Combined translocation with ZNF198-FGFR1 gene fusion and deletion of potential tumor suppressors in a myeloproliferative disorder

Pediatric T-cell acute lymphoblastic leukemia

The most common pediatric malignancy is acute lymphoblastic leukemia (ALL), of which T-cell ALL (T-ALL) comprises 10-15% of cases. T-ALL arises in the thymus from an immature thymocyte as a consequence of a stepwise accumulation of genetic and epigenetic aberrations. Crucial biological processes, such as differentiation, self-renewal capacity, proliferation, and apoptosis, are targeted and deranged by several types of neoplasia-associated genetic alteration, for example, translocations, deletions, and mutations of genes that code for proteins involved in signaling transduction, epigenetic regulation, and transcription. Epigenetically, T-ALL is characterized by gene expression changes caused by hypermethylation of tumor suppressor genes, histone modifications, and miRNA and lncRNA abnormalities. Although some genetic and gene expression patterns have been associated with certain clinical features, such as immunophenotypic subtype and outcome, none has of yet generally been implemented in clinical routine for treatment decisions. The recent advent of massive parallel sequencing technologies has dramatically increased our knowledge of the genetic blueprint of T-ALL, revealing numerous fusion genes as well as novel gene mutations. The challenges now are to integrate all genetic and epigenetic data into a coherent understanding of the pathogenesis of T-ALL and to translate the wealth of information gained in the last few years into clinical use in the form of improved risk stratification and targeted therapies. Here, we provide an overview of pediatric T-ALL with an emphasis on the acquired genetic alterations that result in this disease. © 2016 Wiley Periodicals, Inc.

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.

[Clinical and gene involved of one case of 8p11 myeloproliferative syndrome with ins(13;8)(q12;p11p23)]

OBJECTIVE

To improve the understanding of patients with 8p11 myeloproliferative syndrome (EMS) harboring ins(13;8)(q12;p11p23)/ZNF198 -FGFR1.

METHODS

We reported here a 8p11 EMS case and provided more details on the clinical and molecular features of ins(13;8)(q12;p11p23)/ZNF198-FGFR1，full length ZNF198-FGFR1 was cloned by overlap extension PCR method，and the literatures on this topic were reviewed.

RESULTS

Clinically, the case with ins(13;8)(q12;p11p23)/ZNF198-FGFR1 had distinct hematological and clinical characteristics: hyperleukocytosis, myeloid hyperplasia，widespread adenopathy and lymphoma; Fluorescence in situ hybridization (FISH) disclosed the positive FGFR1 gene rearrangement; Further molecular studies confirmed a mRNA in-frame fusion between exon 17 of the ZNF198 gene and exon 9 of FGFR1 gene ，the full length ZNF198-FGFR1 was composed of a NH2 terminus of ZNF198 including the ZNF and proline-rich domains, whereas the COOH terminus of FGFR1 included 2 tyrosine kinase domains.

CONCLUSION

EMS with ins(13;8)(q12;p11p23)/ZNF198 -FGFR1 was a very rare， distinct myeloproliferative neoplasm, the fusion gene and chimeric protein with constitutive activation of the FGFR1 tyrosine kinase.

Development of covalent inhibitors that can overcome resistance to first-generation FGFR kinase inhibitors

The human FGF receptors (FGFRs) play critical roles in various human cancers, and several FGFR inhibitors are currently under clinical investigation. Resistance usually results from selection for mutant kinases that are impervious to the action of the drug or from up-regulation of compensatory signaling pathways. Preclinical studies have demonstrated that resistance to FGFR inhibitors can be acquired through mutations in the FGFR gatekeeper residue, as clinically observed for FGFR4 in embryonal rhabdomyosarcoma and neuroendocrine breast carcinomas. Here we report on the use of a structure-based drug design to develop two selective, next-generation covalent FGFR inhibitors, the FGFR irreversible inhibitors 2 (FIIN-2) and 3 (FIIN-3). To our knowledge, FIIN-2 and FIIN-3 are the first inhibitors that can potently inhibit the proliferation of cells dependent upon the gatekeeper mutants of FGFR1 or FGFR2, which confer resistance to first-generation clinical FGFR inhibitors such as NVP-BGJ398 and AZD4547. Because of the conformational flexibility of the reactive acrylamide substituent, FIIN-3 has the unprecedented ability to inhibit both the EGF receptor (EGFR) and FGFR covalently by targeting two distinct cysteine residues. We report the cocrystal structure of FGFR4 with FIIN-2, which unexpectedly exhibits a "DFG-out" covalent binding mode. The structural basis for dual FGFR and EGFR targeting by FIIN3 also is illustrated by crystal structures of FIIN-3 bound with FGFR4 V550L and EGFR L858R. These results have important implications for the design of covalent FGFR inhibitors that can overcome clinical resistance and provide the first example, to our knowledge, of a kinase inhibitor that covalently targets cysteines located in different positions within the ATP-binding pocket.

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.

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 t(17;22)(q21;q12) with partial ETV4 deletion in a soft tissue Ewing sarcoma

Cytogenetic analysis of a lumbar soft tissue Ewing sarcoma (ES) in a 7-month-old female child showed a t(17;22)(q21;q12), a rare translocation leading to an EWSR1-ETV4 chimeric transcript. These findings were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization (FISH) techniques. The breakpoints were characterized by direct sequencing of the chimeric fusion gene. Tumor genotyping using the Affymetrix Genome-Wide Human single nucleotide polymorphism (SNP) array 6.0 Genechip identified deletions of both chromosomal regions involved in the translocation, resulting in partial deletion of ETV4, but an uninvolved EWSR1 gene. The creation of a fusion between EWSR1 and an ETS family gene consecutive to a chromosomal translocation is characteristic of the Ewing family of tumors (EFT). This is the first report of a deletion involving the two breakpoints in an EWS-ETS translocation. To date, only two cases of t(17;22)(q21;q12) in Ewing sarcoma have been reported, with no associated deletion. Interestingly, both cases had also occurred in soft tissue tumors, which are less common than their bone-involving counterparts.

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.

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."

Hematopoietic neoplastic diseases develop in C3H/He and C57BL/6 mice after benzene exposure: strain differences in bone marrow tissue responses observed using microarrays

In this study, Trp53-deficient and wild-type mice of both C57BL/6 and C3H/He strains were exposed to benzene (33, 100, and 300 ppm; 6h/day, 5 days/week for 26 weeks) and then observed for lifetime. As results, first, the incidence of nonthymic lymphomas in C57BL/6 mice and acute myeloid leukemias (AMLs) in C3H/He mice showed linear responses at the lower exposure level in Trp53-deficient mice; second, the incidence of thymic lymphomas in C57BL/6 mice and nonthymic lymphomas in C3H/He mice increased without a plateau-like ceiling; thus, the former equivocal induction of hematopoietic neoplasms (HPNs) in the case of low-dose benzene exposure was assumed to be based on the DNA repair potential in wild-type mice, and the latter limited increase in HPNs in the case of high-dose benzene exposure was considered to be due to excessive apoptosis in wild-type mice. Concerning the incidence of AMLs, though a dose of 300 ppm benzene inhalation induced 9% AMLs in wild-type C3H/He mice-AML-prone, it induced AMLs in 38% of Trp53-deficient C3H/He mice. Because AMLs were also observed in Trp53-deficient mice, including in the C57BL/6 mice, benzene exposure may also be a potent inducer of AMLs in mice with some strain differences. In the present study, to elucidate the hematopoietic stem cell-specific, aryl hydrocarbon-receptor-related low-dose adverse effect, global gene expression in the bone marrow was analyzed at 28 days after 2-week-intermittent exposure to 150 mg/kg b.w. benzene, by gavage, i.e., equivalent to the above inhalation protocol with 300 ppm. We observed two conceptually different gene expression profiles; "common gene profiles" (CGPs) shared among mice in each group, and "stochastic gene profiles" (SGPs), i.e., unique union genes from one individual mouse to another. The CGPs of the experimental group and the SGPs of each individual mouse were separately characterized by individual assay. Concerning the CGPs, reciprocal strain differences between C3H/He and C57BL/6 mice in expression gene profiles, both plausible for leukemogenesis, were identified; namely, dominant downmodulations of Sltm and Cryl1, related to suppression of apoptosis and genomic instability in C3H/He mice, respectively, and dominant downmodulations of Atrx/rad54 and Kdm2a, related to a decrease in DNA repair and genomic instability, respectively, in C57BL/6 mice. These findings imply that these reciprocal gene expression differences induced by benzene exposure may lead each strain to undergo different hematopoietic neoplastic pathways. In contrast, each individual mouse often shows a unique SGP. SGPs often include transcription factors, which regulate reciprocal signaling pathways including further SGPs. Among them, apoptosis-related genes expressed in C57BL/6 mice and those in C3H/He mice were attributable to different combinations of SGPs. Such stochastic case-by-case gene expression may be in good agreement with the individual and strain differences observed following benzene exposure. Because gene chip microarray techniques can elucidate stochastic changes in gene expression profiles, possible stochastic toxicology and its future role are discussed.

Genetic fingerprinting of the development and progression of T-cell lymphoma in a murine model of atypical myeloproliferative disorder initiated by the ZNF198-fibroblast growth factor receptor-1 chimeric tyrosine kinase

A mouse model of human ZNF198-fibroblast growth factor receptor-1 (FGFR1) stem cell leukemia lymphoma has been developed to investigate mechanisms of oncogenesis and progression. Using array-based comparative genomic hybridization, we followed disease progression after serial transplantation of ZNF198-FGFR1-transformed stem cells that give rise to a distinct myeloproliferative disorder and T-lymphoblastic leukemia. A consistent, frequently homozygous, chr14:53880459-55011545 deletion, containing the T-cell receptor alpha and delta genes, was identified in the bone marrow, spleen, and lymph nodes in all cases. The absence of cell-surface T-cell receptor alpha in tumor cells precludes CD3 recruitment, resulting in loss of a functional T-cell receptor complex, supporting the idea that prevention of maturation of CD4(+)/CD8(+) double-positive immature T cells is important in ZNF198-FGFR1 disease development. Up-regulation of the B-cell line 2, interleukin 7 receptor alpha and interleuking 2 receptor alpha prosurvival genes in these undifferentiated tumor precursor cells suggests one mechanism that allows them to escape apoptosis in the thymus. Thus, we have defined an important event in the process of ZNF198-FGFR1-induced T-cell leukemia.

A new large deletion in the DFNB1 locus causes nonsyndromic hearing loss

Mutations in the GJB2 gene encoding the gap junction protein connexin 26 are responsible for up to 30% of all cases of autosomal recessive nonsyndromic hearing impairment (HI) with prelingual onset in most populations. The corresponding locus DFNB1, located on chromosome 13q11-q12, is also affected by three distinct deletions. These deletions extended distally to GJB2, which remains intact. We report a novel large deletion in DFNB1 observed in a patient presenting profound prelingual HI. This deletion was observed in trans to a GJB2 mutated allele carrying the p.Val84Met (V84M) mutation and was shown to be associated with hearing loss. The deletion caused a false homozygosity of V84M in the proband. Quantification of alleles by quantitative fluorescent multiplex PCR (QFM-PCR) enabled us to study the breakpoints of the deletion. The deleted segment extended through at least 920kb and removed the three connexin genes GJA3, GJB2 and GJB6. The distal breakpoint inside intron 2 of CRYL1 gene differed from the breakpoints of the known DFNB1 deletions. This case highlights the importance of screening for large deletions in molecular studies of GJB2.

Rearrangements involving 12q in myeloproliferative disorders: possible role of HMGA2 and SOCS2 genes

We report two cases of translocation associated with deletion on derivative chromosomes in atypical myeloproliferative disorder (MPD). In a MPD with t(3;12)(q29;q14), the rearrangement targeted the HMGA2 locus at 12q14 and deleted a region of about 1.5 megabases (Mb) at 3q29. In an MPD with t(9;12)(q13 approximately q21;q22) and JAK2 V617F mutation, array comparative genomic hybridization delineated a deletion of about 3 Mb at 9q13 approximately q21 and a deletion of about 2 Mb at 12q22 containing SOCS2. These results show that close examination of translocations in hematopoietic diseases may reveal associated microdeletions. The role of these deletions is discussed.