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?-Catenin is required for intrinsic but not extrinsic BCR-ABL1 kinase-independent resistance to tyrosine kinase inhibitors in chronic myeloid leukemia.

ABSTRACT: Activation of nuclear ?-catenin and expression of its transcriptional targets promotes chronic myeloid leukemia (CML) progression, tyrosine kinase inhibitor (TKI) resistance, and leukemic stem cell self-renewal. We report that nuclear ?-catenin has a role in leukemia cell-intrinsic but not -extrinsic BCR-ABL1 kinase-independent TKI resistance. Upon imatinib inhibition of BCR-ABL1 kinase activity, ?-catenin expression was maintained in intrinsically resistant cells grown in suspension culture and sensitive cells cultured in direct contact (DC) with bone marrow (BM) stromal cells. Thus, TKI resistance uncouples ?-catenin expression from BCR-ABL1 kinase activity. In ?-catenin reporter assays, intrinsically resistant cells showed increased transcriptional activity versus parental TKI-sensitive controls, and this was associated with restored expression of ?-catenin target genes. In contrast, DC with BM stromal cells promoted TKI resistance, but had little effects on Lef/Tcf reporter activity and no consistent effects on cytoplasmic ?-catenin levels, arguing against a role for ?-catenin in extrinsic TKI resistance. N-cadherin or H-cadherin blocking antibodies abrogated DC-based resistance despite increasing Lef/Tcf reporter activity, suggesting that factors other than ?-catenin contribute to extrinsic, BM-derived TKI resistance. Our data indicate that, while nuclear ?-catenin enhances survival of intrinsically TKI-resistant CML progenitors, it is not required for extrinsic resistance mediated by the BM microenvironment.

SUBMITTER: Eiring AM

PROVIDER: S-EPMC4675686 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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β-Catenin is required for intrinsic but not extrinsic BCR-ABL1 kinase-independent resistance to tyrosine kinase inhibitors in chronic myeloid leukemia.

Eiring A M AM Khorashad J S JS Anderson D J DJ Yu F F Redwine H M HM Mason C C CC Reynolds K R KR Clair P M PM Gantz K C KC Zhang T Y TY Pomicter A D AD Kraft I L IL Bowler A D AD Johnson K K Partlin M Mac MM O'Hare T T Deininger M W MW

Leukemia 20150723 12

Activation of nuclear β-catenin and expression of its transcriptional targets promotes chronic myeloid leukemia (CML) progression, tyrosine kinase inhibitor (TKI) resistance, and leukemic stem cell self-renewal. We report that nuclear β-catenin has a role in leukemia cell-intrinsic but not -extrinsic BCR-ABL1 kinase-independent TKI resistance. Upon imatinib inhibition of BCR-ABL1 kinase activity, β-catenin expression was maintained in intrinsically resistant cells grown in suspension culture and ...[more]

PMID: 26202934

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Project description:BackgroundIt is difficult for chronic myeloid leukemia (CML) patients with BCR::ABL1 independent drug resistance to achieve optimal efficacy. The aim of this study is to investigate the BCR::ABL1 kinase independent mechanism of tyrosine kinase inhibitor (TKI) resistance in CML patients to develop targeted therapeutic strategy.MethodsHerein, we analyzed the long non-coding RNA (lncRNA) and messenger RNA (mRNA) expression profiles of patients who achieved sustained deep molecular response (DMR) after TKI treatment and patients with non-DMR using RNA-seqencing. Furthermore, the differentially expressed lncRNAs and mRNAs were identified. The expression of chosen lncRNA was validated in an expanded cohort, and bioinformatics analysis was performed to analyze the function of selected mRNA.ResultsLncRNA data analysis indicated the diversity lncRNA profiles among healthy individuals, CML patients with non-DMR, and CML patients with DMR. Differential expression analysis and Veen plot of up-regulated lncRNAs in patients with non-DMR (compared with healthy individuals) and down-regulated lncRNAs in patients with DMR (compared to patients with non-DMR) revealed that lncRNA CBR3-AS1 overexpression might be related to BCR::ABL1 independent TKI resistance of CML patients. The expression of CBR3-AS1 was then verified in an expanded cohort, suggesting that, compared with control group, there was no statistical difference of CBR3-AS1 expression in DMR group, whereas, CBR3-AS1 was up-regulated in non-DMR group. Moreover, the mRNA data analysis of RNA-sequencing was performed. We considered genes that up-regulated in non-DMR group (compared with control group), down-regulated in DMR group (compared with non-DMR group), showed no statistical difference between control and DMR group as the potential genes that associated with TKI resistance of CML patients. A total of 55 corresponding mRNAs were obtained including KCNA6, a target gene of CBR3-AS1. Further bioinformatics analysis showed that the major interacted genes of KCNA6 were enriched in several resistance-associated pathways including interleukin -17 signaling pathway and cyclic adenosine monophosphate signaling pathway.ConclusionsIn conclusion, this work indicates that CBR3-AS1 might be involved in BCR::ABL1 independent TKI resistance of CML patients through targeting KCNA6, providing a novel target for intervention treatment of CML patients with BCR::ABL1 independent TKI resistance.

Project description:Beta Catenin signaling is critical for the self-renewal of leukemic stem cells in chronic myeloid leukemia. It is driven by multiple events, enhancing beta catenin stability and promoting its transcriptional co-activating function. We investigated the impact of BCR-ABL1 on Chibby1, a beta catenin antagonist involved in cell differentiation and transformation. Relative proximity of the Chibby1 encoding gene (C22orf2) on chromosome 22q12 to the BCR breakpoint (22q11) lets assume its involvement in beta catenin activation in chronic myeloid leukemia as a consequence of deletions of distal BCR sequences encompassing one C22orf2 allele. Forty patients with chronic myeloid leukemia in chronic phase were analyzed for C22orf2 relocation and Chibby1 expression. Fluorescent in situ hybridization analyses established that the entire C22orf2 follows BCR regardless of chromosomes involved in the translocation. In differentiated hematopoietic progenitors (bone marrow mononuclear cell fractions) of 30/40 patients, the expression of Chibby1 protein was reduced below 50% of the reference value (peripheral blood mononuclear cell fractions of healthy persons). In such cell context, Chibby1 protein reduction is not dependent on C22orf2 transcriptional downmodulation; however, it is strictly dependent upon BCR-ABL1 expression because it was not observed at the moment of major molecular response under tyrosine kinase inhibitor therapy. Moreover, it was not correlated with the disease prognosis or response to therapy. Most importantly, a remarkable Chibby1 reduction was apparent in a putative BCR-ABL1+ leukemic stem cell compartment identified by a CD34+ phenotype compared to more differentiated hematopoietic progenitors. In CD34+ cells, Chibby1 reduction arises from transcriptional events and is driven by C22orf2 promoter hypermethylation. These results advance low Chibby1 expression associated with BCR-ABL1 as a component of beta catenin signaling in leukemic stem cells.

Dataset Information

?-Catenin is required for intrinsic but not extrinsic BCR-ABL1 kinase-independent resistance to tyrosine kinase inhibitors in chronic myeloid leukemia.

Publications

β-Catenin is required for intrinsic but not extrinsic BCR-ABL1 kinase-independent resistance to tyrosine kinase inhibitors in chronic myeloid leukemia.

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