Calreticulin promotes EMT in pancreatic cancer via mediating Ca2+ dependent acute and chronic endoplasmic reticulum stress

Abstract

Background: Our previous study showed that calreticulin (CRT) promoted EGF-induced epithelial-mesenchymal transition (EMT) in pancreatic cancer (PC) via Integrin/EGFR-ERK/MAPK signaling. We next investigated the novel signal pathway and molecular mechanism involving the oncogenic role of CRT in PC. Methods: We investigated the potential role and mechanism of CRT in regulating intracellular free Ca2+ dependent acute and chronic endoplasmic reticulum stress (ERS)-induced EMT in PC in vitro and vivo.Results: Thapsigargin (TG) induced acute ERS via increasing intracellular free Ca2+ in PC cells, which was reversed by CRT silencing. Additionally, CRT silencing inhibited TG-induced EMT in vitro by reversing TG-induced changes of the key proteins in EMT signaling (ZO-1, E-cadherin and Slug) and ERK/MAPK signaling (pERK). TG-promoted cell invasion and migration was also rescued by CRT silencing but enhanced by IRE1α silencing (one of the key stressors in unfolded protein response). Meanwhile, CRT was co-immunoprecipitated and co-localized with IRE1α in vitro and its silencing led to the chronic ERS via upregulating IRE1α independent of IRE1-XBP1 axis. Moreover, CRT silencing inhibited IRE1α silencing-promoted EMT, including inhibiting the activation of EMT and ERK/MAPK signaling and the promotion of cell mobility. In vivo, CRT silencing decreased subcutaneous tumor size and distant liver metastasis following with the increase of IRE1α expression. A negative relationship between CRT and IRE1α was also observed in clinical PC samples, which coordinately promoted the advanced clinical stages and poor prognosis of PC patients. Conclusions: CRT promotes EMT in PC via mediating intracellular free Ca2+ dependent TG-induced acute ERS and IRE1α-mediated chronic ERS via Slug and ERK/MAPK signaling.

Identification of an IRES within the coding region of the structural protein of human rhinovirus 16

“…Therefore, we hypothesized that the IRES sequence was located at the full‐length sequence (nt 1982‐nt 2281) in the VP3 gene (Figure 2E). We also confirmed that IRES activity could be increased under ER stress induced by TG as reported previously 26,31 (Figure 3). Finally, we verified that the IRES (nt 1982‐nt 2281) initiated the translation of GFP in a cap‐independent manner (Figure 4A).…”

Down-regulation of MSMO1 promotes the development and progression of pancreatic cancer

“…Epithelial-mesenchymal transition (EMT) is a cellular process initiated from cellular micro environment following the acquisition of mesenchymal phenotypes and the repression of epithelial features, which finally contributes to the cell invasion and metastasis of cancer, including PC [4,5]. The key characteristic of EMT is the deficiency of epithelial markers, such as E-cadherin and the gain of interstitial markers, such as Vimentin and MMPs [6]. Increasing evidence confirms the significant role of PI3K-AKT-mTOR signaling pathway and it's downstream targets (p-AKT, p-PI3K and p-mTOR) in regulating EMT process [7,8].…”

Procyanidin B2 Alleviates Palmitic Acid-Induced Injury in HepG2 Cells via Endoplasmic Reticulum Stress Pathway

“…Yogalakshmi et al showed that PCB2 restrained ERS by downregulating mRNA levels of PERK, IRE1α, and ATF-6 and protein levels of eIF2α and XBP1 in high-calorie diet-fed rats [33]. Furthermore, we used 4-PBA and TG, the ER stress inhibitor and agonist, respectively [34,35], to assess the protective role of PCB2 in the context of PA-induced injury in HepG2 cells, indicating that ERS-dependent prevention could be involved in its protective effects. Previous and current experiments have confirmed the anti-ERS effects of PCB2 at multiple levels.…”