Project description:The FBXW7 tumour suppressor is commonly mutated, deleted or hypermethylated in a variety of cancer histologies. The tumour suppressive role of the FBXW7 protein has been ascribed to its ability to drive the ubiquitination and degradation of oncoproteins via its role as a substrate recognition subunit of SCF complexes that mediate E3 ubiquitin ligation. Despite this molecular understanding, therapeutic approaches that target tumoural FBXW7 defects do not exist. To identify candidate vulnerabilities put in place by FBXW7 dysfunction, we carried out genome-wide CRISPR-Cas9 screens, focussed RNA interference screens and whole proteome mass spectrometry profiling in multiple FBXW7 wild type and defective isogenic cell systems. These identified candidate FBXW7 synthetic lethal effects, including those involving SCF-related proteins (e.g. CAND1), proteins involved in the response to replication fork stress (ATR, RAD9A and CHEK1) and also proteins involved in replication licencing such as CDC7 and its substrate GINS4. The ATR, CHEK1 and CDC7 synthetic lethal effects were confirmed using drug-like small molecule inhibitors. Integration of proteomic profiling data indicated that FBXW7 defective cells express elevated levels of the replication factor RIF1. Functional experiments showed that FBXW7 vs. CDC7 synthetic lethality is RIF1 dependent and explained by RIF1 being required for CDC7 inhibitor-induced replication fork stalling. The delineation of FBXW7 synthetic lethal effects we describe here could serve as the starting point for subsequent drug discovery and/or development in this area.
Project description:Purpose: FBXW7 is one of the most frequently mutated tumor suppressors, the deficiency of which has been associated with resistance to some anticancer therapies. Through bioinformatic analyses and genome-wide CRISPR screens, we here reveal that FBXW7 deficiency leads to multi-drug resistance (MDR), to a bigger extent than well-established MDR-drivers such as ABCB1. Proteomic data from FBXW7-deficient cells and human cancer samples identify the upregulation of mitochondrial function as a hallmark of FBXW7 deficiency, which has been previously linked to an increased resistance to chemotherapy. Accordingly, genetic or chemical targeting of mitochondria is preferentially toxic for FBXW7-deficient cells. For instance, targeting mitochondrial translation with the antibiotic Tigecycline efficiently kills FBXW7-deficient cells in vitro and in vivo, by a mechanism that involves activation of the Integrated Stress Response (ISR). Searching for additional drugs that overcome MDR in FBXW7-deficient cells, we found several targeted therapies such as Erlotinib, Dasatinib or Vemurafenib which unexpectedly also activate the ISR. Together, our study reveals that one of the most frequent mutations in cancer reduces the sensitivity to the vast majority of available therapies, and identifies a general principle to overcome such resistance. Methods: This study was performed in 2 groups of DLD1 cells with duplicate samples per group. Both control (Wild Type, WT) and experimental (FBXW7 -/-, KO) were exposed to Tigecycline (10µM). DMSO was used as a control for the treatment. After 24h, the RNA was extracted and the transcriptome was profiled with RNA-Sequencing (RNA-seq) analysis. Results: our study reveals that one of the most frequent mutations in cancer reduces the sensitivity to the vast majority of available therapies, and identifies a general principle to overcome such resistance.
Project description:A genome-wide CRISPR screen was combined with a tdTomato reporter-based epigenetic memory assay to identify factors that erase epigenetic memory in ESC. After introducing genome wide perturbation and dCas9::KRAB-mediated epigenetic editing of the Esg1-tdTomato reporter, the trigger was released and cells that maintained the silencing sorted at FACS. Samples were collected out of sorted tdTomato negative (TOMminus) and positive (TOMplus) cells after 6 days of DOX treatment (epigenetic editing) and 3 or 7 days of DOX washout (release of the trigger), using a gating strategy to separate the bottom 2.5% negative cells (2.5%gate) and cells ranging from mildly to fully repressed (widegate).
Project description:We assessed the role of the E3 ligase FBXW7 in mature B-cell neoplasms. This experiment assesses the role of the FBXW7-KMT2D axis in regulating gene expression in OPM-1 cells.
Project description:Fbxw7 is a tumor supressor frequently mutated in endometrial cancer. To analyze the signaling pathways that can be altered by Fbxw7 we compared RNA expression in the presence or absence of Fbxw7 in mouse endometrial cancer cells deficient for Fbxw7 and Pten.
Project description:FBXW7 loss-of-function has been implicated in chemoresistance against antimicrotubule drugs. FBXW7 is frequently mutated in human cancers and the identification of FBXW7 substrates, which could be involved in this phenotype, is a major task.
Project description:We used gene transcript profiling to gain a deeper understanding of the role of FBXW7 in tumor development and to determine the influence of mTOR inhibition by rapamycin on tumor transcriptome and biological functions. In comparison to tumors from p53 single heterozygous (p53+/-) mice, we find that tumors from Fbxw7/p53 double heterozygous (Fbxw7+/-p53+/-) mice show significant deregulation of cholesterol metabolic processes independent of rapamycin treatment, while cell cycle related genes were upregulated in tumors from placebo treated Fbxw7+/-p53+/- mice, but not in tumors from rapamycin treated Fbxw7+/-p53+/- mice. On the other hand, tumors from rapamycin treated Fbxw7+/-p53+/- mice were enriched for genes involved in the integrated stress response, an adaptive mechanism to survive in stressful environments. p53+/â and p53+/âFbxw7+/â mice were generated by crossing p53-/- mice with Fbxw7+/- mice. At 5 weeks of age, mice were exposed whole-body to a single dose of 4 Gy X-ray irradiation. Mice were divided randomly into two groups and treated with rapamycin or placebo. RNA was isolated from thymic lymphomas.
Project description:FBXW7 is one of the most frequently mutated tumor suppressors, the deficiency of which has been associated with resistance to some anticancer therapies. Through bioinformatic analyses and genome-wide CRISPR screens, we here reveal that FBXW7 deficiency leads to multi-drug resistance (MDR), to a bigger extent than well-established MDR-drivers such as ABCB1. Proteomic data from FBXW7-deficient cells and human cancer samples identify the upregulation of mitochondrial function as a hallmark of FBXW7 deficiency, which has been previously linked to an increased resistance to chemotherapy. Accordingly, genetic or chemical targeting of mitochondria is preferentially toxic for FBXW7-deficient cells. For instance, targeting mitochondrial translation with the antibiotic Tigecycline efficiently kills FBXW7-deficient cells in vitro and in vivo, by a mechanism that involves activation of the Integrated Stress Response (ISR). Searching for additional drugs that overcome MDR in FBXW7-deficient cells, we found several targeted therapies such as Erlotinib, Dasatinib or Vemurafenib which unexpectedly also activate the ISR. Together, our study reveals that one of the most frequent mutations in cancer reduces the sensitivity to the vast majority of available therapies, and identifies a general principle to overcome such resistance.
Project description:Following a CRISPR enhancer scan covering the GATA2 super-enhancer region, the top sgRNAs were selected for further inspection. MUTZ3 cells were thus treated with the selected sgRNAs and the region of interested was subjected to amplicons sequencing (amplicon-seq). To that end, we used the Illumina PCR-based custom amplicon sequencing method using the TruSeq Custom Amplicon index kit (Illumina). The same experiment was conducted in K562 cells, which do not harbor an inv(3)/t(3;3), to investigate the role of MYB in this enhancer in other leukemia settings