Combining GP73 with liver stiffness measurements: A proof-of-concept for non-invasive fibrosis assessment in antiviral-naïve HBV patients

Possible roles of Golgi protein-73 in liver diseases

Golgi protein 73 (also known as GP73 or GOLPH2) is a transmembrane glycoprotein present in the Golgi apparatus. In diseased states, GP73 is expressed by hepatocytes rather than by bile duct epithelial cells. Many studies have reported that serum GP73 (sGP73) is a marker for hepatocellular carcinoma (HCC). For HCC diagnosis, the sensitivities of sGP73 were higher than that of other markers but the specificities were lower. Considering that the concentration of GP73 is consistent with the stage of liver fibrosis and cirrhosis, some studies have implied that GP73 may be a marker for liver fibrosis and cirrhosis. Increased sGP73 levels may result from hepatic inflammatory activity. During liver inflammation, GP73 facilitates liver tissue regeneration. By summarizing the studies on GP73 in liver diseases, we wish to focus on the mechanism of GP73 in diseases.

Golgi Phosphoprotein 73: The Driver of Epithelial-Mesenchymal Transition in Cancer

Golgi phosphoprotein 73 (GP73, also termed as GOLM1 or GOLPH2) is a glycosylated protein residing on cis-Golgi cisternae and highly expressed in various types of cancer tissues. Since GP73 is a secretory protein and detectable in serum derived from cancer patients, it has been regarded as a novel serum biomarker for the diagnosis of different cancers, especially hepatocellular carcinoma (HCC). However, the functional roles of GP73 in cancer development are still poorly understood. In recent years, it has been discovered that GP73 acts as a multifunctional protein-facilitating cancer progression, and strikingly, it has been identified as a leading factor promoting epithelial-mesenchymal transition (EMT) of cancer cells and causing cancer metastasis. In this review, we have overviewed the latest findings of the functional roles of GP73 in elevating cancer progression, especially in facilitating EMT and cancer metastasis through modulating expression, transactivation, and trafficking of EMT-related proteins. In addition, unsolved research fields of GP73 have been lightened, which might be helpful to elucidate the regulatory mechanisms of GP73 on EMT and provide potential approaches in therapeutics against cancer metastasis.

Combined Serum Golgi Membrane Glycoprotein 73 Improves the Accuracy of Transient Elastography for Significant Fibrosis Detection in Patients with Chronic HBV Infections

Background: Golgi membrane glycoprotein 73 (GP73) serum level is a potential biomarker for diagnosing significant fibrosis and cirrhosis in chronic liver diseases. Objectives: The current study aimed to evaluate the accuracy of GP73 serum levels as a biomarker in the diagnosis of significant liver fibrosis in patients with hepatitis B virus (HBV). A new promising algorithm was developed by combining LSM and GP73 to predict significant liver fibrosis. Methods: Information on the following parameters were obtained from 165 patients with HBV: liver stiffness measurement (LSM), serum GP73 level, and some other fibrosis criteria approved for clinical practice. The area under the curve (AUC) and sensitivity and specificity of GP73 were compared with LSM, aminotransferase-to-platelet ratio index (APRI), and 4-factor based fibrosis index (FIB-4) for diagnosing significant fibrosis. Results: Compared to the non-significant liver fibrosis patients, the HBV infected patients with significant fibrosis showed a higher level of serum GP73 [64.05 (24.41 - 144.39) versus 91.30 (31.81 - 200.05) ng/mL, P < 0.001]. Concerning significant fibrosis diagnosis, GP73 exhibited advantages regarding the AUC (0.702), sensitivity (69.3%), and specificity (66.0%). Besides, GP73 did not show any advantage over LSM and APRI, but it had a better performance than FIB-4 in significant fibrosis detection. For the newly developed algorithm combining GP73 with LSM, the AUC, sensitivity, and specificity were 0.848, 77.4%, and 83.5%, respectively; hence, it's superior to LSM (0.832, 72.6%, and 83.5%, respectively; P = 0.016) for diagnosing significant fibrosis. Conclusions: This study demonstrated that GP73 can be considered as a new effective biomarker for diagnosing liver fibrosis. The accuracy of significant fibrosis detection in patients with HBV infection can be improved by the new algorithm that contains GP73 and LSM.

Golgi protein 73 and its diagnostic value in liver diseases

Golgi protein 73 (GP73, also referred to as Golph 2) with 400 amino acids is a 73 kDa transmembrane glycoprotein typically found in the cis-Golg complex. It is primarily expressed in epithelial cells, which has been found upregulated in hepatocytes in patients suffering from both viral and non-viral liver diseases. GP73 has drawn increasing attention for its potential application in the diagnosis of liver diseases such as hepatitis, liver cirrhosis and liver cancer. Herein, we reviewed the discovery history of GP73 and summarized studies by many groups around the world, aiming at understanding its structure, expression, function, detection methods and the relationship between GP73 and liver diseases in various settings.

Knockdown of Golgi phosphoprotein 73 blocks the trafficking of matrix metalloproteinase-2 in hepatocellular carcinoma cells and inhibits cell invasion

Golgi phosphoprotein 73 (GP73) has been regarded as a novel serum biomarker for the diagnosis of hepatocellular carcinoma (HCC) in recent years. It has been reported that the upregulation of GP73 may promote the carcinogenesis and metastasis of HCC; however, the mechanisms remain poorly understood. In this study, GP73 correlates positively with matrix metalloproteinase‐2 (MMP‐2) in HCC‐related cells and tissues. Further studies indicate that the knockdown of GP73 blocks MMP‐2 trafficking and secretion, resulting in cell invasion inhibition. Additionally, the knockdown of GP73 induces the accumulation of intracellular MMP‐2, which inhibits the phosphorylation of Src at Y416 and triggers the inhibition of SAPK/JNK and p53‐p21 signalling pathways through a negative feedback loop. Finally, the transactivation of MMP2 was inhibited by the reduction in E2F1. This study reveals that GP73 plays functional roles in the trafficking and equilibrium of epithelial‐mesenchymal transition (EMT)‐related secretory proteins and that GP73 serves as a new potential target for combating the metastasis of HCC.