Increase in hepatocyte growth factor receptor tyrosine kinase activity in renal carcinoma cells is associated with increased motility partly through phosphoinositide 3-kinase activation

Dysregulated cell motility is one of the major characteristics of invasion and metastatic potentials of malignant tumor cells. Here, we examined the h epatocyte growth factor (HGF)-induced cell motility of two human renal carc inoma cell lines, ACHN and VMRC-RCW. Scattering and migration was induced i n ACHN in an HGF-dependent manner, whereas they were maintained in VMRC-RCW even in the absence of HGF. In VMRC-RCW, HGF receptor (HGFR) tyrosine kina se was constitutively active, and sequence analysis showed N375S, A1209G an d V1290L mutations. However, transfection experiments using porcine aortic endothelial (PAE) cells demonstrated that no single mutation or combination of two or three mutations caused HGF-independent constitutive activation. Conversely, the expressed amount of receptor protein had a pivotal role in the basal kinase activity. With respect to downstream signaling molecules o f HGFR in ACHN or VMRC-RCW, the Ras-MAPK pathway was downregulated, whereas phosphoinositide 3-kinase (PI3-kinase) was not further activated by HGF-tr eatment in VMRC-RCW cells. The PI3-kinase inhibitors, wortmannin and LY2940 02 strongly inhibited spontaneous migration of VMRC-RCW. One transfected PA E cell line with massive overexpression of HGFR demonstrated scattered morp hology and increased PI3-kinase activity in association with increased moti lity, which was partially inhibited by LY294002. Taken together, our result s indicate that the overexpression of HGFR causes increase in cellular moti lity and PI3-kinase shows the important contribution on the increased motil ity of renal carcinoma cells.