Targeted disruption of the BCR-ABL fusion gene by Cas9/dual-sgRNA inhibits proliferation and induces apoptosis in chronic myeloid leukemia cells.

The BCR-ABL fusion gene, formed by the fusion of the breakpoint cluster region protein ( BCR) and the Abl Oncogene 1, Receptor Tyrosine Kinase ( ABL) genes, encodes the BCR-ABL oncoprotein, which plays a crucial role in leukemogenesis. Current therapies have limited efficacy in patients with chronic myeloid leukemia (CML) because of drug resistance or disease relapse. Identification of novel strategies to treat CML is essential. This study aims to explore the efficiency of novel CRISPR-associated protein 9 (Cas9)/dual-single guide RNA (sgRNA)-mediated disruption of the BCR-ABL fusion gene by targeting BCR and cABL introns. A co-expression vector for Cas9 green fluorescent protein (GFP)/dual-BA-sgRNA targeting BCR and cABL introns is constructed to produce lentivirus to affect BCR-ABL expression in CML cells. The effects of dual-sgRNA virus-mediated disruption of BCR-ABL are analyzed via the use of a genomic sequence and at the protein expression level. Cell proliferation, cell clonogenic ability, and cell apoptosis are assessed after dual sgRNA virus infection, and phosphorylated BCR-ABL and its downstream signaling molecules are detected. These effects are further confirmed in a CML mouse model via tail vein injection of Cas9-GFP/dual-BA-sgRNA virus-infected cells and in primary cells isolated from patients with CML. Cas9-GFP/dual-BA-sgRNA efficiently disrupts BCR-ABL at the genomic sequence and gene expression levels in leukemia cells, leading to blockade of the BCR-ABL tyrosine kinase signaling pathway and disruption of its downstream molecules, followed by cell proliferation inhibition and cell apoptosis induction. This method prolongs the lifespan of CML model mice. Furthermore, the effect is confirmed in primary cells derived from patients with CML.

Evolution of TP53 abnormalities during CLL disease course is associated with telomere length changes.

BACKGROUND: Telomeres are protective structures at chromosome ends which shorten gradually with increasing age. In chronic lymphocytic leukemia (CLL), short telomeres have been associated with unfavorable disease outcome, but the link between clonal evolution and telomere shortening remains unresolved. METHODS: We investigated relative telomere length (RTL) in a well-characterized cohort of 198 CLL patients by qPCR and focused in detail on a subgroup 26 patients who underwent clonal evolution of TP53 mutations (evolTP53). In the evolTP53 subgroup we explored factors influencing clonal evolution and corresponding changes in telomere length through measurements of telomerase expression, lymphocyte doubling time, and BCR signaling activity. RESULTS: At baseline, RTL of the evolTP53 patients was scattered across the entire RTL spectrum observed in our CLL cohort. RTL changed in the follow-up samples of 16/26 (62%) evolTP53 cases, inclining to reach intermediate RTL values, i.e., longer telomeres shortened compared to baseline while shorter ones prolonged. For the first time we show that TP53 clonal shifts are linked to RTL change, including unexpected RTL prolongation. We further investigated parameters associated with RTL changes. Unstable telomeres were significantly more frequent among younger patients (P = 0.032). Shorter telomeres were associated with decreased activity of the B-cell receptor signaling components p-ERK1/2, p-ZAP-70/SYK, and p-NFκB (P = 0.04, P = 0.01, and P = 0.02, respectively). CONCLUSIONS: Our study revealed that changes of telomere length reflect evolution in leukemic subclone proportion, and are associated with specific clinico-biological features of the explored cohort.

Identification of putative genetic variants in major depressive disorder patients in Pakistan.

BACKGROUND: Major depressive disorder (MDD) is a polygenic, and highly prevalent disorder affecting 322 million people globally. It results in several psychological changes which adversely affect different dimensions of life and may lead to suicide. METHODS: Whole exome sequencing of 15 MDD patients, enrolled at the Dr. A. Q. Khan Institute of Behavioral Sciences, Karachi, was performed using NextSeq500. Different bioinformatics tools and databases like ANNOVAR, ALoFT, and GWAS were used to identify both common and rare variants associated with the pathogenesis of MDD. RESULTS: A total of 1985 variations were identified in 479 MDD-related genes. Several SNPs including rs1079610, rs11750538, rs1799913, rs1801131, rs2230267, rs2231187, rs3819976, rs4314963, rs56265970, rs587780434, rs6330, rs75111588, rs7596487, and rs9624909 were prioritized due to their deleteriousness and frequency difference between the patients and the South Asian population. A non-synonymous variation rs56265970 (BCR) had 26% frequency in patients and was not found in the South Asian population; a multiallelic UTR-5' insertion rs587780434 (RELN) was present with an allelic frequency of 70% in patients whereas 22% in the SAS population. Genetic alterations in PABPC1 genes, a stress-associated gene also had higher allele frequency in the cases than in the normal population. CONCLUSION: This present study identifies both common and rare variants in the genes associated with the pathogenesis of MDD in Pakistani patients. Genetic variations in BCR, RELN, and stress-associated PABPC1 suggest potential roles in the pathogenesis of MDD.

Vitexin isolated from Prosopis cineraria leaves induce apoptosis in K-562 leukemia cells via inhibition of the BCR-ABL-Ras-Raf pathway.

OBJECTIVES: Leukemia is one of the severe cancer types all around the globe. Even though some chemotherapeutic drugs are available for treating leukemia, they have various side effects. As an alternative approach, herbal drugs are focused on current research to overcome leukemia. The present work was conducted to investigate the antileukemic mechanism of active phytochemical vitexin, which was isolated from ethno-medicine (Prosopis cineraria leaf) used by traditional healers of West Bengal, India. METHODS: Antiproliferative mechanisms of selected phyto-compound against K-562 cells were evaluated using cellular uptake, morphological changes, DNA fragmentation, mitochondrial membrane potential and signaling pathways analysis. KEY FINDINGS: Vitexin exhibited cytotoxicity by reducing mitochondrial membrane potential (32.40%) and causing DNA fragmentation (84.15%). The western blotting study indicated inhibition of cell survival proteins (BCR, ABL, H-RAS, N-RAS, K-RAS and RAF) and expression of apoptotic proteins (p38, BAX and caspase-9) in leukemia cells upon treatment with vitexin. CONCLUSIONS: Based on the results, presently investigated phyto-compound vitexin could be considered for developing safe and natural drugs to treat leukemia after conducting suitable preclinical and clinical trials.

DDR1 contributes to kidney inflammation and fibrosis by promoting the phosphorylation of BCR and STAT3.

Discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase activated by collagen, contributes to chronic kidney disease. However, its role in acute kidney injury and subsequent development of kidney fibrosis is not clear. Thus, we performed a model of severe ischemia/reperfusion-induced acute kidney injury that progressed to kidney fibrosis in WT and Ddr1-null mice. We showed that Ddr1-null mice had reduced acute tubular injury, inflammation, and tubulointerstitial fibrosis with overall decreased renal monocyte chemoattractant protein (MCP-1) levels and STAT3 activation. We identified breakpoint cluster region (BCR) protein as a phosphorylated target of DDR1 that controls MCP-1 production in renal proximal tubule epithelial cells. DDR1-induced BCR phosphorylation or BCR downregulation increased MCP-1 secretion, suggesting that BCR negatively regulates the levels of MCP-1. Mechanistically, phosphorylation or downregulation of BCR increased ß-catenin activity and in turn MCP-1 production. Finally, we showed that DDR1-mediated STAT3 activation was required to stimulate the secretion of TGF-ß. Thus, DDR1 contributes to acute and chronic kidney injury by regulating BCR and STAT3 phosphorylation and in turn the production of MCP-1 and TGF-ß. These findings identify DDR1 an attractive therapeutic target for ameliorating both proinflammatory and profibrotic signaling in kidney disease.

A rare case of atypical chronic myeloid leukemia associated with t(8;22)(p11.2;q11.2)/ BCR-FGFR1 rearrangement: A case report and literature review.

Myeloid/lymphoid neoplasm with t(8;22)(p11.2;q11.2)/BCR-FGFR1 is an extremely rare diagnosis, with few reported cases to date. In contrast to other FGFR1-partner rearrangements that are associated with chronic eosinophilic leukemia, acute myeloid leukemia, and/or lymphoblastic lymphoma, patients with BCR-FGFR1 have a myeloproliferative disorder that closely resembles chronic myeloid leukemia (CML). The current report describes a rare case of a 61 year old man with an atypical CML phenotype associated with t(8;22)(p11.2;q11.2)/BCR-FGFR1. A literature review is presented to enhance the awareness of this rare diagnostic entity.

A case of a patient characterized by t(8;22)(p11;q11) and BCR/FGFR1 fusion gene, who was successfully treated with haploidentical hematopoietic stem cell transplantation.

Objective: The 8p11 myeloproliferative syndrome [EMS] is a rare myeloproliferative disorder which usually develops rapidly with chromosomal translocation of the fibroblast growth factor receptor 1 gene. The gene has 15 fusion partners, including the breakpoint cluster region (BCR) gene on chromosome 22. Of all the tests available, chromosome karyotype determination is the most important for the diagnosis of EMS. Here, we describe one case of a patient characterized by marked increase of white blood cells and thrombocytopenia and diagnosed as EMS with t(8;22)(p11;q11) by chromosome karyotype.Methods: 28-year-old man was referred to our hospital. He had a onemonth history of intermittent coughing and a small amount of expectoration after catching a cold. As an outpatient, his complete blood count showed: WBC was 130.04 × 109/L with 80.20% granulocytes.Hematologic investigations, bone marrow analysis and genomic DNA sequencing studies were performed.Results: Despite additional chromosomal abnormalities,the patient progressed rapidly with a B blast cell clone in one month. After diagnosis inthree months, the patient underwent the haplo-identical BMT of his brother, followed up for three years, and had a high rate of survival.Conclusions: Our report provides a definite conceptual framework for a better understanding of the characteristics of The 8p11 myeloproliferative syndrome [EMS].

Comparison of Hepatotoxicity Associated With New BCR-ABL Tyrosine Kinase Inhibitors vs Imatinib Among Patients With Chronic Myeloid Leukemia: A Systematic Review and Meta-analysis.

Importance: Although BCR-ABL fusion oncoprotein tyrosine kinase inhibitors (BCR-ABL TKIs) can substantially improve the survival rate of chronic myeloid leukemia (CML), they are clinically accompanied by severe hepatotoxicity. Objective: To compare the relative risk (RR) of hepatotoxicity of new-generation BCR-ABL TKIs with that of imatinib, and to provide an overall assessment of the clinical benefit. Data Sources: PubMed, Embase, Cochrane library databases, and ClinicalTrials.gov were searched for clinical trials published between January 2000 and April 2020. Study Selection: Study selection was conducted independently by 2 investigators according to the inclusion and exclusion criteria published previously in the protocol: only randomized phase 2 or phase 3 clinical trials that compared bosutinib, dasatinib, nilotinib, or ponatinib with imatinib were included. Among the 2666 records identified, 9 studies finally fulfilled the established criteria. Data Extraction and Synthesis: Two investigators extracted study characteristics and data independently using a standardized data extraction form. Data were extracted according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines. When substantial heterogeneity was observed, pooled estimates were calculated based on the random-effect model; otherwise, the fixed-effect model was used. Main Outcomes and Measures: Data extracted included study characteristics, baseline patient information, interventions and data on all-grade and high-grade (grades 3 and 4) elevation of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, overall survival, and major molecular response (MMR). The RRs and 95% CIs were calculated using the inverse variance method. Results: Nine trials involving 3475 patients were analyzed; the median (range) age was 49 (18-91) years; 2059 (59.2%) were male patients. Increased risks were observed for each new-generation TKI except for dasatinib. Patients receiving new-generation TKIs were more likely to experience all grades of ALT elevation (pooled RR, 2.89; 95% CI, 1.78-4.69; P < .001) and grades 3 and 4 ALT elevation (pooled RR, 4.36; 95% CI, 2.00-9.50; P < .001) compared with those receiving imatinib. Patients receiving new-generation TKIs were also more likely to experience all grades of AST elevation (pooled RR, 2.20; 95% CI, 1.63-2.98; P < .001) and grades 3 and 4 AST elevation (pooled RR, 2.65; 95% CI, 1.59-4.42; P < .001) compared with those receiving imatinib. New-generation TKIs were associated with a significantly higher rate of MMR at 1 year compared with imatinib (pooled RR, 1.59; 95% CI, 1.44-1.75; P < .001). No statistical difference in overall survival at 1 year was found between new-generation TKIs and imatinib (pooled RR, 1.00; 95% CI, 1.00-1.01; P = .33). Conclusions and Relevance: When compared to imatinib, bosutinib, nilotinib, and ponatinib had higher relative risks of hepatotoxicity. Treatment with new-generation TKIs was associated with a higher MMR rate at 1 year but not with 1-year overall survival.

Genomics of Resistance to Targeted Therapies.

Targeting BCR and BCL-2 signaling is a widely used therapeutic strategy for chronic lymphocytic leukemia. C481S mutation decreases the covalent binding affinity of ibrutinib to BTK, resulting in reversible rather than irreversible inhibition. In addition to BTK, mutations in PLCG2 have been demonstrated to mediate acquired ibrutinib resistance. Venetoclax, a highly selective BCL2 inhibitor, has high affinity to the BH3-binding grove of BCL2. Mutation in BCL2 (Gly101Val) decreases the affinity of BCL2 for venetoclax and confers acquired resistance in cell lines and primary patient cells. This review discusses the common mechanisms of resistance to targeted therapies in chronic lymphocytic leukemia.

Loss function of Bcr mutation causes gastrointestinal dysmotility and brain developmental defects.

BACKGROUND: The breakpoint cluster region (BCR) is a protein that originally forms a fusion protein with c-Abl tyrosine kinase and induces leukemia. Researchers have shown that BCR is enriched in the central nervous system and may contribute to neurological disorders. We aimed to investigate the physiological function of BCR in neural development in the gastrointestinal (GI) tract and brain. METHODS: Whole-exome sequencing was used to screen for mutations in the BCR. Bcr knockout mice (Bcr-/- , ΔExon 2-22) were generated using the CRISPR/Cas9 system. Transit of carmine red dye and glass bead expulsion assays were used to record total and proximal GI transit and distal colonic transit. KEY RESULTS: In an infant with pediatric intestinal pseudo-obstruction, we found a heterozygous de novo mutation (NM_004327.3:c.3072+1G>A) in BCR. Bcr deficiency mice (Bcr-/- ) exhibited growth retardation and impaired gastrointestinal motility. Bcr-/- mice had a prolonged average total GI transit time with increased distal colonic transit and proximal GI transit in isolation. Morphology analysis indicated that Bcr-/- mice had a less number of neurons in the submucosal plexus and myenteric plexus. Bcr-/- mice exhibited apparent structural defects in the brain, particularly in the cortex. Additionally, Bcr- depletion in the mouse cortex altered the expression of Ras homologous (Rho) family small GTPases. CONCLUSIONS AND INFERENCES: BCR mutations are associated with intestinal obstruction in children. Loss of Bcr can cause intestinal dysmotility and brain developmental defects may via regulation of Rho GTPases.

Molecular classification improves risk assessment in adult BCR-ABL1-negative B-ALL.

Genomic classification has improved risk assignment of pediatric, but not adult B-lineage acute lymphoblastic leukemia (B-ALL). The international UKALLXII/ECOG-ACRIN E2993 (#NCT00002514) trial accrued 1229 adolescent/adult patients with BCR-ABL1- B-ALL (aged 14 to 65 years). Although 93% of patients achieved remission, 41% relapsed at a median of 13 months (range, 28 days to 12 years). Five-year overall survival (OS) was 42% (95% confidence interval, 39, 44). Transcriptome sequencing, gene expression profiling, cytogenetics, and fusion polymerase chain reaction enabled genomic subtyping of 282 patient samples, of which 264 were eligible for trial, accounting for 64.5% of E2993 patients. Among patients with outcome data, 29.5% with favorable outcomes (5-year OS 65% to 80%) were deemed standard risk (DUX4-rearranged [9.2%], ETV6-RUNX1/-like [2.3%], TCF3-PBX1 [6.9%], PAX5 P80R [4.1%], high-hyperdiploid [6.9%]); 50.2% had high-risk genotypes with 5-year OS of 0% to 27% (Ph-like [21.2%], KMT2A-AFF1 [12%], low-hypodiploid/near-haploid [14.3%], BCL2/MYC-rearranged [2.8%]); 20.3% had intermediate-risk genotypes with 5-year OS of 33% to 45% (PAX5alt [12.4%], ZNF384/-like [5.1%], MEF2D-rearranged [2.8%]). IKZF1 alterations occurred in 86% of Ph-like, and TP53 mutations in patients who were low-hypodiploid (54%) and BCL2/MYC-rearranged (33%) but were not independently associated with outcome. Of patients considered high risk based on presenting age and white blood cell count, 40% harbored subtype-defining genetic alterations associated with standard- or intermediate-risk outcomes. We identified distinct immunophenotypic features for DUX4-rearranged, PAX5 P80R, ZNF384-R/-like, and Ph-like genotypes. These data in a large adult B-ALL cohort treated with a non-risk-adapted approach on a single trial show the prognostic importance of genomic analyses, which may translate into future therapeutic benefits.

CCL2 regulation of MST1-mTOR-STAT1 signaling axis controls BCR signaling and B-cell differentiation.

Chemokines are important regulators of the immune system, inducing specific cellular responses by binding to receptors on immune cells. In SLE patients, decreased expression of CCL2 on mesenchymal stem cells (MSC) prevents inhibition of B-cell proliferation, causing the characteristic autoimmune phenotype. Nevertheless, the intrinsic role of CCL2 on B-cell autoimmunity is unknown. In this study using Ccl2 KO mice, we found that CCL2 deficiency enhanced BCR signaling by upregulating the phosphorylation of the MST1-mTORC1-STAT1 axis, which led to reduced marginal zone (MZ) B cells and increased germinal center (GC) B cells. The abnormal differentiation of MZ and GC B cells were rescued by in vivo inhibition of mTORC1. Additionally, the inhibition of MST1-mTORC1-STAT1 with specific inhibitors in vitro also rescued the BCR signaling upon antigenic stimulation. The deficiency of CCL2 also enhanced the early activation of B cells including B-cell spreading, clustering and signalosome recruitment by upregulating the DOCK8-WASP-actin axis. Our study has revealed the intrinsic role and underlying molecular mechanism of CCL2 in BCR signaling, B-cell differentiation, and humoral response.

Nuclear localization of BCR and cortactin indicates their potential role in regulation of actin branching in nucleus.

AIM: To study cellular localization of full-length breakpoint cluster region (BCR), Pleckstrin homology domain of BCR and cortactin and determine whether they can coexist in cell nucleus. MATERIALS AND METHODS: HEK293T cell line was transfected with pECFP-BCR, pEGFP-PH and pmTagRFP-N1-CTTN using polyethyleneimine. Live cells were imaged in cell culture dishes with glass coverslip attached to the bottom with Leica SP8 STED 3D confocal microscope in the environmental chamber. Obtained images were processed and analyzed with Fiji software. RESULTS: We identified colocalization of full-length BCR and cortactin in nucleus of cell undergoing terminal phase of cell division. We did not observe nuclear localization of cortactin in non-dividing cell. Both Pleckstrin homology domain and full-length BCR exhibited cytoplasmic as well as nuclear localization. CONCLUSIONS: Colocalization of BCR with cortactin in cell nucleus indicates their potential role in regulation of actin network allowing for the maintenance of nuclear architecture and DNA integrity.

BAFF promotes heightened BCR responsiveness and manifestations of chronic GVHD after allogeneic stem cell transplantation.

Patients with chronic graft-versus-host disease (cGVHD) have increased B cell-activating factor (BAFF) levels, but whether BAFF promotes disease after allogeneic bone marrow transplantation (allo-BMT) remains unknown. In a major histocompatibility complex-mismatched model with cGVHD-like manifestations, we first examined B-lymphopenic µMT allo-BMT recipients and found that increased BAFF levels in cGVHD mice were not merely a reflection of B-cell number. Mice that later developed cGVHD had significantly increased numbers of recipient fibroblastic reticular cells with higher BAFF transcript levels. Increased BAFF production by donor cells also likely contributed to cGVHD, because BAFF transcript in CD4+ T cells from diseased mice and patients was increased. cGVHD manifestations in mice were associated with high BAFF/B-cell ratios and persistence of B-cell receptor (BCR)-activated B cells in peripheral blood and lesional tissue. By employing BAFF transgenic (Tg) mice donor cells, we addressed whether high BAFF contributed to BCR activation in cGVHD. BAFF increased NOTCH2 expression on B cells, augmenting BCR responsiveness to surrogate antigen and NOTCH ligand. BAFF Tg B cells had significantly increased protein levels of the proximal BCR signaling molecule SYK, and high SYK protein was maintained by BAFF after in vitro BCR activation or when alloantigen was present in vivo. Using T cell-depleted (BM only) BAFF Tg donors, we found that BAFF promoted cGVHD manifestations, circulating GL7+ B cells, and alloantibody production. We demonstrate that pathologic production of BAFF promotes an altered B-cell compartment and augments BCR responsiveness. Our findings compel studies of therapeutic targeting of BAFF and BCR pathways in patients with cGVHD.

miR-29 modulates CD40 signaling in chronic lymphocytic leukemia by targeting TRAF4: an axis affected by BCR inhibitors.

B-cell receptor (BCR) signaling and T-cell interactions play a pivotal role in chronic lymphocytic leukemia (CLL) pathogenesis and disease aggressiveness. CLL cells can use microRNAs (miRNAs) and their targets to modulate microenvironmental interactions in the lymph node niches. To identify miRNA expression changes in the CLL microenvironment, we performed complex profiling of short noncoding RNAs in this context by comparing CXCR4/CD5 intraclonal cell subpopulations (CXCR4dimCD5bright vs CXCR4brightCD5dim cells). This identified dozens of differentially expressed miRNAs, including several that have previously been shown to modulate BCR signaling (miR-155, miR-150, and miR-22) but also other candidates for a role in microenvironmental interactions. Notably, all 3 miR-29 family members (miR-29a, miR-29b, miR-29c) were consistently down-modulated in the immune niches, and lower miR-29(a/b/c) levels associated with an increased relative responsiveness of CLL cells to BCR ligation and significantly shorter overall survival of CLL patients. We identified tumor necrosis factor receptor-associated factor 4 (TRAF4) as a novel direct target of miR-29s and revealed that higher TRAF4 levels increase CLL responsiveness to CD40 activation and downstream nuclear factor-κB (NF-κB) signaling. In CLL, BCR represses miR-29 expression via MYC, allowing for concurrent TRAF4 upregulation and stronger CD40-NF-κB signaling. This regulatory loop is disrupted by BCR inhibitors (bruton tyrosine kinase [BTK] inhibitor ibrutinib or phosphatidylinositol 3-kinase [PI3K] inhibitor idelalisib). In summary, we showed for the first time that a miRNA-dependent mechanism acts to activate CD40 signaling/T-cell interactions in a CLL microenvironment and described a novel miR-29-TRAF4-CD40 signaling axis modulated by BCR activity.

Identification of "regulation of RhoA activity panel" as a prognostic and predictive biomarker for gastric cancer.

RhoA is a member of the RHO family GTPases and is associated with essential functions in gastric cancer. In this study, we identified a gastric cancer biomarker, termed the "regulation of RhoA activity panel" (RRAP). Patients with gastric cancer from The Cancer Genome Atlas database were divided into training (N=160) and validation (N=155) cohorts. A cohort of 109 Chinese gastric cancer patients was utilized as an independent validation. Patients with mutated RRAP showed significantly better overall survival than patients with wild type RRAP. We also analyzed the association between RRAP and the migration capacity, immune-related signatures, and the tumor microenvironment. RRAP-mutant tumors had a significantly lower degree of lymph node metastasis and lower activities of migration-related pathways. These tumors also showed significantly increased immune cell infiltration and cytotoxic activity. Furthermore, two independent patient cohorts who received immune checkpoint blockade therapy were assessed for RRAP mutant status. As expected, for both immunotherapy cohorts, higher response rates to immune checkpoint blockade therapy were observed in patients with RRAP-mutant tumors than in patients with wild type RRAP tumors. Overall, this study indicates that the RRAP gene set is a potential biomarker for gastric cancer prognosis and therapeutic selection.

Integrated genomic analysis using chromosomal microarray, fluorescence in situ hybridization and mate pair analyses: Characterization of a cryptic t(9;22)(p24.1;q11.2)/BCR-JAK2 in myeloid/lymphoid neoplasm with eosinophilia.

The 2016 World Health Organization entity 'Myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB or FGFR1, or with PCM1-JAK2' encompasses a group of rare neoplasms that result from the formation of a fusion gene that leads to expression of an aberrant tyrosine kinase. This entity also contains variant JAK2 fusion partners, and detection of this defining event can be facilitated by various cytogenetic and molecular methods. Cryptic rearrangements of 9p24/JAK2 can be particularly challenging to identify. We describe the use of chromosomal microarray analysis (CMA), fluorescence in situ hybridization (FISH) with a probe for JAK2, and genomic mate pair analysis to describe a complex karyotype with a t(9;22) that produced a functional BCR-JAK2 fusion, leading to the appropriate diagnosis for the patient. This case highlights the importance of using an integrated genomic approach to fully define complex aberrations to assign proper diagnoses.

Scaffold hopping of the SYK inhibitor entospletinib leads to broader targeting of the BCR signalosome.

Spleen tyrosine kinase (SYK) and Bruton's tyrosine kinase (BTK) are attractive targets in human haematological malignancies with excessively activated B-cell receptor (BCR) signalling pathways. Entospletinib is a SYK inhibitor that has been evaluated as a clinical candidate. We designed and prepared five isosteres in which the imidazo[1,2-a]pyrazine scaffold of entospletinib was altered to pyrazolo[3,4-d]pyrimidine, pyrrolo[3,2-d]pyrimidine, imidazo[4,5-b]pyridine, imidazo[4,5-c]pyridine and purine. The last two isosteres were the most potent SYK inhibitors, with IC50 values in the mid-nanomolar range. Importantly, three compounds also inhibited BTK more effectively than did entospletinib. Further experiments then showed that BCR signalling was suppressed in Ramos cells by the potent compounds. Preliminary kinase inhibition screening also revealed LCK and SRC as additional targets. Our results further support the hypothesis that multikinase targeting compounds could produce more robust responses in the treatment of B lymphoid neoplasms.