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Cheong JK, Virshup DM. Keeping autophagy in cheCK1. Mol Cell Oncol 2016; 3:e1045117. [PMID: 27314070 DOI: 10.1080/23723556.2015.1045117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 04/20/2015] [Accepted: 04/21/2015] [Indexed: 10/23/2022]
Abstract
Mutant RAS-driven cancer cells cope with proliferative stress by increasing basal autophagy to maintain protein/organelle and energy homeostasis. We recently demonstrated that casein kinase 1 alpha (CK1α), a therapeutically tractable enzyme, is critical for fine-tuning the transcriptional regulation of mutant RAS-induced autophagy and the development of mutant RAS-driven cancers.
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Affiliation(s)
- Jit Kong Cheong
- Cancer and Stem Cell Biology Program, Duke-NUS Graduate Medical School , Singapore
| | - David M Virshup
- Cancer and Stem Cell Biology Program, Duke-NUS Graduate Medical School , Singapore
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Zhang F, Cheong JK. The renewed battle against RAS-mutant cancers. Cell Mol Life Sci 2016; 73:1845-58. [PMID: 26892781 PMCID: PMC11108322 DOI: 10.1007/s00018-016-2155-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 01/28/2016] [Accepted: 02/01/2016] [Indexed: 12/13/2022]
Abstract
The RAS genes encode for members of a large superfamily of guanosine-5'-triphosphate (GTP)-binding proteins that control diverse intracellular signaling pathways to promote cell proliferation. Somatic mutations in the RAS oncogenes are the most common activating lesions found in human cancers. These mutations invariably result in the gain-of-function of RAS by impairing GTP hydrolysis and are frequently associated with poor responses to standard cancer therapies. In this review, we summarize key findings of past and present landmark studies that have deepened our understanding of the RAS biology in the context of oncogenesis. We also discuss how emerging areas of research could further bolster a renewed global effort to target the largely undruggable oncogenic RAS and/or its activated downstream effector signaling cascades to achieve better treatment outcomes for RAS-mutant cancer patients.
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Affiliation(s)
- Fuquan Zhang
- Programme in Cancer and Stem Cell Biology, Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Jit Kong Cheong
- Programme in Cancer and Stem Cell Biology, Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore.
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Hale CM, Cheng Q, Ortuno D, Huang M, Nojima D, Kassner PD, Wang S, Ollmann MM, Carlisle HJ. Identification of modulators of autophagic flux in an image-based high content siRNA screen. Autophagy 2016; 12:713-26. [PMID: 27050463 PMCID: PMC4836002 DOI: 10.1080/15548627.2016.1147669] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 01/17/2016] [Accepted: 01/23/2016] [Indexed: 12/24/2022] Open
Abstract
Autophagy is the primary process for recycling cellular constituents through lysosomal degradation. In addition to nonselective autophagic engulfment of cytoplasm, autophagosomes can recognize specific cargo by interacting with ubiquitin-binding autophagy receptors such as SQSTM1/p62 (sequestosome 1). This selective form of autophagy is important for degrading aggregation-prone proteins prominent in many neurodegenerative diseases. We carried out a high content image-based siRNA screen (4 to 8 siRNA per gene) for modulators of autophagic flux by monitoring fluorescence of GFP-SQSTM1 as well as colocalization of GFP-SQSTM1 with LAMP2 (lysosomal-associated membrane protein 2)-positive lysosomal vesicles. GFP-SQSTM1 and LAMP2 phenotypes of primary screen hits were confirmed in 2 cell types and profiled with image-based viability and MTOR signaling assays. Common seed analysis guided siRNA selection for these assays to reduce bias toward off-target effects. Confirmed hits were further validated in a live-cell assay to monitor fusion of autophagosomes with lysosomes. Knockdown of 10 targets resulted in phenotypic profiles across multiple assays that were consistent with upregulation of autophagic flux. These hits include modulators of transcription, lysine acetylation, and ubiquitination. Two targets, KAT8 (K[lysine] acetyltransferase 8) and CSNK1A1 (casein kinase 1, α 1), have been implicated in autophagic regulatory feedback loops. We confirmed that CSNK1A1 knockout (KO) cell lines have accelerated turnover of long-lived proteins labeled with (14)C-leucine in a pulse-chase assay as additional validation of our screening assays. Data from this comprehensive autophagy screen point toward novel regulatory pathways that might yield new therapeutic targets for neurodegeneration.
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Affiliation(s)
| | - Qingwen Cheng
- b Department of Neuroscience Research , Amgen Inc. , Thousand Oaks , CA , USA
| | - Danny Ortuno
- b Department of Neuroscience Research , Amgen Inc. , Thousand Oaks , CA , USA
| | - Ming Huang
- b Department of Neuroscience Research , Amgen Inc. , Thousand Oaks , CA , USA
| | - Dana Nojima
- a Discovery Technologies, Amgen Inc. , Thousand Oaks , CA , USA
| | - Paul D Kassner
- c Genome Analysis Unit, Amgen Inc. , Thousand Oaks , CA , USA
| | - Songli Wang
- c Genome Analysis Unit, Amgen Inc. , Thousand Oaks , CA , USA
| | | | - Holly J Carlisle
- b Department of Neuroscience Research , Amgen Inc. , Thousand Oaks , CA , USA
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Abstract
RAS-driven cancers exhibit variable dependency on autophagy for survival; however, it is not fully understood how. In this issue of the JCI, Cheong and colleagues demonstrate that RAS-dependent elevation of casein kinase 1α (CK1α) negatively regulates autophagy at the level of autophagy gene transcription. Moreover, combined inhibition of both CK1α and autophagy reduced proliferation of RAS-driven tumors. The results of this study provide insight into the connection between mutant RAS and autophagy, and suggest targeting CK1α as a potential therapeutic strategy to modulate autophagy in RAS-driven cancers.
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