Pancreatic Cancer-Secreted Proteins: Targeting Their Functions in Tumor Microenvironment.

Pancreatic Ductal Adenocarcinoma (PDAC) is a ravaging disease with a poor prognosis, requiring a more detailed understanding of its biology to foster the development of effective therapies. The unsatisfactory results of treatments targeting cell proliferation and its related mechanisms suggest a shift in focus towards the inflammatory tumor microenvironment (TME). Here, we discuss the role of cancer-secreted proteins in the complex TME tumor-stroma crosstalk, shedding lights on druggable molecular targets for the development of innovative, safer and more efficient therapeutic strategies.

Pancreatic beta-cell specific BAG3 knockout results in chronic hyperinsulinemia inducing insulin resistance.

BACKGROUND: Insulin, secreted from pancreatic islets of Langerhans, is of critical importance in regulating glucose homeostasis. Defective insulin secretion and/or the inability of tissues to respond to insulin results in insulin resistance and to several metabolic and organ alterations. We have previously demonstrated that BAG3 regulates insulin secretion. Herein we explored the consequences of beta-cells specific BAG3 deficiency in an animal model. METHODS: We generated a beta-cells specific BAG3 knockout mouse model. Glucose and insulin tolerance tests, proteomics, metabolomics, and immunohistochemical analysis were used to investigate the role of BAG3 in regulating insulin secretion and the effects of chronic exposure to excessive insulin release in vivo. RESULTS: Beta-cells specific BAG3 knockout results in primary hyperinsulinism due to excessive insulin exocytosis finally leading to insulin resistance. We demonstrate that resistance is mainly muscle-dependent while the liver remains insulin sensitive. The chronically altered metabolic condition leads in time to histopathological alterations in different organs. We observe elevated glycogen and lipid accumulation in the liver reminiscent of non-alcoholic fatty liver disease as well as mesangial matrix expansion and thickening of the glomerular basement membrane, resembling the histology of chronic kidney disease. CONCLUSION: Altogether, this study shows that BAG3 plays a role in insulin secretion and provides a model for the study of hyperinsulinemia and insulin resistance.

Spike-mediated viral membrane fusion is inhibited by a specific anti-IFITM2 monoclonal antibody.

The early steps of viral infection involve protein complexes and structural lipid rearrangements which characterize the peculiar strategies of each virus to invade permissive host cells. Members of the human immune-related interferon-induced transmembrane (IFITM) protein family have been described as inhibitors of the entry of a broad range of viruses into the host cells. Recently, it has been shown that SARS-CoV-2 is able to hijack IFITM2 for efficient infection. Here, we report the characterization of a newly generated specific anti-IFITM2 mAb able to impair Spike-mediated internalization of SARS-CoV-2 in host cells and, consequently, to reduce the SARS-CoV-2 cytopathic effects and syncytia formation. Furthermore, the anti-IFITM2 mAb reduced HSVs- and RSV-dependent cytopathic effects, suggesting that the IFITM2-mediated mechanism of host cell invasion might be shared with other viruses besides SARS-CoV-2. These results show the specific role of IFITM2 in mediating viral entry into the host cell and its candidacy as a cell target for antiviral therapeutic strategies.

Proteomics Approach Highlights Early Changes in Human Fibroblasts-Pancreatic Ductal Adenocarcinoma Cells Crosstalk.

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer mortality worldwide. Non-specific symptoms, lack of biomarkers in the early stages, and drug resistance due to the presence of a dense fibrous stroma all contribute to the poor outcome of this disease. The extracellular matrix secreted by activated fibroblasts contributes to the desmoplastic tumor microenvironment formation. Given the importance of fibroblast activation in PDAC pathology, it is critical to recognize the mechanisms involved in the transformation of normal fibroblasts in the early stages of tumorigenesis. To this aim, we first identified the proteins released from the pancreatic cancer cell line MIA-PaCa2 by proteomic analysis of their conditioned medium (CM). Second, normal fibroblasts were treated with MIA-PaCa2 CM for 24 h and 48 h and their proteostatic changes were detected by proteomics. Pathway analysis indicated that treated fibroblasts undergo changes compatible with the activation of migration, vasculogenesis, cellular homeostasis and metabolism of amino acids and reduced apoptosis. These biological activities are possibly regulated by ITGB3 and TGFB1/2 followed by SMAD3, STAT3 and BAG3 activation. In conclusion, this study sheds light on the crosstalk between PDAC cells and associated fibroblasts. Data are available via ProteomeXchange with identifier PXD030974.

Concerted BAG3 and SIRPα blockade impairs pancreatic tumor growth.

The BAG3- and SIRPα- mediated pathways trigger distinct cellular targets and signaling mechanisms in pancreatic cancer microenvironment. To explore their functional connection, we investigated the effects of their combined blockade on cancer growth in orthotopic allografts of pancreatic cancer mt4-2D cells in immunocompetent mice. The anti-BAG3 + anti-SIRPα mAbs treatment inhibited (p = 0.007) tumor growth by about the 70%; also the number of metastatic lesions was decreased, mostly by the effect of the anti-BAG3 mAb. Fibrosis and the expression of the CAF activation marker α-SMA were reduced by about the 30% in animals treated with anti-BAG3 mAb compared to untreated animals, and appeared unaffected by treatment with the anti-SIRPα mAb alone; however, the addition of anti-SIRPα to anti-BAG3 mAb in the combined treatment resulted in a > 60% (p < 0.0001) reduction of the fibrotic area and a 70% (p < 0.0001) inhibition of CAF α-SMA positivity. Dendritic cells (DCs) and CD8+ lymphocytes, hardly detectable in the tumors of untreated animals, were modestly increased by single treatments, while were much more clearly observable (p < 0.0001) in the tumors of the animals subjected to the combined treatment. The effects of BAG3 and SIRPα blockade do not simply reflect the sum of the effects of the single blockades, indicating that the two pathways are connected by regulatory interactions and suggesting, as a proof of principle, the potential therapeutic efficacy of a combined BAG3 and SIRPα blockade in pancreatic cancer.

BAG3 induces α-SMA expression in human fibroblasts and its over-expression correlates with poorer survival in fibrotic cancer patients.

Hypoxia and angiogenesis in solid tumors are often strictly linked to the development of fibrotic tissues, a detrimental event that compromises the antitumor immunity. As a consequence, tumor aggressiveness and poor patient prognosis relate to higher incidence of tissue fibrosis and stromal stiffness. The molecular pathways through which normal fibroblasts are converted in cancer-associated fibroblasts (CAFs) have a central role in the onset of fibrosis in tumor stroma, thus emerging as a strategic target of novel therapeutic approaches for cancer disease. Several studies addressed the role of BAG3 in sustaining growth and survival of cancer cell and also shed light on the different mechanisms in which the intracellular protein is involved. More recently, new pieces of evidence revealed a pivotal role of extracellular BAG3 in pro-tumor cell signaling in the tumor microenvironment, as well as its involvement in the development of fibrosis in tumor tissues. Here we report further data showing the presence of the BAG3 receptor (Interferon-induced transmembrane protein [IFITM]-2) on the plasma membrane of normal dermal fibroblasts and the activity of BAG3 as a factor able to induce the expression of α-smooth muscle actin and the phosphorylation of AKT and focal adhesion kinase, that sustain CAF functions in tumor microenvironment. Furthermore, in agreement with these findings, bag3 gene expression has been analyzed by high throughput RNA sequencing databases from patients-derived xenografts. A strong correlation between bag3 gene expression and patients' survival was found in several types of fibrotic tumors. The results obtained provide encouraging data that identify BAG3 as a promising therapeutic target to counteract fibrosis in tumors.

An emerging role for BAG3 in gynaecological malignancies.

BAG3, a member of the BAG family of co-chaperones, is a multidomain protein with a role in several cellular processes, including the control of apoptosis, autophagy and cytoskeletal dynamics. The expression of bag3 is negligible in most cells but can be induced by stress stimuli or malignant transformation. In some tumours, BAG3 has been reported to promote cell survival and resistance to therapy. The expression of BAG3 has been documented in ovarian, endometrial and cervical cancers, and studies have revealed biochemical and functional connections of BAG3 with proteins involved in the survival, invasion and resistance to therapy of these malignancies. BAG3 expression has also been shown to correlate with the grade of dysplasia in squamous intraepithelial lesions of the uterine cervix. Some aspects of BAG3 activity, such as its biochemical and functional interaction with the human papillomavirus proteins, could help in our understanding of the mechanisms of oncogenesis induced by the virus. This review aims to highlight the potential value of BAG3 studies in the field of gynaecological tumours.

BAG3 in Tumor Resistance to Therapy.

BAG3 is highly expressed across cancer types and its intracellular activity is critical for cancer cell survival. However, recent findings suggest that BAG3 can also modulate the tumor microenvironment to promote cancer progression and resistance to therapies, suggesting new ways to target this protein in cancer therapy.

Diagnostic accuracy of p53 immunohistochemistry as surrogate of TP53 sequencing in endometrial cancer.

Aberrant p53 immunohistochemical expression is used to identify the copy-number-high/TP53-mutant subgroup of endometrial cancer (EC). We aimed to determine the diagnostic accuracy of p53 immunohistochemistry as surrogate for TP53 sequencing through a systematic review and meta-analysis. Electronic databases were searched from their inception to June 2019. All studies assessing p53 expression and TP53 mutations in EC were included. Diagnostic accuracy was assessed based on area under the curve (AUC). Immunohistochemical criteria used to define aberrant p53 expression were "overexpression" and "overexpression or complete absence". Subgroup analysis was based on the sequencing technique adopted (Polymerase Chain Reaction + sequencing, or next generation sequencing, NGS). Thirteen observational studies with 727 endometrial cancers were included. Both "overexpression" and "overexpression or complete absence" showed high diagnostic accuracy (AUC = 0.9088 and 0.9030, respectively). The subgroup with "overexpression" and NGS showed the best results, with very high diagnostic accuracy (AUC = 0.9927). In conclusion, immunohistochemistry for p53 is a highly accurate surrogate of TP53 sequencing. Overexpression of p53 in ≥70-80% showed the best accuracy in predicting TP53 mutations. Further studies in this field should adopt optimized immunohistochemical procedures and take into account less common p53 patterns (e.g. cytoplasmic expression).

The multiple activities of BAG3 protein: Mechanisms.

BACKGROUND: BAG3 was identified as a co-chaperone of the heat shock protein (Hsp) 70, which helps, through the binding to the ATPase domain, the ADP release from the chaperone and the nucleotide cycling. By interacting with Hsp70, BAG3 modulates the activities of this chaperone, including the delivery of client proteins to proteasome. BAG3 can also carry out Hsp70- independent functions, through its interactions with other proteins involved in apoptosis, cytoskeleton dynamics and other pathways. SCOPE OF REVIEW: Here we provide a summary of the main mechanisms which encompass BAG3 as an intracellular factor involved in different pathways which regulate and modulate the physiological cell response. Furthermore, it has been shown that BAG3 can be secreted by some cell types and is able to activate the monocytes through the binding on a membrane cell receptor, indicating that the protein can act like an alarmin with different functions inside and outside the cell. MAJOR CONCLUSIONS: Whereas intracellularly BAG3 sustains the levels of anti-apoptotic factors and other molecules, participates in protein quality control, drives the cytoskeleton dynamics, exerts structural and functional roles in myocytes, the discovery of a secreted BAG3 opened a new field of investigation in tumor development and progression, revealing its role in a new signaling pathway, mediated by the BAG3/BAG3R axis, which also includes monocytes and other stromal cells. GENERAL SIGNIFICANCE: BAG3 is a multifunctional protein that is involved cell stress response through its participation in several regulatory pathways which control cell homeostatic response in physiological and pathological conditions.

Development of an anti-BAG3 humanized antibody for treatment of pancreatic cancer.

We have previously shown that secreted BAG3 is a potential target for the treatment of pancreatic ductal adenocarcinoma and that pancreatic tumor growth and metastatic dissemination can be reduced by treatment with an anti-BAG3 murine antibody. Here, we used complementarity-determining region (CDR) grafting to generate a humanized version of the anti-BAG3 antibody that may be further developed for possible clinical use. We show that the humanized anti-BAG3 antibody, named BAG3-H2L4, abrogates BAG3 binding to macrophages and subsequent release of IL-6. Furthermore, it specifically localizes into tumor tissues and significantly inhibits the growth of Mia PaCa-2 pancreatic cancer cell xenografts. We propose BAG3-H2L4 antibody as a potential clinical candidate for BAG3-targeted therapy in pancreatic cancer.

Discovery and synthesis of the first selective BAG domain modulator of BAG3 as an attractive candidate for the development of a new class of chemotherapeutics.

BAG3 protein has emerged as a key regulator of important cellular processes and its expression is increased in some tumor types; however, despite its potential value for future chemotherapeutics, no selective BAG3 modulators have been yet reported. Here we report the 2,4-thiazolidinedione derivative 28 as the first BAG3 protein modulator.

Microbiota effects on cancer: from risks to therapies.

Gut microbiota, a group of 1014 bacteria, eukaryotes and virus living in gastrointestinal tract, is crucial for many physiological processes in particular plays an important role in inflammatory and immune reactions. Several internal and external factors can influence this population, and shifts in their composition, have been demonstrated to contribute and affect different diseases. During dysbiosis several bacteria related to inflammation, one of the most necessary factors in carcinogenesis; it has been shown that some bacterial strains through deregulation of different signals/pathways may affect tumor development through the production of many factors. Gut microbiota might be considered as a holistic hub point for cancer development: direct and indirect involvements have been studying in several neoplasms such as colon rectal cancer, hepatocellular carcinoma and breast cancer. This review discuss over the evidence of crosstalk between gut microbiota and cancer, its ability to modulate chemotherapy, radiotherapy and immunotherapy, and the possibility that the intestinal microbial is a new target for therapeutic approaches to improve the prognosis and quality of life of cancer patients.