals the presence of a novel signature (signature 32), whose incidence correlates with chronic exposure to the immunosuppressive drug azathioprine. Characterisation of a panel of 15 cSCC tumour-derived cell lines reveals that they accurately reflect the mutational signatures and genomic alterations of primary tumours and provide a valuable resource for the validation of tumour drivers and therapeutic targets.

Whole-Exome Sequencing Validates a Preclinical Mouse Model for the Prevention and Treatment of Cutaneous Squamous Cell Carcinoma.

Cutaneous squamous cell carcinomas (cSCC) are among the most common and highly mutated human malignancies. Solar UV radiation is the major factor in the etiology of cSCC. Whole-exome sequencing of 18 microdissected tumor samples (cases) derived from SKH-1 hairless mice that had been chronically exposed to solar-simulated UV (SSUV) radiation showed a median point mutation (SNP) rate of 155 per Mb. The majority (78.6%) of the SNPs are C.G>T.A transitions, a characteristic UVR-induced mutational signature. Direct comparison with human cSCC cases showed high overlap in terms of both frequency and type of SNP mutations. Mutations in Trp53 were detected in 15 of 18 (83%) cases, with 20 of 21 SNP mutations located in the protein DNA-binding domain. Strikingly, multiple nonsynonymous SNP mutations in genes encoding Notch family members (Notch1-4) were present in 10 of 18 (55%) cases. The histopathologic spectrum of the mouse cSCC that develops in this model resembles very closely the spectrum of human cSCC. We conclude that the mouse SSUV cSCCs accurately represent the histopathologic and mutational spectra of the most prevalent tumor suppressors of human cSCC, validating the use of this preclinical model for the prevention and treatment of human cSCC. Cancer Prev Res; 10(1); 67-75. ©2016 AACR.

Genomic analysis of atypical fibroxanthoma.

Atypical fibroxanthoma (AFX), is a rare type of skin cancer affecting older individuals with sun damaged skin. Since there is limited genomic information about AFX, our study seeks to improve the understanding of AFX through whole-exome and RNA sequencing of 8 matched tumor-normal samples. AFX is a highly mutated malignancy with recurrent mutations in a number of genes, including COL11A1, ERBB4, CSMD3, and FAT1. The majority of mutations identified were UV signature (C>T in dipyrimidines). We observed deletion of chromosomal segments on chr9p and chr13q, including tumor suppressor genes such as KANK1 and CDKN2A, but no gene fusions were found. Gene expression profiling revealed several biological pathways that are upregulated in AFX, including tumor associated macrophage response, GPCR signaling, and epithelial to mesenchymal transition (EMT). To further investigate the presence of EMT in AFX, we conducted a gene expression meta-analysis that incorporated RNA-seq data from dermal fibroblasts and keratinocytes. Ours is the first study to employ high throughput sequencing for molecular profiling of AFX. These data provide valuable insights to inform models of carcinogenesis and additional research towards tumor-directed therapy.

Are keratoacanthomas variants of squamous cell carcinomas? A comparison of chromosomal aberrations by comparative genomic hybridization.

Keratoacanthoma (KA) is a benign keratinocytic neoplasm that usually presents as a solitary nodule on sun-exposed areas, develops within 6-8 weeks and spontaneously regresses after 3-6 months. KAs share features such as infiltration and cytological atypia with squamous cell carcinomas (SCCs). Furthermore, there are reports of KAs that have metastasized, invoking the question of whether or not KA is a variant of SCC. To date no reported criteria are sensitive enough to discriminate reliably between KA and SCC, and consequently there is a clinical need for discriminating markers. We screened fresh frozen material from 132 KAs and 37 SCCs for gross chromosomal aberrations by using comparative genomic hybridization (CGH). Forty-nine KAs (37.1%) and 31 SCCs (83.7%) showed genomic aberrations, indicating a higher degree of chromosomal instability in SCCs. Gains of chromosomal material from 1p, 14q, 16q, 20q, and losses from 4p were seen significantly more frequently in SCCs compared with KAs (P-values 0.0033, 0.0198, 0.0301, 0.0017, and 0.0070), whereas loss from 9p was seen significantly more frequently in KAs (P-value 0.0434). The patterns of recurrent aberrations were also different in the two types of neoplasms, pointing to different genetic mechanisms involved in their developments.

Inactivation of TGFß receptors in stem cells drives cutaneous squamous cell carcinoma.

Melanoma patients treated with oncogenic BRAF inhibitors can develop cutaneous squamous cell carcinoma (cSCC) within weeks of treatment, driven by paradoxical RAS/RAF/MAPK pathway activation. Here we identify frequent TGFBR1 and TGFBR2 mutations in human vemurafenib-induced skin lesions and in sporadic cSCC. Functional analysis reveals these mutations ablate canonical TGFß Smad signalling, which is localized to bulge stem cells in both normal human and murine skin. MAPK pathway hyperactivation (through Braf(V600E) or Kras(G12D) knockin) and TGFß signalling ablation (through Tgfbr1 deletion) in LGR5(+ve) stem cells enables rapid cSCC development in the mouse. Mutation of Tp53 (which is commonly mutated in sporadic cSCC) coupled with Tgfbr1 deletion in LGR5(+ve) cells also results in cSCC development. These findings indicate that LGR5(+ve) stem cells may act as cells of origin for cSCC, and that RAS/RAF/MAPK pathway hyperactivation or Tp53 mutation, coupled with loss of TGFß signalling, are driving events of skin tumorigenesis.

Human papillomavirus-DNA loads in actinic keratoses exceed those in non-melanoma skin cancers.

Recent studies suggest a role of cutaneous human papillomaviruses (HPV) in non-melanoma skin cancer (NMSC) development. In this study viral DNA loads of six frequent HPV types were determined by quantitative, type-specific real-time-PCR (Q-PCR) in actinic keratoses (AK, n=26), NMSC (n=31), perilesional tissue (n=22), and metastases of squamous cell carcinomas (SCC) (n=8) which were previously shown to be positive for HPV5, 8, 15, 20, 24, or 36. HPV-DNA loads in AK, (partially microdissected) NMSC, and perilesional skin ranged between one HPV-DNA copy per 0.02 and 14,200 cell equivalents (median: 1 HPV-DNA copy per 344 cell equivalents; n=48). In 32 of the 79 HPV-positive skin biopsies and in seven of the eight metastases viral loads were even below the detection limit of Q-PCR. Low viral loads in NMSC were confirmed by in situ-hybridization showing only a few HPV-DNA-positive nuclei per section. Viral loads in SCC, basal cell carcinomas, and perilesional tissue were similar. But, viral loads found in AK were significantly higher than in SCC (p=0.035). Our data suggest that persistence of HPV is not necessary for the maintenance of the malignant phenotype of individual NMSC cells. Although a passenger state cannot be excluded, the data are compatible with a carcinogenic role of HPV in early steps of tumor development.

Human papillomavirus gene expression in cutaneous squamous cell carcinomas from immunosuppressed and immunocompetent individuals.

Epidermodysplasia verruciformis (EV)-type human papillomavirus (HPV) DNA have been detected by PCR in squamous cell carcinomas (SCC) from both organ transplant recipients (OTR) and immunocompetent individuals. Their role in skin cancer remains unclear, and previous studies have not addressed whether the viruses are transcriptionally active. We have used in situ hybridization to investigate the transcriptional activity and DNA localization of HPV. EV-HPV gene transcripts were demonstrated in four of 11 (36%) OTR SCC, one of two (50%) IC SCC, and one of five (20%) OTR warts positive by PCR. Viral DNA co-localized with E2/E4 early region gene transcripts in the middle or upper epidermal layers. Non-EV cutaneous HPV gene transcripts were demonstrated in one of five (20%) OTR SCC and four of 10 (40%) OTR warts. In mixed infections transcripts for both types were detected in two of six (33%) cases. Our results provide evidence of EV-HPV gene expression in SCC; although only a proportion of tumors were positive, the similarly low transcriptional activity in warts suggests this is an underestimate. These observations, together with emerging epidemiological and functional data, provide further reason to focus on the contribution of EV-HPV types to the pathogenesis of cutaneous SCC.