Loss of anterior gradient-2 expression is an independent prognostic factor in colorectal carcinomas. Eur J Cancer. 2014;50:1722-1730. [PMID: 24794000 DOI: 10.1016/j.ejca.2014.04.012]

AGR2: The Covert Driver and New Dawn of Hepatobiliary and Pancreatic Cancer Treatment

The anterior gradient protein 2 (AGR2) plays a crucial role in facilitating the formation of protein disulfide bonds within the endoplasmic reticulum (ER). Research suggests that AGR2 can function as an oncogene, with its heightened expression linked to the advancement of hepatobiliary and pancreatic cancers through invasion and metastasis. Notably, AGR2 not only serves as a pro-oncogenic agent but also as a downstream targeting protein, indirectly fostering cancer progression. This comprehensive review delves into the established functions and expression patterns of AGR2, emphasizing its pivotal role in cancer progression, particularly in hepatobiliary and pancreatic malignancies. Furthermore, AGR2 emerges as a potential cancer prognostic marker and a promising target for immunotherapy, offering novel avenues for the treatment of hepatobiliary and pancreatic cancers and enhancing patient outcomes.

Anterior gradient proteins in gastrointestinal cancers: from cell biology to pathophysiology

Most of the organs of the digestive tract comprise secretory epithelia that require specialized molecular machines to achieve their functions. As such anterior gradient (AGR) proteins, which comprise AGR1, AGR2, and AGR3, belong to the protein disulfide isomerase family, and are involved in secretory and transmembrane protein biogenesis in the endoplasmic reticulum. They are generally expressed in epithelial cells with high levels in most of the digestive tract epithelia. To date, the vast majority of the reports concern AGR2, which has been shown to exhibit various subcellular localizations and exert pro-oncogenic functions. AGR2 overexpression has recently been associated with a poor prognosis in digestive cancers. AGR2 is also involved in epithelial homeostasis. Its deletion in mice results in severe diffuse gut inflammation, whereas in inflammatory bowel diseases, the secretion of AGR2 in the extracellular milieu participates in the reshaping of the cellular microenvironment. AGR2 thus plays a key role in inflammation and oncogenesis and may represent a therapeutic target of interest. In this review, we summarize the already known roles and mechanisms of action of the AGR family proteins in digestive diseases, their expression in the healthy digestive tract, and in digestive oncology. At last, we discuss the potential diagnostic and therapeutic implications underlying the biology of AGR proteins.

AGR2 and AGR3 play an important role in the clinical characterization and prognosis of basal like breast cancer

INTRODUCTION

Basal-like Breast Cancer (BLBC) represents an important molecular subtype of breast cancer characterized by an aggressive behavior, molecular pathology poorly understood and a limited treatment.

OBJECTIVE

We aim to search for molecular differences between non-BLBC and BLBC tumors in order to propose possible diagnostic and prognostic biomarkers using databases. Metodology: Microarray processed data were downloaded from GEO database considering non-BLBC and BLBC. Enrichment analysis was evaluated using GO consortium and Ingenuity, protein-protein interaction, gene Ontology and co-expression analysis using STRING. Gene expression data was extracted using TCGA, METABRIC and Breast Cancer Gene-Expression Miner v4.2 databases. The Survival was evaluated using The Kaplan-Meier plotter.

RESULTS

Were identified 58 upregulated and 58 downregulated genes enriched in signaling pathways like PDGF, Angiogenesis, Integrin and WNT. AGR2 and AGR3 expression were reduced in BLBC in relation to non-BLBC tumors, patients aged ≤51 years, and with negativity of ER, PR and HER-2 and nodal status. Low expression of AGR2 and AGR3 were associated with worse OS and RFS for all breast cancer cases. But according to the molecular stratification, low AGR2 conferred worst OS in luminal A, worst RFS in BLBC and good OS and RFS in luminal B. High AGR3 conferred worse OS and RFS in BLBC, but low AGR3 attributed worse OS in luminal A.

CONCLUSION

AGR2 and AGR3 expression were able to differentiate non-BLBC from BLBC. Downregulation of AGR2 and AGR3 was associated with BLBC clinical phenotype. Furthermore, both genes behave different when considering prognosis and molecular stratification.

AGR2 is controlled by DNMT3a-centered signaling module and mediates tumor resistance to 5-Aza in colorectal cancer

Human anterior gradient-2 (AGR2), a member of protein disulfide isomerase (PDI) family, is upregulated in various human cancers and reportedly has oncogenic activities. However, the functional roles of AGR2 and its regulation in colorectal cancer (CRC) remain unclear. Here, we showed that AGR2 promoted CRC tumorigenesis and progression in vitro and in vivo and acted as an independent prognostic factor of poor outcome. AGR2 was negatively regulated by DNA methyltransferase 3a (DNMT3a) through directly methylating AGR2 promoter and by a DNMT3a-SPRY2-miR-194 axis. Moreover, AGR2 mediated the resistance to 5-Aza-2'-deoxycytidine (5-Aza) treatment. Knockdown of AGR2 improved the therapeutic effect of 5-Aza in human CRC xenograft tumor model. Thus, our work supports AGR2's oncogenic role in CRC, reveals DNMT3a-mediated epigenetic modulation on AGR2 promoter, and uncovers a new DNMT3a signaling module controlling expression of AGR2. Upregulated AGR2 offset 5-Aza mediated epigenetic therapy. This work might provide potential targets for clinical anti-cancer therapy.

AGR2 silencing contributes to metformin-dependent sensitization of colorectal cancer cells to chemotherapy

There is growing epidemiological evidence indicating an association between diabetes mellitus and the increased incidence of colorectal cancer (CRC). The preferred initial and most widely used pharmacological agent for the treatment of type 2 diabetes is metformin, which in parallel reduces the risk of CRC and improves patient prognosis. AMP-activated protein kinase (AMPK) appears to be tightly associated with the beneficial metabolic effects of metformin, serving as a cellular energy sensor activated in response to a variety of conditions that deplete cellular energy levels. Such conditions include nutrient starvation (particularly glucose), hypoxia and exposure to toxins that inhibit the mitochondrial respiratory chain complex. The aim of the present study was to determine the effect of metformin on CRC cell lines, with different levels of anterior gradient 2 (AGR2) expression, exposed to 5-fluorouracil (5-FU) and oxaliplatin, alone or in combination with metformin. AGR2 has recently emerged as a factor involved in colon carcinogenesis. In AGR2-knockout cells, markedly higher levels of phosphorylated-AMPK were observed in comparison with control cells transfected with GFP-scrambled guide RNA, which indicated that the presence of AGR2 may interfere with the metformin-dependent activation of AMPK. In addition, metformin in combination with 5-FU and oxaliplatin induced ROS production and attenuated autophagy. This effect was enhanced in AGR2-knockout cells.

Impact of Heat Shock Protein 90 Inhibition on the Proteomic Profile of Lung Adenocarcinoma as Measured by Two-Dimensional Electrophoresis Coupled with Mass Spectrometry

Heat shock protein 90 (HSP90) is an important chaperone in lung adenocarcinoma, with relevant protein drivers such as EGFR (epidermal growth factor receptor) and EML4-ALK (echinoderm microtubule-associated protein-like protein4 fused to anaplastic lymphoma kinase) depending on it for their correct function, therefore HSP90 inhibitors show promise as potential treatments for lung adenocarcinoma. To study responses to its inhibition, HSP90 was pharmacologically interrupted by geldanamycin and resorcinol derivatives or with combined inhibition of HSP90 plus HSP70 in lung adenocarcinoma cell lines. Two-dimensional electrophoresis was performed to identify proteomic profiles associated with inhibition which will help to understand the biological basis for the responses. HSP90 inhibition resulted in altered protein profiles that differed according the treatment condition studied. Results revealed 254 differentially expressed proteins after treatments, among which, eukaryotic translation initiation factor3 subunit I (eIF3i) and citrate synthase demonstrated their potential role as response biomarkers. The differentially expressed proteins also enabled signalling pathways involved in responses to be identified; these included apoptosis, serine-glycine biosynthesis and tricarboxylic acid cycle. The proteomic profiles identified here contribute to an improved understanding of HSP90 inhibition and open possibilities for the detection of potential response biomarkers which will be essential to maximize treatment efficacy in lung adenocarcinoma.

Leveraging the Role of the Metastatic Associated Protein Anterior Gradient Homologue 2 in Unfolded Protein Degradation: A Novel Therapeutic Biomarker for Cancer

Effective diagnostic, prognostic and therapeutic biomarkers can help in tracking disease progress, predict patients’ survival, and considerably affect the drive for successful clinical management. The present review aims to determine how the metastatic-linked protein anterior gradient homologue 2 (AGR2) operates to affect cancer progression, and to identify associated potential diagnostic, prognostic and therapeutic biomarkers, particularly in central nervous system (CNS) tumors. Studies that show a high expression level of AGR2, and associate the protein expression with the resilience to chemotherapeutic treatments or with poor cancer survival, are reported. The primary protein structures of the seven variants of AGR2, including their functional domains, are summarized. Based on experiments in various biological models, this review shows an orchestra of multiple molecules that regulate AGR2 expression, including a feedback loop with p53. The AGR2-associated molecular functions and pathways including genomic integrity, proliferation, apoptosis, angiogenesis, adhesion, migration, stemness, and inflammation, are detailed. In addition, the mechanisms that can enable the rampant oncogenic effects of AGR2 are clarified. The different strategies used to therapeutically target AGR2-positive cancer cells are evaluated in light of the current evidence. Moreover, novel associated pathways and clinically relevant deregulated genes in AGR2 high CNS tumors are identified using a meta-analysis approach.

Downregulation of AGR2, p21, and cyclin D and alterations in p53 function were associated with tumor progression and chemotherapy resistance in epithelial ovarian carcinoma

Anterior gradient 2 protein belongs to a family of chaperone‐like proteins, namely protein disulfide isomerase. Generally, AGR2 is highly expressed in mucus‐secreting cells and endocrine organs, and in this study, we aimed to evaluate AGR2 and cell cycle molecules in epithelial ovarian cancer and its implications on prognosis. One hundred seventy‐five patient's samples that were diagnosed with primary epithelial ovarian carcinoma were selected. All the patients were treated with platinum‐taxane standard chemotherapy after surgery and CA125 serum levels were routinely determined. Four‐micrometer‐thick sections were processed by immunohistochemistry using an automated immunostainer, Ventana BenchMark AutoStainer with AGR2, cyclin D1, p21WAF1, and p53. Forty‐nine of 167 cases (29.3%) showed strong to moderate cytoplasmic marking of AGR2, and 118 (70.7%) had weak to negative expression. The absence of the AGR2 protein was observed in high‐grade serous carcinoma (P < .001) and significantly associated with disease‐free survival (DFS; P = .034). The expression of G1‐S phase‐regulatory proteins showed loss of p21 in high‐grade serous carcinoma (P < .001) and was related with poor DFS (P = .003). Strong and diffuse immunoexpression of p53 plus complete absence of p53 staining was interpreted as likely indicating a TP53 gene mutation. This result showed worse DFS alone (P = .012) and combined with low levels of AGR2 (P = .005). The expression profile of AGR2 and cell cycle proteins here presented was showed as good prognosis marker in epithelial ovarian cancer. This finding suggests AGR2 and as putative biomarker of disease progression in chemotherapy‐treated high‐grade serous carcinoma patients.

Secreted AGR2 promotes invasion of colorectal cancer cells via Wnt11-mediated non-canonical Wnt signaling

Human anterior gradient-2 (AGR2), a member of protein disulfide isomerase (PDI) family, is present in both intracellular and extracellular compartments. Although AGR2 is overexpressed in various human cancers and reported to promote aggressive tumor features, little is known regarding AGR2's extracellular functions during tumorigenesis. Here, we demonstrate that secreted AGR2 promotes cell migration and metastasis of colorectal cancer (CRC) in vitro and in vivo. Mechanistically, secreted AGR2 elevated Wnt11 expression, triggering non-canonical Wnt signaling: the Ca²⁺/Calmodulin-dependent protein kinase II (CaMKII) and c-jun amino-terminal kinase (JNK) pathways. Knockdown of Wnt11 or pretreatment with CaMKII and JNK inhibitors reversed the secreted AGR2's migration-promoting effect. Further studies revealed that AGR2 antagonized canonical Wnt/β-catenin signaling via activating CaMKII. Collectively, our study uncovers a critical role of Wnt11-mediated non-canonical Wnt signaling (CaMKII and JNK pathways) in secreted AGR2's promoted migration of CRC cells. These results raise the possibility that secreted AGR2 may be a potential therapeutic target towards inhibiting CRC metastasis.

FOXM1 activates AGR2 and causes progression of lung adenomas into invasive mucinous adenocarcinomas

Lung cancer remains one of the most prominent public health challenges, accounting for the highest incidence and mortality among all human cancers. While pulmonary invasive mucinous adenocarcinoma (PIMA) is one of the most aggressive types of non-small cell lung cancer, transcriptional drivers of PIMA remain poorly understood. In the present study, we found that Forkhead box M1 transcription factor (FOXM1) is highly expressed in human PIMAs and associated with increased extracellular mucin deposition and the loss of NKX2.1. To examine consequences of FOXM1 expression in tumor cells in vivo, we employed an inducible, transgenic mouse model to express an activated FOXM1 transcript in urethane-induced benign lung adenomas. FOXM1 accelerated tumor growth, induced progression from benign adenomas to invasive, metastatic adenocarcinomas, and induced SOX2, a marker of poorly differentiated tumor cells. Adenocarcinomas in FOXM1 transgenic mice expressed increased MUC5B and MUC5AC, and reduced NKX2.1, which are characteristics of mucinous adenocarcinomas. Expression of FOXM1 in KrasG12D transgenic mice increased the mucinous phenotype in KrasG12D-driven lung tumors. Anterior Gradient 2 (AGR2), an oncogene critical for intracellular processing and packaging of mucins, was increased in mouse and human PIMAs and was associated with FOXM1. FOXM1 directly bound to and transcriptionally activated human AGR2 gene promoter via the -257/-247 bp region. Finally, using orthotopic xenografts we demonstrated that inhibition of either FOXM1 or AGR2 in human PIMAs inhibited mucinous characteristics, and reduced tumor growth and invasion. Altogether, FOXM1 is necessary and sufficient to induce mucinous phenotypes in lung tumor cells in vivo.

The prognostic value of AGR2 expression in solid tumours: a systematic review and meta-analysis

The prognostic value of anterior gradient-2 (AGR2) in tumours remains inconclusive. Here, we systematically reviewed the literature evidence and assessed the association between AGR2 expression and prognosis in solid tumours. The primary outcomes were overall survival (OS), disease-specific survival (DSS), and disease-free survival (DFS)/recurrence-free survival (RFS)/progression-free survival (PFS). All analyses were performed by STATA 12.0, with the hazard ratio (HR) or odds ratios (OR), and 95% confidence interval (CI) as the effect size estimate. A total of 20 studies containing 3285 cases were included. Pooled analyses revealed that AGR2 overexpression had an unfavourable impact on OS (HR 1.93, 95% CI 1.32-2.81) and time to tumour progression (TTP) (DFS/RFS/PFS) (HR 1.60 95% CI 1.06-2.40) in solid tumour patients. Subgroup analyses indicated that AGR2 overexpression in breast cancer patients was significantly associated with poor OS (HR 3.02, 95% CI 1.03-8.81) and TTP (HR 1.93, 95% CI 1.17-3.20). Excluding breast cancer, AGR2 overexpression was also found to have a significant correlation with poor OS in the remaining solid tumour patients (HR 1.51, 95% CI 1.04-2.19). Overall, AGR2 might be a potential biomarker to predict prognosis in solid tumour patients.

Conjugation of gold nanoparticles and recombinant human endostatin modulates vascular normalization via interruption of anterior gradient 2-mediated angiogenesis

Several studies have revealed the potential of normalizing tumor vessels in anti-angiogenic treatment. Recombinant human endostatin is an anti-angiogenic agent which has been applied in clinical tumor treatment. Our previous research indicated that gold nanoparticles could be a nanoparticle carrier for recombinant human endostatin delivery. The recombinant human endostatin-gold nanoparticle conjugates normalized vessels, which improved chemotherapy. However, the mechanism of recombinant human endostatin-gold nanoparticle-induced vascular normalization has not been explored. Anterior gradient 2 has been reported to be over-expressed in many malignant tumors and involved in tumor angiogenesis. To date, the precise efficacy of recombinant human endostatin-gold nanoparticles on anterior gradient 2-mediated angiogenesis or anterior gradient 2-related signaling cohort remained unknown. In this study, we aimed to explore whether recombinant human endostatin-gold nanoparticles could normalize vessels in metastatic colorectal cancer xenografts, and we further elucidated whether recombinant human endostatin-gold nanoparticles could interrupt anterior gradient 2-induced angiogenesis. In vivo, it was indicated that recombinant human endostatin-gold nanoparticles increased pericyte expression while inhibit vascular endothelial growth factor receptor 2 and anterior gradient 2 expression in metastatic colorectal cancer xenografts. In vitro, we uncovered that recombinant human endostatin-gold nanoparticles reduced cell migration and tube formation induced by anterior gradient 2 in human umbilical vein endothelial cells. Treatment with recombinant human endostatin-gold nanoparticles attenuated anterior gradient 2-mediated activation of MMP2, cMyc, VE-cadherin, phosphorylation of p38, and extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) in human umbilical vein endothelial cells. Our findings demonstrated recombinant human endostatin-gold nanoparticles might normalize vessels by interfering anterior gradient 2-mediated angiogenesis in metastatic colorectal cancer.

Serum AGR2 as a useful biomarker for pituitary adenomas

OBJECTIVE

This study aims to evaluate whether the serum Anterior Gradient-2 (AGR2) can be used as a potential biomarker screening in the diagnosis of Pituitary adenomas(PAs).

PATIENTS AND METHODS

The serum AGR2 protein levels were preoperatively measured in 163 PA patients, 43 patients with other sellar lesions excluding PAs, 7 patients with prostate cancer as a positive control and 20 normal people(10 female and 10 male) using Enzyme-Linked ImmunoSorbent Assay (ELISA). Differences in the serum AGR2 level between different groups were analyzed for statistical significance with a Mann-Whitney U test.

RESULTS

The data showed that serum AGR2 level was significantly higher in the serum of PA patients (250.10±79.14ng/ml) than the patients with other sellar lesions (220.84±79.62ng/ml, P=0.017) and normal people (163.67±50.38ng/ml, P <0.001). Receiver operating characteristic (ROC) curve analysis was used. The detected area under the curve (AUC) was 0.835. The calculated optimal cut-off point for AGR2 level in serum samples was 158.63ng/ml (Youden index=0.564). The sensitivity was 91.4% and the specificity was 65.0%. Despite the variety of PA clinical features, the serum level of AGR2 are definite in PAs, although there may be a difference between male or female patients.

CONCLUSION

Our data suggests AGR2 as a potential biomarker for the diagnosis of PAs.

Expression of AGR2 in pituitary adenomas and its association with tumor aggressiveness

The aim of the present study was to study the expression of anterior gradient 2 (AGR2) to determine its clinical significance in pituitary adenoma (PA), and to evaluate the potential effect of AGR2 on the diagnosis, therapy or prognosis of PA. Immunohistochemistry was performed to detect the expression of AGR2 in 117 PA tissue samples. Western blotting was performed to confirm the expression profile of AGR2 in different subtypes of PAs. The data showed that in 117 different histological subtypes of PA, 51.3% exhibited AGR2-positive expression. Although AGR2 expression occurred more frequently in PAs secreting growth hormone (GH; 62.5%), adrenocorticotropic hormone (ACTH; 80.0%) and follicle-stimulating hormone (FSH; 75.0%),the positive expression rate of AGR2 showed no statistically significant differences between PA subtypes (P>0.05). The association between AGR2 expression and clinical parameters was analyzed using a χ² test, or Fisher's exact probability test when appropriate. The result showed that the aggressiveness of PA was significantly associated with AGR2 expression, and that in the majority of aggressive PAs, AGR2 was negative (P<0.001). In conclusion, the current study detected the expression of AGR2 in different subtypes of PAs for the first time. The data indicated that GH-, ACTH- and FSH-secreting PAs present marginally more frequently with AGR2 expression, howeverm the association was not significant (P>0.05). AGR2 may be a target for the study of PA aggressiveness, and a potential index for the diagnosis or prognosis of PAs.

AGR2 regulates IFITM3 expression to promote hepatocellular carcinoma cell proliferation

AIM: To investigate the effect of anterior gradient homolog 2 (AGR2) expression on the proliferation of hepatocellular carcinoma cells, and to explore the possible mechanism.

METHODS: The expression of AGR2 and interferon-induced transmembrane protein 3 (IFITM3) in hepatocellular carcinoma and adjacent tissues was detected by fluorescence quantitative PCR and Western blot. The expression of AGR2 mRNA and protein was examined by real-time fluorescence quantitative PCR and Western blot after transfection with pcDNA3.1-AGR2. The cellular growth ability was examined by CCK-8 assay, and the colony formation ability was detected by colony formation assay. Flow cytometry assay was used to determine the apoptosis index. The expression level of IFITM3 protein was examined by Western blot.

RESULTS: AGR2 and IFITM3 mRNA and protein expression in hepatocellular carcinoma tissues was significantly higher than that in the corresponding adjacent tissues. The pcDNA3.1-AGR2 was successfully constructed, and HepG2 cells with stable expression of AGR2 were established. The expression levels of AGR2 mRNA and protein in HepG2 cells after transfection with pcDNA3.1-AGR2 were higher than those in the negative control cells, and the cellular growth ability of HepG2 cells after transfection with pcDNA3.1-AGR2 was significantly increased. IFITM3 protein expression was also increased after transfection with pcDNA3.1-AGR2.

CONCLUSION: Raised AGR2 expression can increase the expression of IFITM3 and promote the proliferation of hepatocellular cells.

Anterior gradient 2 downregulation in a subset of pancreatic ductal adenocarcinoma is a prognostic factor indicative of epithelial-mesenchymal transition

Anterior gradient 2 (AGR2), a member of the protein disulfide isomerase family, has been implicated in various cancers including pancreatic ductal adenocarcinoma (PDAC) and is known to promote cancer progression. However, the prognostic value of AGR2 expression and the interaction with epithelial-mesenchymal transition (EMT) remain unclear. We investigated the clinical significance of AGR2 and EMT markers in PDAC patients by immunohistochemical analyses. Although AGR2 expression was not observed in normal pancreas, all pancreatic precursor neoplastic lesions were positive for AGR2, even at the earliest stages, including pancreatic intraepithelial neoplasia-1A, AGR2 expression was reduced in 27.7% (54/195 cases) of PDAC patients. AGR2 downregulation correlated with EMT markers (vimentin overexpression and reduced membranous E-cadherin expression), high Union for International Cancer Control stage (P<0.0001), high histological cellular grade (P<0.0001), and adverse outcome (P<0.0001). In vitro, targeted silencing of AGR2 in cancer cells using siRNA reduced cell proliferation, colony formation, cell invasiveness, and migration, but did not alter EMT markers. To confer a more aggressive phenotype and induce EMT in PDAC cells, we co-cultured PDAC cell lines with primary-cultured pancreatic stellate cells (PSCs) and found that AGR2 was downregulated in co-cultured PDAC cells compared with PDAC monocultures. Treatment with transforming growth factor beta-1 (TGF-β), secreted from PSCs, decreased AGR2 expression, whereas inhibition of TGF-β signaling using recombinant soluble human TGF-β receptor type II and TGF-β-neutralizing antibodies restored AGR2 expression. We conclude that AGR2 downregulation is a useful prognostic marker, induced by EMT, and that secreted TGF-β from PSCs may partially contribute to AGR2 downregulation in PDAC patients. AGR2 downregulation does not induce EMT or a more aggressive phenotype, but is a secondary effect of these processes in advanced PDAC.