γ-Tocotrienol-induced endoplasmic reticulum stress and autophagy act concurrently to promote breast cancer cell death

2015 ◽  
Vol 93 (4) ◽  
pp. 306-320 ◽  
Author(s):  
Roshan V. Tiwari ◽  
Parash Parajuli ◽  
Paul W. Sylvester

The anticancer effects of γ-tocotrienol are associated with the induction of autophagy and endoplasmic reticulum (ER) stress-mediated apoptosis, but a direct relationship between these events has not been established. Treatment with 40 μmol/L of γ-tocotrienol caused a time-dependent decrease in cancer cell viability that corresponds to a concurrent increase in autophagic and endoplasmic reticulum (ER) stress markers in MCF-7 and MDA-MB-231 human breast cancer cells. γ-Tocotrienol treatment was found to cause a time-dependent increase in early phase (Beclin-1, LC3B-II) and late phase (LAMP-1 and cathepsin-D) autophagy markers, and pretreatment with autophagy inhibitors Beclin-1 siRNA, 3-MA or Baf1 blocked these effects. Furthermore, blockage of γ-tocotrienol-induced autophagy with Beclin-1 siRNA, 3-MA, or Baf1 induced a modest, but significant, reduction in γ-tocotrienol-induced cytotoxicity. γ-Tocotrienol treatment was also found to cause a decrease in mitogenic Erk1/2 signaling, an increase in stress-dependent p38 and JNK1/2 signaling, as well as an increase in ER stress apoptotic markers, including phospho-PERK, phospho-eIF2α, Bip, IRE1α, ATF-4, CHOP, and TRB3. In summary, these finding demonstrate that γ-tocotrienol-induced ER stress and autophagy occur concurrently, and together act to promote human breast cancer cell death.

2016 ◽  
Vol 82 ◽  
pp. 671-677 ◽  
Author(s):  
Fernanda Van Petten Vasconcelos Azevedo ◽  
Daiana Silva Lopes ◽  
Sarah Natalie Cirilo Gimenes ◽  
David Collares Achê ◽  
Lara Vecchi ◽  
...  

2016 ◽  
Vol 15 (4) ◽  
pp. NP44-NP52 ◽  
Author(s):  
Thamizhiniyan Venkatesan ◽  
Min-Ji Jeong ◽  
Young-Woong Choi ◽  
Eun-Jin Park ◽  
Samy Korany El-Desouky ◽  
...  

Although current chemotherapeutic agents are active at the beginning of therapy, the most common risk is the development of resistance during later stages in almost all cancer types including breast cancer. Hence, investigation of novel drugs is still a priority goal for cancer treatment. The objective of the present study is to investigate the anticancer effect of a derivative of stilbene, deoxyrhapontigenin (DR) isolated from Rheum undulatum L. root extracts against the chemoresistant MCF-7/adr and its parental MCF-7 human breast cancer cells. The morphological images indicate that DR induces an extensive cytoplasmic vacuolation in breast cancer cells. Mechanistic investigations revealed that DR treatment causes endoplasmic reticulum (ER) dilation and upregulated the expression of ER stress markers GRP78, IRE1α, eIF2α, CHOP, JNK, and p38. Subsequently, we also identified that DR increases the levels of apoptotic fragment of PARP (89 kDa) in breast cancer cells. Blocking the expression of one of the components of the ER stress–mediated apoptosis pathway, CHOP using siRNA significantly decreased DR-induced apoptotic cleavage of PARP. In summary, the present study suggests that the induction of ER stress–mediated apoptosis by DR may account for its cytotoxic effects in human breast cancer cells.


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