Login to Access Video or Poster Abstract: MP60-06
Sources of Funding: None.

Introduction

We previously reported that high MET and matriptase expression in RCC cells in bone metastasis indicates their importance in bone metastasis (Mukai et al. Hum Cell, 2015). MET is a high-affinity receptor tyrosine kinase of hepatocyte growth factor (HGF). HGF is secreted as an inactive single-chain precursor, which requires proteolytic activation for conversion to an active form. Matriptase is the most efficient known cellular activator of pro-HGF. Furthermore, activation of matriptase is regulated by HGF activator inhibitor (HAI). In this study, we employed a previously reported mouse model of bone metastasis (Strube et al. Clin Exp Metastasis, 2010) to clarify the significance of the matriptase-induced HGF/MET signaling axis in RCC bone metastasis.

Methods

Luciferase-transfected 786-O cells were injected into the left cardiac ventricle of female nude mice (5 weeks old). After 6 weeks, we confirmed the formation of bone metastasis by whole-body bioluminescent imaging, and extracted specimens. Expression of matriptase, MET and HAI was analyzed by PCR, immunohistochemistry (IHC) and immunoblots. Phosphorylation of MET was also investigated. Based on the result, we produced HAI-2 (specific inhibitor of matriptase) stable knock down (KD) 786-O cells, and analyzed the difference of expression in each molecule, cell-migration assay and invasion assay.

Results

Expression of matriptase was increased significantly in bone metastasis compared with parent cell line, and we confirmed increased phosphorylation of MET in bone metastasis. On the other hand, decreased expression of HAI-2 was observed in bone metastasis. Interestingly, increased matriptase expression was observed by HAI-2 KD in 786-O cells. In addition, invasive activity was increased significantly by knock down of HAI-2.

Conclusions

These results have suggested that matriptase contributes to the HGF-dependent MET activation in the pericellular microenvironment of bone metastasis in RCC. In addition, upregulation of matriptase and downregulation of HAI-2 may have important roles in their progression.

Funding

None.