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MTOR signaling mediates resistance to tankyrase inhibitors in Wnt-driven colorectal cancer.

ABSTRACT: Activation of Wnt/?-catenin signaling is essential for colorectal carcinogenesis. Tankyrase, a member of the poly(ADP-ribose) polymerase (PARP) family, is a positive regulator of the Wnt/?-catenin signaling. Accordingly, tankyrase inhibitors are under preclinical development for colorectal cancer (CRC) therapy. However, Wnt-driven colorectal cancer cells are not equally sensitive to tankyrase inhibitors, and cellular factors that affect tankyrase inhibitor sensitivity remain elusive. Here, we established a tankyrase inhibitor-resistant cell line, 320-IWR, from Wnt/?-catenin-dependent CRC COLO-320DM cells. 320-IWR cells exhibited resistance to tankyrase inhibitors, IWR-1 and G007-LK, but remained sensitive to a PARP-1/2 inhibitor, olaparib, and several anti-CRC agents. In 320-IWR cells, nuclear localization of active ?-catenin was decreased and expression of ?-catenin target genes was constitutively repressed, suggesting that these cells repressed the Wnt/?-catenin signaling and were dependent on alternative proliferation pathways. 320-IWR cells exhibited upregulated mTOR signaling and were more sensitive to mTOR inhibition than the parental cells. Importantly, mTOR inhibition reversed resistance to tankyrase inhibitors and potentiated their anti-proliferative effects in 320-IWR cells as well as in CRC cell lines in which the mTOR pathway was intrinsically activated. These results indicate that mTOR signaling confers resistance to tankyrase inhibitors in CRC cells and suggest that the combination of tankyrase and mTOR inhibitors would be a useful therapeutic approach for a subset of CRCs.

SUBMITTER: Mashima T

PROVIDER: S-EPMC5564614 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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mTOR signaling mediates resistance to tankyrase inhibitors in Wnt-driven colorectal cancer.

Mashima Tetsuo T Taneda Yoko Y Jang Myung-Kyu MK Mizutani Anna A Muramatsu Yukiko Y Yoshida Haruka H Sato Ayana A Tanaka Noritaka N Sugimoto Yoshikazu Y Seimiya Hiroyuki H

Oncotarget 20170701 29

Activation of Wnt/β-catenin signaling is essential for colorectal carcinogenesis. Tankyrase, a member of the poly(ADP-ribose) polymerase (PARP) family, is a positive regulator of the Wnt/β-catenin signaling. Accordingly, tankyrase inhibitors are under preclinical development for colorectal cancer (CRC) therapy. However, Wnt-driven colorectal cancer cells are not equally sensitive to tankyrase inhibitors, and cellular factors that affect tankyrase inhibitor sensitivity remain elusive. Here, we es ...[more]

PMID: 28615517

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Project description:BackgroundWnt signaling drives epithelial self-renewal and disease progression in human colonic epithelium and colorectal cancer (CRC). Characterization of Wnt effector pathways is key for our understanding of these processes and for developing therapeutic strategies that aim to preserve tissue homeostasis. O-glycosylated cell surface proteins, such as ?-dystroglycan (?-DG), mediate cellular adhesion to extracellular matrix components. We revealed a Wnt/LARGE2/?-DG signaling pathway which triggers this mode of colonic epithelial cell-to-matrix interaction in health and disease.MethodsNext generation sequencing upon shRNA-mediated silencing of adenomatous polyposis coli (APC), and quantitative chromatin immunoprecipitation (qChIP) combined with CRISPR/Cas9-mediated transcription factor binding site targeting characterized LARGE2 as a Wnt target gene. Quantitative mass spectrometry analysis on size-fractionated, glycoprotein-enriched samples revealed functional O-glycosylation of ?-DG by LARGE2 in CRC. The biology of Wnt/LARGE2/?-DG signaling was assessed by affinity-based glycoprotein enrichment, laminin overlay, CRC-to-endothelial cell adhesion, and transwell migration assays. Experiments on primary tissue, human colonic (tumor) organoids, and bioinformatic analysis of CRC cohort data confirmed the biological relevance of our findings.ResultsNext generation sequencing identified the LARGE2 O-glycosyltransferase encoding gene as differentially expressed upon Wnt activation in CRC. Silencing of APC, conditional expression of oncogenic ?-catenin and endogenous ?-catenin-sequestration affected LARGE2 expression. The first intron of LARGE2 contained a CTTTGATC motif essential for Wnt-driven LARGE2 expression, showed occupation by the Wnt transcription factor TCF7L2, and Wnt activation triggered LARGE2-dependent ?-DG O-glycosylation and laminin-adhesion in CRC cells. Colonic crypts and organoids expressed LARGE2 mainly in stem cell-enriched subpopulations. In human adenoma organoids, activity of the LARGE2/?-DG axis was Wnt-dose dependent. LARGE2 expression was elevated in CRC and correlated with the Wnt-driven molecular subtype and intestinal stem cell features. O-glycosylated ?-DG represented a Wnt/LARGE2-dependent feature in CRC cell lines and patient-derived tumor organoids. Modulation of LARGE2/?-DG signaling affected CRC cell migration through laminin-coated membranes and adhesion to endothelial cells.ConclusionsWe conclude that the LARGE2 O-glycosyltransferase-encoding gene represents a direct target of canonical Wnt signaling and mediates functional O-glycosylation of ?-dystroglycan (?-DG) in human colonic stem/progenitor cells and Wnt-driven CRC. Our work implies that aberrant Wnt activation augments CRC cell-matrix adhesion by increasing LARGE/?-DG-mediated laminin-adhesiveness. Video abstract.

Dataset Information

MTOR signaling mediates resistance to tankyrase inhibitors in Wnt-driven colorectal cancer.

Publications

mTOR signaling mediates resistance to tankyrase inhibitors in Wnt-driven colorectal cancer.

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