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

Abstract

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-KrasG12D;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-KrasG12D;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.

The role of protein disulphide isomerase AGR2 in the tumour niche

“…In pancreatic cancer, it has been reported that AGR2 up‐regulates during inflammatory phase of pancreatic ductal adenocarcinoma (PDAC) development [Dumartin et al., ] and that ER stress induced by AGR2 is associated with the acquisition of a pro‐inflammatory phenotype. Furthermore, ER stress could be the mediator of an intercellular communication between epithelial and stromal cells [Dumartin et al., ].…”

“…In pancreatic cancer, it has been reported that AGR2 up‐regulates during inflammatory phase of pancreatic ductal adenocarcinoma (PDAC) development [Dumartin et al., ] and that ER stress induced by AGR2 is associated with the acquisition of a pro‐inflammatory phenotype. Furthermore, ER stress could be the mediator of an intercellular communication between epithelial and stromal cells [Dumartin et al., ]. It is possible that paracrine mediators, including inflammatory mediators such as reactive oxygen species, are involved in the intercellular communication between ER stress and AGR2 expression; however, this hypothesis remains to be addressed further.…”

“…Clinical studies have shown that elevated expression of AGR2 predicted an unfavourable prognosis in breast cancer patients and mediated tamoxifen drug resistance as an oestrogen agonist [Hrstka et al., ; Hengel et al., ]. AGR2 could activate ER stress response genes [Dumartin et al., ] to stimulate cell proliferation of AGR2‐negative pancreatic tumour cells and to enhance drug resistance [Ramachandran et al., ]. Based on this, the development of anti‐oestrogen resistance in many tumours seriously limits the curative effect of fulvestrant chemotherapy.…”

Stressed Out - Therapeutic Implications of ER Stress Related Cancer Research

“…Additionally, once activated, the pro-survival XBP1 was noted to be activated for a longer time period in cancer cells when compared to normal cells[39]. As well as adapting to chronic ER stress, it has been recently postulated that anterior-gradient 2 (AGR2) may contribute to the initiation and development of PDAC[40]. As AGR2 is a gene associated with protein folding and maturation which is expressed in pancreatic cells under ER stress conditions, it may become a key piece in our understanding of how PDACs arise, as well as a potential future therapeutic target.…”

Cancer Manipulation of Host Physiology: Lessons from Pancreatic Cancer

“…Disruption of autophagy via genetic deletion of its key mediator autophagy related 5 (ATG5) in mice led to increased levels of reactive oxygen species, augmented endoplasmic reticulum (ER) stress, and development of spontaneous chronic atrophic pancreatitis [79]. Conceivably, autophagy appears to limit ER stress and pro-tumorigenic mediators, and protect during incipient pancreatic oncogenesis [80, 81]. …”