Felis catus papillomavirus type-2 E6 binds to E6AP, promotes E6AP/p53 binding and enhances p53 proteasomal degradation

Different expression patterns of p63 and p73 in Felis catus papillomavirus type 2-associated feline Merkel cell carcinomas and other epidermal carcinomas

Merkel cell carcinoma (MCC) is a cutaneous neuroendocrine tumor, and more than 90% of feline MCC cases test positive for Felis catus papillomavirus type 2 (FcaPV2). In the present study, basal cell markers p40, p63, and p73 and the stem cell marker SOX2 and cytokeratin 14 (CK14) were immunohistochemically examined in normal fetal, infant, and adult feline skin tissues. The expression of these proteins was examined in tumors positive for FcaPV2, including MCC, basal cell carcinoma (BCC), Bowenoid in situ carcinoma (BISC), and squamous cell carcinoma (SCC). Infant and adult feline skin tissues had mature Merkel cells, which were CK14-, CK18+, CK20+, SOX2+, synaptophysin+ and CD56+, while fetal skin tissue had no mature Merkel cells. MCC was immunopositive for p73, CK18, and SOX2 in 32/32 cases, and immunonegative for CK14 in 31/32 cases and for p40 and p63 in 32/32 cases. These results indicate that MCC exhibits different immunophenotypes from Merkel cells (p73-) and basal cells (p40+, p63+, and SOX2-). In contrast, all 3 BCCs, 1 BISC, and 2 SCCs were immunopositive for the basal cell markers p40, p63, and p73. The life cycle of papillomavirus is closely associated with the differentiation of infected basal cells, which requires the transcription factor p63. Changes in p63 expression in FcaPV2-positive MCC may be associated with unique cytokeratin expression patterns (CK14-, CK18+, and CK20+). Furthermore, SOX2 appears to be involved in Merkel cell differentiation in cats, similar to humans and mice.

Feline papillomavirus-associated Merkel cell carcinoma: a comparative review with human Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare skin tumor that shares a similar immunophenotype with Merkel cells, although its origin is debatable. More than 80% of human MCC cases are associated with Merkel cell polyomavirus infections and viral gene integration. Recent studies have shown that the clinical and pathological characteristics of feline MCC are comparable to those of human MCC, including its occurrence in aged individuals, aggressive behavior, histopathological findings, and the expression of Merkel cell markers. More than 90% of feline MCC are positive for the Felis catus papillomavirus type 2 (FcaPV2) gene. Molecular changes involved in papillomavirus-associated tumorigenesis, such as increased p16 and decreased retinoblastoma (Rb) and p53 protein levels, were observed in FcaPV2-positive MCC, but not in FcaPV2-negative MCC cases. These features were also confirmed in FcaPV2-positive and -negative MCC cell lines. The expression of papillomavirus E6 and E7 genes, responsible for p53 degradation and Rb inhibition, respectively, was detected in tumor cells by in situ hybridization. Whole genome sequencing revealed the integration of FcaPV2 DNA into the host feline genome. MCC cases often develop concurrent skin lesions, such as viral plaque and squamous cell carcinoma, which are also associated with papillomavirus infection. These findings suggest that FcaPV2 infection and integration of viral genes are involved in the development of MCC in cats. This review provides an overview of the comparative pathology of feline and human MCC caused by different viruses and discusses their cell of origin.

Antiviral activity of Taurisolo® during bovine alphaherpesvirus 1 infection

Bovine alphaherpesvirus 1 (BoAHV-1), the pathogen causing Infectious Bovine Rhinotracheitis (IBR) and predisposing to polymicrobial infections in cattle, provokes farm economic losses and trading restrictions in the world. However, nontoxic antiviral agents for BoAHV-1 infection are still unavailable, but plant extracts, such as flavonoid derivatives possess activity against BoAHV-1. Taurisolo®, a nutraceutical produced by Aglianico grape pomace, has recently shown promising antiviral activity. Herein, the potential activity of Taurisolo® during BoAHV-1 infection in Madin Darby bovine kidney (MDBK) cells was tested. Taurisolo® enhanced cell viability and reduced morphological death signs in BoAHV-1-infected cells. Moreover, Taurisolo® influenced the expression of bICP0, the key regulatory protein of BoAHV-1, and it strongly diminished virus yield. These effects were associated with an up-regulation of aryl hydrocarbon receptor (AhR), a transcription factor involved in microbial metabolism and immune response. In conclusion, our findings indicate that Taurisolo® may represent a potential antiviral agent against BoAHV-1 infection. Noteworthy, AhR could be involved in the observed effects and become a new target in antiviral therapy.

In Vitro Evaluation of Antiviral Activities of Funicone-like Compounds Vermistatin and Penisimplicissin against Canine Coronavirus Infection

Recent studies have demonstrated that 3-O-methylfunicone (OMF), a fungal secondary metabolite from Talaromyces pinophilus belonging to the class of funicone-like compounds, has antiviral activity against canine coronaviruses (CCoV), which causes enteritis in dogs. Herein, we selected two additional funicone-like compounds named vermistatin (VER) and penisimplicissin (PS) and investigated their inhibitory activity towards CCoV infection. Thus, both compounds have been tested for their cytotoxicity and for antiviral activity against CCoV in A72 cells, a fibrosarcoma cell line suitable for investigating CCoV. Our findings showed an increase in cell viability, with an improvement of morphological features in CCoV-infected cells at the non-toxic doses of 1 μM for VER and 0.5 μM for PS. In addition, we observed that these compounds caused a strong inhibition in the expression of the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor which is activated during CCoV infection. Our results also showed the alkalinization of lysosomes in the presence of VER or PS, which may be involved in the observed antiviral activities.

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.

Prevalence of Eucoleus garfiai in Wild Boars Hunted at Different Altitudes in the Campania and Latium Regions (Italy)

Recent reports of Eucoleus garfiai in wild boars in southern Italy have highlighted the need for collecting epidemiological data on the presence of this parasite and understanding the role of possible interactions between wild boars, E. garfiai, and the environment. This study analyses, using histopathological and biomolecular techniques, the presence of E. garfiai in tongue samples of wild boars hunted in four provinces of the Campania and Latium regions (Italy), in areas located above and below 900 m above sea level (asl). Histopathological examinations revealed the presence of adults and eggs of nematodes, which were subsequently identified as E. garfiai by biomolecular analysis, in the tongue epithelium. The detection of the parasite was more frequent in samples collected from hunting areas located above 900 m asl than in those collected from areas located below 900 m asl (66.67% vs. 38.09%; p < 0.01). Some species of earthworms are intermediate hosts of E. garfiai and it is well known that earthworms are more present in high quality soils. Therefore, we can suggest that the higher prevalence of E. garfiai at higher altitudes is probably linked to a greater presence of earthworms in the soil, due to its higher quality in these areas.

Genomic integration and expression of Felis catus papillomavirus type 2 oncogenes in feline Merkel cell carcinoma

The involvement of Felis catus papillomavirus type 2 (FcaPV2) in feline Merkel cell carcinoma (MCC) has been previously hypothesized. In this study, the expression and localization of FcaPV2 oncogene mRNA, the integration of FcaPV2 genes, and p53 mutations in feline MCC were examined by RNAscope in situ hybridization (ISH), whole genome sequencing (WGS), and Sanger DNA sequencing, respectively. Furthermore, the morphological and molecular characteristics of FcaPV2-positive (FMX-MCC01) and FcaPV2-negative (AS-MCC01) MCC cell lines were compared in vitro and in vivo using immunofluorescence, ISH, xenotransplantation into mice, and immunohistochemistry. ISH for FcaPV2 E6/E7 detected viral RNA in 18/21 FcaPV2-positive MCC and not in 1/1 FcaPV2-negative MCC. WGS of 2 FcaPV2-positive cases revealed the integration of FcaPV2 genes in both cases. In cultured cells and xenograft tissues of FMX-MCC01, most cells were positive for E6/E7 by ISH and p16CDKN2A, a few cells were positive for the retinoblastoma protein (pRb), and all cells were negative for p53. In cultured cells and xenograft tissues of AS-MCC01, all cells were negative for p16CDKN2A, most cells were positive for pRb, and some cells were positive for p53. Missense mutations in p53 were identified in 8/10 FcaPV2-positive and 1/1 FcaPV2-negative MCC. These results suggest that the expression of integrated FcaPV2 oncogenes might be associated with reduced expression of the tumor suppressor proteins pRb and p53 and might contribute to the development of feline MCC. On the other hand, p53 mutations may be involved in both FcaPV2-positive and FcaPV2-negative MCC tumorigenesis.

Expression of matrix metalloproteinases (MMPs)−2/-7/-9/-14 and tissue inhibitors of MMPs (TIMPs)−1/-2 in bovine cutaneous fibropapillomas associated with BPV-2 infection

Introduction

Bovine papillomaviruses −1/−2 (BPVs) are small non-enveloped double-stranded DNA viruses able to infect the skin of bovids and equids, causing development of neoplastic lesions such as bovine cutaneous fibropapillomas and equine sarcoid. Matrix metalloproteinases (MMPs) are a group of zinc-dependent endopeptidases that degrade basal membrane and extracellular matrix, whose function is essential in physiological processes such as tissue remodeling and wound healing. MMPs activity is finely regulated by a balancing with expression of tissue inhibitors of MMPs (TIMPs), a process that is impaired during tumour development. BPV infection is associated with upregulation of MMPs and /or their unbalancing with TIMPs, contributing to local invasion and impairment of extracellular matrix remodeling in equine sarcoid; however, studies regarding this topic in bovine fibropapillomas are lacking.

Methods

The aim of this study was to perform an immunohistochemical and biochemical analysis on a panel of MMPs and TIMPs in BPV-2 positive bovine cutaneous fibropapillomas vs. normal skin samples.

Results

Immunohistochemistry revealed a cytoplasmic expression of MMP-2 (15/19), a cytoplasmic and perinuclear immunoreactivity of MMP-7 (19/19) and MMP-9 (19/19), along with a cytoplasmic and nuclear pattern of MMP-14 (16/19), accompanied by a cytoplasmic expression of TIMP-1 (14/19) and TIMP-2 (18/19) in tumour samples; western blotting revealed an overexpression of MMP-2 (8/9), MMP-7 (9/9) and MMP-9 (9/9), and a decreased level of MMP-14 (9/9), TIMP-1 (9/9) and TIMP-2 (9/9) in tumour versus normal skin samples. Moreover, gelatine zymography confirmed the expression of pro-active MMP-2 (9/9) and MMP-9 (9/9) and, most importantly, indicated the presence and increased activity of their active forms (82 and 62 kDa, respectively) in tumour samples.

Discussion

This is the first study describing MMPs and TIMPs in bovine cutaneous fibropapillomas and our results suggest that their unbalanced expression in presence of BPV-2 may play a significant role in tumour development. A further analysis of supplementary MMPs and TIMPs could bring new important insights into the papillomavirus induced tumours.

Anti-EGFR monoclonal antibody Cetuximab displays potential anti-cancer activities in feline oral squamous cell carcinoma cell lines

Feline oral squamous cell carcinoma (FOSCC) is a malignant tumor characterized by an aggressive behavior and poor prognosis, for which no fully effective therapies are available. Studies of comparative oncology suggest that epidermal growth factor receptor (EGFR) may be a therapeutic target in FOSCC, similarly to human head and neck SCC (HNSCC), where the use of anti-EGFR monoclonal antibody Cetuximab has entered the clinical practice. The aim of this study was to assess the efficacy of Cetuximab in three validated preclinical models of FOSCC (SCCF1, SCCF2, SCCF3). Sequencing of tyrosine kinase domain of EGFR in the cell lines revealed a wild-type genotype, excluding the presence of activating mutations. Western blotting experiments demonstrated that Cetuximab inhibited activation of EGFR and its downstream kinase Akt in SCCF1, SCCF2 and SCCF3 along with HNSCC cell line CAL 27 included as control. Importantly, CCK-8 and trypan blue exclusion assays revealed that treatment with Cetuximab caused a decrease in cell proliferation and cell viability in all cell lines, with a general dose- and time-dependent trend. Cell death induced by Cetuximab was associated with cleavage of PARP, indicating occurrence of apoptosis. Taken together, our data suggest that Cetuximab exerts potential anti-cancer activities in FOSCC, paving the way for future translational studies aimed at assessing its employment in the therapy of this lethal cancer of cats.

Effectiveness of the Fungal Metabolite 3-O-Methylfunicone towards Canine Coronavirus in a Canine Fibrosarcoma Cell Line (A72)

Canine coronavirus (CCoV), an alphacoronavirus, may cause self-limiting enteric disease in dogs, especially in puppies. The noteworthy plasticity of coronaviruses (CoVs) occurs through mutation and recombination processes, which sometimes generate new dangerous variants. The ongoing SARS-CoV-2 pandemic and the isolation of a novel canine-feline recombinant alphacoronavirus from humans emphasizes the cross-species transmission ability of CoVs. In this context, exploring antiviral compounds is essential to find new tools for fighting against CoVs infections. Fungi produce secondary metabolites, which are often developed as antibiotics, fungicides, hormones, and plant growth regulators. Previous examinations of benzo-γ-pyrone 3-O-methylfunicone (OMF), obtained from Talaromyces pinophilus, showed that it reduces the infectivity of hepatitis C virus and bovine herpesvirus 1. Based on this evidence, this study evaluated the antiviral ability of OMF against CCoV infection in a canine fibrosarcoma (A72) cell line. During CCoV infection, a non-toxic dose of OMF markedly increased features of cell viability. Moreover, OMF induced a significant reduction in virus yield in the presence of an intense downregulation of the viral nucleocapsid protein (NP). These findings occurred in the presence of a marked reduction in the aryl hydrocarbon receptor (AhR) expression. Taken together, preliminary findings suggest that OMF inhibiting AhR shows promising activity against CCoV infection.

Canine Coronavirus Activates Aryl Hydrocarbon Receptor during In Vitro Infection

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that interacts with substrates, including microbial metabolites. Recent advances reveal that AhR is involved in the host response to coronaviruses (CoVs) infection. Particularly, AhR antagonists decrease the expression of angiotensin-converting enzyme 2 (ACE2) via AhR up-regulation, resulting in suppression of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in mammalian cells. Herein, we report that AhR is expressed in canine fibrosarcoma (A72) cells, where it is considerably activated by infection with genotype II of canine coronavirus (CCoV-II). The pharmacological inhibition of AhR, by CH223191, suppressed cell death signs and increased cell viability. Furthermore, the AhR antagonist induced a meaningful decline in virus yield, accompanied by the inhibition of the expression of viral nuclear protein (NP). Fascinatingly, during CCoV infection, a novel co-expression of NP and AhR expression was found. Taken together, our preliminary findings show that infection with CCoV activates AhR, and pharmacologic AhR inhibition reduces CCoV replication, identifying AhR as a possible candidate target for CCoV antiviral therapy.

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.

Infectious Causes of Neoplasia in the Domestic Cat

Simple Summary

Increasingly, cancers are being linked to infections with viruses, bacteria, and parasites in human medicine. This review summarises the current literature regarding neoplasia occurring in association with infectious diseases in domestic cats. To date, most studies have focused on the role of viruses, especially feline leukaemia virus and feline immunodeficiency virus in association with lymphoma, or the role of papillomavirus in cutaneous and oral neoplasms in cats. Recently, there has been a focus on a potential role of mouse mammary tumour virus in feline mammary carcinoma and lymphoma and studies assessing the potential role of gammaherpes virus and hepadnaviruses in feline neoplasia. Additionally, there has been some focus on potential bacterial and parasitic associations with neoplasia; including reports assessing potential associations between Helicobacter species and gastrointestinal neoplasms, and case reports of neoplasia in association with Platynosomum fastosum and Opisthorchis viverrini.

Abstract

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.

Antiviral Property of the Fungal Metabolite 3-O-Methylfunicone in Bovine Herpesvirus 1 Infection

Bovine herpesvirus type-1 (BoHV-1) is a widespread pathogen that provokes infectious rhinotracheitis and polymicrobial infections in cattle, resulting in serious economic losses to the farm animal industry and trade restrictions. To date, non-toxic active drugs against BoHV-1 are not available. The exploitation of bioactive properties of microbial products is of great pharmaceutical interest. In fact, fungi are a promising source of novel drugs with a broad spectrum of activities and functions, including antiviral properties. Hence, the potential antiviral properties of 3-O-methylfunicone (OMF), a secondary metabolite produced by Talaromyces pinophilus, were evaluated on BoHV-1. In this study, during BoHV-1 infection in bovine cells (MDBK), the non-toxic concentration of 5 µM OMF considerably reduced signs of cell death and increased cell proliferation. Furthermore, OMF significantly decreased the virus titer as well as the cytopathic effect and strongly inhibited the expression of bICP0, the major regulatory protein in the BoHV-1 lytic cycle. These findings were accompanied by a considerable up-regulation in the expression of the aryl hydrocarbon receptor (AhR), a multifunctional transcription factor also linked to the host’s response to a herpesvirus infection. Overall, our results suggest that by involving AhR, OMF shows potential against a BoHV-1 infection.

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.

Involvement of Felis catus papillomavirus type 2 in the tumorigenesis of feline Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a cutaneous neuroendocrine tumor. We recently demonstrated that cats with MCC often have other proliferative cutaneous lesions, such as squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). Based on this finding, we hypothesize that Felis catus papillomavirus (FcaPV) is involved in the development of MCC in cats, similar to SCC and BCC. To investigate this hypothesis, the presence of FcaPV nucleic acid and immunoreactivity for tumor suppressor proteins were examined in 21 feline MCC cases. Polymerase chain reaction using FcaPV type-specific primers detected FcaPV2 DNA in 20/21 samples of MCC. The complete FcaPV2 sequence was characterized in one case. In situ hybridization for FcaPV2 E7 revealed punctate nuclear signals within tumor cells in 19/21 MCC. Increased immunoreactivity for p16^CDKN2A protein and decreased immunoreactivity for retinoblastoma (pRb) and p53 proteins were observed in 20/21 MCC. These results suggest that feline MCC cases are infected with FcaPV2 and the subsequent inhibition of pRb and p53 induced by integrated viral oncogenes is associated with feline MCC tumorigenesis, similar to other PV-induced proliferative cutaneous lesions. On the other hand, the single case of FcaPV2-negative MCC showed strong p53 immunoreactivity, suggesting mutations in p53 caused by cancer inducers other than FcaPV2 infection in this case. The present study suggests FcaPV2 as a cause of feline MCC.

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.

Inhibition of Crandell-Rees Feline Kidney cell proliferation by X-ray-induced senescence

Radioresistance and radiotoxicity have been reported following cancer treatments in felines. Optimizing radiation doses to induce cytotoxic effects to only cancer cells and not normal cells is critical in achieving effective radiation therapy; however, the mechanisms of radiation resistance, radiotoxicity, and DNA damage response (DDR) in feline cells have not yet been elucidated. A DNA double-strand break (DSB) is the most toxic type of DNA damage induced by X-rays and heavy ion beams used in treating cancers. Crandell-Rees Feline Kidney (CRFK) cells is one of the most widely used cat cells in life science research. Here, we report that DSB-triggered senescence induced by X-rays is important in inhibiting the proliferation of CRFK cells. We demonstrated through cell proliferation assay that X-rays at doses 2 Gy and 10 Gy are toxic to CRFK cells that irradiating CRFK cells inhibits their proliferation. In X-irradiated CRFK cells, a dose-dependent increase in DSB-triggered senescence was detected according to morphological changes and using senescence-associated β galactosidase staining assay. Moreover, our data indicated that in CRFK cells, the major DDR pathway, which involves the phosphorylation of H2AX at Ser139, was normally activated by ATM kinases. Our findings are useful in the understanding of X-rays-induced cellular senescence and in elucidating biological effects of radiation, e.g., toxicity, in feline cells. Furthermore, our findings suggest that the CRFK cell line is an excellent matrix for elucidating radioresistance and radiotoxicity in cat cells.

The Small Molecule BIBR1532 Exerts Potential Anti-cancer Activities in Preclinical Models of Feline Oral Squamous Cell Carcinoma Through Inhibition of Telomerase Activity and Down-Regulation of TERT

Expression of telomerase reverse transcriptase (TERT) and telomerase activity (TA) is a main feature of cancer, contributing to cell immortalization by causing telomeres dysfunction. BIBR1532 is a potent telomerase inhibitor that showed potential anti-tumor activities in several types of cancer, by triggering replicative senescence and apoptosis. In a previous work, we detected, for the first time, TERT expression and TA in preclinical models of feline oral squamous cell carcinoma (FOSCC); therefore, we aimed at extending our investigation by testing the effects of treatment with BIBR1532, in order to explore the role of telomerase in this tumor and foreshadow the possibility of it being considered as a future therapeutic target. In the present study, treatment of FOSCC cell lines SCCF1, SCCF2, and SCCF3 with BIBR1532 resulted in successful inhibition of TA, with subsequent cell growth stoppage and decrease in cell viability. Molecular data showed that up-regulation of cell cycle inhibitor p21, unbalancing of Bax/Bcl-2 ratio, and down-regulation of survival gene Survivin were mostly involved in the observed cellular events. Moreover, BIBR1532 diminished the expression of TERT and its transcriptional activator cMyc, resulting in the down-regulation of epidermal growth factor receptor (EGFR), phospho-ERK/ERK ratio, and matrix metalloproteinases (MMPs)-1/-2 and−9, likely as a consequence of an impairment of TERT extra-telomeric functions. Taken together, our data suggest that BIBR1532 exerts multiple anti-cancer activities in FOSCC by inhibiting telomerase pathway and interfering with signaling routes involved in cell proliferation, cell survival, and invasion, paving the way for future translational studies aimed at evaluating its possible employment in the treatment of this severe tumor of cats.

Telomerase Reverse Transcriptase (TERT) Expression, Telomerase Activity, and Expression of Matrix Metalloproteinases (MMP)-1/-2/-9 in Feline Oral Squamous Cell Carcinoma Cell Lines Associated With Felis catus Papillomavirus Type-2 Infection

Telomerase activity contributes to cell immortalization by avoiding telomere shortening at each cell division; indeed, its catalytic subunit telomerase reverse transcriptase (TERT) is overexpressed in many tumors, including human oral squamous cell carcinoma (hOSCC). In these tumors, matrix metalloproteinases (MMPs), a group of zinc-dependent endopeptidases involved in cell migration, contribute to invasive potential of cancer cells. A proportion of hOSCC is associated with infection by high-risk human papillomavirus (HR-HPVs), whose E6 oncogene enhances TERT and MMPs expression, thus promoting cancer progression. Feline oral squamous cell carcinoma (FOSCC) is a malignant tumor with highly invasive phenotype; however, studies on telomerase activity, TERT, and MMPs expression are scarce. In this study, we demonstrate telomerase activity, expression of TERT, and its transcriptional activator cMyc along with expression of MMP-1, -2, and -9 in FOSCC-derived cell lines SCCF2 and SCCF3, suggesting a contribution by these pathways in cell immortalization and invasion in these tumors. Recent studies suggest that a sub-group of FOSCC as well as SCCF2 and SCCF3 are associated with Felis catus PV type-2 (FcaPV-2) infection. However, in this work, FcaPV-2 E6 gene knock-down caused no shift in either TERT, cMyc, or MMPs levels, suggesting that, unlike its human counterpart, the viral oncogene plays no role in their regulation.

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.