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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The c-kit receptor is responsible for transmission of promigration signals to melanocytes; its downregulation may be involved in malignant progression of human melanocytic neoplasms. Expression of this receptor has not been examined in normal or neoplastic melanocytes from dogs. In this study, 14 benign dermal and 61 malignant mucosal melanocytic tumors were examined for c-kit (KIT) expression. Sites of the mucosal melanomas were gingiva (not further specified; n = 30), buccal gingiva (n = 6), soft palate (n = 4), hard palate (n = 5), tongue (n = 7), lip (n = 6), and conjunctiva (n = 3). Melan A was expressed in all 14 dermal melanocytomas and in 59 of 61 (96.7%) tumors from oral or conjunctival mucosa, confirming melanocytic origin. C-kit receptor expression was strong and diffuse throughout the cytoplasm in all 14 dermal melanocytomas and was identified in basilar mucosal melanocytes over submucosal neoplasms (27 of 61, 44.3%), junctional (neoplastic) melanocytes (17 of 61, 27.9%), and, less commonly, neoplastic melanocytes of the subepithelial tumors (6 of 61, 9.8%). KIT expression anywhere within the resected melanomas correlated with significantly longer survival. These results suggest that c-kit receptor expression may be altered in canine melanomas and may have potential as a prognostic indicator for mucosal melanomas. [ABSTRACT FROM PUBLISHER]