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Single-cell transcriptomic analysis of two models of zebrafish beta-catenin-driven HCC

ABSTRACT: Up to 41% of hepatocellular carcinomas (HCCs) result from activating mutations in the CTNNB1 gene encoding β-catenin. β-catenin has dual cellular functions as a component of the Wnt signaling pathway and adherens junctions. HCC-associated CTNNB1 mutations stabilize the β-catenin protein, leading to nuclear and/or cytoplasmic localization of β-catenin and downstream activation of Wnt target genes. In patient HCC samples, β-catenin nuclear and cytoplasmic localization are typically patchy, even among HCC with highly active CTNNB1 mutations. The functional and clinical relevance of this heterogeneity in β-catenin activation are not well understood. To define mechanisms of β-catenin-driven HCC initiation, we generated a Cre-lox system that enabled switching on activated β-catenin in 1) a small number of hepatocytes in early development; or 2) the majority of hepatocytes in later development or adulthood. We discovered that switching on activated β-catenin in a subset of larval hepatocytes was sufficient to drive HCC initiation. To determine the role of Wnt/β-catenin signaling heterogeneity later in hepatocarcinogenesis, we performed RNA-seq analysis of zebrafish β-catenin-driven HCC. Ingenuity Pathway Analysis of differentially expressed genes in the Cre-lox HCC model revealed that “Cancer” and “Liver Tumor” categories were significantly altered, indicating transcriptional similarities with human HCC and other vertebrate HCC models. At the single-cell level, 2.9% to 15.2% of hepatocytes from zebrafish β-catenin-driven HCC expressed two or more of the Wnt target genes axin2, mtor, glula, myca, and wif1, indicating focal activation of Wnt signaling in established tumors. Thus, heterogeneous β-catenin activation drives HCC initiation and persists throughout hepatocarcinogenesis.

ORGANISM(S): Danio rerio

PROVIDER: GSE137784 | GEO | 2019/09/27

REPOSITORIES: GEO

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Project description:Background & Aims: Patients with beta-catenin (encoded by CTNNB1)-mutated hepatocellular carcinoma (HCC) have demonstrated limited clinical benefit to first-line immunotherapy (IO). Animal models of HCC expressing mutant-beta-catenin and additional aberrations via hydrodynamic tail vein injection with sleeping beauty transposon/transposase (SB-HDTVI) represent clinically relevant human HCC subsets. Here, we perform transcriptomic analysis on multiple beta-catenin-mutated and non-mutated HCC animal models to identify Mutated beta-catenin Gene Signature (MBGS) for HCC patient stratification for CTNNB1-mutations and IO response. Methods: We co-expressed in mice mutant-NFE2L2 and hMET +- mutant-CTNNB1 via SB-HDTVI and monitored for HCC development. Bulk RNA-sequencing was assessed for transcriptional differences between various beta-catenin-mutated and non-mutated models. MBGS was generated for predictive ability of CTNNB1 mutations and IO resistance in multiple HCC patient cohorts. Results: Co-expression of S45Y-beta-catenin + G31A-NFE2L2 + hMet (beta-N-M) resulted in HCC development by 4.5 weeks while co-expression of G31A-NFE2L2 + hMet (N-M) led to HCC by 14 weeks with tumors being positive for expected targets by immunohistochemistry (IHC). Bulk RNA-sequencing comparing beta-catenin-driven versus non-beta-catenin driven models yielded 95 common upregulated genes. Differential gene expression analysis of the common genes comparing CTNNB1-mutated vs non-mutated TCGA patients narrowed the gene panel to 13-(or 10-) genes. This MBGS predicted CTNNB1-mutation status in TCGA (n=374) and French (n=398) patient cohorts (with ROC AUC of 0.90 and 0.94). High MBGS expression was also associated with no overall and progression-free survival benefit when comparing atezolizumab + bevacizumab versus sorafenib arms in IMbrave150 cohort implying fewer treatment effects. Conclusions: In an era of patient molecular stratification for HCC, MBGS may aid in optimally selecting patients for IO through diagnosis of a molecular subset which lacks optimal response.

Project description:Medulloblastoma is the most frequent malignant pediatric brain tumor. Considerable efforts are dedicated to identify markers that help to refine treatment strategies. The activation of the Wnt/beta-catenin pathway occurs in 10-15% of medulloblastomas and has been recently described as a marker for favorable patient outcome. We report a series of 72 pediatric medulloblastomas evaluated for beta-catenin immunostaining, CTNNB1 mutations, and studied by comparative genomic hybridization. Gene expression profiles were also available in a subset of 40 cases. Immunostaining of beta-catenin showed extensive nuclear staining (>50% of the tumor cells) in 6 cases and focal nuclear staining (<10% of cells) in 3 cases. The other cases exhibited either a signal strictly limited to the cytoplasm (58 cases) or were negative (5 cases). CTNNB1 mutations were detected in all beta-catenin extensively nucleopositive cases. The expression profiles of these cases documented a strong activation of the Wnt/beta-catenin pathway. Remarkably, 5 out of these 6 tumors showed a complete loss of chromosome 6. In contrast, cases with focal nuclear beta-catenin staining, as well as tumors with negative or cytoplasmic staining, never demonstrated CTNNB1 mutation, Wnt/beta-catenin pathway activation or chromosome 6 loss. Patients with extensive nuclear staining were significantly older at diagnosis and were in continuous complete remission after a mean follow-up of 75.7 months (range 27.5-121.2) from diagnosis. All three patients with a focal nuclear staining of beta-catenin died within 36 months from diagnosis. Altogether, these data confirm and extend previous observations that CTNNB1-mutated tumors represent a distinct molecular subgroup of medulloblastomas with favorable outcome, indicating that therapy de-escalation should be considered. Yet, international consensus on the definition criteria of this distinct medulloblastoma subgroup should be achieved. A series of 72 pediatric medulloblastoma tumors has been studied at the genomic level (array-CGH), screened for CTNNB1 mutations and beta-catenin expression (immunohistochemistry). A subset of 40 tumor samples has been analyzed at the RNA expression level (Affymetrix HG U133 Plus 2.0). Correlations between the genomic data, the expression data, the mutational screening, the pathological classification and clinical data is presented in the study. note: aCGH data not submitted to GEO

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Single-cell transcriptomic analysis of two models of zebrafish beta-catenin-driven HCC

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