Spatial Transcriptomic Landscape of Canine Oral Squamous Cell Carcinoma.

Canine oral squamous cell carcinoma (COSCC) is the second most common oral tumor in dogs and the most relevant for comparative human trials as a spontaneous large animal model of disease. Historical genomic work has focused primarily on bulk sequencing. The present study describes the complete transcriptomic landscape of COSCC with spatial distinction between the surface tumor, deep invasive tumor, peritumoral dysplastic epithelium, and tumor microenvironment compared to matched normal oral samples. Each region demonstrated distinct molecular signatures. Genes related to epithelial growth factor (EGFR) and epithelial-mesenchymal transformation (EMT) were upregulated in both peritumoral dysplasia and surface cancer. Additionally, the KRAS gene set, KRT17, and SSP1 were enriched in cancer. We identified five genes that represent dysplastic lesion with high potential for malignant transformation (FZD4, GAS1, HACD2, NOG, and SLC39A6). Also, three genes, SFRP4, FZD1, and IL34 represented a specific signature of the invasive portion of the COSCC that should be explored for prognostic value as a biomarker of malignancy. Lastly, we verified the immunomodulatory tumor microenvironment detecting an increase in macrophages and an abundance of IL-10 secretion. The other predominant leukocytes were T-cells, with CD4+ T-cells being the most prevalent. CD4+ T cells expressed transcripts for both stimulatory (Inducible T-cell Co-Stimulator (ICOS) and inhibitory molecules (CTLA4). The observed high CTLA4 suggests that this inhibitory signal may be preventing a robust antitumor immune response. Taken together, this study identified multiple targets to be explored for biomarkers of malignancy, prediction of tumor behavior, and potential targets for development of novel therapies.