The t(8;17)(p11;q23) in the 8p11 myeloproliferative syndrome fuses MYO18A to FGFR1

Emerging concepts of myosin 18A isoform mechanobiology in organismal and immune system physiology, development, and function

Alternative and combinatorial splicing of myosin 18A (MYO18A) gene transcripts results in expression of MYO18A protein isoforms and isoform variants with different membrane and subcellular localizations, and functional properties. MYO18A proteins are members of the myosin superfamily consisting of a myosin-like motor domain, an IQ motif, and a coiled-coil domain. MYO18A isoforms, however, lack the ability to hydrolyze ATP and do not perform ATP-dependent motor activity. MYO18A isoforms are distinguished by different amino- and carboxy-terminal extensions and domains. The domain organization and functions of MYO18Aα, MYO18Aβ, and MYO18Aγ have been studied experimentally. MYO18Aα and MYO18Aβ have a common carboxy-terminal extension but differ by the presence or absence of an amino-terminal KE repeat and PDZ domain, respectively. The amino- and carboxy-terminal extensions of MYO18Aγ contain unique proline and serine-rich domains. Computationally predicted MYO18Aε and MYO18Aδ isoforms contain the carboxy-terminal serine-rich extension but differ by the presence or absence of the amino-terminal KE/PDZ extension. Additional isoform variants within each category arise by alternative utilization or inclusion/exclusion of small exons. MYO18Aα variants are expressed in somatic cells and mature immune cells, whereas MYO18Aβ variants occur mainly in myeloid and natural killer cells. MYO18Aγ expression is selective to cardiac and skeletal muscle. In the present review perspective, we discuss current and emerging concepts of the functional specialization of MYO18A proteins in membrane and cytoskeletal dynamics, cellular communication and signaling, endocytic and exocytic organelle movement, viral infection, and as the SP-R210 receptor for surfactant protein A.

The 8p11 myeloproliferative syndrome: Genotypic and phenotypic classification and targeted therapy

EMS(8p11 myeloproliferative syndrome, EMS) is an aggressive hematological neoplasm with/without eosinophilia caused by a rearrangement of the FGFR1 gene at 8p11-12. It was found that all cases carry chromosome abnormalities at the molecular level, not only the previously reported chromosome translocation and insertion but also a chromosome inversion. These abnormalities produced 17 FGFR1 fusion genes, of which the most common partner genes are ZNF198 on 13q11-12 and BCR of 22q11.2. The clinical manifestations can develop into AML (acute myeloid leukemia), T-LBL (T-cell lymphoblastic lymphoma), CML (chronic myeloid leukemia), CMML (chronic monomyelocytic leukemia), or mixed phenotype acute leukemia (MPAL). Most patients are resistant to traditional chemotherapy, and a minority of patients achieve long-term clinical remission after stem cell transplantation. Recently, the therapeutic effect of targeted tyrosine kinase inhibitors (such as pemigatinib and infigratinib) in 8p11 has been confirmed in vitro and clinical trials. The TKIs may become an 8p11 treatment option as an alternative to hematopoietic stem cell transplantation, which is worthy of further study.

Identification of a novel HOOK3-FGFR1 fusion gene involved in activation of the NF-kappaB pathway

Background

Rearrangements involving the fibroblast growth factor receptor 1 (FGFR1) gene result in 8p11 myeloproliferative syndrome (EMS), which is a rare and aggressive hematological malignancy that is often initially diagnosed as myelodysplastic syndrome (MDS). Clinical outcomes are typically poor due to relative resistance to tyrosine kinase inhibitors (TKIs) and rapid transformation to acute leukemia. Deciphering the transcriptomic signature of FGFR1 fusions may open new treatment strategies for FGFR1 rearrangement patients.

Methods

DNA sequencing (DNA-seq) was performed for 20 MDS patients and whole exome sequencing (WES) was performed for one HOOK3-FGFR1 fusion positive patient. RNA sequencing (RNA-seq) was performed for 20 MDS patients and 8 healthy donors. Fusion genes were detected using the STAR-Fusion tool. Fluorescence in situ hybridization (FISH), quantitative real-time PCR (qRT-PCR), and Sanger sequencing were used to confirm the HOOK3-FGFR1 fusion gene. The phosphorylation antibody array was performed to validate the activation of nuclear factor-kappaB (NF-kappaB) signaling.

Results

We identified frequently recurrent mutations of ASXL1 and U2AF1 in the MDS cohort, which is consistent with previous reports. We also identified a novel in-frame HOOK3-FGFR1 fusion gene in one MDS case with abnormal monoclonal B-cell lymphocytosis and ring chromosome 8. FISH analysis detected the FGFR1 break-apart signal in myeloid blasts only. qRT-PCR and Sanger sequencing confirmed the HOOK3-FGFR1 fusion transcript with breakpoints located at the 11th exon of HOOK3 and 10th exon of FGFR1, and Western blot detected the chimeric HOOK3-FGFR1 fusion protein that is presumed to retain the entire tyrosine kinase domain of FGFR1. The transcriptional feature of HOOK3-FGFR1 fusion was characterized by the significant enrichment of the NF-kappaB pathway by comparing the expression profiling of FGFR1 fusion positive MDS with 8 healthy donors and FGFR1 fusion negative MDS patients. Further validation by phosphorylation antibody array also showed NF-kappaB activation, as evidenced by increased phosphorylation of p65 (Ser 536) and of IKBalpha (Ser 32).

Conclusions

The HOOK3-FGFR1 fusion gene may contribute to the pathogenesis of MDS and activate the NF-kappaB pathway. These findings highlight a potential novel approach for combination therapy for FGFR1 rearrangement patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02451-y.

Multifaceted Function of Myosin-18, an Unconventional Class of the Myosin Superfamily

Myosin is a diverse superfamily of motor proteins responsible for actin-based motility and contractility in eukaryotic cells. Myosin-18 family, including myosin-18A and myosin-18B, belongs to an unconventional class of myosin, which lacks ATPase motor activity, and the investigations on their functions and molecular mechanisms in vertebrate development and diseases have just been initiated in recent years. Myosin-18A is ubiquitously expressed in mammalian cells, whereas myosin-18B shows strong enrichment in striated muscles. Myosin-18 family is important for cell motility, sarcomere formation, and mechanosensing, mostly by interacting with other cytoskeletal proteins and cellular apparatus. Myosin-18A participates in several intracellular transport processes, such as Golgi trafficking, and has multiple roles in focal adhesions, stress fibers, and lamellipodia formation. Myosin-18B, on the other hand, participates in actomyosin alignment and sarcomere assembly, thus relating to cell migration and muscle contractility. Mutations of either Myo18a or Myo18b cause cardiac developmental defects in mouse, emphasizing their crucial role in muscle development and cardiac diseases. In this review, we revisit the discovery history of myosin-18s and summarize the evolving understanding of the molecular functions of myosin-18A and myosin-18B, with an emphasis on their separate yet closely related functions in cell motility and contraction. Moreover, we discuss the diseases tightly associated with myosin-18s, especially cardiovascular defects and cancer, as well as highlight the unanswered questions and potential future research perspectives on myosin-18s.

Myeloid/Lymphoid Neoplasms Associated With Eosinophilia and Rearrangements of PDGFRA, PDGFRB, or FGFR1 or With PCM1-JAK2

OBJECTIVES

To summarize cases submitted to the 2019 Society for Hematopathology/European Association for Haematopathology Workshop under the category of myeloid/lymphoid neoplasms with eosinophilia and PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2 rearrangements, focusing on recent updates and relevant practice findings.

METHODS

The cases were summarized according to their respective gene rearrangement to illustrate the spectrum of clinical, laboratory, and histopathology manifestations and to explore the appropriate molecular genetic tests.

RESULTS

Disease presentations were heterogeneous, including myeloproliferative neoplasms (MPNs), myelodysplastic syndromes (MDSs), MDS/MPN, acute myeloid leukemia, acute B- or T-lymphoblastic lymphoma/acute lymphoblastic lymphoma (ALL/LBL), or mixed-lineage neoplasms. Frequent extramedullary involvement occurred. Eosinophilia was common but not invariably present. With the advancement of RNA sequencing, cryptic rearrangements were recognized in genes other than PDGFRA. Additional somatic mutations were more frequent in the FGFR1-rearranged cases. Cases with B-ALL presentations differed from Philadelphia-like B-ALL by the presence of an underlying MPN. Cases with FLT3 and ABL1 rearrangements could be potential candidates for future inclusion in this category.

CONCLUSIONS

Accurate diagnosis and classification of this category of myeloid/lymphoid neoplasms has important therapeutic implications. With the large number of submitted cases, we expand our understanding of these rare neoplasms and improve our ability to diagnose these genetically defined disorders.

Myosins and Disease

Myosins constitute a superfamily of actin-based molecular motor proteins that mediates a variety of cellular activities including muscle contraction, cell migration, intracellular transport, the formation of membrane projections, cell adhesion, and cell signaling. The 12 myosin classes that are expressed in humans share sequence similarities especially in the N-terminal motor domain; however, their enzymatic activities, regulation, ability to dimerize, binding partners, and cellular functions differ. It is becoming increasingly apparent that defects in myosins are associated with diseases including cardiomyopathies, colitis, glomerulosclerosis, neurological defects, cancer, blindness, and deafness. Here, we review the current state of knowledge regarding myosins and disease.

Myosin XVIII

Class XVIII myosins represent a branch of the myosin family tree characterized by the presence of large N- and C-terminal extensions flanking a generic myosin core. These myosins display the highest sequence similarity to conventional class II muscle myosins and are compatible with but not restricted to myosin-2 contractile structures. Instead, they fulfill their functions at diverse localities, such as lamella, actomyosin bundles, the Golgi apparatus, focal adhesions, the cell membrane, and within sarcomeres. Sequence comparison of active-site residues and biochemical data available thus far indicate that this myosin class lacks active ATPase-driven motor activity, suggesting that its members function as structural myosins. An emerging body of evidence indicates that this structural capability is essential for the organization, maturation, and regulation of the contractile machinery in both muscle and nonmuscle cells. This is supported by the clear association of myosin-18A (Myo18A) and myosin-18B (Myo18B) dysregulation with diseases such as cancer and various myopathies.

[Myeloid/lymphoid neoplasms with eosinophilia and FGFR1 rearrangement: 5 cases report and literatures review]

目的

分析罕见疾病伴嗜酸性粒细胞增多和FGFR1重排的髓系/淋系肿瘤（即8p11骨髓增殖综合征，EMS）的临床特征、诊断及治疗。

方法

总结中国医学科学院血液病医院2014年1月至2018年5月收治的5例确诊EMS患者的临床表现、实验室特征、诊治经过及转归。

结果

5例EMS患者外周血白细胞计数均明显升高，伴有嗜酸性粒细胞绝对值增高（均值18.89×10⁹/L）；骨髓髓系极度增生，原始细胞均<5%，嗜酸性粒细胞比例增高（均值17.24%）。5例患者染色体核型各不相同，但FISH检查均存在FGFR1基因重排。发病至确诊平均时间为4.8个月，中位生存期仅14个月。

结论

EMS是一种罕见病，恶性程度高，对常规化疗反应差，生存期短，且易发生误诊漏诊，细胞遗传学及分子生物学检查有助于早期诊断。

Two myeloid leukemia cases with rare FLT3 fusions

Genetic rearrangements involving FLT3 are rare and only recently have been detected in myeloid/lymphoid neoplasms associated with eosinophilia (MLN-eos) and chronic myeloproliferative disorders. Here we report two cases with FLT3 fusions in patients demonstrating mixed features of myelodysplastic/myeloproliferative neoplasms. In the first case, FLT3 was fused with a new fusion partner MYO18A in a patient with marrow features most consistent with atypical chronic myeloid leukemia; the second case involving ETV6-FLT3 fusion was observed in a case with bone marrow features most consistent with chronic myelomonocytic leukemia. Notably, we observed that samples from both patients demonstrated FLT3 inhibitor (quizartinib and sorafenib) sensitivity in ex vivo drug screening assay.

GOLPH3: a Golgi phosphatidylinositol(4)phosphate effector that directs vesicle trafficking and drives cancer

GOLPH3 is a peripheral membrane protein localized to the Golgi and its vesicles, but its purpose had been unclear. We found that GOLPH3 binds specifically to the phosphoinositide phosphatidylinositol(4)phosphate [PtdIns(4)P], which functions at the Golgi to promote vesicle exit for trafficking to the plasma membrane. PtdIns(4)P is enriched at the trans-Golgi and so recruits GOLPH3. Here, a GOLPH3 complex is formed when it binds to myosin18A (MYO18A), which binds F-actin. This complex generates a pulling force to extract vesicles from the Golgi; interference with this GOLPH3 complex results in dramatically reduced vesicle trafficking. The GOLPH3 complex has been identified as a driver of cancer in humans, likely through multiple mechanisms that activate secretory trafficking. In this review, we summarize the literature that identifies the nature of the GOLPH3 complex and its role in cancer. We also consider the GOLPH3 complex as a hub with the potential to reveal regulation of the Golgi and suggest the possibility of GOLPH3 complex inhibition as a therapeutic approach in cancer.

MYO18A: An unusual myosin

MYO18A is a divergent member of the myosin family characterized by the presence of an amino-terminal PDZ domain. MYO18A has been found in a few different complexes involved in intracellular transport processes. MYO18A is found in a complex with LURAP1 and MRCK that functions in retrograde treadmilling of actin. It also has been found in a complex with PAK2, βPIX, and GIT1, functioning to transport that protein complex from focal adhesions to the leading edge. Finally, a high proportion of MYO18A is found in complex with GOLPH3 at the trans Golgi, where it functions to promote vesicle budding for Golgi-to-plasma membrane trafficking. Interestingly, MYO18A has been implicated as a cancer driver, as have other components of the GOLPH3 pathway. It remains uncertain as to whether or not MYO18A has intrinsic motor activity. While many questions remain, MYO18A is a fascinatingly unique myosin that is essential in higher organisms.

Pediatric 8p11 eosinophilic myeloproliferative syndrome (EMS): A case report and review of the literature

The 8p11 eosinophilic myeloproliferative syndrome (EMS) is an aggressive neoplasm driven by translocation of the fibroblast growth factor receptor 1 and often transforms to leukemias and lymphomas that are refractory to treatment. The first case was identified in 1983, and to date over 70 cases have been reported in the literature. Despite those reports, no consensus exists on management of this condition, and inconsistency in treatment regimens is even more pronounced in the pediatric literature. We report a case of a male infant with the 8p11 EMS, review the published pediatric experience with EMS, and discuss treatment strategies for this enigmatic hematological disorder.

Multiple MYO18A-PDGFRB fusion transcripts in a myeloproliferative neoplasm patient with t(5;17)(q32;q11)

BACKGROUND

Myeloproliferative neoplasms (MPNs), typically defined by myeloid proliferation and eosinophilia, and are only rarely caused by platelet-derived growth factor receptor beta (PDGFRB) gene rearrangements.

CASE PRESENTATION

Here, we report a unique case of MPN that is negative for eosinophilia and characterized by a novel PDGFRB rearrangement. After cytogenetic analysis revealed a karyotype of t(5;17) (q32;q11), we used fluorescence in situ hybridization to specifically identify the PDGFRB gene at 5q31-q33 as the gene that had been translocated. Subsequently, RNA sequencing identified a new MYO18A-PDGFRB gene fusion. This fusion presented a previously undescribed breakpoint composed of exon 37 of MYO18A and exon 13 of PDGFRB. Furthermore, both RT-PCR and Bi-directional Sanger sequencing confirmed this out-of-frame fusion. Interestingly, we simultaneously identified the presence of another three PDGFRB transcripts, all of which were in-frame fusions. After treating the patient with imatinib, the t(5;17) translocation was no longer detected by conventional cytogenetics or by FISH, and at the time of the last follow-up, the patient had been in complete remission for 26 months.

CONCLUSION

We prove that MYO18A-PDGFRB fusions are recurrent genetic aberrations involved in MPNs, and identify multiple fusion transcripts with novel breakpoints.

Myosins: Domain Organisation, Motor Properties, Physiological Roles and Cellular Functions

Myosins are cytoskeletal motor proteins that use energy derived from ATP hydrolysis to generate force and movement along actin filaments. Humans express 38 myosin genes belonging to 12 classes that participate in a diverse range of crucial activities, including muscle contraction, intracellular trafficking, cell division, motility, actin cytoskeletal organisation and cell signalling. Myosin malfunction has been implicated a variety of disorders including deafness, hypertrophic cardiomyopathy, Usher syndrome, Griscelli syndrome and cancer. In this chapter, we will first discuss the key structural and kinetic features that are conserved across the myosin family. Thereafter, we summarise for each member in turn its unique functional and structural adaptations, cellular roles and associated pathologies. Finally, we address the broad therapeutic potential for pharmacological interventions that target myosin family members.

Mutations in tyrosine kinase and tyrosine phosphatase and their relevance to the target therapy in hematologic malignancies

Protein tyrosine kinases and protein tyrosine phosphatases play pivotal roles in regulation of cellular phosphorylation and signal transduction with opposite functions. Accumulating evidences have uncovered the relevance of genetic alterations in these two family members to hematologic malignancies. This review underlines progress in understanding the pathogenesis of these genetic alterations including mutations and aberrant expression and the evolving protein tyrosine kinases and protein tyrosine phosphatases targeted therapeutic strategies in hematologic neoplasms.

KIT D816V and JAK2 V617F mutations are seen recurrently in hypereosinophilia of unknown significance

Myeloproliferative neoplasms with eosinophilia are commonly characterized by a normal karyotype and remain poorly defined at the molecular level. We therefore investigated 426 samples from patients with hypereosinophilia of unknown significance initially referred for screening of the FIP1L1-PDGFRA (FP) fusion gene also for KIT D816V and JAK2 V617F mutations. Overall, 86 (20%) patients tested positive: FP+ in 55 (12%), KIT D816V+ in 14 (3%), and JAK2 V617F+ in 17 (4%) patients, respectively. To gain better insight into clinical characteristics, we compared these cases with 31 additional and well-characterized KIT D816V+ eosinophilia-associated systemic mastocytosis (SM-eo) patients enrolled within the "German Registry on Disorders of Eosinophils and Mast cells." Significant differences included younger age, male predominance, and higher eosinophil counts for FP+ cases while abdominal lymphadenopathy, ascites, and serum tryptase levels >100 μg/l were characteristic for those with KIT D816V. Leukocytes, hemoglobin, and splenomegaly did not differ significantly. A median of three additional mutations, most frequently TET2 and SRSF2, were identified in 12/13 KIT D816V+ SM-eo patients with available material indicating a more complex molecular pathogenesis. Median survival was not reached for FP+ cases but was only 26 and 41 months for KIT D816V+ SM and JAK2 V617F+ MPN-eo, respectively. Eosinophilia of ≥2 × 10(9) /l was identified as discriminator for inferior survival in KIT D816V+ and/or JAK2 V617F+ patients (median survival 20 months vs. not reached, P = 0.002). Thus, there is a clear prognostic and therapeutic rationale for detection of KIT D816V and JAK2 V617F in the diagnostic work up of eosinophilia.

Myeloid and lymphoid neoplasm with abnormalities of FGFR1 presenting with trilineage blasts and RUNX1 rearrangement: a case report and review of literature

OBJECTIVES

Myeloid and lymphoid neoplasms with abnormalities of fibroblast growth factor receptor 1 gene (FGFR1) are a rare and aggressive disease group that harbors translocations of FGFR1 with at least 14 recognized partner genes. We report a case of a patient with a novel t(17;21)(p13;q22) with RUNX1 rearrangement and trilineage blasts.

METHODS

A 29-year-old man with relapsed T-lymphoblastic lymphoma in the cervical nodes showed a myeloproliferative neoplasm in his bone marrow with three separate populations of immunophenotypically aberrant myeloid, T-lymphoid, and B-lymphoid blasts by flow cytometry. Cytogenetic and fluorescent in situ hybridization studies showed unique dual translocations of t(8;13)(p11.2;q12) and t(17;21)(p13;q22) with RUNX1 rearrangement.

RESULTS

The patient was initiated on a mitoxantrone, etoposide, and cytarabine chemotherapy regimen and died of complications of disease 1 month later.

CONCLUSIONS

To our knowledge, this is the first reported case of a myeloid and lymphoid neoplasm with abnormalities of FGFR1 with t(17;21)(p13;q22) and trilineage blasts.

8p11 myeloproliferative syndrome with t(1;8)(q25;p11.2): a case report and review of the literature

8p11 myeloproliferative syndrome (EMS) is a rare disease characterized by myeloproliferative neoplasm (MPN) associated with eosinophilia and T or B lymphoblastic lymphoma/leukemia. EMS is defined by molecular disruption of the FGFR1 gene at the 8p11-12 chromosome locus, and various partner genes are associated with FGFR1 gene translocation or insertion. The different partner-FGFR1 fusion genes are associated with slightly different disease phenotypes. The present patient showed T lymphoblastic lymphoma in a cervical lymph node, involvement of malignant lymphoma in the skin, and MPN bone marrow morphology with peripheral monocytosis. Chromosome analysis of the patient showed t(1;8)(q25;p11.2). To our knowledge, only 2 cases of EMS with translocation of t(1;8)(q25;p11.2) have been previously reported. Including this case, all 3 cases with EMS with t(1;8)(q25;p11.2) showed MPN bone marrow morphology and peripheral monocytosis. These findings support that t(1;8)(q25;p11.2) is associated with peripheral monocytosis in EMS patients. Of the 2 cases of EMS with t(1;8)(q25;p11.2) which were previously reported, FGFR1 rearrangement was not confirmed in 1 case. Similarly, FGFR1 rearrangement in the present case was not detected by fluorescence in situ hybridization or reverse transcription-polymerase chain reaction. Further study is needed to identify other techniques that could be used to demonstrate FGFR1 rearrangement.

Non-muscle myosins in tumor progression, cancer cell invasion, and metastasis

The actin cytoskeleton, which regulates cell polarity, adhesion, and migration, can influence cancer progression, including initial acquisition of malignant properties by normal cells, invasion of adjacent tissues, and metastasis to distant sites. Actin-dependent molecular motors, myosins, play key roles in regulating tumor progression and metastasis. In this review, we examine how non-muscle myosins regulate neoplastic transformation and cancer cell migration and invasion. Members of the myosin superfamily can act as either enhancers or suppressors of tumor progression. This review summarizes the current state of knowledge on how mutations or epigenetic changes in myosin genes and changes in myosin expression may affect tumor progression and patient outcomes and discusses the proposed mechanisms linking myosin inactivation or upregulation to malignant phenotype, cancer cell migration, and metastasis.

Functional roles of fibroblast growth factor receptors (FGFRs) signaling in human cancers

The fibroblast growth factor receptors (FGFRs) regulate important biological processes including cell proliferation and differentiation during development and tissue repair. Over the past decades, numerous pathological conditions and developmental syndromes have emerged as a consequence of deregulation in the FGFRs signaling network. This review aims to provide an overview of FGFR family, their complex signaling pathways in tumorigenesis, and the current development and application of therapeutics targeting the FGFRs signaling for treatment of refractory human cancers.

The 8p12 myeloproliferative syndrome

The occurrence of a myeloproliferative disorder in association with an aggressive lymphoproliferative disorder is a distinctly unusual phenomenon. We report a case of concurrent leukaemia-lymphoma syndrome characterized by a BCR/ABL-negative myeloproliferative disease, eosinophilia and a lymphoma. The bone marrow chromosome analysis showed the karyotype 46, XY, t(8;9) (q12; p33), which indicated presence of FGFR1 gene translocations. 8p12 myeloproliferative syndrome (EMS) / stem cell leukaemia-lymphoma syndrome (SCLL) belongs to the tyrosine kinase fusion genes chronic myeloproliferative diseases. The patient was managed conservatively with hydroxyurea, allopurinol and blood component therapy. The patient eventually died of intracerebral haemorrhage due to severe thrombocytopaenia.

Based on our experience the overlap in the clinical presentation of this disease with lymphomas, can lead to a delay in diagnosis of EMS/SCLL. Given the aggressive nature of this disease, an accurate clinical and molecular diagnosis of this entity has become increasingly important.

The 8p12 myeloproliferative syndrome

The occurrence of a myeloproliferative disorder in association with an aggressive lymphoproliferative disorder is a distinctly unusual phenomenon. We report a case of concurrent leukaemia-lymphoma syndrome characterized by a BCR/ABL-negative myeloproliferative disease, eosinophilia and a lymphoma. The bone marrow chromosome analysis showed the karyotype 46, XY, t(8;9) (q12; p33), which indicated presence of FGFR1 gene translocations. 8p12 myeloproliferative syndrome (EMS) / stem cell leukaemia-lymphoma syndrome (SCLL) belongs to the tyrosine kinase fusion genes chronic myeloproliferative diseases. The patient was managed conservatively with hydroxyurea, allopurinol and blood component therapy. The patient eventually died of intracerebral haemorrhage due to severe thrombocytopaenia. Based on our experience the overlap in the clinical presentation of this disease with lymphomas, can lead to a delay in diagnosis of EMS/SCLL. Given the aggressive nature of this disease, an accurate clinical and molecular diagnosis of this entity has become increasingly important.

Functional characterization of human myosin-18A and its interaction with F-actin and GOLPH3

Molecular motors of the myosin superfamily share a generic motor domain region. They commonly bind actin in an ATP-sensitive manner, exhibit actin-activated ATPase activity, and generate force and movement in this interaction. Class-18 myosins form heavy chain dimers and contain protein interaction domains located at their unique N-terminal extension. Here, we characterized human myosin-18A molecular function in the interaction with nucleotides, F-actin, and its putative binding partner, the Golgi-associated phosphoprotein GOLPH3. We show that myosin-18A comprises two actin binding sites. One is located in the KE-rich region at the start of the N-terminal extension and appears to mediate ATP-independent binding to F-actin. The second actin-binding site resides in the generic motor domain and is regulated by nucleotide binding in the absence of intrinsic ATP hydrolysis competence. This core motor domain displays its highest actin affinity in the ADP state. Electron micrographs of myosin-18A motor domain-decorated F-actin filaments show a periodic binding pattern independent of the nucleotide state. We show that the PDZ module mediates direct binding of myosin-18A to GOLPH3, and this interaction in turn modulates the actin binding properties of the N-terminal extension. Thus, myosin-18A can act as an actin cross-linker with multiple regulatory modulators that targets interacting proteins or complexes to the actin-based cytoskeleton.

B-lymphoblastic leukemia/lymphoma associated with t(8;13)(p11;q12)/ ZMYM2 (ZNF198)-FGFR1 : rare case and review of the literature

Myeloid and lymphoid neoplasms with fibroblastic growth factor receptor-1 (FGFR1) abnormalities originate from mutated pluripotent stem cells and have a heterogeneous clinical presentation. There are 12 identified partner genes commonly involved in FGFR1 translocation at an 8p11 breakpoint. In FGFR1-related neoplasms, T-lymphoblastic lymphoma with eosinophilia is the most common clinical scenario, whereas acute B-lymphoblastic leukemia/lymphoma (B-ALL/LBL) is rare. To date, only 7 cases of B-ALL/LBL with FGFR1 abnormalities have been reported. Here, we report an additional case of a 64-year-old gentleman with leukocytosis, eosinophilia and diffuse mediastinal and general lymphadenopathy. Bone marrow examination showed patchy infiltrates of immature precursors/blasts, along with myeloid/eosinophilic hyperplasia. Immunophenotyping confirmed increased B lymphoblasts (30-40%). Karyotyping revealed cytogenetic abnormalities, including t(8;13)(p11;q12)/ZMYM2 (ZNF198)-FGFR1 and trisomy 21. The patient did not respond to hyper-CVAD chemotherapy and within 4 months developed acute myelomonocytic leukemia and expired 11 months after the initial diagnosis. Similar cases from the literature are reviewed.

A case of 8p11 myeloproliferative syndrome with BCR-FGFR1 gene fusion presenting with trilineage acute leukemia/lymphoma, successfully treated by cord blood transplantation

The 8p11 myeloproliferative syndrome is a rare neoplasm associated with chromosomal translocations involving the fibroblast growth factor receptor 1 (FGFR1) gene located at chromosome 8p11-12. FGFR1 encodes a transmembrane receptor tyrosine kinase. The resultant fusion proteins are constitutively active tyrosine kinases that drive the proliferation of hematopoietic cells, whose uncontrolled growth can present as a myeloproliferative neoplasm. We report here the case of a 50-year-old man harboring the t(8;22)(p12;q11) chromosomal translocation in cells from both bone marrow and lymph nodes. He presented with acute leukemia and lymphoma with trilineage features. A novel mRNA in-frame fusion between exon 4 of the breakpoint cluster region (BCR) gene at chromosome 22q11 and exon 9 of FGFR1 gene on chromosome 8p11-12 was identified by reverse transcription polymerase chain reaction analysis and was confirmed by DNA sequencing. Because the patient was refractory to chemotherapy, cord blood transplantation was performed in progressive disease. It resulted in a successful outcome in which cytogenetic complete remission has been maintained for 2 years till date.

A three-way translocation of MLL, MLLT11, and the novel reciprocal partner gene MYO18A in a child with acute myeloid leukemia

Translocations of the MLL gene are common among neonates and infants with acute lymphoblastic and acute myeloid leukemias. We characterized a new three-way translocation involving MLL in an infant with acute myeloid leukemia who subsequently relapsed and underwent a hematopoietic stem cell transplant from an unrelated stem cell donor. The translocation was characterized using karyotyping and fluorescence in situ hybridization. In this patient, a complex rearrangement fused the distal part of 11q23 with 17q11.2, the distal part of 17q11.2 with 1q21, and the distal part of 1q21 with 11q23, resulting in a three-way translocation; t(1;11;17)(q21;q23;q11.2). The two reciprocal MLL fusion sites were cloned by long-distance inverse polymerase chain reaction, which led to the identification of MLL-MLLT11 and the reciprocal MYO18A-MLL fusion alleles. Both fusion genes are in-frame and can be translated into functional fusion proteins. Although the MLL-MLLT11 fusion gene has been described in the literature, the reciprocal MYO18A fusion partner is a novel candidate gene in the growing list of reciprocal MLL fusions.

JAK2 Inhibition: Reviewing a New Therapeutical Option in Myeloproliferative Neoplasms

JAK2 is a tyrosine kinase gene that plays an essential role in the development of normal haematopoiesis. Hyperactivation of JAK2 occurs in myeloproliferative neoplasms by different mechanisms. As a consequence, JAK2 inhibitors have been designed to suppress the cytokine signalling cascade caused by the constitutive activation of JAK2. In clinical trials, JAK2 inhibitors are efficient in decreasing spleen size, controlling clinical symptoms, and improving quality of life in patients with myeloproliferative neoplasms. However, JAK2 inhibitors are unable to target uncommitted hematopoietic progenitors responsible of the initiation of the myeloproliferative disease. It is expected that, in order to cure the myeloproliferative disease, JAK2 inhibitors should be combined with other drugs to target simultaneously different pathways and to target the initiator hematopoietic cell population in myeloproliferative disorders. Taking advantage of the inhibition of the cytokine cascade of JAK2 inhibitors, these compounds are going to be used not only to treat patients with hematological neoplasms but may also be beneficial to treat patients with rheumatoid arthritis or other inflammatory diseases.

Centrosomal targeting of tyrosine kinase activity does not enhance oncogenicity in chronic myeloproliferative disorders

Constitutive tyrosine kinase activation by reciprocal chromosomal translocation is a common pathogenetic mechanism in chronic myeloproliferative disorders. Since centrosomal proteins have been recurrently identified as translocation partners of tyrosine kinases FGFR1, JAK2, PDGFRα and PDGFRβ in these diseases, a role for the centrosome in oncogenic transformation has been hypothesized. In this study, we addressed the functional role of centrosomally targeted tyrosine kinase activity. First, centrosomal localization was not routinely found for all chimeric fusion proteins tested. Second, targeting of tyrosine kinases to the centrosome by creating artificial chimeric fusion kinases with the centrosomal targeting domain of AKAP450 failed to enhance the oncogenic transforming potential in both Ba/F3 and U2OS cells, although phospho-tyrosine-mediated signal transduction pathways were initiated at the centrosome. We conclude that the centrosomal localization of constitutively activated tyrosine kinases does not contribute to disease pathogenesis in chronic myeloproliferative disorders.

Discovery of 3-(2,6-dichloro-3,5-dimethoxy-phenyl)-1-{6-[4-(4-ethyl-piperazin-1-yl)-phenylamino]-pyrimidin-4-yl}-1-methyl-urea (NVP-BGJ398), a potent and selective inhibitor of the fibroblast growth factor receptor family of receptor tyrosine kinase

A novel series of N-aryl-N'-pyrimidin-4-yl ureas has been optimized to afford potent and selective inhibitors of the fibroblast growth factor receptor tyrosine kinases 1, 2, and 3 by rationally designing the substitution pattern of the aryl ring. On the basis of its in vitro profile, compound 1h (NVP-BGJ398) was selected for in vivo evaluation and showed significant antitumor activity in RT112 bladder cancer xenografts models overexpressing wild-type FGFR3. These results support the potential therapeutic use of 1h as a new anticancer agent.

The kinase inhibitor TKI258 is active against the novel CUX1-FGFR1 fusion detected in a patient with T-lymphoblastic leukemia/lymphoma and t(7;8)(q22;p11)

We report a patient with T-lymphoblastic leukemia/lymphoma and a t(7;8)(q22;p11). CUX1 was identified as the fusion partner of FGFR1 by fluorescence in situ hybridization and 5' RACE-PCR. We further investigated this novel FGFR1 fusion using the interleukin-3 (IL-3) dependent Ba/F3 cell line and demonstrated IL-3 independent cell growth of CUX1-FGFR1 expressing cells. TKI258 and PKC412 potently inhibited proliferation of CUX1-FGFR1 transformed Ba/F3 cells. This growth inhibition was shown to be mediated by inhibition of CUX1-FGFR1 kinase activity for TKI258 but not PKC412. In summary, we identified a novel CUX1-FGFR1 fusion oncogene in a patient with the 8p11 myeloproliferative syndrome and demonstrated its transforming potential in the Ba/F3 cell line. Our in vitro data support the further investigation of TKI258 for the treatment of constitutively active FGFR1 fusion proteins.

Roles of fibroblast growth factor receptors in carcinogenesis

The fibroblast growth factor receptors (FGFR) play essential roles both during development and in the adult. Upon ligand binding, FGFRs induce intracellular signaling networks that tightly regulate key biological processes, such as cell proliferation, survival, migration, and differentiation. Deregulation of FGFR signaling can thus alter tissue homeostasis and has been associated with several developmental syndromes as well as with many types of cancer. In human cancer, FGFRs have been found to be deregulated by multiple mechanisms, including aberrant expression, mutations, chromosomal rearrangements, and amplifications. In this review, we will give an overview of the main FGFR alterations described in human cancer to date and discuss their contribution to cancer progression.

BCR-ABL-negative chronic myeloid leukemia

Constitutive activation of protein tyrosine kinases plays a central role in the pathogenesis of myeloproliferative disorders, including BCR-ABL-negative chronic myeloid leukemia. Current research is focused on elucidating the full spectrum of causative mutations in this rare, heterogeneous disease. Activated tyrosine kinases are excellent targets for signal transduction therapy, and an accurate diagnosis including morphology, karyotyping, and molecular genetics will become increasingly important to direct individualized treatment. In addition, new molecular findings need to be incorporated into disease classification systems.

Biphenotypic hematologic malignancy: a case report of the 8p11 myeloproliferative syndrome in a child

The 8p11 myeloproliferative syndrome, also known as stem cell leukemia/lymphoma, is a rare, atypical, myeloproliferative disorder and lymphoid malignancy associated with chromosomal abnormalities involving the 8p11 chromosomal band. Translocations associated with this syndrome result in the fusion of the fibroblast growth factor receptor 1 (FGFR 1) gene with various partners, resulting in ligand-independent FGFR activity. To date, 8 partner genes have been identified in association with FGFR1 rearrangements. The most frequent FGFR1 translocation partner is the zinc finger gene ZNF198 located at 13q11. Disease phenotypes associated with this translocation include poor prognosis and transformation to acute leukemia and non-Hodgkin lymphoma. In common with a T-cell phenotype, obtaining and maintaining remission is difficult by conventional chemotherapy. This study describes an illustrative case of 8p11 myeloproliferative syndrome/stem cell leukemia/lymphoma outlining its chief features and historical developments.

Genomic alterations of primary tumor and blood in invasive ductal carcinoma of breast

BACKGROUND

Genomic alterations are important events in the origin and progression of various cancers, with DNA copy number changes associated with progression and treatment response in cancer. Array CGH is potentially useful in the identification of genomic alterations from primary tumor and blood in breast cancer patients. The aim of our study was to compare differences of DNA copy number changes in blood and tumor tissue in breast cancer.

METHODS

DNA copy number changes in blood were compared to those in tumor tissue using array-comparative genomic hybridization in samples obtained from 30 breast cancer patients. The relative degree of chromosomal changes was analyzed using log2 ratios and data was validated by real-time polymerase chain reaction.

RESULTS

Forty-six regions of gains present in more than 30% of the tissues and 70 regions of gains present in more than 30% of blood were identified. The most frequently gained region was chromosome 8q24. In total, agreement of DNA copy numbers between primary tumor and blood was minimal (Kappa = 0.138, p < 0.001).

CONCLUSION

Although there was only a slight agreement of DNA copy number alterations between the primary tumor and the blood samples, the blood cell copy number variation may have some clinical significance as compared to the primary tumor in IDC breast cancer patients.

Chromosome 8p11.2 translocations: prevalence, FISH analysis for FGFR1 and MYST3, and clinicopathologic correlates in a consecutive cohort of 13 cases from a single institution

Chromosome 8p11.2 translocations result in diverse oncogenic fusion genes involving FGFR1 or MYST3. Among 24,262 unique patient cytogenetic studies performed at the Mayo Clinic, 8p11.2 translocations were identified in 14 cases ( approximately 0.06%). FISH analysis was performed in 13 patients (12 had myeloid neoplasms) and revealed abnormalities of MYST3 (n = 4) or FGFR1 (n = 4) in eight patients. MYST3 abnormalities were associated with acute myeloid leukemia (AML), M4 in three and M6 in one. Three of the four FGFR1-rearranged cases were associated with myeloproliferative neoplasms but none, including the two with sole 8p11.2, displayed the typical phenotype for stem cell leukemia/lymphoma (SCLL) and only one had eosinophilia; the fourth case had AML-M4. FISH did not reveal FGFR1 involvement in the one patient with SCLL. We conclude that neither the SCLL phenotype nor blood eosinophilia is a consistent feature of FGFR1-associated 8p11.2 translocations; conversely, FISH might not always reveal FGFR1 involvement in typical SCLL.

8p11 myeloproliferative syndrome: a review

The 8p11 myeloproliferative syndrome is an aggressive neoplasm associated with chromosomal translocations involving the fibroblast growth factor receptor 1 tyrosine kinase gene on chromosome 8p11-12. By our count, 65 cases are currently reported in the literature. This neoplasm affects patients of all ages, with a slight male predominance. Patients often present with peripheral blood eosinophilia without basophilia. Bone marrow examination commonly is hypercellular, with or without eosinophilia, which usually leads to the initial diagnosis of a myeloproliferative neoplasm. Many patients also present with or develop lymphadenopathy. Lymph node biopsy in these patients has commonly shown lymphoblastic leukemia/lymphoma, most often reported as being of T-cell lineage, but bilineal myeloid/T-cell lymphomas and less often a myeloid sarcoma are also reported. The natural history of this neoplasm is to evolve into acute leukemia, usually of myeloid or mixed lineage, and less frequently of T- or B-lymphoid lineage. The prognosis is poor despite aggressive chemotherapy, with a few patients achieving long clinical remission after stem cell transplantation. At the molecular level, all cases carry a chromosomal abnormality involving the fibroblast growth factor receptor 1 (FGFR1) gene at chromosome 8p11, where 10 translocations and 1 insertion have been identified. These abnormalities disrupt the FGFR1 and various partner genes, and result in the creation of novel fusion genes and chimeric proteins. The latter include the N-terminal portion of the partner genes and the C-terminal portion of FGFR1. The most common partner is ZNF198 on chromosome 13q12. In the current World Health Organization classification, the 8p11 myeloproliferative syndrome is designated as "myeloid and lymphoid neoplasms with FGFR1 abnormalities."

Molecular monitoring of 8p11 myeloproliferative syndrome in an infant

The 8p11 myeloproliferative syndrome is a rare hematologic malignancy derived from a pluripotent hematopoietic stem cell associated with rearrangements involving the fibroblast growth factor receptor 1 (FGFR1) gene located on chromosome 8p11. The most common translocation, t(8;13) (p11;q13), results in a ZNF198-FGFR1 fusion gene and constitutively active FGFR1 tyrosine kinase activity. Typical pathologic findings include myeloid hyperplasia, lymphadenopathy, precursor T-lymphoblastic lymphoma, and eosinophilia. The disease is usually associated with an aggressive course and progression to acute myeloid leukemia is frequent. We report here the first case of 8p11 myeloproliferative syndrome in an infant and demonstrate the value of molecular testing in the diagnosis and minimal disease monitoring of this rare disease.

Phosphorylation of the SSBP2 and ABL proteins by the ZNF198-FGFR1 fusion kinase seen in atypical myeloproliferative disorders as revealed by phosphopeptide-specific MS

The ZNF198-fibroblast growth factor receptor-1 (FGFR1) fusion kinase is a constitutively activated tyrosine kinase associated with a specific atypical myeloproliferative disease. The chimeric protein localizes to the cytoplasm, unlike the wild type FGFR1 receptor kinase, and presumably inappropriately phosphorylates specific targets as part of the oncogenic signaling cascade. Other than known targets of the FGFR1 kinase itself, few specific targets of ZNF198-FGFR1 have been identified. Using a genetically engineered HEK 293 cell system, we have identified proteins that are specifically phosphorylated in the presence of the fusion kinase using anti-phosphotyrosine immunoprecipitation and MS. Compared with 293 cells expressing exongenous wild type FGFR1, ZNF198-FGFR1 is associated with phosphorylation of several proteins including SSBP2, ABL, FLJ14235, CALM and TRIM4 proteins. The specificity of the phosphorylation events in the SSBP2 and ABL proteins, which have previously been implicated in leukemogenesis, was further confirmed independently using immunoprecipitation with protein-specific antibodies and Western blotting. The MS analysis also identified the phosphorylation events in the ZNF198 moiety in the chimeric protein that might be related to its function. These studies identify the intersection of several different leukemia-related pathways in the development of this myeloproliferative disorder and provide new insights into the substrates of FGFR1 under defined conditions.

Philadelphia chromosome-negative chronic myeloproliferative disease

Session 2 of the 2007 Workshop of the Society for Hematopathology/European Association for Haematopathology was focused on Philadelphia chromosome-negative chronic myeloproliferative diseases (Ph- MPDs), recently termed chronic myeloproliferative neoplasms. The presented and submitted cases highlighted some important issues and also impending problems associated with the diagnosis and classification. Cases included predominantly rare entities like chronic eosinophilic leukemia and related disorders, chronic neutrophilic leukemia, and others with specific genetic abnormalities that allowed molecularly targeted therapy. In this context, the distinctive role of a positive JAK2(V617F) mutation for the diagnosis of Ph- MPD was underscored, including entities with a low allele burden and the discrimination from reactive disorders (autoimmune myelofibrosis, reactive thrombocytosis). Although novel genetic and molecular approaches have significantly improved the way we classify Ph- MPD, a combined clinicopathologic approach, including representative bone marrow specimens, still remains the yardstick for diagnosis.

The t(1;9)(p34;q34) and t(8;12)(p11;q15) fuse pre-mRNA processing proteins SFPQ (PSF) and CPSF6 to ABL and FGFR1

We have investigated two patients with acquired chromosomal rearrangements, a male presenting with a t(1;9)(p34;q34) and B cell progenitor acute lymphoid leukemia and a female presenting with a t(8;12)(p11;q15) and the 8p11 myeloproliferative syndrome. We determined that the t(1;9) fused ABL to SFPQ (also known as PSF), a gene mapping to 1p34 that encodes a polypyrimidine tract-binding protein-associated splicing factor. The t(8;12) fused CPSF6, a cleavage and polyadenylation specificity factor, to FGFR1. The fusions were confirmed by amplification of the genomic breakpoints and RT-PCR. The predicted oncogenic products of these fusions, SFPQ-ABL and CPSF6-FGFR1, are in-frame and encode the N-terminal domain of the partner protein and the entire tyrosine kinase domain and C-terminal sequences of ABL and FGFR1. SFPQ interacts with two FGFR1 fusion partners, ZNF198 and CPSF6, that are functionally related to the recurrent PDGFRalpha partner FIP1L1. Our findings thus identify a group of proteins that are important for pre-mRNA processing as fusion partners for tyrosine kinases in hematological malignancies.