Activating mutations of G protein alpha subunits (Ga) occur in 4-5% of all human cancers1 but oncogenic alterations in beta subunits (Gb) have not been defined. Here we demonstrate that recurrent mutations in the Gb proteins GNB1 and GNB2 confer cytokine-independent growth and activate canonical G protein signaling. Multiple mutations in GNB1 affect the protein interface that binds Ga subunits as well as downstream effectors, and disrupt Ga-Gbg interactions. Different mutations in Gb proteins clustered to some extent based on lineage; for example, all eleven GNB1 K57 mutations were in myeloid neoplasms while 6 of 7 GNB1 I80 mutations were in B cell neoplasms. Expression of patient-derived GNB1 alleles in Cdkn2a-deficient bone marrow followed by transplantation resulted in either myeloid or B cell malignancies. In vivo treatment with the dual PI3K/mTOR inhibitor BEZ235 suppressed GNB1-induced signaling and markedly increased survival. In several human tumors, GNB1 mutations co-occurred with oncogenic kinase alterations, including BCR/ABL, JAK2 V617F and BRAF V600K. Co-expression of patient-derived GNB1 alleles with these mutant kinases resulted in inhibitor resistance in each context. Thus, GNB1 and GNB2 mutations confer transformed and resistance phenotypes across a range of human tumors and may be targetable with inhibitors of G protein signaling.
Mutations in G protein β subunits promote transformation and kinase inhibitor resistance.
Cell line, Time
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Triplication of a 21q22 region contributes to B cell transformation through HMGN1 overexpression and loss of histone H3 Lys27 trimethylation.
Specimen part
View SamplesChildren with Down syndrome (DS) have a 20-fold increased risk of developing B cell acute lymphoblastic leukemia (B-ALL). Polysomy 21 (i.e., extra copies of chr.21) is also the most frequent somatic aneuploidy among all B-ALLs. Additional B-ALLs harbor intrachromosomal amplifications of chr.21q22 (iAMP21). Yet, the mechanistic links between chr.21q22 triplication and B-ALL remain undefined. Here we show that germline triplication of only 31 genes orthologous to human chr.21q22 is sufficient to confer murine B cell self-renewal in vitro, B cell maturation defects in vivo, and B-ALL in concert with either BCR-ABL or CRLF2 with activated JAK2. Chr.21q22 triplication suppresses H3K27me3 in murine progenitor B cells and B-ALLs, and bivalent genes with both H3K27me3 and H3K4me3 at their promoters in wild-type progenitor B cells are preferentially overexpressed in triplicated cells. Strikingly, human B-ALLs with polysomy 21 are distinguished by their overexpression of genes known to be marked with H3K27me3 in multiple cell types. Finally, overexpression of HMGN1, a nucleosome remodeling protein encoded on chr.21q22, suppresses H3K27me3 and promotes both B cell proliferation in vitro and B-ALL in vivo. These data implicate HMGN1 overexpression and loss of H3K27me3 in progenitor B cell transformation and suggest strategies to target leukemias with polysomy 21.
Triplication of a 21q22 region contributes to B cell transformation through HMGN1 overexpression and loss of histone H3 Lys27 trimethylation.
No sample metadata fields
View SamplesHematopoietic stem and progenitor cells (Lineagelo ScaI+ c-Kit+) were sorted 4 weeks post pIpC injection. RNA was extracted using TRIZOL and RNEASY RNA extraction kit. RNA was then amplified using NUGEN Pico amplification kit, fragmented and hybridized on Mouse Expression Array 430 2.0. Signal normalization was performed by RMA method. Data were analyzed using GSEA across the complete list of genes ranked by signal-to-noise ratio.
Musashi-2 controls cell fate, lineage bias, and TGF-β signaling in HSCs.
Specimen part
View SamplesLeukemia stem cells (LSCs) are found in most aggressive myeloid diseases and contribute to therapeutic resistance. Genetic and epigenetic alterations cause a dysregulated developmental program in leukemia. The MSI2 RNA binding protein has been previously shown to predict poor survival in leukemia. We demonstrate that the conditional deletion of Msi2 results in delayed leukemogenesis, reduced disease burden and a loss of LSC function. Gene expression profiling of the Msi2 ablated LSCs demonstrates a loss of the HSC/LSC and an increase in the differentiation program. The gene signature from the Msi2 deleted LSCs correlates with survival in AML patients. MSI2’s maintains the MLL self-renewal program by interacting with and retaining efficient translation of Hoxa9, Myc and Ikzf2. We further demonstrate that shRNA depletion of the MLL target gene Ikzf2 also contributes to MLL leukemia cell survival. Our data provides evidence that MSI2 controls efficient translation of the oncogenic LSC self-renewal program and a rationale for clinically targeting MSI2 in myeloid leukemia. Overall design: RNA-Seq was performed on sorted c-Kit high leukemic cells from 2 Msi2 -/- and 2 Msi2 f/f mice.
Musashi2 sustains the mixed-lineage leukemia-driven stem cell regulatory program.
No sample metadata fields
View SamplesAnalysis of musashi2 contribution towards maintaing myelodysplastic phenotype in stem cells. We find that musashi2 plays an integral role in maintaining the myelodysplastic phenotype Overall design: Control, NUP98-HOXD13; NHD13, NHD13/MSI2 bone marrow was transplated allowed to engraft into lethally irradiated congenic CD45.1 animals. Mice were then fed doxycycline to induce MSI2 overexpression. Mice were induced for 3 months and then CD45.2 Lineage lo Sca1+ and Kit+ cells were sorted and then assessed for gene expression.
MSI2 is required for maintaining activated myelodysplastic syndrome stem cells.
Age, Specimen part, Cell line, Subject
View SamplesMalignant rhabdoid tumors (MRT) are highly aggressive pediatric cancers that respond poorly to current therapies. We screened several MRT cell lines each with large-scale RNAi, CRISPR-Cas9, and small-molecule libraries to identify potential drug targets specific for these cancers. We discovered MDM2 and MDM4, the canonical negative regulators of p53, as significant vulnerabilities. Using two compounds currently in clinical development, idasanutlin and ATSP-7041, we show that MRT cells are more sensitive than other p53 wild-type cancer cell lines to MDM2 and dual MDM2/4 inhibition in vitro. These compounds cause significant upregulation of the p53 pathway in MRT cells, and sensitivity is ablated by CRISPR-Cas9-mediated inactivation of TP53. We show that loss of SMARCB1, a subunit of the SWI/SNF (BAF) complex mutated in nearly all MRT, sensitizes cells to MDM2 and MDM2/4 inhibition by enhancing p53-mediated apoptosis. Both MDM2 and MDM2/4 inhibition slowed MRT xenograft growth in vivo, with a five-day idasanutlin pulse causing marked regression of all xenografts including durable complete responses in 50% of mice. Together, these studies identify a genetic connection between mutations in the SWI/SNF chromatin-remodeling complex and the tumor suppressor gene p53, and provide preclinical evidence to support the targeting of MDM2 and MDM4 in this often-fatal pediatric cancer. Overall design: RNA-seq in TTC642 MRT cells treated with idasanutlin compared to DMSO
MDM2 and MDM4 Are Therapeutic Vulnerabilities in Malignant Rhabdoid Tumors.
Specimen part, Subject
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Functional screen of MSI2 interactors identifies an essential role for SYNCRIP in myeloid leukemia stem cells.
Specimen part, Cell line
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