Inhibition of endoplasmic-reticulum-stress-mediated autophagy enhances the effectiveness of chemotherapeutics on pancreatic cancer

Abstract

BackgroundEndoplasmic reticulum (ER) stress and its consequent unfolded protein response (UPR) are believed to be associated with progression, survival and chemoresistance of a variety of tumor cells through multiple cellular processes, including autophagy. Therefore, the ER stress-autophagy pathway presents a potential molecular target for therapeutic intervention. The objective of this study was to evaluate the therapeutic efficacy of ER stress and autophagy modulators in the context of pancreatic ductal adenocarcinoma (PDAC).MethodsWe first targeted IRE1α, an important regulator of the UPR, through STF-083010 treatment in PDAC cell lines in vitro. Chloroquine was then used to target autophagy and an optimal combination treatment was developed using chloroquine, sunitinib and gemcitabine. Apoptosis was analyzed using TUNEL assay, autophagy was estimated using lysotracker staining and electron microscopy, and UPR was analyzed using anti-GRP78 immunostaining and XBP1 splicing. Transplantation of PDAC derived KPCP1 and Panc02 cells in mouse pancreas were performed to study treatment efficacy in vivo.ResultsSuppression of the IRE1α by STF-083010 alone resulted in increased lysosomes and reduced viability of PDAC cells. Chloroquine treatment alone inhibited downstream autophagy but was insufficient in reducing PDAC cell growth. However, combining STF-083010 and chloroquine had additive anti-tumor efficacy when used with gemcitabine. Sunitinib alone caused abnormal maturation of the autolysosomes with increased intracellular multivesicular bodies and increased apoptosis evident in PDAC cells. Sunitinib showed a synergistic effect with chloroquine in reducing in vitro PDAC cell viability and significantly increased the efficacy of gemcitabine in human and murine PDAC cell lines. The anti-proliferative effect of gemcitabine was significantly increased when used in combination with sunitinib and/or chloroquine in both in vitro and in vivo PDAC models. The addition of sunitinib and/or chloroquine to gemcitabine, resulted in a significantly increased survival of the animals without noticeably increased toxicity. Sunitinib, gemcitabine and chloroquine treated mice showed a significant reduction of GRP78 expression, reduced cell proliferation and increased apoptosis in pancreas, compatible with a tumor response.ConclusionsSunitinib combined with chloroquine reduces tumor growth through suppression of autophagy and increased apoptosis. Co-administration of modulators of ER stress-mediated autophagy with chemotherapy presents a novel therapeutic approach in PDAC.Electronic supplementary materialThe online version of this article (10.1186/s12967-018-1562-z) contains supplementary material, which is available to authorized users.

PTBP3 promotes malignancy and hypoxia‐induced chemoresistance in pancreatic cancer cells by ATG12 up‐regulation

“…An association between hypoxia‐induced chemoresistance and autophagy is becoming increasingly apparent . Moreover, hypoxia‐associated genes and autophagy are implicated with a less favourable outcome in PDAC . PTBs are known to regulate gene expression by binding to hypoxia‐related transcripts ; therefore, we also studied the role of PTBP3 in the development of PDAC and therapeutic resistance in tumour tissue and in pancreatic cancer cell lines under hypoxic stress.…”

“…In agreement with our results, the anti‐proliferative effect of gemcitabine was significantly increased when autophagy was inhibited. Thakur et al found that the addition of sunitinib or chloroquine to gemcitabine significantly increased survival in an animal pancreatic cancer model without an increase in toxicity. The authors proposed that sunitinib and chloroquine can reduce tumour growth through the suppression of autophagy and increased apoptosis.…”

“…[34][35][36] Moreover, hypoxia-associated genes and autophagy are implicated with a less favourable outcome in PDAC. 37,38 PTBs are known to regulate gene expression by binding to hypoxia-related transcripts 20 ; therefore, we also studied the role of PTBP3 in the development of PDAC and therapeutic resistance in tumour tissue and in pancreatic cancer cell lines under hypoxic stress. In addition, we determined whether PTBP3 influenced the stress response against hypoxia and the cytotoxic effects of gemcitabine and investigated whether PTBP3 expression promoted the proliferation of PDAC cells and its direct influence on the expression of ATG12.…”

Long noncoding RNA growth arrest‐specific 5 facilitates glioma cell sensitivity to cisplatin by suppressing excessive autophagy in an mTOR‐dependent manner

“…6,7 Autophagy is a conserved physiological process that can maintain homeostasis by degrading damaged protein and organelles, which depends on the regulation of autophagy-related protein including microtubule-associated protein light chain 3 (LC3), Beclin 1, and p62. 6,7 Autophagy is a conserved physiological process that can maintain homeostasis by degrading damaged protein and organelles, which depends on the regulation of autophagy-related protein including microtubule-associated protein light chain 3 (LC3), Beclin 1, and p62.…”

“…For research on cancer chemotherapy, accumulating evidence has confirmed a paradoxical role of autophagy: it can act as a prosurvival or prodeath contributor to anticancer therapy. 6 Inconsequently, suppressing of autophagy enhances drug resistance in gastric cancer cells. 9 Analogously, targeting endoplasmic reticulum stress-mediated autophagy elevates the effectiveness of sunitinib and gemcitabine on pancreatic cancer.…”