51280

GOLM1

Golgi protein 73 (GP73), a resident Golgi type-II membrane protein, is often upregulated in hepatocytes. In the present study, shRNA-mediated suppression of GP73 expression in hepatocellular carcinoma (HCC) cell lines (MHCC97H, HCCLM3) resulted in a significant inhibition of cell motility and invasion and also led to the regression of epithelial-mesenchymal transition phenotypes. In contrast, overexpression of GP73 in the SMMC7721 cell line retrieved the expression of EMT markers, and promoted cell motility and invasion. High expression of GP73 was also found in HCC tissues with metastasis, as detected by western blot and immunohistochemistry analyses. Kaplan-Meier survival analysis showed that the survival of patients with high GP73 expression was significantly poorer than that of patients with low GP73 expression (p=0.027). Our findings demonstrated an important role of GP73 in HCC metastasis, and indicated that GP73 is a candidate target for HCC therapy.

epithelial-mesenchymal transition (EMT) is associated with invasion and metastasis of cancer cells. Golgi protein 73 (GP73) is a serum biomarker for hepatocellular carcinoma (HCC) and our previous study demonstrated that the expression of GP73 correlated with aggressive behavior and EMT molecules in HCC. However, its role in metastatic mechanism of HCC is not clear. The aim of this study was to investigate the effect of GP73 on invasion and migration, and underlying mechanism of GP73 involved in EMT of HCC. The expression of GP73 was downregulated by small interfering RNA (siRNA). The metastatic and invasive abilities were analyzed using scratch assay and Transwell assay. Changes in EMT-related molecules were evaluated by western blot and qRTPCR analyses, and epithelial-mesenchymal phenotype changes were also observed. expression of GP73 was upregulated in the more metastatic HCC cell lines. Knockdown of GP73 by siRNA resulted in a significant decrease in migratory and invasive abilities in both MHCC97H and Bel-7404 cell lines. Importantly, EMT-related markers and morphological phenotypes significantly changed following by the inhibition of GP73. Silencing GP73 contributed to the reduction of invasion and metastasis via suppressing EMT in HCC. GP73 may serve as a novel molecular target against EMT in HCC metastasis therapy.

The transforming growth factor-beta1 (TGF-beta1) signaling pathways contribute to cell metastasis and epithelial-mesenchymal transition (EMT). Golgi protein 73 (GP73), a type II transmembrane protein in the Golgi apparatus, was initially regarded as a potential biomarker for the diagnosis of hepatocellular carcinoma (HCC). Recently, it was reported that GP73 acts as a key oncogene by promoting HCC growth and metastasis. However, the role of GP73 in metastasis, especially when involving signaling pathways, is uncertain. Here, we report that GP73, which is upregulated in HCC tissues and cell lines, is associated with tumor size, tumor node metastasis stage, distant metastasis and vascular invasion. The ectopic overexpression of GP73 increased HCC cell invasion, EMT and metastasis both in vitro and in vivo. Conversely, GP73 knockdown inhibited invasion and EMT. Moreover, GP73 enhanced p-Smad2 and p-Smad3 levels by mediating TGF-beta1, thus leading to the promotion of EMT and invasion in HCC cells. In contrast, we used SB431542 (SB) to repress p-Smad2 and p-Smad3 expression, which resulted in a reversion of EMT. Furthermore, when the TGF-beta1/Smad pathway was blocked, upregulation of GP73 still caused an enhanced EMT and invasion, and downregulation of GP73 resulted in a decreased in EMT and invasion. In clinical HCC samples, GP73 positively correlated with TGF-beta1/Smad2, which was upregulated in HCC. Taken together, our findings highlight the important role of GP73 in regulating EMT and metastasis in HCC partly by targeting TGF-beta1/Smad2 signaling, suggesting that GP73 may represent a novel potential therapeutic target and prognostic marker for the treatment and diagnosis of HCC.