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Endoplasmic reticulum stress-induced resistance to doxorubicin is reversed by paeonol treatment in human hepatocellular carcinoma cells.

Fan L, Song B, Sun G, Ma T, Zhong F, Wei W - PLoS ONE (2013)

Bottom Line: Interestingly, co-pretreatment with tunicamycin and Pae significantly increased apoptosis induced by doxorubicin.Furthermore, induction of ER stress resulted in increasing expression of COX-2 concomitant with inactivation of Akt and up-regulation of the pro-apoptotic transcription factor CHOP (GADD153) in HepG2 cells.However, co-pretreatment with tunicamycin and Pae decreased the expression of COX-2 and levels of activation of Akt as well as increasing the levels of CHOP in HCC cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncology, The First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China.

ABSTRACT

Background: Endoplasmic reticulum stress (ER stress) is generally activated in solid tumors and results in tumor cell anti-apoptosis and drug resistance. Paeonol (Pae, 2-hydroxy-4-methoxyacetophenone), is a natural product extracted from the root of Paeonia Suffruticosa Andrew. Although Pae displays anti-neoplastic activity and increases the efficacy of chemotherapeutic drugs in various cell lines and in animal models, studies related to the effect of Pae on ER stress-induced resistance to chemotherapeutic agents in hepatocellular carcinoma (HCC) are poorly understood.

Methodology/principal findings: In this study, we investigated the effect of the endoplasmic reticulum (ER) stress response during resistance of human hepatocellular carcinoma cells to doxorubicin. Treatment with the ER stress-inducer tunicamycin (TM) before the addition of doxorubicin reduced the rate of apoptosis induced by doxorubicin. Interestingly, co-pretreatment with tunicamycin and Pae significantly increased apoptosis induced by doxorubicin. Furthermore, induction of ER stress resulted in increasing expression of COX-2 concomitant with inactivation of Akt and up-regulation of the pro-apoptotic transcription factor CHOP (GADD153) in HepG2 cells. These cellular changes in gene expression and Akt activation may be an important resistance mechanism against doxorubicin in hepatocellular carcinoma cells undergoing ER stress. However, co-pretreatment with tunicamycin and Pae decreased the expression of COX-2 and levels of activation of Akt as well as increasing the levels of CHOP in HCC cells.

Conclusions/significance: Our results demonstrate that Pae reverses ER stress-induced resistance to doxorubicin in human hepatocellular carcinoma cells by targeting COX-2 mediated inactivation of PI3K/AKT/CHOP.

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Related in: MedlinePlus

Effect of co-treatment with tunicamycin and celecoxib/LY294002 on the expression of phospho (p)-Akt and CHOP in HepG2 cells.HepG2 cells were treated with 3 µmol/L tunicamycin in either the absence (control) or the presence of celecoxib(A)(50 µmol/L)/LY294002(B) (30 µmol/L) for 8 hr. Equal amounts of cell lysates were subjected to western blot analysis using specific anti-COX-2, anti-p-AKT, anti-AKT and anti-CHOP antibody. β-actin in the same HepG2 cells extract was used as an internal used as an internal reference. Optical density reading values of the specific protein versus the loading control protein β-actin are represented as fold of the control values. (*P<0.05, **P<0.01, compared with untreated HepG2 cells, #P<0.05, ##P<0.01, compared with HepG2 cells treated with tunicamycin alone).
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pone-0062627-g008: Effect of co-treatment with tunicamycin and celecoxib/LY294002 on the expression of phospho (p)-Akt and CHOP in HepG2 cells.HepG2 cells were treated with 3 µmol/L tunicamycin in either the absence (control) or the presence of celecoxib(A)(50 µmol/L)/LY294002(B) (30 µmol/L) for 8 hr. Equal amounts of cell lysates were subjected to western blot analysis using specific anti-COX-2, anti-p-AKT, anti-AKT and anti-CHOP antibody. β-actin in the same HepG2 cells extract was used as an internal used as an internal reference. Optical density reading values of the specific protein versus the loading control protein β-actin are represented as fold of the control values. (*P<0.05, **P<0.01, compared with untreated HepG2 cells, #P<0.05, ##P<0.01, compared with HepG2 cells treated with tunicamycin alone).

Mentions: To elucidate which signaling pathway is involved in COX-2 mediated cytoprotective function of ER stress, the activation status of the PI3K/Akt survival pathway was monitored in HepG2 cells before and after treatment with celecoxib in the presence of tunicamycin. As shown in Figure 8A, exposure to TM increases activation (phosphorylation) of Akt, whereas celecoxib inhibited TM-induced activation of Akt. Furthermore, HepG2 cells treated with the PI3K inhibitor, LY294002, in the presence of TM increased the expression of CHOP protein. (Figure 8B), These results suggest that the PI3K/AKT/CHOP pathway is important in the COX-2 mediated cytoprotective function of ER stress against doxorubicin-induced hepatocellular carcinoma cells apoptosis.


Endoplasmic reticulum stress-induced resistance to doxorubicin is reversed by paeonol treatment in human hepatocellular carcinoma cells.

Fan L, Song B, Sun G, Ma T, Zhong F, Wei W - PLoS ONE (2013)

Effect of co-treatment with tunicamycin and celecoxib/LY294002 on the expression of phospho (p)-Akt and CHOP in HepG2 cells.HepG2 cells were treated with 3 µmol/L tunicamycin in either the absence (control) or the presence of celecoxib(A)(50 µmol/L)/LY294002(B) (30 µmol/L) for 8 hr. Equal amounts of cell lysates were subjected to western blot analysis using specific anti-COX-2, anti-p-AKT, anti-AKT and anti-CHOP antibody. β-actin in the same HepG2 cells extract was used as an internal used as an internal reference. Optical density reading values of the specific protein versus the loading control protein β-actin are represented as fold of the control values. (*P<0.05, **P<0.01, compared with untreated HepG2 cells, #P<0.05, ##P<0.01, compared with HepG2 cells treated with tunicamycin alone).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3643935&req=5

pone-0062627-g008: Effect of co-treatment with tunicamycin and celecoxib/LY294002 on the expression of phospho (p)-Akt and CHOP in HepG2 cells.HepG2 cells were treated with 3 µmol/L tunicamycin in either the absence (control) or the presence of celecoxib(A)(50 µmol/L)/LY294002(B) (30 µmol/L) for 8 hr. Equal amounts of cell lysates were subjected to western blot analysis using specific anti-COX-2, anti-p-AKT, anti-AKT and anti-CHOP antibody. β-actin in the same HepG2 cells extract was used as an internal used as an internal reference. Optical density reading values of the specific protein versus the loading control protein β-actin are represented as fold of the control values. (*P<0.05, **P<0.01, compared with untreated HepG2 cells, #P<0.05, ##P<0.01, compared with HepG2 cells treated with tunicamycin alone).
Mentions: To elucidate which signaling pathway is involved in COX-2 mediated cytoprotective function of ER stress, the activation status of the PI3K/Akt survival pathway was monitored in HepG2 cells before and after treatment with celecoxib in the presence of tunicamycin. As shown in Figure 8A, exposure to TM increases activation (phosphorylation) of Akt, whereas celecoxib inhibited TM-induced activation of Akt. Furthermore, HepG2 cells treated with the PI3K inhibitor, LY294002, in the presence of TM increased the expression of CHOP protein. (Figure 8B), These results suggest that the PI3K/AKT/CHOP pathway is important in the COX-2 mediated cytoprotective function of ER stress against doxorubicin-induced hepatocellular carcinoma cells apoptosis.

Bottom Line: Interestingly, co-pretreatment with tunicamycin and Pae significantly increased apoptosis induced by doxorubicin.Furthermore, induction of ER stress resulted in increasing expression of COX-2 concomitant with inactivation of Akt and up-regulation of the pro-apoptotic transcription factor CHOP (GADD153) in HepG2 cells.However, co-pretreatment with tunicamycin and Pae decreased the expression of COX-2 and levels of activation of Akt as well as increasing the levels of CHOP in HCC cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncology, The First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China.

ABSTRACT

Background: Endoplasmic reticulum stress (ER stress) is generally activated in solid tumors and results in tumor cell anti-apoptosis and drug resistance. Paeonol (Pae, 2-hydroxy-4-methoxyacetophenone), is a natural product extracted from the root of Paeonia Suffruticosa Andrew. Although Pae displays anti-neoplastic activity and increases the efficacy of chemotherapeutic drugs in various cell lines and in animal models, studies related to the effect of Pae on ER stress-induced resistance to chemotherapeutic agents in hepatocellular carcinoma (HCC) are poorly understood.

Methodology/principal findings: In this study, we investigated the effect of the endoplasmic reticulum (ER) stress response during resistance of human hepatocellular carcinoma cells to doxorubicin. Treatment with the ER stress-inducer tunicamycin (TM) before the addition of doxorubicin reduced the rate of apoptosis induced by doxorubicin. Interestingly, co-pretreatment with tunicamycin and Pae significantly increased apoptosis induced by doxorubicin. Furthermore, induction of ER stress resulted in increasing expression of COX-2 concomitant with inactivation of Akt and up-regulation of the pro-apoptotic transcription factor CHOP (GADD153) in HepG2 cells. These cellular changes in gene expression and Akt activation may be an important resistance mechanism against doxorubicin in hepatocellular carcinoma cells undergoing ER stress. However, co-pretreatment with tunicamycin and Pae decreased the expression of COX-2 and levels of activation of Akt as well as increasing the levels of CHOP in HCC cells.

Conclusions/significance: Our results demonstrate that Pae reverses ER stress-induced resistance to doxorubicin in human hepatocellular carcinoma cells by targeting COX-2 mediated inactivation of PI3K/AKT/CHOP.

Show MeSH
Related in: MedlinePlus