Molecular subgroups of human malignant peripheral nerve sheath tumors are conserved in canines.

Malignant peripheral nerve sheath tumors (MPNST) are aggressive sarcomas of Schwann cell lineage with poor prognosis in both humans and dogs. While rare in humans, MPNSTs occur more frequently in dogs and share histomorphological and clinical features. Recent methylome and transcriptome analyses have identified two molecular subgroups of human MPNST with distinct oncogenic signaling pathways and prognostic implications; however, it remains unclear if these subgroups also exist in canines. Given their higher incidence and biological similarities to human disease, canine MPNSTs represent a promising comparative model to investigate molecular subtypes and evaluate novel therapeutic strategies. To characterize canine MPNST and assess molecular parallels with the human subgroups, we applied laser-capture microdissection (LCM) followed by RNAsequencing to analyze tumor tissue from 20 canine MPNST. Principle component and differential gene expression analyses identified two clearly distinct transcriptional clusters corresponding to spindle cell and epithelioid MPNST variants, respectively. Unsupervised cross-species comparison aligned the two canine clusters with the human G1 and G2 subgroups. Accordingly, one cluster was characterized by SHH pathway activation and increased cell cycle activity, while the other showed non-canonical WNT pathway, Schwann cell-like features and marked macrophage infiltration. Immunohistochemistry further demonstrated loss of H3K27me3, p-ERK activation and β-catenin signaling by IHC in a subset of tumors. These findings support the value of canine MPNST as clinically amenable model for structured assessment of novel therapeutic approaches to benefit patients of both species.