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SPAG9-JAK2 gene expression array in Ba/F3 cells

ABSTRACT: SPAG9-JAK2 is a novel fusion gene identified in a pediatric patient with Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL). In this study, we performed functional analysis of the SPAG9-JAK2 fusion to establish molecular targeted therapy. Ba/F3 cells expressing SPAG9-JAK2 generated by retroviral transduction (Ba/F3-SPAG9-JAK2), proliferated in the absence of IL-3, and exhibited constitutive phosphorylation of the tyrosine residues in the JAK2 kinase domain of the fusion protein and STAT3/STAT5. Mutation of tyrosine residues in the JAK2 kinase domain (SPAG9-JAK2 mut) abolished IL-3 independence, but had no influence on STAT3/STAT5 phosphorylation levels. Gene expression analysis revealed that Stat1 was significantly up-regulated in Ba/F3-SPAG9-JAK2 cells. STAT1 was also phosphorylated in Ba/F3-SPAG9-JAK2 but not SPAG9-JAK2 mut cells, suggesting that STAT1 is key for SPAG9-JAK2-mediated cell proliferation. Consistently, STAT1 induced expression of the anti-apoptotic proteins, BCL-2 and MCL-1, as did SPAG9-JAK2, but not SPAG9-JAK2 mut. Ruxolitinib abrogated Ba/F3-SPAG9-JAK2-mediated proliferation in vitro, but was insufficient in vivo. Venetoclax (a BCL-2 inhibitor) or AZD5991 (an MCL-1 inhibitor) enhanced the effects of ruxolitinib on Ba/F3-SPAG9-JAK2 in vitro. These findings suggest that activation of the JAK2-STAT1-BCL-2/MCL-1 axis contributes to SPAG9-JAK2-related aberrant growth promotion. BCL-2 or MCL-1 inhibition is a potential therapeutic option for B-ALL with SPAG9-JAK2 fusion.

ORGANISM(S): Mus musculus

PROVIDER: GSE174578 | GEO | 2021/05/18

REPOSITORIES: GEO

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Project description:ETV6::FRK is a rare kinase-related fusion gene which was identified only in AML but not in ALL. Herein, we firstly identified ETV6::FRK fusion gene in a patient with pediatric B-ALL. Because FRK is Src family tyrosine kinase, we performed functional analysis of ETV6::FRK to establish molecular targeting therapy. Our case with B-ALL was refractory to conventional chemotherapy and received allogeneic bone marrow transplantation following administration of blinatumomab. Cytogenetic analysis demonstrated 46,XY,t(6;12)(q21;p13) and target capture mRNA sequencing revealed ETV6::FRK. Ba/F3 cells expressing ETV6::FRK generated by retroviral transduction (Ba/F3-ETV6::FRK) and analyzed for IL-3 independent growth. Gene expression analysis using whole transcriptome sequencing and gene set enrichment analysis (GSEA) was performed for comprehensive analysis of gene expression profile related to ETV6::FRK. It was also analyzed whether dasatinib, which is Src-kinase inhibitor, suppressed the growth of Ba/F3-ETV6::FRK in vitro and in vivo. Ba/F3-ETV6::FRK proliferated without IL-3, suggesting ETV6::FRK had proliferation activity. Western blot revealed that constitutive phosphorylation of tyrosine residue of ETV6::FRK and STAT3/STAT5, suggesting constitutive activation of FRK-STAT3/STAT5 pathway. GSEA of oncogenic gene sets (C6) from the GSEA Molecular Signatures Database revealed that, compared with control cells, Ba/F3-ETV6::FRK cells were enriched for up-regulation of SNF5 target genes and down-regulation of RB target genes involved in cell cycle regulation. In vitro killing assay showed that dasatinib killed efficiently Ba/F3-ETV6::FRK. Dasatinib also suppressed the growth of Ba/F3-ETV6::FRK in vivo and extended the survival time of the xenografted NSG mice. These findings suggest that activation of FRK-STAT3/STAT5 pathway contributes aberrant growth promotion of Ba/F3-ETV6::FRK. Our study demonstrated that dasatinib might be effective for the patient with B-ALL harboring ETV6::FRK.

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SPAG9-JAK2 gene expression array in Ba/F3 cells

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