AGR2 is a SMAD4-suppressible gene that modulates MUC1 levels and promotes the initiation and progression of pancreatic intraepithelial neoplasia

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.

Significance of TP53, CDKN2A, SMAD4 and KRAS in Pancreatic Cancer

The present review demonstrates the major tumor suppressor genes, including TP53, CDKN2A and SMAD4, associated with pancreatic cancer. Each gene's role, prevalence and impact on tumor development and progression are analyzed, focusing on the intricate molecular landscape of pancreatic cancer. In addition, this review underscores the prognostic significance of specific mutations, such as loss of TP53, and explores some potential targeted therapies tailored to these molecular signatures. The findings highlight the importance of genomic analyses for risk assessment, early detection and the design of personalized treatment approaches in pancreatic cancer. Overall, this review provides a comprehensive analysis of the molecular intricacies of pancreatic tumors, paving the way for more effective and tailored therapeutic interventions.

ESE1/AGR2 axis antagonizes TGF-β-induced epithelial-mesenchymal transition in low-grade pancreatic cancer

Epithelium-specific ETS transcription factor 1 (ESE1) has been implicated in epithelial homeostasis, inflammation, as well as tumorigenesis, and cancer progression. However, numerous studies have reported contradictory roles-as an oncogene or a tumor suppressor of ESE1 in different cancers, and its function in the development and progression of pancreatic ductal adenocarcinoma (PDAC) has remained largely unexplored. Herein, we report that ESE1 was found upregulated in primary PDAC compared to normal pancreatic tissue, but high expression of ESE1 correlated to better relapse-free survival in patients with PDAC. Interestingly, ESE1 was found to exhibit dual roles in regulation of malignant properties of PDAC cells in that its overexpression promoted cell proliferation, whereas its downregulation enhanced epithelial-mesenchymal transition (EMT) phenotype. In the context of TGF-β-induced EMT, ESE1 is markedly downregulated at post-transcriptional level, and reconstituted ESE1 expression partially reversed TGF-β-induced EMT marker expression. Furthermore, we identify AGR2 as a novel transcriptional target of ESE1 that participates in TGF-β-induced EMT in PDAC. Collectively, our findings reveal an ESE1/AGR2 axis that interacts with TGF-β signaling to modulate EMT phenotype in PDAC.

MUC1-C is a master regulator of MICA/B NKG2D ligand and exosome secretion in human cancer cells

BACKGROUND

The MUC1-C protein evolved in mammals to protect barrier tissues from loss of homeostasis; however, MUC1-C promotes oncogenesis in association with chronic inflammation. Aberrant expression of MUC1-C in cancers has been linked to depletion and dysfunction of T cells in the tumor microenvironment. In contrast, there is no known involvement of MUC1-C in the regulation of natural killer (NK) cell function.

METHODS

Targeting MUC1-C genetically and pharmacologically in cancer cells was performed to assess effects on intracellular and cell surface expression of the MHC class I chain-related polypeptide A (MICA) and MICB ligands. The MICA/B promoters were analyzed for H3K27 and DNA methylation. Shedding of MICA/B was determined by ELISA. MUC1-C interactions with ERp5 and RAB27A were assessed by coimmunoprecipitation and direct binding studies. Exosomes were isolated for analysis of secretion. Purified NK cells were assayed for killing of cancer cell targets.

RESULTS

Our studies demonstrate that MUC1-C represses expression of the MICA and MICB ligands that activate the NK group 2D receptor. We show that the inflammatory MUC1-C→NF-κB pathway drives enhancer of zeste homolog 2-mediated and DNMT-mediated methylation of the MICA and MICB promoter regions. Targeting MUC1-C genetically and pharmacologically with the GO-203 inhibitor induced intracellular and cell surface MICA/B expression but not MICA/B cleavage. Mechanistically, MUC1-C regulates the ERp5 thiol oxidoreductase that is necessary for MICA/B protease digestion and shedding. In addition, MUC1-C interacts with the RAB27A protein, which is required for exosome formation and secretion. As a result, targeting MUC1-C markedly inhibited secretion of exosomes expressing MICA/B. In concert with these results, we show that targeting MUC1-C promotes NK cell-mediated killing.

CONCLUSIONS

These findings uncover pleotropic mechanisms by which MUC1-C confers evasion of cancer cells to NK cell recognition and destruction.

AGR2: a secreted protein worthy of attention in diagnosis and treatment of breast cancer

AGR2 is a secreted protein widely existing in breast. In precancerous lesions, primary tumors and metastatic tumors, the expression of AGR2 is increased, which has aroused our interest. This review introduces the gene and protein structure of AGR2. Its endoplasmic reticulum retention sequence, protein disulfide isomerase active site and multiple protein binding sequences endow AGR2 with diverse functions inside and outside breast cancer cells. This review also enumerates the role of AGR2 in the progress and prognosis of breast cancer, and emphasizes that AGR2 can be a promising biomarker and a target for immunotherapy of breast cancer, providing new ideas for early diagnosis and treatment of breast cancer.

Expression of KAI1 and AGR2 in lung adenocarcinoma and their clinicopathological significance

OBJECTIVE

Anticancer 1 (KAI1, tumor metastasis suppressor gene) and Anterior gradient-2 (AGR2, considered a valuable prognostic factor for some cancers) are associated with metastasis and prognosis of various types of human cancers. Nevertheless, the relationship between KAI1 and AGR2 in lung adenocarcinoma (LUAD) remains unclear. In this research, we analyzed the correlations between KAI1 and AGR2 in LUAD, and explored their correlations with clinicopathological parameters and overall survival time (OS) in patients with LUAD.

METHODS

Immunohistochemical staining was used to detect KAI1 and AGR2 expression in 132 cases of LUAD samples. At the same time, all clinicopathological parameters and postoperative survival information were collected.

RESULTS

AGR2 positive rate was significantly increased and KAI1 positive rate was significantly decreased in LUAD and control tissues. KAI1 positive rates were negatively correlated with tumor stage, LNM stage and TNM stage, and KAI1 subgroup positive expression of OS was significantly higher than negative KAI1 subgroup. The positive rate of AGR2 was positively correlated with tumor grade, LNM stage and TNM stage, and negatively correlated with patients OS. Active expression of AGR2 and KAI1, tumor stage, and LNM stage in multivariate analyses may be independent prognostic factors for OS in LUAD patients.

CONCLUSION

KAI1 and AGR2 may be potential biomarkers for prognosis and metastasis, and they are also promising therapeutic targets for LUAD patients.

Knock-Out of the Five Lysyl-Oxidase Family Genes Enables Identification of Lysyl-Oxidase Pro-Enzyme Regulated Genes

The five lysyl-oxidase genes share similar enzymatic activities and contribute to tumor progression. We have knocked out the five lysyl-oxidase genes in MDA-MB-231 breast cancer cells using CRISPR/Cas9 in order to identify genes that are regulated by LOX but not by other lysyl-oxidases and in order to study such genes in more mechanistic detail in the future. Re-expression of the full-length cDNA encoding LOX identified four genes whose expression was downregulated in the knock-out cells and rescued following LOX re-expression but not re-expression of other lysyl-oxidases. These were the AGR2, STOX2, DNAJB11 and DNAJC3 genes. AGR2 and STOX2 were previously identified as promoters of tumor progression. In addition, we identified several genes that were not downregulated in the knock-out cells but were strongly upregulated following LOX or LOXL3 re-expression. Some of these, such as the DERL3 gene, also promote tumor progression. There was very little proteolytic processing of the re-expressed LOX pro-enzyme in the MDA-MB-231 cells, while in the HEK293 cells, the LOX pro-enzyme was efficiently cleaved. We introduced point mutations into the known BMP-1 and ADAMTS2/14 cleavage sites of LOX. The BMP-1 mutant was secreted but not cleaved, while the LOX double mutant dmutLOX was not cleaved or secreted. However, even in the presence of the irreversible LOX inhibitor β-aminoproprionitrile (BAPN), these point-mutated LOX variants induced the expression of these genes, suggesting that the LOX pro-enzyme has hitherto unrecognized biological functions.

Identification of AGR2 Gene-Specific Expression Patterns Associated with Epithelial-Mesenchymal Transition

The TGF-β signaling pathway is involved in numerous cellular processes, and its deregulation may result in cancer development. One of the key processes in tumor progression and metastasis is epithelial to mesenchymal transition (EMT), in which TGF-β signaling plays important roles. Recently, AGR2 was identified as a crucial component of the cellular machinery responsible for maintaining the epithelial phenotype, thereby interfering with the induction of mesenchymal phenotype cells by TGF-β effects in cancer. Here, we performed transcriptomic profiling of A549 lung cancer cells with CRISPR-Cas9 mediated AGR2 knockout with and without TGF-β treatment. We identified significant changes in transcripts associated with focal adhesion and eicosanoid production, in particular arachidonic acid metabolism. Changes in transcripts associated with the focal adhesion pathway were validated by RT-qPCR of COL4A1, COL4A2, FLNA, VAV3, VEGFA, and VINC mRNAs. In addition, immunofluorescence showed the formation of stress fibers and vinculin foci in cells without AGR2 and in response to TGF-β treatment, with synergistic effects observed. These findings imply that both AGR2 downregulation and TGF-β have a role in focal adhesion formation and cancer cell migration and invasion. Transcripts associated with arachidonic acid metabolism were downregulated after both AGR2 knockout and TGF-β treatment and were validated by RT-qPCR of GPX2, PTGS2, and PLA2G4A. Since PGE₂ is a product of arachidonic acid metabolism, its lowered concentration in media from AGR2-knockout cells was confirmed by ELISA. Together, our results demonstrate that AGR2 downregulation and TGF-β have an essential role in focal adhesion formation; moreover, we have identified AGR2 as an important component of the arachidonic acid metabolic pathway.

Dynamic transcriptome and LC-MS/MS analysis revealed the important roles of taurine and glutamine metabolism in response to environmental salinity changes in gills of rainbow trout (Oncorhynchus mykiss)

Recently, the frequent salinity fluctuation has become a growing threat to fishes. However, the dynamic patterns of gene expression in response to salinity changes remain largely unexplored. In the present study, 18 RNA-Seq datasets were generated from gills of rainbow trout at different salinities, including 0 ‰, 6 ‰, 12 ‰, 18 ‰, 24 ‰ and 30 ‰. Based on the strict thresholds, we have identified 63, 1411, 2096, 1031 and 1041 differentially expressed genes in gills of rainbow trout through pairwise comparisons. Additionally, weighted gene co-expression network analysis was performed to construct 18 independent modules with distinct expression patterns. Of them, green and tan modules were found to be tightly related to salinity changes, several hub genes of which are known as the important regulators in taurine and glutamine metabolism. To further investigate their potential roles in response to salinity changes, taurine, glutamine, and their metabolism-related glutamic acid and α-ketoglutaric acid were accurately quantitated using liquid chromatography-tandem mass spectrometry analysis. Results clearly showed that their concentrations were closely associated with salinity changes. These findings suggested that taurine and glutamine play important roles in response to salinity changes in gills of rainbow trout, providing new insights into the molecular mechanism of fishes in salinity adaptation.

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.

Physiological, morphological and transcriptomic responses of Tibetan naked carps (Gymnocypris przewalskii) to salinity variations

Gymnocypris przewalskii is a native cyprinid fish that dwells in the Lake Qinghai with salinity of 12-13‰. It migrates annually to the freshwater rivers for spawning, experiencing the significant changes in salinity. In the present study, we performed the physiological, morphological and transcriptomic analyses to understand the osmoregulation in G. przewalskii. The physiological assay showed that the osmotic pressure of G. przewalskii was almost isosmotic to the brackish lake water. The low salinity reduced its ionic concentrations and osmotic pressure. The plasticity of gill microstructure was linked to the salinity variations, including the presence of mucus and intact tight junctions in brackish water and the development of the mitochondria-rich cells and the loosened tight junctions in freshwater. RNA-seq analysis identified 1926 differentially expressed genes, including 710 and 1216 down- and up-regulated genes in freshwater, which were enriched in ion transport, cell-cell adhesion, and mucus secretion. Genes in ion uptake were activated in low salinity, and mucus pathways and tight junction showed the higher transcription in brackish water. The isosmoticity between the body fluid and the environment suggested G. przewalskii was in the metabolic-saving condition in the brackish water. The decreased salinity disrupted this balance, which activated the ion uptake in freshwater to maintain osmotic homeostasis. The gill remodeling was involved in this process through the development of the mitochondria-rich cells to enhance ion uptake. The current finding provided insights into the potential mechanisms of G. przewalskii to cope with salinity alteration.

Resistance to Gemcitabine in Pancreatic Ductal Adenocarcinoma: A Physiopathologic and Pharmacologic Review

Pancreatic ductal adenocarcinoma (PDAC) is a very aggressive tumor with a poor prognosis and inadequate response to treatment. Many factors contribute to this therapeutic failure: lack of symptoms until the tumor reaches an advanced stage, leading to late diagnosis; early lymphatic and hematic spread; advanced age of patients; important development of a pro-tumoral and hyperfibrotic stroma; high genetic and metabolic heterogeneity; poor vascular supply; a highly acidic matrix; extreme hypoxia; and early development of resistance to the available therapeutic options. In most cases, the disease is silent for a long time, andwhen it does become symptomatic, it is too late for ablative surgery; this is one of the major reasons explaining the short survival associated with the disease. Even when surgery is possible, relapsesare frequent, andthe causes of this devastating picture are the low efficacy ofand early resistance to all known chemotherapeutic treatments. Thus, it is imperative to analyze the roots of this resistance in order to improve the benefits of therapy. PDAC chemoresistance is the final product of different, but to some extent, interconnected factors. Surgery, being the most adequate treatment for pancreatic cancer and the only one that in a few selected cases can achieve longer survival, is only possible in less than 20% of patients. Thus, the treatment burden relies on chemotherapy in mostcases. While the FOLFIRINOX scheme has a slightly longer overall survival, it also produces many more adverse eventsso that gemcitabine is still considered the first choice for treatment, especially in combination with other compounds/agents. This review discusses the multiple causes of gemcitabine resistance in PDAC.

The unfolded protein response: An emerging therapeutic target for pancreatitis and pancreatic ductal adenocarcinoma

Pancreatitis is a debilitating disease involving inflammation and fibrosis of the exocrine pancreas. Recurrent or chronic forms of pancreatitis are a significant risk factor for pancreatic ductal adenocarcinoma. While genetic factors have been identified for both pathologies, environmental stresses play a large role in their etiology. All cells have adapted mechanisms to handle acute environmental stress that alters energy demands. A common pathway involved in the stress response involves endoplasmic reticulum stress and the unfolded protein response (UPR). While rapidly activated by many external stressors, in the pancreas the UPR plays a fundamental biological role, likely due to the high protein demands in acinar cells. Despite this, increased UPR activity is observed in response to acute injury or following exposure to risk factors associated with pancreatitis and pancreatic cancer. Studies in animal and cell cultures models show the importance of affecting the UPR in the context of both diseases, and inhibitors have been developed for several specific mediators of the UPR. Given the importance of the UPR to normal acinar cell function, efforts to affect the UPR in the context of disease must be able to specifically target pathology vs. physiology. In this review, we highlight the importance of the UPR to normal and pathological conditions of the exocrine pancreas. We discuss recent studies suggesting the UPR may be involved in the initiation and progression of pancreatitis and PDAC, as well as contributing to chemoresistance that occurs in pancreatic cancer. Finally, we discuss the potential of targeting the UPR for treatment.

From development to cancer - an ever-increasing role of AGR2

Anterior gradient 2, AGR2, is a small, 20 kDa protein that plays a vital role in oxidative protein folding in the endoplasmic reticulum. AGR2 is involved in several signal transduction pathways that are essential for cell survival. It was initially discovered in the African clawed frog, Xenopus laevis, where it plays an important function in embryonic development. Akin to several other developmental genes, it is also frequently deregulated in cancer, where it plays a decisive role in tumor initiation, progression and metastasis. In this review, we have summarized currently known AGR2 functions, its expression and function in embryonic and cancer development, as well as its potential as a candidate tumor biomarker and promising new target for cancer immunotherapy.

Intracellular AGR2 transduces PGE2 stimuli to promote epithelial-mesenchymal transition and metastasis of colorectal cancer

Human anterior gradient homolog 2 (AGR2) reportedly acts as an oncogene in multiple types of cancers. As a secreted protein, the oncogenic roles of extracellular AGR2 have been the focus of the increasing number of studies. In contrast, the oncological functions of intracellular AGR2 (iAGR2) remain elusive. Here, we report that intracellular AGR2 (iAGR2) is sufficient to promote CRC metastasis. iAGR2 binds to KDEL receptors (KDELRs) via its KTEL motif to activate downstream Gs-PKA signaling. Activated PKA upregulates the expression of NF-κB subunit c-Rel (REL) and acetylates histone H3 at lysine 9 (H3K9ac) to promote the transcription of SNAIL and SLUG. AGR2 can be upregulated by prostaglandin E2 (PGE2) via EP4-PI3K-AKT pathway and is indispensable for PGE2-induced CRC metastasis. AGR2 knockdown enhances therapeutic effects of a COX-2 inhibitor, celecoxib, in CRC metastasis. Collectively, our study reveals a promoting role and molecular mechanisms of iAGR2 in CRC metastasis and uncovers a new tumor microenvironment signal regulating AGR2 expression, which may provide new targets for treating metastatic CRC.

Effects of ER-resident and secreted AGR2 on cell proliferation, migration, invasion, and survival in PANC-1 pancreatic cancer cells

Background

Anterior gradient-2 (AGR2) is a proto-oncogene involved in tumorigenesis and cancer progression. AGR2, predominantly localized in the endoplasmic reticulum (ER), is also a secreted protein detected in the extracellular compartment in multiple cancers. However, the biological functions of intracellular and extracellular AGR2 remain to be elucidated.

Methods

Based on the biochemical structure of AGR2 protein, PANC-1 pancreatic cancer cells stably expressing ER-resident or secreted AGR2 were generated by a lentivirus-mediated stable overexpression system. The capacities of cell proliferation, migration, invasion and survival were assessed in PANC-1 stable cells. Moreover, EGFR expression and activation were determined to explore the possible mechanism of AGR2 roles in pancreatic cancer tumorigenesis.

Results

It was discovered that secreted AGR2, but not ER-resident AGR2, promotes cell proliferation, migration and invasion of PANC-1 cells. Moreover, the data indicated that both the ER-resident and the secreted AGR2 enhance the survival capacity of PANC-1 cells after tunicamycin-induced ER stress and gemcitabine treatment. However, EGFR expression and activation were not found to be involved in AGR2-dependent oncogenic phenotypes in PANC-1 cells.

Conclusions

Secreted AGR2 is predominantly involved in cell proliferation, migration and invasion in PANC-1 pancreatic cancer cells. Both secreted and ER-resident AGR2 contribute to the survival of PANC-1 cells under the challenging conditions. These findings provide insight into how different localizations of AGR2 have contributed to pancreatic cancer growth, metastasis, and drug sensitivity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07743-y.

Anterior gradient 2 is a novel pro-tumor factor in pancreatic cancer under NF-κB subunit RelA trans-regulation that can be suppressed by eugenic acid

This study aimed to examine eugenic acid (EA) as an alternative therapeutic approach against pancreatic cancer. The pancreatic cancer xenograft mouse model was employed to determine the impacts of treatment with EA on the growth of tumors. Expressions of NF-κB subunit RelA as well as Anterior gradient 2 (AGR2) were quantified in pancreatic cells treated with EA. Chromatin immunoprecipitation and luciferase report assay were performed to examine the regulation of AGR2 by RelA. The function of AGR2 as a downstream effector EA treatment was further assessed through overexpression of AGR2 in pancreatic cells. EA suppressed the growth of xenograft pancreatic tumor, and promoted the overall survival of animals with xenograft tumors. Furthermore, EA downregulated the expression of AGR2 in pancreatic cancer cells via the RelA binding site. Ectopic AGR2 overexpression attenuated the EA-elicited inhibition on the growth of xenograft pancreatic tumor, and negated the EA-induced enhancement of mouse survival. EA ameliorates pancreatic cancer through suppression of AGR2 expression, and future studies in clinical settings are needed to further assess the anti-cancer efficacy of EA.

Cross-talk between myeloid-derived suppressor cells and Mucin1 in breast cancer vaccination: On the verge of a breakthrough

Although breast cancer is one of the leading troublesome cancers, the available therapeutic options have not fulfilled the desired outcomes. Immune-based therapy has gained special attention for breast cancer treatment. Although this approach is highly tolerable, its low response rate has rendered it as an undesirable approach. This review aims to describe the essential oncogenic pathways involved in breast cancer, elucidate the immunosuppression and oncogenic effect of Mucin1, and introduce myeloid-derived suppressor cells, which are the main culprits of anti-tumoral immune response attenuation. The various auto-inductive loops between Mucin1 and myeloid-derived suppressor cells are focal in the suppression of anti-tumoral immune responses in patients with breast cancer. These cross-talks between the Mucin1 and myeloid-derived suppressor cells can be the underlying causes of immunotherapy's impotence for patients with breast cancer. This approach can pave the road for the development of a potent vaccine for patients with breast cancer and is translated into clinical settings.

AGR2-induced glucose metabolism facilitated the progression of endometrial carcinoma via enhancing the MUC1/HIF-1α pathway

Anterior gradient 2 (AGR2) was proved to modulate cancer progression. However, the role of AGR2 on endometrial cancer was not established. Here, we investigated the effects of AGR2 expression on endometrial cancer and explored the regulation mechanism. In the study, we found that AGR2 was overexpressed in tumor tissues of 30 endometrial cancer patients. A high level of AGR2 promoted endometrial cancer cells proliferation, migration and invasion. AGR2 induced the expression of lactate dehydrogenase A (LDHA), phosphoglycerate kinase 1 (PGK1), kallikrein 2 (HK2), and enolase 1-α (ENO1), glucose uptake and lactate production. AGR2 could bind to MUC1 and induce MUC1 and hypoxia-inducible factor 1α (HIF-1α). The inhibition effects of AGR2 knockdown on cells proliferation, migration and invasion ability were abolished by the overexpression of MUC1. Besides, the overexpression of MUC1 also reversed the inhibition effects of AGR2 knockdown on the expression of LDHA, HK2, PGK1 and ENO1, glucose uptake and lactate production. AGR2 knockdown inhibited tumor growth, the levels of Ki-67, MUC1, HIF-1α and glycolysis. In conclusion, AGR2 was overexpressed in endometrial cancer and AGR2-induced glucose metabolism facilitated the progression of endometrial carcinoma via the MUC1/HIF-1α pathway. AGR2 may be an effective therapeutic target for endometrial carcinoma.

Pseudostellaria heterophylla Extract Polysaccharide H-1-2 Suppresses Pancreatic Cancer by Inhibiting Hypoxia-Induced AG2

We aimed to examine the therapeutic potential of polysaccharide H-1-2, a bioactive component of Pseudostellaria heterophylla, against pancreatic cancer, as well as to demonstrate the underlying molecular mechanisms. Invasion and migration of pancreatic cells treated with H-1-2 were evaluated. A xenograft tumor mouse model was established to assess the effect of H-1-2 on tumor growth. Expression levels of hypoxic inducible factor-1α (HIF1α) and anterior gradient 2 (AGR2) were measured in pancreatic cells after H-1-2 treatment. Luciferase report and chromatin immunoprecipitation assays were conducted to investigate HIF1α regulation on AGR2. AGR2 expression was re-introduced into pancreatic cells to assess the role of AGR2 as a downstream effector of hypoxia after H-1-2 treatment. H-1-2 inhibited invasion and migration of pancreatic cancer cells, repressed xenograft pancreatic tumor growth, and increased survival of mice. H-1-2 repressed AGR2 expression in pancreatic cancer cells through the hypoxia response element (HRE) in its promoter region. Ectopic AGR2 expression partially negated the H-1-2 inhibitory effect on invasion and migration of pancreatic cells and on xenograft pancreatic tumors growth, and it also compromised the H-1-2 promotional effect on survival of mice. We conclude that H-1-2 suppresses pancreatic cancer by inhibiting hypoxia-induced AGR2 expression, supporting further investigation into its efficacy against pancreatic cancer in clinical settings.

MUC1 oncoprotein mitigates ER stress via CDA-mediated reprogramming of pyrimidine metabolism

The Mucin 1 (MUC1) protein is overexpressed in various cancers and mediates chemotherapy resistance. However, the mechanism is not fully understood. Given that most chemotherapeutic drugs disrupt ER homeostasis as part of their toxicity, and MUC1 expression is regulated by proteins involved in ER homeostasis, we investigated the link between MUC1 and ER homeostasis. MUC1 knockdown in pancreatic cancer cells enhanced unfolded protein response (UPR) signaling and cell death upon ER stress induction. Transcriptomic analysis revealed alterations in the pyrimidine metabolic pathway and cytidine deaminase (CDA). ChIP and CDA activity assays showed that MUC1 occupied CDA gene promoter upon ER stress induction correlating with increased CDA expression and activity in MUC1-expressing cells as compared to MUC1 knockdown cells. Inhibition of either the CDA or pyrimidine metabolic pathway diminished survival in MUC1-expressing cancer cells upon ER stress induction. Metabolomic analysis demonstrated that MUC1-mediated CDA activity corresponded to deoxycytidine to deoxyuridine metabolic reprogramming upon ER stress induction. The resulting increase in deoxyuridine mitigated ER stress-induced cytotoxicity. Additionally, given 1) the established roles of MUC1 in protecting cells against reactive oxygen species (ROS) insults, 2) ER stress-generated ROS further promote ER stress and 3) the emerging anti-oxidant property of deoxyuridine, we further investigated if MUC1 regulated ER stress by a deoxyuridine-mediated modulation of ROS levels. We observed that deoxyuridine could abrogate ROS-induced ER stress to promote cancer cell survival. Taken together, our findings demonstrate a novel MUC1-CDA axis of the adaptive UPR that provides survival advantage upon ER stress induction.

The anterior gradient-2 interactome

The anterior gradient-2 (AGR2) is an endoplasmic reticulum (ER)-resident protein belonging to the protein disulfide isomerase family that mediates the formation of disulfide bonds and assists the protein quality control in the ER. In addition to its role in proteostasis, extracellular AGR2 is responsible for various cellular effects in many types of cancer, including cell proliferation, survival, and metastasis. Various OMICs approaches have been used to identify AGR2 binding partners and to investigate the functions of AGR2 in the ER and outside the cell. Emerging data showed that AGR2 exists not only as monomer, but it can also form homodimeric structure and thus interact with different partners, yielding different biological outcomes. In this review, we summarize the AGR2 “interactome” and discuss the pathological and physiological role of such AGR2 interactions.

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.

Extracellular AGR3 regulates breast cancer cells migration via Src signaling

Human anterior gradient proteins AGR2 and AGR3 are overexpressed in a variety of adenocarcinomas and are often secreted in cancer patients' specimens, which suggests a role for AGR proteins in intra and extracellular compartments. Although these proteins exhibit high sequence homology, AGR2 is predominantly described as a pro-oncogene and a potential prognostic biomarker. However, little is known about the function of AGR3. Therefore, the aim of the present study was to investigate the role of AGR3 in breast cancer. The results demonstrated that breast cancer cells secrete AGR3. Furthermore, it was revealed that extracellular AGR3 (eAGR3) regulates tumor cell adhesion and migration. The current study indicated that the pharmacological and genetic perturbation of Src kinase signaling, through treatment with Dasatinib (protein kinase inhibitor) or investigating cells that express a dominant-negative form of Src, significantly abrogated eAGR3-mediated breast cancer cell migration. Therefore, the results indicated that eAGR3 may control tumor cell migration via activation of Src kinases. The results of the present study indicated that eAGR3 may serve as a microenvironmental signaling molecule in tumor-associated processes.

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.

Associations of MACC1, AGR2, and KAI1 expression with the metastasis and prognosis in head and neck squamous cell carcinoma

BACKGROUND

Metastasis-associated in colon cancer-1 (MACC1, was firstly found in colon cancer and associated metastasis and prognosis in various cancers), anterior gradient 2 (AGR2, was considered as a valuable prognostic factor for some cancers), and Kangai 1 (KAI1, was a tumor metastasis suppressor gene) are all related to metastasis and prognosis of many cancers. However, the associations of MACC1, AGR2, and KAI1 in head and neck squamous cell carcinoma (HNSCC) are still unclear. In this study, we analyzed associations among MACC1, AGR2, and KAI1 in HNSCC, and their respective associations with clinicopathological parameters and overall survival (OS) in HNSCC.

METHODS

Positive expression of MACC1, AGR2, and KAI1 in 106 whole HNSCC tissue samples was detected by immunohistochemical staining. Patient's clinical data and demographics were both collected.

RESULTS

Positive rates of MACC1 and AGR2 were significantly higher, and positive rate of KAI1 was significantly lower, in HNSCC and than those in control tissues. Positive rates of MACC1 and AGR2 were positively correlated with grades of tumor, TNM stages, and lymph node metastasis (LNM) stages, and negatively with patients OS; positive rate of KAI1 was negatively associated with grades of tumor, TNM stages, and LNM stages, and the positive expression of KAI1 subgroup had significantly longer OS than did the negative KAI1 subgroup. In multivariate analysis, positive expression MACC1, AGR2, and KAI1, and tumor stages, as well as LNM stages were potential to be independent prognostic factors for OS in patients with HNSCC.

CONCLUSIONS

MACC1, AGR2, and KAI1 may represent potential metastatic and prognostic biomarkers, as well as promising therapeutic targets for HNSCC.

MicroRNA-1291 targets the FOXA2-AGR2 pathway to suppress pancreatic cancer cell proliferation and tumorigenesis

Pancreatic cancer is the fourth leading cause of cancer death in the United States. Better understanding of pancreatic cancer biology may help identify new oncotargets towards more effective therapies. This study investigated the mechanistic actions of microRNA-1291 (miR-1291) in the suppression of pancreatic tumorigenesis. Our data showed that miR-1291 was downregulated in a set of clinical pancreatic carcinoma specimens and human pancreatic cancer cell lines. Restoration of miR-1291 expression inhibited pancreatic cancer cell proliferation, which was associated with cell cycle arrest and enhanced apoptosis. Furthermore, miR-1291 sharply suppressed the tumorigenicity of PANC-1 cells in mouse models. A proteomic profiling study revealed 32 proteins altered over 2-fold in miR-1291-expressing PANC-1 cells that could be assembled into multiple critical pathways for cancer. Among them anterior gradient 2 (AGR2) was reduced to the greatest degree. Through computational and experimental studies we further identified that forkhead box protein A2 (FOXA2), a transcription factor governing AGR2 expression, was a direct target of miR-1291. These results connect miR-1291 to the FOXA2-AGR2 regulatory pathway in the suppression of pancreatic cancer cell proliferation and tumorigenesis, providing new insight into the development of miRNA-based therapy to combat pancreatic cancer.

SMAD4-independent activation of TGF-β signaling by MUC1 in a human pancreatic cancer cell line

Pancreatic Ductal Adenocarcinoma (PDA) has a mortality rate that nearly matches its incidence rate. Transforming Growth Factor Beta (TGF-β) is a cytokine with a dual role in tumor development switching from a tumor suppressor to a tumor promoter. There is limited knowledge of how TGF-β function switches during tumorigenesis. Mucin 1 (MUC1) is an aberrantly glycosylated, membrane-bound, glycoprotein that is overexpressed in >80% of PDA cases and is associated with poor prognosis. In PDA, MUC1 promotes tumor progression and metastasis via signaling through its cytoplasmic tail (MUC1-CT) and interacting with other oncogenic signaling molecules. We hypothesize that high levels of MUC1 in PDA may be partly responsible for the TGF-β functional switch during oncogenesis. We report that overexpression of MUC1 in BxPC3 human PDA cells (BxPC3.MUC1) enhances the induction of epithelial to mesenchymal transition leading to increased invasiveness in response to exogenous TGF-β1. Simultaneously, these cells resist TGF-β induced apoptosis by downregulating levels of cleaved caspases. We show that mutating the tyrosines in MUC1-CT to phenylalanine reverses the TGF-β induced invasiveness. This suggests that the tyrosine residues in MUC1-CT are required for TGF-β induced invasion. Some of these tyrosines are phosphorylated by the tyrosine kinase c-Src. Thus, treatment of BxPC3.MUC1 cells with a c-Src inhibitor (PP2) significantly reduces TGF-β induced invasiveness. Similar observations were confirmed in the Chinese hamster ovarian (CHO) cell line. Data strongly suggests that MUC1 may regulate TGF-β function in PDA cells and thus have potential clinical relevance in the use of TGF-β inhibitors in clinical trials.

miR-342-3p suppresses cell proliferation and migration by targeting AGR2 in non-small cell lung cancer

AGR2 is a well-studied secreted protein that is involved in multiple biological processes including cell proliferation and migration. The mechanism by which AGR2 increases the growth and migration of non-small cell lung cancer cells (NSCLC) is still unknown. In this study, we report that AGR2 is directly targeted by miR-342-3p. Functional studies suggest that overexpression of miR-342-3p inhibits the proliferation and migration of non-small cell lung cancer cells. Overexpression of AGR2 counteracts the phenotypes induced by miR-342-3p. Moreover, AGR2 expression is up-regulated and negatively correlated with miR-342-3p levels in NSCLC cells and tissues. A meta-analysis of survival data indicates that NSCLC patients with high levels of AGR2 in their tumors have a worse prognosis. Collectively, the identification of miR-342-3p and AGR2 might facilitate the development of biomarkers and therapeutic targets for this devastating disease.

T cell optimization for the treatment of pancreatic cancer

INTRODUCTION

Pancreatic cancer remains a deadly disease despite advances in surgery, chemotherapy, and radiation therapy. Treatment failure is likely due to intense chemoresistance and immunosuppression. Therefore, new treatment paradigms are urgently needed. Immunotherapy, particularly adoptive T cell transfer, is a highly-personalized therapy that involves the isolation and ex vivo expansion of tumor-specific T cells before administration to cancer-bearing hosts. Areas covered: This review summarizes different strategies of adoptive T cell therapy and their application in pancreatic cancer treatment. It also highlights recent advances and gives discussion on the future directions in T cell-based immunotherapy for pancreatic cancer. Expert opinion: Pancreatic ductal adenocarcinoma is extremely challenging to treat, in part, due to intense desmoplastic reaction and immunosuppression. The recent progress in cancer immunotherapy triggers a hope to use immunotherapeutic modality to treat pancreatic cancer. Immunotherapy is generally well tolerated, and has the potential to function as a monotherapy or in synergistic combination with conventional chemotherapy. We must make efforts to optimize the immunotherapeutic regimen and to select patients to treat based on their biological profile. To accomplish this goal, an intense collaboration is needed to bridge between bench and bedside.

Suppression of AGR2 in a TGF-β-induced Smad regulatory pathway mediates epithelial-mesenchymal transition

Background

During cancer progression, epithelial cancer cells can be reprogrammed into mesenchymal-like cells with increased migratory potential through the process of epithelial-mesenchymal transition (EMT), representing an essential step of tumor progression towards metastatic state. AGR2 protein was shown to regulate several cancer-associated processes including cellular proliferation, survival and drug resistance.

Methods

The expression of AGR2 was analyzed in cancer cell lines exposed to TGF-β alone or to combined treatment with TGF-β and the Erk1/2 inhibitor PD98059 or the TGF-β receptor specific inhibitor SB431542. The impact of AGR2 silencing by specific siRNAs or CRISPR/Cas9 technology on EMT was investigated by western blot analysis, quantitative PCR, immunofluorescence analysis, real-time invasion assay and adhesion assay.

Results

Induction of EMT was associated with decreased AGR2 along with changes in cellular morphology, actin reorganization, inhibition of E-cadherin and induction of the mesenchymal markers vimentin and N-cadherin in various cancer cell lines. Conversely, induction of AGR2 caused reversion of the mesenchymal phenotype back to the epithelial phenotype and re-acquisition of epithelial markers. Activated Smad and Erk signaling cascades were identified as mutually complementary pathways responsible for TGF-β-mediated inhibition of AGR2.

Conclusion

Taken together our results highlight a crucial role for AGR2 in maintaining the epithelial phenotype by preventing the activation of key factors involved in the process of EMT.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3537-5) contains supplementary material, which is available to authorized users.

ER stress protein AGR2 precedes and is involved in the regulation of pancreatic cancer initiation

The mechanisms of initiation of pancreatic ductal adenocarcinoma (PDAC) are still largely unknown. In the present study, we analysed the role of anterior gradient-2 (AGR2) in the earliest stages of pancreatic neoplasia. Immunohistochemical analysis of chronic pancreatitis (CP) and peritumoral areas in PDAC tissues showed that AGR2 was present in tubular complexes (TC) and early pancreatic intraepithelial neoplasia (PanINs). Moreover, AGR2 was also found in discrete subpopulations of non-transformed cells neighbouring these pre-neoplastic lesions. In primary cells derived from human patient-derived xenograft (PDX) model, flow-cytometry revealed that AGR2 was overexpressed in pancreatic cancer stem cells (CSC) compared with non-stem cancer cells. In LSL-Kras^G12D;Pdx1-Cre (KC) mouse model Agr2 induction preceded the formation of pre-neoplastic lesions and their development was largely inhibited by Agr2 deletion in engineered LSL-Kras^G12D;Pdx1-Cre; Agr2^−/− mice. In vitro, AGR2 expression was stimulated by tunicamycin-induced endoplasmic reticulum (ER) stress in both KRAS wild-type normal pancreas cells, as well as in KRAS mutated pancreatic cancer cells and was essential for ER homoeostasis. The unfolded protein response proteins GRP78, ATF6 and XBP1s were found expressed in CP and PDAC peritumoral tissues, but in contrast to AGR2, their expression was switched off during TC and PanIN formation. Real-time PCR and ELISA analyses showed that ER stress induced a pro-inflammatory phenotype in pancreatic normal, cancer and stellate cells. Moreover, AGR2 expression was inducible by paracrine transfer of ER stress and pro-inflammation between different pancreatic cell types. Our findings demonstrate that AGR2 induced in ER-stressed and inflammatory pre-neoplastic pancreas is a potential marker of cancer progenitor cells with an important functional role in PDAC initiation.

Binding of anterior gradient 2 and estrogen receptor-α: Dual critical roles in enhancing fulvestrant resistance and IGF-1-induced tumorigenesis of breast cancer

Anterior gradient 2 (AGR2), an essential cancer biomarker, has been widely reported to be associated with estrogen receptor (ER) positive breast cancer development. Here, we uncovered the role of cytoplasmic and exogenous AGR2, through interaction with ER-α, in enhancing fulvestrant resistance and IGF-1-induced carcinogenesis respectively. Our present study revealed that the endogenous AGR2 level positively correlates with fulvestrant resistance in MCF-7 and T47D cells. AGR2-knockdown in MCF-7 cells strongly enhances the fulvestrant-induced G1 phase arrest and accelerates the fulvestrant-induced ER-α degradation. Furthermore, intracellular AGR2 exhibits a functional interaction with ER-α. On the other hand, extracellular AGR2 remarkably promotes the IGF-1-induced cell proliferation, migration, cell cycle progression and epithelial-mesenchymal transition. Extracellular AGR2 also enhances IGF-1 downstream signaling. We also showed that ER-α specifically interacts with both extracellular AGR2 and IGF-1 receptor as a potential intermediator. Finally, we revealed that the adjuvant therapy of AGR2 monoclonal antibody enhances the inhibitory effects of fulvestrant and linsitinib toward breast cancer development. Our findings, for the first time, point out the different functions of intra- and extra-cellular AGR2, providing new insights into the development of anti-tumor therapies targeting AGR2.

Anterior gradient protein 2 expression in high grade head and neck squamous cell carcinoma correlated with cancer stem cell and epithelial mesenchymal transition

Anterior gradient protein 2 (AGR2) is a novel biomarker with potential oncogenic role. We sought to investigate the diagnostic and prognostic role of AGR2 on head and neck squamous cell carcinoma (HNSCC) with an emphasis on its correlation of cancer stemloid cells (CSC) and epithelial mesenchymal transition (EMT). We found that AGR2 protein levels were higher in HNSCC than in normal oral mucosa. High levels of AGR2 were associated with the T category, pathological grade and lymph node metastasis of HNSCC. Expression of AGR2 increased in recurring HNSCC after radiotherapy and in post cisplatin-based chemotherapeutic tissues. In HNSCC cell lines, knock-down of AGR2 induced apoptosis, reduced sphere formation, and down-regulated Survivin, Cyclin D1, Bcl2, Bcl2l1, Slug, Snail, Nanog and Oct4. In addition, over-expressed AGR2 in transgenic mice with spontaneous HNSCC was associated with lost function of Tgfbr1 and/or lost function of Pten. In vitro knockdown TGFBR1 in HNSCC cell lines increased AGR2 expression. These results suggest that AGR2 is involved in EMT and self-renewal of CSC and may present a potential therapeutic target (oncotarget) for HNSCC.

Quantitative Secretomic Analysis Identifies Extracellular Protein Factors That Modulate the Metastatic Phenotype of Non-Small Cell Lung Cancer

Lung cancer is the leading cause of cancer-related deaths for men and women in the United States, with non-small cell lung cancer (NSCLC) representing 85% of all diagnoses. Late stage detection, metastatic disease and lack of actionable biomarkers contribute to the high mortality rate. Proteins in the extracellular space are known to be critically involved in regulating every stage of the pathogenesis of lung cancer. To investigate the mechanism by which secreted proteins contribute to the pathogenesis of NSCLC, we performed quantitative secretomic analysis of two isogenic NSCLC cell lines (NCI-H1993 and NCI-H2073) and an immortalized human bronchial epithelial cell line (HBEC3-KT) as control. H1993 was derived from a chemo-naïve metastatic tumor, while H2073 was derived from the primary tumor after etoposide/cisplatin therapy. From the conditioned media of these three cell lines, we identified and quantified 2713 proteins, including a series of proteins involved in regulating inflammatory response, programmed cell death and cell motion. Gene Ontology (GO) analysis indicates that a number of proteins overexpressed in H1993 media are involved in biological processes related to cancer metastasis, including cell motion, cell-cell adhesion and cell migration. RNA interference (RNAi)-mediated knock down of a number of these proteins, including SULT2B1, CEACAM5, SPRR3, AGR2, S100P, and S100A14, leads to dramatically reduced migration of these cells. In addition, meta-analysis of survival data indicates NSCLC patients whose tumors express higher levels of several of these secreted proteins, including SULT2B1, CEACAM5, SPRR3, S100P, and S100A14, have a worse prognosis. Collectively, our results provide a potential molecular link between deregulated secretome and NSCLC cell migration/metastasis. In addition, the identification of these aberrantly secreted proteins might facilitate the development of biomarkers for early detection of this devastating disease.

Distal bile duct carcinomas and pancreatic ductal adenocarcinomas: postulating a common tumor entity

The set definition of distal cholangiocarcinomas and adenocarcinomas of the pancreatic head is challenged by their close anatomical relation, similar growth pattern, and corresponding therapeutic outcome. They show a mutual development during embryologic organ formation and share phenotypic characteristics. This review will highlight the similarities with regard to the common origin of their primary organs, histopathological similarities, and modern clinical management. Thus, we propose to subsume those entities under a common superfamily.

MUC1 (CD227): a multi-tasked molecule

Mucin 1 (MUC1 [CD227]) is a high-molecular weight (>400 kDa), type I membrane-tethered glycoprotein that is expressed on epithelial cells and extends far above the glycocalyx. MUC1 is overexpressed and aberrantly glycosylated in adenocarcinomas and in hematological malignancies. As a result, MUC1 has been a target for tumor immunotherapeutic studies in mice and in humans. MUC1 has been shown to have anti-adhesive and immunosuppressive properties, protects against infections, and is involved in the oncogenic process as well as in cell signaling. In addition, MUC1 plays a key role in the reproductive tract, in the immune system (affecting dendritic cells, monocytes, T cells, and B cells), and in chronic inflammatory diseases. Evidence for all of these roles for MUC1 is discussed herein and demonstrates that MUC1 is truly a multitasked molecule.

Integrated stress response is critical for gemcitabine resistance in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with marked chemoresistance and a 5-year survival rate of 7%. The integrated stress response (ISR) is a cytoprotective pathway initiated in response to exposure to various environmental stimuli. We used pancreatic cancer cells (PCCs) that are highly resistant to gemcitabine (Gem) and an orthotopic mouse model to investigate the role of the ISR in Gem chemoresistance. Gem induced eIF2 phosphorylation and downstream transcription factors ATF4 and CHOP in PCCs, and these effects occurred in an eIF2α-S51 phosphorylation-dependent manner as determined using PANC-1 cells, and wild type and S51 mutant mouse embryo fibroblasts. Blocking the ISR pathway in PCCs with the ISR inhibitor ISRIB or siRNA-mediated depletion of ATF4 resulted in enhanced Gem-mediated apoptosis. Polyribosomal profiling revealed that Gem caused repression of global translation and this effect was reversed by ISRIB or by expressing GADD34 to facilitate eIF2 dephosphorylation. Moreover, Gem promoted preferential mRNA translation as determined in a TK-ATF4 5′UTR-Luciferase reporter assay, and this effect was also reversed by ISRIB. RNA-seq analysis revealed that Gem upregulated eIF2 and Nrf2 pathways, and that ISRIB significantly inhibited these pathways. Gem also induced the expression of the antiapoptotic factors Nupr1, BEX2, and Bcl2a1, whereas ISRIB reduced their expression. In an orthotopic tumor model using PANC-1 cells, ISRIB facilitated Gem-mediated increases in PARP cleavage, which occurred in conjunction with decreased tumor size. These findings indicate that Gem chemoresistance is enhanced by activating multiple ISR-dependent pathways, including eIF2, Nrf2, Nupr1, BEX2, and Bcl2A1. It is suggested that targeting the ISR pathway may be an efficient mechanism for enhancing therapeutic responsiveness to Gem in PDAC.

The metastasis-inducing protein AGR2 is O-glycosylated upon secretion from mammary epithelial cells

AGR2 is overexpressed in multiple cancers, particularly those arising from breast and prostate tissues, and higher levels of AGR2 are associated with earlier patient death. Although AGR2 is normally resident within the endoplasmic reticulum, the protein has been found in the extracellular space in several model systems. However, it has never been expressly demonstrated that this extracellular form of the protein is secreted and does not just accumulate in the extracellular space as a result of cell lysis. We show in this paper that AGR2 protein is secreted by both human and rat mammary epithelial cells in culture. Furthermore, this secreted form of AGR2 becomes O-glycosylated, with no detectable presence of N-glycosylation. Importantly, this post-translationally modified AGR2 is only detected in the conditioned medium from non-leaky cells, suggesting that membrane integrity must be maintained to allow AGR2 glycosylation. The results suggest a possible role for O-glycosylation in modulating the extracellular functions of AGR2.

A proteomic profiling of laser-microdissected lung adenocarcinoma cells of early lepidic-types

Background

In the new pathologic classification of lung adenocarcinoma proposed by IASLC/ATS/ERS in 2011, lepidic type adenocarcinomas are constituted by three subtypes; adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA) and lepidic predominant invasive adenocarcinoma (LPIA). Although these subtypes are speculated to show sequential progression from preinvasive lesion to invasive lung cancer, changes of protein expressions during these processes have not been fully studied yet. This study aims to glimpse a proteomic view of the early lepidic type lung adenocarcinomas.

Methods

A total of nine formalin-fixed and paraffin-embedded (FFPE) lepidic type lung adenocarcinoma tissues were selected from our archives, three tissues each in AIS, MIA and LPIA. The tumor and peripheral non-tumor cells in these FFPE tissues were collected with laser microdissection (LMD). Using liquid chromatography-tandem mass spectrometry (MS/MS), protein compositions were compared with respect to the peptide separation profiles among tumors collected from three types of tissues, AIS, MIA and LPIA. Proteins identified were semi-quantified by spectral counting-based or identification-based approach, and statistical evaluation was performed by pairwise G-tests.

Results

A total of 840 proteins were identified. Spectral counting-based semi-quantitative comparisons of all identified proteins through AIS to LPIA have revealed that the protein expression profile of LPIA was significantly differentiated from other subtypes. 70 proteins including HPX, CTTN, CDH1, EGFR, MUC1 were found as LPIA-type marker candidates, 15 protein candidates for MIA-type marker included CRABP2, LMO7, and RNPEP, and 26 protein candidates for AIS-type marker included LTA4H and SOD2. The STRING gene set enrichment resulted from the protein-protein interaction (PPI) network analysis suggested that AIS was rather associated with pathways of focal adhesion, adherens junction, tight junction, that MIA had a strong association predominantly with pathways of proteoglycans in cancer and with PI3K-Akt. In contrast, LPIA was associated broadly with numerous tumor-progression pathways including ErbB, Ras, Rap1 and HIF-1 signalings.

Conclusions

The proteomic profiles obtained in this study demonstrated the technical feasibility to elucidate protein candidates differentially expressed in FFPE tissues of LPIA. Our results may provide candidates of disease-oriented proteins which may be related to mechanisms of the early-stage progression of lung adenocarcinoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s40169-015-0064-3) contains supplementary material, which is available to authorized users.

Anterior gradient protein 3 is associated with less aggressive tumors and better outcome of breast cancer patients

Anterior gradient protein (AGR) 3 is a highly related homologue of pro-oncogenic AGR2 and belongs to the family of protein disulfide isomerases. Although AGR3 was found in breast, ovary, prostate, and liver cancer, it remains of yet poorly defined function in tumorigenesis. This study aimed to determine AGR3 expression in a cohort of 129 primary breast carcinomas and evaluate the clinical and prognostic significance of AGR3 in these tumors. The immunohistochemical analysis revealed the presence of AGR3 staining to varying degrees in 80% of analyzed specimens. The percentage of AGR3-positive cells significantly correlated with estrogen receptor, progesterone receptor (both P<0.0001) as well as low histological grade (P=0.003), and inversely correlated with the level of Ki-67 expression (P<0.0001). In the whole cohort, AGR3 expression was associated with longer progression-free survival (PFS), whereas AGR3-positive subgroup of low-histological grade tumors showed both significantly longer PFS and overall survival. In conclusion, AGR3 is associated with the level of differentiation, slowly proliferating tumors, and more favorable prognosis of breast cancer patients.

Mechanisms of anterior gradient-2 regulation and function in cancer

Proteins targeted to secretory pathway enter the endoplasmic reticulum where they undergo post-translational modification and subsequent quality control executed by exquisite catalysts of protein folding, protein disulphide isomerases (PDIs). These enzymes can often provide strict conformational protein folding solutions to highly cysteine-rich cargo as they facilitate disulphide rearrangement in the endoplasmic reticulum. Under conditions when PDI substrates are not isomerised properly, secreted proteins can accumulate in the endoplasmic reticulum leading to endoplasmic reticulum stress initiation with implications for human disease development. Anterior Gradient-2 (AGR2) is an endoplasmic reticulum-resident PDI superfamily member that has emerged as a dominant effector of basic biological properties in vertebrates including blastoderm formation and limb regeneration. AGR2 perturbation in mammals influences disease processes including cancer progression and drug resistance, asthma, and inflammatory bowel disease. This review will focus on the molecular characteristics, function, and regulation of AGR2, views on its emerging biological functions and misappropriation in disease, and prospects for therapeutic intervention into endoplasmic reticulum-resident protein folding pathways for improving the treatment of human disease.

New Blocking Antibodies against Novel AGR2-C4.4A Pathway Reduce Growth and Metastasis of Pancreatic Tumors and Increase Survival in Mice

Anterior gradient 2 (AGR2) promotes cancer growth, metastasis, and resistance to therapy via unknown mechanisms. We investigated the effects of extracellular AGR2 signaling through the orphan glycosylphosphatidylinositol-linked receptor C4.4A in pancreatic ductal adenocarcinoma (PDAC). Proliferation, migration, invasion, and apoptosis were measured using colorimetric, Boyden chamber, and FACS analyses. We developed blocking mAbs against AGR2 and C4.4A and tested their effects, along with siRNAs, on cancer cell functions and on orthotopic tumors in nude mice. Extracellular AGR2 stimulated proliferation, migration, invasion, and chemoresistance of PDAC cell lines. AGR2 interacted with C4.4A in cell lysates and mixtures of recombinant proteins. Knockdown of C4.4A reduced migration and resistance to gemcitabine. PDAC tissues, but not adjacent healthy pancreatic tissues, expressed high levels of AGR2 and C4.4A. AGR2 signaling through C4.4A required laminins 1 or 5 and integrin β1. Administration of antibodies against AGR2 and C4.4A reduced growth and metastasis and caused regression of aggressive xenograft tumors, leading to increased survival of mice. These data support a model in which AGR2 binds and signals via C4.4A in an autocrine loop and promotes the growth of pancreas tumors in mice. Blocking mAbs against AGR2 and C4.4A may have therapeutic potential against PDAC.

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.

The role of AGR2 and AGR3 in cancer: similar but not identical

In the past decades, highly related members of the protein disulphide isomerase family, anterior gradient protein AGR2 and AGR3, attracted researchers' attention due to their putative involvement in developmental processes and carcinogenesis. While AGR2 has been widely demonstrated as a metastasis-related protein whose elevated expression predicts worse patient outcome, little is known about AGR3's role in tumour biology. Thus, we aim to confront the issue of AGR3 function in physiology and pathology in the following review by comparing this protein with the better-described homologue AGR2. Relying on available data and in silico analyses, we show that AGR proteins are co-expressed or uncoupled in context-dependent manners in diverse carcinomas and healthy tissues. Further, we discuss plausible roles of both proteins in tumour-associated processes such as differentiation, proliferation, migration, invasion and metastasis. This work brings new hints and stimulates further thoughts on hitherto unresolved conundrum of anterior gradient protein function.

Agr2 mediates paracrine effects on stromal fibroblasts that promote invasion by gastric signet-ring carcinoma cells

Agr2 is a disulfide isomerase residing in the endoplasmic reticulum (ER), which physiologically regulates protein folding and mediates resistance to ER stress. Agr2 is overexpressed in adenocarcinomas of various organs, where it participates in neoplastic transformation and metastasis, therefore acts as a pro-oncogenic protein. Besides its normal localization in the ER, Agr2 is also found in the serum and urine of cancer patients, although the physiological significance of extracellular Agr2 is poorly understood. In this study, we demonstrated that extracellular Agr2 can activate stromal fibroblasts and promote fibroblast-associated cancer invasion in gastric signet-ring cell carcinoma (SRCC), where Agr2 is highly expressed. Agr2 secreted from SRCC cells was incorporated by the surrounding gastric fibroblasts and promoted invasion by these cells. In turn, activated fibroblasts coordinated the invasive behavior of fibroblasts and cancer cells. Our findings suggested that Agr2 drives progression of gastric SRCC by exerting paracrine effects on fibroblasts in the tumor microenvironment, acting also to increase the growth and resistance of SRCC cells to oxidative and hypoxic stress as cell autonomous effects.

Knockdown of anterior gradient 2 expression extenuates tumor-associated phenotypes of SNU-478 ampulla of Vater cancer cells

Background

Anterior gradient 2 (AGR2) has been implicated in tumor-associated phenotypes such as cell viability, invasion and metastasis in various human cancers. However, the tumor promoting activity of AGR2 has not yet been determined in biliary tract cancers. Thus, we examined the expression of AGR2 and its tumor-promoting activity in biliary tract cancer cells in this study.

Methods

Expression of AGR2 mRNA and protein was analyzed by real time RT-PCR and western blotting, respectively. MTT assay was employed to measure cell viability and pulsed BrdU incorporation by proliferating cells was monitored by flow cytometry. Soft agar colony formation assay and transwell invasion assay were employed to determine anchorage-independent growth and in vitro invasion of the tumor cells, respectively. In vivo tumor formation was examined by injection of tumor cells into immunocompromised mice subcutaneously. Statistical analysis was performed with 2-tailed unpaired Student’s t-test for continuous data and with one-way ANOVA for multiple group comparisons. Bonferroni tests were used for post hoc 2-sample comparisons.

Results

AGR2 mRNA was detected in SNU-245, SNU-478, and SNU-1196 cell lines, and its protein expression was confirmed in SNU-478 and SNU-245 cell lines by western blot analysis. Knockdown of AGR2 expression with an AGR2-specific short hairpin RNA (shRNA) in SNU-478, an ampulla of Vater cancer cell line resulted in decreased cell viability and in decreased anchorage-independent growth by 98%. The AGR2 knockdown also increased the sensitivity of the cells to chemotherapeutic drugs, including gemcitabine, 5-fluorouracil and cisplatin. In addition, SNU-478 cells expressing AGR2-shRNA failed to form detectable tumor xenografts in nude mice, whereas control cells formed tumors with an average size of 179 ± 84 mm³ in 3 weeks. Overexpression of AGR2 in SNU-869 cells significantly increased cell viability through enhanced cell proliferation and the number of Matrigel™-invading cells compared with AGR2-negative SNU-869 cells.

Conclusions

Our findings implicate that AGR2 expression augments tumor-associated phenotypes by increasing proliferative and invasive capacities of the ampulla of Vater cancer cells.

Dicer regulates differentiation and viability during mouse pancreatic cancer initiation

miRNA levels are altered in pancreatic ductal adenocarcinoma (PDA), the most common and lethal pancreatic malignancy, and intact miRNA processing is essential for lineage specification during pancreatic development. However, the role of miRNA processing in PDA has not been explored. Here we study the role of miRNA biogenesis in PDA development by deleting the miRNA processing enzyme Dicer in a PDA mouse model driven by oncogenic Kras. We find that loss of Dicer accelerates Kras driven acinar dedifferentiation and acinar to ductal metaplasia (ADM), a process that has been shown to precede and promote the specification of PDA precursors. However, unconstrained ADM also displays high levels of apoptosis. Dicer loss does not accelerate development of Kras driven PDA precursors or PDA, but surprisingly, we observe that mouse PDA can develop without Dicer, although at the expense of proliferative capacity. Our data suggest that intact miRNA processing is involved in both constraining pro-tumorigenic changes in pancreatic differentiation as well as maintaining viability during PDA initiation.

Differential expression of anterior gradient protein 3 in intrahepatic cholangiocarcinoma and hepatocellular carcinoma

Intrahepatic cholangiocarcinoma (ICC) is the second most common primary liver cancer next to hepatocellular carcinoma (HCC). Despite the significant difference of the therapeutic strategy for both diseases, their histological appearance may be very similar. Thus the correct diagnosis is crucial for treatment choice but is often difficult to achieve. The aim of our study was to evaluate anterior gradient 3 (AGR3) as a new diagnostic marker helping to distinguish between ICC and HCC. AGR3 is a putative transmembrane protein implicated in breast, prostate and ovary tumorigenesis and belongs to the family of protein disulfide isomerases. Since there is little information on how AGR3 is expressed in normal and diseased tissues and what its exact function is, we analyzed its expression pattern in normal liver and tumor tissue of ICC and HCC. The immunohistochemical analysis in normal tissue revealed specific AGR3 expression in intrahepatic bile duct cholangiocytes which was not present in liver hepatocytes. Consequently we analyzed AGR3 expression in 74 representative samples of puncture biopsies, tissue excisions and resection specimens from which 48 samples were diagnosed as HCC and 26 as ICC. Our results showed AGR3 expression negative and weakly positive respectively in hepatocellular carcinomas compared to stronger AGR3 positivity in cholangiocellular carcinomas. AGR3 expression statistically significantly correlated to acid mucopolysaccharide expression and negatively correlated to glypican-3 expression. We conclude that according to receiver operating characteristics (ROC) analysis AGR3 expression is relatively specific for ICC and is potentially linked to mucosecretion, which may indicate potential implication in treatment resistance.

Engineering a synthetic cell panel to identify signalling components reprogrammed by the cell growth regulator anterior gradient-2

AGR2 forms an ER-resident signalling axis in cell development, limb regeneration, and in human diseases like asthma and cancer, yet molecular mechanisms underlying its effects remain largely undefined. A single integrated Flippase recombination target (FRT) site was engineered within the AGR2-non expressing A375 cell line to allow integration of a constitutively expressed AGR2 alleles. This allows an analysis of how AGR2 protein expression reprogrammes intracellular signalling. The engineered expression of AGR2 had marginal impact on global transcription signalling, compared to its paralogue AGR3. However, expression of AGR2 had a significant impact on remodelling the cellular proteome using a triple-labelled SILAC protocol. 29 045 peptides were detected for the identification and relative quantitation of 3003 proteins across the experimental conditions. Ingenuity Pathway annotation highlighted the dominant pathway suppressed by wt-AGR2 was the p53-signalling axis. DNA damage induced p53 stabilization and p21 induction by cisplatin treatment confirmed that wt-AGR2 expression suppressed the p53 pathway. The furthest outlying SILAC protein expression change induced by AGR2 was the anti-viral and cell cycle regulator tumour susceptibility gene 101 (TSG101), confirmed by immunoblotting. Transfection of TSG101 into MCF7 (AGR2+, oestrogen dependent), A549 (AGR2+, oestrogen independent) or A375 (AGR2-) cells confirmed that TSG101 attenuates p53 signalling. These systems wide screens suggest that the most dominant landscape reprogrammed by low levels of AGR2 protein is the cellular proteome, rather than the transcriptome, and provide focus for evaluating its role in proteostasis.