Introduction

To identify novel molecular targets for chemotherapy in canine histiocytic sarcoma (HS) using next generation sequencing.

Methods

Tumor samples obtained from dogs suffered from HS were subjected to whole exome sequencing (WES) (8 samples) and RNA-sequencing (4 samples). With respect to a candidate molecule, FGFR1, its relative mRNA expression level was compared between HS tumor samples and normal monocytes. Expression of FGFR1 protein was also examined by immunohistochemistry using 13 samples. Finally, effects of FGFR1 inhibitors were examined in cultured canine HS cell lines.

Results

In WES, 39 gene mutations were identified, and pathway analysis using these genes revealed that gene mutations were significantly concentrated in PI3K-Akt and ERK1/2 pathways. Based on these observations, we investigated the expression levels of receptor tyrosine kinases (RTKs) using the data of RNA-sequencing, leading to a finding that FGFR1 mRNA expression level was higher than those of other RTKs in HS tumor tissues. In addition, FGFR1 mRNA level was significantly higher in HS tumor cells than normal monocytes. Immunohistochemistry revealed the expression of FGFR1 in tumor tissues from all of the 13 dogs examined. Finally, treatment with FGFR1 inhibitors induced cell cycle arrest, increase of apoptosis, and inhibition of proliferations in 3 canine HS cell lines.

Conclusions

The intracellular signaling from FGFR1 and mutations of genes associated with the regulations of PI3K-Akt and ERK1/2 pathways might be involved in the pathogenesis of canine HS.

Clinical Significance of the Results

FGFR1 might be a novel molecular target for chemotherapy in canine HS.