The pivotal role of c-Jun NH2-terminal kinase-mediated Beclin 1 expression during anticancer agents-induced autophagy in cancer cells.
The c-Jun NH2-terminal kinase (JNK) pathway represents one subgroup of MAP kinases that are activated primarily by cytokines and exposure to environmental stress. Autophagy is a protein-degradation system characterized by the formation of double-membrane vacuoles termed autophagosomes. Autophagy-related gene beclin 1 plays a key role in autophagosome formation. However, the relationships between activation of JNK pathway, autophagy induction and Beclin 1 expression remain elusive. In this study, we used human cancer cell lines CNE2 and Hep3B to investigate the role of JNK-mediated Beclin 1 expression in ceramide-induced autophagic cell death. Ceramide-treated cells exhibited the characteristics of autophagy (that is, acidic vesicular organelle formation and the LC3-II generation). JNK was activated in these two cell lines exposed to ceramide and the phosphorylation of c-Jun also increased. In the meantime, we found that ceramide upregulated Beclin 1 expression in cancer cells. The upregulation of Beclin 1 expression could be blocked by SP600125 (a specific inhibitor of JNK) or a small interfering RNA (siRNA) directed against JNK1/2 or c-Jun. Chromatin immunoprecipitation and luciferase reporter analysis revealed that c-Jun was involved in the regulation of beclin 1 transcription in response to ceramide treatment. In addition, inhibition of JNK activity by SP600125 could inhibit autophagy induction by ceramide. Furthermore, Beclin 1 knockdown by siRNA also inhibited ceramide-mediated autophagic cell death. JNK-mediated Beclin 1 expression was also observed in topotecan-induced autophagy. These data suggest that activation of JNK pathway can mediate Beclin 1 expression, which plays a key role in autophagic cell death in cancer cells.
Li
D-D
DD
State Key Laboratory of Oncology in South China, Cancer Center, Sun Yat-Sen University, Guangzhou, China.
Wang
L-L
LL
Deng
R
R
Tang
J
J
Shen
Y
Y
Guo
J-F
JF
Wang
Y
Y
Xia
L-P
LP
Feng
G-K
GK
Liu
Q Q
QQ
Huang
W-L
WL
Zeng
Y-X
YX
Zhu
X-F
XF
D000873:Anthracenes / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D001343:Autophagy; D000071186:Beclin-1; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002518:Ceramides / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D010588:Phagosomes / Q000378:metabolism; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000378:metabolism
D000873:Anthracenes; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D002518:Ceramides; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D034741:RNA, Small Interfering; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D053148:Caspase 3