Evaluation of angiogenesis in canine mammary tumors by quantitative platelet endothelial cell adhesion molecule immunohistochemistry

Low-grade mammary gland tumours 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 four 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 < 0.0001) and low-grade (r = 0.287, p<0.0001) carcinomas and between MVD and VEGF-A in low-grade carcinomas (r = 0.267, p = 0.0064). Thus, the markers evaluated showed greater immunostaining in canine mammary tumors with a lower degree of malignancy.

Association of mast cell density, microvascular density and endothelial area with clinicopathological parameters and prognosis in canine mammary gland carcinomas

Background

Mast cell density has been shown to have both enhancing and inhibiting effects on tumour progression and the ability to predict breast cancer behaviour in humans. However, prognostic results have been contradictory. Some previous studies suggested involvement of mast cells in the progression of canine mammary tumours. This study investigated total, intratumoural and peritumoural mast cell densities by Giemsa staining, and their association with clinicopathological parameters and the disease outcome of canine mammary tumours. In addition, since mast cells promote angiogenesis, the microvascular density and endothelial area were evaluated by CD31 immunostaining.

Results

Intratumoural mast cell density was associated with tumour size, lymph node involvement and tumour-infiltrating lymphocyte count, while peritumoural mast cell density was associated with grade. The endothelial area was associated with grade, mitotic index, tubular formation and proliferation index. Tumours with a high grade, high total intratumoural mast cell density and a larger endothelial area were associated with shorter disease-free survival. Intratumoural mast cell density and grade were found to be independent prognostic factors.

Conclusions

These results suggest that intratumoural mast cell density and the endothelial area can be used to evaluate the aggressiveness of canine mammary carcinomas, while intratumoural mast cell density could be of use as an independent predictor of a prognosis of disease-free survival. Peritumoural mast cell density does not seem to influence tumour behaviour.

Evaluation of Hypoxia-Inducible Factor-1 Alpha (HIF-1α) in Equine Sarcoid: An Immunohistochemical and Biochemical Study

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-1α) 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 >60% of neoplastic fibroblasts, while 20% of samples showed a moderate cytoplasmic staining in 40-60% of neoplastic fibroblasts for HIF-1α. Results of Western blotting (WB) were consistent with immunohistochemistry (IHC). Moreover, a positive correlation between HIF-1α and VEGF expression (r = 0.60, p < 0.01) was observed.

CONCLUSION

we have shown that HIF-1α was strongly expressed in equine sarcoid. The upregulation of HIF-1α 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-1α pathway regulation, contributing to the development of equine sarcoids by promoting HIF-1α/VEGF mediated tumor angiogenesis.

Know Thy Model: Charting Molecular Homology in Stromal Reprogramming Between Canine and Human Mammary Tumors

Spontaneous canine simple mammary tumors (CMTs) are often viewed as models of human breast cancer. Cancer-associated stroma (CAS) is central for initiation and progression of human cancer, and is likely to play a key role in canine tumors as well. Until recently, however, canine CAS in general, and in CMT in particular, lacked detailed characterization and it remained unclear how canine and human CAS compare. This void in knowledge regarding canine CAS and the resulting lack of unbiased cross-species analysis of molecular homologies and differences undermined the validity of the canine model for human disease. To assess stromal reprogramming in canine breast tumors, we have recently established a protocol to specifically isolate and analyze CAS and matched normal stroma from archival, formalin-fixed paraffin embedded (FFPE) clinical tumor samples using laser-capture microdissection followed by next-generation RNA-sequencing. Using this approach, we have analyzed stromal reprogramming in both malignant canine mammary carcinomas (mCAs) as well as benign canine mammary adenomas in a series of studies. Our results demonstrate strong stromal reprogramming in CMTs and identify high-grade molecular homology between human and canine CAS. Here, I aim to give a short background on the value of comparative oncology in general, and spontaneous CMT in particular. This will be followed by a concise review of the current knowledge of stromal reprogramming in both malignant canine mCA and benign adenoma. Finally, I will conclude with insights on highly conserved aspects of stromal reprogramming between CMT and human breast cancer that accentuate the relevance of CAS in CMT as a model for the human disease.

Immunohistochemical Expression of Vascular Endothelial Growth Factor and Vascular Endothelial Growth Factor Receptor Associated with Tumor Cell Proliferation in Canine Cutaneous Squamous Cell Carcinomas and Trichoepitheliomas

The expression of 5 markers associated with angiogenesis was studied in canine squamous cell carcinomas (SCCs) ( n = 19) and canine trichoepitheliomas (TCPs) ( n = 24). SCCs were assigned histologic grades, and tissue sections from both tumor types were immunohistochemially stained for the expression of vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor-2 (VEGFR-2), as well as intratumoral microvessel density (iMVD), tumor proliferation index (PI), and tumor apoptotic index (AI), using antibodies against VEGF, VEGFR-2, von Willebrand's factor, Ki-67 antigen, and the terminal deoxynucleotidyl transferase-mediated 2′-deoxyuridine 5′-triphosphate endlabeling method (TUNEL), respectively. VEGF and VEGFR-2 were detected in 17/19 (89.4%) and 19/19 (100%) SCCs and in 17/24 (70.8%) and 20/24 (83.3%) TCPs, respectively. In SCCs, there was substantial correlation between histologic grade and PI ( r = 0.51); and moderate correlation between VEGF and histologic grade ( r = 0.43), VEGFR-2 and histologic grade ( r = 0.47), VEGF and PI ( r = 0.47), and VEGFR-2 and PI ( r = 0.47) (Spearman rank correlation coefficient). In TCPs, there was substantial correlation between VEGF and PI ( r = 0.51) and a moderate correlation between VEGFR-2 and iMVD ( r = 0.36). The median iMVD of SCCs (15.5) was significantly higher than the median iMVD of TCPs (9.05) ( P value < .05). It was concluded that VEGF and VEGFR-2 may promote tumor cell proliferation in TCPs and SCCs. An autocrine pathway for VEGF probably operates in canine SCCs and TCPs, as VEGF and VEGFR-2 expression was found in most tumors and was associated with evidence for tumor cell proliferation.

Prognostic Significance of Intratumoral Microvessel Density in Canine Soft-Tissue Sarcomas

The prognosis of canine soft-tissue sarcomas (STS) has traditionally been based on histologic grading. We have recently demonstrated the prognostic value of cellular proliferation markers in canine STS. Another method of predicting the behavior of neoplasms is intratumoral microvessel density (IMD), which is a measure of tumor angiogenesis. The prognostic significance of IMD has been documented in many human neoplasms and in a limited number of canine and feline neoplasms. To evaluate the prognostic value of IMD in canine STS, we studied 57 STS and compared IMD with histologic features, histologic grade, cellular proliferation, metastatic propensity, and survival. Using immunohistochemistry, the STS were labeled with anti—factor VIII-related antigen (FVIII-RA) and anti-CD31 antibodies to determine 3 IMD parameters: mean microvessel density, high microvessel density, and microvessel area. Using FVIII-RA and CD31, increasing IMD was statistically associated with increasing histologic grade, necrosis scores, and mitotic scores. Higher FVIII-RA IMD values were significantly associated with higher median argyrophilic nucleolar organizing region (AgNOR) values (as previously investigated) and increased metastatic propensity. Fibrosarcomas appear to be the least vascularized of STS. There is no correlation between IMD and survival. Our results indicate that IMD is of prognostic value for histologic grade, histologic features, cellular proliferation (based on AgNOR), and metastatic propensity of canine STS, specifically when using FVIII-RA as the endothelial marker. Assessing histologic grading, cellular proliferation, and IMD of canine STS at the time of diagnosis could therefore provide better prognostic information for the veterinary clinician.

Canine mammary carcinomas: influence of histological grade, vascular invasion, proliferation, microvessel density and VEGFR2 expression on lymph node status and survival time

Spontaneous invasive non-inflammatory canine mammary carcinomas (CMC) and their regional lymph nodes (LN) were analysed (n = 136). Histological grade (HG) and vascular invasion (VI) in the tumours and lymph node status were recorded. Proliferation index (PI), microvessel density (MVD) and vascular endothelial growth factor receptor 2 (VEGFR2) expression were estimated using anti-proliferating cell nuclear antigen (PCNA), anti-von Willebrand factor and anti-Flk-1, respectively. Eighteen months follow-up was performed (34 bitches). Tumours of different grades showed differences regarding PI, Flk-1/integrated optical density (Flk-1/IOD) and MVD. Every feature showed significant association with LN status through bivariate analyses. From multivariate analyses, VI and Flk-1/IOD were selected to predict LN status. Data revealed that the probability of a CMC-bearing bitch to remain alive at 1, 4, 5 and 14-18 months was 0.91, 0.87, 0.81 and 0.77, respectively. Besides LN status, VI was the only feature positively correlated with survival time, although a trend to shorter survival of animal patients bearing high expressing VEGFR2 CMC was noted.

Expression of endothelin-1 and endothelin-1 receptor A in canine mammary tumours

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.

Immunohistochemical investigation of the angiogenic proteins VEGF, HIF-1α and CD34 in invasive ductal carcinoma of the breast

The expression of prognostic markers in cancer has become important in diagnostic routine and research. A high mitotic rate compromises the individual cell access to oxygen and nutrients, due to reduced blood supply. Cells undertake adaptive measures such as vascular endothelial growth factor (VEGF), expressed under the control of hypoxia-inducible factor-1α (HIF-1α). CD34 is an endothelial marker which can show the presence and distribution of blood vessels. This study evaluated the presence and relative expression of VEGF, HIF-1α and CD34 using immunohistochemistry of 60 breast tumors and double staining, correlating the findings with clinical and pathological variables. High VEGF expression was correlated with low cell proliferation, lymph node-negative, smaller tumor size and patients not receiving hormone therapy. High HIF-1α expression predominated in younger (<50-year) patients, subjected to neo-adjuvant therapy and in p53-negative tumors. Absence of metastasis, radiotherapy or hormone treatment, and estrogen receptor (ER)-positive tumors showed high CD34 immunoreactivity. We suggest that the angiogenic factors VEGF, HIF-1α and CD34 are important in breast cancer progression and their abundance in breast tumors has prognostic and predictive value.

Angiogenesis in canine mammary tumours: a morphometric and prognostic study

Angiogenesis in canine mammary tumours (CMTs) has been described previously; however, only the intratumoural (IT) region has been studied and information on peritumoural (PT) angiogenesis is lacking. In this study, the blood vessel density (BVD), blood vessel perimeter (BVP) and blood vessel area (BVA) in IT and PT regions of 56 benign CMTs, 55 malignant CMTs and 13 samples of normal mammary gland tissue were analyzed. In addition, the blood endothelial cell proliferation (BECP) as an indicator of ongoing angiogenesis was investigated. The prognostic value of each parameter was also examined. Blood vessels and proliferating blood endothelial cells were present in IT and PT regions of both benign and malignant tumours. The vessels in the PT region had a significantly higher area and perimeter compared with those in the IT region. Malignant tumours showed significantly more vessels with a smaller total BVA and a higher BECP compared with benign tumours and control tissue. In the PT regions there was a significantly higher BVD, BVA and BVP compared with the vessels in control tissue. Only the IT and PT BVD and PT BECP in benign tumours allowed prediction of survival. The morphology of blood vessels in CMTs shows similarities with those in human breast cancer, which strengthens the case for the use of dogs with CMTs in comparative oncology trials.

EGFR and microvessel density in canine malignant mammary tumours

The epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase receptor which has been shown to have an important role in human breast cancer. Its role appears to be associated with increased angiogenesis and metastasis. In order to clarify its role in canine mammary tumours (CMT), 61 malignant neoplasms were studied by using immunohistochemistry, comparing expression of EGFR, microvessel density (MVD) by CD31 immunolabelling and characteristics of tumour aggressiveness. High EGFR immunoexpression was statistically significantly associated with tumour size, tumour necrosis, mitotic grade, histological grade of malignancy and clinical stage. High CD31 immunoreactivity was statistically significantly associated with tubule formation, histological grade of malignancy and clinical stage. A positive correlation between EGFR and CD31 immunoexpression (r = 0.843; P < 0.001) was also observed. Results suggest that an over-expression of EGFR may contribute to increased angiogenesis and aggression in malignant CMT, presenting the possibility of using EGFR inhibitors in the context of metastatic disease treatment.

Canine mammary tumours, an overview

Canine mammary tumours (CMTs) are the most common neoplasms in intact female dogs. Although the prevalence of these tumours decreases in regions where preventive ovari(ohyster)ectomy is performed, it remains an important disease entity in veterinary medicine. Moreover, treatment options are limited in comparison with human breast cancer. Nevertheless, recent human treatment protocols might have potential in bitches suffering from CMTs.

Molecular carcinogenesis of canine mammary tumors: news from an old disease

Studies focusing on the molecular basis of canine mammary tumors (CMT) have long been hampered by limited numbers of molecular tools specific to the canine species. The lack of molecular information for CMT has impeded the identification of clinically relevant tumor markers beyond histopathology and the introduction of new therapeutic concepts. Additionally, the potential use for the dog as a model for human breast cancer is debatable until questions are answered regarding cellular origin, mechanisms, and cellular pathways. During the past years, increasing numbers of canine molecular tools have been developed on the genomic, RNA, and protein levels, and an increasing number of studies have shed light on specific aspects of canine carcinogenesis, particularly of the mammary gland. This review summarizes current knowledge on the molecular carcinogenesis of CMT, including the role of specific oncogenes, tumor suppressors, regulators of apoptosis and DNA repair, proliferation indices, adhesion molecules, circulating tumor cells, and mediators of angiogenesis in CMT progression and clinical behavior. Whereas the data available are far from complete, knowledge of molecular pathways has a significant potential to complement and refine the current diagnostic and therapeutic approach to this tumor type. Furthermore, current data show that significant similarities and differences exist between canine and human mammary tumors at the molecular level. Clearly, this is only the beginning of an understanding of the molecular mechanisms of CMT and their application in clinical patient management.

COX-2 over-expression correlates with VEGF and tumour angiogenesis in canine mammary cancer

This study was designed to investigate the possible roles of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF) in canine mammary cancer angiogenesis. Immunohistochemistry was performed on 70 tumours (28 benign and 42 malignant) in order to detect COX-2 and VEGF expression. Microvessel density (MVD) was determined by CD31 immunolabelling to assess tumour angiogenesis. There was a significantly higher expression of COX-2 (P<0.001), VEGF (P<0.001) and MVD (P<0.001) in malignant compared to benign tumours. In the malignant group, the MVD of COX-2 positive tumours was significantly higher than that of COX-2 negative tumours (P=0.026). A similar association was observed for VEGF (P<0.001) positive tumours. The results from this study suggested that over-expression of COX-2 and VEGF may contribute to increased angiogenesis and aggression in malignant tumours.

Canine classical seminoma: a specific malignant type with human classifications is highly correlated with tumor angiogenesis

Background

Human seminoma is classified as classical seminoma (SE) and spermatocytic seminoma (SS). Human SE is known to be more malignant and metastasizing more frequently than SS. Tumor angiogenesis is highly related with tumor progression and metastasis, with microvessel density (MVD) being an important parameter of metastatic potential. Canine seminoma is not yet well-established as SE or SS type including correlation with angiogenesis. We classified canine SE and SS, and then compared them to tumor associated vessels.

Methods

Twenty-three cases of canine seminomas (2 intratubular, 9 diffuse, and 12 intratubular/diffuse seminomas showing both intratubular and diffuse patterns) were classified as SE or SS by immunohistochemistry (IHC) using monoclonal antibody against PLAP and by PAS stain. The histopathological data were then compared to see if there was a correlation with SE or SS. Angiogenesis of seminomas were evaluated by immunohistochemical assay using polyclonal antibody against Von Willebrand factor (vWF) and by calculating the means of MVD, vessels area and perimeters using computerized image analysis. Statistical Package for Social Sciences (SPSS) program was used for various statistical analyses.

Results

The numbers of PLAP+/PAS+ canine SEs were 8/23 (34.8%) and PLAP-/PAS- SSs were 15/23 (61.2%). All SE cases (8/8, 100%) were intratubular/diffuse types. SS types included 2 intratubular (2/15, 13.3%), 9 diffuse (9/15, 60%), and 4 intratubular/diffuse (4/15, 26.7%) types. MVD and vascular parameters in SEs were significantly higher than in SSs, showing the highest value in the intratubular/diffuse type. Seminomas observed with neoplastic cells invasion of vessels presented higher perimeter and area values than seminomas without conformed neoplastic cells invasion.

Conclusion

In this study, we demonstrated a positive relationship between canine SE and tumor angiogenesis. Furthermore, we also showed that a tumor cells invasion of vessels were a correlated vascular parameter. Although metastasis of canine seminomas has rarely been reported, our results support that canine SE could have high metastatic potential similar to the human counterpart. Further studies are required to clarify the relationship between canine SE and clinical data with metastatic factors.

Histological, Immunohistological, and Ultrastructural Description of Vasculogenic Mimicry in Canine Mammary Cancer

Canine inflammatory mammary cancer (IMC) and human inflammatory breast cancer (IBC) are the most aggressive and lethal type of mammary cancer in female dogs and in women. The generation of microvascular channels by malignant tumor cells (endothelial-like cells [ELCs]) without endothelial cell participation (vasculogenic mimicry) has been reported in human breast cancer, including IBC, and is considered a new type of tumor angiogenesis. The aim of this study was to investigate the presence of ELCs in highly malignant canine mammary tumors (IMC and non-IMC) by histology, inmunohistochemistry (pancytokeratin, cytokeratin 14, vimentin, actin, desmin, vWF, CD31, and CD34), and electron microscopy. This retrospective study included 21 female dogs with diagnoses of IMC and 20 animals with metastatic grade III noninflammatory malignant mammary tumors (MMT). IMC tumors (33.33%) and MMT (5%) showed ELCs forming structures similar to small capillaries. The histological, immunohistochemical (positive to AE1/AE3 and cytokeratin 14, mostly negative to endothelial markers), and ultrastructural characteristics of these cells indicated vasculogenic mimicry. The higher frequency of this phenomenon in inflammatory versus noninflammatory canine mammary cancer is in agreement with previous studies in experimental and spontaneous human IBC, and it could be in relation with the extremely high lymphangiogenic capacity and metastatic lymphangiotropism characteristics of inflammatory breast cancer.

Cox-2 Expression in Canine Mammary Carcinomas

Mammary tumors are among the most common neoplastic processes in female dogs. Prostaglandin E2, the catalytic product of Cox-2, may promote tumor development and angiogenesis. It has been investigated in several human cancers and also correlated with the evolution of the disease. However, the clinical implications of tumor pathology require more investigation in veterinary medicine. Angiogenesis is essential for the growth and metastasis of major solid tumors and has been correlated with prognosis in human and canine breast cancer. The aim of this study was to evaluate Cox-2 expression and microvessel density in canine mammary carcinomas and to correlate them with overall survival of the animal. Cox-2 and angiogenesis were assessed by immunohistochemistry in 46 mammary carcinomas (19 ductal and 27 metaplastic) and in healthy mammary glands. To assess tumor angiogenesis, microvessel density (MVD) was determined by CD31 staining. Immunostaining revealed that 46/46 (100%) of the tumors were positive for Cox-2 and CD31, and there was no statistical difference among tumor types. Cox-2 protein expression correlated positively with CD31 staining ( r = 0.3742, P = .0104) but did not correlate significantly with tumor type. Longer overall survival was observed in metaplastic carcinomas ( P = .028), in tumors with low microvessel density ( P = .0002) and with low Cox-2 score ( P = .01). Our results demonstrate that increased microvessel density and increased Cox-2 expression were linearly related in the canine mammary tumors studied and were also related to worse prognosis and shorter overall survival. This suggests that Cox-2 inhibitors could be an alternative for the treatment and control of advanced neoplastic mammary disease in female dogs.

Immunohistochemical expression of vascular endothelial growth factor and vascular endothelial growth factor receptor in canine cutaneous fibrosarcomas

The expression of five markers associated with tumour angiogenesis, proliferation and apoptosis was studied in 24 canine cutaneous fibrosarcomas. Tumours were assigned histological grades and were immunohistochemically evaluated for the expression of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR-2). Additionally, intra-tumour microvessel density (iMVD) was assessed by immunohistochemical labelling for expression of von Willebrand factor (vWf) and tumour proliferation index (PI) was measured following labelling of Ki-67 antigen. Finally, tumour apoptotic index (AI) was determined by application of the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP end-labelling method (TUNEL). VEGF and VEGFR-2 expression were detected in 22/24 (92%) and 24/24 (100%) of fibrosarcomas, respectively. There was correlation between VEGF and VEGFR-2 expression (r = 0.51) and between histological grade and PI (r = 0.82). A significant difference in PI between tumours of different histological grade was found (P < 0.05). The median PI in grade 2 and 3 tumours (30.6 and 54.7, respectively) was significantly higher than in grade 1 tumours (6.4). Therefore, only PI correlates significantly with the histological grade of canine cutaneous fibrosarcomas. The potential for autocrine activity for VEGF exists in canine cutaneous fibrosarcomas, as VEGF and VEGFR-2 expression was found in most tumours.

Canine mast cell tumours: a review of the pathogenesis, clinical features, pathology and treatment

Mast cells (MCs) are well known for their neoplastic transformation in solitary and multiple cutaneous mast cell tumours (MCTs), as well as visceral and systemic mastocytosis. Dogs have a unique risk of developing cutaneous MCTs, and they account for 7% to 21% of all canine skin tumours. The aetiology of canine MCTs is unknown but is probably multifactorial. This article reviews up-to-date knowledge on the pathogenesis, the clinical presentation, the clinical prognostic factors, the diagnostic workup including clinical staging, cytological findings, histological findings and the various grading systems which have been evaluated based on morphology, the assessment of proliferation markers and other factors such as vessel density. Furthermore, detailed information about current treatment protocols for canine cutaneous MCTs is provided.

Evaluation of microvessel density (MVD) in canine mammary tumours by quantitative immunohistochemistry of the claudin-5 molecule

In our recent investigation, angiogenesis was evaluated and quantified by immunohistochemical evaluation of microvessel density (MVD) using claudin-5 (CLDN-5) as a marker for vascular endothelium in 67 canine mammary gland tumours. Computer image analysis was used to measure the intratumoural MVD. Higher intratumoural MVD was detected in malignant simple neoplasms compared with benign tumours. Furthermore, the results of MVD were correlated with histological grade, higher grades being accompanied by higher MVD. In simple adenomas and grade I tubular-tubulopapillary simple carcinomas the intratumoural microvessels were wide and regular in shape with evident erythrocytes in their lumen. In grade III solid carcinomas the microvessels were smaller, less regular and had irregular shape, often without a distinct lumen, and isolated endothelial cells were frequently present. In the complex carcinomas MVD was low and the intratumoural microvessels were mostly irregular in shape without a distinct lumen. The evaluation of MVD by CLDN-5 immunohistochemistry may give useful additional information on the angiogenic potential of breast cancers in dogs.

Comparison of B-mode and Doppler ultrasonographic findings with histologic features of benign and malignant mammary tumors in dogs

OBJECTIVE

To compare and correlate B-mode and color Doppler ultrasonographic characteristics with the histologic findings of benign and malignant mammary tumors in dogs.

STUDY POPULATION

49 mammary tumors in 26 dogs.

PROCEDURES

Before excision, tumors were evaluated via B-mode and color Doppler ultrasonography to assess size, echogenicity, echopattern, acoustic transmission, invasiveness, and vascularity. Paraffin-embedded microsections of the tumors were stained with H&E and examined for presence of necrosis, cysts, cartilage, bone, mineralization, invasion of surrounding tissue, and tissue heterogeneity. To assess vascularity, the number and distribution of vessels that were stained by the Verhoeff van Gieson technique were recorded.

RESULTS

Tumor echogenicity and echopattern on ultrasonographic images correlated with tissue heterogeneity detected histologically. Acoustic enhancement was correlated with the presence of necrotic or cystic areas. Tumor invasion into surrounding tissues as determined ultrasonographically did not correlate with the histologic findings. There was a significant correlation between the number of detected vessels and distribution of flow within the tumors determined via ultrasonographic and histologic examinations.

CONCLUSIONS AND CLINICAL RELEVANCE

In canine mammary tumors, ultrasonographic characteristics appear to be correlated with histopathologic changes. Data suggest that ultrasonography may have an important role in the evaluation of mammary tumors in dogs, particularly in the evaluation of tissue composition and tumor vascularity.

Mast cells and angiogenesis in canine melanomas: malignancy and clinicopathological factors

The biological significance of mast cells and angiogenesis in canine melanomas is unclear. Eighty canine melanomas (56 malignant and 24 benign), investigated to determine the relationship between mast cell count (MCC), microvessel density (MVD) and clinicopathology, revealed significantly higher MCC and MVD counts in malignant melanomas. Evaluation of the prognostic significance of MCC and MVD in malignant melanomas showed a significant correlation between MCC and MVD both within and at the edges of the tumour. Multivariate analysis indicated that MCC and MVD were independent predictors of survival but the former was a significantly better prognostic marker. Greater numbers of mast cells and microvessels were found in malignant melanomas of poor prognosis. The findings demonstrate a prognostic significance of MCC and MVD in canine melanocytic tumours.

CHARACTERIZATION OF CANINE SUPERFICIAL TUMORS USING GRAY-SCALE B MODE, COLOR FLOW MAPPING, AND SPECTRAL DOPPLER ULTRASONOGRAPHY-A MULTIVARIATE STUDY

Superficial tumors are not routinely evaluated by two- or three-dimensional diagnostic imaging methods as part of the staging of canine cancer patients, although superficial tumors are readily imaged by ultrasound. The objectives of this study were to characterize the ultrasonographic patterns of superficial tumors and to evaluate whether ultrasound can help discriminate between benign and malignant tumors in dogs. Superficial tumors (n=132) in 86 dogs were evaluated by B mode, color flow mapping, and spectral Doppler ultrasonography. Size, echogenicity, tumor border definition, invasiveness, acoustic transmission, presence and distribution of vascular flow to and within the tumor, as well as perfusion indices were measured. The tumors were classified as lipomas, benign tumors, atypical mammary tumors, and malignant tumors. Multivariate statistics using discriminant analysis was used to determine which parameters may be used to predict the status of the tumor. Tumor echogenicity, border shape, acoustic shadowing, total number of vessels to the tumor and the total flow amount are the parameters that in combination resulted in the lowest classification error (24%), meaning that on average three out of four tumors were correctly classified using these parameters. All the lipomas and atypical mammary tumors were classified correctly by ultrasonography. The results of this study show that ultrasonography has an important role in the evaluation of canine superficial tumors, particularly in the evaluation of tissue homogeneity and tumor vascularity.

Prognostic and predictive markers in canine tumours: rationale and relevance. A review

Cancer is one of the most common causes of death in dogs. The availability of multiple treatment modalities and novel therapeutic targets make the correct diagnosis, prognostic stratification, and the identification of treatment effect predictive factors an issue of major debate in cancer management. Selection of high and low risk patients and the type of systemic or local treatment is important in cancer management. The search for better prognostic markers and predictive factors is now focused on the molecular mechanisms which underlie tumour behaviour, such as altered cell cycle progression, proliferation, apoptosis, and angiogenesis. The ultimate goal is to identify reliable markers that can accurately diagnose and stage a tumour and predict tumour's clinical behaviour, prognosis and response to therapy. In this review, the current state of prognostication in canine tumours and promising new molecular markers are discussed. The markers are allocated to four groups according to their function: (i) proliferation markers, (ii) apoptosis, (iii) extracellular matrix and cell adhesion molecules, (iv) angiogenesis and (v) cell cycle regulators. Clinicopathological factors and histopathological grading remain the most practical parameters in decision-making. Although experimental research has shown that molecular markers have a good potential to be used as diagnostic, prognostic or predictive markers in canine tumours, insufficient evidence exists on their efficacy for routine use in veterinary oncology.

Enhancement of the repair of meniscal wounds in the red-white zone (middle third) by the injection of bone marrow cells in canine animal model

Bone marrow stem cells (BMSCs) can differentiate into several cells that participate in the healing of meniscal wounds. To test this hypothesis, we examined the effects of injected BMSCs on the healing of meniscal wounds. Autologous BMSCs from eight adult dogs were injected into meniscal wounds (knee joints). After 12 weeks, the healing process was clinically and immunomorphologically evaluated using: (i) histochemical stains (haematoxylin and eosin, Masson trichrome and periodic acid-Schiff) and (ii) immunoperoxidase staining methods (CD3, CD79a, CD68, CD31 and alpha smooth-muscle actin for T, B lymphocytes, macrophages, endothelial cells and smooth-muscle lineage). Complete (six vs. three), partial (one vs. one) and no healing (one vs. four animals) of the meniscal wounds were observed in the injected and noninjected menisci. As compared with the noninjected menisci, examination of the tissues from the injected ones revealed: (i) marked angiogenesis (microvessel density: 3.22 +/- 0.66 vs. 6.50 +/- 2.10); (ii) chondrogenesis; (iii) prominent immune cell infiltrate (4.07 +/- 0.78 vs. 9.56 +/- 1.69, 8.33 +/- 0.77 vs. 3.67 +/- 1.00 and 4.38 +/- 0.62 vs. 11.1 +/- 1.43 for the total numbers of immune cells, lymphocytes and macrophages, respectively); and (iv) proliferation of the fibroblasts with marked deposition of collagen fibres (2.0 +/- 0.84 vs. 2.66 +/- 0.48). These values were statistically significantly higher for the injected menisci as compared with the noninjected ones (P >/= 0.05). Autologous BMSCs can improve meniscal wound healing. Whether this improvement occurs through BMSC differentiation into cells operational in the repair process, the release of certain mediator or other unknown mechanisms mandates further investigations.

Prognostic value of intratumoral vessel density in cutaneous mast cell tumors of the dog

The biological behaviour of canine cutaneous mast cell tumours (MCTs) is highly variable. The aim of this study was to investigate whether intratumoral microvessel density (IMVD), as an indicator of angiogenesis, was predictive of biological behaviour in MCTs of canine skin, and to relate this parameter to histological grade and other histomorphological features. IMVD was evaluated by immunohistochemical labelling of the endothelial marker factor VIII (Von Willebrand's factor)-related antigen in 32 primary cutaneous MCTs. Computer image analysis was used to measure IMVD, expressed as the number of microvessels per square millimetre. Cases were assigned to low and high vessel density groups, the median value (14.1) being used as the "cut-off". Kaplan-Meier-estimated survival curves of the groups revealed that IMVD was significantly associated with survival time (P=0.046). One-way analysis of variance, performed to compare the IMVD values of tumours of different histological grades, showed a significant difference between grades I and III (P=0.0002). There was a significant difference in IMVD between moderately invasive and highly invasive tumours (P=0.002) and between tumours with different numbers of mitoses (P=0.0046). In multivariate analysis, performed to test the combined influence on survival of each parameter, only the mitotic index and IMVD were independent prognostic variables (P=0.00019). The relation of angiogenesis to biological behaviour and histological parameters of malignancy of cutaneous MCTs was consistent with previous findings in human and animal tumours.

Expression of Vascular Endothelial Growth Factor Receptor Flk-1 in Canine Mammary Tumours

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.

Evaluation of angiogenesis in canine seminomas by quantitative immunohistochemistry

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.

Canine mammary gland tumors

The National Consensus Group recommends that all women with tumors larger than 1 cm be offered chemotherapy regardless of tumor histology of lymph node status. This recommendation is to ensure that everyone at risk for failing, even though the risk may be low in women with relatively small tumors and favorable histology, has a choice and receives the benefit of adjuvant chemotherapy. This type of treatment recommendation may also be made in dogs based on recognized, well-accepted prognostic factors such as tumor size, stage, type, and histologic differentiation. Based on the limited clinical information available in veterinary medicine, the drugs that are effective in human breast cancer, such as cyclophosphamide, 5-fluorouracil, and doxorubicin, may also have a role in the treatment of malignant mammary gland tumors in dogs. Randomized prospective studies are needed, however, to evaluate the efficacy of chemotherapy in dogs with high-risk mammary gland tumors and to determine which drugs and protocols are the most efficacious. Until such studies are performed, the treatment of canine mammary gland tumors will be based on the individual oncologist's understanding of tumor biology, experience, interpretation of the available studies, and a little bit of gut-feeling. Table 2 is a proposal for treatment guidelines for malignant canine mammary gland tumors according to established prognostic factors, results from published veterinary studies, and current recommendations for breast cancer treatment in women.

Correlation of vascular endothelial growth factor expression to overall survival in feline invasive mammary carcinomas

Samples from feline invasive mammary carcinomas (FMCs) were used to determine the prognostic significance of the immunohistochemical expression of vascular endothelial growth factor (VEGF) and microvessel density (MVD). Forty-eight queens bearing FMCs were included in a 2-year follow-up study. Mammary tumors were classified according to the World Health Organization system and graded on the basis of histologic criteria. Tumor sections were immunostained using anti-VEGF and anti-von Willebrand factor (vWf) antibodies. VEGF expression was quantified on the basis of the percentage of positive cells. MVD of vWf-positive microvessels was determined by both mean microvessel counts and highest microvessel counts. Normal mammary gland tissues showed an inconspicuous VEGF staining. In FMCs the proportion of VEGF-positive cells was significantly higher in papillary and solid carcinomas than in tubular and papillary cystic tumors. An increased number of cells expressing VEGF was also observed in poorly differentiated FMCS. Sixteen (33.3%) of the queens bearing invasive carcinomas were still alive at the end of the 2-year follow-up period, and 32 (66.7%) had died. The VEGF expression was significantly correlated with the clinical outcome, but no correlation was observed with the invasion of lymphatic vessels. A correlation between the higher percentage of VEGF-positive cells and the unfavorable prognosis was demonstrated by the estimation of curves for overall survival (P = 0.03). Univariate analysis showed that MVD did not correlate with the overall survival. The results of our study demonstrated that VEGF expression, although not associated with increased angiogenesis, is a prognostic indicator in feline mammary tumors. In contrast, there is no support for a role of neovascularization as an indicator of survivability.

Expression of vascular endothelial growth factor in canine mammary tumors

Vascular endothelial growth factor (VEGF) is a dimeric protein that stimulates angiogenesis in vitro and in vivo by inducing endothelial cell proliferation and migration. In this immunohistochemical study, VEGF-immunolabeled cells were counted in a series of 10 benign and 40 malignant canine mammary tumors. The morphologic pattern of VEGF positivity (intensity of immunolabeling and VEGF granule size and distribution) was also evaluated. A low number of cells weakly positive for VEGF with few and small granules polarized to the luminal pole was detected in benign neoplasms. In contrast, in malignancies a high number of VEGF-positive cells had strong immunolabeling, often with large granules found diffusely in the cytoplasm. This level of immunolabeling was more pronounced in the less differentiated, more malignant phenotypes (grade 3). Macrophages, which can synthesize VEGF, were strongly positive. Stromal and myoepithelial cells were negative. VEGF data were correlated statistically with intratumoral microvessel density (number of newly formed microvessels) and both measures were greater in less differentiated malignant neoplasms, demonstrating that angiogenesis and malignancy increase together. VEGF appears to be a powerful angiogenic factor in canine mammary tumors.

Computer-assisted image analysis of neovascularization in thyroid neoplasms from dogs

OBJECTIVE

To develop a computer-assisted image analysis procedure for quantitation of neovascularization in formalin-fixed paraffin-embedded specimens of thyroid gland tissue from dogs with and without thyroid gland neoplasia.

SAMPLE POPULATION

47 thyroid gland carcinomas, 8 thyroid gland adenomas, and 8 specimens of thyroid tissue from dogs without thyroid gland abnormalities (normal).

PROCEDURE

Serial tissue sections were prepared and stained with antibodies against human CD31 or factor VIII-related antigen (factor VIII-rag). The areas of highest vascularity were identified in CD31-stained sections, and corresponding areas were then identified in factor VIII-rag-stained sections. Image analysis was used to calculate the total vascular density in each section, and neovascularization, expressed as a percentage, was determined as the absolute value of the total vascular density derived from factor VIII-rag-stained sections minus the vascular density derived from CD31-stained sections.

RESULTS

Mean vascular density of thyroid gland carcinomas derived from CD31-stained sections was significantly greater than density derived from factor VII I-rag-stained sections. This incremental difference was presumed to represent degree of neovascularization. However, significant differences were not detected between vascular densities derived from CD31 and factor VIII-rag-stained sections for either normal thyroid gland tissue or thyroid gland adenomas. No significant correlations were found between vascular density in thyroid gland carcinomas and survival time following surgery.

CONCLUSION AND CLINICAL RELEVANCE

A computer-assisted image analysis method was developed for quantifying neovascularization in thyroid gland tumors of dogs. This method may allow identification of dogs with tumors that are most likely to respond to treatment with novel antiangiogenesis agents.

Angiogenesis in squamous cell carcinomas of canine skin: an immunohistochemical and quantitative analysis

In a number of recent papers, the intratumoral microvessel density (iMVD) has been described as a promising new prognostic factor. In this study, the angiogenic rate was evaluated immunohistochemically for platelet endothelial cell adhesion molecule (CD31) in 15 squamous cell carcinomas (SCCs) of canine skin. Computer image analysis was used to measure the iMVD, which increased progressively from differentiation grade I to IV. The iMVD was consistently and significantly greater in the poorly differentiated SCC cases. The correlation of angiogenesis data with differentiation grade of canine SCCs suggests that the iMVD value may provide an additional criterion for evaluating the intrinsic malignancy and growth potential of such tumours.