Ganglioside GD1a negatively regulates hepatocyte growth factor expression through caveolin-1 at the transcriptional level in murine osteosarcoma cells

BackgroundHepatocyte growth factor (HGF) is a mesenchyme-derived, multifunctional protein that is implicated in tumor growth and invasive behavior. Some tumor cells express both HGF and its receptor MET, forming an autocrine loop that permanently activates it. Ganglioside GD1a suppresses metastatic capacity in murine FBJ osteosarcoma cells and MET phosphorylation activated by HGF binding, but the signaling pathway controlling HGF production has not been fully explored.MethodsExpression of HGF, caveolins, or MET of the cells that had been transfected with siRNA or cDNA directed to GM2/GD2 synthase, caveolin-1 or HGF was determined by semi-quantitative RT-PCR and Western blots.ResultsHGF expression in highly metastatic, GD1a-deficient FBJ-LL cells was higher than that in the poorly metastatic, GD1a-rich FBJ-S1 cells. Transfection with GM2/GD2 synthase cDNA increased GD1a levels in FBJ-LL cells and suppressed HGF expression. Treatment with siRNAs directed toward GM2/GD2 synthase in FBJ-S1 cells reduced gangliosides and augmented HGF expression. GD1a was found to be the only ganglioside species suppressing HGF expression upon addition to FBJ-LL cells. HGF expression was decreased by GD1a addition to FBJ-LL cells after 48 h, enough to induce caveolin-1 expression. Silencing caveolin-1 up-regulated HGF, and the re-introduction of caveolin-1 cDNA decreased HGF expression. Caveolin-1 suppressed MET phosphorylation. We also found GD1a regulation of HGF in Lewis lung carcinoma cells.ConclusionsHGF expression was negatively regulated by GD1a through caveolin-1 at the transcriptional level via the suppression of MET phosphorylation.General significanceThis is the first report that ganglioside GD1a negatively regulates HGF expression through caveolin-1.

► Ganglioside GD1a was shown to suppress HGF expression at the transcriptional level. ► GD1a increases caveolin-1 expression that also negatively regulates HGF expression. ► Caveolin-1 suppressed MET phosphorylation. ► GD1a regulation of HGF was also found in Lewis lung carcinoma cells.