Somatic mutation as a mechanism of Wnt/ -catenin pathway activation in CLL

Blood (Impact Factor: 10.45). 04/2014; 124(7). DOI: 10.1182/blood-2014-01-552067
Source: PubMed


One major goal of cancer genome sequencing is to identify key genes and pathways that drive tumor pathogenesis. While many studies have identified candidate driver genes based on recurrence of mutations in individual genes, subsets of genes with non-recurrent mutations may also be defined as putative drivers if they affect a single biological pathway. In this fashion, we previously identified Wnt signaling as significantly mutated through large-scale massively-parallel DNA sequencing of chronic lymphocytic leukemia (CLL). Here, we use a novel method of biomolecule delivery, vertical silicon nanowires, to efficiently introduce small interfering RNAs into CLL cells, and interrogate the effects of 8 of 15 mutated Wnt pathway members identified across 91 CLLs. In HEK293T cells, mutations in 2 genes did not generate functional changes, 3 led to dysregulated pathway activation, and 3 led to further activation or loss of repression of pathway activation. Silencing 4 of 8 mutated genes in CLL samples harboring the mutated alleles resulted in reduced viability compared to leukemia samples with wild-type alleles. We demonstrate that somatic mutations in CLL can generate dependence on this pathway for survival. These findings support the notion that non-recurrent mutations at different nodes of the Wnt pathway can contribute to leukemogenesis.

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Available from: Kristen Stevenson, Jan 15, 2016
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    ABSTRACT: In this issue of Blood, Wang et al demonstrate how mutations in the Wnt/beta-catenin pathway in chronic lymphocytic leukemia (CLL) lead to activation of this pathway. 1 The work presented demonstrates that this pathway is likely to contribute to CLL pathogenesis, at least in a subset of patients, and suggests that it may contain potential therapeutic targets. These observations are following the authors' groundbreaking work on the genetic landscape in CLL2,3 and by using exciting, novel transfection technology (ie, silicon nanowires).(4) Thus, the notoriously difficult-to-transfect CLL cells could be modified to be able to target a pathway that has been identified by indirect evidence from next generation sequencing, demonstrating that attacking the mutated proteins by genetic modification is feasible. Indeed, at least for some proteins tested, modification of the pathway on a number of levels led to changes in CLL behavior consistent with a role of the Wnt/b-catenin pathway in CLL pathogenesis. The paper must be read to fully appreciate the elegance of the approaches taken, as well as understand the potential limitations of the approach.
    Preview · Article · Aug 2014 · Blood
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    ABSTRACT: In spite of being the most prevalent adult leukemia in Western countries, the molecular mechanisms driving the establishment and progression of chronic lymphocytic leukemia (CLL) remain largely unknown. In recent years, the use of next-generation sequencing techniques has uncovered new and, in some cases, unexpected driver genes with prognostic and therapeutic value. The mutational landscape of CLL is characterized by high-genetic and epigenetic heterogeneity, low mutation recurrence and a long tail of cases with undefined driver genes. On the other hand, the use of deep sequencing has also revealed high intra-tumor heterogeneity and provided a detailed picture of clonal evolution processes. This phenomenon, in which aberrant DNA methylation can also participate, appears to be tightly associated to poor outcomes and chemo-refractoriness, thus providing a new subject for therapeutic intervention. Hence, and having in mind the limitations derived from the CLL complexity thus described, the application of massively parallel sequencing studies has unveiled a wealth of information that is expected to substantially improve patient staging schemes and CLL clinical management.
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    ABSTRACT: Recent research has shown that chronic lymphocytic leukemia (CLL) B-cells display a strong tendency to differentiate into antibody-secreting cells (ASCs) and thus may be amenable to differentiation therapy. However, the effect of this differentiation on factors associated with CLL pathogenesis has not been reported. In the present study, purified CLL B-cells were stimulated to differentiate into ASCs by phorbol myristate acetate or CpG oligodeoxynucleotide, in combination with CD40 ligand and cytokines in a two-step, seven-day culture system. We investigated (i) changes in the immunophenotypic, molecular, functional, morphological features associated with terminal differentiation into ASCs, (ii) the expression of factors involved in CLL pathogenesis, and (iii) the expression of pro-and anti-apoptotic proteins in the differentiated cells. Our results show that differentiated CLL B-cells are able to display the transcriptional program of ASCs. Differentiation leads to depletion of the malignant program and deregulation of the apoptosis/survival balance. Analysis of apoptosis and the cell cycle showed that differentiation is associated with low cell viability and a low rate of cell cycle entry. Our findings shed new light on the potential for differentiation therapy as a part of treatment strategies for CLL.
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