Evaluation of feline oral squamous cell carcinomas for p16CDKN2A protein immunoreactivity and the presence of papillomaviral DNA

Feline Papillomatosis

Different types of feline papillomaviruses (PVs) are associated with a variety of skin lesions and neoplasia, such as papillomas and cell carcinomas, but the virus can also be found in healthy skin. In this review, the European Advisory Board on Cat Diseases (ABCD), a scientifically independent board of veterinary experts on feline infectious diseases from 11 European Countries, discusses the current knowledge of feline PV infections. Cats most likely become infected through lesions or abrasions of the skin. Most PV infections remain asymptomatic. Besides cat-specific PVs, DNA sequences most closely related to human and bovine PVs have been detected in feline skin lesions. Diagnosis is supported by the histological detection of PV-induced cell changes and intralesional detection of viral antigen (immunostaining) or viral DNA (in situ hybridization). Immunostaining of p16CDKN2A protein (p16) can be performed as a proxy marker for PV-induced neoplasms. There is no specific treatment for PV-induced skin lesions. Spontaneous regression commonly occurs. In the case of invasive squamous cell carcinoma (ISCC), complete excision should be considered, if possible.

Papillomaviruses and Papillomaviral Disease in Dogs and Cats: A Comprehensive Review

Papillomaviruses (PVs) frequently infect humans as well as non-human species. While most PV infections are asymptomatic, PVs can also cause hyperplastic papillomas (warts) as well as pre-neoplastic and neoplastic lesions. In this review, the life cycle of PVs is discussed, along with the mechanisms by which PVs cause hyperplastic and neoplastic diseases. The humoral and cell-mediated immune responses to PVs are reviewed, giving context to the later discussion on the use of vaccines to reduce canine and feline PV-associated disease. Both dogs and cats are infected by numerous different PV types classified into multiple different PV genera. The taxonomic classification of PVs is reviewed, along with the significance of this classification. The PV-associated diseases of dogs and cats are then described. These descriptions include the clinical presentation of the disease, the causative PV types, the histological features that allow diagnosis, and, where appropriate, possible treatment options. The review is comprehensive and contains the latest information about PVs and the diseases they cause in dogs and cats.

Expression of mPGES1 and p16 in feline and human oral squamous cell carcinoma: A comparative oncology approach

Comparative cancer studies help us determine if discoveries in one species apply to another. Feline and human oral squamous cell carcinoma (FOSCC and HOSCC) are invasive tumours in which inflammation and abnormal p16 expression are reported. Immunohistochemistry was used to determine the expression of p16 and microsomal prostaglandin E2 synthase 1 (mPGES1) in 42 HOSCC and 45 FOSCC samples with known expression of cyclooxygenase 2 (COX2) and cluster of differentiation 147 (CD147). High p16 expression was more common in HOSCC tumour cells compared to adjacent stroma and oral epithelium (p < .05), with a similar but statistically nonsignificant pattern in FOSCC. Interestingly, high mPGES1 expression in FOSCC was more common in the adjacent epithelium compared to the other compartments (p < .05). In HOSCC, mPGES1 was more similar between compartments but was numerically more common in the tumour compartment (p > .05). There were nominal (p > 0.05) differences in marker expression between high and low mPGES1 expressing tumours in both species, including high p16 observed more commonly in high mPGES1 tumours, and COX-2 positive tumours being more common in low mPGES1 tumours. High CD147 HOSCC tumours were more common in the high mPGES1 HOSCC group (p < .05). In the FOSCC cohort, where there was no statistical difference in CD147 expression between high and low mPGES1 tumours, there were numerically higher CD147 cases in the high mPGES1group. Different expression patterns in FOSCC and HOSCC could be related to different risk factors. For example, p16 is a marker of papillomavirus-driven HOSCC, but a causal relationship between papillomaviruses and FOSCC has yet to be definitively demonstrated. The significance of high P16 expression in the absence of papillomavirus infection deserves further study, and the relative contributions of COX2 and mPGES1 to tumour inflammation and progression should be explored. The findings reveal potential similarities in FOSCC and HOSCC biology, while also demonstrating differences that may relate to risk factors and pathogenesis that are unique to each species.

Two Lineages of Papillomaviruses Identified from Caracals (Caracal caracal) in South Africa

Papillomaviruses (PV) infect epithelial cells and can cause hyperplastic or neoplastic lesions. In felids, most described PVs are from domestic cats (Felis catus; n = 7 types), with one type identified in each of the five wild felid species studied to date (Panthera uncia, Puma concolor, Leopardus wiedii, Panthera leo persica and Lynx rufus). PVs from domestic cats are highly diverse and are currently classified into three genera (Lambdapapillomavirus, Dyothetapapillomavirus, and Taupapillomavirus), whereas those from wild felids, although diverse, are all classified into the Lambdapapillomavirus genus. In this study, we used a metagenomic approach to identify ten novel PV genomes from rectal swabs of five deceased caracals (Caracal caracal) living in the greater Cape Town area, South Africa. These are the first PVs to be described from caracals, and represent six new PV types, i.e., Caracal caracal papillomavirus (CcarPV) 1-6. These CcarPV fall into two phylogenetically distinct genera: Lambdapapillomavirus, and Treisetapapillomavirus. Two or more PV types were identified in a single individual for three of the five caracals, and four caracals shared at least one of the same PV types with another caracal. This study broadens our understanding of wild felid PVs and provides evidence that there may be several wild felid PV lineages.

Canine and feline papillomaviruses: an update

Papillomaviruses are small viruses able to cause disease not only in mammalians, but also in birds and reptiles. In recent years, a rising number of papillomaviruses have been identified in dogs and cats, totaling 24 canine papillomavirus (CPV) and six feline papillomavirus (FcaPV). The canine and feline papillomaviruses (CPVs and FcaPVs, respectively) are responsible for multiple lesions in these domestic species but the potential pathological relevance of some recently identified types remains to be determined. CPVs are associated with oral papillomatosis, cutaneous papillomas and viral pigmented plaques, and have been rarely associated with the development of oral and cutaneous squamous cell carcinomas in their canine hosts. FcaPVs are associated with oral papillomas, viral plaques, and Bowenoid in situ carcinomas. The present review provides readers with the more recent advances on dog and cat papillomavirus research, bringing an update on this field to both veterinary practitioners and the virology community at large.

Feline Oral Squamous Cell Carcinoma: A Critical Review of Etiologic Factors

Simple Summary

Feline oral squamous cell carcinoma (FOSCC) is the most common oral neoplasia in cats. This malignant tumor is locally invasive, has a high mortality rate, and its etiology is not yet known. A critical review about the potential etiologic factors of FOSCC was performed, considering publications between 2000 and 2022. The initial search resulted in 553 publications, with only 26 of these being included in the review. Sixteen studies were related to viral etiology and nine related to environmental factors such as exposure to tobacco smoke, ectoparasitic products, and the presence of oral comorbidities. When evaluated, feline papillomavirus was detected in 16.2% of samples of FOSCC. In the three studies focused on exposure to tobacco smoke, 35.2% (30/85) of cats with FOSCC had a history of this exposure. Among 485 cats with FOSCC, 6.4% had dental and oral pathology. The present study demonstrates that the available evidence on the etiology of FOSCC is still limited, however, there has been increasing interest in this topic.

Abstract

Feline oral squamous cell carcinoma (FOSCC) is the most common oral neoplasia in cats. This malignant tumor is locally invasive, has a high mortality rate, and its etiology is not yet known. In humans, head and neck squamous cell carcinoma is associated with tobacco smoke, alcohol consumption, and human papillomavirus infection. Herein, a critical review about the potential etiologic factors of FOSCC was performed, considering publications between 2000 and 2022, aiming to synthesize all available scientific evidence regarding this issue. Recommendations of the PRISMA statement and the Cochrane Collaboration were followed and the PubMed database searched by using the MeSH terms MeSH terms “oral”, “mouth”, “lingual”, “labial”, “gingiva”, “carcinoma”, “squamous”, and “feline”. The selection process for eligible studies was based on specific inclusion and exclusion criteria and the quality of the studies assessed. The initial search resulted in 553 publications, with only 26 of these being included in the review. Sixteen studies were related to viral etiology and nine related to environmental factors such as exposure to tobacco smoke, ectoparasitic products, and the presence of oral comorbidities. When evaluated, feline papillomavirus was detected in 16.2% of samples of FOSCC. In the three studies focused on exposure to tobacco smoke, 35.2% (30/85) of cats with FOSCC had a history of this exposure. The consumption of canned food and the use of deworming collars were associated, in only one publication, with a risk of neoplasia increased by 4.7 and 5.3 times, respectively. Among 485 cats with FOSCC, 6.4% had dental and oral pathology (i.e., periodontal disease or feline chronic gingivostomatitis). The present study demonstrates that the available evidence on the etiology of FOSCC is still limited, however, there has been an increasing interest on this topic. To better understand the role of the possible etiological factors of this aggressive disease, and model for its human counterpart, large, prospective multi-institutional studies are needed.

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.

Papillomaviral skin diseases of humans, dogs, cats and horses: A comparative review. Part 1: Papillomavirus biology and hyperplastic lesions

Papillomaviruses (PVs) cause disease in humans, dogs, cats, and horses. While there are some differences, many aspects of the pathogenesis, presentation, and treatment of these diseases are similar between the four species. In this review, the PV-induced diseases of humans are compared to the similar diseases that develop in the companion animal species. By comparing with the human diseases, it is possible to make assumptions about some of the less common and less well-studied diseases in the veterinary species. In the first part of this review, the PV lifecycle is discussed along with the classification of PVs and the immune response to PV infection. The hyperplastic diseases caused by PVs are then discussed; including PV-induced cutaneous, anogenital, and oral warts within the four species.

Infectious Causes of Neoplasia in the Domestic Cat

In recent years, growing attention has been paid to the influence/role of infectious diseases in tumour development and progression. Investigations have demonstrated that some infectious organisms can have a direct role in the development of neoplasia, whereas others can predispose to neoplasia by alterations in the immune response, or by creating a pro-inflammatory environment. Feline leukaemia virus was one of the first infectious agents recognised as an oncogenic organism, and along with feline immunodeficiency virus has received the most attention. Since the discovery of this retrovirus, several other organisms have been associated with neoplastic processes in cats, these include gammaherpes virus, mouse mammary tumour virus, papillomaviruses, hepadnavirus, Helicobacter species, and the parasitic infections Platynosomum fastosum and Opisthorchis viverrini. This review summarises the findings to date.

In situ squamous cell carcinoma of the gingiva and nictitating membrane associated with Felis catus papillomavirus type 3 in a cat

Oral squamous cell carcinomas (OSCCs) are common cancers of cats. While papillomaviruses (PVs) are an important cause of human OSCCs, there is currently little evidence that PVs cause squamous cell carcinomas (SCCs) of the mouth or other mucosal surfaces in cats. In the present cat, in situ carcinomas developed on the gingiva and nictitating membrane. Neoplastic cells within both cancers contained prominent PV-induced cellular changes consistent with those caused by Felis catus PV3 (FcaPV3), and FcaPV3 DNA was amplified from both cancers. Neoplasms also contained intense nuclear and cytoplasmic p16CDKN2A protein (p16) immunolabeling, suggesting PV-induced degradation of retinoblastoma protein. The molecular and histological features strongly suggested the cancers were caused by FcaPV3 infection. This is the first report of an association between PV infection and the development of an in situ carcinoma of the mucosa of cats. The identification of these lesions suggests that PVs might cause a proportion of OSCCs, and SCCs from other mucosal surfaces, in cats.

Investigation of multiple <i>Felis catus</i> papillomavirus types (-1/-2/-3/-4/-5/-6) DNAs in feline oral squamous cell carcinoma: a multicentric study

Recent evidence suggests a possible association of Felis catus papillomavirus type 2 (FcaPV-2) DNA with feline oral squamous cell carcinoma (FOSCC). In this study, type-specific PCR targeting two genes (L1/E6 or E1/E6) of FcaPV-1/-2/-3/-4/-5/-6 was performed to detect viral DNA in a large amount of FOSCC samples collected in Italy and Austria. FcaPV-1/-2/-3/-4/-5 were detected in 7/113 (6.2%), 7/93 (7.5%), 6/113 (5.3%), 1/113 (0.9%) and 2/113 (1.8%) specimens, respectively, with different prevalences in Italian vs. Austrian samples, whilst FcaPV-6 went undetected. Our results confirms that FcaPV-2 is the most prevalent in FOSCC, followed by FcaPV-1/-3 and suggest that FcaPVs have variable circulation rates in European countries.

Renal Senescence, Telomere Shortening and Nitrosative Stress in Feline Chronic Kidney Disease

Kidney tissues from cats with naturally occurring chronic kidney disease (CKD) and adult and senior cats without CKD were assessed to determine whether telomere shortening and nitrosative stress are associated with senescence in feline CKD. The histopathologic assessment of percent global glomerulosclerosis, inflammatory infiltrate, and fibrosis was performed. Senescence and nitrosative stress were evaluated utilizing p16 and iNOS immunohistochemistry, respectively. Renal telomere length was evaluated using telomere fluorescent in situ hybridization combined with immunohistochemistry. CKD cats were found to have significantly increased p16 staining in both the renal cortex and corticomedullary junction compared to adult and senior cats. Senior cats had significantly increased p16 staining in the corticomedullary junction compared to adult cats. p16 staining in both the renal cortex and corticomedullary junction were found to be significantly correlated with percent global glomerulosclerosis, cortical inflammatory infiltrate, and fibrosis scores. p16 staining also correlated with age in non-CKD cats. Average telomere length was significantly decreased in CKD cats compared to adult and senior cats. CKD cats had significantly increased iNOS staining compared to adult cats. Our results demonstrate increased renal senescence, telomere shortening, and nitrosative stress in feline CKD, identifying these patients as potential candidates for senolytic therapy with translational potential.

Papillomaviruses in Domestic Cats

Papillomaviruses (PVs) are well established to cause hyperplastic papillomas (warts) in humans and animals. In addition, due to their ability to alter cell regulation, PVs are also recognized to cause approximately 5% of human cancers and these viruses have been associated with neoplasia in a number of animal species. In contrast to other domestic species, cats have traditionally been thought to less frequently develop disease due to PV infection. However, in the last 15 years, the number of viruses and the different lesions associated with PVs in cats have greatly expanded. In this review, the PV life cycle and the subsequent immune response is briefly discussed along with methods used to investigate a PV etiology of a lesion. The seven PV types that are currently known to infect cats are reviewed. The lesions that have been associated with PV infections in cats are then discussed and the review finishes with a brief discussion on the use of vaccines to prevent PV-induced disease in domestic cats.

Comparison of prevalence of Felis catus papillomavirus type 2 in squamous cell carcinomas in cats between Taiwan and Japan

Felis catus papillomavirus (FcaPV), especially type 2 (FcaPV2) is considered as one of the causative agents in squamous cell carcinoma (SCC) in cats. However, our previous study detected FcaPV3 and FcaPV4, but not FcaPV2 in feline SCCs collected in Japan, suggesting that the prevalence of FcaPV2 in SCC may vary depending on geographic locations. To evaluate this hypothesis, two conventional PCR reactions targeting E1 and E7 genes were performed to detect FcaPV2 in feline SCC samples collected in Taiwan and Japan. While 46.9% (23/49) of feline SCC cases from Taiwan were PCR positive for FcaPV2, only 8.6% (3/35) cases from Japan were positive. Our result suggests that the prevalence of FcaPV2 in feline SCCs may depend on the region.

Beyond tradition and convention: benefits of non-traditional model organisms in cancer research

Traditional laboratory model organisms are indispensable for cancer research and have provided insight into numerous mechanisms that contribute to cancer development and progression in humans. However, these models do have some limitations, most notably related to successful drug translation, because traditional model organisms are often short-lived, small-bodied, genetically homogeneous, often immunocompromised, are not exposed to natural environments shared with humans, and usually do not develop cancer spontaneously. We propose that assimilating information from a variety of long-lived, large, genetically diverse, and immunocompetent species that live in natural environments and do develop cancer spontaneously (or do not develop cancer at all) will lead to a more comprehensive understanding of human cancers. These non-traditional model organisms can also serve as sentinels for environmental risk factors that contribute to human cancers. Ultimately, expanding the range of animal models that can be used to study cancer will lead to improved insights into cancer development, progression and metastasis, tumor microenvironment, as well as improved therapies and diagnostics, and will consequently reduce the negative impacts of the wide variety of cancers afflicting humans overall.

Detection of Felis catus papillomavirus type-2 DNA and viral gene expression suggest active infection in feline oral squamous cell carcinoma

Papillomavirus (PV) infection is associated with development of epithelial cancer in different species, including domestic cat (Felis catus). Felis catus PV type-2 (FcaPV-2) is considered the causative agent of a proportion of feline cutaneous squamous cell carcinoma (SCC), through the transforming properties of its E6 and E7 oncogenes. However, the possible role of FcaPVs in the aetiology of feline oral SCC (FOSCC) is still unclear. The aim of this study was to assess the presence and gene expression of FcaPV-2 in FOSCC samples. We detected FcaPV-2 DNA in 10/32 (31%) of the analysed FOSCC by the use of PCR methods. Importantly, viral mRNA was detected by RT-PCR in 7/10 (70%) of DNA positive samples. In particular, FcaPV-2 L1, E2 and E6E7 genes were found to be expressed in 5/10 (50%), 3/10 (33%) and 5/10 (50%) samples, respectively. Viral DNA was also detected in non neoplastic oral ulcerative lesions (ULs) (4/11, 36%); qPCR suggested a difference in viral load between ULs and FOSCCs, particularly in those expressing E6E7, although it was not statistically significant. These data suggest, but do not definively prove, a possible role of FcaPV-2 in the development of a proportion of FOSCC. Moreover, L1 and E2 gene expression results indicate that FcaPV-2 infection associated with these tumours may possibly be productive.

Identification of A Novel Papillomavirus Associated with Squamous Cell Carcinoma in A Domestic Cat

Papillomaviruses infect the skin and mucosal surfaces of diverse animal hosts with consequences ranging from asymptomatic colonization to highly malignant epithelial cancers. Increasing evidence suggests a role for papillomaviruses in the most common cutaneous malignancy of domestic cats, squamous cell carcinoma (SCC). Using total DNA sequencing we identified a novel feline papillomavirus in a nasal biopsy taken from a cat presenting with both nasal cavity lymphoma and recurrent squamous cell carcinoma affecting the nasal planum. We designate this novel virus as Felis catus papillomavirus 6 (FcaPV6). The complete FcaPV6 7453 bp genome was similar to those of other feline papillomaviruses and phylogenetic analysis revealed that it was most closely related to FcaPV3, although was distinct enough to represent a new viral type. Classification of FcaPV6 in a new genus alongside FcaPVs 3, 4 and 5 is supported. Archived excisional biopsy of the SCC, taken 20 months prior to presentation, was intensely positive on p16 immunostaining. FcaPV6, amplified using virus-specific, but not consensus, PCR, was the only papillomavirus detected in DNA extracted from the SCC. Conversely, renal lymphoma, sampled at necropsy two months after presentation, tested negative on FcaPV6-specific PCR. In sum, using metagenomics we demonstrate the presence of a novel feline papillomavirus in association with cutaneous squamous cell carcinoma.

A virome sequencing approach to feline oral squamous cell carcinoma to evaluate viral causative factors

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A comprehensive high-throughput viral sequencing strategy (ViroCap) was adapted for use with feline tumors.

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Papillomavirus was not commonly associated with feline oral squamous cell carcinoma.

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Feline oral squamous cell carcinoma is a good model for HPV-negative head and neck squamous cell carcinoma in people.

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The virome of FOSCC and normal feline oral mucosa included feline foamy virus, torque teno virus, herpes and papillomavirus, FIV and EBV.

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Co-occurrence of Epstein Barr Virus and feline papillomavirus-3 was found found in a feline oral squamous cell carcinoma sample.

Feline oral squamous cell carcinoma (FOSCC) may be the best naturally-occurring model of human head and neck squamous cell carcinoma (HNSCC). HNSCC can be broadly divided into human papillomavirus (HPV)-negative cancers and HPV-positive cancers where HPV is the causative agent. Previous studies in FOSCC have used both species-specific and species-nonspecific PCR primers that may be insensitive to the detection of PVs and other viruses that may be divergent from known sequences. ViroCap is a targeted capture and next generation sequencing tool that was designed to identify all known vertebrate DNA and RNA viruses. In this study we used a metagenomic approach using ViroCap for DNA viruses in 20 FOSCC, 9 normal feline oral mucosal, and 8 suspected PV positive control samples. We tested the hypothesis that viruses would be enriched in FOSCC compared to normal oral mucosa. The virome of the FOSCC and normal feline oral mucosa consisted of feline foamy virus in 7/20 and 2/9 (35% and 22%), feline torque teno virus in 2/20 and 0/9 (10% and 0%), alphaherpesvirus in 2/10 and 0/9 (10% and 0%), FIV (0% and 22%), Epstein-Barr virus in 1/20 and 0/9 (5% and 0%) and feline papillomavirus in 1/20 and 0/9 samples (5% and 0% respectively). Felis catus papillomavirus-3 was found in 1 of 20 FOSCC samples. A virus was not associated consistently with FOSCC. If PVs have a role in FOSCC it is at most a supplementary or uncommon role. FOSCC appears most closely related to HPV-negative HNSCC. Future research on FOSCC should focus on identifying genetic and environmental causes.

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.

Novel viruses: Update on the significance of papillomavirus infections in cats

PRACTICAL RELEVANCE

Prior to 1990 papillomaviruses (PVs) were not recognised to infect or cause disease in domestic cats. Since this time, the use of histology, immunohistochemistry and, more recently, molecular techniques has revealed that PVs almost certainly cause feline viral plaques and Bowenoid in situ carcinomas, oral papillomas and feline sarcoids. In addition, there is increasing evidence that PVs play a significant role in the development of feline cutaneous squamous cell carcinomas, one of the most common skin cancers of cats. Recent studies have also revealed that most cats are asymptomatically infected with PVs. This raises a critical question that is currently unanswered: why do only a small proportion of infected cats develop disease? In the future it may be possible to prevent PV-induced diseases by using a vaccine to prevent PV infection. Alternatively, novel therapies may be developed that prevent PVs from causing clinical disease by stimulating the host immune response.

CLINICAL CHALLENGES

A recognition of the skin diseases caused by PVs is important to more accurately predict disease progression. Unfortunately, there are currently no non-surgical treatments that have been proven to be beneficial in cats and clinical management of PV-induced skin disease in cats can be challenging.

GLOBAL IMPORTANCE

PVs have a worldwide distribution and negatively impact feline health and welfare globally.

AUDIENCE

This review is aimed at clinicians, especially those who regularly treat cats with skin disease. The review will also be useful to oncologists and researchers who have an interest in how cancer develops in cats.

EVIDENCE BASE

In producing this update the authors have drawn on recently published peer-reviewed literature.

Increased p16CDKN2A, but not p53, immunostaining is predictive of longer survival time in cats with oral squamous cell carcinomas

Although oral squamous cell carcinomas (SCCs) are common in cats there are currently few prognostic markers for these cancers. This study used 52 feline oral SCCs to determine if prognosis can be predicted by the age or sex of the cat, the presence of bone within the diagnostic sample, or the anatomic location of the SCC. Additionally, as p16^CDKN2A protein (p16) and p53 are prognostic for human oral SCCs, p16 and p53 immunostaining was evaluated. Only SCC location and p16 immunostaining were prognostic. Cats with oropharyngeal SCCs had an estimated median survival time (MST) of 151 days which was significantly longer than cats with maxillary (51 days P = 0.017), sublingual (33 days P = 0.011) and mandibular (34 days P = 0.029) SCCs. Overall, 19% of oral SCCs were p16-positive with intense nuclear and cytoplasmic immunostaining within most neoplastic cells, 69% had cytoplasmic immunostaining that was confined to the periphery of nests of neoplastic cells, and 12% had no p16 immunostaining. Cats with p16-positive SCCs had a MST of 87 days, which was significantly longer than cats with p16-peripheral SCCs (MST 37 days, P = 0.03), but not longer than cats with p16-negative SCCs (MST 51 days, P = 0.72). No papillomaviral DNA was amplified from the p16-positive SCCs. Twenty (39%) SCCs contained immunostaining for p53, but this was not prognostic (P = 0.31). These results suggest that feline oral SCCs develop by cellular mechanisms that result in one of three patterns of p16 immunostaining. Cancers which develop due to these mechanisms appear to have different clinical behaviors and p16 immunostaining predicts the behavior of these common feline cancers.

Non-murine models to investigate tumor-immune interactions in head and neck cancer

The immune response has important roles in the biology of solid tumors, including oncogenesis, tumor growth, invasion and metastasis, and response to treatment. Improved understanding of tumor-immune system interactions has provided promising therapeutic options that are based on the rescue and enhancement of the anti-tumoral host response. Immune-based treatments have been approved for clinical use in various types of cancer, including head and neck cancer (HNC); other strategies involving combination therapies are currently in development. These novel therapies were developed based on knowledge derived from in vitro, in silico, and in vivo pre-clinical studies. However, clinical trials seldom replicate the efficacy observed in pre-clinical animal studies. This lack of correlation between pre-clinical studies and clinical trials may be related to limitations of the models used; which highlights the relevance of considering immune-related aspects of different pre-clinical models. Murine models are the most frequently used pre-clinical models of HNC and are discussed elsewhere. Non-murine models have characteristics that offer unique opportunities for the study of HNC etiology, therapeutic strategies, and tumor-immune system interactions. The current review focuses on immune-related aspects of non-murine models, including dog, cat, pig, zebrafish, and frog, that could be used to investigate tumor-immune interactions in HNC.

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.

An Update on Canine, Feline and Bovine Papillomaviruses

Over recent years, a growing number of papillomaviruses have been identified, which cause a wide range of lesions in domestic and wild animals. Papillomavirus-induced lesions may have a great impact on animal health, and some diseases observed in farm animals are associated with significant economic losses. This concise review brings together recent advancements on animal papillomavirus research, providing the scientific community and veterinary practitioners with an update on this rapidly evolving field. Among others, bovine, canine and feline papillomaviruses (BPV, CPV and FcaPV) are most extensively discussed, in view of the recent discovery of new viral types and their worldwide importance for animal health. Feline papillomaviruses 2 is an emerging, highly prevalent pathogen in domestic cats, associated with a subset of malignant skin lesions. Aspects related to cross-species infection by BPV and its environmental co-factors are also addressed. Animal papillomaviruses are also fascinating models for studying molecular and cell biology and have recently inspired some major breakthroughs. Overall, it is clear that additional, international and systematic efforts are needed to clarify which lesions are caused by which viral types and to develop experimental models for studying animal papillomavirus.

p16, pRb, and p53 in Feline Oral Squamous Cell Carcinoma

Feline oral squamous cell carcinoma (FOSCC) is a highly aggressive head and neck cancer in cats, but the molecular pathogenesis of this cancer is still uncertain. In this study, p16, p53, and pRb proteins were detected and quantified by immunohistochemistry in forty-three FOSCC primary tumors and three FOSCC xenografts. p16 mRNA levels were also measured in three FOSCC cell lines (SCCF1, F2, and F3), which were consistent with their p16 immunoreactivity. Feline SCCF1 cells had very high levels of p16 protein and mRNA (55-fold greater) compared to SCCF2 and F3. A partial feline p16 cDNA sequence was amplified and sequenced. The average age of cats with FOSCC with high p16 immunoreactivity was significantly lower than the average age in the low p16 group. Eighteen of 43 (42%) FOSCCs had low p16 intensity, while 6/43 (14%) had high p16 immunoreactivity. Feline papillomavirus L1 (major capsid) DNA was not detected in the SCC cell lines or the FOSCCs with high p16 immunostaining. Five of 6 (83%) of the high p16 FOSCC had low p53, but only 1/6 (17%) had low pRb immunoreactivity. In summary, the staining pattern of p16, p53, and pRb in FOSCC was different from human head and neck squamous cell carcinoma and feline cutaneous squamous cell carcinoma. The majority of FOSCCs have low p16 immunostaining intensity, therefore, inactivation of CDKN2A is suspected to play a role in the pathogenesis of FOSCC. A subset of FOSCCs had increased p16 protein, which supports an alternate pathogenesis of cancer in these cats.

Geno- and seroprevalence of Felis domesticus Papillomavirus type 2 (FdPV2) in dermatologically healthy cats

Background

Papillomaviruses can cause proliferative skin lesions ranging from benign hyperplasia to squamous cell carcinoma (SCC). However, asymptomatic infection is also possible. Several groups have detected Felis domesticus Papillomavirus type 2 (FdPV2) DNA in association with feline Bowenoid in situ carcinoma (BISC). Therefore, a causative connection has been suggested. However, the knowledge about FdPV2 epidemiology is limited. The aim of this study was to describe the genoprevalence and seroprevalence of FdPV2 in healthy cats.

For this purpose an FdPV2-specific quantitative (q)PCR assay was developed and used to analyse Cytobrush samples collected from 100 dermatologically healthy cats. Moreover, an ELISA was established to test the sera obtained from the same cats for antibodies against the major capsid protein (L1) of FdPV2.

Results

The genoprevalence of FdPV2 was to 98 %. Surprisingly, the quantities of viral DNA detected in some samples from the healthy cats exceeded the amounts detected in control samples from feline BISC lesions. The seroprevalence was much lower, amounting to 22 %. The concentrations of antibodies against FdPV2 were relatively low in healthy cats, whereas they were very high in control cats with BISC.

Conclusion

These observations suggest that FdPV2 is highly prevalent, even among healthy cats. However, cats that carry it on their skin mount in most instances no antibody response. It might be hypothesized that FdPV2 is only rarely productively replicating or its replication is only rarely exposed to the immune system.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0776-7) contains supplementary material, which is available to authorized users.

High Numbers of Stromal Cancer-Associated Fibroblasts Are Associated With a Shorter Survival Time in Cats With Oral Squamous Cell Carcinoma

Cancer-associated fibroblasts (CAFs) are fibroblastic cells that express α-smooth muscle actin and have been identified in the stroma of numerous epithelial tumors. The presence of CAFs within the tumor stroma has been associated with a poorer prognosis in some human cancers, including oral squamous cell carcinomas (SCCs). Cats frequently develop oral SCCs, and although these are generally highly aggressive neoplasms, there is currently a lack of prognostic markers for these tumors. The authors investigated the prognostic value of the presence of CAFs within the stroma of oral SCC biopsy specimens from 47 cats. In addition, several epidemiologic, clinical, and histologic variables were also assessed for prognostic significance. A CAF-positive stroma was identified in 35 of 47 SCCs (74.5%), and the median survival time (ST) of cats with CAF-positive SCCs (35 days) was significantly shorter than that of cats with CAF-negative SCCs (48.5 days) (P = .031). ST was also associated with the location of the primary tumor (P = .0018): the median ST for oropharyngeal SCCs (179 days) was significantly longer than for maxillary (43.5 days; P = .047), mandibular (42 days; P = .022), and sublingual SCCs (22.5 days; P = .0005). The median ST of sublingual SCCs was also shorter compared with maxillary SCCs (P = .0017). Furthermore, a significant association was identified between site and the presence of stromal CAFs (P = .025). On the basis of this retrospective study, evaluating the tumor stroma for CAFs in feline oral SCC biopsy specimens may be of potential prognostic value.

Animal models of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the most common oral cancer worldwide. Local bone invasion into the maxilla or mandible and metastasis to regional lymph nodes often result in a poor prognosis, decreased quality of life and shortened survival time for HNSCC patients. Poor response to treatment and clinical outcomes are the major concerns in this aggressive cancer. Multiple animal models have been developed to replicate spontaneous HNSCC and investigate genetic alterations and novel therapeutic targets. This review provides an overview of HNSCC as well as the traditional animal models used in HNSCC preclinical research. The value and challenges of each in vivo model are discussed. Similarity between HNSCC in humans and cats and the possibility of using spontaneous feline oral squamous cell carcinoma (FOSCC) as a model for HNSCC in translational research are highlighted.

Feline Oral Squamous Cell Carcinoma: Clinical Manifestations and Literature Review

Squamous cell carcinoma (SCC) is the most commonly encountered malignant oral tumor in cats. The etiology of this locally invasive tumor is likely multifactorial. Several risk factors have been identified, including the use of flea collars, and a history of feeding canned food and canned tuna. Clinical signs vary depending on tumor location. The tumor commonly arises from the gingiva and mucosa of the maxilla, mandible, tongue, sublingual area, or tonsillar region. Maxillary SCC commonly presents clinically as an ulcerative lesion, whereas mandibular SCC is commonly proliferative, expansile, and firm. Lingual/sublingual SCC may be ulcerative, necrotic, infiltrative, or proliferative. In general, feline oral SCC is an invasive and malignant neoplasm regardless of its location. Surgery, radiation therapy, chemotherapy and combinations thereof have been attempted with rarely a satisfactory response. Currently, cures are obtained only in a small subset of cats whose tumors are amenable to complete resection, or where resection with microscopic residual disease is followed by definitive radiation therapy. A multimodal treatment approach likely offers the best chance of success. For cats with advanced disease, palliative care may improve patients' quality of life, albeit transiently. Sequelae associated with tumor progression and local tissue destruction often result in euthanasia of feline patients with oral SCC.

Characterization of STAT3 expression, signaling and inhibition in feline oral squamous cell carcinoma

Background

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in tumor development by regulating signaling pathways involved in cell proliferation, survival, metastasis and angiogenesis. STAT3 is activated in many cancers, including head and neck squamous cell carcinoma (HNSCC) in people. Feline oral squamous cell carcinoma (OSCC) is similar to advanced or recurrent HNSCC as it is poorly responsive to traditional therapies and carries a poor long-term prognosis. The purpose of this study was to characterize expression and activation of STAT3 in feline OSCC cell lines and tumor samples and to investigate the biologic activity of a novel, allosteric STAT3 inhibitor, LLL12, in feline OSCC cell lines.

Results

We evaluated 3 feline OSCC cell lines and one of these (SCCF2) exhibited high levels of constitutive STAT3 phosphorylation and high sensitivity to LLL12 treatment. Exposure of SCCF2 cells to LLL12 resulted in decreased expression of pSTAT3 and total STAT3, apoptosis as assessed by caspase 3/7 activation, inhibition of colony formation and reduced expression of the STAT3 transcriptional target survivin. In contrast, the STAT3 transcriptional targets VEGF and MCL-1 increased after LLL12 treatment. This was, in part, likely due to LLL12 mediated upregulation of HIF-1α, which is known to drive VEGF and MCL-1 expression. The OSCC cell lines with low basal STAT3 phosphorylation did not exhibit these effects, suggesting that STAT3 inhibition was responsible for the observed results. Lastly, immunohistochemistry for pSTAT3 was performed using a feline OSCC tissue microarray, demonstrating expression in 48 % of samples tested.

Conclusions

These data demonstrate that LLL12 has biologic activity against a feline OSCC cell line expressing pSTAT3 and that STAT3 represents a target for therapeutic intervention in this disease. However, given the up-regulation of several STAT3 transcriptional targets following treatment, further investigation of STAT3 and its related signaling pathways in OSCC is warranted.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0505-7) contains supplementary material, which is available to authorized users.

Something old, something new: Update of the 2009 and 2013 ABCD guidelines on prevention and management of feline infectious diseases

OVERVIEW

The ABCD has published 34 guidelines in two Special Issues of the Journal of Feline Medicine and Surgery (JFMS): the first in July 2009 (Volume 11, Issue 7, pages 527-620) and the second in July 2013 (Volume 15, Issue 7, pages 528-652). The present article contains updates and new information on 18 of these (17 disease guidelines and one special article 'Prevention of infectious diseases in cat shelters'). For detailed information, readers are referred to the guidelines published in the above-mentioned JFMS Special Issues.

A naturally occurring feline model of head and neck squamous cell carcinoma

Despite advances in understanding cancer at the molecular level, timely and effective translation to clinical application of novel therapeutics in human cancer patients is lacking. Cancer drug failure is often a result of toxicity or inefficacy not predicted by preclinical models, emphasizing the need for alternative animal tumor models with improved biologic relevancy. Companion animals (dogs and cats) provide an opportunity to capitalize on an underutilized and biologically relevant translational research model which allows spontaneous disease modeling of human cancer. Head and neck squamous cell carcinoma (HNSCC) is a common cancer with a poor prognosis and limited clinical advancements in recent years. One potential novel spontaneous animal tumor model is feline oral squamous cell carcinoma (FOSCC). FOSCC and HNSCC share similar etiopathogenesis (tobacco and papillomavirus exposure) and molecular markers (EGFR, VEGF, and p53). Both human and feline SCCs share similar tumor biology, clinical outcome, treatment, and prognosis. Future clinical trials utilizing FOSCC as a tumor model may facilitate translation of preclinical cancer research for human cancer patients.

Feline viral papillomatosis: ABCD guidelines on prevention and management

OVERVIEW

Papillomaviruses are epitheliotropic and cause cutaneous lesions in man and several animal species, including cats.

INFECTION

Cats most likely become infected through lesions or abrasions of the skin. Species-specific viruses have been detected but human and bovine related sequences have also been found, suggesting cross-species transmission.

CLINICAL SIGNS

In cats, papillomaviruses are associated with four different skin lesions: hyperkeratotic plaques, which can progress into Bowenoid in situ carcinomas (BISCs) and further to invasive squamous cell carcinomas (ISCCs); cutaneous fibropapillomas or feline sarcoids; and cutaneous papillomas. However, papillomaviruses have also been found in normal skin.

DIAGNOSIS

Papillomavirus-induced skin lesions can be diagnosed by demonstration of papillomavirus antigen in biopsies of skin lesions, or detection of papillomavirus-like particles by electron microscopy and papillomavirus DNA by polymerase chain reaction (PCR).

TREATMENT

Spontaneous regression might be expected. In cases of ISCC, complete excision should be considered if possible.

Development of a PCR assay to detect papillomavirus infection in the snow leopard

Background

Papillomaviruses (PVs) are a group of small, non-encapsulated, species-specific DNA viruses that have been detected in a variety of mammalian and avian species including humans, canines and felines. PVs cause lesions in the skin and mucous membranes of the host and after persistent infection, a subset of PVs can cause tumors such as cervical malignancies and head and neck squamous cell carcinoma in humans. PVs from several species have been isolated and their genomes have been sequenced, thereby increasing our understanding of the mechanism of viral oncogenesis and allowing for the development of molecular assays for the detection of PV infection. In humans, molecular testing for PV DNA is used to identify patients with persistent infections at risk for developing cervical cancer. In felids, PVs have been isolated and sequenced from oral papillomatous lesions of several wild species including bobcats, Asian lions and snow leopards. Since a number of wild felids are endangered, PV associated disease is a concern and there is a need for molecular tools that can be used to further study papillomavirus in these species.

Results

We used the sequence of the snow leopard papillomavirus UuPV1 to develop a PCR strategy to amplify viral DNA from samples obtained from captive animals. We designed primer pairs that flank the E6 and E7 viral oncogenes and amplify two DNA fragments encompassing these genes. We detected viral DNA for E6 and E7 in genomic DNA isolated from saliva, but not in paired blood samples from snow leopards. We verified the identity of these PCR products by restriction digest and DNA sequencing. The sequences of the PCR products were 100% identical to the published UuPV1 genome sequence.

Conclusions

We developed a PCR assay to detect papillomavirus in snow leopards and amplified viral DNA encompassing the E6 and E7 oncogenes specifically in the saliva of animals. This assay could be utilized for the molecular investigation of papillomavirus in snow leopards using saliva, thereby allowing the detection of the virus in the anatomical site where oral papillomatous lesions develop during later stages of infection and disease development.