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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 tunicamycin treatment on the expression of COX-2 and GRP78 in HepG2 cells.HepG2 cells were treated with 3 µmol/L tunicamycin (TM) for 0 (control), 4 and 8 hr. Equal protein amounts of cell lysates were subjected to western blot assay using specific anti-COX-2 and anti-GRP78 antibody. β-actin in the same HepG2 cells extract was 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<0.01, ##P<0.01,compared with untreated HepG2 cells).
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pone-0062627-g004: Effect of tunicamycin treatment on the expression of COX-2 and GRP78 in HepG2 cells.HepG2 cells were treated with 3 µmol/L tunicamycin (TM) for 0 (control), 4 and 8 hr. Equal protein amounts of cell lysates were subjected to western blot assay using specific anti-COX-2 and anti-GRP78 antibody. β-actin in the same HepG2 cells extract was 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<0.01, ##P<0.01,compared with untreated HepG2 cells).

Mentions: To investigate the underlying mechanisms involved in the protection of HepG2 cells treated with tunicamycin against doxorubicin-induced apoptosis, alterations in the protein expression of COX-2 and GRP78 (a hallmark of ER stress) were determined through western blotting. As shown in Figure 4, administration of tunicamycin to HepG2 cells induced an early increase in GRP78 expression, which is indicative of ER stress. Simultaneously, the expression of COX-2 rapidly increased after treatment with tunicamycin. These data suggest that COX-2 may be directly involved in ER stress–induced resistance to doxorubicin.


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 tunicamycin treatment on the expression of COX-2 and GRP78 in HepG2 cells.HepG2 cells were treated with 3 µmol/L tunicamycin (TM) for 0 (control), 4 and 8 hr. Equal protein amounts of cell lysates were subjected to western blot assay using specific anti-COX-2 and anti-GRP78 antibody. β-actin in the same HepG2 cells extract was 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<0.01, ##P<0.01,compared with untreated HepG2 cells).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0062627-g004: Effect of tunicamycin treatment on the expression of COX-2 and GRP78 in HepG2 cells.HepG2 cells were treated with 3 µmol/L tunicamycin (TM) for 0 (control), 4 and 8 hr. Equal protein amounts of cell lysates were subjected to western blot assay using specific anti-COX-2 and anti-GRP78 antibody. β-actin in the same HepG2 cells extract was 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<0.01, ##P<0.01,compared with untreated HepG2 cells).
Mentions: To investigate the underlying mechanisms involved in the protection of HepG2 cells treated with tunicamycin against doxorubicin-induced apoptosis, alterations in the protein expression of COX-2 and GRP78 (a hallmark of ER stress) were determined through western blotting. As shown in Figure 4, administration of tunicamycin to HepG2 cells induced an early increase in GRP78 expression, which is indicative of ER stress. Simultaneously, the expression of COX-2 rapidly increased after treatment with tunicamycin. These data suggest that COX-2 may be directly involved in ER stress–induced resistance to doxorubicin.

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