Casein kinase 1α–dependent feedback loop controls autophagy in RAS-driven cancers

Cheong, Jit Kong; Zhang, Fuquan; Chua, Pei Jou; Bay, Boon Huat; Thorburn, Andrew; Virshup, David M.

doi:10.1172/jci78018

Cited by 57 publications

(68 citation statements)

References 67 publications

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“…Cellular Physiology and Biochemistry target for anti-tumour therapies [32,33]. The results of these studies are consistent with our results, which showed that FOXO3 plays a protective role in gastric tumour cells in abnormal microenvironments, such as acidic microenvironments.…”

Section: Cellular Physiology and Biochemistrysupporting

confidence: 92%

FOXO3 Inhibits Human Gastric Adenocarcinoma (AGS) Cell Growth by Promoting Autophagy in an Acidic Microenvironment

Gao

Sun

et al. 2018

Cell Physiol Biochem

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Background/Aims: Previous studies have shown that FOXO3, a member of the forkhead box O (FOXO) family, regulates autophagy in various cells. To date, whether the induction of autophagy in gastric cancer (GC) cells is triggered by an acidic microenvironment is unclear. Little is known about the relationship between FOXO3 and acidic microenvironments in GC. The aims of our study were to investigate the roles of FOXO3 and the acidic microenvironment in autophagy and to determine how FOXO3 and the acidic microenvironment regulate GC cell growth through autophagy. Methods: We cultured human gastric adenocarcinoma (AGS) cells in media with different pH values in vitro, transfected the cells with FOXO3a plasmids and then detected autophagy in the cells under different conditions. In addition, we also performed cell counting kit 8 (CCK8), wound and cell invasion assays to test cell viability and invasion, respectively. We employed real-time PCR, western blotting and mRFP-GFP-LC3 vectors to detect the expression of various autophagy indicators. Results: We found that cells treated with FOXO3 and exposed to an acidic microenvironment displayed suppressed growth compared with control cells. We also found that the protein expression levels of several autophagy makers, such as LC3I, LC3II and Beclin-1, were higher in FOXO3 plasmid-transfected AGS cells cultured in an acidic microenvironment than in control cells, while P62 protein expression levels were clearly decreased in FOXO3 plasmid-transfected cells compared with control cells. Moreover, we observed autophagic flux in AGS cells overexpressing FOXO3 and exposed to low pH conditions. Conclusion: These findings suggest that FOXO3 inhibits AGS cell growth by promoting autophagy in an acidic microenvironment. Furthermore, the results showed that anticancer therapies targeting FOXO3 and low pH conditions may be useful in the treatment of GC.

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Section: Cellular Physiology and Biochemistrysupporting

confidence: 92%

FOXO3 Inhibits Human Gastric Adenocarcinoma (AGS) Cell Growth by Promoting Autophagy in an Acidic Microenvironment

Gao

Sun

et al. 2018

Cell Physiol Biochem

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“…Thus, it remains plausible that a subset of SSTC3’s effects on CRC viability occur via a non-WNT–dependent mechanism. For example, CK1α has been implicated in the p53/MDM2 (47–49), FOXO1/autophagy (50–52), and sonic hedgehog–GLI (53–55) signaling pathways, all of which have also been implicated in aspects of CRC progression (56–59). Pyrvinium, the first-in-class CK1α activator, was reported to exert antitumor activity through suppression of GLI activity (60) or autophagy flux (61).…”

Section: Discussionmentioning

confidence: 99%

Differential abundance of CK1α provides selectivity for pharmacological CK1α activators to target WNT-dependent tumors

Orton

Neitzel

et al. 2017

Sci. Signal.

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Constitutive WNT activity drives the growth of various human tumors, including nearly all colorectal cancers (CRCs). Despite this prominence in cancer, no WNT inhibitor is currently approved for use in the clinic largely due to the small number of druggable signaling components in the WNT pathway and the substantial toxicity to normal gastrointestinal tissue. We have shown that pyrvinium, which activates casein kinase 1α (CK1α), is a potent inhibitor of WNT signaling. However, its poor bioavailability limited the ability to test this first-in-class WNT inhibitor in vivo. We characterized a novel small-molecule CK1α activator called SSTC3, which has better pharmacokinetic properties than pyrvinium, and found that it inhibited the growth of CRC xenografts in mice. SSTC3 also attenuated the growth of a patient-derived metastatic CRC xenograft, for which few therapies exist. SSTC3 exhibited minimal gastrointestinal toxicity compared to other classes of WNT inhibitors. Consistent with this observation, we showed that the abundance of the SSTC3 target, CK1α, was decreased in WNT-driven tumors relative to normal gastrointestinal tissue, and knocking down CK1α increased cellular sensitivity to SSTC3. Thus, we propose that distinct CK1α abundance provides an enhanced therapeutic index for pharmacological CK1α activators to target WNT-driven tumors.

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“…This is consistent with a recent study showing that CSNK1A1 phosphorylates the transcription factor FOXO3A and limits its nuclear localization, reducing transcription of autophagy-related genes in RAS-driven cancer cells. 31 RNAseq expression profiles reported for human (NextBio Body Atlas, http://www.nextbio.com/b/nextbioCorp.nb) 32 and mouse 33 brain tissues indicate that at least 5 of the top 10 hits from the screen are likely to be expressed in neurons, with CSNK1A1 showing relatively high levels of expression across multiple brain tissues (Figs. S8 and S9).…”

Section: Discussionmentioning

confidence: 99%

Identification of modulators of autophagic flux in an image-based high content siRNA screen

et al. 2016

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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, a 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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Casein kinase 1α–dependent feedback loop controls autophagy in RAS-driven cancers

Cited by 57 publications

References 67 publications

FOXO3 Inhibits Human Gastric Adenocarcinoma (AGS) Cell Growth by Promoting Autophagy in an Acidic Microenvironment

FOXO3 Inhibits Human Gastric Adenocarcinoma (AGS) Cell Growth by Promoting Autophagy in an Acidic Microenvironment

Differential abundance of CK1α provides selectivity for pharmacological CK1α activators to target WNT-dependent tumors

Identification of modulators of autophagic flux in an image-based high content siRNA screen

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