Direct in Vivo RNAi Screen Unveils Myosin IIa as a Tumor Suppressor of Squamous Cell Carcinomas

Schramek, Daniel; Sendoel, Ataman; Segal, Jeremy P.; Beronja, Slobodan; Heller, Evan; Oristian, Daniel; Reva, Boris; Fuchs, Elaine

doi:10.1126/science.1248627

Cited by 233 publications

(240 citation statements)

References 38 publications

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“…Together with the observation that inhibition of myosin light chain phosphorylation by ML-7 had no effect on Lgr5 þ stem cell survival, our data indicate that Myh9-mediated Lgr5 þ stem cell death is independent of dissociation-induced actin-myosin contraction. This idea is consistent with a recent report showing that Myh9 could function as a novel tumour suppressor of squamous cell carcinomas through activating p53 independent of F-actin polymerization 43 . [25][26][27] .…”

Section: Discussionsupporting

confidence: 93%

The non-muscle-myosin-II heavy chain Myh9 mediates colitis-induced epithelium injury by restricting Lgr5+ stem cells

Zhao

et al. 2015

Nat Commun

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Lgr5 þ stem cells are crucial to gut epithelium homeostasis, and therapies targeting these cells hold promise for treatment of gastrointestinal diseases. Here we report that the non-muscle-myosin-II (NMII) heavy chain Myh9 accumulates at epithelial injury sites in mice distal colon treated with dextran sulphate sodium (DSS). Gut-epithelium-specific Myh9 monoallelic deletion alleviates DSS-induced colonic crypt damage and acute colitis. Consistently, the NMII inhibitor blebbistatin can improve the survival of Lgr5 þ stem cells and the growth of Lgr5 organoids. Mechanistically, inhibition of NMII by blebbistatin or Myh9 monoallelic deletion activates Akt through Rac1 and PAK1, which is essential for the survival and pluripotency of Lgr5 þ cells. These results establish a critical role of the Myh9-Rac1-PAK1-Akt pathway in the maintenance of Lgr5 þ stem cells. As blebbistatin can mitigate DSS-induced colitis and preserve Lgr5 þ colonic stem cells in vivo, our findings provide a potential therapeutic intervention of gastrointestinal epithelium injury and degenerative diseases.

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Section: Discussionsupporting

confidence: 93%

The non-muscle-myosin-II heavy chain Myh9 mediates colitis-induced epithelium injury by restricting Lgr5+ stem cells

Zhao

et al. 2015

Nat Commun

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“…Mutations in myosin II paralogs and myosin II regulatory proteins are associated with a number of diseases, such as the MYH9-related disease cluster (May-Hegglin anomaly, Epstein syndrome, and Sebastian syndrome) (28)(29)(30). Increasingly, altered nonmuscle myosin II regulation is correlated with tumor progression and metastasis: The up-regulation of Kras, 14-3-3, and Rac signaling leads to down-regulation of contractile myosin II (8,24,(31)(32)(33)(34)(35). These changes in expression, often caused by genetic lesions, can provide a mechanical differential, giving precancerous cells an advantage over their neighbors in breast and pancreatic cancer progression (23,25,26).…”

Section: Discussionmentioning

confidence: 99%

Pharmacological activation of myosin II paralogs to correct cell mechanics defects

Surcel¹,

Ng²,

West‐Foyle³

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Current approaches to cancer treatment focus on targeting signal transduction pathways. Here, we develop an alternative system for targeting cell mechanics for the discovery of novel therapeutics. We designed a live-cell, high-throughput chemical screen to identify mechanical modulators. We characterized 4-hydroxyacetophenone (4-HAP), which enhances the cortical localization of the mechanoenzyme myosin II, independent of myosin heavy-chain phosphorylation, thus increasing cellular cortical tension. To shift cell mechanics, 4-HAP requires myosin II, including its full power stroke, specifically activating human myosin IIB (MYH10) and human myosin IIC (MYH14), but not human myosin IIA (MYH9). We further demonstrated that invasive pancreatic cancer cells are more deformable than normal pancreatic ductal epithelial cells, a mechanical profile that was partially corrected with 4-HAP, which also decreased the invasion and migration of these cancer cells. Overall, 4-HAP modifies nonmuscle myosin II-based cell mechanics across phylogeny and disease states and provides proof of concept that cell mechanics offer a rich drug target space, allowing for possible corrective modulation of tumor cell behavior. mechanical modulator | 3,4-dichloroaniline | 4-hydroxyacetophenone | myosin II | pancreatic cancer C ell shape change processes include cell growth, division, motility, and the formation of complex structures like tissues and organs, all of which are governed by the intersection of biochemistry, genetics, and mechanics. These three modules are integral not just for normal function in healthy cells but also in disease states. Pharmacological manipulation of some of these modules has already led to treatment strategies for inflammation and cancer (e.g., paclitaxel) (1, 2). However, many presently available therapies, which address only one aspect of cell shape change, typically either fail to abolish the disease completely or lead to compensatory regulatory changes, and therefore to drug resistance. Targeting cell mechanics remains an underused approach for drug development. In cancer, altered cell mechanics are a hallmark of metastatic efficiency: cell stiffness decreases up to 70% in many metastatic cancer cells (3-5). It is rational then that one therapeutic approach is to increase cellular elasticity, which would, in turn, reduce metastatic potential and act downstream of cancer-inducing genetic alterations.Known mechanical modulators (e.g., latrunculin, blebbistatin) are often lethal, have numerous off-site targets, and act to generate a softer and metastatic-like mechanical phenotype (6, 7). However, the field's ability to increase cellular elasticity on acute time scales is highly restricted. In an effort to close this gap and find modulators that stiffen cells, we leveraged our molecular and analytical understanding of cytokinesis, an evolutionarily conserved and highly mechanical cell shape change event, to establish an in vivo, large-scale, high-throughput chemical screen for small-molecule modulators of cell shap...

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“…Underscoring the utility of this approach, we were able to validate the screening results in human cancer cell lines with complex genetic alterations. Similarly focused RNAi screens can be combined with an existing drug to identify novel therapeutic combinations or performed in vivo, where hundreds of genes or drug targets can be evaluated simultaneously in a single animal (Schramek et al 2014).…”

Section: Discussionmentioning

confidence: 99%

CDK9-mediated transcription elongation is required for MYC addiction in hepatocellular carcinoma

et al. 2014

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One-year survival rates for newly diagnosed hepatocellular carcinoma (HCC) are <50%, and unresectable HCC carries a dismal prognosis owing to its aggressiveness and the undruggable nature of its main genetic drivers. By screening a custom library of shRNAs directed toward known drug targets in a genetically defined Myc-driven HCC model, we identified cyclin-dependent kinase 9 (Cdk9) as required for disease maintenance. Pharmacological or shRNA-mediated CDK9 inhibition led to robust anti-tumor effects that correlated with MYC expression levels and depended on the role that both CDK9 and MYC exert in transcription elongation. Our results establish CDK9 inhibition as a therapeutic strategy for MYC-overexpressing liver tumors and highlight the relevance of transcription elongation in the addiction of cancer cells to MYC.

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Direct in Vivo RNAi Screen Unveils Myosin IIa as a Tumor Suppressor of Squamous Cell Carcinomas

Cited by 233 publications

References 38 publications

The non-muscle-myosin-II heavy chain Myh9 mediates colitis-induced epithelium injury by restricting Lgr5+ stem cells

The non-muscle-myosin-II heavy chain Myh9 mediates colitis-induced epithelium injury by restricting Lgr5+ stem cells

Pharmacological activation of myosin II paralogs to correct cell mechanics defects

CDK9-mediated transcription elongation is required for MYC addiction in hepatocellular carcinoma

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