178: Leucine-rich α2 glycoprotein promotes TGFβ1-induced apoptosis in the lewis lung carcinoma cell lines

Abstract

Aims Leucine-rich α2 glycoprotein (LRG) is an approximately 50 kDa glycoprotein originally found in the blood. It has been reported that the expression levels of LRG were elevated in the sera of several cancers. While it has been demonstrated that LRG modulated TGFβ1 signaling in endothelial cells and promoted pathogenic angiogenesis, the precise function of LRG in cancer remains unclear. In this study, we investigated the role of LRG on the cellular response by TGFβ1 in Lewis lung carcinoma (LLC) cell line. Methods Parental LLC, mLRG-overexpressing LLC or control vector transfeced LLC cells were subcutaneously transplanted into LRG Knockout(KO) or Wild-type(WT) C57BL/6 J mice and tumor growth was monitored. Cell proliferation treated with TGFβ1 was evaluated by WST-8 assay. Caspase activity was measured with Casapase-Glo™ assay kit, protein expression levels were analyzed by western blotting and gene expression was analyzed with Quantitative real-time PCR. LLC tumor growth were monitored in LRG KO or WT mice treated with TGFβRI inhibitor(SB431542) or vehicle. Apoptosis of LLC tumor was evaluated by TUNEL staining. Result LLC tumor growth in LRG KO mice was significantly enhanced compared with that in WT mice. Conversely, overexpression of mLRG significantly inhibited the growth of LLC tumors in WT mice. TGFβ1 inhibited the proliferation of LLC cells in vitro. Addition of TGFβ1 strongly inhibited the proliferation of mLRG-overexpressing LLC cells than control vector LLC cells by induction of apoptosis. By TGFβ1 stimulation, induction of apoptosis via activation of smad2 and downstream signaling pathway was significantly increased in mLRG overexpressing LLC compared with control LLC cells in vitro. TGFβRI inhibitor significantly enhanced growth and inhibited apoptosis of LLC tumor in WT mice compared with LRG KO. Conclusion Our data showed that LRG promotes TGFβ1-induced apoptosis in LLC, in vitro and in vivo. LRG might be classified as a novel protein that modulates the effects of cytokines.