Molecular Classification Based on the Gene Expression Profiles in Canine Histiocytic Sarcoma Cells

The molecular abnormalities of canine histiocytic sarcoma (CHS) remain to be elucidated. We previously revealed that the sensitivities to dasatinib and trametinib were significantly various among CHS cell lines, indicating the differences in underlying molecular abnormalities. In the present study, we performed RNA sequencing analysis using 11 CHS cell lines to investigate molecular classifications based on the gene expression profiles (GEPs). The clustering analysis showed that CHS cell lines were divided into two distinct clusters. The comparisons of GEPs between the clusters extracted 675 differentially expressed genes (DEGs), and these DEGs were enriched with those related to the regulations of inflammatory responses. Among these DEGs, differences in the expressions of CCL3, CCL4, CCL7, CLEC7A, and TLR4 genes between the two groups were confirmed by RT-qPCR. Since no significant difference in the activation status of Akt and ERK pathways was observed between the two groups, the NF-κB pathway was focused on and its activation status was examined in the cell lines. As a result, cell lines belonging to one cluster showed nuclear translocation of the p65 protein together with increased release of CCL5 protein, which is a target molecule of the NF-κB pathway, in a cell culture supernatant. These results suggested that the molecular pathology of CHS cells might be divided into two categories depending on the activation status of the NF-κB pathway, and it is necessary to establish precision medicine for each molecular subtype of CHS.