Evaluation of selected growth factor expression in canine spirocercosis (Spirocerca lupi)-associated non-neoplastic nodules and sarcomas

Cancerogenic parasites in veterinary medicine: a narrative literature review

Parasite infection is one of the many environmental factors that can significantly contribute to carcinogenesis and is already known to be associated with a variety of malignancies in both human and veterinary medicine. However, the actual number of cancerogenic parasites and their relationship to tumor development is far from being fully understood, especially in veterinary medicine. Thus, the aim of this review is to investigate parasite-related cancers in domestic and wild animals and their burden in veterinary oncology. Spontaneous neoplasia with ascertained or putative parasite etiology in domestic and wild animals will be reviewed, and the multifarious mechanisms of protozoan and metazoan cancer induction will be discussed.

Spirocerca lupi Proteomics and Its Role in Cancer Development: An Overview of Spirocercosis-Induced Sarcomas and Revision of Helminth-Induced Carcinomas

Spirocerca lupi is a parasitic nematode of canids that induces a myriad of clinical manifestations in its host and, in 25% of infections, leads to the formation of sarcomas. The description of the protein composition of the excretory and secretory products (Sl-ESP) of S. lupi has shed light on its possible interactions with the host environment, including migration within the host and mechanisms of immunomodulation. Despite this, the process by which S. lupi induces cancer in the dog remains poorly understood, and some hypotheses have arisen regarding these possible mechanisms. In this review, we discuss the role of specific ESP from the carcinogenic helminths Clonorchis sinensis, Opisthorchis viverrini and Schistosoma haematobium in inducing chronic inflammation and cancer in their host’s tissues. The parasitic worms Taenia solium, Echinococcus granulosus, Heterakis gallinarum, Trichuris muris and Strongyloides stercoralis, which have less-characterized mechanisms of cancer induction, are also analyzed. Based on the pathological findings in spirocercosis and the mechanisms by which other parasitic helminths induce cancer, we propose that the sustained inflammatory response in the dog´s tissues produced in response to the release of Sl-ESP homologous to those of other carcinogenic worms may lead to the malignant process in infected dogs.

Expression of angiogenic growth factors in canine squamous cell cancers

Skin and subcutaneous tissue tumors are the most common neoplasms in dogs. The most common sites of origin in dogs include digits, skin and the oral cavity including cheek and retromandibular area. We investigated canine squamous cell carcinoma (SCC) samples from 15 dogs and classified them histopathologically according to the degree of differentiation. bFGF, VEGF-C, TGF-β, PDGF-A, PDGF-C and PDGFR-α expressions were assessed using immunohistochemistry to determine the roles of growth factors during SCC. We found that TGF-β1 immunolabeling was elevated significantly compared to healthy controls in SCC originating from nailbeds, while expression of other growth factors did not change significantly. Our findings might explain the role of TGF-β1 in the infiltrative and malignant behavior of SCC originating from nailbeds.

Insights on Spirocerca lupi, the Carcinogenic Dog Nematode

Spirocerca lupi is a nematode transmitted by dung beetles that infects domestic and wild canids in tropical and subtropical regions and is associated with neoplasia. It produces a distinctive pathology with the formation of esophageal nodules classified as inflammatory, preneoplastic, or neoplastic with metastasis to distant organs. Aberrant central nervous system migration of this nematode is also responsible for severe neurological manifestations. Reports of spirocercosis have increased over the last two decades showing spread of this canine helminth in five continents. S. lupi from different geographical locations is genetically distinct with two genotypes, genotype I from Africa, Asia, and Australia, and genotype II from Europe, and recently separated from Spirocerca vulpis, a new species described in red foxes from Europe.

Tyrosine Kinase Receptor Expression in Canine Liposarcoma

The expression of tyrosine kinase receptors is attracting major interest in human and veterinary oncological pathology because of their role as targets for adjuvant therapies. Little is known about tyrosine kinase receptor (TKR) expression in canine liposarcoma (LP), a soft tissue sarcoma. The aim of this study was to evaluate the immunohistochemical expression of the TKRs fibroblast growth factor receptor 1 (FGFR1) and platelet-derived growth factor receptor–β (PDGFRβ); their ligands, fibroblast growth factor 2 (FGF2) and platelet-derived growth factor B (PDGFB); and c-kit in canine LP. Immunohistochemical labeling was categorized as high or low expression and compared with the mitotic count and MIB-1–based proliferation index. Fifty canine LPs were examined, classified, and graded. Fourteen cases were classified as well differentiated, 7 as myxoid, 25 as pleomorphic, and 4 as dedifferentiated. Seventeen cases were grade 1, 26 were grade 2, and 7 were grade 3. A high expression of FGF2, FGFR1, PDGFB, and PDGFRβ was identified in 62% (31/50), 68% (34/50), 81.6% (40/49), and 70.8% (34/48) of the cases, respectively. c-kit was expressed in 12.5% (6/48) of the cases. Mitotic count negatively correlated with FGF2 ( R = –0.41; P < .01), being lower in cases with high FGF2 expression, and positively correlated with PDGFRβ ( R = 0.33; P < .01), being higher in cases with high PDGFRβ expression. No other statistically significant correlations were identified. These results suggest that the PDGFRβ-mediated pathway may have a role in the progression of canine LP and may thus represent a promising target for adjuvant cancer therapies.

Recommendations for Health Monitoring and Reporting for Zebrafish Research Facilities

The presence of subclinical infection or clinical disease in laboratory zebrafish may have a significant impact on research results, animal health and welfare, and transfer of animals between institutions. As use of zebrafish as a model of disease increases, a harmonized method for monitoring and reporting the health status of animals will facilitate the transfer of animals, allow institutions to exclude diseases that may negatively impact their research programs, and improve animal health and welfare. All zebrafish facilities should implement a health monitoring program. In this study, we review important aspects of a health monitoring program, including choice of agents, samples for testing, available testing methodologies, housing and husbandry, cost, test subjects, and a harmonized method for reporting results. Facilities may use these recommendations to implement their own health monitoring program.

Growth Factors and COX2 Expression in Canine Perivascular Wall Tumors

Canine perivascular wall tumors (PWTs) are a group of subcutaneous soft tissue sarcomas developing from vascular mural cells. Mural cells are involved in angiogenesis through a complex crosstalk with endothelial cells mediated by several growth factors and their receptors. The evaluation of their expression may have relevance since they may represent a therapeutic target in the control of canine PWTs. The expression of vascular endothelial growth factor (VEGF) and receptors VEGFR-I/II, basic fibroblast growth factor (bFGF) and receptor Flg, platelet-derived growth factor B (PDGFB) and receptor PDGFRβ, transforming growth factor β1 (TGFβ1) and receptors TGFβR-I/II, and cyclooxygenase 2 (COX2) was evaluated on frozen sections of 40 PWTs by immunohistochemistry and semiquantitatively scored to identify their potential role in PWT development. Statistical analysis was performed to analyze possible correlations between Ki67 labeling index and the expression of each molecule. Proteins of the VEGF-, PDGFB-, and bFGF-mediated pathways were highly expressed in 27 (67.5%), 30 (75%), and 19 (47.5%) of 40 PWTs, respectively. Proteins of the TGFβ1- and COX2-mediated pathways were highly expressed in 4 (10%) and 14 (35%) of 40 cases. Statistical analysis identified an association between VEGF and VEGFR-I/II (P = .015 and .003, respectively), bFGF and Flg (P = .038), bFGF and PDGFRβ (P = .003), and between TGFβ1 and COX2 (P = .006). These findings were consistent with the mechanisms that have been reported to play a role in angiogenesis and in tumor development. No association with Ki67 labeling index was found. VEGF-, PDGFB-, and bFGF-mediated pathways seem to have a key role in PWT development and growth. Blockade of tyrosine kinase receptors after surgery could represent a promising therapy with the aim to reduce the PWT relapse rate and prolong the time to relapse.

Triple phase dynamic computed tomographic perfusion characteristics of spirocercosis induced esophageal nodules in non-neoplastic versus neoplastic canine cases

Neoplastic transformation of Spirocerca lupi induced esophageal nodules carries a poor prognosis. Clinical, clinicopathological, endoscopic, and radiographic characteristics may be indicative of neoplastic transformation but variable sensitivity and specificity of these parameters makes their use questionable. We hypothesized that CT would be a better diagnostic modality to discriminate between non-neoplastic and neoplastic nodules. In this prospective study of 38 dogs, the appearance and perfusion characteristics of confirmed spirocercosis-induced neoplastic and non-neoplastic esophageal nodules were described using survey CT and triple phase dynamic CT angiography (CTA). Pre- and post-contrast early arterial, late arterial, and venous CTA images were evaluated. Non-neoplastic nodules were smooth and nonmineralized with a higher proportion of hypoattenuating necropurulent cavities compared to neoplastic nodules that had a more irregular surface, with 93% having mineralized foci and rarely any hypoattenuating pockets. Non-neoplastic nodules were significantly more perfused than neoplastic nodules with the difference being up to 23 Hounsfield units. The difference was most marked in the early and late arterial phases (P = 0.0005 and 0.00005, respectively). Ratios of the normal esophagus adjacent to the neoplastic and non-neoplastic nodules did not differ significantly from each other. Perfusion findings demonstrated relative hypoperfusion of the esophageal sarcomas. Findings from the current study indicated that CT characteristics of relative postcontrast hypoperfusion, combined with nodule irregularity and mineralization warrant a high level of concern for neoplastic transformation in canine spirocercosis-induced esophageal nodules.

Vascular endothelial growth factor concentrations in dogs with spirocercosis

BACKGROUND

Vascular endothelial growth factor (VEGF) is a potent proangiogenic factor associated with tumor development. Spirocerca lupi is a nematode of canids that induces an esophageal nodule that progresses to a sarcoma in 25% of cases. Determination of neoplastic transformation is challenging and usually based on endoscopy-guided biopsies under general anesthesia, an expensive procedure that often yields nondiagnostic, necrotic samples.

HYPOTHESIS

Circulatory VEGF concentrations are increased in dogs with neoplastic spirocercosis and can distinguish between dogs with neoplastic and nonneoplastic disease.

ANIMALS

A total of 24 client-owned dogs, 9 nonneoplastic, 9 neoplastic, and 6 controls.

METHODS

Case-control study. Plasma and serum VEGF concentrations at the time of diagnosis were compared with those of healthy controls. Measurement of VEGF was performed using a canine-specific ELISA. Kruskal-Wallis and Dunn's tests were used for statistical analysis with significance set at P < .05.

RESULTS

The median plasma VEGF concentrations of dogs with neoplastic spirocercosis were 629 pg/mL (range, 282-2,366) higher than both the nonneoplastic (<39.5 pg/mL; range, <39.5-716) and control dogs (<39.5 pg/mL; all values, <39.5; P = .0003). The median serum VEGF concentration of the neoplastic dogs was 69 pg/mL (range, <39.5-212) higher than the nonneoplastic (<39.5 pg/mL; range, <39.5-44.13) and control dogs (<39.5 pg/mL; all values, <39.5; P = .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Both plasma and serum VEGF concentrations can be used to differentiate nonneoplastic and neoplastic spirocercosis. The role of VEGF in neoplastic transformation of S. lupi-induced nodules and the potential utility of anti-VEGF drugs in spirocercosis-induced sarcoma warrant further investigation.

Spirocerca lupi-associated vertebral changes: a radiologic-pathologic study

Spirocerca lupi causes a caudal esophageal mass in dogs which may be accompanied by aortic changes and caudal thoracic spondylitis. Previous literature hypothesized that the spondylitis was caused by either aberrant larval migration or was secondary to the inflammation caused by the aortic migration. The current study aimed to evaluate these hypotheses. Ten dogs of various breeds and ages with radiographic evidence of spondylitis, which were necropsied, had the affected vertebrae removed and prepared for light and transmission electron microscopy examination. Transverse and sagittal sections of the ventral vertebrae were taken from 27 spondylitis and 8 spondylosis deformans lesions as well as from 8 normal vertebrae. Early spondylitis changes were characterized by periosteal woven new bone covered by hyperplastic periosteum with some involvement of the ventral longitudinal ligament. More mature lesions were characterized by nodules of denser trabecular bone and cartilage, also covered by hyperplastic periosteum and involved the ventral longitudinal ligament. It was difficult to distinguish the spondylitis and spondylosis deformans new bone. Inflammation was seen in five spondylitis cases (edema, lymphocytes, plasma cells, eosinophils and fibrin fibers). Spirocerca eggs were seen in one histologic section. This study shows that inflammation is mild and inconsistent in spirocercosis-induced spondylitis and that aberrant migration of the larvae or adults did not appear to be a predominant cause. Inflammatory mediators or osteoproliferative growth factors, which may be related to the primary esophageal lesion or to the worm itself, could be involved. This requires further investigation.

Pneumoesophagography and the appearance of masses in the caudal portion of the esophagus in dogs with spirocercosis

OBJECTIVE

To determine the usefulness of pneumoesophagography, compared with that of survey radiography, for characterization of esophageal pathological changes in dogs with endoscopically confirmed intraluminal Spirocerca lupi nodules in the caudal portion of the esophagus.

DESIGN

Diagnostic test evaluation.

ANIMALS

30 dogs with endoscopically confirmed spirocercosis.

PROCEDURES

Dorsoventral (DV) and right lateral recumbent (RLR) thoracic survey radiographs were obtained for each dog. Endoscopy was subsequently performed, the esophagus was inflated with air, and left lateral recumbent, RLR, DV, and ventrodorsal thoracic radiographs were obtained. The amount of esophageal and gastric distention was recorded. Visibility, location, and surface characteristics of lesions and total length of esophageal involvement were recorded independently for each radiograph and modality and compared with each other.

RESULTS

Survey DV radiographs were more reliable than survey RLR radiographs for detecting caudal esophageal pathological changes. Lateral pneumoesophagograms showed more esophageal air and had more visible nodules than did their orthogonal counterparts. Right lateral recumbent pneumoesophagograms allowed for evaluation of the air-filled stomach, particularly the cardiac portion, for additional pathological changes. Pneumoesophagography allowed the mural position (47% located dorsally) and surface characteristics of Spirocerca nodules to be determined. Six of 9 dogs with confirmed malignant disease had an irregular nodule surface suggestive of neoplastic transformation.

CONCLUSIONS AND CLINICAL RELEVANCE

Pneumoesophagography was easily performed in dogs with spirocercosis and showed promise as a cost-effective and safe initial diagnostic procedure for further evaluation and characterization of suspected caudal esophageal lesions.