Comparative Phenotypic and Molecular Characterisation of Feline Oral Squamous Cell Carcinoma Cell Lines Reveals Marked Biological Heterogeneity.

Feline oral squamous cell carcinoma (FOSCC) is the most common oral malignancy, characterised by aggressive local invasion, frequent bone involvement, and poor prognosis. The limited availability of well-characterised in vitro models has hindered the understanding of tumour heterogeneity and invasive behaviour. This study aimed to establish and comparatively characterise a panel of FOSCC cell lines derived from tumours with and without documented bone invasion to identify intrinsic biological differences. Four FOSCC cell lines were evaluated for epithelial identity, growth kinetics, clonogenicity, migratory capacity and chemosensitivity. All cell lines retained epithelial characteristics, with consistent expression of epithelial markers; however, variation in cytokeratin-19 and vimentin suggested phenotypic heterogeneity and partial epithelial-mesenchymal plasticity. The cell lines demonstrated distinct proliferation rates, doubling times, and clonogenic capacities. Morphologically, these cells displayed varying degrees of peripheral filopodial activity. Functional assays further revealed substantial migratory capacity under both serum-supplemented and serum-free conditions, with differences across cell lines. Chemosensitivity profiling showed heterogeneous responses to targeted and cytotoxic agents, highlighting cell line-specific differences in drug susceptibility and potential intrinsic drug responsiveness. These findings demonstrate that FOSCC cell lines possess distinct biological properties consistent with phenotypic differences. The observed heterogeneity underscores the potential relevance of tumour origin in shaping functional behaviour and highlights the value of using multiple, well-characterised cell line models to better represent disease diversity. This study provides a comprehensive comparative characterisation of four FOSCC cell lines, including a newly established model, and establishes a baseline resource for future mechanistic and translational investigations in feline and comparative oncology.