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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.

Background: equine sarcoids are the most frequent skin tumors in equidae worldwide. It is well known that delta bovine papillomaviruses are their causative agents. We have recently shown the presence in equine sarcoids of abnormal vessel structures, which could cause a hypoxic condition. The aim of this study was to analyze the expression of hypoxia-inducible factor-1 alpha (HIF-1&alpha, ) in a subset of BPV positive equine sarcoids and explore the relationship with vascular endothelial growth factor (VEGF) expression. Results: 80% of equine sarcoids showed strong cytoplasmic staining in &gt, 60% of neoplastic fibroblasts, while 20% of samples showed a moderate cytoplasmic staining in 40&ndash, 60% of neoplastic fibroblasts for HIF-1&alpha, Results of Western blotting (WB) were consistent with immunohistochemistry (IHC). Moreover, a positive correlation between HIF-1&alpha, and VEGF expression (r = 0.60, p &lt, 0.01) was observed. Conclusion: we have shown that HIF-1&alpha, was strongly expressed in equine sarcoid. The upregulation of HIF-1&alpha, has been described in numerous tumors and can be modulated by many proteins encoded by transforming viruses. Thus, it is also possible that BPV could have a relevant role in HIF-1&alpha, pathway regulation, contributing to the development of equine sarcoids by promoting HIF-1&alpha, /VEGF mediated tumor angiogenesis.

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.

Canine mammary tumours are frequent neoplasms mostly affecting intact female dogs, for which no 100% efficient therapy is available. Platelet derived growth factor β receptor (PDGFβR) is a tyrosine kinase receptor (TKR) with a potential role in human breast cancer and a series of canine tumours. In this study we demonstrated, for the first time, expression of PDGFβR and its downstream transduction molecules, mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) and extracellular signal-regulated kinase (ERK), as well as their activated forms in canine mammary tumours by both biochemical analysis and immunohistochemistry. PDGFβR was expressed and hyperphosphorylated in the majority of tumour samples and tumour derived cell lines. Additionally, both MEK and ERK were expressed and activated in cell lines as well as biopsies. TKR inhibitors (TKRi) are currently under investigation as possible therapy in human breast and several canine tumours, thus our in vivo and in vitro findings pave the way for future studies aimed at establishing a potential therapeutic employment of TKRi for the treatment of canine mammary cancer.

Due to high rates of proliferation and DNA synthesis, neoplastic cells have higher requirements of iron than normal cells. For that reason, neoplastic cells have remodelled iron metabolism pathways, over‐expressing genes encoding for iron uptake proteins, among which Transferrin Receptor‐1 (TFR‐1). Accumulating evidence has proven that overexpression of TFR‐1 and high Iron concentration, are both widespread condition of cancer cells, both essential to tumour onset and progression. We studied TFR‐1 and PCNA immunohistochemical expression in fifteen (15) Canine osteoblastic osteosarcomas (COS). After immunohistochemical staining, counting of TFR‐1 positive cells by two independent observers showed that 85%–95% of neoplastic cells were strongly labelled at cytoplasmic level by anti‐TFR‐1 antibody in all examined COS. Furthermore, 70%–80% of neoplastic cells were positively labelled at the nuclear level by PCNA. Surprisingly, about 100% of intratumour vascular endothelial cells were also positive, whereas extratumour vascular endothelial cells were negative. The latter is an interesting finding, as TFR‐1 is usually not expressed in normal vasculature, with the exception of normal brain vascular endothelium, where it allows transport of transferrin, and thus iron, into tissues, suggesting a similar function here to support cancer growth. The early results presented highlight the relevance of TFR‐1 expression in canine OS, suggesting therapies involving both TFR‐1 and Iron metabolisms in dogs with osteosarcoma should be developed., Neoplastic cells have higher requirements of iron than normal cells. For that reason, neoplastic cells over‐express genes encoding for iron uptake proteins, including Transferrin Receptor‐1 (TFR‐1). We studied TFR‐1 immunohistochemical expression in ten Canine osteoblastic osteosarcomas (OS). In all examined OS, 85–95% of neoplastic cells showed a strong cytoplasmic immunostaining with anti‐TFR‐1 antibody. Surprisingly, about 100% of intratumor vascular endothelial cells were also positive, whilst extra‐tumor vascular endothelial cells were negative. The early results presented highlight the relevance of TFR‐1 expression in canine OS, suggesting therapies involving both TFR‐1 and Iron metabolisms in dogs with osteosarcoma should be developed.

It is well known that factors acting on the decrease of population of honeybees, can act on the male and female reproductive system, compromising the fertility of queens and drones. While there are many studies on female fertility, only a few studies have focused on male fertility and the possible alterations of the reproductive system. The testes of 25 samples of adult drones of Apis mellifera ligustica were analyzed by histopathology using an innovative histological processing technique and the alterations that were found are here described. Most of the samples showed unaltered testes but, in some cases, samples showed degenerated seminiferous tubules, while others appeared immature. Although a limited number of samples were analyzed, the results obtained displayed that histopathological alterations of the testes exist also in honeybees and that more interest should be put to the matter, as honeybees could be considered as bioindicators for endocrine disruptors. Future studies on a larger number of samples are necessary to analyze how different environmental factors can act and induce alterations in the honeybee reproductive system.

Oral squamous cell carcinoma (OSCC) is one of the most aggressive and deadliest tumors worldwide. The aryl hydrocarbon receptor (AHR) is a nuclear transcription factor known as a dioxin receptor and mediates the toxic effects of industrial contaminants. In addition, AHR has been implicated in multiple cellular processes and its expression has been shown to play a critical role in tumorigenesis, including human oral cancer cell lines. In the present study, we evaluated the expression of AHR/HSP-90 in 25formalin‑fixed, paraffin-embedded human oral cancer specimens by IHC analysis. CYP1A1 expression was regarded as an AHR reporter gene. The data indicated a complete correlation between AHR expression and cancer grade enabling us to propose AHR as a prognostic marker of oral cancer. Moreover, in OSCC cell line CAL27, we observed the modulatory effect of polydatin, a widespread natural substance and direct precursor of resveratrol, on AHR expression. A computational approach was performed to predict the site of interaction of polydatin on the AHR surface. Our studies confirm the involvement of AHR signaling in the clinicopathological specimens of oral cancer and suggest the use of polydatin for oral cancer prevention.

Background: Sarcoids are the mostcommon skin tumors in horses, ch aracterized by rare regression, invasiveness and high recurrence following surgical intervention and Delta Papillomaviruses are widely recognized as the causative agents of the disease. In order to gain new insights into equine sarco id development, we have evaluated, in 25 equine sarcoids, by immunohistochemistry and western blotting analysis, the expression levels of VEGF, Ki67 and bcl-2. Moreover, we have measured microvessel density an d specific vessel parameters. Results: All sarcoid samples showed a strong and finely granular cytoplasmatic staining for VEGF in the majority (90%) of keratinocytes, sarcoid fibroblasts and endothelial cells. Numerous small blood vessels, immunostained with Von Willebrand factor, often appeared irregular in shape and without a distinct lumen, with mean values of microvessel area and perimeter lower than normal. Moreover, in all sarcoid samples, Ki67 immunoreactivity was moderately positive in 5 – 10% of dermal sarcoid fibroblasts, while Bcl2 immunoreactivity was detected in 52% of the sarcoid samples, with a weak staining in 20 – 50% of dermal sarcoid fibroblasts. Biochemical analysis was consistent with immunohistochemical results. Conclusions: This study has provided evidence that in equine sarcoid: VEGF was strongly expressed; the increased number of vessels was not associated with their complete maturation, probably leading to a hypoxic condition, which could increase VEGF synthesis; the levels of sarcoid fibroblasts proliferation were very low. Concluding, VEGF may have a role in equine sarcoid development, not only through the increase of angiogenesis, but also through the control of sarcoid fibroblast activity.

E6 from high risk human papillomaviruses (HR HPVs) promotes ubiquitination and degradation of p53 tumour suppressor by mediating its binding to ubiquitin ligase E6AP in a ternary complex, contributing to cell transformation in cervical cancer. We have previously shown that Felis catus papillomavirus type −2 (FcaPV-2) E6 is expressed in feline squamous cell carcinoma (SCC) and displays the ability to bind p53 and decrease its protein levels in transfected CRFK cells. However, the mechanism of p53 downregulation has not yet been characterized. Here we show that FcaPV-2 E6 bound to E6AP, which in turn was bound by p53 exclusively in cells expressing the viral oncoprotein (CRFKE6). Furthermore, p53 was highly poly-ubiquitinated and underwent accumulation upon E6AP gene knockdown in CRFKE6. Half-life experiments and proteasome inhibition treatments indicated that down-regulation of p53 protein in CRFKE6 was due to accelerated proteasomal degradation. E6AP/p53 binding was also demonstrated in two feline SCC cell lines expressing FcaPV-2 E6, where p53 protein levels and poly-ubiquitination degree were proportional to E6 mRNA levels. The data obtained in both artificial and spontaneous in vitro models suggest that FcaPV-2 E6 degrades p53 through a molecular mechanism similar to HR HPVs, possibly contributing to the development of feline SCC.

Angiogenesis is crucial for the growth and metastasis of malignant tumours, and various proangiogenic factors promote this process. One of these factors is vascular endothelial growth factor (VEGF), which appears to play a key role in tumour angiogenesis. The aim of the present study was to assess whether VEGF expression is associated with angiogenesis, disease progression and neoplastic proliferation in canine oral squamous cell carcinoma (OSCC) tissue. VEGF immunoreactivity was quantified by immunohistochemistry in 30 specimens, including normal oral mucosa and OSCC tissues graded as well, moderately or poorly differentiated. VEGF expression was correlated with tumour cell proliferation, as assessed using the proliferating cell nuclear antigen (PCNA) marker and microvessel density (data already published). The present results revealed that VEGF and PCNA expression increased significantly between normal oral tissue and neoplastic tissue, and between well and moderately/poorly differentiated tumours. In addition, VEGF expression was strongly correlated with PCNA expression and microvessel density. It was concluded that VEGF may promote angiogenesis through a paracrine pathway, stimulating endothelial cell proliferation and, similarly, may induce tumour cell proliferation through an autocrine pathway. The present results suggest that the evaluation of VEGF may be a useful additional criterion for estimating malignancy and growth potential in canine OSCCs.

The air sacs of free-ranging birds of prey (n= 652) from southern Italy, including 11 species of Accipitriformes and six of Falconiforms, were examined for infections with Serratospiculumtendo (Nematoda: Diplotriaenoidea). Of the 17 species of birds examined, 25 of 31 (80.6%) peregrine falcons (Falco peregrinus) from Calabria Region and a single northern goshawk (Accipiter gentilis) from Campania Region were infected with S. tendo, suggesting a strong host specificity for the peregrine falcon. The northern goshawk and 18 of 25 infected peregrine falcons showed cachexia and all infected birds had bone fractures. At gross examination, air sacculitis and pneumonia were the most common lesions in infected birds. Microscopically, the air-sac walls showed thickening of the smooth muscle cells, resulting in a papillary appearance, along with hyperplasia of the mesothelium and epithelium, and foci of plasma cell infiltration and macrophages associated with several embryonated eggs and adult parasites. Extensive areas of inflammation were found in the lungs, characterized by lymphocytes, macrophages and fibroblasts surrounding embryonated eggs. The northern goshawk also had detachment of the dextral lung with several necrotic foci. In this case, the death of the bird was directly attributed to S. tendo infection. Lesions and pathological changes observed here suggest that S. tendo can cause disease.

Background: Since few decades, the world is facing important losses in the number of honeybees, with great threat to the agro-zootechnic economics and to the global biodiversity. It is well known that stressors

Background: Equine sarcoids are locally invasive, fibroblastic benign skin tumors. Bovine papillomavirus type-1 (BPV-1) and/or Bovine papillomavirus type-2 (BPV-2) are believed to be the causative agent of sarcoids, although the mechanisms by which the virus induce the tumor are still poorly understood. We hypothesized that in genetically predisposed equines latent BPV infection may be reactivated by immunosoppression and/or mechanical injury leading to a form of pathologic wound which may transform into a sarcoid. In this study, we investigated in 25 equine sarcoids and in five normal skin samples the histological features and evaluated the immunohistochemical and molecular expression of type I and type III Collagen, vimentin (VIM), alfa Smooth Muscle Actin (a?-SMA), Matrix Metalloproteinase (MMPs) -2, 9, 14 and tissue inhibitor of metalloproteinase 2 (TIMP-2). Results: In 64 % of investigated sarcoids, type I collagen staining was stronger than that of type III collagen. In 80 % of sarcoids, SFs were strongly positive for vimentin and negative for a?-SMA; the remaining sarcoid samples (20 %) showed 70-80 % of SFs labeled for vim and approximately 20-30 % labeled for a?-SMA. Moreover, all sarcoid specimen showed a variable staining pattern (weak to moderate) for MMP-9 and MMP-14, and a moderate to strong staining for MMP-2 and TIMP-2. Biochemical analysis confirmed immunohistochemical results and showed in sarcoids, for the first time, the cleaved form of MMP9, the 35 KDa active species for MMP-9. Conclusions: This study revealed that in equine sarcoids exhibit an altered turnover of the Extracellular Matrix (ECM) deposition and degradation, as result of an altered expression of MMPs and TIMPs. Therefore, these observations seem to confirm that the basic mechanism for growth of equine sarcoids could be a neoplastic transformation during wound healing.

Bovine papillomavirus type 13 (BPV-13), a novel Deltapapillomavirus, has been found associated with urothelial tumours of the urinary bladder of cattle grazing on lands infested with bracken fern. BPV-13 was detected in 28 of 39 urothelial tumours. Diagnosis was based on sequencing of L1 and E5 amplicons from tumour samples. The nucleotide sequences generated from these amplicons showed a 100% homology with the sequences of BPV-13 L1 and E5 DNA found in Brazil from a fibropapilloma of the ear in a cow and from equine sarcoids in two horses. GenBank accession number of our representative BPV-13 sequences is JQ798171.1. Furthermore, mRNA encoding BPV-13 E5 oncoprotein was also documented, and its expression was also shown by immunohistochemistry and immunofluorescence in the basal and suprabasal urothelial tumour cells. In twenty-three tumours, BPV-13 was simultaneously found with BPV-2, a Deltapapillomavirus genus, species 4. The latter virus was detected by amplifying and sequencing a 154-bp-sized DNA fragment of BPV-2 E5. In addition, BPV-13 by itself was seen to be expressed in five BPV-2-negative urothelial tumours. This study shows that BPV-13 is present in urothelial tumour cells thus sharing biological properties with BPV-1 and BPV-2. Although further studies are needed, BPV-13 appears to be another worldwide infectious agent responsible for a distressing disease causing severe economic losses in cattle industry.

Four hundred bovine urothelial tumours and tumour-like lesions were classified in accordance with the 2004 World Health Organization (WHO) morphological classification for human urothelial tumours. The spectrum of neoplastic lesions of the urinary bladder of cattle is becoming wider and bovine urothelial tumours share striking morphological features with their human counterparts. A classification system based on the WHO scheme would also be appropriate for the classification of bovine bladder tumours. Bovine urothelial tumours are most often multiple. Four distinct growth patterns of bovine urothelial tumours and tumour-like lesions are recognized: flat, exophytic or papillary, endophytic and invasive. Carcinoma in situ (CIS) is the most common flat urothelial lesion, accounting for approximately 4% of urothelial tumours. CIS is detected adjacent to papillary and invasive tumours in 80-90% of cases. Approximately 3% of papillary lesions are papillomas and approximately 5% are 'papillary urothelial neoplasms of low malignant potential' (PUNLMP). Low-grade carcinoma is the most common urothelial tumour of cattle. High-grade carcinomas, and low and high-grade invasive tumours, are less commonly seen. Bovine papillomavirus (BPV) infection and ingestion of bracken fern both play a central role in carcinogenesis of these lesions.

Endothelins and their receptors have been implicated in numerous diseases and have recently emerged as relevant players in a variety of malignancies. Tumours overexpress the Endothelin-1 (ET-1) and the Endothelin-A receptors (ETAR) and their interaction enhances tumour growth and metastasis by promoting tumour cell survival, proliferation and angiogenesis. In this study we have evaluated the expression of ET-1 and ETAR in 50 canine mammary tumours, compared to normal controls. Results demonstrated a progressive increase in ET-1 and ETAR expression from benign tumour to grade 1 and to grade 2 malignant mammary tumours with a decrease of expression in grade 3 carcinomas. Co-localization of ET-1 and ETAR was observed in benign mammary tumours and in G1 and G2 carcinomas, while absent in G3 carcinomas. Concluding, ET-1/ETAR can be considered reliable markers for evaluating malignancy of canine mammary tumours and could have importance for the development of specific anticancer therapies.

Background: Nosemosis is an infection of ventricular epithelial cells of adult European honey bees (Apis mellifera), caused by Nosema species. Until recently, it was thought to be caused only

This report describes the histopathology of two hundred and fifty-three mesenchymal tumors of the urinary bladder in cattle grazing on lands rich in bracken fern. Approximately 80% were hemangiomas and angiosarcomas. Hemangioma (capillary, cavernous, and large vessels) was the most frequent mesenchymal tumor and was more common than angiosarcoma. Although the appearance of endothelial cells can vary remarkably, epithelioid angiosarcomas, often containing multinucleated cells, were the most frequent malignant vascular tumors. Hemangiopericytoma and tumors of muscle and soft connective tissue origin, alone and/or in association with tumor-like lesions, were less frequently seen. Furthermore, forty-five cases of intravascular papillary endothelial hyperplasia (IPEH), a lesion not previously reported in the urinary bladder of cattle, were also described. Bovine papillomavirus type-2 DNA was amplified in tumor samples. Forty vascular tumors were investigated by dual-labeling immunofluorescence, and, for the first time, a coexpression of E5 and platelet-derived growth factorβreceptor (PDGFβR) was shown to occur. The results show that the BPV-2 E5 oncoprotein binds to the activated form of the PDGFβreceptor thus playing an important role in mesenchymal as well as epithelial carcinogenesis of the urinary bladder. Furthermore, these findings demonstrate that BPV-2 infects both epithelial and mesenchymal cells.

Malassezia pachydermatis is a normal inhabitant of canine and feline skin that can spread to other pets. The outer layer or epidermis is made up primarily of keratinocytes, which are capable of releasing various factors and expressing receptors that are significantly involved in the immune regulation. Little is known about the mechanism by which M. pachydermatis overcomes the natural barrier of the skin. The aim of this study was to evaluate the direct in vitro interaction between human keratinocytes and a clinical strain of live M. pachydermatis isolated as a pure culture from an otitic cat. Human keratinocytes (HaCat) were infected with M. pachydermatis to analyse the modulation of the innate immune response. Gene expression was analysed by real-time PCR. We demonstrated that M. pachydermatis invaded HaCat cells and modulated the expression of TLR2 after 24. h infection, while HBD-2, IL-1β TNF-α, IL-6 and IL-8 were modulated both at 24 and 48. h. Thus, our results demonstrated that M. pachydermatis is able to stimulate the innate immune response in infected human keratinocytes indicating a possible role of this yeast as a human opportunistic pathogen.

This report describes the histopathology of two hundred and fifty-three mesenchymal tumors of the urinary bladder in cattle grazing on lands rich in bracken fern. Approximately 80% were hemangiomas and angiosarcomas. Hemangioma (capillary, cavernous, and large vessels) was the most frequent mesenchymal tumor and was more common than angiosarcoma. Although the appearance of endothelial cells can vary remarkably, epithelioid angiosarcomas, often containing multinucleated cells, were the most frequent malignant vascular tumors. Hemangiopericytoma and tumors of muscle and soft connective tissue origin, alone and/or in association with tumor-like lesions, were less frequently seen. Furthermore, forty-five cases of intravascular papillary endothelial hyperplasia (IPEH), a lesion not previously reported in the urinary bladder of cattle, were also described. Bovine papillomavirus type-2 DNA was amplified in tumor samples. Forty vascular tumors were investigated by dual-labeling immunofluorescence, and, for the first time, a coexpression of E5 and platelet-derived growth factor β receptor (PDGFβR) was shown to occur. The results show that the BPV-2 E5 oncoprotein binds to the activated form of the PDGFβ receptor thus playing an important role in mesenchymal as well as epithelial carcinogenesis of the urinary bladder. Furthermore, these findings demonstrate that BPV-2 infects both epithelial and mesenchymal cells.

Bovine cutaneous fibropapillomas are benign skin tumours formed by proliferation of epidermal keratinocytes and dermal fibroblasts caused by bovine papillomaviruses (BPVs). BPV E5 oncoprotein plays a key role in neoplastic cell transformation by specifically binding to the platelet derived growth factor beta receptor (PDGFβR) causing its phosphorylation and activation of proliferation and survival signal transduction pathways, among these phosphatidyl inositol-3-kinase (PI3K)/Akt and Ras-mitogen-activated-protein-kinase-Erk (Ras-MAPK-Erk) pathways. The aim of this study was to investigate the expression of PDGFβR, its phosphorylation status and expression of the downstream molecules phospho-Akt (pAkt) and phospho-Erk (pErk), in naturally occurring bovine cutaneous fibropapillomas. By immunohistochemistry on serial sections we showed cytoplasmic co-expression of the PDGFβR and E5 protein in neoplastic tissue. Western blot analysis revealed that PDGFβR was phosphorylated in higher amount in tumour samples compared to normal skin. pAkt, but not pErk, was also overexpressed in tumour samples. These findings may provide new insights into the aetiopathogenic mechanisms underlying naturally occurring bovine fibropapillomas and contribute to understanding the molecular scenario underlying BPV induced tumourigenesis.

Vascular endothelial growth factor (VEGF) induces endothelial cell proliferation, and the beginning of angiogenesis, by interacting with specific endothelial receptors termed VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1). In this study, Flk-1 expression was evaluated immunohistochemically in 10 benign and 40 malignant canine mammary tumours. There was immunolabelling of endothelial cells located within the neoplastic proliferation and at the infiltrating periphery, and also of neoplastic cells. The number of positive endothelial and neoplastic cells, was higher in malignant than in benign tumours. Moreover, in the malignant tumours, expression of Flk-1 increased from well to less differentiated phenotypes (grade 1–3). The presence of VEGF receptor on neoplastic cells suggests that VEGF has an autocrine function in which neoplastic cells act as both VEGF producers and target cells. Thus, in malignant tumours, VEGF may contribute to neoplastic growth by inducing angiogenesis and by stimulating the proliferation of neoplastic cells.

Angiogenesis, which assists in supplying the nutritional and respiratory needs of proliferating cells, is essential for tumour growth. Angiogenic control is complex, involving a network of cytokines, in particular vascular endothelial growth factor ( VEGF ), a potent endothelial cell mitogen which also stimulates neoplastic cell proliferation. The purpose of this study was to evaluate VEGF expression and microvessel density (number of microvessels per mm 2 ), in canine seminomas. VEGF expression and microvessel density were higher in seminomas than in normal testicular tissue; both parameters were higher in diffuse tumours than in intratubular tumours. These data demonstrate an increase in angiogenesis in the more malignant histological types of seminoma and suggest that both VEGF and microvessel density are useful criteria for evaluating the intrinsic malignancy and growth potential of canine testicular tumours.