Abstract
Regulator of Cullins-1 (ROC1) or RING box protein-1 (RBX1) is an essential RING component of Cullin-RING ligase (CRL). Our previous studies showed that ROC1 is required for the growth of several cancer cell lines while ROC1 siRNA silencing inactivates CRL, leading to cell cycle arrest, cell senescence and/or apoptosis. However, it is completely unknown whether ROC1 knockdown triggers autophagic response by inactivating CRL. Moreover, the role of ROC1 in liver cancer remains elusive. In this study, we reported that ROC1 knockdown significantly inhibited the growth of liver cancer cells by sequentially and independently inducing autophagy and p21-dependent cell senescence. Mechanism analysis revealed that ROC1 silencing triggered autophagy by inhibition of mammalian target of rapamycin (mTOR) activity due to accumulation of mTOR-inhibitory protein Deptor, a substrate of CRL. Consistently, Deptor knockdown significantly blocked autophagy response upon ROC1 silencing. Biologically, autophagy response upon ROC1 silencing was a survival signal, and blockage of autophagy pathway sensitized cancer cells to apoptosis. Finally, we demonstrated that ROC1 was overexpressed in hepatocellular carcinomas, which is associated with poor prognosis of liver cancer patients. These findings suggest that ROC1 is an appealing drug target for liver cancer and provide a proof-of-concept evidence for a novel drug combination of ROC1 inhibitor and an autophagy inhibitor for effective treatment of liver cancer by enhancing apoptosis.
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Abbreviations
- ROC1:
-
regulator of Cullins-1
- CRL:
-
Cullin-RING ligase
- SCF:
-
SKP1-Cullin-F-box proteins
- mTOR:
-
mammalian target of rapamycin
- HCCs:
-
hepatocellular carcinomas
- SA-β-gal:
-
senescence-associated β-galactosidase
- LC3-I:
-
microtubule-associated protein light chain 3-I
- AVO:
-
acidic vesicular organelle
- 3-MA:
-
3-methyladenine
- BafA1:
-
bafilomycin A1
- CQ:
-
Chloroquine
- p-70S6K:
-
phosphorylated 70S6K
- p-4EBP1:
-
phosphorylated 4EBP1
- OIS:
-
oncogene-induced senescence
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Acknowledgements
This work is supported by the National Natural Science Foundation Grant of China (31071204), the National Basic Research Program of China (973 program, 2012CB910302) and Key Project of Shanghai Municipal Health Bureau (2010012) to Lijun Jia, the National Natural Science Foundation Grant of China to Dongqin Yang (81101811) and Jie Liu (91129702,81125001), as well as Postdoctoral Science Foundation of China to Dongqin Yang (KLF101054).
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Yang, D., Li, L., Liu, H. et al. Induction of autophagy and senescence by knockdown of ROC1 E3 ubiquitin ligase to suppress the growth of liver cancer cells. Cell Death Differ 20, 235–247 (2013). https://doi.org/10.1038/cdd.2012.113
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DOI: https://doi.org/10.1038/cdd.2012.113
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