MUM1 (multiple myeloma oncogene 1)/IRF4 (interferon regulatory factor 4) gene has been identified as an oncogene transcriptionally activated by t(6;14)(p25;q32) chromosomal translocation in multiple myeloma (MM).
Chromosome rearrangement of 14q32.33 has recurrently occurred with variable partner sites, including 11q13.3, 8q24.1, 18q21.3, and 6p21.1 in multiple myeloma (MM). To assess the actual incidence of 14q32.33 translocation and to elucidate its implication in the pathogenesis of MM, we studied 42 patients with MM, plasma cell leukemia, or plasmacytoma and 5 with monoclonal gammopathy with undetermined significance (MGUS) by G-banding and molecular cytogenetic methods. Using double-color fluorescence in situ hybridization (DCFISH) with 2 Ig heavy chain (IgH) gene probes, a yeast artificial chromosome (YAC) clone containing variable region, and a phage clone containing γ constant region, 14q32.33 translocation was detected as split signals of the IgH gene in 31 patients with plasma cell malignancies and 3 with MGUS. In contrast, of 40 patients who were assessed by G-banding, 3 (7.5%) showed the 14q+ chromosome. DCFISH detected a split of the IgH gene on interphase nuclei in 34 (73.9%) of 46 patients analyzed, whereas on metaphase spreads, it was in 22 (51.2%) of 43 patients analyzed. Interphase DCFISH was particularly useful to detect 14q32.33 translocation in 17 (65.4%) of 26 patients with normal karyotypes. Donor sites were identified in 11 of 22 patients demonstrated as carrying 14q32.33 translocation by metaphase FISH. Chromosome t(11; 14)(q13.3; q32.33) was detected in 5 patients, t(8; 14)(q24.1; q32.33) in 2, t(14; 18)(q32.33; q21.3) in 2, and t(7; 14)(q32.1; q32.33) in 1. A complex 14q32.33 translocation involving 3q and 16q24 was detected in 1 patient. Myeloma cells with t(7; 14) showed myelomonocytoid surface antigen. Because rearrangements of 14q32.33 were closely associated with translocation of proto-oncogenes into the IgH gene, our findings indicate that 14q32.33 translocation with various partner chromosomes is a critical event in the pathogenesis of MM and MGUS.
Chromosome rearrangement of 14q32.33 has recurrently occurred with variable partner sites, including 11q13.3, 8q24.1, 18q21.3, and 6p21.1 in multiple myeloma (MM). To assess the actual incidence of 14q32.33 translocation and to elucidate its implication in the pathogenesis of MM, we studied 42 patients with MM, plasma cell leukemia, or plasmacytoma and 5 with monoclonal gammopathy with undetermined significance (MGUS) by G-banding and molecular cytogenetic methods. Using double-color fluorescence in situ hybridization (DCFISH) with 2 Ig heavy chain (IgH) gene probes, a yeast artificial chromosome (YAC) clone containing variable region, and a phage clone containing γ constant region, 14q32.33 translocation was detected as split signals of the IgH gene in 31 patients with plasma cell malignancies and 3 with MGUS. In contrast, of 40 patients who were assessed by G-banding, 3 (7.5%) showed the 14q+ chromosome. DCFISH detected a split of the IgH gene on interphase nuclei in 34 (73.9%) of 46 patients analyzed, whereas on metaphase spreads, it was in 22 (51.2%) of 43 patients analyzed. Interphase DCFISH was particularly useful to detect 14q32.33 translocation in 17 (65.4%) of 26 patients with normal karyotypes. Donor sites were identified in 11 of 22 patients demonstrated as carrying 14q32.33 translocation by metaphase FISH. Chromosome t(11; 14)(q13.3; q32.33) was detected in 5 patients, t(8; 14)(q24.1; q32.33) in 2, t(14; 18)(q32.33; q21.3) in 2, and t(7; 14)(q32.1; q32.33) in 1. A complex 14q32.33 translocation involving 3q and 16q24 was detected in 1 patient. Myeloma cells with t(7; 14) showed myelomonocytoid surface antigen. Because rearrangements of 14q32.33 were closely associated with translocation of proto-oncogenes into the IgH gene, our findings indicate that 14q32.33 translocation with various partner chromosomes is a critical event in the pathogenesis of MM and MGUS.
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 (Sc3) at 14q32 and the first intron of the human retinoic acid-inducible E3 protein (E3)/lysosomeassociated 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.
Human myeloma cell lines are useful as an in vitro model for the genetic and cellular biological characterization of primary myeloma cells. We have been attempting to establish myeloma lines since 1979 for the study of the cytogenetic, molecular and cellular biological aspects of myeloma cells and to resolve the clinical problems associated with multiple myeloma. The establishment and characterization of some of these lines have been reported. Here we review the lines established at Kawasaki Medical School and discuss investigations related to the clinical manifestation of myeloma using these lines. For instance, the relation between myeloma specific chromosomal translocations, such as t(11;14)(q13;q32), t(8;14)(q24;q32), and t(4;14)(q16.3;q32.3), found in some of the cell lines and gene expression was examined.
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