Activation of Rac1 and the exchange factor Vav3 are involved in NPM-ALK signaling in anaplastic large cell lymphomas [J]

INSERM, U563, Centre de Physiopathologie de Toulouse Purpan, Toulouse, France.
Oncogene (Impact Factor: 8.46). 05/2008; 27(19):2728-36. DOI: 10.1038/sj.onc.1210921
Source: PubMed


The majority of anaplastic large cell lymphomas (ALCLs) express the nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) fusion protein, which is oncogenic due to its constitutive tyrosine kinase activity. Transformation by NPM-ALK not only increases proliferation, but also modifies cell shape and motility in both lymphoid and fibroblastic cells. We report that the Rac1 GTPase, a known cytoskeletal regulator, is activated by NPM-ALK in ALCL cell lines (Karpas 299 and Cost) and transfected cells (lymphoid Ba/F3 cells, NIH-3T3 fibroblasts). We have identified Vav3 as one of the exchange factors involved in Rac1 activation. Stimulation of Vav3 and Rac1 by NPM-ALK is under the control of Src kinases. It involves formation of a signaling complex between NPM-ALK, pp60(c-src), Lyn and Vav3, in which Vav3 associates with tyrosine 343 of NPM-ALK via its SH2 domain. Moreover, Vav3 is phosphorylated in NPM-ALK positive biopsies from patients suffering from ALCL, demonstrating the pathological relevance of this observation. The use of Vav3-specific shRNA and a dominant negative Rac1 mutant demonstrates the central role of GTPases in NPM-ALK elicited motility and invasion.

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Available from: Damien Ramel, Sep 03, 2014
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    • "NPM-ALK is an oncogenic fusion protein, which acts as a constitutive active tyrosine kinase [36]. NPM-ALK signals in part through Rac1 thereby contributing to the pathogenesis of ALK-positive human lymphomas [34], [35]. Here, we present data indicating that NPM1 and Rac1 interact and reciprocally regulate each other. "
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    ABSTRACT: The Rac1 GTPase is a critical regulator of cytoskeletal dynamics and controls many biological processes, such as cell migration, cell-cell contacts, cellular growth and cell division. These complex processes are controlled by Rac1 signaling through effector proteins. We have previously identified several effector proteins of Rac1 that also act as Rac1 regulatory proteins, including caveolin-1 and PACSIN2. Here, we report that Rac1 interacts through its C-terminus with nucleophosmin1 (NPM1), a multifunctional nucleo-cytoplasmic shuttling protein with oncogenic properties. We show that Rac1 controls NPM1 subcellular localization. In cells expressing active Rac1, NPM1 translocates from the nucleus to the cytoplasm. In addition, Rac1 regulates the localization of the phosphorylated pool of NPM1 as this pool translocated from the nucleus to the cytosol in cells expressing activated Rac1. Conversely, we found that expression of NPM1 limits Rac1 GTP loading and cell spreading. In conclusion, this study identifies NPM1 as a novel, negative regulator of Rac1.
    Full-text · Article · Jul 2013 · PLoS ONE
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    • "RAC1 is a member of the Rho family of small GTPases and has been strongly implicated in tumorigenesis [43, 44]. It is involved in B-cell signaling through the CD40 receptor after activation of the RAS pathway [45] and was found to be activated in anaplastic large T-cell lymphomas [46]. RAC1 was shown to be a target of miR-142-3p in hepatocellular carcinoma cells [26]. "
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    ABSTRACT: MicroRNAs (miRNAs) are short 18-23 nucleotide long noncoding RNAs that posttranscriptionally regulate gene expression by binding to mRNA. Our previous miRNA profiling of diffuse large B-cell lymphoma (DLBCL) revealed a mutation in the seed sequence of miR-142-3p. Further analysis now showed that miR-142 was mutated in 11 (19.64%) of the 56 DLBCL cases. Of these, one case had a mutation in both alleles, with the remainder being heterozygous. Four mutations were found in the mature miR-142-5p, four in the mature miR-142-3p, and three mutations affected the miR-142 precursor. Two mutations in the seed sequence redirected miR-142-3p to the mRNA of the transcriptional repressor ZEB2 and one of them also targeted the ZEB1 mRNA. However, the other mutations in the mature miR-142-3p did not influence either the ZEB1 or ZEB2 3' untranslated region (3' UTR). On the other hand, the mutations affecting the seed sequence of miR-142-3p resulted in a loss of responsiveness in the 3' UTR of the known miR-142-3p targets RAC1 and ADCY9. In contrast to the mouse p300 gene, the human p300 gene was not found to be a target for miR-142-5p. In one case with a mutation of the precursor, we observed aberrant processing of the miR-142-5p. Our data suggest that the mutations in miR-142 probably lead to a loss rather than a gain of function. This is the first report describing mutations of a miRNA gene in a large percentage of a distinct lymphoma subtype.
    Full-text · Article · Oct 2012 · Cancer Medicine
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    • "NPM–ALK mediates cellular transformation by taking control of signaling pathways involved in proliferation (for example, adaptors, mitogen-activated protein kinases (MAPKs), phospholipase Cg, protein tyrosine phosphatases (PTPs) or pp60 cÀsrc ), and in survival or antiapoptotic functions (phosphatidylinositol 3-kinase, PI3K/Akt pathway, or the Jak/ signal transducer and activator of transcription protein (STAT3–5) module) (Chiarle et al., 2008). NPM– ALK( þ ) neoplasias are very aggressive and cells display a very distorted morphology with increased invasion capabilities resulting from modifications of the cytoskeleton dynamics through proteins such as p130Crk- associated substrate (p130Cas) and Rac1 guanosine triphosphate phosphatase (GTPase) (Ambrogio et al., 2005; Colomba et al., 2008). "
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    ABSTRACT: The chimera nucleophosmin-anaplastic lymphoma kinase (NPM-ALK), the tyrosine kinase activity of which is constitutively upregulated, is the causative agent of 75% of the anaplastic large-cell lymphomas (ALCLs). We have demonstrated that NPM-ALK induces the production of reactive oxygen species (ROS) by a pathway involving the arachidonic acid-metabolizing enzymes of the lipoxygenase (LOX) family. The use of the LOX inhibitor nordihydroguaiaretic acid (NDGA) and of the anti-oxidant N-acetylcysteine (NAC) demonstrated that ROS are important in maintaining the ALK kinase active. Consistent with this, NDGA treatment resulted in the inhibition of key pathways, such as Akt, signal transducer and activator of transcription factor 3 (STAT3) and extracellular signal-regulated kinase (ERK), which are involved in NPM-ALK antiapoptotic and pro-mitogenic functions. Conversely, the stress-activated kinase p38, described in some instances as a mediator of apoptosis, was activated. Interestingly, 5-LOX, an isoform involved in many cancers, was found to be activated in NPM-ALK(+) cells. Functional studies have shown that transforming properties, namely proliferation and resistance to apoptosis, were abrogated by treatment with either NDGA or the 5-LOX inhibitor (N-(3-phenoxycinnamyl)-acetohydroxamic acid) (BW A4C). Together, these data point to the ROS/LOX pathway as a potential new target for therapy in NPM-ALK-positive tumors.
    Preview · Article · Jul 2009 · Oncogene
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