Simultaneous inhibition of the ubiquitin-proteasome system and autophagy enhances apoptosis induced by ER stress aggravators in human pancreatic cancer cells.
In contrast to normal tissue, cancer cells display profound alterations in protein synthesis and degradation. Therefore, proteins that regulate endoplasmic reticulum (ER) homeostasis are being increasingly recognized as potential therapeutic targets. The ubiquitin-proteasome system and autophagy are crucially important for proteostasis in cells. However, interactions between autophagy, the proteasome, and ER stress pathways in cancer remain largely undefined. This study demonstrated that withaferin-A (WA), the biologically active withanolide extracted from Withania somnifera, significantly increased autophagosomes, but blocked the degradation of autophagic cargo by inhibiting SNARE-mediated fusion of autophagosomes and lysosomes in human pancreatic cancer (PC) cells. WA specifically induced proteasome inhibition and promoted the accumulation of ubiquitinated proteins, which resulted in ER stress-mediated apoptosis. Meanwhile, the impaired autophagy at early stage induced by WA was likely activated in response to ER stress. Importantly, combining WA with a series of ER stress aggravators enhanced apoptosis synergistically. WA was well tolerated in mice, and displayed synergism with ER stress aggravators to inhibit tumor growth in PC xenografts. Taken together, these findings indicate that simultaneous suppression of 2 key intracellular protein degradation systems rendered PC cells vulnerable to ER stress, which may represent an avenue for new therapeutic combinations for this disease.
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Xu
X
Li
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Feng
F
Zhu
b Department of Hepatic-Biliary-Pancreatic Surgery , Hubei Cancer Hospital , Wuhan , China.
Jianxin
J
Jiang
c Department of Biliary-Hepatic Surgery , Affiliated Hospital of Guiyang Medical College , Guizhou , China.
Chengyi
C
Sun
d Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center , Dallas , TX , USA.
Qing
Q
Zhong
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Ming
M
Shen
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Xin
X
Wang
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Rui
R
Tian
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Chengjian
C
Shi
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Meng
M
Xu
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Feng
F
Peng
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Xingjun
X
Guo
e Department of Colon Cancer , Tianjin Medical University Cancer Institute and Hospital , Tianjin , China.
Jun
J
Hu
f Department of Oncology , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Dawei
D
Ye
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Min
M
Wang
a Department of Biliary-Pancreatic Surgery , Affiliated Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.
Renyi
R
Qin
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D000071182:Autophagosomes / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects; D016923:Cell Death; D045744:Cell Line, Tumor; D002470:Cell Survival; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005260:Female; D006706:Homeostasis; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D010936:Plant Extracts / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D000071456:Sequestosome-1 Protein / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D054358:Withanolides / Q000494:pharmacology
D000970:Antineoplastic Agents; D010936:Plant Extracts; D061988:Proteasome Inhibitors; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D025801:Ubiquitin; D054358:Withanolides; D046988:Proteasome Endopeptidase Complex; C009684:withaferin A
ER stress; SNAREs; autophagy; proteasome; withaferin A