BAG3 induces fibroblasts to release key cytokines involved in pancreatic cell migration

Abstract

Pancreatic ductal adenoma carcinoma (PDAC) is considered one of the deadliest solid cancers as it is usually diagnosed in advanced stages and has a poor response to treatment. The enormous effort made in the last 2 decades in the oncology field has not led to significant progress in improving early diagnosis or therapy for PDAC. The stroma of PDAC plays an active role in tumour initiation and progression and includes immune cells and stromal cells. We previously reported that Bcl2‐associated athanogene (BAG3) secreted by PDAC cells activates tumour‐associated macrophages to promote tumour growth. The disruption of this tumour–stroma axis by the anti‐BAG3 H2L4 therapeutic antibody is sufficient to delay tumour growth and limit metastatic spreading in different PDAC preclinical models. In the present study, we examined the role of BAG3 to activate human fibroblasts (HF) in releasing cytokines capable of supporting tumour progression. Treatment of fibroblasts with recombinant BAG3 induced important changes in the organisation of the cytoskeleton of these cells and stimulated the production of interleukin‐6, monocyte chemoattractant protein‐1/C–C motif chemokine ligand 2, and hepatocyte growth factor. Specifically, we observed that BAG3 triggered a depolymerisation of microtubules at the periphery of the cell while they were conserved in the perinuclear area. Conversely, the vimentin‐based intermediate filaments increased and spread to the edges of the cells. Finally, the conditioned medium (CM) collected from BAG3‐treated HF promoted the survival, proliferation, and migration of the PDAC cells. Blocking of the PDAC‐fibroblast axis by the H2L4 therapeutic anti‐BAG3 antibody, resulted in inhibition of cytokine release and, consequently, the inhibition of the migratory phenotype conferred by the CM to PDAC cells.

Corelating the molecular structure of BAG3 to its oncogenic role

“…It has also been demonstrated recently that BAG3 positive pancreatic stellate cells (PSC) stimulate the release of cytokines such as IL-8, MCP1, TGF-β2, IL-6 that act in a paracrine (on PDAC's) and autocrine manner (on PSC) to alter tumour microenvironment and drive invasiveness and metastasis of pancreatic adenocarcinoma (PDAC) (Yuan et al, 2019). BAG3 also stimulates the secretion of IL-6, chemokine ligand 2 and monocyte chemokine attractant protein from human fibroblasts (HF) present in tumour microenvironment that contributes further to diminished prognosis (Dufrusine et al, 2022). (Stürner & Behl, 2017).…”

“…BAG3, particularly its WW domain, has also been found to interact with repressors of the Hippo pathway, leading to the liberation of coactivators in the nucleus (Klimek et al, 2019). Encouraging tumour microenvironment cross‐talk: Recent research has suggested that BAG3 encourages the secretion of proinflammatory cytokines such as IL‐6, IL‐8 and CSF by macrophages, stellate cells and human fibroblasts present in the tumour‐microenvironment (Avinery et al, 2022; Dufrusine et al, 2022; Mantovani et al, 2008; Yuan et al, 2019). These cytokines activate proproliferative, prometastatic pathways, drive further infiltration of macrophages and other cell types and confer chemoresistance thereby contributing to further tumour progression (Rosati et al, 2015).…”

“…BAG3 can also bind to SH3 domain containing MIA (Melanoma Inhibitory Protein) through its PXXP motif to enhance cell‐survival by impeding apoptotic pathway. Secreted form of BAG3 has been shown to initiate secretion of cytokines such as IL‐8, IL‐6 in the tumour microenvironment by binding to cell‐surface receptors (Dufrusine et al, 2022). While some of the receptors and cytokines being secreted as a result of binding have been discovered, there lies additional scope for discovery of more pathways followed by BAG3 to initiate secretion of proinflammatory cytokines.…”

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

“…Furthermore, a distinct function was described for secreted BAG3. Indeed, its interaction with IFITM2 (Interferon Induced Transmembrane Protein 2) on the plasma membrane can induce pro-tumoral cytokine release by macrophages [61] and fibroblasts [62], thus sustaining tumor growth. Another relevant protein in this context is the soluble GSTP1 (Glutathione S-Transferase Pi 1), able to catalyze the conjugation of many hydrophobic and electrophilic compounds with reduced glutathione.…”

Iron Dyshomeostasis in COVID-19: Biomarkers Reveal a Functional Link to 5-Lipoxygenase Activation

“…PBMCs were lysed for Western blot analysis, as previously described [178]. Cellular protein amount was determined using the Bradford assay (Bio-Rad, Hercules, CA, USA); cell lysates were denatured in 5X Laemmli sample buffer at 98 • C for 10 min and equal amounts of proteins were separated using 12, 10, or 8% SDS-PAGE and transferred to a PVDF membrane (Merck Millipore, Darmstadt, Germany).…”