Anterior Gradient 2 (AGR2) Induced Epidermal Growth Factor Receptor (EGFR) Signaling Is Essential for Murine Pancreatitis-Associated Tissue Regeneration

New insights into the unfolded protein response (UPR)-anterior gradient 2 (AGR2) pathway in the regulation of intestinal barrier function in weaned piglets

Sustained dysfunction of the intestinal barrier caused by early weaning is a major factor that induces postweaning diarrhea in weaned piglets. In both healthy and diseased states, the intestinal barrier is regulated by goblet cells. Alterations in the characteristics of goblet cells are linked to intestinal barrier dysfunction and inflammatory conditions during pathogenic infections. In this review, we summarize the current understanding of the mechanisms of the unfolded protein response (UPR) and anterior gradient 2 (AGR2) in maintaining intestinal barrier function and how modifications to these systems affect mucus barrier characteristics and goblet cell dysregulation. We highlight a novel mechanism underlying the UPR-AGR2 pathway, which affects goblet cell differentiation and maturation and the synthesis and secretion of mucin by regulating epidermal growth factor receptor and mucin 2. This study provides a theoretical basis and new insights into the regulation of intestinal health in weaned piglets.

Potential Role of AGR2 for Mammalian Skin Wound Healing

The limited ability of mammals to regenerate has garnered significant attention, particularly in regard to skin wound healing (WH), which is a critical step for regeneration. In human adults, skin WH results in the formation of scars following injury or trauma, regardless of severity. This differs significantly from the scarless WH observed in the fetal skin of mammals or anamniotes. This review investigates the role of molecular players involved in scarless WH, which are lost or repressed in adult mammalian WH systems. Specifically, we analyze the physiological role of Anterior Gradient (AGR) family proteins at different stages of the WH regulatory network. AGR is activated in the regeneration of lower vertebrates at the stage of wound closure and, accordingly, is important for WH. Mammalian AGR2 is expressed during scarless WH in embryonic skin, while in adults, the activity of this gene is normally inhibited and is observed only in the mucous epithelium of the digestive tract, which is capable of full regeneration. The combination of AGR2 unique potencies in postnatal mammals makes it possible to consider it as a promising candidate for enhancing WH processes.

REL-NPMI: Exploring genotype and phenotype relationship of pancreatitis based on improved normalized point-by-point mutual information

Pancreatitis is a relatively serious disease caused by the self-digestion of trypsin in the pancreas. The generation of diseases is closely related to gene and phenotype information. Generally, gene-phenotype relations are mainly obtained through clinical experiments, but the cost is huge. With the amount of published biomedical literature increasing exponentially, it carries a wealth of disease-related gene and phenotype information. This study provided an effective way to obtain disease-related gene and phenotype information. To our best knowledge, this work first attempted to explore relationships between genotype and phenotype about the pancreatitis from the computational perspective. It mined 6152 genes and 76,753 pairs of genotype and phenotype extracted from the biomedical literature about pancreatitis using text mining. Based on the above 76,753 pairs, the study proposed an improved normalized point-wise mutual information (REL-NPMI) model to optimize gene-phenotype relations related to pancreatitis, and obtained 12,562 gene-phenotype pairs which may be related to pancreatitis. The extracted top 20 results were validated and evaluated. The experimental results show that the method is promising for exploring pancreatitis' molecular mechanism, thus it provides a computational way for studying pancreatitis' disease pathogenesis. Data resources and the Pancreatitis Gene-Phenotype Association Database are available at http://114.116.4.45:8081/and resources are also available at https://github.com/polipoptbe8023/REL-NPMI.git.

The anterior gradient homologue 2 (AGR2) co-localises with the glucose-regulated protein 78 (GRP78) in cancer stem cells, and is critical for the survival and drug resistance of recurrent glioblastoma: in situ and in vitro analyses

BACKGROUND

Glioblastomas (GBs) are characterised as one of the most aggressive primary central nervous system tumours (CNSTs). Single-cell sequencing analysis identified the presence of a highly heterogeneous population of cancer stem cells (CSCs). The proteins anterior gradient homologue 2 (AGR2) and glucose-regulated protein 78 (GRP78) are known to play critical roles in regulating unfolded protein response (UPR) machinery. The UPR machinery influences cell survival, migration, invasion and drug resistance. Hence, we investigated the role of AGR2 in drug-resistant recurrent glioblastoma cells.

METHODS

Immunofluorescence, biological assessments and whole exome sequencing analyses were completed under in situ and in vitro conditions. Cells were treated with CNSTs clinical/preclinical drugs taxol, cisplatin, irinotecan, MCK8866, etoposide, and temozolomide, then resistant cells were analysed for the expression of AGR2. AGR2 was repressed using single and double siRNA transfections and combined with either temozolomide or irinotecan.

RESULTS

Genomic and biological characterisations of the AGR2-expressed Jed66_GB and Jed41_GB recurrent glioblastoma tissues and cell lines showed features consistent with glioblastoma. Immunofluorescence data indicated that AGR2 co-localised with the UPR marker GRP78 in both the tissue and their corresponding primary cell lines. AGR2 and GRP78 were highly expressed in glioblastoma CSCs. Following treatment with the aforementioned drugs, all drug-surviving cells showed high expression of AGR2. Prolonged siRNA repression of a particular region in AGR2 exon 2 reduced AGR2 protein expression and led to lower cell densities in both cell lines. Co-treatments using AGR2 exon 2B siRNA in conjunction with temozolomide or irinotecan had partially synergistic effects. The slight reduction of AGR2 expression increased nuclear Caspase-3 activation in both cell lines and caused multinucleation in the Jed66_GB cell line.

CONCLUSIONS

AGR2 is highly expressed in UPR-active CSCs and drug-resistant GB cells, and its repression leads to apoptosis, via multiple pathways.

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.

A 3D system to model human pancreas development and its reference single-cell transcriptome atlas identify signaling pathways required for progenitor expansion

Human organogenesis remains relatively unexplored for ethical and practical reasons. Here, we report the establishment of a single-cell transcriptome atlas of the human fetal pancreas between 7 and 10 post-conceptional weeks of development. To interrogate cell–cell interactions, we describe InterCom, an R-Package we developed for identifying receptor–ligand pairs and their downstream effects. We further report the establishment of a human pancreas culture system starting from fetal tissue or human pluripotent stem cells, enabling the long-term maintenance of pancreas progenitors in a minimal, defined medium in three-dimensions. Benchmarking the cells produced in 2-dimensions and those expanded in 3-dimensions to fetal tissue identifies that progenitors expanded in 3-dimensions are transcriptionally closer to the fetal pancreas. We further demonstrate the potential of this system as a screening platform and identify the importance of the EGF and FGF pathways controlling human pancreas progenitor expansion.

From single-cell transcriptome analyses to defining culture media for spheroids, the authors provide a census of information to understand the development of human pancreatic progenitors. This approach identifies signalling pathways (EGF and FGF) regulating progenitor proliferation.

Anterior Gradient Protein 2 Promotes Mucosal Repair in Pediatric Ulcerative Colitis

Mucosal healing comprises a key goal of ulcerative colitis (UC) treatment. Anterior gradient protein 2 (AGR2) plays an important role in maintaining intestinal homeostasis in UC. However, the role of AGR2 in the repair of mucosal injury is not yet clear. This study is aimed at investigating the expression of AGR2 in the intestinal tissues of children with UC and its role in repairing mucosal injury. Forty UC patients who were hospitalized in the Pediatric Gastroenterology Ward of Shengjing Hospital affiliated with China Medical University between July 1, 2013, and May 31, 2020, and 20 children who had normal colonoscopy results during the same period (control group) made up the study sample. The disease activity of UC was evaluated based on the pediatric ulcerative colitis activity index, and the ulcerative colitis endoscopic index was evaluated according to the Rachmilewitz score. Immunohistochemical staining was employed to examine the differences in AGR2 expression in the intestinal mucosa between groups. The protective effect of AGR2 in a model of tumor necrosis factor-alpha- (TNF-α-) induced intestinal mucosal barrier injury and the underlying molecular mechanism were explored through in vitro experiments. The results showed that compared with the normal control group, UC patients in the remission or active period had significantly higher expression of AGR2 in the intestine. AGR2 expression was positively correlated with Ki67, an intestinal epithelial cell proliferation marker, but negatively correlated with the degree of endoscopic mucosal injury. In an in vitro model, AGR2 overexpression promoted cell proliferation and migration and inhibited TNF-α-induced intestinal epithelial barrier damage by activating yes-associated protein (YAP). Collectively, our study suggests that AGR2 might serve as a valuable biomarker to help assess the condition and mucosal healing status of UC patients. In vitro, AGR2 promoted the repair of intestinal mucosal barrier injury by activating YAP.

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.

Laser-assisted 3D bioprinting of exocrine pancreas spheroid models for cancer initiation study

Pancreatic ductal adenocarcinoma (PDAC) is the most common malignancy of the pancreas. It has shown a poor prognosis and a rising incidence in the developed world. Other pathologies associated with this tissue include pancreatitis, a risk condition for pancreatic cancer. The onset of both pancreatitis and pancreatic cancer follows a common pattern: exocrine pancreatic acinar cells undergo a transdifferentiation to duct cells that triggers a 3D restructuration of the pancreatic tissue. However, the exact mechanism underlying this process remains partially undefined. Further understanding the cellular events leading to PDAC could open new avenues in the development of novel therapeutic approaches. Since current 2D cell culture models fail to mimic the tridimensional complexity of the pancreatic tissue, new in vitro models are urgently needed. Here, we generated 3D pancreatic cell spheroid arrays using laser-assisted bioprinting and characterized their phenotypic evolution over time through image analysis and phenotypic characterization. We show that these bioprinted spheroids, composed of both acinar and ductal cells, can replicate the initial stages of PDAC development. This bioprinted miniaturized spheroid-based array model should prove useful for the study of the internal and external factors that contribute to the formation of precursor PDAC lesions and to cancer progression, and may therefore shed light on future PDAC therapy strategies.

Finite cell lines of turkey sperm storage tubule cells: ultrastructure and protein analysis

Cell lines of turkey sperm storage tubule (SST) epithelial cells were established. Turkey SSTs were dissected from freshly obtained uterovaginal junction (UVJ) tissue and placed in explant culture on various substrates and media. Primary cultures of SST epithelium only survived and grew from SST explants that were cultured on inactivated Sandoz inbred strain, thioguanine- and ouabain-resistance (STO) mouse feeder-cell layers in 12% fetal bovine serum-supplemented Dulbecco's Modified Eagle Medium mixed 1:1 with F12 nutrient mixture. Three independent primary colonies gave rise to 3 finite cell lines, SST-1, -2, and -3, which were continuously cultured for 8 to 16 passages at 1:3 passage ratios over a period of 3 to 4 mo. The cells were passaged by pretreatment with Y27632 and dissociation with Accutase. The SST cells grew as tightly knit monolayers on top of the feeder cells at a slow rate (approximately 96 h doubling time) at a medium pH of approximately 6.9. Lipid vacuoles were visible by light microscopy in the cells particularly at the periphery of growth. Transmission electron microscopy revealed the cells to be a polarized epithelium with apical microvilli and to have lateral tight-junction-like unions and associated desmosomes. Numerous secretory vesicles filled the upper portion of the cells’ cytoplasm, and nuclei and other major organelles such as mitochondria, rough endoplasmic reticulum, and Golgi apparatus were distributed somewhat lower in the cytoplasm. The secretory vesicles resembled mucin secretory vesicles. Proteomic analysis by mass spectroscopy of the conditioned medium of the cells, and of the cells themselves, showed the cell lines did not secrete large amounts of any particular protein, and the analysis confirmed their epithelial character. In conclusion, the SST-derived cell lines resembled the mucus-secreting cells found in the epithelium lining the UVJ of the turkey's reproductive tract.

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.

Pancreatic gene expression during recovery after pancreatitis reveals unique transcriptome profiles

It is well known that pancreatic recovery after a single episode of injury such as an isolated bout of pancreatitis occurs rapidly. It is unclear, however, what changes are inflicted in such conditions to the molecular landscape of the pancreas. In the caerulein hyperstimulation model of pancreatitis, the murine pancreas has the ability to recover within one week based on histological appearance. In this study, we sought to characterize by RNA-sequencing (RNA-seq) the transcriptional profile of the recovering pancreas up to two weeks post-injury. We found that one week after injury there were 319 differentially expressed genes (DEGs) compared with baseline and that after two weeks there were 53 DEGs. Forty (12.5%) of the DEGs persisted from week one to week two, and another 13 DEGs newly emerged in the second week. Amongst the top up-regulated DEGs were several trypsinogen genes (trypsinogen 4, 5, 12, 15, and 16). To our knowledge, this is the first characterization of the transcriptome during pancreatic recovery by deep sequencing, and it reveals on a molecular basis that there is an ongoing recovery of the pancreas even after apparent histological resolution. The findings also raise the possibility of an emerging novel transcriptome upon pancreatic recovery.

Anterior gradient 2 is induced in cutaneous wound and promotes wound healing through its adhesion domain

Anterior gradient 2 (AGR2), a member of protein disulfide isomerase (PDI) family, is both located in cytoplasm and secreted into extracellular matrix. The orthologs of AGR2 have been linked to limb regeneration in newt and wound healing in zebrafish. In mammals, AGR2 influences multiple cell signaling pathways in tumor formation and in normal cell functions related to new tissue formation like angiogenesis. However, the function of AGR2 in mammalian wound healing remains unknown. This study aimed to investigate AGR2 expression and its function during skin wound healing and the possible application of external AGR2 in cutaneous wound to accelerate the healing process. Our results showed that AGR2 expression was induced in the migrating epidermal tongue and hyperplastic epidermis after skin excision. Topical application of recombinant AGR2 significantly accelerated wound-healing process by increasing the migration of keratinocytes (Kera.) and the recruitment of fibroblasts (Fibro.) near the wounded area. External AGR2 also promoted the migration of Kera. and Fibro. in vitro in a dose-dependent manner. The adhesion domain of AGR2 was required for the formation of focal adhesions in migrating Fibro., leading to the directional migration along AGR2 gradient. These results indicate that recombinant AGR2 accelerates skin wound healing through regulation of Kera. and Fibro. migration, thus demonstrating its potential utility as an alternative strategy of the therapeutics to accelerate the healing of acute or chronic skin wounds.