Gene-gene Interaction of AhR With and Within the Wnt Cascade Affects Susceptibility to Lung Cancer
Albert RosenbergerNils MuttrayRayjean J. HungDavid C. ChristianiNeil E. CaporasoGeoffrey LiuStig E. BojesenLoı̈c Le MarchandDemetrius AlbanesMelinda C. AldrichAdonina TardónGuillermo Fernández‐TardónGad RennertJohn K. FieldMichael DaviesTriantafillos LiloglouLambertus A. KiemeneyPhilip LazarusBernadette WendelAage HaugenShanbeh ZienolddinyStephen LamMatthew B. SchabathAngeline S. AndrewEric J. DuellSusanne M. ArnoldGary E. GoodmanChu ChenJennifer A. DohertyFiona TaylorAngela CoxPenella J. WollAngela RischThomas R MuleyMikael JohanssonPaul BrennanMaria Teresa LandiSanjay SheteChristopher I. AmosHeike Bickeböller
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Abstract Introduction: Aberrant Wnt signalling, regulating cell development and stemness, is observed in many cancer entities. Aryl hydrocarbon receptor ( AhR ) mediates tumorigenesis of environmental pollutants. Complex interaction patterns of genes assigned to AhR/Wnt -signalling were recently associated to lung cancer susceptibility. Aim: To assess the association and predictive ability of AhR/Wnt -genes with lung cancer in cases and controls of European descent. Methods: Odds ratios (OR) were estimated for genomic variants assigned to the genes DKK2 , DKK3 , DKK4 , FRZB , SFRP4 and Axin2 and other lung cancer-related genes. Logistic regression models with variable selection were trained, validated and tested to predict lung cancer. Further, decision trees were created to investigate variant x variant interaction. All analyses were performed for overall lung cancer and for subgroups. Results: No association with overall lung cancer was observed, but within the subgroups of ever smokers (e.g. maker rs2722278 SFRP4; OR=1.20; 95%-CI: 1.13-1.27; p=5.6 10 -10 ) and never smokers. Although predictability is poor, AhR/Wnt-variants are unexpected overrepresented in optimized prediction scores for overall lung cancer and for small cell lung cancer. Remarkable, the score for never-smokers contained solely two AhR/Wnt-variants . The optimal decision tree for never smokers consists of 7 AhR/Wnt-variants and only two lung cancer variants, no assigned to any CHRN gene. Conclusions: The role of variants belonging to Wnt / AhR- pathways in lung cancer susceptibility may be underrated in main-effects association analysis. Complex interaction patterns in individuals of European descent have moderate predictive capacity for lung cancer or subgroups thereof, especially in never smokers.Keywords:
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In the liver, Wnt/β-catenin signaling is involved in regulating zonation and hepatocyte proliferation during homeostasis. We have examined Wnt gene expression and signaling after injury and we show by in situ hybridization that Wnts are activated by acute carbon tetrachloride (CCl4) toxicity. Following injury, peri-injury hepatocytes become Wnt-responsive, expressing the Wnt target gene Axin2. Lineage tracing of peri-injury Axin2+ hepatocytes shows that during recovery, the injured parenchyma becomes repopulated and repaired by Axin2+ descendants. Using single cell RNA sequencing (scRNA-seq), we show that endothelial cells are the major source of Wnts following acute CCl4 toxicity. Induced loss of β-catenin in peri-injury hepatocytes results in delayed repair and ultimately to injury-induced lethality, while loss of Wnt production from endothelial cells leads to a delay in the proliferative response after injury. Conclusion: Our Findings highlight the importance of the Wnt/β-catenin signaling pathway in restoring tissue integrity following acute liver toxicity and establishes a role of endothelial cells as an important Wnt-producing regulator of liver tissue repair following localized liver injury.
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Abstract Wnt signaling drives nuclear translocation of β-catenin and its subsequent association with the DNA-bound TCF/LEF transcription factors, which dictate target gene specificity by recognizing Wnt responsive elements across the genome. β-catenin target genes are therefore thought to be collectively activated upon Wnt pathway stimulation. However, this appears in contrast with the non-overlapping patterns of Wnt target gene expression in several contexts, including early mammalian embryogenesis. Here we followed Wnt target gene expression in human embryonic stem cells after Wnt pathway stimulation at a single-cell resolution. Cells changed gene expression program over time consistent with three key developmental events: i) loss of pluripotency, ii) induction of Wnt target genes, and iii) mesoderm specification. Contrary to our expectation, not all cells displayed equal amplitude of Wnt target gene activation; rather, they distributed in a continuum from strong to weak responders when ranked based on the expression of the target AXIN2 . Moreover, high AXIN2 did not always correspond to elevated expression of other Wnt targets, which were activated in different proportions in individual cells. This uncoupling of Wnt target gene expression, which was also identified in single colorectal cancer cells with hyper-activated Wnt signaling, underlines the necessity to identify additional mechanisms that explain the heterogeneity of the Wnt/β-catenin-mediated transcriptional outputs in single cells.
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Wnt signaling drives nuclear translocation of β-catenin and its subsequent association with the DNA-bound TCF/LEF transcription factors, which dictate target gene specificity by recognizing Wnt responsive elements across the genome. β-Catenin target genes are therefore thought to be collectively activated upon Wnt pathway stimulation. However, this appears in contrast with the non-overlapping patterns of Wnt target gene expression in several contexts, including early mammalian embryogenesis. Here we followed Wnt target gene expression in human embryonic stem cells after Wnt pathway stimulation at a single-cell resolution. Cells changed gene expression program over time consistent with three key developmental events: i) loss of pluripotency, ii) induction of Wnt target genes, and iii) mesoderm specification. Contrary to our expectation, not all cells displayed equal amplitude of Wnt target gene activation; rather, they distributed in a continuum from strong to weak responders when ranked based on the expression of the target AXIN2. Moreover, high AXIN2 did not always correspond to elevated expression of other Wnt targets, which were activated in different proportions in individual cells. The uncoupling of Wnt target gene expression was also identified in single cell transcriptomics profiling of other Wnt-responding cell types, including HEK293T, murine developing forelimbs, and human colorectal cancer. Our finding underlines the necessity to identify additional mechanisms that explain the heterogeneity of the Wnt/β-catenin-mediated transcriptional outputs in single cells.
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e15185 Background: Aberrant activation of Wnt signaling contributing to tumorigenesis is most commonly associated with CRC (90% harbor Wnt pathway mutations). SM08502, a novel, oral Wnt signaling pathway inhibitor, was evaluated in preclinical CRC models. Methods: In vitro Wnt signaling: assessed using TOPflash β-catenin/TCF reporter assay in SW480 human CRC cells. In vitro Wnt pathway gene expression: measured by qRT-PCR in SW480 and Wnt3a-stimulated cells (HEK-293T, IEC-6), and with the Nanostring Wnt pathway array (180 genes) across a panel of 16 CRC cell lines. In vitro cell proliferation: 17 CRC cell lines were used to test cell viability following treatment. In vivo antitumor activity: Oral SM08502 was tested in CRC mouse xenografts (SW480, HCT 116) and a PDX model over 20-21 days (QD, QOD). 24-hr pharmacodynamic (PD) analysis of Wnt pathway gene expression was done in SW480 tumor explants from mice following one 25 mg/kg dose. Results: SM08502 inhibited Wnt pathway signaling (EC 50 = 46 nM) in SW480 cells. Wnt pathway gene expression was inhibited by SM08502 (0.3-3 µM) in Wnt3a-stimulated cells ( AXIN2, LEF1) and SW480 ( AXIN2, CTNNB1, LEF1, MYC, TCF7, TCF7L2) at 24 hrs ( P < .05 vs. vehicle) . Corresponding effects on protein expression were confirmed for all genes except CTNNB1, suggesting SM08502 acted independently of β-catenin. Nanostring array screening identified inhibition of LRP5, DVL2, BTRC, and ERBB2 by SM08502. Cell proliferation was inhibited in all 17 lines (avg. EC 50 = 177 nM). In vivo, SM08502 was well tolerated and induced dose-dependent antitumor effects in xenografts and PDX models. Tumor growth inhibition for 25 mg/kg QD (max dose) was 83%, 56%, and 70% in SW480, HCT 116, and PDX, respectively. PD analysis showed significant inhibition ( P< .05 vs. vehicle) of TCF7, MYC, LRP5, DVL2, and BTRC expression 8 hrs post treatment. Conclusions: In preclinical CRC models, SM08502 was a potent inhibitor of Wnt pathway signaling and gene expression. It showed strong antitumor activity in human tumor models with activating Wnt pathway mutations. The safety, tolerability, and PK of SM08502 are being evaluated in an ongoing phase 1 study (NCT03355066).
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Abstract The Wnt/β-catenin signaling pathway is important for multiple developmental processes and tissue maintenance in adults. Consequently, deregulated signaling is involved in a range of human diseases including cancer and developmental defects. A better understanding of the intricate regulatory mechanism and effect of physiological (active) and pathophysiological (hyperactive) WNT signaling is important for predicting treatment response and developing novel therapies. The constitutively expressed CTNNB1 (commonly and hereafter referred to as β-catenin) is degraded by a destruction complex, composed of amongst other AXIN1 and GSK3. The destruction complex is inhibited during active signaling leading to β-catenin stabilization and induction of β-catenin/TCF target genes. In this study we investigated the mechanism and effect of β-catenin stabilization during active and hyperactive WNT signaling in a combined in silico and in vitro approach. We constructed a Petri net model of Wnt/β-catenin signaling including main players from the plasma membrane (WNT ligands and receptors), cytoplasmic effectors and the downstream negative feedback target gene AXIN2 . We simulated the model with active (i.e. WNT stimulation) and hyperactive (i.e. GSK3 inhibition) signaling, which led to the following observations: 1) A dose- and time-dependent response was observed for both WNT stimulation and GSK3 inhibition. 2) The Wnt-pathway activity was 2-fold higher for GSK3 inhibition compared to WNT stimulation. Both of these observations were corroborated by TCF/LEF luciferase reporter assays. Using this experimentally validated model we simulated the effect of the negative feedback regulator AXIN2 upon WNT stimulation and observed an attenuated β-catenin stabilization. We furthermore simulated the effect of APC inactivating mutations, yielding a stabilization of β-catenin levels comparable to the Wnt-pathway activities observed in colorectal and breast cancer. Our model can be used for further investigation and viable predictions of the role of Wnt/β-catenin signaling in oncogenesis and development. Author Summary Deregulated Wnt/β-catenin signaling is implicated in cancer and developmental defects. In this study we combined in silico and in vitro efforts to investigate the behavior of physiological and pathophysiological WNT signaling. We created a model of Wnt/β-catenin signaling that describes the core interactions: receptor activation, inhibition of downstream effectors and an important negative feedback mechanism. Simulations with the model demonstrated the expected dose- and time-dependent response for both conditions, and the Wnt-pathway activity was significantly higher for pathophysiological compared to physiological signaling. These observations were experimentally validated, which allowed us to investigate and predict the effect of the negative feedback and an inactivating cancer mutation on the Wnt-pathway activity. Our model provides mechanistic insight on the different conditions and can easily be extended and used to answer other questions on Wnt/β-catenin signaling in the area of cancer research and regenerative medicine.
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Significance Despite the importance of Wnt signaling in bone biology, there is a knowledge gap in the identity of the cells that produce the Wnt ligands and the functions of Wnts produced by specific cell types. In our study, we comprehensively characterized the expression patterns of all 19 Wnts in the developing mouse bone by in situ hybridization, and further showed that Osterix-expressing cells can produce Wnts and respond to Wnt signaling. Additionally, we found that Wnts produced by these Osterix-expressing cells regulate their differentiation and proliferation. Through providing a better understanding of how Wnt signaling contributes to bone biology, our findings also have clinical implications for the mechanism of the osteoporotic drug that targets Sclerostin, a Wnt signaling antagonist.
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Abstract Wnt signaling is a crucial developmental pathway involved in early development as well as stem cell maintenance in adults and its misregulation leads to numerous diseases. Thus, understanding the regulation of this pathway becomes vitally important. Axin2 and Nkd1 are widely utilized negative feedback regulators in Wnt signaling where Axin2 functions to destabilize cytoplasmic β-catenin, and Nkd1 functions to inhibit the nuclear localization of β-catenin. Here, we set out to further understand how Axin2 and Nkd1 regulate Wnt signaling by creating axin2 -/- , nkd1 -/- single mutants and axin2 -/- ; nkd1 -/- double mutant zebrafish using sgRNA/Cas9. All three Wnt regulator mutants were viable and had impaired heart looping, neuromast migration defects, and behavior abnormalities in common, but there were no signs of synergy in the axin2 -/- ; nkd1 -/- double mutants. Further, Wnt target gene expression by qRT-PCR, and RNA-seq analysis and protein expression by mass spectrometry demonstrated that the double axin2 -/- ; nkd1 -/- mutant resembled the nkd1 -/- phenotype demonstrating that Axin2 functions upstream of Nkd1 and that loss of Nkd1 is epistatic to the loss of Axin2. In support of this, the data further demonstrates that Axin2 uniquely alters the properties of β-catenin-dependent transcription having novel readouts of Wnt activity compared to nkd1 -/- or the axin2 -/- ; nkd1 -/- double mutant. We also tested the sensitivity of the Wnt regulator mutants to exacerbated Wnt signaling, where the single mutants displayed characteristic heightened Wnt sensitivity, resulting in an eyeless phenotype. Surprisingly, this phenotype was rescued in the double mutant, where we speculate that cross-talk between Wnt/β-catenin and Wnt/Planar Cell Polarity pathways could lead to altered Wnt signaling in some scenarios. Collectively, the data emphasizes both the commonality and the complexity in the feedback regulation of Wnt signaling.
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The Wnt/β-catenin signaling pathway is important for multiple developmental processes and tissue maintenance in adults. Consequently, deregulated signaling is involved in a range of human diseases including cancer and developmental defects. A better understanding of the intricate regulatory mechanism and effect of physiological (active) and pathophysiological (hyperactive) WNT signaling is important for predicting treatment response and developing novel therapies. The constitutively expressed CTNNB1 (commonly and hereafter referred to as β-catenin) is degraded by a destruction complex, composed of amongst others AXIN1 and GSK3. The destruction complex is inhibited during active WNT signaling, leading to β-catenin stabilization and induction of β-catenin/TCF target genes. In this study we investigated the mechanism and effect of β-catenin stabilization during active and hyperactive WNT signaling in a combined in silico and in vitro approach. We constructed a Petri net model of Wnt/β-catenin signaling including main players from the plasma membrane (WNT ligands and receptors), cytoplasmic effectors and the downstream negative feedback target gene AXIN2. We validated that our model can be used to simulate both active (WNT stimulation) and hyperactive (GSK3 inhibition) signaling by comparing our simulation and experimental data. We used this experimentally validated model to get further insights into the effect of the negative feedback regulator AXIN2 upon WNT stimulation and observed an attenuated β-catenin stabilization. We furthermore simulated the effect of APC inactivating mutations, yielding a stabilization of β-catenin levels comparable to the Wnt-pathway activities observed in colorectal and breast cancer. Our model can be used for further investigation and viable predictions of the role of Wnt/β-catenin signaling in oncogenesis and development.
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