A Scoping Review on Tyrosine Kinase Inhibitors in Cats: Current Evidence and Future Directions

Tyrosine kinase inhibitors (TKIs) have become invaluable in the treatment of human and canine malignancies, but their role in feline oncology is less defined. While toceranib phosphate and masitinib mesylate are licensed for use in dogs, no TKI is yet approved for cats. This review systematically maps the research conducted on the expression of tyrosine kinases in neoplastic and non-neoplastic domestic feline tissues, as well as the in vitro/in vivo use of TKIs in domestic cats. We identify and discuss knowledge gaps and speculate on the further research and potential indications for TKI use in cats. A comprehensive search of three electronic databases and relevant paper reference lists identified 139 studies meeting the inclusion criteria. The most commonly identified tumors were mast cell tumors (MCTs), mammary and squamous cell carcinomas and injection-site sarcomas. Based on the current literature, toceranib phosphate appears to be the most efficacious TKI in cats, especially against MCTs. Exploring the clinical use of TKIs in mammary carcinomas holds promise. Despite the progress, currently, the evidence falls short, underscoring the need for further research to discover new indications in feline oncology and to bridge the knowledge gaps between human and feline medicine.

Feline Soft Tissue Sarcomas: A Review of the Classification and Histological Grading, with Comparison to Human and Canine

Simple Summary

Soft tissue sarcomas are a common form of cancer arising in the skin and connective tissues of domestic cats. Soft tissue sarcomas encompass a group of different histological subtypes of tumours, which can behave in a range of different ways in the patient. In dogs and in humans, this group of tumours can be given a histological score (“grade”) at the time of diagnosis, which is prognostic, but there is no equivalent, well-established grading system for these tumours in cats. This review looks at soft tissue sarcomas in terms of which histological subtypes of tumour should be included in this group, and how pathologists approach their grading, comparing feline tumours with their human and canine counterparts.

Abstract

Soft tissue sarcomas are one of the most commonly diagnosed tumours arising in the skin and subcutis of our domestic cats, and are malignant neoplasms with a range of histological presentations and potential biological behaviours. However, unlike their canine and human counterparts, there is no well-established histological grading system for pathologists to apply to these tumours, in order to provide a more accurate and refined prognosis. The situation is further complicated by the presence of feline injection site sarcomas as an entity, as well as confusion over terminology for this group of tumours and which histological types should be included. There is also an absence of large scale studies. This review looks at these tumours in domestic cats, their classification and histological grading, with comparisons to the human and canine grading system.

Feline injection site sarcoma: immunohistochemical characteristics

OBJECTIVES

Feline injection site sarcoma (FISS) is a rapid growing locally aggressive tumor with a low metastatic rate. Its histologic features are clearly defined, but there are few studies regarding its immunohistochemical characteristics. The present study investigated the immunohistochemical characteristics of 21 cases of FISS.

METHODS

FISSs from 12 male and nine female cats, 20 mixed-breed and one Siamese, were included in the study. After histopathological diagnosis, additional histologic sections were immunostained for vimentin, cytokeratin, desmin, S100 protein, viral feline leukemia virus (FeLV) particles, cyclooxygenase 2 (COX-2) and c-KIT. Positive and negative controls were adopted accordingly. Immunostainings were classified as positive or negative according to the number of positive cells from a total of 1000 cells per tumor section.

RESULTS

Histopathologic diagnosis of the tumors revealed 18 (85.7%) fibrosarcomas and three (14.3%) other sarcomas; four fibrosarcomas (22.2%) were grade III, five (27.8%) were grade II and nine (50.0%) were grade I. Two sarcomas were grade III and one was grade II. Seventeen (81%) tumors were negative for desmin. All samples were positive for vimentin. Twenty tumors (95.2%) were positive for S-100 protein. Positivity for c-KIT was observed in four (19%) samples; COX-2 was positive in 13 (61.9%) and FeLV viral particles were positive in nine (42.9%) FISSs.

CONCLUSIONS AND RELEVANCE

Immunohistochemical findings of FISSs revealed positive immunostainings for desmin, vimentin, S-100 protein, c-KIT, COX-2 and FeLV viral particles.

Disodium Cromolyn and Anti-podoplanin Antibodies Strongly Inhibit Growth of BHK 21/C13-derived Fibrosarcoma in a Chick Embryo Chorioallantoic Membrane Model

AIM

To characterize baby hamster kidney fibroblast (BHK 21/C13) cells and test the effects of antibodies against podoplanin and disodium cromolyn on BHK 21/C13 cell line-derived tumors grown on chick embryo chorioallantoic membrane (CAM).

MATERIAL AND METHODS

BHK 21/C13 cell-derived fibrosarcomas developed in hamsters were implanted on CAM and treated with anti-podoplanin antibodies and disodium cromolyn. BHK 21/C13 cell immunophenotype was assessed.

RESULTS

Fibrosarcoma cells were positive for vimentin, CD117, smooth muscle actin, vascular endothelial growth factor epidermal growth factor receptor, homebox prospero gene 1 and negative for platelet-derived growth factor B, neuron-specific enolase, S100, CD34, Ewing sarcoma and podoplanin. CAM-grown fibrosarcomas were highly sensitive to disodium cromolyn and anti-podoplanin antibodies.

CONCLUSION

Immunophenotyping BHK 21/C13 cells and their response to drugs represent the first step in revealing cell line utility and a reliable tool for experimental cancer research.

Cytogenomics of Feline Cancers: Advances and Opportunities

Relative to the dog, integration of the cat into the “One Health” concept has been more restricted, particularly in the field of molecular oncology. Beyond the continual need to enhance the sophistication of feline healthcare per se, the unique spectrum of naturally-occurring cancers in the cat offers tremendous opportunities for comparative and translational advances that may have mutual benefit for human and veterinary medicine. The study of feline cancers additionally may generate new insight into underexplored aspects of tumor biology that are less accessible in other species, such as the relationship between chronic inflammation and neoplasia, and the role of viruses in malignant transformation. Several factors that have hindered molecular studies of feline cancers have now been surmounted, with the most fundamental step forward coming from the development of a high-quality reference genome sequence assembly for the cat. This article reviews landmark studies that have led to our current appreciation of feline genome architecture, and outlines techniques used in cancer cytogenomics, from conventional karyotyping analysis through to the development of genomic microarrays and beyond. A summary of progress in the identification and characterization of chromosomal aberrations in feline cancers is provided using examples from studies of injection-site sarcomas, lymphomas and mammary tumors.

Clinical outcome, PDGFRβ and KIT expression in feline histiocytic disorders: a multicentre study

Information about histiocytic disease in cats is limited. The aim of this study was to document clinical findings and outcome in feline histiocytic disorders, and characterize the expression of PDGFRβ and KIT in order to identify potential treatment targets. Morphologically diagnosed feline histiocytic tumours were reviewed and characterized by immunohistochemistry (IHC). Five cases of feline progressive histiocytosis (FPH), eight histiocytic sarcomas (HS) and two haemophagocytic histiocytic sarcomas (HaeHS) were confirmed. PDGFRβ was variably positive in most histiocytic cases, while KIT was negative in all. Clinical presentation, treatment and outcome were also evaluated. Partial responses were recorded in measurable disease with tyrosine kinase inhibitors and lomustine, and radiotherapy achieved long-term control in some cases. Survival times were shortest in HaeHS and disseminated disease. PDGFRβ, but not KIT, may represent a therapeutic target in feline histiocytic disorders but more studies are needed to investigate other potential treatment targets.