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Cabozantinib is known as an inhibitor of receptor tyrosine kinases mainly targeting AXL receptor tyrosine kinase (AXL), MET proto-oncogene-encoded receptor tyrosine kinase (MET), and vascular endothelial growth factor receptor 2. Growth arrest-specific 6 (GAS6) and hepatocyte growth factor (HGF), the natural ligands of AXL and MET, respectively, are associated with the induction of cancer cell proliferation or metastasis. Currently, it is still unclear how cabozantinib regulates cancer cell migration and invasion by inhibiting AXL and MET. This study was conducted to investigate the mechanism underlying the anti-cancer effects of cabozantinib through regulation of AXL and MET signaling.The results of Boyden chamber assays showed that cancer cell migration was induced by GAS6 and HGF in SKOV3 cells in serum-free medium. Combinatorial treatment with GAS6 and HGF exerted an additive effect on cell migration. Furthermore, we examined the role of AXL and MET signaling in cell migration. Short interfering RNA targeting AXL and MET inhibited GAS6- and HGF-induced migration, respectively. Double knockdown of AXL and MET completely suppressed cell migration induced by combination treatment with GAS6 and HGF compared to AXL or MET inhibition alone. Finally, we investigated the effects of cabozantinib on cell migration and invasion. Cabozantinib inhibited AXL and MET phosphorylation and downregulated the downstream mediators, phosphorylated SRC in the presence of both GAS6 and HGF in SKOV3 cells. The cell migration and invasion induced by combined GAS6 and HGF treatment were suppressed by cabozantinib, but not by capmatinib, a selective MET inhibitor.Our data indicate that the GAS6-AXL and HGF-MET signal pathways markedly contribute to cancer cell migration and invasion in an independent manner, suggesting that simultaneous inhibition of these two pathways contributes to the anti-cancer effects of cabozantinib. Keywords: Growth arrest-specific 6, Hepatocyte growth factor, AXL receptor tyrosine kinase, MET proto-oncogene-encoded receptor tyrosine kinase, Cabozantinib, Cancer cell migration

Recent studies in RAS wild-type (WT) metastatic colorectal cancer (mCRC) suggest that the survival benefits of therapy using anti-epidermal growth factor receptor (anti-EGFR) and anti-vascular endothelial growth factor (anti-VEGF) antibodies combined with chemotherapy are maximized when the anti-EGFR antibody is given as first-line, followed by subsequent anti-VEGF antibody therapy. We report reverse-translational research using LIM1215 xenografts of RAS WT mCRC to elucidate the biologic mechanisms underlying this clinical observation. Sequential administration of panitumumab then bevacizumab (PB) demonstrated a stronger tendency to inhibit tumor growth than bevacizumab then panitumumab (BP). Cell proliferation was reduced significantly with PB (P