Receptor Tyrosine Kinase Expression Profiles in Canine Cutaneous and Subcutaneous Mast Cell Tumors

Abstract

The receptor tyrosine kinase (RTK) KIT is a major focus of current research into canine mast cell tumors (MCTs). Little is known about the role of other RTKs, such as vascular endothelial growth factor receptors (VEGFRs) and platelet-derived growth factor receptors (PDGFRs). These RTKs are dysregulated in many human and animal cancers and are key regulators of tumor angiogenesis. The aims of this study were to assess the expression and activation (phosphorylation) status of KIT, VEGFR2, and PDGFR (α and β) in canine MCTs and to examine associations with various clinical outcomes. c-KITmutational status and KIT cellular localization pattern were also evaluated for these tumors. Twenty-seven MCTs, consisting of 5 subcutaneous and 22 cutaneous tumors, from 25 dogs were evaluated. MCT biopsies, cultured mast cells, and skin from the surgical margin were analyzed through Western blotting. MCT biopsies were also used for KIT immunohistochemical labeling and polymerase chain reaction for c-KITmutational analysis. MCT had heterogeneous expression profiles for all 3 RTKs, which varied in intensity and activation status. Statistical analyses showed phosphorylated KIT, VEGFR2, and KIT cellular localization to be predictive of decreased survival time, disease-free interval, and increased metastatic rate. Expression of VEGFR2 and KIT diffuse cytoplasmic labeling were also significantly associated with increased rate of local recurrence. The results of the study show that phosphorylated KIT, KIT, VEGFR2, and PDGFRβ, in addition to KIT localization, may be valuable prognostic determinants in MCTs and should be further studied to improve diagnostic and therapeutic modalities.

Use of neutrophil to lymphocyte ratio for predicting histopathological grade of canine mast cell tumours

“…A two-tiered (Kiupel and others 2011) and a three-tiered grading system (Patnaik and others 1984) are both currently used. Numerous histopathological proliferation indices and markers have also been utilised in attempt to better determine the biological behaviour of a MCT: argyrophilic nucleolar-organising regions (Bostock and others 1989, Scase and others 2006, Webster and others 2007, 2008), B-cell lymphoma 2 (BCL-2) gene and protein expression (Vascellari and others 2013), Ki-67 (Abadie and others 1999, Scase and others 2006, Ozaki and others 2007, Webster and others 2007, 2008, Maglennon and others 2008), KIT staining pattern, presence of mutations in KIT or alterations in other receptor tyrosine kinases (Zemke and others 2002, Kiupel and others 2004, Webster and others 2007, 2008, Thompson and others 2015), minichromosome maintenance protein 7 (Berlato and others 2012), mitotic index (Bostock and others 1989, Sakai and others 2002, Elston and others 2007, Romansik and others 2007, Vascellari and others 2013, Van Lelyveld and others 2015), tumour suppressor in lung cancer 1 (Taylor and others 2010) and combinations of multiple markers or indices (Simoes and others 1994, Séguin and others 2006). …”

Pilot assessment of vascular endothelial growth factor receptors and trafficking pathways in recurrent and metastatic canine subcutaneous mast cell tumours

“…VEGFR2 and pVEGFR2 antibodies identified a major band at approximately 250 kDa, and minor bands of slightly lower molecular weight, as has been reported for human and canine neoplastic cells (Adham & Coomber ; Thompson et al . ). The c‐CBL blots showed a single specific band of approximately 100 kDa (Feshchenko et al .…”

“…Our results are also in line with a recent study that reported VEGFR2 expression (detected via western blot) in neoplastic cells isolated from some canine cutaneous and subcutaneous MCT (Thompson et al . ). These findings may help explain the success of KIT directed TKIs in tumours that lack mutated KIT (London et al .…”

“…; Thompson et al . ) and mast cell tumour cells express both VEGF ligand and VEGFRs (Sekis et al . ) although whether autocrine signalling pathways are active in mast cell tumours is controversial.…”

“…The KIT protein, encoded by the proto-oncogene c-KIT, stimulates the proliferation, maturation and activation of normal mast cells (Yavuz et al 2002). Its role in subcutaneous MCT is less well understood (Thompson et al 2011a(Thompson et al , 2016.…”