TGFß in malignant canine mammary tumors: relation with angiogenesis, immunologic markers and prognostic role.

Transforming growth factor-ß (TGFß) and FoxP3 regulatory T cells (Treg) are involved in human breast carcinogenesis. This topic is not well documented in canine mammary tumors (CMT). In this work, the tumoral TGFß expression was assessed by immunohistochemistry in 67 malignant CMT and its correlation to previously determined FoxP3, VEGF, and CD31 markers and other clinicopathologic parameters was evaluated. The high levels of TGFß were statistically significantly associated with skin ulceration, tumor necrosis, high histological grade of malignancy (HGM), presence of neoplastic intravascular emboli and presence of lymph node metastases. The observed levels of TGFß were positively correlated with intratumoral FoxP3 (strong correlation), VEGF (weak correlation) and CD31 (moderate correlation). Tumors that presented a concurrent high expression of TGFß/FoxP3, TGFß/VEGF, and TGFß/CD31 markers were statistically significantly associated with parameters of tumor malignancy (high HGM, presence of vascular emboli and nodal metastasis). Additionally, shorter overall survival (OS) time was statistically significantly associated with tumors with an abundant TGFß expression and with concurrent high expression of TGFß/FoxP3, TGFß/VEGF, and TGFß/CD31. The presence of lymph node metastasis increased 11 times the risk of disease-related death, arising as an independent predictor of poor prognosis in the multivariable analysis. In conclusion, TGFß and Treg cells seem involved in tumor progression emerging as potential therapeutic targets for future immunotherapy studies.

The relationships of platelet-derived growth factor, microvascular proliferation, and tumor cell proliferation in canine high-grade oligodendrogliomas: Immunohistochemistry of 45 tumors and an AFOB-01 xenograft mouse model.

High-grade oligodendroglioma (HGOG) is the most common type of glioma in dogs and expresses platelet-derived growth factor receptor-α (PDGFR-α). Microvascular proliferation is often observed in HGOG. Therefore, the present study investigated the functional relationships between PDGFR-α, microvascular proliferation, and tumor cell proliferation in canine HGOG. The expression of PDGFR-α and PDGF-subunit A (PDGF-A) in tumor cells, as well as endothelial cells and pericytes of tumor-associated microvascular proliferations, in 45 canine HGOGs were examined immunohistochemically. Microvascular proliferation was observed in 24/45 cases (53%). PDGFR-α expression in tumor cells and microvascular proliferations was observed in 45/45 (100%) and 2/24 cases (8%), respectively. Furthermore, PDGF-A expression in tumor cells and microvascular proliferations was detected in 13/45 (29%) and 24/24 cases (100%), respectively. In vitro, stimulation of the canine HGOG cell line AOFB-01 with PDGF-A showed that the doubling time of AOFB-01 cells was significantly shorter with PDGF-A than without PDGF-A. Crenolanib (a PDGFR inhibitor) inhibited AOFB-01 cell proliferation. In vivo, the AOFB-01 xenograft mouse model was treated with crenolanib. Tumor xenografts were smaller in crenolanib-treated mice than in untreated control mice. PDGFR-α expression in tumor cells and PDGF-A expression in microvascular proliferations and tumor cells suggest autocrine and paracrine effects of PDGF-A in canine HGOG. The results of in vitro assays indicate that canine HGOG expresses functional PDGFR-α, which responds to PDGF-A. Therefore, PDGF-A produced by microvascular proliferations and tumor cells may promote the proliferation of PDGFR-α-expressing tumor cells in canine HGOG. PDGFR-α signaling has potential as a therapeutic target.

New molecular targets in canine hemangiosarcoma-Comparative review and future of the precision medicine.

Human angiosarcoma and canine hemangiosarcoma reveal similarities not only in their aggressive clinical behaviour, but especially in molecular landscape and genetic alterations involved in tumorigenesis and metastasis formation. Currently, no satisfying treatment that allows for achieving long overall survival or even prolonged time to progression does not exist. Due to the progress that has been made in targeted therapies and precision medicine the basis for a new treatment design is to uncover mutations and their functions as possible targets to provide tailored drugs for individual cases. Whole exome or genome sequencing studies and immunohistochemistry brought in the last few years important discoveries and identified the most common mutations with probably crucial role in this tumour development. Also, despite a lack of mutation in some of the culprit genes, the cancerogenesis cause may be buried in main cellular pathways connected with proteins encoded by those genes and involving, for example, pathological angiogenesis. The aim of this review is to highlight the most promising molecular targets for precision oncology treatment from the veterinary perspective aided by the principles of comparative science. Some of the drugs are only undergoing laboratory in vitro studies and others entered the clinic in the management of other cancer types in humans, but those used in dogs with promising responses have been mentioned as priorities.

Low-Grade Mammary Gland Tumors in Dogs Have Greater VEGF-A and BMP2 Immunostaining and Higher CD31 Blood Vessel Density.

Tumor angiogenesis is an important process in tumor growth, and different molecules are involved in its regulation including VEGF-A, BMP2, and CD31, which can be considered possible prognostic markers. The aim of this study was to verify whether the VEGF-A and BMP2 immunostaining area, and microvascular density (MVD) might be associated with the degree of malignancy in malignant mammary neoplasms of dogs. For this purpose, samples of mammary malignancies from female dogs embedded in wax were used and separated into 4 main histomorphological types: tubulopapillary carcinomas, solid, complex, and carcinosarcoma, which were separated based on high and low degrees of malignancy. Immunohistochemical analysis was performed on tissue microarray blocks using anti-CD31 antibodies for evaluation of MVD and vascular lumen area, and with anti-VEGF-A and anti-BMP2 to determine the immunostaining area using the DAKO EnVision FLEX+ kit. MVD and vascular lumen area were higher in tubulopapillary carcinomas as were the areas stained by VEGF-A and BMP2. Immunostaining for CD31 was higher in low-grade carcinomas as well as in areas immunostained by VEGF-A and BMP2. There was a positive correlation between VEGF and BMP2 in high (r = 0.556, P < .0001) and low-grade (r = 0.287, P < .0001) carcinomas and between MVD and VEGF-A in low-grade carcinomas (r = 0.267, P = .0064). Thus, the markers evaluated showed greater immunostaining in canine mammary tumors with a lower degree of malignancy.

Cell adhesion molecules E-cadherin and CADM1 are differently expressed in canine inflammatory mammary cancer.

Human inflammatory breast cancer (IBC) and canine inflammatory mammary cancer (IMC) are the most aggressive and lethal types of mammary tumors with specific characteristics such as exacerbated angiogenesis, lymphangiogenesis and lymphangiotropism. E-cadherin expression is another specific feature of IBC not previously studied in canine IMC. In this study, the expression of E-cadherin and CADM1 (Cell Adhesion molecule 1) and their possible role as key molecules involved in the pathogenesis of IMC were immunohistochemically analyzed in 19 canine IMC and 15 grade III non-IMC cases. E-cadherin and CADM1 expression was higher in IMC cases (p = 0.002, p = 0.008, respectively). In the IMC group, E-cadherin cytoplasmic immunolabeling was more frequent (p = 0.035) and it was associated to the expression of the angiogenic and lymphangiogenic factors COX-2 (p = 0.009), VEGF-A (p = 0.031) and VEGF-D (p = 0.008). The differential mRNA expression between IMC and non-IMC was studied by microarray analysis in 6 cases. E-cadherin gene (CDH1) was not up-regulated in IMC cases at a transcriptional level; interestingly CADM1 was 7-fold upregulated. The differential expression of E-cadherin protein in IMC suggests a possible role of E-cadherin in the characteristic exacerbated angiogenesis and lymphangiogenesis and further support IMC as a natural model for the study of human IBC. Future studies in IBC and IMC including a broad panel of adhesion molecules are necessary to elucidate their role in the metastatic process and angiogenesis.

Sorafenib inhibits tumor cell growth and angiogenesis in canine transitional cell carcinoma.

Canine transitional cell carcinoma (cTCC) is the most common naturally occurring bladder cancer and accounts for 1-2% of canine tumors. The prognosis is poor due to the high rate of invasiveness and metastasis at diagnosis. Sorafenib is a multi-kinase inhibitor that targets rapidly accelerated fibrosarcoma (RAF), vascular endothelial growth factor receptor (VEGFR)-1, VEGFR-2, VEGFR-3, platelet-derived growth factor receptor-ß (PDGFR-ß), and KIT. In previous studies, a somatic mutation of B-rapidly accelerated fibrosarcoma (BRAF) and expressions of VEGFR-2 and PDGFR-ß were observed in over 80% of patients with cTCC. Therefore, in this study, we investigated the anti-tumor effects of sorafenib on cTCC. Five cTCC cell lines were used in the in vitro experiments. All five cTCC cell lines expressed VEGFR-2 and PDGFR-ß and sorafenib showed growth inhibitory effect on cTCC cell lines. Cell cycle arrest at the G0/G1 phase and subsequent apoptosis were observed following sorafenib treatment. In the in vivo experiments, cTCC (Sora) cells were subcutaneously injected into nude mice. Mice were orally administered with sorafenib (30 mg/kg daily) for 14 days. Sorafenib inhibited tumor growth compared to vehicle control. The necrotic area in the tumor tissues was increased in the sorafenib-treated group. Sorafenib also inhibited angiogenesis in the tumor microenvironment. Thus, sorafenib may be potential therapeutic agent for cTCC via its direct anti-tumor effect and inhibition of angiogenesis.

Pathways Involved in the Development of Vasculogenic Mimicry in Canine Mammary Carcinoma Cell Cultures.

Vasculogenic mimicry (VM) is the ability of highly aggressive cancer cells to form fluid-conducting channels that facilitate the nutrition and metastasis of cancer cells. Considering the importance of VM in the prognosis of canine mammary gland tumours, this study aimed to investigate global gene expression in two canine mammary carcinoma cell cultures associated with the capacity for VM in vitro. The cell lines were subjected to an in-vitro assay to form VM channels (3D culture). Each cell line was then used in 2D conditions as controls and we compared the global gene expression with that of the 3D cultures. A total of 1,217 differentially expressed genes (DEGs) (P <0.05, fold change >2.0 or <2.0) were observed in 3D conditions compared with 2D culture in the UNESP-CM9 cell line, of which 677 were upregulated genes and 540 were downregulated. In contrast, the UNESP-CM60 cell line had only one upregulated and two downregulated genes. Overall, we identified several genes and pathways involved in the development of VM and these molecular data will be useful for future studies aimed at identifying diagnostic and therapeutic targets for VM in canine mammary carcinoma.

Comparison of vascular endothelial growth factor/vascular endothelial growth factor receptor 2 expression and its relationship to tumor cell proliferation in canine epithelial and mesenchymal tumors.

The vascular endothelial growth factor (VEGF)/VEGF receptor 2 (VEGFR2) signaling pathway plays an important role in tumor angiogenesis. VEGFR2 is expressed not only in vascular endothelial cells but also in tumor cells; however, the relationship of VEGF/VEGFR2 expression and tumor proliferation has yet to be elucidated. In addition, since several studies have reported that VEGFR2 inhibitors are more effective against epithelial tumors than mesenchymal tumors, there may be a difference in VEGF/VEGFR2 expression between epithelial and mesenchymal tumors. The purpose of this study was to elucidate differences in VEGF/VEGFR2 expression between epithelial and mesenchymal tumors and the relationship of VEGF/VEGFR2 expression and proliferation in canine tumor cells. We assessed 29 epithelial and 21 mesenchymal canine tumors for microvessel density (MVD), mRNA transcription levels of von Willebrand Factor (vWF) and endoglin, expression of VEGF, VEGFR2, and phosphorylated VEGFR2 (pVEGFR2), and proliferation index (PI) using real-time reverse transcription polymerase chain reaction and immunohistochemistry. VEGFR2 expression on vascular endothelial cells, MVD, and mRNA transcription levels of vWF and endoglin were not significantly different between the two groups. However, expression of VEGF, VEGFR2, and pVEGFR2 was higher in epithelial tumors (P<0.01). Moreover, PI correlated with pVEGFR2 expression in only epithelial tumors (P<0.01, Rs=0.543). These results suggest that the activity of VEGF/VEGFR2 signaling in tumor cells is raised in epithelial tumors, and that this signaling pathway may be related to tumor cell proliferation in epithelial tumors.

Overexpression of Twist1 in vascular endothelial cells promotes pathological retinal angiogenesis in mice.

Retinal angiogenesis is a critical process for normal retinal function. However, uncontrolled angiogenesis can lead to pathological neovascularization (NV), which is closely related to most irreversible blindness-causing retinal diseases. Understanding the molecular basis behind pathological NV is important for the treatment of related diseases. Twist-related protein 1 (TWIST1) is a well-known transcription factor and principal inducer of epithelial-mesenchymal transition (EMT) in many human cancers. Our previous study showed that Twist1 expression is elevated in pathological retinal NV. To date, however, the role of TWIST1 in retinal pathological angiogenesis remains to be elucidated. To study the role of TWIST1 in pathological retinal NV and identify specific molecular targets for antagonizing pathological NV, we generated an inducible vascular endothelial cell (EC)-specific Twist1 transgenic mouse model ( Tg-Twist1 iEC+ ). Whole-mount retinas from Tg-Twist1 iEC+ mice showed retarded vascular progression and increased vascular density in the front end of the growing retinal vasculature, as well as aneurysm-like pathological retinal NV. Furthermore, overexpression of Twist1 in the ECs promoted cell proliferation but disturbed cell polarity, thus leading to uncontrolled retinal angiogenesis. TWIST1 promoted pathological NV by activating the Wnt/ß-catenin signaling pathway and inducing the expression of NV formation-related genes, thereby acting as a 'valve' in the regulation of pathological angiogenesis. This study identified the critical role of TWIST1 in retinal pathological NV, thus providing a potential therapeutic target for pathological NV.

Expression and prognostic significance of vascular endothelial growth factor-A (VEGF-A) and its receptor in canine prostate cancer.

BACKGROUND: Vascular endothelial growth factor-A (VEGF-A) and its receptor, VEGF receptor-2 (VEGFR-2), represent a complex family of angiogenic molecules consisting of different ligands and receptors. Due to the importance of VEGF-A/VEGFR-2 signaling in tumor proliferation and angiogenesis, this study aimed to evaluate the protein and gene expression levels of VEGF-A and VEGFR-2 in canine prostate cancer (PC). METHODS: We analyzed VEGF-A and VEGFR-2 expression in 87 PC samples by immunohistochemistry and quantitative-polymerase chain reaction. PC samples were graded according to the Gleason score and the immunohistochemical staining for VEGF-A and VEGFR-2 was quantified using a selected threshold from the ImageJ Software. Microvascular density was assessed by cluster of differentiation 31 staining and counting the number of positive vessels. Additionally, the homology of VEGF-A and VEGFR-2 between humans and dogs was assessed, followed by the construction of a protein structure homology model to compare the tertiary structures of these proteins in both species. RESULTS: Negative to weakly positive expression levels of VEGF-A and VEGFR-2 were observed in the epithelial cells of the normal prostate (NP) and prostatic hyperplasia samples. In contrast, the canine proliferative atrophy and PC samples exhibited higher VEGF-A (p < .0001) and VEGFR-2 (p < .0001) compared to NP. Moreover, positive correlations between the expression levels of VEGF-A and VEGFR-2 (Spearman's coefficient (r) = .68, p = .013) and the expression levels of VEGF-A and VEGFR-2 proteins (r = .8, p < .0001) were also observed in the NP samples. Additionally, the patients with PC exhibiting higher VEGFR-2 expression levels experienced a shorter survival period (p = .0372). Furthermore, we found an association between the microvascular density and overall survival. Dogs with a higher number of vessels showed a shorter survival time. We further demonstrated that the VEGF-A and VEGFR-2 exhibited high homology between humans and dogs, and identified their protein structures in both species. CONCLUSIONS: In conclusion, VEGFR-2 appears to be an independent prognostic factor in animals with PC. VEGF-A and VEGFR-2 are highly conserved between humans and dogs, which can be investigated further in future cross-species studies to explore their therapeutic applications.

Bronchial angiogenesis in horses with severe asthma and its response to corticosteroids.

BACKGROUND: Severe asthma in horses is characterized by structural changes that thicken the lower airway wall, a change that is only partially reversible by current treatments. Increased vascularization contributes to the thickening of the bronchial wall in humans with asthma and is considered a potential new therapeutic target. OBJECTIVE: To determine the presence of angiogenesis in the bronchi of severely asthmatic horses, and if present, to evaluate its reversibility by treatment with corticosteroids. ANIMALS: Study 1: Bronchial samples from asthmatic horses in exacerbation (7), in remission (7), and aged-matched healthy horses. Study 2: Endobronchial biopsy samples from asthmatic horses in exacerbation (6) and healthy horses (6) before and after treatment with dexamethasone. METHODS: Blinded, randomized controlled study. Immunohistochemistry was performed using collagen IV as a marker for vascular basement membranes. Number of vessels, vascular area, and mean vessel size in the bronchial lamina propria were measured by histomorphometry. Reversibility of vascular changes in Study 2 was assessed after 2 weeks of treatment with dexamethasone. RESULTS: The number of vessels and vascular area were increased in the airway walls of asthmatic horses in exacerbation (P = .01 and P = .02, respectively) and in remission (P = .02 and P = .04, respectively) when compared to controls. In Study 2, the differences observed between groups disappeared after 2 weeks of treatment with corticosteroids because of the increased number of vessels in healthy horses. CONCLUSIONS AND CLINICAL IMPORTANCE: Angiogenesis contributes to thickening of the airway wall in asthmatic horses and was not reversed by a 2-week treatment with corticosteroids.

Repeatable and objective method for evaluating angiogenesis using real-time RT-PCR of endoglin expression in canine tumours.

Anti-angiogenic therapy is a cancer treatment strategy targeting new blood vessel formation. Microvessel density (MVD) is a histopathological method for evaluating angiogenesis and endoglin is used as an activated endothelial marker in human medicine. The assessment of the treatment effect using MVD is difficult because it is a non-repeatable method. To develop a repeatable method for evaluating angiogenesis, we investigated correlations among MVD, mRNA transcription levels of endothelial markers and angiogenesis factors, and confirmed the agreement of mRNA transcription levels between tissue samples and small samples obtained by fine needle aspiration (FNA). The various types of spontaneous tumours were collected from 51 dogs. MVD was assessed by immunostaining for von Willebrand factor (vWF). mRNA transcription levels of vWF, endoglin, vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR2) were analysed using real-time reverse transcription polymerase chain reaction (real-time RT-PCR). There were significant correlations between MVD and mRNA transcription levels of vWF, endoglin and VEGFR2. VEGFR2 was more strongly correlated with endoglin (P <.01, Rs = 0.649) than vWF (P <.01, Rs = 0.512), indicating that angiogenesis can be evaluated more accurately by the measurement of mRNA transcription levels of endoglin. The mRNA transcription levels in tissue and FNA samples were strongly correlated, suggesting that evaluating angiogenesis using FNA samples is possible. In conclusion, we developed a repeatable and objective method for angiogenesis evaluation using mRNA transcription levels of endothelial markers by FNA sampling.

Canine Dilated Cardiomyopathy: Diffuse Remodeling, Focal Lesions, and the Involvement of Macrophages and New Vessel Formation.

Dilated cardiomyopathy (DCM) is among the most common cardiac diseases in dogs. Its pathogenesis is not fully understood, but myocardial remodeling and inflammation are suspected to be involved. The present study aimed to characterize the pathological processes in canine DCM, investigating morphological changes in association with the expression of relevant cytokines and remodeling markers. The myocardium of 17 dogs with DCM and 6 dogs without cardiac diseases was histologically evaluated, and selected cases were further examined by immunohistochemistry, morphometry, and reverse transcription quantitative PCR. In DCM, the myocardium exhibited subtle but statistically significant diffuse quantitative changes. These comprised increased interstitial collagen deposition and macrophage numbers, as well as an overall reduced proportion of contractile tissue. This was accompanied by a significant increase in myocardial transcription of intracellular adhesion molecule (ICAM) 1, inflammatory cytokines, and remodeling enzymes. Laser microdissection showed that cardiomyocytes transcribed most relevant markers including ICAM-1, tumor necrosis factor α, transforming growth factor ß (TGF-ß), matrix metalloproteinase 2 (MMP-2), tissue inhibitor of MMP (TIMP) 1 and TIMP-2. In addition, there were multifocal cell-rich lesions characterized by fibrosis, neovascularization, macrophage infiltration, and cardiomyocyte degeneration. In these, macrophages were often found to express ICAM-1, TGF-ß, and vascular endothelial growth factor; the former two were also expressed by cardiomyocytes. These results characterize the diffuse myocardial remodeling processes that occur in DCM. The observed multifocal cell-rich lesions might result from reduced tissue perfusion. Macrophages and cardiomyocytes seem to actively contribute to the remodeling processes, which ultimately lead to cardiac dilation and dysfunction. The precise role of the involved cells and the factors initiating the remodeling process still needs to be identified.

Significance of Angiogenic Growth Factors in Bovine Ocular Squamous Cell Carcinoma.

Bovine ocular squamous cell carcinoma (BOSCC) is the most common and economically significant neoplasm of the eye in cattle. This study investigated the role of angiogenic growth factors in the pathogenesis of BOSCC. Eighteen cases of BOSCC were classified histopathologically according to the degree of differentiation. Normal upper and lower eyelids and third eyelids collected from the right and left eyes of six healthy cattle aged 1-3 years, that had been presented for slaughter to abattoirs, served as controls. Transcription of genes encoding the angiogenic growth factors vascular endothelial growth factor-C (VEGF-C), basic fibroblast growth factor (bFGF), platelet-derived growth factor-C (PDGF-C) and platelet-derived growth factor receptor-α (PDGFR-α) was determined by quantitative real-time polymerase chain reaction (RT-PCR) in tissue obtained from paraffin wax blocks. Immunohistochemistry (IHC) was utilized to detect intensity of expression and tissue distribution of these growth factors. IHC results revealed that bFGF and PDGF-C were elevated significantly (P >0.05) and VEGF-C expression was decreased in BOSCC compared with healthy control tissue. PDGR-α expression was elevated; however, the difference, compared with control tissues, was not significant. RT-PCR results showed an inverse relationship to the results of IHC; where protein levels were elevated their corresponding mRNA levels were decreased or vice-versa. Angiogenic regulators therefore appear to play a role in the pathogenesis of BOSCC.

Angiogenesis-related gene expression profile in clinical cases of canine cancer.

The balance between pro- and anti-angiogenic signalling is tightly regulated in normal tissues to maintain the functions of the vasculature. In contrast, the overproduction of angiogenic factors and enhanced angiogenesis are frequently observed in several types of tumours. Although there have been many reports on the correlation between tumour progression and angiogenesis in humans, little is known about tumour angiogenesis in canines. Hence, we attempted to clarify whether angiogenesis contributes to tumour progression in canines as well as humans. In this study, we investigated the expression of several angiogenesis-related genes, including CD34, VEGF-A, VEGFR-1, VEGFR-2, Ang-1, Ang-2, Tie1, and Tie2, in 66 canine tumour tissues and in the normal tissues surrounding the tumours by quantitative real-time PCR analysis. Our comparative analysis between canine tumour tissues and normal tissues revealed that several angiogenesis-related genes, such as vascular endothelial growth factor (VEGF) and VEGF-receptor genes, were significantly upregulated in canine tumour tissues when compared to the normal tissues. We also found that the angiopoietin (Ang)-1/Ang-2 gene expression ratio was lower in canine tumour tissues than in the normal tissues, suggesting less association between vascular endothelial cells and perivascular cells in the canine tumour tissues. Taken together, our results suggest that several angiogenesis-related genes may contribute to the malignant progression of canine tumours via tumour angiogenesis.

Tumour angiogenesis, anti-angiogenic therapy and chemotherapeutic resistance.

In order for a tumour to continue to grow and disseminate, it must acquire a new blood supply. Neovascularisation can be enacted by a number of different mechanisms. This dependence of tumour progression on an augmented vascular supply has been exploited by the development of anti-angiogenic drugs, which are designed to inhibit new blood vessel formation or disrupt existing tumour-associated vasculature, both leading to ischaemic-hypoxic tumour cell death. However, the clinical benefits of these therapeutic approaches are frequently variable and often transient, the neoplasm sometimes being able to use other neovascularisation mechanisms to maintain its blood supply and thus evade the current anti-angiogenic therapy. Tumours may also develop a more malignant phenotype following this treatment. Clinical outcomes may be improved by simultaneously inhibiting different angiogenic pathways, abetted by more effective drug delivery regimens such as metronomic chemotherapy and the concurrent use of other antitumour modalities.

Evidence of Vasculogenic Mimicry in a Palpebral Melanocytoma in a Dog.

A 7-year-old neutered female Doberman pinscher was presented with a palpebral nodule on the haired eyelid of the left eye. The nodule was removed surgically. Microscopically, the nodule was consistent with eyelid melanocytoma. The tumour was characterized by the presence of numerous lacunar and slit-like spaces filled by erythrocytes and interspersed throughout the neoplastic melanocytes. Immunohistochemically, these spaces were lined by cells expressing PNL2, but the cells were negative for factor VIII and CD31. [corrected] These findings were consistent with neoplastic melanocytes without endothelial cell participation. This feature was interpreted as 'vasculogenic mimicry', a mechanism of tumour angiogenesis that is well-recognized in human melanomas, but has not yet been reported in melanomas in animals.

In vitro and in vivo activity of liposome-encapsulated curcumin for naturally occurring canine cancers.

Curcumin has well-established anti-cancer properties in vitro, however, its therapeutic potential has been hindered by its poor bioavailability. Lipocurc is a proprietary liposome-encapsulated curcumin formulation that enables intravenous delivery and has been shown to reach its highest concentration within lung tissue. The goal of this study was to characterize the anti-cancer and anti-angiogenic activity of Lipocurc in vitro, in addition to evaluating Lipocurc infusions in dogs with naturally occurring cancer. We therefore evaluated the effect of Lipocurc, relative to free curcumin, on the viability of canine osteosarcoma, melanoma and mammary carcinoma cell lines, as well as the ability of Lipocurc to inhibit endothelial cell viability, migration and tube formation. We also undertook a pilot clinical trial consisting of four weekly 8-hour Lipocurc infusions in 10 cancer-bearing dogs. Tumour cell proliferation was inhibited by curcumin at concentrations exceeding those achievable in the lung tissue of dogs. Similarly, equivalent high concentrations of Lipocurc and curcumin also inhibited endothelial cell viability, migration and tube formation. Four out of six dogs completing planned infusions of Lipocurc experienced stable disease; however, no radiographic responses were detected.

A single dose of intravenous combretastatin A4-phosphate is reasonably well tolerated and significantly reduces tumour vascularization in canine spontaneous cancers.

Combretastatin A4-phosphate (CA4P) is an anti-tumour vascular targeting agent which selectively blocks tumour blood flow. Research on CA4P in rodent tumour models is extensive; however, knowledge of its effect on spontaneous cancer is scarce. This study was conducted in canine patients with spontaneous solid tumours. The goal was to assess the toxicity and efficacy of CA4P in various spontaneous tumour types. Eight dogs with spontaneous tumours were enrolled and treated with a single dose of 75 mg m-2 intravenous CA4P. The dogs were screened and monitored before and after injection. Pre- and post-treatment tumour blood flow was analysed in vivo by power Doppler ultrasound (PDUS) and contrast-enhanced ultrasound (CEUS). Vessel destruction and tumour necrosis were evaluated by histopathology. Clinically relevant toxicity was limited to one case of temporary tetraparesis; other adverse events were mild. Significant cardiovascular changes were mostly confined to changes in heart rate and cTnI levels. Macroscopic tumour size reduction was evident in 2 dogs. Based on PDUS and CEUS, CA4P induced a significant decrease in vascular index and tumour blood flow. Post-treatment, histopathology revealed a significant increase of necrotic tumoural tissue and a significant reduction in microvessel density in tumoural tissue. Anti-vascular and necrotizing effects of CA4P were documented in a variety of canine spontaneous cancers with only minimal side effects. This is the first study reporting the administration of CA4P to canine cancer patients with in vivo and ex vivo assessment, and a first step toward implementing CA4P in combination therapies in veterinary oncology patients. The use of CA4P in canine patients was approved and registered by the Belgian Federal Agency for Medicines and Health Products (FAMHP) (approval number 0002588, registration number 6518 ID 2F12).

Glomeruloid Microvascular Proliferation, Desmoplasia, and High Proliferative Index as Potential Indicators of High Grade Canine Choroid Plexus Tumors.

Choroid plexus tumors (CPT) are intraventricular neoplasms accounting for 10% of all primary central nervous system tumors in dogs. They are frequently classified according to the human WHO classification into choroid plexus papilloma (CPP, grade I), atypical CPP (aCPP, grade II), and choroid plexus carcinoma (CPC, grade III). Histological features observed in canine CPT such as increased vascular density (IVD) and glomeruloid microvascular proliferation (GMVP) are not part of the WHO classification. This multi-centric study aimed to investigate tumor-associated vascular hyperplasia in dogs by determining the prevalence of GMVP and IVD in 52 canine CPT and their association with tumor grade. In addition, the expression of angiogenic factors was assessed by immunohistochemistry in 25 tumors to investigate the pathogenesis of tumor-associated vascular hyperplasia. Based on the classical histological hallmarks, this study of 52 CPT identified 22 (42%) CPP (grade I) and 30 of (58%) CPC (grade III). GMVP was more prevalent in CPC (13/30; 43%) than CPP (1/22; 4%), whereas IVD occurred to a similar extent in CPP and CPC. Desmoplasia was more common in CPC (19/30; 63%) than CPP (2/22; 9%), and similarly, the proliferative index (PI) of neoplastic epithelium was significantly higher in CPC (5.14%) than CPP (0.94%). The majority of CPT expressed platelet-derived growth factor (PDGF), PDGFRα, PDGFRß, and vascular endothelial growth factor (VEGF) irrespective of tumor grade or tumor-associated vascular hyperplasia. These results suggest that tumor-associated GMVP, desmoplasia, and PI may serve as histological indicators of malignancy in CPT.