Development of multiple pigmented viral plaques and squamous cell carcinomas in a dog infected by a novel papillomavirus

Clinical, histopathological, and molecular characterization of canine pigmented viral plaques

Canine pigmented viral plaques (PVPs) are proliferative epidermal lesions caused by canine papillomaviruses (CPVs). Although the lesions are benign, neoplastic transformation has been reported. Cases reported in the literature are few and mainly focused on genome sequencing. The aim of this study was to collect data on the epidemiology, clinicopathological features, and genotyping of PVPs. Fifty-five canine PVPs were retrospectively retrieved and histologically evaluated. Follow-up was available for 33 cases. The median age was 6.5 years and pugs were the most represented breed (25%). There were 4 clinical presentations: a single lesion (24%), multiple lesions (75%) in one (41%) or different sites (34%), and generalized lesions all over the body (24%). The abdomen and axillae were the most common sites. In single lesions, no recurrence was observed after conventional surgery, whereas different medical treatments reported for multiple lesions were not successful. Spontaneous regression was reported in 3 cases. Neoplasia in contiguity with PVPs was seen in 5 of 55 lesions (9%), and 1 dog was euthanized due to invasive squamous cell carcinoma (SCC). The most useful histopathological features for diagnosis were scalloped profile, epidermal spikes, hypergranulosis, and hyperpigmentation. L1 immunolabeling was present in 14 of 16 cases (87%). Sequencing revealed that 10 of 16 cases were associated with CPV-9 (71%), 2 cases were associated with CPV-4 (14%), and 2 cases were associated with CPV-8 (14%). In conclusion, this represents a large cohort study on canine PVPs reporting data on clinicopathological features, therapy, outcome, and the type of CPV involved for the first time in Italy.

Exploring the link between viruses and cancer in companion animals: a comprehensive and comparative analysis

Currently, it is estimated that 15% of human neoplasms globally are caused by infectious agents, with new evidence emerging continuously. Multiple agents have been implicated in various forms of neoplasia, with viruses as the most frequent. In recent years, investigation on viral mechanisms underlying tumoral transformation in cancer development and progression are in the spotlight, both in human and veterinary oncology. Oncogenic viruses in veterinary medicine are of primary importance not only as original pathogens of pets, but also in the view of pets as models of human malignancies. Hence, this work will provide an overview of the main oncogenic viruses of companion animals, with brief notes of comparative medicine.

Canine oral squamous cell carcinoma as a spontaneous, translational model for radiation and immunology research

Introduction

Improving outcomes for oral squamous cell carcinoma (OSCC) patients has been hindered by a lack of effective predictive animal models. Spontaneously occurring canine OSCC could help fill this gap. The objective of this study was to characterize the immune landscape of canine OSCC to advance understanding of how dogs could serve as a surrogate for human OSCC.

Methods/Results

Canine OSCC contains a heterogenous tumor immune microenvironment. CD3+ T cells were the predominant tumor infiltrating immune cell population; however, there was a wide range CD3+ T cell density across samples. The most common CD3+ T cell micro-anatomical distribution was defined as "pre-existing immunity", but the remaining 20% of tumors were characterized as "immunologically ignorant" or "excluded infiltrates" patterns. When compared to normal oral mucosa, the tumor gene expression pattern suggests that canine OSCC microenvironment is highly inflamed and characterized by the presence of an anti-tumor immune response dominated by cytotoxic\effector T cells and NK cells (CD8a, GZMA, OX40, and HLA-A); however, overexpression of genes associated with effector T cell exhaustion and microenvironmental immunosuppression was also identified (PD-1, LAG3, CXCL2). Correlations between CD3+ T cell density and immune gene expression revealed key genes associated with cytotoxic anti-tumor T cell responses (GZMA, GZMB, PRF1), co-stimulation of T cells (CD27, CD28, ICOS), and other immune processes, including Type I IFN response (TNF, TNFSF10), and T cell exhaustion (CTLA4, PD-1). CD3+ T cell density in canine OSCC was significantly correlated with a cytolytic activity score (mean PRF1 and GZMA expression), suggestive of active effector CD8 T cell function. CD204+ macrophages were the second most abundant tumor infiltrating immune cell, and when comparing to normal oral mucosa, two differently expressed genes linked to tumor associated macrophages and myeloid derived suppressor cells (MDSC) were identified: CXCL2, CD70. Overexpression of CXCL2 was also identified in canine OSCC "T cell-high" tumors compared to "T cell-low" tumors.

Discussion

This study identified actionable immunotherapy targets which could inform future comparative oncology trials in canine OSCC: CTLA-4, PD-1, CXCL2. These data provide a good first step towards utilizing spontaneous canine OSCC as a comparative model for human OSCC radiation and immuno-oncology research.

Papillomaviral skin diseases of humans, dogs, cats and horses: A comparative review. Part 2: Pre-neoplastic and neoplastic diseases

Papillomaviruses (PVs) are well recognized to cause pre-neoplastic and neoplastic diseases in humans. Similarly, there is increasing evidence that PVs play a significant role in the development of pre-neoplastic and neoplastic diseases of the haired skin of dogs and cats, and the mucosa of horses. As the mechanisms by which PVs cause neoplasia are well studied in humans, it is valuable to compare the PV-induced neoplasms of humans with similar PV-associated neoplasms in the companion animal species. In the second part of this comparative review, the pre-neoplastic and neoplastic diseases thought to be caused by PVs in humans, dogs, cats, and horses are described. This includes PV-induced cutaneous plaques, cutaneous squamous cell carcinomas (SCCs) and mucosal SCCs within the four species. The review concludes with a discussion about the potential use of vaccines to prevent PV-induced diseases of dogs, cats, and horses.

Extensive progressive pigmented viral plaques in a Chihuahua dog

Extensive exophytic pigmented viral plaques developed on a Chihuahua dog causing pruritus and discomfort. Neither the medical treatments used nor a papillomavirus vaccine resulted in clinical improvement. Laser surgery removed some plaques, yet others developed. This case illustrates the difficulty in treating viral plaques and the progressive nature of this disease.

Alimentary squamous cell carcinoma in psittacines: 12 cases and review of the literature

Squamous cell carcinoma (SCC), which is a neoplasm that usually arises from the integument, is reported uncommonly in pet birds. Only a few reports of SCCs in the alimentary tract of birds, including psittacines, have been published, and a detailed description of the pathology is not available in the literature. We present here 12 cases of alimentary SCC in psittacines. The average age of the birds was 22.2 y (range: 15-29 y), and affected species included 4 Amazon parrots (Amazona sp.), 3 cockatiels (Nymphicus hollandicus), 3 macaws (Ara sp.), 1 conure (Eupsittula sp.), and 1 Senegal parrot (Poicephalus sp.). Frequent clinical complaints included regurgitation, dysphagia, dyspnea, lethargy, and/or weight loss. SCC primarily affected the oral cavity in 6 of 12 cases, the crop alone in 2 of 12 cases, the crop and esophagus in 1 of 12 cases, the proventriculus alone in 1 of 12 cases, and the crop, esophagus, and proventriculus in 2 of 12 cases. Histologically, alimentary SCCs were locally invasive and often resulted in mucosal ulceration. Although there were no metastases in any of our cases, poor clinical outcomes were frequent and associated most commonly with complete effacement of the alimentary segment and severe inflammation with opportunistic bacterial infection. Our review of the literature records commonly affected species, variability of gross presentations and clinical signs, plausible etiologies, and current diagnostic developments.

Development of multiple cutaneous and follicular neoplasms associated with canine papillomavirus type 3 in a dog

A 12-year-old spayed English pointer dog developed multiple skin lesions including pigmented viral plaques, basal cell carcinomas, squamous cell carcinomas and trichoblastomas. Canine papillomavirus type 3 was detected in multiple lesions suggesting common aetiology.

Canine papillomavirus type 16 associated to squamous cell carcinoma in a dog: virological and pathological findings

Papillomaviruses (PVs) are circular double-stranded DNA virus belonging to Papillomaviridae family. During the infection cycle, PVs translate proteins that can influence cell growth and differentiation, leading to epidermal hyperplasia and papillomas (warts) or malignant neoplasms. Canis familiaris papillomaviruses (CPVs) have been associated with different lesions, such as oral and cutaneous papillomatosis, pigmented plaques, and squamous cell carcinomas (SCCs). Here, we report a clinical case of a mixed bred female dog with pigmented plaques induced by CPV16 (Chipapillomavirus 2) that progressed to in situ and invasive SCCs. Gross and histological findings were characterized, and the lesions were mainly observed in ventral abdominal region and medial face of the limbs. In situ hybridization (ISH) revealed strong nuclear hybridization signals in the neoplastic epithelial cells, as well as in the keratinocytes and koilocytes of the pigmented viral plaques. The full genome of the CPV16 recovered directly from the lesions was characterized, and the phylogenetic relationships were determined. The identification of oncoprotein genes (E5, E6, and E7) by high throughput sequencing (HTS) and their expected domains are suggestive of the malignant transformation by CPV16.

Morphological features of coilocytary atypism of squamous papillomas of dogs

Coilocytic atypism of tumors of epithelial origin is considered as a marker of HPV infection, regardless of the type of neoplasm, which is a clinical manifestation of papillomatosis. Many neoplasms in dogs are diagnosed depending on the identification of specific cellular and tissue atypism, which underlies the histological diagnosis. According to the recent studies, the following types of neoplasm can be distinguished depending on the taxonomic affiliation of HPV: papillomas of various localization, cancerous epidermodysplasia verruciformis, pigment affects (including plaque), inverted and squamous papillomas, squamous cell carcinomas. Histological studies are an affordable diagnostic method that allows studying the morphological features of coylocytary atypism of squamous papillomas of dogs. Squamous cell papillomas in dogs have a number of morphological and cytological features, due to the predominance of the keratinization process. In this case, the process of differentiation of epithelial cells is consistent and all layers typical of the skin of dogs are distinguished. The corneal layer prevails over all the described layers, the activity of the cells of the basal layer is noted. Coilocytes are localized in a spinous and granular layer, but depending on their location, they have distinctive morphological and quantitative characteristics. Despite the polymorphism of the manifestation of coylocytary atypism in animals within the limits of specific affects, as well as depending on the type of neoplasm, there are no common morphological criteria for evaluating coylocytosis depending on oncogenesis. It was noted that the morphological and quantitative characteristics of coilocytes depend on their location, while they have a morphology described by many researchers, including in various animal species.

Papillomavirus DNA is not Amplifiable from Bladder, Lung, or Mammary Gland Cancers in Dogs or Cats

Simple Summary

Papillomaviruses (PVs) are well established to cause genital and oral cancer in humans. Additionally, some evidence suggests that these viruses may also have a role in the development of human lung, breast, and bladder cancer. Recent studies have revealed that PVs can influence the development of some cancers in cats and, less frequently, in dogs. In the present study, 47 lung, mammary gland, and bladder cancers in dogs and 25 cancers in cats were evaluated for evidence of any role PVs may have in cancer development. Histology did not reveal any lesions suggestive of PV infection, and no PV DNA was amplified from any cancer. Therefore, these findings suggest that PVs do not frequently infect these tissues and are therefore unlikely to be significant factors in the development of lung, mammary gland, or bladder cancer in either dogs or cats.

Abstract

Papillomaviruses (PVs) cause around 5% of all human cancers, including most cervical cancers and around a quarter of all oral cancers. Additionally, some studies have suggested that PVs could cause a proportion of human lung, breast, and bladder cancers. As PVs have been associated with skin cancer in cats and, more rarely, dogs, it was hypothesized that these viruses could also contribute to epithelial cancers of the lung, mammary gland, and bladder of dogs and cats. Formalin-fixed paraffin-embedded samples of 47 canine and 25 feline cancers were examined histologically for evidence of PV infection. Additionally, three sets of consensus PCR primers were used to amplify PV DNA from the samples. No histological evidence of PV infection was visible in any of the cancers. DNA from a bovine PV type was amplified from one sample, while two different samples were found to contain human PV DNA. However, these were considered to be contaminants, and no canine or feline PV types were amplified from any of the cancers. These results suggest that PVs do not frequently infect the lung, mammary gland, or bladder of dogs and cats and therefore are unlikely to be significant factors in the development of cancers in these tissues.

Viral genome integration of canine papillomavirus 16

Papillomaviruses infect humans and animals, most often causing benign proliferations on skin or mucosal surfaces. Rarely, these infections persist and progress to cancer. In humans, this transformation most often occurs with high-risk papillomaviruses, where viral integration is a critical event in carcinogenesis. The first aim of this study was to sequence the viral genome of canine papillomavirus (CPV) 16 from a pigmented viral plaque that progressed to metastatic squamous cell carcinoma in a dog. The second aim was to characterize multiple viral genomic deletions and translocations as well as host integration sites. The full viral genome was identified using a combination of PCR and high throughput sequencing. CPV16 is most closely related to chipapillomaviruses CPV4, CPV9, and CPV12 and we propose CPV16 be classified as a chipapillomavirus. Assembly of the full viral genome enabled identification of deletion of portions of the E1 and E2/E4 genes and two viral translocations within the squamous cell carcinoma. Genome walking was performed which identified four sites of viral integration into the host genome. This is the first description of integration of a canine papillomavirus into the host genome, raising the possibility that CPV16 may be a potential canine high-risk papillomavirus type.

Malignant transformation of canine oral papillomavirus (CPV1)-associated papillomas in dogs: An emerging concern?

Canine oral papillomavirus (CPV1, also known as COPV), the most common cause of non-neoplastic papillomas, has not been shown to cause squamous cell carcinomas (SCC). Furthermore, malignant transformation of benign papillomas to SCC has only been reported in a single group of dogs with severe combined immunodeficiency infected with CPV2. Here, we report a series of 7 dogs with benign CPV1-associated papillomas with histologic evidence of CPV1 causing malignant transformation to carcinoma in situ and ultimately SCC. Expression of p53 and p16 proteins in CPV1-infected cells within the benign papillomas and lesions that progressed into SCC also supported an association between papillomavirus and malignant transformation. Moreover, our retrospective analysis indicated that while there have been increased numbers of viral papillomas with malignant transformation, the number of annually diagnosed canine viral papillomas has remained constant over the past decade in our laboratory. We speculate that either an altered host immunity from increased usage of immunosuppressive drugs or changing environmental factors, e.g. increase exposure to UV radiation, may cause an increased oncogenic potential of this “low-risk” virus. This study aims to raise awareness of the malignant potential of CPV1 and to encourage further investigations into the cause of this suspected change in its oncogenic potential.

Detection of Felis catus papillomavirus type 2 within multicentric basosquamous carcinoma in a domestic cat

A 12-year-old neutered male domestic shorthair cat was presented with a 3-year history of multiple nonpruritic, ulcerated, plaque-like skin lesions but no other clinical signs. A systemic examination revealed mild lymphadenopathy. Histopathologic analysis of the skin lesions revealed multicentric basosquamous carcinoma (BSC). Immunohistochemical analysis, PCR, and sequencing detected Felis catus papillomavirus type 2 (FcaPV-2) within the tumors. As BSC is rare in cats, clinical behavior has not been established. To our knowledge, this is the first case report to demonstrate detection of FcaPV-2 within a BSC in a domestic cat.

Progressive cutaneous viral pigmented plaques in three Hungarian Vizslas and the response of lesions to topical tigilanol tiglate gel

Cutaneous pigmented viral plaques is a disorder of epidermal growth caused by canine papillomavirus type 4 (CPV-4). There is currently no standard of care for managing this condition and it has not been reported in the Hungarian Vizsla. This case series documents the clinical features of canine pigmented viral plaques in Hungarian Vizsla dogs and the treatment of a severe case using a novel topical agent tigilanol tiglate (EBC-46). A 4-year-old spayed Hungarian Vizsla in Australia was presented for multiple cutaneous pigmented plaques extending from the ventral cervical region. Lesions were neither painful nor pruritic. The number and size of these sessile plaques increased over time, with the largest lesions eventually taking on an exophytic (wart-like) appearance. These lesions did not affect the dog's wellbeing. Two much less severe cases in a 5-year-old Vizsla from the UK and a 7-year-old Vizsla from New Zealand were also diagnosed. Histology was consistent with papillomavirus-induced pigmented plaques and CPV-4 DNA sequences were amplified from paraffin-embedded formalin-fixed tissue using the polymerase chain reaction from the most severely affected patient. Topical imiquimod was ineffective although used for only a short time. Two topical applications of novel anti-neoplastic diterpene ester tigilanol tiglate as a gel, 9 days apart, greatly reduced the size and number of lesions in a limited portion of skin treated, over the lateral hock. While CPV-4 has been previously reported to cause pigmented plaques, most commonly on pug dogs, but sporadically on other breeds, this is the first report of this virus causing plaques in Hungarian Vizslas. The cases illustrate some of the difficulties in diagnosing papillomavirus-induced disease in dogs, especially in its early stages. Topical tigilanol tiglate is a potentially useful topical therapy for this viral-induced disorder of cell growth and represents a treatment deserving of further investigation.

Papillomaviruses in dogs and cats

Papillomaviruses (PVs) cause disease in both dogs and cats. In dogs, PVs are thought to cause oral papillomatosis, cutaneous papillomas and canine viral pigmented plaques, whereas PVs have been rarely associated with the development of oral and cutaneous squamous cell carcinomas in this species. In cats, PVs are currently thought to cause oral papillomas, feline viral plaques, Bowenoid in situ carcinomas and feline sarcoids. Furthermore, there is increasing evidence that PVs may also be a cause of cutaneous squamous cell carcinomas and basal cell carcinomas in cats. These diseases are discussed in this review. Additionally, there is a brief overview of PV biology, including how these viruses cause disease. Diagnostic techniques and possible methods to prevent PV infection are also discussed.

p16 Immunostaining of Canine Squamous Cell Carcinomas Is Not Associated with Papillomaviral DNA

While papillomavirus (PVs) are an established cause of human cancer, few reports have supported a relationship between PV and canine squamous cell carcinomas (SCCs). Human oncogenic PVs lead to an increased expression of the p16 tumor suppressor protein, and the latter can be demonstrated immunohistochemically to support a likely causal relationship between tumor and PV infection. In the present study, archive samples of canine SCC from different anatomical locations were tested by polymerase chain reaction for the presence of PV DNA and by p16 immunohistochemistry. The aims were to investigate the relationship between p16 expression and presence of PV DNA, in order to assess the utility of p16 overexpression as a biomarker of PV infection in canine SCC. A total of 52 SCCs were included. Nine cases (17.3%) showed moderate p16 immunoreactivity, with no association with tumor degree of differentiation, histotype or mitotic activity. The canPVf/FAP64 primers amplified Canis familiaris PV-1 DNA from 3 out of 52 tumors (5.8%), one cutaneous, one oral and one tonsillar SCC. There was no association between PV presence and p16 immunostaining. These results do not support a significant role of PVs in the development of canine SCCs. Additionally, PV infection was apparently not the cause of the p16 immunostaining observed in a subset of canine SCCs. A better awareness of p16 level of expression and cellular function in canine cancer may help to define its diagnostic and prognostic role.

Complete genome sequence of canine papillomavirus type 16

Papillomaviruses are epitheliotropic, circular, double-stranded DNA viruses within the family Papillomaviridae that are associated with benign and malignant tumors in humans and animals. We report the complete genome sequence of canine papillomavirus type 16 identified within multiple pigmented cutaneous plaques and squamous cell carcinoma from an intact female Basenji dog.

Papillomaviral DNA sequences are not amplifiable from canine subungual squamous cell carcinomas

AIM

To determine if papillomaviral DNA is more frequently present within canine subungual squamous cell carcinomas (SCCs) than in non-SCC digit lesions.

METHODS

Total DNA was extracted from 23 canine subungual SCCs and 23 non-SCC digit lesions. The presence of amplifiable DNA within each sample was confirmed by amplifying a section of the glyceraldehyde-3-phosphate dehydrogenase (GADPH) gene. Two different consensus PCR primer sets were used to amplify papillomaviral DNA from the samples.

RESULTS

The consensus primers only amplified papillomaviral DNA from the positive control samples. None of the 46 canine digit samples contained DNA that was amplifiable by the consensus PCR primers.

CONCLUSION

Papillomaviruses are unlikely to be a significant cause of canine subungual SCCs.

CLINICAL RELEVANCE

While circumstantial evidence suggests that canine subungual SCCs could develop due to papillomaviral infection, this study did not reveal any evidence to support papillomaviral aetiology of these neoplasms.

Entire genomic sequence of novel canine papillomavirus type 13

Papillomaviruses are associated with benign and malignant neoplasias of the skin and mucous membranes. The sequence of a novel canine papillomavirus was determined from DNA detected in the oral cavity of a dog. The sequence of the novel virus canine papillomavirus type 13 (CPV13) shares the highest levels of similarity with the Tau papillomaviruses CPV2 and CPV7.

Detection of six novel papillomavirus sequences within canine pigmented plaques

In dogs, papillomaviruses are thought to cause oral and cutaneous papillomas and pigmented plaques. Eight canine papillomaviruses have been fully sequenced to date. Four of these canine papillomaviruses, including Canis familiaris papillomavirus (CPV)-3, CPV-4, CPV-5, and CPV-8, were amplified from pigmented plaques. Given the identification of several different canine papillomaviruses within pigmented plaques, it is likely that there are additional papillomavirus sequences that have not been previously identified. The aim of the present study was to amplify papillomavirus DNA from pigmented plaques and identify potentially novel papillomavirus sequences through nucleotide sequence analysis. Polymerase chain reaction was used to amplify DNA sequences of the papillomavirus L1 gene from 27 pigmented plaques. Identification of novel papillomavirus sequences was based on less than 90% shared DNA homology to any known papillomavirus. DNA from 10 different papillomaviruses was identified within the pigmented plaques, including 6 putative novel papillomavirus sequences. CPV-4 was detected within 41% (11/27) of the pigmented plaques, while CPV-5 was identified within 2 pigmented plaques and CPV-3 within a single pigmented plaque. A previously identified novel papillomavirus sequence was identified within 2 pigmented plaques. The remaining 11 pigmented plaques contained 6 papillomavirus DNA sequences that have not been previously reported. These putative novel PV sequences were most similar to the canine papillomaviruses that have been detected within canine pigmented plaques.

Malignant transformation of a putative eyelid papilloma to squamous cell carcinoma in a dog

A 6-year-old female spayed Chihuahua was presented for the evaluation of generalized pigmented cutaneous masses, one of which was present on the lower right eyelid. The dog was not on immunosuppressive medications and did not have historical or laboratory evidence of underlying endocrine disease, including hypothyroidism and hyperadrenocorticism. Histopathology, immunohistochemistry, and polymerase chain reaction of a cutaneous biopsy from the left antebrachium containing representative lesions confirmed viral papillomatosis. Additionally, histopathology of the antebrachial mass revealed regions of epithelial dysplasia suggestive of possible early transformation to malignancy. Over the course of 5 months, the mass on the right lower eyelid progressed to encompass and efface the majority of the eyelid margin. Additionally, the eyelid tumor had changed from an ovoid, brown pigmented mass to an irregular, flesh-colored mass. At the dog's last recheck examination, a corneal ulcer had developed beneath the irregular dorsal margin of the tumor. Histopathology of the eyelid mass was consistent with squamous cell carcinoma (SCC) and was positive for the presence of papillomavirus using polymerase chain reaction. This report describes the transformation of a putative viral eyelid papilloma into a malignant SCC in an adult dog.