The Research On The Mechanism Of Ganglioside GD1a Regulation Of Inducible No Synthase (NOS2) And Hepatocyte Growth Factor (HGF) In Murine Steosarcoma FBJ Cells

Gangliosides, sialic acid-containing glycosphingolipids, are localized on the plasma membranes of higher vertebrates and have been implicated in multifarious bioactivity in cells. They are involved in cell and cell interactions on the cell surface and affect signal transductions, leading the modulation of cell proliferation, tumor metastatic ability. In murine osteosarcoma FBJ-S1 cells with poorly metastatic property and the highly metastatic variant FBJ-LL cells are obtained from FBJ virus-induced osteosarcoma of Balb/c mouse. Previous results showed that GD1a suppressed metastatic ability of FBJ cells.Inducible nitric oxide synthase (NOS2) is associated with inflammation and tumorigenesis and over-expressed in a number of tumors and implicated in tumor growth and metastasis. In murine FBJ osteosarcoma cells, silencing NOS2 inhibited cell proliferation, migration, and anchorage-independent growth, suggesting that the metastatic properties of FBJ-LL cells are tightly associated with NOS2. GD1a negatively regulates NOS2 through ERK1 but not ERK2, and further investigation found that ERK/MAPK pathway played an important role in the regulation of NOS2 by GD1a. GD1a suppressed NOS2 expression through GRB2/ARAF/MEK2/ERK1, and EGFR was not involved. Similar with GD1a, EGF also shared the same signal pathway with GD1a to suppress NOS2 expression. Although NOS2 was higher expressed in FBJ-LL cell compared with FBJ-S1 cell, but there was a signal pathway which inhibited NOS2 expresson in FBJ-LL cells:EGFR/GRB2/SOS/MRAS/ARAF/MEK2/ERK1. Furthermore, in FBJ-LL cells, PKC, Src, cAMP-dependent pathway and PAK1 were confirmed to be involved in NOS2 regulation by inhibitor or activator treatment and RNAi technique.Hepatocyte growth factor (HGF) is a mesenchyme-derived growth factor. In FBJ cells, GDla suppressed HGF expression, and HGF formed an autocrine loop with its only known receptor MET. Caveolin-1 is the main component of caveolae, which locates on the cell membrane and takes part in signal transduction. In FBJ cells, GDla suppressed HGF through increasing Cavl expression which suppressed the phorsphorylation of MET. But Cavl didn’t influenced by HGF expression. ERK/MAPK and PI3K/AKT pathway also found to be took part in the regulation of HGF in FBJ-LL cells.