Anterior Gradient-2 monoclonal antibody inhibits lung cancer growth and metastasis by upregulating p53 pathway and without exerting any toxicological effects: A preclinical study

Advances in understanding the molecular mechanisms of borderline ovarian tumors

Borderline ovarian tumors (BOTs), which are a special type of epithelial tumor of the ovary, lie between benign and malignant tumors and have low malignant potential. Due to the fact that the early symptoms of these tumors are relatively subtle, they are not easy to diagnose clinically. This study explores advancements in clinical detection methods and provides a comprehensive overview of molecules such as cell migration factors, cell transcription factors, cell damage repair factors, cell cycle regulators, and tumor suppressor genes that are related to the development of BOTs and their related mechanisms in recent years, thus aiming to provide more sensitive, specific, and efficient differential diagnosis and treatment plans for patients to improve their prognosis and survival outcomes.

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.

AGR2-mediated unconventional secretion of 14-3-3ε and α-actinin-4, responsive to ER stress and autophagy, drives chemotaxis in canine mammary tumor cells

BACKGROUND

Canine mammary tumors (CMTs) in intact female dogs provide a natural model for investigating metastatic human cancers. Our prior research identified elevated expression of Anterior Gradient 2 (AGR2), a protein disulfide isomerase (PDI) primarily found in the endoplasmic reticulum (ER), in CMT tissues, highly associated with CMT progression. We further demonstrated that increased AGR2 expression actively influences the extracellular microenvironment, promoting chemotaxis in CMT cells. Unraveling the underlying mechanisms is crucial for assessing the potential of therapeutically targeting AGR2 as a strategy to inhibit a pro-metastatic microenvironment and impede tumor metastasis.

METHODS

To identify the AGR2-modulated secretome, we employed proteomics analysis of the conditioned media (CM) from two CMT cell lines ectopically expressing AGR2, compared with corresponding vector-expressing controls. AGR2-regulated release of 14-3-3ε (gene: YWHAE) and α-actinin 4 (gene: ACTN4) was validated through ectopic expression, knockdown, and knockout of the AGR2 gene in CMT cells. Extracellular vesicles derived from CMT cells were isolated using either differential ultracentrifugation or size exclusion chromatography. The roles of 14-3-3ε and α-actinin 4 in the chemotaxis driven by the AGR2-modulated CM were investigated through gene knockdown, antibody-mediated interference, and recombinant protein supplement. Furthermore, the clinical relevance of the release of 14-3-3ε and α-actinin 4 was assessed using CMT tissue-immersed saline and sera from CMT-afflicted dogs.

RESULTS

Proteomics analysis of the AGR2-modulated secretome revealed increased abundance in 14-3-3ε and α-actinin 4. Ectopic expression of AGR2 significantly increased the release of 14-3-3ε and α-actinin 4 in the CM. Conversely, knockdown or knockout of AGR2 expression remarkably reduced their release. Silencing 14-3-3ε or α-actinin 4 expression diminished the chemotaxis driven by AGR2-modulated CM. Furthermore, AGR2 controls the release of 14-3-3ε and α-actinin 4 primarily via non-vesicular routes, responding to the endoplasmic reticulum (ER) stress and autophagy activation. Knockout of AGR2 resulted in increased α-actinin 4 accumulation and impaired 14-3-3ε translocation in autophagosomes. Depletion of extracellular 14-3-3ε or α-actinin 4 reduced the chemotaxis driven by AGR2-modulated CM, whereas supplement with recombinant 14-3-3ε in the CM enhanced the CM-driven chemotaxis. Notably, elevated levels of 14-3-3ε or α-actinin 4 were observed in CMT tissue-immersed saline compared with paired non-tumor samples and in the sera of CMT dogs compared with healthy dogs.

CONCLUSION

This study elucidates AGR2's pivotal role in orchestrating unconventional secretion of 14-3-3ε and α-actinin 4 from CMT cells, thereby contributing to paracrine-mediated chemotaxis. The insight into the intricate interplay between AGR2-involved ER stress, autophagy, and unconventional secretion provides a foundation for refining strategies aimed at impeding metastasis in both canine mammary tumors and potentially human cancers.

Construction and stable gene expression of AGR2xPD1 bi-specific antibody that enhances attachment between T-Cells and lung tumor cells, suppress tumor cell migration and promoting CD8 expression in cytotoxic T-cells

There has been a substantial and consistent rise in the number of clinical trials to develop advanced and potent bispecific antibodies (BsAb) over the past two decades with multiple targets to improve the efficacy or tissue specificity of monoclonal antibodies (mAb) treatment for diseases with multiple determining factors or widely-expressed targets. In this study, we designed and synthesized BsAb AGR2xPD1 targeting extracellular AGR2, a paracrine signal, and PD1, an immune checkpoint protein. Our design is intended to use AGR2 binding to guide PD1 targeting for AGR2⁺cancer. We used this construction to produce AGR2xPD1 BsAb by generating clonally selected stable 293F cell line with high expression. Applying this BsAb in a T cell-Tumor cell co-culture system showed that targeting both PD1 and AGR2 with this BsAb induces the attachment of TALL-104 (CD8⁺ T-lymphocytes) cells onto co-cultured H460 AGR2⁺ Lung tumor cells and significantly reduces migration of H460 cells. T-cell expression of CD8 and IFNγ is also synergistically enhanced by the AGR2xPD1 BsAb treatment in the AGR2⁺H460 co-culture system. These effects are significantly reduced with AGR2 expression negative WI38 cells. Our results demonstrate that the AGR2xPD1 BsAb could be a potential therapeutic agent to provide better solid tumor targeting and synergetic efficacy for treating AGR2+ cancer by blocking AGR2 paracrine signaling to reduce tumor survival, and redirecting cytotoxic T-cells into AGR2+ cancer cells.

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.

Influencing factors and prediction methods of radiotherapy and chemotherapy in patients with lung cancer based on logistic regression analysis

Logistic regression analysis has widespread applications in clinical disease diagnosis, but it has not yet been applied to assess the acceptance of radiotherapy and chemotherapy in patients with lung cancer. A prediction model was established to investigate the influencing factors of radiotherapy and chemotherapy in lung cancer patients in order to provide useful information for clinicians to develop targeted and effective treatment. A sample was admitted of lung cancer patients to Binzhou Medical University Hospital stays from January 2020 to June 2021. After investigating doctors, nurses, patients, managers and conducting expert demonstration, the questionnaire was formed. The questionnaire was filled out by the patient or the patient's family members. The factors in the questionnaire data of patients accepting and not accepting radiotherapy and chemotherapy were compared for univariate analysis, and the significantly different single factor were analyzed by multifactor logistic regression analysis, explored the influencing factors of radiotherapy and chemotherapy in lung cancer patients established a predictive model and drew the receiver operating characteristic curve (ROC curve). The factors of two groups had statistically significant differences or no statistically significant differences. After multifactor logistic regression analysis was conducted, own personality, self-care ability, disease course classification, own attitude towards disease treatment, and family attitude towards disease treatment were included in the influencing factors of radiotherapy and chemotherapy in patients with lung cancer. Then, a predictive model was established. The area under the ROC curve of the predicted model was 0.973, the 95% confidence interval was 0.952-0.995, the optimal critical value was 0.832, the sensitivity was 91.84%, the specificity was 89.09%, and the accuracy was 90.85%. Based on logistic regression analysis, the prediction model could predict the extent of accepting radiotherapy and chemotherapy in patients with lung cancer. Understanding the factors related to patients with lung cancer accepting radiotherapy and chemotherapy could provide useful information for the targeted and effective treatment by clinicians.

Microenvironment components and spatially resolved single-cell transcriptome atlas of breast cancer metastatic axillary lymph nodes

As an indicator of clinical prognosis, lymph node metastasis of breast cancer has drawn great attention. Many reports have revealed the characteristics of metastatic breast cancer cells, however, the effect of breast cancer cells on the microenvironment components of lymph nodes and spatial transcriptome atlas remains unclear. In this study, by integrating single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics, we investigate the transcriptional profiling of six surgically excised lymph node samples and the spatial organization of one positive lymph node. We identify the existence of osteoclast-like giant cells (OGC) which have high expressions of CD68 and CD163, the biomarkers of tumor-associated macrophages (TAMs). Through a spatially resolved transcriptomic method, we find that OGCs are scattered among metastatic breast cancer cells. In the lymph node microenvironment with breast cancer cell infiltration, TAMs are enriched in protumoral pathways including NF-κB signaling pathways and NOD-like receptor signaling pathways. Further subclustering demonstrates the potential differentiation trajectory in which macrophages develop from a state of active chemokine production to a state of active lymphocyte activation. This study is the first to integrate scRNA-seq and spatial transcriptomics in the tumor microenvironment of axillary lymph nodes, offering a systematic approach to delve into breast cancer lymph node metastasis.

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.

Endoplasmic Reticulum Stress-Related Signature for Predicting Prognosis and Immune Features in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) with cancer cells under endoplasmic reticulum (ER) stress has a poor prognosis. This study is aimed at discovering credible biomarkers for predicting the prognosis of HCC based on ER stress-related genes (ERSRGs). We constructed a novel four-ERSRG prognostic risk model, including PON1, AGR2, SSR2, and TMCC1, through a series of bioinformatic approaches, which can accurately predict survival outcomes in HCC patients. Higher risk scores were linked to later grade, recurrence, advanced TNM stage, later T stage, and HBV infection. In addition, 20 fresh frozen tumors and normal tissues from HCC patients were collected and used to validate the genes expressed in the signature by qRT-PCR and immunohistochemical (IHC) assays. Moreover, we found the ER stress-related signature could reflect the infiltration levels of different immune cells in the tumor microenvironment (TME) and forecast the efficacy of immune checkpoint inhibitor (ICI) treatment. Finally, we created a nomogram incorporating this ER stress-related signature. In conclusion, our constructed four-gene risk model associated with ER stress can accurately predict survival outcomes in HCC patients, and the model's risk score is associated with the poor clinical classification.

Functions and mechanisms of protein disulfide isomerase family in cancer emergence

The endoplasmic reticulum (ER) is a multi-layered organelle that is essential for the synthesis, folding, and structural maturation of almost one-third of the cellular proteome. It houses several resident proteins for these functions including the 21 members of the protein disulfide isomerase (PDI) family. The signature of proteins belonging to this family is the presence of the thioredoxin domain which mediates the formation, and rearrangement of disulfide bonds of substrate proteins in the ER. This process is crucial not only for the proper folding of ER substrates but also for maintaining a balanced ER proteostasis. The inclusion of new PDI members with a wide variety of structural determinants, size and enzymatic activity has brought additional epitomes of how PDI functions. Notably, some of them do not carry the thioredoxin domain and others have roles outside the ER. This also reflects that PDIs may have specialized functions and their functions are not limited within the ER. Large-scale expression datasets of human clinical samples have identified that the expression of PDI members is elevated in pathophysiological states like cancer. Subsequent functional interrogations using structural, molecular, cellular, and animal models suggest that some PDI members support the survival, progression, and metastasis of several cancer types. Herein, we review recent research advances on PDIs, vis-à-vis their expression, functions, and molecular mechanisms in supporting cancer growth with special emphasis on the anterior gradient (AGR) subfamily. Last, we posit the relevance and therapeutic strategies in targeting the PDIs in cancer.

Comparison of anti-cancer effects of novel protein disulphide isomerase (PDI) inhibitors in breast cancer cells characterized by high and low PDIA17 expression

Background

Protein disulphide isomerases (PDIs) play an important role in cancer progression. However, the relative contribution of the various isoforms of PDI in tumorigenesis is not clear.

Methods

The content of PDI isoforms in 22 cancer cells lines was investigated using LC–MS/MS-based proteomic analysis. The effects of PDIA1, PDIA3 and PDIA17 inhibition on the proliferation, migration and adhesion of MCF-7 and MDA-MB-231 cells, identified as high and low PDIA17 expressing cells, respectively, were assessed using novel aromatic N-sulphonamides of aziridine-2-carboxylic acid derivatives as PDI inhibitors.

Results

PDIA1 and PDIA3 were the most abundant in cancer cell lysates and were also detected extracellularly in breast cancer cells (MDA-MB-231 and MCF-7). Some cancer cell lines (e.g., MCF-7, HT-29) showed upregulated expression of PDIA17, whereas in others (e.g., MDA-MB-231, 67NR), PDIA17 was not detected. The simultaneous inhibition of PDIA1 and PDIA3 showed similar anti-proliferative effects in MCF-7 and MDA-MB-231 breast cancer cells. However, the inhibition of PDIA1 and PDIA17 in the MCF-7 cell line resulted in more effective anti-adhesive and anti-proliferative effects.

Conclusions

PDIA1 and PDIA3 represent major isoforms of multiple cancer cells, and their non-selective inhibition displays significant anti-proliferative effects irrespective of whether or not PDIA17 is present. The more pronounced anti-adhesive effects of PDI inhibition in hormone-sensitive MCF-7 cells featured by higher levels of PDIs when compared to triple-negative MDA-MB-231 cells suggests that targeting extracellular PDIA1 and PDIA3 with or without additional PDIA17 inhibition may represent a strategy for personalized anti-adhesive, anti-metastatic therapy in cancers with high PDI expression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02631-w.

EASINESS: E. coli Assisted Speedy affINity-maturation Evolution SyStem

Antibodies are one of the most important groups of biomolecules for both clinical and basic research and have been developed as potential therapeutics. Affinity is the key feature for biological activity and clinical efficacy of an antibody, especially of therapeutic antibodies, and thus antibody affinity improvement is indispensable and still remains challenging. To address this issue, we developed the E. coli Assisted Speed affINity-maturation Evolution SyStem (EASINESS) for continuous directed evolution of Ag-Ab interactions. Two key components of EASINESS include a mutation system modified from error-prone DNA polymerase I (Pol I) that selectively mutates ColE1 plasmids in E. coli and a protein-protein interaction selection system from mDHFR split fragments. We designed a GCN4 variant which barely forms a homodimer, and during a single round of evolution, we reversed the homodimer formation activity from the GCN4 variant to verify the feasibility of EASINESS. We then selected a potential therapeutic antibody 18A4Hu and improved the affinity of the antibody (18A4Hu) to its target (ARG2) 12-fold in 7 days while requiring very limited hands-on time. Remarkably, these variants of 18A4Hu revealed a significant improved ability to inhibit melanoma pulmonary metastasis in a mouse model. These results indicate EASINESS could be as an attractive choice for antibody affinity maturation.

Recent Advances in Functional Carbon Quantum Dots for Antitumour

Carbon quantum dots (CQDs) are an emerging class of quasi-zero-dimensional photoluminescent nanomaterials with particle sizes less than 10 nm. Owing to their favourable water dispersion, strong chemical inertia, stable optical performance, and good biocompatibility, CQDs have become prominent in biomedical fields. CQDs can be fabricated by “top-down” and “bottom-up” methods, both of which involve oxidation, carbonization, pyrolysis and polymerization. The functions of CQDs include biological imaging, biosensing, drug delivery, gene carrying, antimicrobial performance, photothermal ablation and so on, which enable them to be utilized in antitumour applications. The purpose of this review is to summarize the research progress of CQDs in antitumour applications from preparation and characterization to application prospects. Furthermore, the challenges and opportunities of CQDs are discussed along with future perspectives for precise individual therapy of tumours.

Extracellular AGR2 activates neighboring fibroblasts through endocytosis and direct binding to β-catenin that requires AGR2 dimerization and adhesion domains

Anterior gradient 2 (AGR2) is often overexpressed in several types of cancer. AGR2 is cytoplasmic or secreted as an extracellular signal. Intracellular AGR2 properties and role in cancer have been well studied, but its extracellular function is largely unclear. It has been shown that extracellular AGR2 activates endothelial cells and fibroblasts in culture, but the mechanism of AGR2 signaling is not well elucidated. Here, we report that tumor secreted or externally added AGR2 translocates into cytoplasm by endocytosis, binds to β-catenin and further co-translocates to the nucleus in NIH3T3 fibroblasts. Externally added AGR2 also increased β-catenin expression, stability, and accumulation in the nucleus in both fibroblasts and cancer cells. External AGR2 rescued the expression of β-catenin, which was suppressed by EGFR inhibitor AG1478 indicating an alternative pathway to regulate β-catenin independent of EGFR signal. These effects were abolished when a monoclonal antibody against AGR2 was added to the experiments, confirming the effects are caused by AGR2 only. Putting together, our results show that extracellular AGR2 signaling pathway involves endocytosis mediated cellular translocation, direct binding and regulating β-catenin nuclear accumulation. It is also a target against tumor initiated AGR2 signaling to form and maintain tumor microenvironment.

Prospect of Anterior Gradient 2 homodimer inhibition via repurposing FDA-approved drugs using structure-based virtual screening

Anterior Gradient 2 (AGR2) has recently been reported as a tumor biomarker in various cancers, i.e., breast, prostate and lung cancer. Predominantly, AGR2 exists as a homodimer via a dimerization domain (E60-K64); after it is self-dimerized, it helps FGF2 and VEGF to homo-dimerize and promotes the angiogenesis and the invasion of vascular endothelial cells and fibroblasts. Up till now, no small molecule has been discovered to inhibit the AGR2-AGR2 homodimer. Therefore, the present study was performed to prepare a validated 3D structure of AGR2 by homology modeling and discover a small molecule by screening the FDA-approved drugs library on AGR2 homodimer as a target protein. Thirteen different homology models of AGR2 were generated based on different templates which were narrowed down to 5 quality models sorted by their overall Z-scores. The top homology model based on PDB ID = 3PH9 was selected having the best Z-score and was further assessed by Verify-3D, ERRAT and RAMPAGE analysis. Structure-based virtual screening narrowed down the large library of FDA-approved drugs to ten potential AGR2-AGR2 homodimer inhibitors having FRED score lower than - 7.8 kcal/mol in which the top 5 drugs' binding stability was counter-validated by molecular dynamic simulation. To sum up, the present study prepared a validated 3D structure of AGR2 and, for the first time reported the discovery of 5 FDA-approved drugs to inhibit AGR2-AGR2 homodimer by using structure-based virtual screening. Moreover, the binding of the top 5 hits with AGR2 was also validated by molecular dynamic simulation. A validated 3D structure of Anterior Gradient 2 (AGR2) was prepared by homology modeling, which was used in virtual screening of FDA-approved drugs library for the discovery of prospective inhibitors of AGR2-AGR2 homodimer.

An Ultrasensitive Biosensor for Detection of Femtogram Levels of the Cancer Antigen AGR2 Using Monoclonal Antibody Modified Screen-Printed Gold Electrodes

The detection of cancer antigens is a major aim of cancer research in order to develop better patient management through early disease detection. Many cancers including prostate, lung, and ovarian secrete a protein disulfide isomerase protein named AGR2 that has been previously detected in urine and plasma using mass spectrometry. Here we determine whether a previously developed monoclonal antibody targeting AGR2 can be adapted from an indirect two-site ELISA format into a direct detector using solid-phase printed gold electrodes. The screen-printed gold electrode was surface functionalized with the anti-AGR2 specific monoclonal antibody. The interaction of the recombinant AGR2 protein and the anti-AGR2 monoclonal antibody functionalized electrode changed its electrochemical impedance spectra. Nyquist diagrams were obtained after incubation in an increasing concentration of purified AGR2 protein with a range of concentrations from 0.01 fg/mL to 10 fg/mL. In addition, detection of the AGR2 antigen can be achieved from cell lysates in medium or artificial buffer. These data highlight the utility of an AGR2-specific monoclonal antibody that can be functionalized onto a gold printed electrode for a one-step capture and quantitation of the target antigen. These platforms have the potential for supporting methodologies using more complex bodily fluids including plasma and urine for improved cancer diagnostics.

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.

Secretion of pro-oncogenic AGR2 protein in cancer

Anterior gradient-2 (AGR2) protein mediates the formation, breakage and isomerization of disulphide bonds during protein maturation in the endoplasmic reticulum (ER) and contributes to the homoeostasis of the secretory pathway. AGR2 promotes tumour development and metastasis and its elevated expression is almost completely restricted to malignant tumours. Interestingly, this supposedly ER-resident protein can be localised to other compartments of cancer cells and can also be secreted into the extracellular milieu. There are emerging evidences that describe the gain-of-function activities of the extracellular AGR2, particularly in cancer development. Here, we reviewed studies detailing the expression, pathological and physiological roles associated with AGR2 and compared the duality of localization, intracellular and extracellular, with special emphasis on the later. We also discussed the possible mechanisms of AGR2 secretion as well as deliberating the functional impacts of AGR2 in cancer settings. Last, we deliberate the current therapeutic strategies and posit the potential use AGR2, as a prognosis and diagnosis marker in cancer.

Paracrine signalling of AGR2 stimulates RhoA function in fibroblasts and modulates cell elongation and migration

The most prominent cancer-associated fibroblasts (CAFs) in tumor stroma is known to form a protective structure to support tumor growth. Anterior gradient-2 (AGR2), a tumor secretory protein is believed to play a pivotal role during tumor microenvironment (TME) development. Here, we report that extracellular AGR2 enhances fibroblasts elongation and migration significantly. The early stimulation of RhoA showed the association of AGR2 by upregulation of G1-S phase-regulatory protein cyclin D1 and FAK phosphorylation through fibroblasts growth factor receptor (FGFR) and vascular endothelial growth factor receptor (VEGFR). Our finding indicates that secretory AGR2 alters fibroblasts elongation, migration, and organization suggesting the secretory AGR2 as a potential molecular target that might be responsible to alter fibroblasts infiltration to support tumor growth.

AGR2, a unique tumor-associated antigen, is a promising candidate for antibody targeting

Anterior gradient 2 (AGR2), a protein disulfide isomerase, shows two subcellular localizations: intracellular (iAGR2) and extracellular (eAGR2). In healthy cells that express AGR2, the predominant form is iAGR2, which resides in the endoplasmic reticulum. In contrast, cancer cells secrete and express eAGR2 on the cell surface. We wanted to test if AGR2 is a cancer-specific tumor-associated antigen. We utilized two AGR2 antibodies, P3A5 and P1G4, for in vivo tumor localization and tumor growth inhibition. The monoclonal antibodies recognized both human AGR2 and mouse Agr2. Biodistribution experiments using a syngeneic mouse model showed high uptake of P3A5 AGR2 antibody in xenografted eAgr2⁺ pancreatic tumors, with limited uptake in normal tissues. In implanted human patient-derived eAGR2⁺ pancreatic cancer xenografts, tumor growth inhibition was evaluated with antibodies and Gemcitabine (Gem). Inhibition was more potent by P1G4 + Gem combination than Gem alone or P3A5 + Gem. We converted these two antibodies to human:mouse chimeric forms: the constructed P3A5 and P1G4 chimeric mV_LhC_κ and mV_HhC_γ (γ1, γ2, γ4) genes were inserted in a single mammalian expression plasmid vector, and transfected into human 293F cells. Expressed human:mouse chimeric IgG1, IgG2 and IgG4 antibodies retained AGR2 binding. Increase in IgG yield by transfected cells could be obtained with serial transfection of vectors with different drug resistance. These chimeric antibodies, when incubated with human blood, effectively lysed eAGR2⁺ PC3 prostate cancer cells. We have, thus, produced humanized anti-AGR2 antibodies that, after further testing, might be suitable for treatment against a variety of eAGR2⁺ solid tumors.