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Combination therapy targeting ectopic ATP synthase and 26S proteasome induces ER stress in breast cancer cells.

Chang HY, Huang TC, Chen NN, Huang HC, Juan HF - Cell Death Dis (2014)

Bottom Line: We showed that citreoviridin triggered PERK-mediated eIF2α phosphorylation, which in turn attenuated general protein synthesis and led to cell cycle arrest in the G0/G1 phase.More interestingly, the combined treatment triggered lethality through unusual non-apoptotic caspase- and autophagy-independent cell death with a cytoplasmic vacuolization phenotype.The results imply that by boosting ER stress, the combination of ATP synthase inhibitor citreoviridin and 26S proteasome inhibitor bortezomib could potentially be an effective therapeutic strategy against breast cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Science, National Taiwan University, Taipei, Taiwan.

ABSTRACT
F1Fo ATP synthase is present in all organisms and is predominantly located on the inner membrane of mitochondria in eukaryotic cells. The present study demonstrated that ATP synthase and electron transport chain complexes were ectopically expressed on the surface of breast cancer cells and could serve as a potent anticancer target. We investigated the anticancer effects of the ATP synthase inhibitor citreoviridin on breast cancer cells through proteomic approaches and revealed that differentially expressed proteins in cell cycle regulation and in the unfolded protein response were functionally enriched. We showed that citreoviridin triggered PERK-mediated eIF2α phosphorylation, which in turn attenuated general protein synthesis and led to cell cycle arrest in the G0/G1 phase. We further showed that the combination of citreoviridin and the 26S proteasome inhibitor bortezomib could improve the anticancer activity by enhancing ER stress, by ameliorating citreoviridin-caused cyclin D3 compensation, and by contributing to CDK1 deactivation and PCNA downregulation. More interestingly, the combined treatment triggered lethality through unusual non-apoptotic caspase- and autophagy-independent cell death with a cytoplasmic vacuolization phenotype. The results imply that by boosting ER stress, the combination of ATP synthase inhibitor citreoviridin and 26S proteasome inhibitor bortezomib could potentially be an effective therapeutic strategy against breast cancer.

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Related in: MedlinePlus

Combination of bortezomib and citreoviridin inhibited cell cycle progression through different cell cycle regulators. Cells treated with or without 0.1 μM citreoviridin (Citreo) and 10 nM bortezomib (Btz) for 48 h were subjected to cell cycle analysis or harvested for western blotting analysis. Cell cycles distributed in the (a) G0/G1, (b) S, and (c) G2/M phases were quantified. *P-values of <0.01 show that treatment effects differed significantly from those on the DMSO control. (d) Protein expression levels of the cell cycle regulators and CKIs from cells treated for 48 h were normalized to actin and DMSO (−/−) levels. For the phosphorylated form of the indicated proteins, the level of phosphorylation was further normalized to the total level of the given protein
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fig6: Combination of bortezomib and citreoviridin inhibited cell cycle progression through different cell cycle regulators. Cells treated with or without 0.1 μM citreoviridin (Citreo) and 10 nM bortezomib (Btz) for 48 h were subjected to cell cycle analysis or harvested for western blotting analysis. Cell cycles distributed in the (a) G0/G1, (b) S, and (c) G2/M phases were quantified. *P-values of <0.01 show that treatment effects differed significantly from those on the DMSO control. (d) Protein expression levels of the cell cycle regulators and CKIs from cells treated for 48 h were normalized to actin and DMSO (−/−) levels. For the phosphorylated form of the indicated proteins, the level of phosphorylation was further normalized to the total level of the given protein

Mentions: Subsequently, we analyzed the effects of bortezomib and citreoviridin on cell cycle progression and found that the combined treatment caused elevated populations in both the G0/G1 and G2/M phases accompanied by a significant reduction in the S phase (Figures 6a–c). The cell cycle regulators phospho-Rb, CDK4, cyclin D1, phospho-CDK1, cyclin B1, Cdc25C, and proliferating cell nuclear antigen (PCNA) were inhibited by citreoviridin alone and in combination with bortezomib (Figure 6d). We also revealed that the combination of bortezomib and citreoviridin inhibited citreoviridin-induced compensation of cyclin D3 and CDK6, thus preventing Rb phosphorylation and S-phase entry by decreasing PCNA expression (Figure 6d). We moreover found that citreoviridin alone and in combination with bortezomib augmented only p21, whereas p53 and p27 were unaltered, showing that these two CKIs were not involved in citreoviridin- or bortezomib-induced cell cycle arrest (Figure 6d).


Combination therapy targeting ectopic ATP synthase and 26S proteasome induces ER stress in breast cancer cells.

Chang HY, Huang TC, Chen NN, Huang HC, Juan HF - Cell Death Dis (2014)

Combination of bortezomib and citreoviridin inhibited cell cycle progression through different cell cycle regulators. Cells treated with or without 0.1 μM citreoviridin (Citreo) and 10 nM bortezomib (Btz) for 48 h were subjected to cell cycle analysis or harvested for western blotting analysis. Cell cycles distributed in the (a) G0/G1, (b) S, and (c) G2/M phases were quantified. *P-values of <0.01 show that treatment effects differed significantly from those on the DMSO control. (d) Protein expression levels of the cell cycle regulators and CKIs from cells treated for 48 h were normalized to actin and DMSO (−/−) levels. For the phosphorylated form of the indicated proteins, the level of phosphorylation was further normalized to the total level of the given protein
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4260757&req=5

fig6: Combination of bortezomib and citreoviridin inhibited cell cycle progression through different cell cycle regulators. Cells treated with or without 0.1 μM citreoviridin (Citreo) and 10 nM bortezomib (Btz) for 48 h were subjected to cell cycle analysis or harvested for western blotting analysis. Cell cycles distributed in the (a) G0/G1, (b) S, and (c) G2/M phases were quantified. *P-values of <0.01 show that treatment effects differed significantly from those on the DMSO control. (d) Protein expression levels of the cell cycle regulators and CKIs from cells treated for 48 h were normalized to actin and DMSO (−/−) levels. For the phosphorylated form of the indicated proteins, the level of phosphorylation was further normalized to the total level of the given protein
Mentions: Subsequently, we analyzed the effects of bortezomib and citreoviridin on cell cycle progression and found that the combined treatment caused elevated populations in both the G0/G1 and G2/M phases accompanied by a significant reduction in the S phase (Figures 6a–c). The cell cycle regulators phospho-Rb, CDK4, cyclin D1, phospho-CDK1, cyclin B1, Cdc25C, and proliferating cell nuclear antigen (PCNA) were inhibited by citreoviridin alone and in combination with bortezomib (Figure 6d). We also revealed that the combination of bortezomib and citreoviridin inhibited citreoviridin-induced compensation of cyclin D3 and CDK6, thus preventing Rb phosphorylation and S-phase entry by decreasing PCNA expression (Figure 6d). We moreover found that citreoviridin alone and in combination with bortezomib augmented only p21, whereas p53 and p27 were unaltered, showing that these two CKIs were not involved in citreoviridin- or bortezomib-induced cell cycle arrest (Figure 6d).

Bottom Line: We showed that citreoviridin triggered PERK-mediated eIF2α phosphorylation, which in turn attenuated general protein synthesis and led to cell cycle arrest in the G0/G1 phase.More interestingly, the combined treatment triggered lethality through unusual non-apoptotic caspase- and autophagy-independent cell death with a cytoplasmic vacuolization phenotype.The results imply that by boosting ER stress, the combination of ATP synthase inhibitor citreoviridin and 26S proteasome inhibitor bortezomib could potentially be an effective therapeutic strategy against breast cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Science, National Taiwan University, Taipei, Taiwan.

ABSTRACT
F1Fo ATP synthase is present in all organisms and is predominantly located on the inner membrane of mitochondria in eukaryotic cells. The present study demonstrated that ATP synthase and electron transport chain complexes were ectopically expressed on the surface of breast cancer cells and could serve as a potent anticancer target. We investigated the anticancer effects of the ATP synthase inhibitor citreoviridin on breast cancer cells through proteomic approaches and revealed that differentially expressed proteins in cell cycle regulation and in the unfolded protein response were functionally enriched. We showed that citreoviridin triggered PERK-mediated eIF2α phosphorylation, which in turn attenuated general protein synthesis and led to cell cycle arrest in the G0/G1 phase. We further showed that the combination of citreoviridin and the 26S proteasome inhibitor bortezomib could improve the anticancer activity by enhancing ER stress, by ameliorating citreoviridin-caused cyclin D3 compensation, and by contributing to CDK1 deactivation and PCNA downregulation. More interestingly, the combined treatment triggered lethality through unusual non-apoptotic caspase- and autophagy-independent cell death with a cytoplasmic vacuolization phenotype. The results imply that by boosting ER stress, the combination of ATP synthase inhibitor citreoviridin and 26S proteasome inhibitor bortezomib could potentially be an effective therapeutic strategy against breast cancer.

Show MeSH
Related in: MedlinePlus