GOLPH2 expression may serve as diagnostic marker in seminomas

Golgi apparatus targeted therapy in cancer: Are we there yet?

Membrane trafficking within the Golgi apparatus plays a pivotal role in the intracellular transportation of lipids and proteins. Dysregulation of this process can give rise to various pathological manifestations, including cancer. Exploiting Golgi defects, cancer cells capitalise on aberrant membrane trafficking to facilitate signal transduction, proliferation, invasion, immune modulation, angiogenesis, and metastasis. Despite the identification of several molecular signalling pathways associated with Golgi abnormalities, there remains a lack of approved drugs specifically targeting cancer cells through the manipulation of the Golgi apparatus. In the initial section of this comprehensive review, the focus is directed towards delineating the abnormal Golgi genes and proteins implicated in carcinogenesis. Subsequently, a thorough examination is conducted on the impact of these variations on Golgi function, encompassing aspects such as vesicular trafficking, glycosylation, autophagy, oxidative mechanisms, and pH alterations. Lastly, the review provides a current update on promising Golgi apparatus-targeted inhibitors undergoing preclinical and/or clinical trials, offering insights into their potential as therapeutic interventions. Significantly more effort is required to advance these potential inhibitors to benefit patients in clinical settings.

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.

Golgi protein 73, hepatocellular carcinoma and other types of cancers

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with a low survival rate. The identification of mechanisms underlying the development of HCC helps uncover cellular and molecular targets for the diagnosis, prevention, and treatment of HCC. Golgi protein 73 (GP73) level is upregulated in HCC patients and potentially can be a therapeutic target. Despite many studies devoted to GP73 as a marker for HCC early diagnosis, there is little discussion about the function of GP73 in HCC tumorigenesis. Given the poor response to currently available HCC therapies, a better understanding of the role of GP73 in HCC may provide a new therapeutic target for HCC. The current paper summarizes the role of GP73 as a diagnostic marker as well as its roles in liver carcinogenesis. Its roles in other types of cancer are also discussed.

Research progress on GP73 in malignant tumors

Malignant cancer is one of the most serious diseases that currently endanger human health. As most tumors are diagnosed at an advanced stage, the current treatments show poor therapeutic efficacy, and the patients have poor prognosis. However, a 5-year survival rate higher than 80% could be achieved if tumors are diagnosed at an early stage. Therefore, early diagnosis and treatment play important roles in the prevention and treatment of malignant tumors, and serum tumor markers are important for the early diagnosis of malignant cancers. Recent studies have shown that GP73, a transmembrane protein, has greater diagnostic value in primary liver cancer than in other types of cancers, and research on the regulation of GP73 expression has unveiled broad prospects in anticancer targeted therapy. Thus, GP73, as a new tumor marker, deserves further study.

Overexpression of GP73 promotes cell invasion, migration and metastasis by inducing epithelial-mesenchymal transition in pancreatic cancer

Pancreatic cancer is one of the most difficult clinical cases to diagnose with a very low 5-year survival rate of 5%, regardless of the advances made in both the medical and surgical treatment of the disease. One of the contributing factors for the high mortality rate seen of pancreatic cancer patients is the lack of effective chemotherapies, which is believed to be due to drug-resistance. Based on recent evidence, epithelial-mesenchymal transition (ETM) of pancreatic cancer cells has been found to be associated with the development of drug resistance and an increase in cell invasion. Therefore, we conducted the present study in order to investigate the regulatory effects of Golgi protein-73 (GP73) on PC. GP73 and EMT-related gene expressions in PC, along with the adjacent and chronic pancreatitis tissues were determined by means of RT-qPCR and Western blot analysis. Cultured PC cells were treated with pAdTrack-CMV, si-NC, GP73 overexpression, Si-GP73, Snail-siRNA and GP73 + Snail-siRNA. Cell invasion, migration and metastasis were measured in vitro and in vivo. The results revealed that the PC tissues and chronic pancreatitis tissues exhibited diminished E-cadherin expression and amplified GP73, N-cadherin, Vimentin and Snail expression. In response to GP73 gene silencing, PC cells presented with increased E-cadherin expression and decreased N-cadherin, Vimentin, Snail expression in addition to the inhibition of the number of invasive cells, tumor volume and number of liver lesions. These findings highly indicated that the overexpression of GP73 promotes cell invasion, migration and metastasis by inducing EMT in PC.

Quantitative screening of serum protein biomarkers by reverse phase protein arrays

Screening biomarkers in serum samples for different diseases has always been of great interest because it presents an early, reliable, and, most importantly, noninvasive means of diagnosis and prognosis. Reverse phase protein arrays (RPPAs) are a high-throughput platform that can measure single or limited sets of proteins from thousands of patients' samples in parallel. They have been widely used for detection of signaling molecules involved in diseases, especially cancers, and related regulation pathways in cell lysates. However, this approach has been difficult to adapt to serum samples. Previously, we developed a sensitive method called the enhanced protein array to quantitatively measure serum protein levels from large numbers of patient samples. Here, we further refine the technology on several fronts: 1. simplifying the experimental procedure; 2. optimizing multiple parameters to make the assay more robust, including the support matrix, signal reporting method, background control, and antibody validation; and 3. establishing a method for more accurate quantification. Using this technology, we quantitatively measured the expression levels of 10 proteins: alpha-fetoprotein (AFP), beta 2 microglobulin (B2M), Carcinoma Antigen 15-3(CA15-3), Carcinoembryonic antigen (CEA), golgi protein 73 (GP73), Growth differentiation factor 15 (GDF15), Human Epididymis Protein 4 (HE4), Insulin Like Growth Factor Binding Protein 2 (IGFBP2), osteopontin (OPN) and Beta-type platelet-derived growth factor receptor (PDGFRB) from serum samples of 132 hepatocellular carcinoma (HCC) patients and 78 healthy volunteers. We found that 6 protein expression levels are significantly increased in HCC patients. Statistical and bioinformatical analysis has revealed decent accuracy rates of individual proteins, ranging from 0.617 (B2M) to 0.908 (AFP) as diagnostic biomarkers to distinguish HCC from healthy controls. The combination of these 6 proteins as a specific HCC signature yielded a higher accuracy of 0.923 using linear discriminant analysis (LDA), logistic regression (LR), random forest (RF) and support vector machine (SVM) predictive model analyses. Our work reveals promise for using reverse phase protein arrays for biomarker discovery and validation in serum samples.

Markers of clinical utility in the differential diagnosis and prognosis of prostate cancer

Molecular diagnostics is a rapidly evolving area of surgical pathology, that is gradually beginning to transform our diagnostical procedures for a variety of tumors. Next to molecular prognostication that has begun to complement our histological diagnosis in breast cancer, additional testing to detect targets and to predict therapy response has become common practice in breast and lung cancer. Prostate cancer is a bit slower in this respect, as it is still largely diagnosed and classified on morphological grounds. Our diagnostic immunohistochemical armamentarium of basal cell markers and positive markers of malignancy now allows to clarify the majority of lesions, if applied to the appropriate morphological context (and step sections). Prognostic immunohistochemistry remains a problematic and erratic yet tempting research field that provides information on tumor relevance of proteins, but little hard data to integrate into our diagnostic workflow. Main reasons are various issues of standardization that hamper the reproducibility of cut-off values to delineate risk categories. Molecular testing of DNA-methylation or transcript profiling may be much better standardized and this review discusses a couple of commercially available tests: The ConfirmDX test measures DNA-methylation to estimate the likelihood of cancer detection on a repeat biopsy and may help to reduce unnecessary biopsies. The tests Prolaris, OncotypeDX Prostate, and Decipher all are transcript tests that have shown to provide prognostic data independent of clinico-pathological parameters and that may aid in therapy planning. However, further validation and more comparative studies will be needed to clarify the many open questions concerning sampling bias and tumor heterogeneity.

GP73 level determines chemotherapeutic resistance in human hepatocellular carcinoma cells

Objective GP73 is a new hepatocellular carcinoma (HCC) marker, which is highly expressed in hepatocellular carcinoma and closely relates to prognosis. This study was to investigate the effects of GP73 on cellular proliferation, apoptosis, oxaliplatin (OXA) resistance and secretory clusterin (sCLU) of HCC cells. Materials and Methods Western blot and immunofluorescence was used to detect the expression of GP73 in 8 types of commonly used HCC cell lines. Drug resistance was induced by increasing concentration gradient method. The drug-resistant human HCC cell lines underwent GP73 overexpression or inhibition. Flow cytometry were used to detect the proliferation and apoptosis of HCC cell lines. The changes of sCLU were detected by enzyme-linked immunosorbent assay (ELISA). Results The expression of GP73 in MHC-97H cells was the highest and in Hep3B cells the lowest. The expression of GP73 was found further elevated in OXA-resistant MHC-97H cells. After the knockdown of GP73 in OXA-resistant 97H cells, the IC₅₀ of OXA decreased and the ability of cell proliferation decreased significantly. After over-expression of GP73 in OXA-resistant Hep3B cells, the IC₅₀ of OXA increased and the cell proliferation ability increased, showing that GP73 is critical for OXA resistant in HCC cell lines; No significant change of sCLU level in GP73 overexpressed Hep3B and GP73 blocked MHCC-97H were identified. Conclusion The expression level of GP73 is critical for the resistance of OXA in HCC cell lines.

Association of GOLPH2 expression with survival in non-small-cell lung cancer: clinical implications and biological validation

AIM

We investigated the role of GOLPH2 in non-small-cell lung cancer (NSCLC).

METHODS

We analyzed the relationship between the expression of GOLPH2 and the clinical pathological characteristics of patients with NSCLC. The function of GOLPH2 in NSCLC cell lines was also explored through overexpression and knockdown studies.

RESULTS

The positive expression rate of GOLPH2 protein in NSCLC tissue was higher than that of normal lung tissue. We found that positive GOLPH2 expression was closely associated with unfavorable features of patients with NSCLC. The GOLPH2 expression was an independent predictor of the prognosis of patients with NSCLC. That GOLPH2 can promote the proliferation and invasion of NSCLC cells.

CONCLUSION

The GOLPH2 is a novel marker for NSCLC.

Golgi-Related Proteins GOLPH2 (GP73/GOLM1) and GOLPH3 (GOPP1/MIDAS) in Cutaneous Melanoma: Patterns of Expression and Prognostic Significance

GOLPH2 and GOLPH3 are Golgi-related proteins associated with aggressiveness and progression of a number of cancers. Their prognostic significance in melanoma has not yet been analyzed. We performed immunohistochemical analysis for GOLPH2 and GOLPH3 in 20 normal skin, 30 benign nevi and 100 primary melanoma tissue samples and evaluated their expression in three compartments: cancer cells, tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs). High levels of both proteins in melanoma cells were associated with characteristics of aggressive disease, and shorter disease-free survival (DFS) and cancer-specific overall survival (CSOS). On the contrary, increased numbers of GOLPH2-positive and GOLPH3-positive TAMs were observed in thinner, non-ulcerated tumors, with brisk lymphocytic reaction and absent lymphangioinvasion. Distant metastases were not observed among patients with high numbers of GOLPH2-positive TAMs. Increased expression of either protein in TAMs was related to prolonged CSOS and DFS. Similarly, GOLPH3-expressing CAFs were more frequent in thin melanomas with low mitotic rate, without ulceration and lymphangioinvasion. Moreover, increased GOLPH3-positive CAFs correlated with the absence of regional or distant metastases, and with longer CSOS and DFS. GOLPH2 expression was not observed in CAFs. Our results suggest that GOLPH2 and GOLPH3 play a role in melanoma progression and are potential targets for molecular-based therapies.

mTORC1 Up-Regulates GP73 to Promote Proliferation and Migration of Hepatocellular Carcinoma Cells and Growth of Xenograft Tumors in Mice

BACKGROUND & AIMS

Levels of the Golgi protein 73 (GP73) increase during development of hepatocellular carcinoma (HCC); GP73 is a serum marker for HCC. However, little is known about the mechanisms or effects of GP73 during hepatic carcinogenesis.

METHODS

GP73 was overexpressed from a retroviral vector in HepG2 cells, which were analyzed in proliferation and migration assays. Xenograft tumors were grown from these cells in nude mice. The effects of monoclonal antibodies against GP73 were studied in mice and cell lines. GP73(-/-), GP73(+/-), and GP73(+/+) mice were given injections of diethylnitrosamine to induce liver injury. Levels of GP73 were reduced in MHCC97H, HCCLM3, and HepG2.215 cell lines using small hairpin RNAs; xenograft tumors were grown in mice from MHCC97H-small hairpin GP73 or MHCC97H-vector cells. We used microarray analysis to compare expression patterns between GP73-knockdown and control MHCC97H cells. We studied the effects of the mechanistic target of rapamycin (mTOR) inhibitor rapamycin on GP73 expression in different cancer cell lines and on growth of tumors in mice. Levels of GP73 and activated mTOR were quantified in human HCC tissues.

RESULTS

Xenograft tumors grown from HepG2 cells that expressed GP73 formed more rapidly and more metastases than control HepG2 cells in mice. A monoclonal antibody against GP73 reduced proliferation of HepG2 cells and growth of xenograft tumors in mice. GP73(-/-) mice had less liver damage after administration of diethylnitrosamine than GP73(+/-) or GP73(+/+) mice. In phosphatase and tensin homolog-null mouse embryonic fibroblasts with constitutively activated mTOR, GP73 was up-regulated compared with control mouse embryonic fibroblasts; this increase was reversed after incubation with rapamycin. Expression of GP73 also was reduced in HCC and other cancer cell lines incubated with rapamycin. mTORC1 appeared to regulate expression of GP73 in cell lines. Activated mTOR correlated with the level of GP73 in human HCC tissues. Injection of rapamycin slowed the growth of xenograft tumors from MHCC97H-vector cells, compared with MHCC97H-short hairpin GP73 cells.

CONCLUSIONS

Increased expression of GP73 promotes proliferation and migration of HCC cell lines and growth of xenograft tumors in mice. mTORC1 regulates the expression of GP73, so GP73 up-regulation can be blocked with rapamycin. mTOR inhibitors or other reagents that reduce the level or activity of GP73 might be developed for the treatment of HCC.

Serum gp73 is also a biomarker for diagnosing cirrhosis in population with chronic HBV infection

OBJECTIVES

To clarify the role of Golgi membrane glycoprotein 73 (gp73) in evaluating the progression of chronic hepatitis B virus (HBV) infection.

DESIGN AND METHODS

Participants included 958 controls, 421 chronic hepatitis B, 944 hepatic cirrhosis, and 127 hepatocellular carcinoma (HCC) patients. All the patients, with the exception of the controls, were diagnosed HBsAg positive. Serum biomarkers, including gp73, alpha-fetoprotein (AFP), alpha-l-fucosidase, and Lens culinaris agglutinin-reactive fraction of AFP, were determined.

RESULTS

The patients with Hepatic cirrhosis gp73 levels over 150 ng/mL had an odds ratio of 3.21 (95% CI: 2.07-5.00). In hepatic cirrhosis patients, serum gp73 correlated with the Child-Pugh score. gp73 is a marker for diagnosing cirrhosis in the hepatitis populations. When the cut-off was set at 75.5 ng/mL, the sensitivity, specificity, and AUC were 75.6% (95% CI: 71.30%-79.62%), 60.3% (95% CI: 56.95%-63.63%) and 0.72 (95% CI: 0.69-0.75), respectively.

CONCLUSION

The variation trend of gp73 in chronic liver disease may indicate that monitoring of serum gp73 is helpful to diagnose cirrhosis in population with chronic HBV infection.

Expression of GOLPH2 is associated with the progression of and poor prognosis in gastric cancer

Golgi phosphoprotein 2 (GOLPH2) has been associated with the development and progression of various human cancers. The aims of this study were to investigate the relationship between GOLPH2 and gastric cancer (GC) progression and explore the clinical significance of GOLPH2 in GC. GOLPH2 expression was examined in four pairs of primary GC tissues and the adjacent non-cancerous tissues from the same patients, using immunohistochemistry (IHC), quantitative PCR and western blotting. Furthermore, GOLPH2 protein expression was analyzed in 10 normal gastric tissues and 385 clinicopathologically characterized cases of GC by IHC. Statistical analyses were performed to determine the prognostic and diagnostic associations. GOLPH2 mRNA and protein expression were both markedly upregulated in GC tissues, compared with the paired adjacent non-cancerous tissues. The Chi-square test and Spearman analysis revealed a significant correlation between GOLPH2 expression and clinical stage, T classification, lymph node metastasis, metastasis and venous invasion. Patients with a higher GOLPH2 expression had a shorter overall survival (OS), compared to patients with lower GOLPH2 expression. Notably, our results suggested that GOLPH2 is associated with the development and progression of GC. Therefore, additional studies focusing on the potential of GOLPH2 as a novel therapeutic target in GC are required.

Aberrant chimeric RNA GOLM1-MAK10 encoding a secreted fusion protein as a molecular signature for human esophageal squamous cell carcinoma

It is increasingly recognized that chimeric RNAs may exert a novel layer of cellular complexity that contributes to oncogenesis and cancer progression, and could be utilized as molecular biomarkers and therapeutic targets. To date yet no fusion chimeric RNAs have been identified in esophageal cancer, the 6th most frequent cause of cancer death in the world. While analyzing the expression of 32 recurrent cancer chimeric RNAs in esophageal squamous cell carcinoma (ESCC) from patients and cancer cell lines, we identified GOLM1-MAK10, as a highly cancer-enriched chimeric RNA in ESCC. In situ hybridization revealed that the expression of the chimera is largely restricted to cancer cells in patient tumors, and nearly undetectable in non-neoplastic esophageal tissue from normal subjects. The aberrant chimera closely correlated with histologic differentiation and lymph node metastasis. Furthermore, we demonstrate that chimera GOLM1-MAK10 encodes a secreted fusion protein. Mechanistic studies reveal that GOLM1-MAK10 is likely derived from transcription read-through/splicing rather than being generated from a fusion gene. Collectively, these findings provide novel insights into the molecular mechanism involved in ESCC and provide a novel potential target for future therapies. The secreted fusion protein translated from GOLM1-MAK10 could also serve as a unique protein signature detectable by standard non-invasive assays. These observations are critical as there is no clinically useful molecular signature available for detecting this deadly disease or monitoring the treatment response.

GP73 is a potential marker for evaluating AIDS progression and antiretroviral therapy efficacy

Golgi protein-73 (GP73) is upregulated in cancers and viral infections; however, its role in human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) remains undetermined. GP73 was evaluated as a biomarker of HIV progression and AIDS treatment efficacy. Forty-eight HIV patients (≤ 350 CD4 + T cells/μL) undergoing highly active antiretroviral therapy (HAART group) and 18 HIV patients expected to undergo HAART within 9 months (>350 CD4 + T cells/μL) (control group) were enrolled in a prospective, single center, cohort study from May 2009 to Jun 2012. Blood aspartate aminotransferase, alanine aminotransferase (ALT), cholesterol, triglycerides, and total bilirubin were assessed at baseline, 2 weeks, and 1, 3, 6, 9, and 12 months (HAART group) or 3 month intervals (control group). Serum HIV RNA level (viral load) was determined by reverse-transcriptase polymerase chain reaction (RT-PCR), and serum and peripheral blood mononuclear cell (PBMC) GP73 concentration were determined by chemiluminescent immunoassay kit and western blot, respectively. Significant positive and negative correlations in baseline serum GP73 concentration and HIV viral load (r = 0.39, P < 0.001) and CD4 + T cell count (r = -0.501, P < 0.001) were observed, respectively. In receiver operator characteristic (ROC) analysis, area under the curve (AUC) was 0.79 (95 % CI 0.66-0.92). The sensitivity and specificity of GP73 for correct identification of patients with ≤350 CD4 + T cells/μL were 76.09 and 75.0 %, respectively, with an ROC-derived cut-off of 100.6 ng/mL. For HIV patients undergoing antiretroviral therapy, GP73 may be a potential biomarker treatment efficacy useful in AIDS management.

GP73 is down-regulated in gastric cancer and associated with tumor differentiation

Background

Golgi protein 73 (GP73) is a type II Golgi transmembrane protein. It is over-expressed in several cancers, including hepatocellular carcinomas, bile duct carcinomas, lung cancer and prostate cancer. However, there are few reports of GP73 in gastric cancer. This study is aimed at investigating the expression of GP73 and its relationship with clinical pathological characters in gastric cancer.

Methods

GP73 mRNA level was determined by quantitative real-time RT-PCR in 41 pairs of matched gastric tumorous tissues and adjacent non-tumorous mucosal tissues. Western blotting was also performed to detect the GP73 protein level. GP73 protein expression was analyzed by immunohistochemistry in 52 clinically characterized gastric cancer patients and 10 non-tumorous gastric mucosal tissue controls.

Results

The mRNA and protein level of GP73 were significantly down-regulated in gastric tumorous tissues compared with the non-tumorous mucosal tissues. In non-tumorous mucosa, strong diffuse cytoplasmic staining can be seen in cells located at the surface of the glandular and foveolar compartment; while in tumorous tissues, the staining was much weaker or even absent, and mainly in a semi-granular dot-like staining pattern. The expression level of GP73 protein was associated with patients’ gender and tumor differentiation.

Conclusions

GP73 was normally expressed in non-tumorous gastric mucosa and down-regulated in gastric cancer. Its expression in gastric cancer was correlated with tumor differentiation.

Monoclonal antibody preparation of Golgi phosphoprotein 2 and preliminary application in the early diagnosis of hepatocellular carcinoma

Golgi phosphoprotein 2 (Golph2) is a type II Golgi‑specific membrane protein, which has been found to be overexpressed in hepatocellular carcinoma (HCC) patients. The sensitivity of diagnosis of HCC using Golph2 (76%) was markedly elevated compared with alpha‑fetoprotein (AFP) (70%), and Golph2 is expected to be a novel and effective serum biomarker for the diagnosis of HCC. The aim of this study was to prepare monoclonal antibodies against Golph2 and to establish double-antibody sandwich enzyme-linked immunosorbent assay (s-ELISA), which will be used in diagnostics, therapeutics and as a tool in understanding the role of Golph2 in the pathogenesis of liver diseases and cancer. In this study, fusion protein TRX-Golph2 was expressed and purified using an Escherichia coli system. BALB/c mice were immunized with TRX-Golph2 recombinant protein. The hybridoma technique was used for the production of anti-Golph2 monoclonal antibody. Hybridoma clones were screened using indirect ELISA and anti-Golph2 monoclonal antibody was produced in the ascites of BALB/c mice. The specificity of anti-Golph2 monoclonal antibody was detected by western blot analysis and immunocytochemistry. s-ELISA was established using horseradish peroxidase (HRP)‑labeled anti-Golph2 monoclonal antibody and used to detect the antigen in the serum of HCC patients. As a result, five stable hybridoma cell clones (5C6D5, 5B7F5, 7F5F3, 8A7B4, 8C9E8) producing anti-Golph2 monoclonal antibody were established. The highest titer of anti-Golph2 monoclonal antibody (5C6D5) was 1:51,200. Western blot analysis revealed that anti-Golph2 monoclonal antibody had a high specificity for Golph2 protein. Anti-Golph2 monoclonal antibody was HRP-labeled and the optimal working concentration was found to be 1:500. The levels of antigen in a proportion of HCC patients were shown to be significantly higher compared to those found in healthy controls.

Tumor markers for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with a high rate of morbidity and mortality. HCC affects approximately one million individuals annually worldwide, with the incidence equal to the mortality rate. In 2008, HCC was listed as the third most lethal cancer. Thus, early diagnosis is crucial for improving the survival rate for patients. α-fetoprotein (AFP) together with iconography and pathology detection are commonly used in the clinical early diagnosis of liver cancer. However, the specificity and sensitivity of AFP used in screening for liver cancer are not satisfactory. Athough the development of molecular biology has led to the identification of new tumor markers, including proteantigens, cytokines, enzymes and isoenzymes, as well as related genes that can be used in the treatment and prognosis of liver cancer, more tumor markers are required for effective early diagnosis of diseases and monitoring of the curative effect.

Interleukin-6 and oncostatin M are elevated in liver disease in conjunction with candidate hepatocellular carcinoma biomarker GP73

The Golgi phosphoprotein GP73 is elevated in the circulation of individuals with a diagnosis of hepatocellular carcinoma. Its usefulness as a biomarker of HCC is questioned, since it has also been reported to be elevated in the circulation of people with liver cirrhosis. Regulation of GP73 by inflammatory cytokines is therefore of interest. The interleukin-6 (IL-6) family cytokines were tested for effects on GP73 mRNA and/or protein levels in human hepatoblastoma HepG2 cells. Levels of GP73 mRNA and protein were up-regulated in HepG2 cells following treatment with either proinflammatory cytokine IL-6 or the related cytokine oncostatin M (OSM). Induction required the shared receptor subunit gp130, and correlated with increased tyrosine phosphorylation of STAT3. Maximal cytokine-mediated induction was not observed in the presence of protein synthesis inhibitor cycloheximide, suggesting additional regulatory factors play an important role. ELISA measurement of GP73 and IL-6 levels in the sera of patients with pre-malignant liver disease revealed a significant correlation between circulating levels of the two proteins. Similarly, a sensitive ELISA assay was developed to measure circulating OSM. OSM levels were elevated 6-7 fold in sera from patients with either cirrhosis or HCC relative to controls without liver disease. Although there was an association between levels of GP73 and OSM in serum from people with liver cirrhosis, there was not a statistically significant correlation in HCC, suggesting that the role of the cytokines in determining circulating levels may be complex. To our knowledge, this is the first report of OSM elevation being associated with liver disease.

Golgi phosphoprotein 2 in physiology and in diseases

Golgi phosphoprotein 2 (GOLPH2, also termed GP73 and GOLM1) is a type II transmembrane protein residing in the cis and medial-Golgi cisternae. GOLPH2 is predominantly expressed in the epithelial cells of many human tissues. Under poorly defined circumstances, GOLPH2 can be cleaved and released to the extracellular space. Despite of its relatively “young age” since the first description in 2000, the physiological and pathological roles of GOLPH2 have been the subject that has attracted considerable amount of attention in recent years. Here, we review the history of GOLPH2’s discovery and the multitude of studies by many groups around the world aimed at understanding its molecular, cellular, physiological, and pathogenic activities in various settings.

Cloning and characterization of human Golgi phosphoprotein 2 gene (GOLPH2/GP73/GOLM1) promoter

Human Golgi phosphoprotein 2 gene (also known as GOLPH2, GP73 or GOLM1) encodes an epithelial-specific Golgi membrane protein which can be induced by virus infection. It is also overexpressed in a number of tumors and is currently considered as an early diagnosis marker for hepatocellular carcinoma. However, little is known about how GOLPH2 is dysregulated in these disease conditions and the functional implications of its overexpression. The aim of this study is to investigate human GOLPH2 regulation mechanisms. We cloned a 2599 bp promoter fragment of GOLPH2 and found it maintained epithelial specificity. By deletion analysis, a repressive region (-864 to -734 bp), a positive regulatory region (-734 to -421 bp) and a core promoter region (-421 to -79 bp) were identified. Sequence analysis revealed that GOLPH2 core promoter was devoid of canonical TATA element and classified as a TATA-less promoter. Adenoviral early region 1A (E1A) was able to activate GOLPH2 and the CtBP interaction domain of E1A was sufficient but not required for activation. A GC-box motif (-89 to -83 bp) in GOLPH2 core promoter region partly mediated E1A transactivation. These results delineated regulatory regions and functional element in GOLPH2 promoter, elucidated adenoviral E1A stimulation mechanisms and provided insight into GOLPH2 functions.

Advances in understanding the relationship between GP73 and hepatic diseases

Golgi protein-73 (GP73), a recently discovered Golgi glycoprotein localized on the membrane of the Golgi complex, is expressed in many types of human epithelial cells. In normal human liver, GP73 is highly expressed in biliary epithelial cells, but barely detectable in hepatocytes. However, GP73 expression has been found to be strongly up-regulated in hepatocytes and elevated in the serum in patients with liver diseases, especially those with hepatocellular carcinoma (HCC). Thus, GP73 is a candidate serum marker for the early detection of HCC.