AEG -1 overexpression: a novel indicator for peritoneal dissemination and lymph node metastasis in epithelial ovarian cancers

Emerging Role and Clinicopathological Significance of AEG-1 in Different Cancer Types: A Concise Review

Tumor breakthrough is driven by genetic or epigenetic variations which assist in initiation, migration, invasion and metastasis of tumors. Astrocyte elevated gene-1 (AEG-1) protein has risen recently as the crucial factor in malignancies and plays a potential role in diverse complex oncogenic signaling cascades. AEG-1 has multiple roles in tumor growth and development and is found to be involved in various signaling pathways of: (i) Ha-ras and PI3K/AKT; (ii) the NF-κB; (iii) the ERK or mitogen-activated protein kinase and Wnt or β-catenin and (iv) the Aurora-A kinase. Recent studies have confirmed that in all the hallmarks of cancers, AEG-1 plays a key functionality including progression, transformation, sustained angiogenesis, evading apoptosis, and invasion and metastasis. Clinical studies have supported that AEG-1 is actively intricated in tumor growth and progression which includes esophageal squamous cell, gastric, colorectal, hepatocellular, gallbladder, breast, prostate and non-small cell lung cancers, as well as renal cell carcinomas, melanoma, glioma, neuroblastoma and osteosarcoma. Existing studies have reported that AEG-1 expression has been induced by Ha-ras through intrication of PI3K/AKT signaling. Conversely, AEG-1 also activates PI3K/AKT pathway and modulates the defined subset of downstream target proteins via crosstalk between the PI3K/AKT/mTOR and Hedgehog signaling cascade which further plays a crucial role in metastasis. Thus, AEG-1 may be employed as a biomarker to discern the patients of those who are likely to get aid from AEG-1-targeted medication. AEG-1 may play as an effective target to repress tumor development, occlude metastasis, and magnify the effectiveness of treatments. In this review, we focus on the molecular mechanism of AEG-1 in the process of carcinogenesis and its involvement in regulation of crosstalk between the PI3K/AKT/mTOR and Hedgehog signaling. We also highlight the multifaceted functions, expression, clinicopathological significance and molecular inhibitors of AEG-1 in various cancer types.

The Scope of Astrocyte Elevated Gene-1/Metadherin (AEG-1/MTDH) in Cancer Clinicopathology: A Review

Since its initial cloning in 2002, a plethora of studies in a vast number of cancer indications, has strongly established AEG-1 as a bona fide oncogene. In all types of cancer cells, overexpression and knockdown studies have demonstrated that AEG-1 performs a seminal role in regulating proliferation, invasion, angiogenesis, metastasis and chemoresistance, the defining cancer hallmarks, by a variety of mechanisms, including protein-protein interactions activating diverse oncogenic pathways, RNA-binding promoting translation and regulation of inflammation, lipid metabolism and tumor microenvironment. These findings have been strongly buttressed by demonstration of increased tumorigenesis in tissue-specific AEG-1 transgenic mouse models, and profound resistance of multiple types of cancer development and progression in total and conditional AEG-1 knockout mouse models. Additionally, clinicopathologic correlations of AEG-1 expression in a diverse array of cancers establishing AEG-1 as an independent biomarker for highly aggressive, chemoresistance metastatic disease with poor prognosis have provided a solid foundation to the mechanistic and mouse model studies. In this review a comprehensive analysis of the current and up-to-date literature is provided to delineate the clinical significance of AEG-1 in cancer highlighting the commonality of the findings and the discrepancies and discussing the implications of these observations.

The Effect of Metadherin on NF-κB Activation and Downstream Genes in Ovarian Cancer

Ovarian cancer (OC) is the most aggressive gynecological cancer. Even with the advances in detection and therapeutics, it still remains clinically challenging and there is a pressing need to identify novel therapeutic strategies. In searching for rational molecular targets, we identified metadherin (MTDH), a multifunctional gene associated with several tumor types but previously unrecognized in OC. In this study, we found the MTDH is overexpressed in OC tissues. Through in vitro assays with overexpression cells, we characterized the role of MTDH. We confirmed MTDH stable overexpression significantly increased the expression of TNF-α, IL-6, IL-8, IL-10, and IL-1β. Interestingly, NF-kappa-B (NF-κB) and MTDH were found in a feed-forward loop motif. Thus, our findings support the notion that the MTDH and NF-κB signaling network contributes to OC traits. MTDH represents a new OC-associated gene that can contribute to insights of OC biology and suggests other treatment strategies.

Significance of BRCA1 expression in breast and ovarian cancer patients with brain metastasis - A multicentre study

PURPOSE

Cerebral metastases develop in 10-30% of patients with breast cancer (BC) and in around 3.3 to 4% of patients with ovarian cancer (OC). The aim of the multicenter study is to investigate the correlation between the expression of estrogen alpha receptors (ERα), progesterone receptors (PR), human epidermal growth factor receptor 2 (HER2), stromal cell-derived factor 1 (SDF1) and its receptor C-X-C chemokine receptor type 4 (CXCR4), breast cancer metastasis suppressor 1 (BRMS1), astrocyte elevated gene 1 (AEG1), depending on the status of BRCA1 protein, in patients suffering from OC and BC with brain metastases.

PATIENTS AND METHODS

The analysis included 51 patients: 29 with BC and 22 with OC, in whom brain metastases were disclosed.

RESULTS

In most patients (65.5% of BC patients and 68.2% of patients with OC tumors) BRCA1 protein loss was found. No correlation was disclosed between the levels of ERα, PR receptors, HER2, SDF1, CXCR4, AEG1, BRMS1 and BRCA1 status, patient age, stage of disease advancement, grade of histological maturity of the cells, presence of metastases to lymph nodes. A statistically significant correlation was disclosed between the negative expression of PR receptors and a high expression of CXCR4 in patients with BC. High values of the AEG1 protein (linked to metastases) were detected alongside a high expression of BRMS1 (a suppressor of metastases).

CONCLUSIONS

Patients with BC and OC and brain metastases have a frequent loss of BRCA1 expression. The role of ERα, PR, HER2, SDF1, CXCR4, AEG1, BRMS1 in metastatic process needs further studies.

Metadherin Is a Prognostic Apoptosis Modulator in Mesothelioma Induced via NF-κB-Mediated Signaling

Therapies against malignant pleural mesothelioma (MPM) have yielded disappointing results, in part, because pathologic mechanisms remain obscure. In searching for rational molecular targets, we identified metadherin (MTDH), a multifunctional gene associated with several tumor types but previously unrecognized in MPM. Cox proportional hazards regression analysis delineated associations between higher MTDH expression and lower patient survival from three independent MPM cohorts (n = 349 patients). Through in vitro assays with overexpression and downregulation constructs in MPM cells, we characterized the role of MTDH. We confirmed in vivo the phenotype of altered MTDH expression in a murine xenograft model. Transcriptional regulators of MTDH were identified by chromatin immunoprecipitation. Overexpression of both MTDH mRNA (12-fold increased) and protein levels was observed in tumor tissues. MTDH stable overexpression significantly augmented proliferation, invasiveness, colony formation, chemoresistance, and an antiapoptosis phenotype, while its suppression showed opposite effects in MPM cells. Interestingly, NF-κB and c-Myc (in a feed-forward loop motif) contributed to modulating MTDH expression. Knockdown of MTDH expression profoundly retarded xenograft tumor growth. Thus, our findings support the notion that MTDH integrates upstream signals from certain transcription factors and mediates pathogenic interactions contributing to MPM traits. MTDH represents a new MPM-associated gene that can contribute to insights of MPM biology and, as such, suggest other treatment strategies.

ADH1B promotes mesothelial clearance and ovarian cancer infiltration

Primary debulking surgery followed by adjuvant chemotherapy is the standard treatment for ovarian cancer. Residual disease after primary surgery is associated with poor patient outcome. Previously, we discovered ADH1B to be a molecular biomarker of residual disease. In the current study, we investigated the functional role of ADH1B in promoting ovarian cancer cell invasiveness and contributing to residual disease. We discovered that ADH1B overexpression leads to a more infiltrative cancer cell phenotype, promotes metastasis, increases the adhesion of cancer cells to mesothelial cells, and increases extracellular matrix degradation. Live cell imaging revealed that ADH1B-overexpressing cancer cells efficiently cleared the mesothelial cell layer compared to control cells. Moreover, gene array analysis revealed that ADH1B affects several pathways related to the migration and invasion of cancer cells. We also discovered that hypoxia increases ADH1B expression in ovarian cancer cells. Collectively, these findings indicate that ADH1B plays an important role in the pathways that promote ovarian cancer cell infiltration and may increase the likelihood of residual disease following surgery.

AEG-1 mRNA expression in non-small cell lung cancer is associated with increased tumor angiogenesis

Astrocyte-elevated gene-1 (AEG-1) is implicated in the oncogenesis and angiogenesis of various types of human malignant disease. However, the angiogenesis roles of AEG-1 in non-small cell lung cancer (NSCLC) remain to be further elucidated. In the present study, the expression level of AEG-1 mRNA in seven human lung cell lines and 89 paired tissue samples (tumor tissues (TTs) and pair-matched normal adjacent tissues (PMNATs)) from NSCLC patients was detected by real-time PCR. Staining of vascular endothelial growth factor (VEGF) and intratumoral microvessel density (iMVD, labeled by CD105) were assessed by immunohistochemistry. Furthermore, cell migration and invasion were evaluated by wound healing assay and transwell assays. AEG-1 mRNA level was significantly higher in human lung cancer cells and TTs than that in human normal bronchial epithelial cell line 16HBE and PMNATs, respectively (P<0.001). Higher AEG-1 mRNA level in patients with NSCLC was correlated with clinical stages (P=0.028), differentiation (P=0.042), and lymph node metastasis (P=0.004). Moreover, Upregulated AEG-1 mRNA expression level was associated with higher tumor angiogenesis, reflected by the increase of VEGF expression and iMVD counting (P=0.021, P<0.001). However, 95D cell line transfected with AEG-1 siRNA oligos (siAEG-1) exhibited no significant decrease of cell invasion or migration capacities when compared with the control cells (P>0.05).These results suggested that AEG-1 may play important roles at the transcription level in malignant transformation and tumor angiogenesis in NSCLC, and anti-AEG-1 mRNA expression may be a novel potential strategy for anti-angiogenic therapy of NSCLC.

AEG-1 associates with metastasis in papillary thyroid cancer through upregulation of MMP2/9

Astrocyte elevated gene-1 (AEG-1), known as an oncogene, is overexpressed in various cancers and implicated in tumor progression and metastasis. However, its functional significance and underlying molecular mechanisms in thyroid cancer remain to be elucidated. In the present study, we detected the potential function of AEG-1 in papillary thyroid cancer (PTC). We also investigated the relation between AEG-1 and matrix metalloproteases (MMP)2 and 9 through immunohistochemistry, western blotting, real-time PCR, immunofluorescence staining, zymography and co-immunoprecipitation (Co-IP). We found that overexpression of AEG-1 in PTC was positively correlated with lymph node metastasis and MMP2/9 expression. Knockdown of AEG-1 reduced the capacity of migration and invasion through downregulation of MMP2/9 in thyroid cancer cells. Furthermore, we firstly found that AEG-1 interacted with MMP9 in thyroid cancer cells. AEG-1 was associated with the activation of the nuclear factor κB (NF-κB) signaling pathways in thyroid cancer cells. Overall, our results for the first time showed that AEG-1 interacted with MMP9 in thyroid cancer cells and AEG-1 expression was closely associated with progression and metastasis of papillary thyroid cancer. AEG-1 might be a potential therapeutic target in papillary thyroid cancer.

miR-217 inhibits laryngeal cancer metastasis by repressing AEG-1 and PD-L1 expression

High incidences of laryngeal cancer have been reported recently. Increasing our understanding of the molecular mechanisms underlying this malignancy could reveal more effective approaches to treating laryngeal cancer patients and so improve their prognoses. In this study, we explored the biological effects of miR-217 on laryngeal cancer. miR-217 potently inhibited multiple metastatic traits, including cell migration, invasion, proliferation, apoptosis, and EMT, as well as angiogensis. These effects were achieved through downregulation of the miR-217 target gene, AEG-1 and PD-L1. Clinical expression and animal model studies further confirmed our results. These findings provide new insight into the physiological effects of miR-217 in laryngeal cancer and its potential therapeutic use.

HIF-1α binding to AEG-1 promoter induced upregulated AEG-1 expression associated with metastasis in ovarian cancer

Ovarian cancer with the highest mortality rate among gynecological malignancies is one of common cancers among female cancer patients. As reported in recent years, AEG‐1 was associated with the occurrence, development, and metastasis of ovarian cancer, but the mechanisms remain unclear. In the current study, invasion capabilities of ovarian cancer OVCAR3 cells were measured by viral infection and transwell assay. Western blot analysis was used to evaluate the expression levels of β‐catenin, E‐cadherin, MMP2, and MMP9. With qRT‐PCR analysis, AEG‐1 and HIF‐1α gene expression were detected. We used luciferase reporter gene to measure AEG‐1 promoter activity under normoxia/hypoxia in OVCAR3 cells. Our work demonstrated that AEG‐1 significantly enhanced invasion capabilities of OVCAR3 cells and the expression levels of β‐catenin, E‐cadherin, MMP2, and MMP9 associated with invasion capabilities of OVCAR3 cells were upregulated. Furthermore, hypoxia enhanced invasion capabilities of OVCAR3 cells and induced AEG‐1 high gene expression, which was reversed by AEG‐1 knockdown lentivirus. HIF‐1α expression upregulation was induced in OVCAR3 cells after hypoxia. HIF‐1α knockdown lentivirus induced downregulated expression of AEG‐1 and invasion capabilities of OVCAR3 cells were also inhibited. Wild‐type AEG‐1 promoter activity under hypoxic conditions was significantly higher than that AEG‐1 mutation under normoxic conditions in the absence of hypoxia response. Our results suggested that HIF‐1α binds to AEG‐1 promoter to upregulate its expression, which was correlated with metastasis in ovarian cancer by inducing the expression of MMP2 and MMP9 as well as inhibiting expression of E‐cadherin and β‐catenin.

Knockdown of astrocyte elevated gene-1 inhibited cell growth and induced apoptosis and suppressed invasion in ovarian cancer cells

Emerging evidence has demonstrated that AEG-1 (astrocyte elevated gene-1) plays a pivotal oncogenic role in tumorigenesis. However, the molecular mechanism by which AEG-1 exerts its oncogenic function is elusive in ovarian cancer. To explore the role and molecular insight on AEG-1-mediated tumorigenesis in ovarian cancer, multiple approaches are performed including MTT assay, flow cytometry for apoptosis and cell cycle assay, gene transfection, real-time RT-PCR, Western blotting, and Transwell assay. Our MTT assay showed that knockdown of AEG-1 by its siRNA significantly inhibited cell growth in ovarian cancer cells. Moreover, AEG-1 siRNA treatment induced G₀/G₁ cell cycle arrest and triggered cell apoptosis in ovarian cancer cells. Notably, inhibition of AEG-1 suppressed cell migration and invasion in ovarian cancer cells. Intriguingly, we identified that knockdown of AEG-1 remarkably inhibited the activation of Akt pathway. Our results also validated that knockdown of AEG-1 inhibited the expression of MMP-2 and VEGF, which could lead to inhibition of cell migration and invasion. These data suggest that AEG-1 could be a potential therapeutic target for the treatment of ovarian cancer.

Association of MTDH immunohistochemical expression with metastasis and prognosis in female reproduction malignancies: a systematic review and meta-analysis

Various literatures have demonstrated that overexpression of Metadherin (MTDH) is correlated with tumor metastasis and it can predict poor survival outcomes in female reproduction malignancies. In order to enhance the statistical power and reach a recognized conclusion, we conducted a systematic review and meta-analysis to thoroughly investigate the association of MTDH expression with tumor metastasis and survival outcomes following PRISMA guidelines. Odds ratios (ORs) and hazard ratios (HRs) were used to demonstrate the impact of MTDH on tumor metastasis and prognosis respectively. Data were pooled with appropriate effects model on STATA12.0. Our results indicated that high MTDH expression is significantly correlated with higher mortality for breast, ovarian and cervical cancer. High immunohistochemical expression of MTDH is remarkably associated with shorter disease-free survival (DFS) in breast cancer but not in ovarian cancer. The pooled results suggested that high level of MTDH significantly predicted distant metastasis and lymph node metastasis in breast cancer. Strong associations were observed between MTDH expression and lymph node metastasis in ovarian and cervical cancer. In conclusion, MTDH might be a novel biomarker which can effectively reflect metastasis status and prognosis of breast cancer. However, its application in clinical practice needs more prospective studies with large samples.

A metabolic labeling approach for glycoproteomic analysis reveals altered glycoprotein expression upon GALNT3 knockdown in ovarian cancer cells

Epithelial ovarian cancer (EOC) is a disease responsible for more deaths among women in the Western world than all other gynecologic malignancies. There is urgent need for new therapeutic targets and a better understanding of EOC initiation and progression. We have previously identified the polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3) gene, a member of the GalNAc-transferases (GalNAc-Ts) gene family, as hypomethylated and overexpressed in high-grade serous EOC tumors, compared to low malignant potential EOC tumors and normal ovarian tissues. This data also suggested for a role of GALNT3 in aberrant EOC glycosylation, possibly implicated in disease progression. To evaluate differential glycosylation in EOC caused by modulations in GALNT3 expression, we used a metabolic labeling strategy for enrichment and mass spectrometry-based characterization of glycoproteins following GALNT3 gene knockdown (KD) in A2780s EOC cells. A total of 589 differentially expressed glycoproteins were identified upon GALNT3 KD. Most identified proteins were involved in mechanisms of cellular metabolic functions, post-translational modifications, and some have been reported to be implicated in EOC etiology. The GALNT3-dependent glycoproteins identified by this metabolic labeling approach support the oncogenic role of GALNT3 in EOC dissemination and may be pursued as novel EOC biomarkers and/or therapeutic targets.

BIOLOGICAL SIGNIFICANCE

Knowledge of the O-glycoproteome has been relatively elusive, and the functions of the individual polypeptide GalNAc-Ts have been poorly characterized. Alterations in GalNAc-Ts expression were shown to provide huge variability in the O-glycoproteome in various pathologies, including cancer. The application of a chemical biology approach for the metabolic labeling and subsequent characterization of O-glycoproteins in EOC using the Ac4GalNAz metabolite has provided a strategy allowing for proteomic discovery of GalNAc-Ts specific functions. Our study supports an essential role of one of the GalNAc-Ts - GALNT3, in EOC dissemination, including its implication in modulating PTMs and EOC metabolism. Our approach validates the use of the applied metabolic strategy to identify important functions of GalNAc-Ts in normal and pathological conditions.

AEG-1 Promotes Metastasis Through Downstream AKR1C2 and NF1 in Liver Cancer

Liver cancer is one of the most lethal cancers, but our knowledge of the molecular mechanism underlying this process remains insufficient. Through deep sequencing and expression regulation analysis in liver cancer cells, we identified two novel factors, AKR1C2 (positive factor) and NF1 (negative factor), as the AEG-1 downstream players in the process of metastasis in liver cancer. They were experimentally validated to have the capacities of regulating cell migration, cell invasion, cell proliferation, and EMT. Further clinic expression and animal model evidence confirmed their functions. Together, our findings provide a new insight into the pharmaceutical and therapeutic use of AEG-1 and downstream AKR1C2 and NF1.

AEG-1 participates in high glucose-induced activation of Rho kinase and epithelial-mesenchymal transition in proximal tubular epithelial cells

OBJECTIVE

To prove whether astrocyte elevated gene-1 (AEG-1) plays a role in high glucose-stimulated Rho kinase activation and epithelial-mesenchymal transition (EMT) in human renal tubular epithelial (HK-2) cells.

METHODS

The protein levels of AEG-1, alpha-smooth muscle actin, E-cadherin and MYPT1 were determined by Western blot.

RESULTS

AEG-1 protein level was upregulated in HK-2 cells stimulated with high glucose. AEG-1 siRNA downregulated Rho kinase protein expression and blocked high glucose-induced EMT.

CONCLUSIONS

Our results show that AEG-1 acts a key role in high glucose-induced activation of Rho kinase and EMT in HK-2 cells.

RNA interference-mediated knockdown of astrocyte elevated gene-1 inhibits growth, induces apoptosis, and increases the chemosensitivity to 5-fluorouracil in renal cancer Caki-1 cells

Astrocyte elevated gene-1 (AEG-1) is a recently discovered oncogene that has been reported to be highly expressed in various types of malignant tumors, including renal cell carcinoma. However, the precise role of AEG-1 in renal cancer cell proliferation and apoptosis has not been clarified. In this study, we transfected the renal cancer cell line Caki-1 with a plasmid expressing AEG-1 short hairpin RNA (shRNA) and obtained cell colonies with stable knockdown of AEG-1. We found that AEG-1 down-regulation inhibited cell proliferation and colony formation and arrested cell cycle progression at the sub-G1 and G0/G1 phase. Western blot analysis indicated that the expression of proliferating cell nuclear antigen (PCNA), cyclin D1 and cyclin E were significantly reduced following AEG-1 down-regulation. In addition, AEG-1 knockdown led to the appearance of apoptotic bodies in renal cancer cells, and the ratio of apoptotic cells significantly increased. Expression of the anti-apoptotic factor Bcl-2 was dramatically reduced, whereas the pro-apoptotic factors Bax, caspase-3 and poly (ADP-ribose) polymerase (PARP) were significantly activated. Finally, AEG-1 knockdown in Caki-1 cells remarkably suppressed cell proliferation and enhanced cell apoptosis in response to 5-fluorouracil (5-FU) treatment, suggesting that AEG-1 inhibition sensitizes Caki-1 cells to 5-FU. Taken together, our data suggest that AEG-1 plays an important role in renal cancer formation and development and may be a potential target for future gene therapy for renal cell carcinoma.

Overexpression of astrocyte-elevated gene-1 is associated with ovarian cancer development and progression

It has previously been reported that astrocyte‑elevated gene‑1 (AEG‑1) has a critical role in the regulation of tumor development, and/or progression. However, the functional significance of AEG‑1 in human ovarian cancer remains unclear. The present study conducted an immunohistochemical analysis of ovarian tissues, and the association between AEG‑1 protein expression, clinicopathological features and outcomes were investigated. The gain or loss of AEG‑1 function was also examined, through exogenous overexpression or knockdown of expression by small interfering RNA, in ovarian cancer cells. Normal ovarian tissue exhibited very little or no AEG‑1 immunoreactivity, whereas high expression levels of AEG‑1 were detected in 12.7% of cystadenomas, 30.0% of borderline tumors, and 71.2% of ovarian carcinomas, respectively, as determined by immunohistochemistry. Statistical analyses demonstrated a significant correlation of AEG‑1 expression with differentiation (P=0.001), lymph node metastasis (P=0.008) and clinical staging (P=0.002). In addition, the overall survival time of patients with higher AEG‑1 expression levels was markedly shorter, as compared with patients with lower expression levels of AEG‑1 (P=0.001). Multivariate analysis indicated that AEG‑1 expression was an independent prognostic indicator of the survival of patients with ovarian cancer. Furthermore, exogenous overexpression of AEG‑1 in ovarian cancer cells was shown to significantly enhance cell proliferation, adhesion and invasion. Conversely, silencing AEG‑1 expression caused an inhibition of cell growth, adhesion and invasion. The results of the present study indicate that AEG‑1 is a valuable biomarker for the prediction of ovarian cancer prognosis, and AEG‑1 inhibition may be a potential therapeutic strategy for ovarian cancer treatment.

Metadherin exon 11 skipping variant enhances metastatic spread of ovarian cancer

Metastatic ovarian cancer has a dismal prognosis and current chemotherapeutic approaches have very limited success. Metadherin (MTDH) is expressed in human ovarian cancer tissue and its expression inversely correlates with patients overall survival. Consistent with these studies, we observed MTDH expression in tissue specimens of FIGO Stage III ovarian carcinomas (72/83 cases). However, we also observed this in normal human ovarian epithelial (OE) cells, which raised the question of whether MTDH-variants with functional differences exist. We identified a novel MTDH exon 11 skipping variant (MTDHdel) which was seen at higher levels in ovarian cancer compared to benign OE cells. We analyzed MTDH-binding partner interactions and found that 12 members of the small ribosomal subunit and several mRNA binding proteins bound stronger to MTDHdel than to wildtype MTDH which indicates differential effects on gene translation. Knockdown of MTDH in ovarian cancer cells reduced the amount of distant metastases and improved the survival of ovarian cancer-bearing mice. Selective overexpression of the MTDHdel enhanced murine and human ovarian cancer progression and caused a malignant phenotype in originally benign human OE cells. MTDHdel was detectable in microdissected ovarian cancer cells of some human tissue specimens of ovarian carcinomas. In summary, we have identified a novel MTDH exon 11 skipping variant that shows enhanced binding to small ribosomal subunit members and that caused reduced overall survival of ovarian cancer bearing mice. Based on the findings in the murine system and in human tissues, MTDHdel must be considered a major promalignant factor for ovarian cancer.

Metadherin expression and lung relapse in patients with colorectal carcinoma

Colorectal cancer (CRC) is the third most common malignant disease in men and the second in women worldwide. CRC relapse occurs mostly in liver and lungs, decreasing the 5-year survival to 6 %. Metadherin (MTDH) is overexpressed in several types of cancer, has been implicated in proliferation, invasion, metastasis, angiogenesis, and chemoresistance, and is a factor of poor prognosis in CRC. In this work we addressed the prognostic significance of MTDH expression in CRC progression to the lungs. We found that MTDH gene was more frequently amplified (copy number >1.8) in patients with CRC and relapse to the lung, when compared to patients without lung metastases (17.4 vs 100 %; p < 0.001). We observed a correlation between MTDH gene copy number and MTDH expression by IHC (p = 0.0001). Next we also analyzed MTDH expression by IHC in samples from 85 patients diagnosed with CRC, stage II or III, M0, with at least 3 years of follow-up. Kaplan-Meier survival analysis showed that lung relapse-free survival (HR 5.29, 95 % CI 1.90-14.77, p = 0.0004), liver relapse-free survival (HR 8.59, 95 % CI 0.99-74.18, p = 0.003), relapse-free survival (HR 4.85, 95 % CI 1.88-12.45, p = 0.0003) and overall survival (HR 3.75, 95 % CI 1.15-12.18, p = 0.018) were significantly lower in the group with high MTDH expression. Multivariate analysis showed that high MTDH expression was an independent factor for all outcomes. This study demonstrates that high MTDH expression is a biomarker of relapse in CRC, including lung-specific relapse. Determination of MTDH expression in primary CRC may be useful in the earlier detection of lung metastases in patients with high expression and increased risk.

Astrocyte elevated gene-1: a novel independent prognostic biomarker for metastatic ovarian tumors

Astrocyte elevated gene-1 (AEG-1), a novel tumor-associated gene, was found overexpressed in many tumors. Therefore, our purpose is to estimate whether AEG-1 overexpression is a novel predictor of prognostic marker in metastatic ovarian tumors. Immunohistochemistry was used to estimate AEG-1 overexpression in metastatic ovarian tumors from 102 samples. The association between AEG-1 expression and prognosis was estimated by univariate and multivariate survival analyses with Cox regression. The log-rank test was used to identify any differences in the prognosis between the two groups. The median overall and progression-free survival rates of patients with tumors from gastrointestinal tract origin were 0.97 and 0.51 years, respectively. Similarly, survival rates of patients with tumors of breast origin were 2.68 and 1.96 years (P < 0.0001). Of 102 patients, 77 had high expression, and AEG-1 overexpression had a significant link of prognosis in metastatic ovarian patients (P < 0.01). On the other hand, medians of overall survival and progression-free survival of patients with tumors of gastrointestinal tract origin were significantly lower than those of patients with tumors of breast origin (P < 0.0001). Patients with metastatic ovarian tumors of breast origin had significantly better prognosis than those with the tumors from gastrointestinal tract primary malignancies. It is suggested that AEG-1 overexpression might be an independent prognostic marker of metastatic ovarian tumors.

Progress of cancer research on astrocyte elevated gene-1/Metadherin (Review)

Tumor development is initiated by an accumulation of numerous genetic and epigenetic alterations that promote tumor initiation, invasion and metastasis. Astrocyte elevated gene-1 [AEG-1; also known as Metadherin (MTDH) and Lysine-rich CEACAM1 co-isolated (LYRIC)] has emerged in recent years as a potentially crucial mediator of tumor malignancy, and a key converging point of a complex network of oncogenic signaling pathways. AEG-1/MTDH has a multifunctional role in tumor development that has been found to be involved in the following signaling cascades: i) The Ha-Ras and PI3K/Akt pathways; ii) the nuclear factor-κB signaling pathway; iii) the ERK/mitogen-activated protein kinase and Wnt/β-catenin pathways; and iv) the Aurora-A kinase signaling pathway. Studies have established that AEG-1/MTDH is crucial in tumor progression, including transformation, the evasion of apoptosis, invasion, angiogenesis and metastasis. In addition, recent clinical studies have convincingly associated AEG-1/MTDH with tumor progression and poor prognosis in a number of cancer types, including hepatocellular, esophageal squamous cell, gallbladder and renal cell carcinomas, breast, non-small cell lung, prostate, gastric and colorectal cancers, and glioma, melanoma, neuroblastoma and osteosarcoma. AEG-1/MTDH may be used as a biomarker to identify subgroups of patients who require more intensive treatments and who are likely to benefit from AEG-1/MTDH-targeted therapies. The therapeutic targeting of AEG-1/MTDH may simultaneously block metastasis, suppress tumor growth and enhance the efficacy of chemotherapeutic treatments.

Metadherin, p50, and p65 expression in epithelial ovarian neoplasms: an immunohistochemical study

NF-κB signaling promotes cancer progression in a large number of malignancies. Metadherin, a coactivator of the NF-κB transcription complex, was recently identified to regulate different signaling pathways that are closely related to cancer. We assessed the immunohistochemical expression of p50, p65, and metadherin in 30 ovarian carcinomas, 15 borderline ovarian tumours, and 31 benign ovarian cystadenomas. Ovarian carcinomas exhibited significantly higher expression of all 3 markers compared to benign ovarian tumours. Borderline ovarian tumours demonstrated significantly higher expression for all 3 markers compared to benign cystadenomas. Ovarian carcinomas demonstrated significantly higher expression of p50 and metadherin compared to borderline ovarian tumours, whereas no significant difference was noted in p65 expression between ovarian carcinomas and borderline ovarian tumours. There was a strong correlation with the expression levels of p50, p65, and metadherin, whereas no correlation was observed with either grade or stage. Strong p50, p65, and metadherin expression was associated with a high probability to distinguish ovarian carcinomas over borderline and benign ovarian tumours, as well as borderline ovarian tumours over benign ovarian neoplasms. A gradual increase in the expression of these molecules is noted when moving across the spectrum of ovarian carcinogenesis, from borderline ovarian tumours to epithelial carcinomas.

Astrocyte elevated gene-1 activates MMP9 to increase invasiveness of colorectal cancer

The molecular mechanism underlying the invasiveness of colorectal cancer (CRC) cells remains largely unknown. Here, we found that astrocyte elevated gene-1 (AEG-1) was significantly upregulated in CRC tissues, compared with the adjacent normal tissues from human patients. Ectopic expression of AEG-1 enhanced the invasive ability of CRC cells, while small interfering RNA (siRNA)-induced knockdown of AEG-1 inhibited the invasive ability of CRC cells. Transcription, protein levels, and secretion of matrix metalloproteinase 9 (MMP9), all increased by AEG-1 overexpression in CRC cells, and all decreased by AEG-1 inhibition. Suppression of endogenous MMP9 abrogated the effects of AEG-1 on invasiveness, without affecting AEG-1 levels. Taken together, these findings suggest that AEG-1 contributes to CRC invasiveness and metastasis by enhancing MMP9 activity. Thus, AEG-1 appears to be a novel therapeutic target for preventing the metastasis of CRC.

AEG-1/MTDH/LYRIC: clinical significance

"Gain-of-function" and "loss-of-function" studies in human cancer cells and analysis of a transgenic mouse model have convincingly established that AEG-1/MTDH/LYRIC performs a seminal role in regulating proliferation, invasion, angiogenesis, metastasis, and chemoresistance, the salient defining hallmarks of cancer. These observations are strongly buttressed by clinicopathologic correlations of AEG-1/MTDH/LYRIC expression in a diverse array of cancers distinguishing AEG-1/MTDH/LYRIC as an independent biomarker for highly aggressive metastatic disease with poor prognosis. AEG-1/MTDH/LYRIC has been shown to be a marker predicting response to chemotherapy, and serum anti-AEG-1/MTDH/LYRIC antibody titer also serves as a predictor of advanced stages of aggressive cancer. However, inconsistent findings have been reported regarding the localization of AEG-1/MTDH/LYRIC protein in the nucleus or cytoplasm of cancer cells and the utility of nuclear or cytoplasmic AEG-1/MTDH/LYRIC to predict the course and prognosis of disease. This chapter provides a comprehensive analysis of the existing literature to emphasize the common and conflicting findings relative to the clinical significance of AEG-1/MTDH/LYRIC in cancer.

AEG-1/MTDH/LYRIC: signaling pathways, downstream genes, interacting proteins, and regulation of tumor angiogenesis

Astrocyte elevated gene-1 (AEG-1), also known as metadherin (MTDH) and lysine-rich CEACAM1 coisolated (LYRIC), was initially cloned in 2002. AEG-1/MTDH/LYRIC has emerged as an important oncogene that is overexpressed in multiple types of human cancer. Expanded research on AEG-1/MTDH/LYRIC has established a functional role of this molecule in several crucial aspects of tumor progression, including transformation, proliferation, cell survival, evasion of apoptosis, migration and invasion, metastasis, angiogenesis, and chemoresistance. The multifunctional role of AEG-1/MTDH/LYRIC in tumor development and progression is associated with a number of signaling cascades, and recent studies identified several important interacting partners of AEG-1/MTDH/LYRIC in regulating cancer promotion and other biological functions. This review evaluates the current literature on AEG-1/MTDH/LYRIC function relative to signaling changes, interacting partners, and angiogenesis and highlights new perspectives of this molecule, indicating its potential as a significant target for the clinical treatment of various cancers and other diseases.

AEG-1/MTDH/LYRIC, the beginning: initial cloning, structure, expression profile, and regulation of expression

Since its initial identification as a HIV-1-inducible gene in 2002, astrocyte elevated gene-1 (AEG-1), subsequently cloned as metadherin (MTDH) and lysine-rich CEACAM1 coisolated (LYRIC), has emerged over the past 10 years as an important oncogene providing a valuable prognostic marker in patients with various cancers. Recent studies demonstrate that AEG-1/MTDH/LYRIC is a pleiotropic protein that can localize in the cell membrane, cytoplasm, endoplasmic reticulum (ER), nucleus, and nucleolus, and contributes to diverse signaling pathways such as PI3K-AKT, NF-κB, MAPK, and Wnt. In addition to tumorigenesis, this multifunctional protein is implicated in various physiological and pathological processes including development, neurodegeneration, and inflammation. The present review focuses on the discovery of AEG-1/MTDH/LYRIC and conceptualizes areas of future direction for this intriguing gene. We begin by describing how AEG-1, MTDH, and LYRIC were initially identified by different research groups and then discuss AEG-1 structure, functions, localization, and evolution. We conclude with a discussion of the expression profile of AEG-1/MTDH/LYRIC in the context of cancer, neurological disorders, inflammation, and embryogenesis, and discuss how AEG-1/MTDH/LYRIC is regulated. This introductory discussion of AEG-1/MTDH/LYRIC will serve as the basis for the detailed discussions in other chapters of the unique properties of this intriguing molecule.

Regulation of the localisation and function of the oncogene LYRIC/AEG-1 by ubiquitination at K486 and K491

The pivotal role of LYRIC/AEG‐1 in malignant transformation, tumourigenesis and chemo‐resistance has previously been demonstrated in different cell types and sub‐cellular compartments. The localisation of LYRIC/AEG‐1 appears crucial to its function and is regulated by three lysine‐rich nuclear localisation signal regions, one of which was previously demonstrated to be modified by ubiquitin. Here we show that mutation of LYRIC/AEG‐1 at K486 and K491 results in a loss of ubiquitination. A K486/491R double mutant that is incapable of ubiquitination shows reduced binding to the NFκB subunit p65 or importin‐β resulting in a distinctive peri‐nuclear localisation of LYRIC/AEG‐1. We also provide evidence to suggest that TOPORS, an E3 ligase that also regulates p53 modification may be responsible for LYRIC/AEG‐1 ubiquitin modification. Overall we demonstrate that specific sites of LYRIC/AEG‐1 ubiquitination are essential for regulating LYRIC/AEG‐1 localisation and functionally interacting proteins.

LYRIC/AEG‐1 is an important oncogene.

2 specific lysine residues in exNLS‐2 are ubiquitinated.

Deletion of both lysine residues changes localisation and interaction with p65.

LYRIC/AEG‐1 interacts with TOPORS, a known E3 ligase.

AU-binding factor 1 expression was correlated with metadherin expression and progression of hepatocellular carcinoma

RNA-binding factor 1 (AUF1) was found to be up-regulated in numerous tumors compared with untransformed tissues. Furthermore, it has been identified to regulate mRNAs en masse in hepatocellular carcinoma (HCC). Metadherin (MTDH) as a novel oncogene also promotes tumor progression and metastasis in HCC. Our study aimed to investigate the correlation between AUF1 and MTDH expressions by immunochemistry in 146 HCC patients from Heilongjiang region. AUF1 expression in HCC tumors was higher than that in the matched normal liver tissues. Particularly, AUF1 overexpression was closely associated with tumor size (P < 0.022), TNM stage (P < 0.003), hepatitis B surface antigen status, and AFP serum levels (P < 0.05). Furthermore, AUF1 overexpression led to poor outcome during 5-year follow-up (P < 0.001). Additionally, AUF1 and MTDH expressions were correlated with each other. Our findings suggest that the AUF1 gene may play an important role in HCC progression and be a novel biomarker in the future.

Astrocyte elevated gene-1 is a novel biomarker of epithelial-mesenchymal transition and progression of hepatocellular carcinoma in two China regions

Astrocyte elevated gene-1 (AEG-1) is involved in important biological processes including cell invasion, metastasis, and carcinogenesis. However, its clinical significance has remained largely unknown in hepatocellular carcinoma. Here, specimens from 144 patients with hepatocellular carcinomas in Beijing and Heilongjiang regions were investigated by immunohistochemical staining for AEG-1, vimentin, and E-cadherin expressions. A clinicopathological study revealed that AEG-1 expression level in tumor cells was significantly correlated with TNM stage (P = 0.001) and Edmonson grade (P < 0.0001). In addition, AEG-1, vimentin, and E-cadherin (epithelial-mesenchymal transition (EMT) biomarker) expressions were correlated with each other. These findings suggest that AEG-1 may be an epithelial-mesenchymal transition-associated biomarker in human hepatocellular carcinoma and play important roles in the progression of hepatocellular carcinoma. In addition, the AEG-1 gene is a potential target for elimination of hepatocellular carcinoma in the future.

Establishment and characterization of MTDH knockdown by artificial MicroRNA interference - functions as a potential tumor suppressor in breast cancer

BACKGROUND

Considerable evidence suggests that metadherin (MTDH) is a potentially crucial mediator of tumor malignancy and an important therapeutic target for simultaneously enhancing chemotherapy efficacy and reducing metastasis risk. Inhibition of MTDH expression by RNA interference has been shown in several previous research, but silencing MTDH expression by microRNA (miRNA) interference in breast cancer has not been established. In the present study, we investigated the role of MTDH-miRNA in down-regulation of proliferation, motility and migration of breast carcinoma cells.

METHODS

Expression vectors of recombinant plasmids expressing artificial MTDH miRNA were constructed and transfected to knockdown MTDH expression in MDA-MB-231 breast cancer cells. Expression of MTDH mRNA and protein was detected by RT-PCR and Western blot, respectively. MTT assays were conducted to determine proliferation, and wound healing assays and transwell migration experiments for cell motility and migration.

RESULTS

Transfection of recombinant a plasmid of pcDNA-MTDH-miR-4 significantly suppressed the MTDH mRNA and protein levels more than 69% in MDA-MB-231 breast cancer cells. This knockdown significantly inhibited proliferation, motility and migration as compared with controls.

CONCLUSIONS

MTDH-miRNA may play an important role in down- regulating proliferation, motility and migration in breast cancer cells, and should be considered as a potential small molecule inhibitor therapeutic targeting strategy for the future.

The MTDH (-470G>A) polymorphism is associated with ovarian cancer susceptibility

MTDH (metadherin), an important oncogene that is widely overexpressed in various cancers, is a potential biomarker of tumor malignancy. Variants in MTDH have been associated with susceptibility to breast cancer. However, no studies assessing MTDH gene polymorphisms and their potential relationship to ovarian cancer susceptibility have been reported. Thus, we investigated the association of MTDH (-470G>A) polymorphism with ovarian cancer development in 145 ovarian cancer patients and 254 matched control subjects, using sequence analysis. We found that the MTDH (-470G>A) polymorphism was statistically correlated with ovarian cancer risk (under the additive genetic model, GG vs. GA vs AA, P = 0.042). Compared with genotypes containing the G allele (GG and GA), the AA genotype may decrease the risk of ovarian cancer (P = 0.0198, OR = 0.33, 95% CI [0.12∼0.78]). Compared with the G allele, the A allele is protective against ovarian cancer risk (P = 0.01756, OR = 0.66, 95% CI [0.46∼0.93]). Furthermore, a statistically significant association between the GG and GA+AA genotypes and the clinical stage was observed (P = 0.038). These data suggest that MTDH (-470G>A) could be a useful molecular marker for assessing ovarian cancer risk and for predicting ovarian cancer patient prognosis.

Expression of AEG-1 in human T-cell lymphoma enhances the risk of progression

The aim of this study was to examine the expression and role of astrocyte elevated gene-1 (AEG-1) in biological processes of T-cell non-Hodgkin's lymphoma (T-NHL). AEG-1 expression in T-NHL patients was characterized with immunohistochemistry. The expression of AEG-1, survivin, Bcl-2 and Bax in Jurkat and Hut-78 cells was detected by real-time PCR and western blotting. Cell proliferation, cell cycle and apoptosis were measured by MTT and flow cytometry. MMP-2/-9 activity was detected by gelatin zymography. Of the studied tumors, 104 (80.62%) exhibited cytoplasmic AEG-1 immunostaining. AEG-1-siRNA in Jurkat and Hut-78 cells suppressed cell proliferation and induced cell apoptosis, inhibited survivin and Bcl-2/Bax protein expression as well as MMP-2/-9 activity. Downregulation of AEG-1 using siRNA could provide a potential approach for gene therapy against T-NHL, and the antitumor effects may be associated with inhibition of survivin and Bcl-2/Bax protein expression and MMP-2/-9 activity.

Inhibition of metadherin sensitizes breast cancer cells to AZD6244

The development of systemic therapy drug resistance for breast cancer treatment is an ongoing problem, thus, so are the potential molecular mechanisms of it. AZD6244 is a novel ATP-uncompetitive inhibitor to MAP/ERK kinase (MEK) 1/2 which has been demonstrated to be potent, selective and safe in the clinical trials and previous studies. However, the precise role of resistance to AZD6244 is largely unknown. We and other groups have reported that the novel oncogene Metadherin (MTDH) is associated with multiple drug resistance, but there is no report about its role in treatment of AZD6244. Here we report that the resistance to AZD6244 can be reserved by downregulating MTDH in breast cancer cell lines. When the MTDH was downregulated, the breast cancer cells exhibited a significantly increased sensitivity to AZD6244 as measured by MTT assay. After treated with AZD6244 the MTDH-knockdown cells showed more apoptosis rate and growth inhibition. We also showed that knockdown of MTDH cannot only increase expression of FOXO3a but also activate it by promoting its translocation via MTDH/ERK1/2/FOXO3a pathway rather than MTDH/AKT/FOXO3a pathway. In conclusion knockdown MTDH can enhance the breast cancer cells sensitivity to AZD6244 via regulating the expression and activity of FOXO3a. These indicate us that MTDH is a candidate marker to predict the clinical efficacy of AZD6244 and targeting MTDH could overcome the resistance to AZD6244 in breast cancer cells.

Does tumour biology determine surgical success in the treatment of epithelial ovarian cancer? A systematic literature review

Background:

Ovarian cancer is the most lethal gynaecological cancer. Progression-free and overall survival is significantly related to surgical success and residual disease volume. It is unclear whether this survival advantage is due to an intrinsic biological element of the tumour cells which enables successful surgery and improved prognosis, or alternatively the number of tumour sustaining cells remaining irrespective of differences in biology.

Methods:

A systematic review of the literature was performed identifying studies that have investigated the association between biomarkers and surgical outcomes. We attempted validation of these results using The Cancer Genome Atlas ovarian cancer data sets.

Results:

Thirty studies were identified of which sixteen determined protein expression, eight gene expression and one DNA methylation in association with surgical debulking. Individualised linear models adjusting for batch, stage and age identified only expression of the genes MTDH and insulin-like growth factor-1 receptor (IGF1R) to be significantly associated with debulking surgery (P<0.05, false discovery rate (FDR)<5%), although in the case of IGF1R this was in the opposite direction to previous findings.

Conclusion:

The majority of studies are limited by design, include heterogeneous samples and lack adjustment for major confounding factors. High quality detailed clinical annotations should be routinely collected in future to more accurately evaluate biomarkers of surgical outcome.

Elevated expression of astrocyte elevated gene-1 (AEG-1) is correlated with cisplatin-based chemoresistance and shortened outcome in patients with stages III-IV serous ovarian carcinoma

AIMS

To correlate astrocyte elevated gene-1 (AEG-1) expression with the clinicopathological features and outcome of patients with stages III-IV ovarian serous carcinoma, and to clinically assess the involvement of AEG-1 in acquired cisplatin resistance.

METHODS AND RESULTS

The frequency and intensity of immunohistochemical AEG-1 expression increased in a step-wise fashion from normal to chemosensitive to chemoresistant tissues. These observations were confirmed by Western blot analysis. AEG-1 expression level was correlated with lymph nodal metastasis, histological differentiation, residual tumour size and response to primary chemotherapy. Five-year progression-free survival (PFS) and overall survival (OS) rates were lower in the high-expression group than that in the low-expression group. AEG-1 overexpression was an independent but poor prognostic factor in the OS and PFS of these patients, as determined by multivariate Cox regression analysis. Multivariate logistic regression analysis revealed that the presence of cisplatin-based chemoresistance was significantly associated with expression level of AEG-1 and the degree of residual disease (P = 0.0001 and P = 0.0027, respectively).

CONCLUSION

Our findings indicate that tumour AEG-1 overexpression is associated with poor prognosis and cisplatin resistance in advanced serous ovarian cancer.

Cytoplasmic Metadherin (MTDH) provides survival advantage under conditions of stress by acting as RNA-binding protein

Overexpression of metadherin (MTDH) has been documented in many solid tumors and is implicated in metastasis and chemoresistance. MTDH has been detected at the plasma membrane as well as in the cytoplasm and nucleus, and the function of MTDH in these locales remains under investigation. In the nucleus, MTDH acts as a transcription co-factor to induce expression of chemoresistance-associated genes. However, MTDH is predominantly cytoplasmic in prostate tumors, and this localization correlates with poor prognosis. Herein, we used endometrial cancer cells as a model system to define a new role for MTDH in the cytoplasm. First, MTDH was primarily localized to the cytoplasm in endometrial cancer cells, and the N-terminal region of MTDH was required to maintain cytoplasmic localization. Next, we identified novel binding partners for cytoplasmic MTDH, including RNA-binding proteins and components of the RNA-induced silencing complex. Nucleic acids were required for the association of MTDH with these cytoplasmic proteins. Furthermore, MTDH interacted with and regulated protein expression of multiple mRNAs, such as PDCD10 and KDM6A. Depletion of cytoplasmic MTDH was associated with increased stress granule formation, reduced survival in response to chemotherapy and the tyrosine kinase inhibitor BIBF1120, Rad51 nuclear accumulation, and cell cycle arrest at G(2)/M. Finally, in vivo tumor formation was abrogated with knockdown of cytoplasmic MTDH. Taken together, our data identify a novel function for cytoplasmic MTDH as an RNA-binding protein. Our findings implicate cytoplasmic MTDH in cell survival and broad drug resistance via association with RNA and RNA-binding proteins.