Ectopic expression of MAFB gene in human myeloma cells carrying (14;20)(q32;q11) chromosomal translocations

Chromosome 14q +, which represents a chromosomal rearrangement involving the immunoglobulin heavy chain gene (IgH) locus, is a genetic hallmark of human multiple myeloma (MM). Here, we report the identification of (14;20)(q32;q11) chromosomal translocations found in MM cells. Double color fluorescence in situ hybridization analyses pinpointed the breakpoints at the 20q11 locus in two MM cell lines within a length of at most 680 kb between the KIAA0823 and MAFB gene loci. Among the transcribed sequences in the vicinity of the breakpoints, an ectopic expression of the MAFB gene, which is located at 450 - 680 kb telomeric to one of the breakpoints and encodes a member of the MAF family basic region / leucine zipper transcription factor, was demonstrated to be associated with t(14;20). This finding, together with that of a previous study describing its transforming activity, suggests that the MAFB gene may be one of the targets deregulated by regulatory elements of the IgH gene as a result of t(14;20).

Coduplication of the MLL and FLT3 genes in patients with acute myeloid leukemia

Tandem duplication (TD) of the MLL or FLT3 gene in acute myeloid leukemia (AML) has been reported. We examined whether TD of these two genes occurs simultaneously. We analyzed 13 AML and 2 myelodysplastic syndrome patients, including 6 adult patients with trisomy 11 and 9 pediatric patients with TD of the FLT3 gene, using RT-PCR followed by sequencing. Among these, TD of the MLL and FLT3 genes was found in 5 and 10 patients, respectively. Notably, TD of both the MLL and FLT3 genes (coduplication) was detected in two AML patients, who died 6 and 14 months after diagnosis. TD of these two genes in AML is rare; thus, coduplication of these genes in the same patient is predicted to be very rare. Although the mechanisms of TD of both genes are different, development of TD of both genes may be related to an unknown similar etiology in leukemia because the frequency of coduplication of these genes in a single patient is considered to be very low. Further studies of the coduplication of these genes in AML patients may lead to the clarification of its mechanism and clinical implications.

Myelodysplastic syndrome with clonal eosinophilia accompanied by eosinophilic pulmonary interstitial infiltration

We report a case of de novo myelodysplastic syndrome with clonal eosinophilia (MDS-Eo) and eosinophilic pulmonary interstitial infiltration, confirmed by autopsy. Cytogenetic study using Giemsa banding identified 47,XY,+1,der(1;7)(q10;p10),+8 in the marrow cells. Simple Giemsa staining revealed the same chromosomal aberration in metaphase spreads with eosinophilic granules, indicating the clonal proliferation of eosinophils. To our knowledge, our case is the 6th reported case of MDS-Eo with cytogenetically confirmed clonal eosinophilia, and the first autopsy of MDS-Eo. A review of the literature combined with our findings suggests that this type of chromosomal aberration might be involved in the as yet unknown pathogenesis of MDS-Eo.

The CDCREL1 gene fused to MLL in de novo acute myeloid leukemia with t(11;22)(q23;q11.2) and its frequent expression in myeloid leukemia cell lines

We report on an adult patient with de novo acute myeloid leukemia (AML) with a t(11;22)(q23;q11.2) involving CDCREL1 and MLL genes. Reverse transcriptase (RT)-polymerase chain reaction (PCR) followed by direct sequencing analysis revealed the MLL-CDCREL1 fusion transcript in his leukemic cells. Analysis of the fusion transcript showed that exon 6 of MLL was fused to exon 4 of CDCREL1, which contains an AT-hook domain of MLL and a GTP binding domain of CDCREL1. To investigate the roles of CDCREL1 further, we examined the expression of the CDCREL1 gene in various cell lines. Expression of CDCREL1 was detected in 11 (85%) of 13 AML cell lines and 3 (21%) of 14 acute lymphoblastic leukemia (ALL) cell lines, but none of 11 EB virus transformed B-cell lines by RT-PCR. The expression rate of CDCREL1 was significantly higher in AML cell lines than in ALL cell lines (P = 0.0035). Platelet glycoprotein 1B beta (GP1B beta), which is located downstream of CDCREL1 and is cotranscribed with CDCREL1 due to a nonconsensus polyadenylation sequence, was expressed in all these cell lines. The higher expression rate of CDCREL1 in AML cell lines than in ALL cell lines suggests that this gene may play some role in myeloid leukemogenesis.

IRTA1 and IRTA2, novel immunoglobulin superfamily receptors expressed in B cells and involved in chromosome 1q21 abnormalities in B cell malignancy

Abnormalities of chromosome 1q21 are common in B cell malignancies, but their target genes are largely unknown. By cloning the breakpoints of a (1;14) (q21;q32) chromosomal translocation in a myeloma cell line, we have identified two novel genes, IRTA1 and IRTA2, encoding cell surface receptors homologous to the Fc and inhibitory receptor families. Both genes are selectively expressed in mature B cells: IRTA1 in marginal zone B cells and IRTA2 in centrocytes, marginal zone B cells, and immunoblasts. As a result of the t(1;14), IRTA1 is fused to the immunoglobulin Calpha domain to produce a chimeric IRTA1/Calpha fusion protein. In tumor cell lines with 1q21 abnormalities, IRTA2 expression is deregulated. Thus, IRTA1 and IRTA2 are novel immunoreceptors implicated in B cell development and lymphomagenesis.

Identification of an alternatively spliced form of the mouse AML1/RUNX1 gene transcript AML1c and its expression in early hematopoietic development

Acute myeloid leukemia 1 (AML1: or runt-related transcription factor, RUNX1) encodes the DNA binding subunit of the heterodimering transcription factor complex PEBP2 (CBF), which plays an essential role for definitive hematopoiesis. Transcription of AML1 is controlled by two distinct promoter regions, which results in the generation of the respective AML1b and AML1c isoforms. Here we report the isolation of the mouse homologue of human AML1c, whose unique N-terminus is 100% identical at the amino acid level to its human counterpart and 63 and 37% identical to the respective family members AML2 and AML3. Semiquantitative RT-PCR assay on mouse embryonic stem cell clones during in vitro differentiation and Northern blot analysis of a mouse embryo revealed that AML1b is expressed in undifferentiated ES cells and upregulated in the early developmental stage, in contrast to the gradual upregulation and steady maintenance of AML1c expression during embryogenesis. In addition, maintenance of AML1c expression depended on the presence of active AML1 allele(s) while that of AML1b did not. Thus, these two AML1 isoforms driven by their respective promoters are differentially expressed and are likely to have distinct functions in early hematopoietic development.

Langerhans cell histiocytosis of an adult with tumors in liver and spleen

We describe a 58-year-old male with multiple histiocytic tumors in the liver and spleen. Multiple tumors in the liver and spleen were seen by image analysis, and splenectomy showed a large splenic tumor with a small nodule and a swelling lymph node in the hilus. Histological features of the tumors in the liver and spleen revealed proliferation of histiocytic cells with large and clear cytoplasm and a horseshoe-shaped nucleus. Immunohistochemical studies revealed the presence of S-100 protein and CD1a antigen in the tumor cells, and neither lymphocytic marker nor lysozyme was detected. No definite Birbeck granules were seen ultrastructurally, thus the tumor cells could be classified into Langerhans cell type without Birbeck granules. Administration of adriamycin, vincristine, cyclophosphamide and prednisolone reduced size and number of the liver tumors, and the histiocytic cells could not be detected in repeatedly biopsied tissue from liver tumor. We present the clinical, immunohistological and cytological features in a visceral type of adult Langerhans cell histiocytosis, which responded well to chemotherapy.

Detection of t(14; 18)(q32;q21) in hyperdiploid cells by fluorescence in situ hybridization in a patient with Hodgkin disease

The most frequent nonrandom chromosome rearrangements in B-cell non-Hodgkin lymphoma (NHL) is the t(14;18)(q32;q21) found in follicular lymphomas. The t(14;18) in Hodgkin disease (HD) was rarely observed using cytogenetic techniques. Although Southern blot analysis failed to demonstrate the t(14;18), there have been conflicting reports concerning the occurrence of the translocation using polymerase chain reaction (PCR) methods in HD. In some HD tissues, the translocation might be derived from background lymphocytes rather than Hodgkin and Reed-Sternberg (HRS) cells, because B-cells with t(14;18) are regularly generated in normal individuals. However, the cells bearing the translocation have remained unidentified. We describe a patient with HD who showed t(14;18) in hyperdiploid cells using fluorescence in situ hybridization (FISH) and HRS cells which were strongly positive for BCL2 by immunohistochemistry. These findings suggest that HRS cells may have a t(14;18).

A novel gene, MEL1, mapped to 1p36.3 is highly homologous to the MDS1/EVI1 gene and is transcriptionally activated in t(1;3)(p36;q21)-positive leukemia cells

The reciprocal translocation t(1;3)(p36;q21) occurs in a subset of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), which is frequently characterized by trilineage dysplasia, in particular dysmegakaryocytopoiesis, and poor prognosis. Previously, the breakpoint cluster region (BCR) at 3q21 was identified within a 60-kilobase (kb) region centromeric to the BCR of 3q21q26 syndrome and that at 1p36.3 within a 90-kb region. In this study, genes were searched near the breakpoints at 1p36.3, and a novel gene was isolated that encoded a zinc finger protein with a PR domain, which is highly homologous to the MDS1/EVI1 gene. The novel gene, designated as MEL1 (MDS1/EVI1-like gene 1), with 1257 amino acid residues is 64% similar in nucleotide and 63% similar in amino acid sequences to MDS1/EVI1 with the same domain structure. The MEL1 gene is expressed in leukemia cells with t(1;3) but not in other cell lines or bone marrow, spleen, and fetal liver, suggesting that MEL1 is specifically in the t(1;3)(p36;q21)-positive MDS/AML. On the basis of the positional relationship between the EVI1 and MEL1 genes in each translocation, it was suggested that both genes are transcriptionally activated by the translocation of the 3q21 region with the Ribophorin I gene. Because of the transcriptional activation of the EVI1 family genes in both t(1;3)(p36;q21)-positive MDS/AML and 3q21q26 syndrome, it is suggested that they share a common molecular mechanism for the leukemogenic transformation of the cells.

Rare alteration of genomic structure or expression of the DPC4 gene in myelogenous leukemias

We examined homozygous deletion, point mutation and expression of DPC4 gene, a recently isolated candidate pancreatic tumor suppressor gene, in 53 patients with myelogenous leukemias and 5 cell lines. The patients consisted of 34 cases of chronic myelogenous leukemia including 22 in the chronic phase, 3 in the accelerated phase, and 9 in blastic crisis, and 19 with acute myelogenous leukemia including 9 at the initial presentation and 10 at relapse. Polymerase chain reaction (PCR)-based deletion analysis for DPC4 exon 8 and PCR-single strand conformation polymorphism study for the entire coding region were carried out. Homozygous deletion or subtle mutation was not detected in any of the samples examined. However, 3 patients with various clinical phases showed a decrease of DPC4 expression. These results suggest that DPC4 alteration is not a crucial event in the development or the progression of myelogenous leukemias.

c-myc overexpression is not mandatory in aggressive-phase multiple myeloma with Burkitt's type translocation

This report concerns a case of aggressive-phase multiple myeloma (AGMM) with Burkitt's type translocation t(8;14)(q24;q32), detected by Giemsa-banding. Double-color fluorescence in situ hybridization identified the breakpoint on 8q24 at a comparatively centromeric site, which was at least 300 kb and possibly 600 kb distant from the c-myc coding region. The breakpoint on 8q24 of the present case was far removed from that seen in other B-cell neoplasms with t(8;14)(q24;q32). Despite the presence of t(8;14)(q24;q32), neither rearrangement nor overexpression of the c-myc gene was observed in this case. Although our case may be a special case of multiple myeloma, it nevertheless suggests that overexpression of c-myc is not mandatory in an AGMM patient with Burkitt's type translocation. t(8;14)(q24;q32) which was seen in our case represents one of the first to be mapped at more than 300 kb 5' of c-myc. It should also be noted that this result could mean that a centromeric boundary 5' of c-myc exists where the influence of the immunoglobulin (Ig) H enhancer on c-myc transcription is not effective.

Isolation, tissue distribution, and chromosomal localization of the human activation-induced cytidine deaminase (AID) gene

The gene encoding activation-induced cytidine deaminase (AID), a member of the cytidine deaminase family, was isolated from a murine B cell lymphoma line, CH12F3-2, induced by combined stimulation of TGF-beta, IL-4, and CD40L. We have isolated the human orthologue of mouse AID cDNA, which has an open reading frame of 198 residues containing a conserved cytidine deaminase motif. The amino acid sequence of human AID is 92% identical to that of mouse AID. RT-PCR analysis of 15 human tissues showed that AID mRNA is expressed strongly in lymph nodes and tonsils. The complete human AID gene consisting of five exons was isolated and mapped to chromosome 12p13 by fluorescence in situ hybridization.

Randomized comparison of mobilization kinetics of circulating CD34+ cells between biweekly CHOP and dose-escalated CHOP with the prophylactic use of lenograstim (glycosylated rHuG-CSF) in aggressive non-Hodgkin's lymphoma. The lenograstim/Lymphoma Study Group

High-dose chemotherapy with autologous hematopoietic stem cell transplantation has been expected to result in a promising outcome in high risk aggressive non-Hodgkin's lymphoma (NHL). However, it remains unknown what type of initial chemotherapy is optimal, especially regarding progenitor cell mobilization. Sixty-three untreated patients with aggressive NHL in a high risk group were randomized to either a biweekly arm with 8 cycles of standard CHOP or 6 cycles of the dose-escalated CHOP arm with cyclophosphamide 1.5 g/m2 and doxorubicin 70 mg/m2. Lenograstim (glycosylated rHuG-CSF 2.0 microg/kg/day) was administered daily from day 3 to patients in both arms. The mobilization effect of the two regimens on circulating CD34+ cells was evaluated. Twenty-seven of 29 patients in the biweekly CHOP arm and 33 of 34 patients in the dose-escalated CHOP were assessable. Dose-escalated CHOP yielded a significantly higher number of circulating CD34+ cells in the first cycle compared with biweekly CHOP (p=0.05). The peak number of circulating CD34+ cells with biweekly CHOP did not significantly change from cycle to cycle; however, in dose-escalated CHOP, the peak number of circulating CD34+ cells mobilized after the fifth and sixth cycle was lower than after the first cycle (p=0.07 and 0.009, respectively). Routine conventional-dose chemotherapy and low-dose G-CSF can mobilize sufficient CD34+ cells in patients with aggressive NHL. The mobilization kinetics of circulating progenitor cells in patients with aggressive NHL is dependent on the dosage and schedule of CHOP.

A novel human multiple myeloma-derived cell line, NCU-MM-1, carrying t(2;11)(q11;q23) and t(8;22)(q24;q11) chromosomal translocations with overexpression of c-Myc protein

A novel cell line, designated as NCU-MM-1, was established from a 66-year-old female patient with multiple myeloma (MM) that had shown rapid progression from solitary plasmacytoma to plasma cell leukemia. Interestingly, cytogenetic analysis including fluorescence in situ hybridization analysis disclosed that this cell line carried 2 kinds of chromosomal translocations involving immunoglobulin light chain (IgL) gene loci without the presence of 14q32 translocations (14q+). The Ig lambda locus juxtaposed to the c-MYC locus at 8q24 on the derivative (8) chromosome and a concomitant overexpression of the c-Myc protein was observed. On the derivative (11) chromosome, the Ig kappa locus was also fused to the chromosome 11q23 locus, which is known to be a nonrandom translocation breakpoint in mature B-cell malignancies. The NCU-MM-1 cell line may thus be useful not only for the identification of the responsible proto-oncogene(s) mapped to 11q23, deregulated by the Ig kappa enhancer sequences, but also for clarification of the molecular origin of MM lacking 14q+ chromosomes because IgL rearrangements can physiologically begin to occur in the pre-B-cell stage.

Interstitial deletion of the short arm of chromosome 12 during clonal evolution in myelodysplastic syndrome with t(5;12)(q13;p13) involving the ETV6 gene

We report here a 65-year-old man with a myelodysplastic syndrome (MDS), refractory anemia with excess of blasts. He had received chemotherapy with tegafur for renal carcinoma. Chromosome analysis of bone marrow cells revealed complex karyotypes; del(5)(q13) was observed in all 20 metaphase spreads, and two related aberrations, add(12)(p11) and add(12)(p13), were detected in 13 and 7 cells, respectively. Fluorescence in situ hybridization (FISH) analysis with chromosome-specific DNAs revealed that these alterations originated from a reciprocal translocation (5;12)(q13;p13). Therefore, del(5)(q13), add(12)(p11), and add(12)(p13) were revised as der(5)t(5;12)(q13;p13), der(12)del(12)(p11p13)t(5;12)(q13;p13), and der(12)t(5;12)(q13;p13), respectively. Fluorescence in situ hybridization with a series of cosmid probes spanning the ETV6 gene showed that the 12p13 breakpoint on the der(12)t(5;12)(q13;p13) was located in intron 1, but the exon 1 signal was deleted. Our results suggest that a fusion gene was generated between the 5'-end of an unidentified partner at 5q13 and the 3'-end of ETV6 by t(5;12)(q13;p13), and that the interstitial deletion (12)(p11p13) occurred following t(5;12) during clonal evolution. del(12)(p11p13), including the rearranged ETV6 gene, may be implicated in the progression of MDS.

Induction of chromosomal aberrations and growth-transformation of lymphoblastoid cell lines by inhibition of reactive oxygen species-induced apoptosis with interleukin-6

Etiological evidence, indicating the relationships between the onset of malignant lymphoma and pre-existing chronic inflammation, has been accumulated. For the autonomous growth of malignant tumor, genetic lesions, such as chromosomal aberrations, amplification of oncogenes, and mutations of genes involved in the cell cycle regulation, must be essential. However, how the inflammation promotes the accumulation of genetic lesions and induces the autonomous growth of lymphoid cells remains unclear. Reactive oxygen species released by polymorphonuclear leukocytes and macrophages are factors causing DNA damage in the foci of inflammation, and thus could play a role in lymphomagenesis. The xanthine/xanthine oxidase (X/XOD) system produces a mixture of hydrogen peroxide and superoxide anion extracellularly, and thus serves as an in vitro source of reactive oxygen species. Cell death of lymphoblastoid cell lines (LCLs) was induced with X/XOD treatment in a dose-dependent manner. DNA fragmentation, which is the characteristic feature of apoptosis, was observed in LCLs at 4-8 hours after X/XOD treatment. Among cytokines such as interleukin-6 (IL-6), IL-10, and interferon-gamma, only pretreatment with IL-6 gave LCLs the resistance to X/XOD-induced cell death in a dose-dependent manner. The proportion of apoptotic cells in X/XOD-treated LCL culture was decreased with IL-6 pretreatment by quantification with flow cytometric analysis. Treatment of LCLs with IL-6 for 48 hours up-regulated bcl-2 mRNA expression. Furthermore, the LCLs repeatedly treated with X/XOD and cultured with or without IL-6 showed many more structural abnormalities of chromosomes than those without X/XOD treatment. Colony forming efficiency of X/XOD-treated LCLs with IL-6 was significantly higher than those without IL-6, and even relatively higher than LCLs without X/XOD treatment. IL-6 could support the survival of non-neoplastic B cells and accelerate the malignant transformation of B lineage cells in inflammatory lesions.

The Ikaros gene, a central regulator of lymphoid differentiation, fuses to the BCL6 gene as a result of t(3;7)(q27;p12) translocation in a patient with diffuse large B-cell lymphoma

The BCL6 gene, isolated from the breakpoints of 3q27-associated chromosomal translocations, has been implicated in diffuse large B-cell lymphomas (DLBL). Here we describe the molecular characterization of novel t(3;7)(q27;p12) translocations in 2 patients with DLBL. Molecular genetic analysis of the breakpoint area involving BCL6 revealed the presence of the Ikaros gene, a central regulator of lymphoid differentiation that had been mapped to human chromosome 7 band p13-p11.1. As a molecular consequence of the translocation, the 5' regulatory region of the BCL6 gene was replaced by the putative 5' regulatory region of the Ikaros gene, probably leading to deregulated expression of the BCL6 gene throughout B-cell differentiation. Reverse transcription-polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization (FISH) analyses of a patient sample established that the t(3;7)(q27;p12) results in fusion of the Ikaros and BCL6 genes. This study provides the first evidence that the Ikaros gene is rearranged in human hematopoietic malignant disorders. (Blood. 2000;95:2719-2721)

The p73 gene is less involved in the development but involved in the progression of neuroblastoma

We performed expression, mutation, loss of heterozygosity (LOH) and fluorescence in situ hybridization (FISH) analyses of the p73 gene in neuroblastomas (NBs). Reverse transcription-polymerase chain reaction (RT-PCR) using primers which can detect both the p73alpha and p73beta transcripts was performed on 30 fresh NBs and 22 NB cell lines. Aberrant expression of the p73 gene was found in 4 (25%) of 16 primary tumors found by mass screening and in 10 (71.4%) of 14 primary tumors found clinically. The rates of expression in these two types of tumors were significantly different (p=0.026, Fisher's exact test). The incidence of aberrant expression of the p73 gene was significantly higher in stage IV patients than in stages I, II, III plus IVS patients (p=0.0236, Fisher's exact test). No homozygous deletions or rearrangements of the p73 gene were found in any samples examined. In addition to the polymorphism in exon 2, a silent mutation (codon 336 GCC/GCT) was found in one primary tumor. LOH of the p73 gene was detected in 5 (15%) of 33 primary NBs using PCR-LOH analysis. FISH analysis showed that all 17 NB cell lines used in this study revealed allelic loss of the p73 gene, while most of them expressed the p73 gene. These results suggest that the p73 gene is not monoallelically expressed in NB. We conclude that the p73 gene is less involved in the development but involved in the progression of neuroblastoma.

MLL-CBP fusion transcript in a therapy-related acute myeloid leukemia with the t(11;16)(q23;p13) which developed in an acute lymphoblastic leukemia patient with Fanconi anemia

We describe a boy with Fanconi anemia (FA) who developed acute lymphoblastic leukemia (ALL) (FAB-LI) followed by acute myeloid leukemia (AML) (FAB-M5) at relapse. The patient was diagnosed with early pre-B-cell ALL without preceding aplastic anemia and was treated with ALL-oriented chemotherapy which included doxorubicin (a total dose of 140 mg/m(2) administered), which is a topoisomerase II inhibitor. Complete remission was obtained, but after 38 weeks AML developed. The karyotype of ALL cells at diagnosis showed 46,XY, and that of AML cells at relapse was 46,XY, t(11;16)(q23;p13). An MLL gene rearrangement and MLL-CBP chimeric mRNA were found in AML, but not in ALL. A diagnosis of FA was confirmed by an increased number of chromosomal breaks and rearrangements in peripheral blood lymphocytes cultured with mitogen in the presence of mitomycin C. We conclude that this FA patient developed ALL followed by a therapy-related t(11;16)-AML resulting in an MLL-CBP fusion. Further examination of such patients would shed light on leukemogenesis in FA patients. Genes Chromosomes Cancer 27:264-269, 2000.

Interphase detection of t(4;14)(p16.3;q32.3) by in situ hybridization and FGFR3 overexpression in plasma cell malignancies

The immunoglobulin (Ig) genes are frequently involved in chromosomal rearrangements with a wide variety of partner loci in multiple myeloma (MM). However, several partner chromosomes have not been detected by conventional cytogenetic methods; for example, 4p16.3 (FGFR3), 6p25.3 (IRF4), and 16q23 (c-maf). To clarify the incidence of t(4;14)(p16.3;q32.3) in primary tumors of MM and to evaluate possible correlations with specific manifestations of the disease, G-banding, double-color fluorescence in situ hybridization (DC-FISH), and/or reverse-transcriptase polymerase chain reaction (RT-PCR) were performed on 40 patients with MM-two with plasmacytoma (PCM) and three with plasma cell leukemia (PCL). All patients were studied by DC-FISH; 40 were studied by G-banding and 36 were studied by RT-PCR. The FISH probes consisted of a cosmid pC385.12 containing the FGFR3 gene, a YAC Y6 containing VH, and a phage Iggamma1-10 containing the gamma1 constant region (Cgamma). We identified eight patients with either FGFR3/Cgamma fusion or FGFR3 overexpression: six patients with both FGFR3/Cgamma fusion and FGFR3 overexpression, one patient with FGFR3/Cgamma, and one with FGFR3 overexpression. FGFR3/Cgamma fusion was demonstrated at a frequency of 19% to 38% on interphase nuclei in seven of the 45 patients. Lytic bone lesions were found to be associated with FGFR3 overexpression. Interphase FISH with FGFR3 and Cgamma probes combined with RT-PCR proved to be an effective tool for detection of this fully cryptic translocation, thus facilitating the characterization of clinical features of MM patients with t(4;14).

Identification of breakpoint cluster regions at 1p36.3 and 3q21 in hematologic malignancies with t(1;3)(p36;q21)

The reciprocal translocation t(1;3)(p36;q21) is associated with myelodysplastic syndromes (MDSs) and acute myeloid leukemia (AML) characterized by trilineage dysplasia, in particular dysmegakaryocytopoiesis, and a poor prognosis. As yet no molecular genetic analyses of the t(1;3) have been reported. In four patients with t(1;3), all of whom had AML-M4, which evolved from MDS, the breakpoints at 3q21 clustered within a 60-kb region centromeric to the breakpoint of the inv(3)(q21q26), whereas the breakpoints at 1p36 clustered within a 90-kb region at 1p36.3. The presence of novel clusters in both the 3q21 and 1p36 breakpoints (BCRs) suggests a common, underlying molecular mechanism for the development of t(1;3)-positive MDS/AML. The Ribophorin I (RPN1) gene close to the BCR at 3q21 was highly expressed without gross structural changes, whereas the GR6 gene located within the BCR at 3q21 was not expressed. No other highly expressed genes were isolated in a 150-kb region at 3q21. Thus, it is likely that a gene at 1p36.3 is activated by the translocation of the 3q21 region or a gene important for transformation lies on 3q21, outside the 150-kb region. Further characterization of the BCRs at 1p36.3 and 3q21 should provide important insights into the molecular genetic mechanisms involved in the genesis of t(1;3)-positive MDS/AML. Genes Chromosomes Cancer 27:229-238, 2000.

AF5q31, a newly identified AF4-related gene, is fused to MLL in infant acute lymphoblastic leukemia with ins(5;11)(q31;q13q23)

Infant acute lymphoblastic leukemia (ALL) with MLL gene rearrangements is characterized by early pre-B phenotype (CD10(-)/CD19(+)) and poor treatment outcome. The t(4;11), creating MLL-AF4 chimeric transcripts, is the predominant 11q23 chromosome translocation in infant ALL and is associated with extremely poor prognosis as compared with other 11q23 translocations. We analyzed an infant early preB ALL with ins(5;11)(q31;q13q23) and identified the AF5q31 gene on chromosome 5q31 as a fusion partner of the MLL gene. The AF5q31 gene, which encoded a protein of 1,163 aa, was located in the vicinity of the cytokine cluster region of chromosome 5q31 and contained at least 16 exons. The AF5q31 gene was expressed in fetal heart, lung, and brain at relatively high levels and fetal liver at a low level, but the expression in these tissues decreased in adults. The AF5q31 protein was homologous to AF4-related proteins, including AF4, LAF4, and FMR2. The AF5q31 and AF4 proteins had three homologous regions, including the transactivation domain of AF4, and the breakpoint of AF5q31 was located within the region homologous to the transactivation domain of AF4. Furthermore, the clinical features of this patient with the MLL-AF5q31 fusion transcript, characterized by the early pre-B phenotype (CD10(-)/CD19(+)) and poor outcome, were similar to those of patients having MLL-AF4 chimeric transcripts. These findings suggest that AF5q31 and AF4 might define a new family particularly involved in the pathogenesis of 11q23-associated-ALL.

Expression of fibroblast growth factor and FGF-receptor family genes in human myeloma cells, including lines possessing t(4;14)(q16.3;q32. 3) and FGFR3 translocation

Recently several chromosomal translocations involved in myeloma cases and myeloma cell lines; i.e., t(11;14)(q13;q32), t('8;14)(q24;q32), t(4;14)(q16.3;q32.3), t(6;14)(p25;q32), and t(14;16)(q32.3;q23), have been identified. These translocations are considered to dysregulate genes which may be concerned with myelomagenesis; i.e., PRAD1/cyclin D1, the c-myc oncogene, FGFR3 (fibroblast growth factor receptor 3), MMSET (multiple myeloma SET domain), MUM1 (multiple myeloma oncogene 1)/IRF4 (interferon regulatory factor 4), and the c-maf oncogene, respectively. However, the cellular biological roles of these genes have not yet been elucidated in myeloma cells. Because two of the seven human myeloma cell lines which were established at Kawasaki Medical School, Okayama, Japan, KMS-11 and KMS-18, have been proven to possess t(4;14)(q16.3;q32.3), we studied the expression levels of the FGFR3 gene in these seven cell lines and 13 primary myeloma specimens. The expression levels of 12 known FGF family genes (FGF-1 to 12) and 4 FGFR genes (FGFR1 to 4) were also examined in seven cell lines. In addition, the growth status of the KMS-11 and KMS-18 lines with FGF-1 or anti-FGF-4 neutralizing monoclonal antibody (MoAb) supplementation was investigated because FGF-1 and 4 are known as the principal ligands for FGFR3. FGFR3 overexpression was observed in both of the cell lines possessing t(4;14)(q16.3;q32.3) and in 3 of 13 case specimens. Anti-FGF-4 neutralizing MoAb caused significant growth inhibition in these two cell lines possessing t(4;14)(q16.3;q32.3). These findings indicate that t(4;14) (q16. 3;q32.3) may provide myeloma cells with a growth advantage via an autocrine mechanism between FGFR3 and FGF-4.