Inactivation of the E3/LAPTm5 gene by chromosomal rearrangement and DNA methylation in human multiple myeloma.

Chromosomal band 1p34-36 is a commonly rearranged locus in many types of cancers. We cloned the breakpoint region of a chromosomal translocation, t(1;14)(p34;q32), found in the human multiple myeloma (MM) cell line, ODA. This rearrangement occurred between the nearby switch region of the immunoglobulin heavy chain (IgH) gene (Sgamma3) at 14q32 and the first intron of the human retinoic acid-inducible E3 protein (E3)/lysosome-associated protein, transmembrane-5 (LAPTm5) gene at the 1p34 locus. Consequently, the E3 gene, which is a hematopoietic cell-specific transcript induced by retinoic acid and located at the rearranged allele, was interrupted within its coding region and was not expressed in the ODA cell line in spite of the other allele still being intact. The expression derived from the remaining intact allele in ODA cells was silenced by DNA methylation at sequences within the first intron around a GC-rich EagI site. Interestingly, the silenced expression of E3 mRNA due to DNA methylation of intron 1 sequences was frequently encountered in MM cells [6/10 (60%) of MM cell lines tested], while E3 is expressed in normal plasma cells and in most other hematopoietic cell lines including those of B-cell lineage. Thus, as the E3 protein has been suggested to be involved in cellular differentiation and apoptotic pathways in certain cell types, our results suggest that loss of E3 gene expression might be a crucial event during the progression of human MM.

Possible dominant-negative mutation of the SHIP gene in acute myeloid leukemia.

The SH2 domain-containing inositol 5'-phosphatase (SHIP) is crucial in hematopoietic development. To evaluate the possible tumor suppressor role of the SHIP gene in myeloid leukemogenesis, we examined primary leukemia cells from 30 acute myeloid leukemia (AML) patients, together with eight myeloid leukemia cell lines. A somatic mutation at codon 684, replacing Val with Glu, was detected in one patient, lying within the signature motif 2, which is the phosphatase active site. The results of an in vitro inositol 5'-phosphatase assay revealed that the mutation reduced catalytic activity of SHIP. Leukemia cells with the mutation showed enhanced Akt phosphorylation following IL-3 stimulation. K562 cells transfected with the mutated SHIP-V684E cDNA showed a growth advantage even at lower serum concentrations and resistance to apoptosis induced by serum deprivation and exposure to etoposide. These results suggest a possible role of the mutated SHIP gene in the development of acute leukemia and chemotherapy resistance through the deregulation of the phosphatidylinositol-3,4,5-triphosphate (PI(3,4,5)P3)/Akt signaling pathway. This is the first report of a mutation in the SHIP gene in any given human cancer, and indicates the need for more attention to be paid to this gene with respect to cancer pathogenesis.

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).

Improvement of splenomegaly and pancytopenia by enzyme replacement therapy against type 1 Gaucher disease: a report of sibling cases.

Gaucher disease is a genetic lipid storage disease and represents a potentially serious health problem. It arises from a deficiency of glucocerebrosidase activity with secondary accumulation of large quantities of glucocerebroside. Symptoms are usually multisystemic, often debilitating or disabling, and sometimes disfiguring, and they can lead to death. We report objective clinical response's to repeated infusion of human placental and recombinant glucocerebrosidase in 2 patients with type 1 Gaucher disease and increased hemoglobin levels and platelet counts. Splenic volume decreased during the period of enzyme administration. Enzyme replacement therapy has improved the treatment of type 1 Gaucher disease by safely and effectively arresting, decreasing, or normalizing many of its major signs and symptoms. Consideration by physicians must be given to Gaucher disease, and appropriate treatments must be given when confronted with cryptogenic pancytopenia or hepatosplenomegaly.

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.

MUM1/IRF4 expression as a frequent event in mature lymphoid malignancies.

MUM1/IRF4 is a myeloma-associated oncogene transcriptionally activated as a result of t(6;14)(p25,q32) chromosomal translocation and by virtue of its juxtaposition to the immunoglobulin heavy chain gene (IgH) locus. When this oncogene becomes non-functional, no activated B/T lymphocytes and Ig secreting plasma cells are observed, suggesting that MUM1/IRF4 is crucial for lymphoid development. Its expression was analyzed in both reactive lymphoid and lymphoma tissues by means of an immunohistochemical technique using specific goat antiserum against MUM1/IRF4. This analysis detected a 50 kDa MUM1 product whose localization was restricted to the nuclei of the lymphocytes. The MUM1+ cells in reactive lymph nodes were found to consist of plasma cells and a small fraction (approximately 7.9%) of B cells harboring CD20+CD38+, which were located in the light zone of the germinal center. MUM1 expression in peripheral blood B/T lymphocytes was upregulated by mitogenic stimuli, suggesting that MUM1 positivity represents the activated state of the B/T cells. In B cell non-Hodgkin's lymphoma (NHL), MUM1 expression was observed in 73.2% (30/41) of diffuse large B cell lymphoma (DLBCL), 20% (1/5) of marginal zone lymphoma (MZL) and 43% (3/7) of small lymphocytic lymphoma (SLL) cases, whereas it was not seen in any cases of mantle cell lymphoma (MCL) or follicle center lymphoma (FCL). Also, MUM1 was stained at high intensity in various types of T cell lymphomas including adult T cell leukemia/lymphoma (ATL/L) and anaplastic large cell lymphoma (ALCL) and in the majority of Hodgkin's diseases. Our results suggest that a major proportion of lymphomas comprise either physiologically or aberrantly activated neoplastic lymphocytes expressing the MUM1 protein.

Idiopathic CD4+ T-lymphocytopenia in a non-Hodgkin's lymphoma patient.

We report a case of idiopathic CD4+ T-lymphocytopenia with malignant lymphoma (diffuse large, B-cell type) for which there was no evidence of human immunodeficiency virus type 1 or type 2 infection and no other known causes of immunodeficiency. She had never suffered from any opportunistic infection until the diagnosis of malignant lymphoma was made, and the CD4+ T-lymphocytopenia persisted after complete remission of the lymphoma. As the clinical features and immune status of the patient differed from those associated with the acquired immunodeficiency syndrome (AIDS)-related syndrome, we conclude that immunodeficiency in this case did not contribute to the opportunistic infection but may have been associated with the genesis of malignant lymphoma.