Oncogene addiction to GNAS in GNASR201 mutant tumors
Ontology highlight
ABSTRACT: The GNASR201 gain-of-function mutation is the single most frequent cancer-causing mutation across all heterotrimeric G proteins, driving oncogenesis in various low-grade/benign gastrointestinal and pancreatic tumors. In this study, we investigated the role of GNAS and its product Gαs in tumor progression using peritoneal models of colorectal cancer (CRC). GNAS was knocked out in multiple CRC cell lines harboring GNASR201C/H mutations (KM12, SNU175, SKCO1), leading to decreased cell-growth in 2D and 3D organoid models. Nude mice were peritoneally injected with GNAS-knockout KM12 cells, leading to a decrease in tumor growth and drastically improved survival at 7 weeks. Supporting these findings, GNAS overexpression in LS174T cells led to increased cell-growth in 2D and 3D organoid models, and increased tumor growth in PDX mouse models. GNAS knockout decreased levels of cyclic AMP in KM12 cells, and molecular profiling identified phosphorylation of β-catenin and activation of its targets as critical downstream effects of mutant GNAS signaling. Supporting these findings, chemical inhibition of both PKA and β-catenin reduced growth of GNAS mutant organoids. Our findings demonstrate oncogene addiction to GNAS in peritoneal models of GNASR201C/H tumors, which signal through the cAMP/PKA and Wnt/β-catenin pathways. Thus, GNAS and its downstream mediators are promising therapeutic targets for GNAS mutant tumors.
Project description:Strong activation of the oncogenic Wnt/beta-catenin pathway is a main mechanism of resistance to FOXO3a-induced apoptosis promoted by PI3K and AKT inhibitors in colorectal cancer (CRC). Reducing Wnt/beta-catenin activity would sensitize colorectal tumors to these inhibitors. However, no Wnt/beta-catenin signaling inhibitor has proven clinical potential yet. Recently, inhibitors that block tankyrases were shown to reduce colon cancer cell proliferation by decreasing nuclear beta-catenin. We aim to identify determinants of response to these novel Wnt-inhibitors. Therefore, we treated in vivo three different patient-derived xenograft models (PDX; P2, P5 and P30) growing subcutaneously in NOD SCID mice with the novel tankyrase inhibitor NVP-TNKS656.
Project description:Wnt/β-catenin signaling is activated in colorectal cancer (CRC) and is involved in CRC growth. Tankyrase, a poly(ADP-ribose) polymerase family member, destabilizes Axin and positively regulates the Wnt/β-catenin signaling. Tankyrase inhibitors efficiently suppress CRC cell proliferation. We established 320-IWR cells, which showed resistance to tankyrase inhibitor IWR-1, from human CRC COLO-320DM cells. We analyzed gene expression profile of 320-IWR cells (320IWR_1,_2) and parental COLO-320DM cells (COLO320_1,_2).
Project description:Colorectal cancer (CRC) is the second leading cause of cancer mortality worldwide. However, the molecular mechanisms underlying CRC progression remain to be further defined to improve patient outcomes. In this study, we found that KCTD9, a member of the potassium channel tetramerization domain-containing (KCTD) gene family, was commonly downregulated in CRC tissues and that KCTD9 expression was negatively correlated with the clinical CRC stage. Survival analysis showed that patients whose tumors expressed low KCTD9 levels had poorer outcomes. Functional analyses revealed that KCTD9 overexpression inhibited CRC cell proliferation and metastasis, whereas KCTD9 knockdown promoted CRC cell proliferation and metastasis in both in vitro and in vivo models. Manipulating KCTD9 levels in CRC cells via overexpression or knockdown showed KCTD9 expression positively influenced the degradation of β-catenin levels leading to inhibition of Wnt signaling and reductions in Wnt pathway target gene expression. Mechanistically, we found KCTD9 associated with ZNT9 (Zinc Transporter 9), a coactivator of β-catenin-mediated gene transcription. The overexpression of KCTD9 or knockdown of ZNT9 in CRC cells increased the polyubiquitination and proteasomal degradation of β-catenin. In turn, the KCTD9-ZNT9 interaction disrupted interactions between β-catenin and ZNT9, thereby leading to decreased β-catenin target gene expression and the inhibition of Wnt signaling. In conclusion, our findings propose that KCTD9 functions as a tumor suppressor that inhibits CRC cell proliferation and metastasis by inactivating the Wnt/β-catenin pathway. Moreover, its frequent downregulation in CRC suggests KCTD9 as a potential prognostic and therapeutic target in CRC.
Project description:The tumor suppressor gene adenomatous polyposis coli (APC) is mutated in most colorectal cancers (CRC) resulting in constitutive Wnt activation. To understand the Wnt-activating mechanism of APC mutation, we applied CRISPR/Cas9 technology to engineer various APC-truncated isogenic lines. We find that the β-catenin inhibitory domain (CID) in APC represents the threshold for pathological levels of Wnt activation and tumor transformation. Mechanistically, CID-deleted APC truncation promotes β-catenin deubiquitination through reverse binding of β-TrCP and USP7 to the destruction complex. USP7 depletion in APC-mutated CRC inhibits Wnt activation by restoring β-catenin ubiquitination, drives differentiation and suppresses xenograft tumor growth. Finally, the Wnt-activating role of USP7 is specific to APC mutations, thus can be used as tumor-specific therapeutic target for most CRCs.
Project description:Spheroids are 3D multi-cell aggregates formed in non-addherent culture conditions. In ovarian cancer (OC), they serve as a vehicle for cancer cell dissemination in the peritoneal cavity. We investigated genes and networks upregulated in three dimensional (3D) versus two-dimensional (2D) culture conditions by Affymetrix gene expression profiling and identified ALDH1A1, a cancer stem cell marker as being upregulated in OC spheroids. Network analysis confirmed ALDH1A1 upregulation in spheroids in direct connection with elements of the beta-catenin pathway. A parallel increase in the expression levels of beta-catenin and ALDH1A1 was demonstrated in spheroids vs. monolayers an in successive spheroid generations by using OC cell liness and primary OC cells. The percentage of Aldefluor positive cells was significantly higher in spheroids vs. monolayers in IGROV1, A2780, SKOV3, and primary OC cells. B-catenin knock-down decreased ALDH1A1 expression and chromatin immunoprecipitation demonstrated that beta-catenin directly binds to the ALDH1A1 promoter. Both siRNA mediated beta-catenin knock-down and a novel ALDH1A1 small molecule enzymatic inhibitor described here for the first time, decreased the number of OC spheroids (p<0.001) and cell viability. These data strongly support the role of beta-catenin regulated ALDH1A1 in the maintenance of OC spheroids and of a stem cell phenotype and propose new ALDH1A1 inhibitors targeting this cell population. Different gene profiles were observed in ovarian cancer spheroids versus ovarian cancer monolayers. Nine samples were analyzed in triplicate. Each group is a reference.
Project description:Unrestrained transcriptional activity of β-CATENIN and its binding partner TCF7L2 frequently underlies colorectal tumor initiation and is considered an obligatory oncogenic driver throughout intestinal carcinogenesis. Yet, the TCF7L2 gene carries inactivating mutations in about 10 % of colorectal tumors and is non-essential in colorectal cancer (CRC) cell lines. To determine whether CRC cells acquire TCF7L2-independence through cancer-specific compensation by other T-cell factor (TCF)/lymphoid enhancer‑binding factor (LEF) family members, or rather lose addiction to β-CATENIN/TCF7L2-driven gene expression altogether, we generated multiple CRC cell lines entirely negative for TCF/LEF or β-CATENIN expression. Viability of these cells demonstrates complete β‑CATENIN- and TCF/LEF-independence, albeit one β-CATENIN-deficient cell line eventually became senescent. Absence of TCF/LEF proteins and β-CATENIN consistently impaired CRC cell proliferation, reminiscent of mitogenic effects of WNT/β-CATENIN signaling in the healthy intestine. Despite this common phenotype, β-CATENIN-deficient cells exhibited highly cell-line-specific gene expression changes with little overlap between β-CATENIN- and TCF7L2-dependent transcriptomes. Apparently, β‑CATENIN and TCF7L2 control sizeable fractions of their target genes independently from each other. The observed divergence of β-CATENIN and TCF7L2 transcriptional programs, and the finding that neither β-CATENIN nor TCF/LEF activity is strictly required for CRC cell survival has important implications when evaluating these factors as potential drug targets.
Project description:The lysine methyltransferase EZH2 is overexpressed in colorectal cancer (CRC) and has been found to be positively and negatively correlated with CRC patient survival depending on the study suggesting that EZH2 has a complex role in CRC. Here, we demonstrate that AKT-mediated EZH2 S21 phosphorylation induced EZH2 to trimethylate β-catenin at K49, which increased β-catenin’s binding to the chromatin. Additionally, EZH2-mediated β-catenin trimethylation induced β-catenin’s interaction with TCF1 and RNA polymerase II and resulted in a dramatic gain in genomic regions with β-catenin occupancy. Interestingly, EZH2 catalytic inhibition decreased stemness but increased migratory phenotypes of CRC cells with active AKT. Overall, we demonstrated that EZH2 modulates AKT-induced changes in gene expression through the AKT/EZH2/β-catenin axis in CRC. Our results suggest that EZH2 inhibitors have tumor-inhibiting and promoting effects in CRC as they inhibit EZH2-mediated methylation of histone and non-histone targets like β-catenin.
Project description:The lysine methyltransferase EZH2 is overexpressed in colorectal cancer (CRC) and has been found to be positively and negatively correlated with CRC patient survival depending on the study suggesting that EZH2 has a complex role in CRC. Here, we demonstrate that AKT-mediated EZH2 S21 phosphorylation induced EZH2 to trimethylate β-catenin at K49, which increased β-catenin’s binding to the chromatin. Additionally, EZH2-mediated β-catenin trimethylation induced β-catenin’s interaction with TCF1 and RNA polymerase II and resulted in a dramatic gain in genomic regions with β-catenin occupancy. Interestingly, EZH2 catalytic inhibition decreased stemness but increased migratory phenotypes of CRC cells with active AKT. Overall, we demonstrated that EZH2 modulates AKT-induced changes in gene expression through the AKT/EZH2/β-catenin axis in CRC. Our results suggest that EZH2 inhibitors have tumor-inhibiting and promoting effects in CRC as they inhibit EZH2-mediated methylation of histone and non-histone targets like β-catenin.
Project description:The lysine methyltransferase EZH2 is overexpressed in colorectal cancer (CRC) and has been found to be positively and negatively correlated with CRC patient survival depending on the study suggesting that EZH2 has a complex role in CRC. Here, we demonstrate that AKT-mediated EZH2 S21 phosphorylation induced EZH2 to trimethylate β-catenin at K49, which increased β-catenin’s binding to the chromatin. Additionally, EZH2-mediated β-catenin trimethylation induced β-catenin’s interaction with TCF1 and RNA polymerase II and resulted in a dramatic gain in genomic regions with β-catenin occupancy. Interestingly, EZH2 catalytic inhibition decreased stemness but increased migratory phenotypes of CRC cells with active AKT. Overall, we demonstrated that EZH2 modulates AKT-induced changes in gene expression through the AKT/EZH2/β-catenin axis in CRC. Our results suggest that EZH2 inhibitors have tumor-inhibiting and promoting effects in CRC as they inhibit EZH2-mediated methylation of histone and non-histone targets like β-catenin.
Project description:Occurrence of Colorectal cancer(CRC)is relevant with gut microbiota. However, role of IRF3, a key signaling mediator in innate immune sensing, has been barely investigated in CRC. Here, we unexpectedly found that the IRF3 deficient mice are hyper-susceptible to the development of intestinal tumor in AOM/DSS and Apcmin/+ models. Genetic ablation of IRF3 profoundly promotes the proliferation of intestinal epithelial cells via aberrantly activating Wnt signaling. Mechanically, IRF3 in resting state robustly associates with the active β-catenin in the cytoplasm, thus preventing its nuclear translocation and cell proliferation, which can be relieved upon microbe-induced activation of IRF3. In accordance, the survival of CRC is clinically correlated with the expression level of IRF3. Therefore, our study identifies IRF3 as a negative regulator of the Wnt/β-catenin pathway and a potential prognosis marker for Wnt-related tumorigenesis, and describes an intriguing link between gut microbiota and CRC via the IRF3-β-catenin axis.