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Nuclear Vav3 is required for canonical PRC1 activity in B-cell lymphoblastic leukemogenesis (CUT&RUN)

ABSTRACT: Acute B-cell lymphoblastic leukemia (B-ALL) represents a multiclonal evolution of B-cell progenitors endowed with both tumor-initiating and propagating properties. We have previously shown that the concurrent overexpression and activation of both the Rac guanine nucleotide exchange factor (RacGEF) Vav3 and Rac GTPases is required for BCR-ABL-mediated leukemogenesis. Here, we show that upon BCR-ABL expression, Vav3 expression becomes predominantly nuclear. In this location, Vav2 interacts with BCR-ABL, Rac, and the canonical polycomb repression complex proteins Bmi1, Ring1b and Ezh2. The GEF activity of Vav3 is required for B-cell proliferation and Bmi1-dependent B-cell progenitor self-renewal, nuclear Rac activation, protein interaction with Bmi1, H2A(K119) mono-ubiquitination (H2AK119Ub), and repression of downstream target loci. Vav3 deficiency results in de-repression and repression of loci encoding negative regulators of cell proliferation and oncogenic transcriptional factors, respectively. Mechanistically, we show that Vav3 prevents the Phlpp2-sensitive and Akt (S473)-dependent phosphorylation of Bmi1 on the regulatory residue S314 that, in turn, promotes the transcriptional factor reprogramming of leukemic B-cell progenitors. These results highlight the importance of non-canonical nuclear Rho GTPase signaling in leukemogenesis.

ORGANISM(S): Mus musculus

PROVIDER: GSE196375 | GEO | 2022/04/16

REPOSITORIES: GEO

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Project description:The guanosine triphosphatases of the Rho and Rac subfamilies regulate protumorigenic pathways and are activated by guanine nucleotide exchange factors (Rho GEFs), which could be potential targets for anticancer therapies. We report that two Rho GEFs, Vav2 and Vav3, play synergistic roles in breast cancer by sustaining tumor growth, neoangiogenesis, and many of the steps involved in lung-specific metastasis. The involvement of Vav proteins in these processes did not correlate with Rac1 and RhoA activity or cell migration, implying the presence of additional biological programs. Microarray analyses revealed that Vav2 and Vav3 controlled a vast transcriptional program in breast cancer cells through mechanisms that were shared between the two proteins, isoform-specific or synergistic. Furthermore, the abundance of Vav regulated transcripts was modulated by Rac1-dependent and Rac1-independent pathways. This transcriptome encoded therapeutically targetable proteins that played non redundant roles in primary tumorigenesis and lung-specific metastasis, such as integrin-linked kinase (Ilk), the transforming growth factorM-bM-^@M-^Sb family ligand inhibin bA, cyclooxygenase-2, and the epithelial cell adhesion molecule Tacstd2. It also contained gene signatures that predicted disease outcome in breast cancer patients. These results identify possible targets for treating breast cancer and lung metastases and provide a potential diagnostic tool for clinical use. All microarray experiments were performed by the personnel of the Genomics and Proteomics Unit of our Institution. Transcriptomal changes were determined using the Mouse Gene 1.0 ST arrays (Affymetrix). Two independent experiments were performed to identify the Vav2/Vav3-dependent transcriptome. In the first one, we compared the transcriptomes of Control, KD2/3(A) and KD2/3(B) to identify Vav family-dependent genes. In the second one, we compared the transcriptomes of KD2/3(A) and KD2/3+V2/3 cells. In all cases, total cellular RNA was extracted from three independent exponential cultures of the appropriate cell lines using the RNAeasy kit (Qiagen), quantified using 6000 Nano Chips (Agilent Technologies, Santa Clara, CA), and used (2.3 M-NM-<g/sample) to generated labeled cRNA probes according to the manufacturerM-bM-^@M-^Ys instructions (Affymetrix). Upon microarray hybridization, the raw data was normalized, filtered and analyzed with the Bioconductor software (www.bioconductor.com) using the Affy and Siggenes applications. Generation of knockdown cell lines. The shRNA-mediated knockdown of transcripts for Vav2 and Vav3 was carried out using already packaged Mission TRC lentiviral particles (Sigma-Aldrich) according to the manufacturerM-bM-^@M-^Ys protocol. The catalogue numbers and shRNA sequences yielding the greatest knockdown were clone number TRC0000097094 (5M-bM-^@M-^Y-CCGGGCCTGCATCTCTGGTTTAGATCTCGAGATCTAA ACCAGAGATGCAGGCTTTTTG-3M-bM-^@M-^Y) for the mouse Vav2 mRNA; TRC0000097124 (5M-bM-^@M-^Y-CCGGCCAGCATTTCTCGTCTTAAATCTCGAGATTTAA GACGAGAAATGCTGGTTTTTG-3M-bM-^@M-^Y) for the mouse Vav3 mRNA. Lentiviral particles containing the empty pLOK.1puro vector (Sigma-Aldrich) were used to generate the M-bM-^@M-^\ControlM-bM-^@M-^] 4T1 cells used in these experiments. Cells were incubated with lentiviral particles in the presence of 8 M-NM-<g/ml polybrene (Sigma), selected with puromycin (1 M-NM-<g/ml; Sigma), and used as either pools or isolated clones. Two clones of double Vav2;Vav3 knockdown cells (designated KD2/A(A) and KD2/3 (B)) were used in these experiments. Generation of rescued 4T1 cell lines. To generate the rescued KD2/3(A) cell line expressing both Vav2 and Vav3, cells were first infected with lentiviral particles produced from the pCCM33 vector (encoding wild type, HA-tagged Vav2) and then with lentiviral particles containing the pCQS1 vector (encoding wild type, Myc-tagged Vav3). Cells were then selected with hygromycin (present in the Vav2-encoding pCCM33 vector) and susbsequently sorted by flow cytometry to isolate GFP positive cells (which was expressed bicistronically from the same Vav3-encoding pCQS1 vector). A clone of double reconstituted cells was used in the microarray experiments and designated as KD2/3+V2/V3.

Project description:MiR-142 is dynamically expressed and plays a regulatory role in hematopoiesis. Based on the simple observation that miR-142 levels are significantly lower in CD34+CD38- cells from blast crisis (BC) chronic myeloid leukemia (CML). CML patients compared with chronic phase (CP) CML patients (p=0.002), we hypothesized that miR-142 deficit plays a role in BC transformation. To test this hypothesis, we generated a miR-142 KO BCR-ABL (i.e., miR-142−/−BCR-ABL) mouse by crossing a miR-142−/− mouse with a miR-142+/+BCR-ABL mouse. While the miR-142+/+BCR-ABL mice developed and died of CP CML, the miR-142−/−BCR-ABL mice developed a BC-like phenotype in the absence of any other acquired gene mutations and died significantly sooner than miR-142+/+BCR-ABL CP controls (p=0.001). Leukemic stem cell (LSC)-enriched Lineage-Sca-1+c-Kit+ cells (LSKs) from diseased miR-142−/−BCR-ABL mice transplanted into congenic recipients, recapitulated the BC features thereby suggesting stable transformation of CP-LSCs into BC-LSCs in the miR-142 KO CML mouse. Single cell (sc) RNA-seq profiling showed that miR-142 deficit changed the cellular landscape of the miR-142−/−BCR-ABL LSKs compared with miR-142+/+BCR-ABL LSKs with expansion of myeloid-primed and loss of lymphoid-primed factions. Bulk RNA-seq analyses along with unbiased metabolomic profiling and functional metabolic assays demonstrated enhanced fatty acid β-oxidation (FAO) and oxidative phosphorylation (OxPhos) in miR-142−/−BCR-ABL LSKs vs miR-142+/+BCR-ABL LSKs. MiR-142 deficit enhanced FAO in miR-142−/−BCR-ABL LSKs by increasing the expression of CPT1A and CPT1B, that controls the cytosol-to-mitochondrial acyl-carnitine transport, a critical step in FAO. MiR-142 deficit also enhanced OxPhos in miR-142−/−BCR-ABL LSKs by increasing mitochondrial fusion and activity. As the homeostasis and activity of LSCs depend on higher levels of these oxidative metabolism processes, we then postulate that miR-142 deficit is a potentially druggable target for BC-LSCs. To this end, we developed a novel CpG-miR-142 mimic oligonucleotide (ODN; i.e., CpG-M-miR-142) that corrected the miR-142 deficit and alone or in combination with a tyrosine kinase inhibitor (TKI) significantly reduced LSC burden and prolonged survival of miR-142−/−BCR-ABL mice. The results from murine models were validated in BC CD34+CD38- primary blasts and patient-derived xenografts (PDXs). In conclusion, an acquired miR-142 deficit sufficed in transforming CP-LSCs into BC-LSCs, via enhancement of bioenergetic oxidative metabolism in absence of any additional gene mutations, and likely represent a novel therapeutic target in BC CML.

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Nuclear Vav3 is required for canonical PRC1 activity in B-cell lymphoblastic leukemogenesis (CUT&RUN)

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