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Modulation of the unfolded protein response impedes tumor cell adaptation to proteotoxic stress: a PERK for hepatocellular carcinoma therapy.

Vandewynckel YP, Laukens D, Bogaerts E, Paridaens A, Van den Bussche A, Verhelst X, Van Steenkiste C, Descamps B, Vanhove C, Libbrecht L, De Rycke R, Lambrecht BN, Geerts A, Janssens S, Van Vlierberghe H - Hepatol Int (2014)

Bottom Line: Consistent with the UPR activation, electron microscopy demonstrated ER expansion and reorganization in HCC cells in vivo.Strikingly, under ER stress or hypoxia, the Perk inhibitor and not the Ire1 inhibitor reduced cell viability and proliferation via escalating proteotoxic stress in vitro.We provide the first evaluation of the UPR dynamics in a long-term cancer model and identified a small molecule inhibitor of Perk as a promising strategy for HCC therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.

ABSTRACT

Background: Functional disturbances of the endoplasmic reticulum (ER) lead to activation of the unfolded protein response (UPR), which is involved in the consecutive steps of carcinogenesis. In human hepatocellular carcinoma (HCC), the UPR is shown to be activated; however, little is known about the UPR kinetics and effects of UPR modulation in HCC.

Methods: We sequentially monitored the UPR over time in an orthotopic mouse model for HCC and explored the effects of UPR modulation on cell viability and proliferation in vitro and in the mouse model.

Results: The expression of ER-resident chaperones peaked during tumor initiation and increased further during tumor progression, predominantly within the nodules. A peak in Ire1 signaling was observed during tumor initiation. The Perk pathway was activated during tumor progression, and the proapoptotic target Chop was upregulated from week 5 and continued to rise, especially in the tumors. The Atf6 pathway was modestly activated only after tumor initiation. Consistent with the UPR activation, electron microscopy demonstrated ER expansion and reorganization in HCC cells in vivo. Strikingly, under ER stress or hypoxia, the Perk inhibitor and not the Ire1 inhibitor reduced cell viability and proliferation via escalating proteotoxic stress in vitro. Notably, the Perk inhibitor significantly decreased tumor burden in the mouse model.

Conclusion: We provide the first evaluation of the UPR dynamics in a long-term cancer model and identified a small molecule inhibitor of Perk as a promising strategy for HCC therapy.

No MeSH data available.


Related in: MedlinePlus

Effect of salubrinal, PERK or IRE1 inhibitor on the UPR and cell viability in HepG2 cells. Cells were subjected to hypoxia or tunicamycin as indicated for 48 h. a Effect on UPR marker mRNA expression by a PERK inhibitor and by an IRE1 inhibitor compared with solvent-treated cells under the same condition. b Immunoblotting for UPR markers. c Cell viability of HepG2 cells was assessed by a WST-1 assay. d Caspase-3 activity of HepG2 cells treated with the indicated compounds. These experiments were repeated six times with similar results. *p < 0.05, ***p < 0.001
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Fig4: Effect of salubrinal, PERK or IRE1 inhibitor on the UPR and cell viability in HepG2 cells. Cells were subjected to hypoxia or tunicamycin as indicated for 48 h. a Effect on UPR marker mRNA expression by a PERK inhibitor and by an IRE1 inhibitor compared with solvent-treated cells under the same condition. b Immunoblotting for UPR markers. c Cell viability of HepG2 cells was assessed by a WST-1 assay. d Caspase-3 activity of HepG2 cells treated with the indicated compounds. These experiments were repeated six times with similar results. *p < 0.05, ***p < 0.001

Mentions: To address whether interfering with the UPR affects tumor growth, we first validated the effect of the PERK inhibitor (PERKi) and IRE1 inhibitor on HepG2 cells under hypoxia and in the presence of tunicamycin-induced ER stress. The expression of ER stress markers was induced by tunicamycin and hypoxia (Fig. 4b).Fig. 4


Modulation of the unfolded protein response impedes tumor cell adaptation to proteotoxic stress: a PERK for hepatocellular carcinoma therapy.

Vandewynckel YP, Laukens D, Bogaerts E, Paridaens A, Van den Bussche A, Verhelst X, Van Steenkiste C, Descamps B, Vanhove C, Libbrecht L, De Rycke R, Lambrecht BN, Geerts A, Janssens S, Van Vlierberghe H - Hepatol Int (2014)

Effect of salubrinal, PERK or IRE1 inhibitor on the UPR and cell viability in HepG2 cells. Cells were subjected to hypoxia or tunicamycin as indicated for 48 h. a Effect on UPR marker mRNA expression by a PERK inhibitor and by an IRE1 inhibitor compared with solvent-treated cells under the same condition. b Immunoblotting for UPR markers. c Cell viability of HepG2 cells was assessed by a WST-1 assay. d Caspase-3 activity of HepG2 cells treated with the indicated compounds. These experiments were repeated six times with similar results. *p < 0.05, ***p < 0.001
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Related In: Results  -  Collection

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Fig4: Effect of salubrinal, PERK or IRE1 inhibitor on the UPR and cell viability in HepG2 cells. Cells were subjected to hypoxia or tunicamycin as indicated for 48 h. a Effect on UPR marker mRNA expression by a PERK inhibitor and by an IRE1 inhibitor compared with solvent-treated cells under the same condition. b Immunoblotting for UPR markers. c Cell viability of HepG2 cells was assessed by a WST-1 assay. d Caspase-3 activity of HepG2 cells treated with the indicated compounds. These experiments were repeated six times with similar results. *p < 0.05, ***p < 0.001
Mentions: To address whether interfering with the UPR affects tumor growth, we first validated the effect of the PERK inhibitor (PERKi) and IRE1 inhibitor on HepG2 cells under hypoxia and in the presence of tunicamycin-induced ER stress. The expression of ER stress markers was induced by tunicamycin and hypoxia (Fig. 4b).Fig. 4

Bottom Line: Consistent with the UPR activation, electron microscopy demonstrated ER expansion and reorganization in HCC cells in vivo.Strikingly, under ER stress or hypoxia, the Perk inhibitor and not the Ire1 inhibitor reduced cell viability and proliferation via escalating proteotoxic stress in vitro.We provide the first evaluation of the UPR dynamics in a long-term cancer model and identified a small molecule inhibitor of Perk as a promising strategy for HCC therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.

ABSTRACT

Background: Functional disturbances of the endoplasmic reticulum (ER) lead to activation of the unfolded protein response (UPR), which is involved in the consecutive steps of carcinogenesis. In human hepatocellular carcinoma (HCC), the UPR is shown to be activated; however, little is known about the UPR kinetics and effects of UPR modulation in HCC.

Methods: We sequentially monitored the UPR over time in an orthotopic mouse model for HCC and explored the effects of UPR modulation on cell viability and proliferation in vitro and in the mouse model.

Results: The expression of ER-resident chaperones peaked during tumor initiation and increased further during tumor progression, predominantly within the nodules. A peak in Ire1 signaling was observed during tumor initiation. The Perk pathway was activated during tumor progression, and the proapoptotic target Chop was upregulated from week 5 and continued to rise, especially in the tumors. The Atf6 pathway was modestly activated only after tumor initiation. Consistent with the UPR activation, electron microscopy demonstrated ER expansion and reorganization in HCC cells in vivo. Strikingly, under ER stress or hypoxia, the Perk inhibitor and not the Ire1 inhibitor reduced cell viability and proliferation via escalating proteotoxic stress in vitro. Notably, the Perk inhibitor significantly decreased tumor burden in the mouse model.

Conclusion: We provide the first evaluation of the UPR dynamics in a long-term cancer model and identified a small molecule inhibitor of Perk as a promising strategy for HCC therapy.

No MeSH data available.


Related in: MedlinePlus