Nanao Kamada

Cancer Incidence in Atomic Bomb Survivors. Part III: Leukemia, Lymphoma and Multiple Myeloma, 1950-1987

This paper presents an analysis of data on the incidence of leukemia, lymphoma and myeloma in the Life Span Study cohort of atomic bomb survivors during the period from late 1950 through the end of 1987 (93,696 survivors accounting for 2,778,000 person-years). These analyses add 9 additional years of follow-up for leukemia and 12 for myeloma to that in the last comprehensive reports on these diseases. This is the first analysis of the lymphoma incidence data in the cohort. Using both the Leukemia Registry and the Hiroshima and Nagasaki tumor registries, a total of 290 leukemia, 229 lymphoma and 73 myeloma cases were identified. The primary analyses were restricted to first primary tumors diagnosed among residents of the cities or surrounding areas with Dosimetry System 1986 dose estimates between 0 and 4 Gy kerma (231 leukemias, 208 lymphomas and 62 myelomas). Analyses focused on time-dependent models for the excess absolute risk. Separate analyses were carried out for acute lymphocytic leukemia (ALL), acute myelogenous leukemia (AML), chronic myelocytic leukemia (CML) and adult T-cell leukemia (ATL). There were few cases of chronic lymphocytic leukemia in this population. There was strong evidence of radiation-induced risks for all subtypes except ATL, and there were significant subtype differences with respect to the effects of age at exposure and sex and in the temporal pattern of risk. The AML dose-response function was nonlinear, whereas there was no evidence against linearity for the other subtypes. When averaged over the follow-up period, the excess absolute risk (EAR) estimates (in cases per 10(4) PY Sv) for the leukemia subtypes were 0.6, 1.1 and 0.9 for ALL, AML and CML, respectively. The corresponding estimated average excess relative risks at 1 Sv are 9.1, 3.3 and 6.2 respectively. There was some evidence of an increased risk of lymphoma in males (EAR = 0.6 cases per 10(4) PY Sv) but no evidence of any excess in females. There was no evidence of an excess risk for multiple myeloma in our standard analyses.

The Incidence of Leukemia, Lymphoma and Multiple Myeloma among Atomic Bomb Survivors: 1950–2001

A marked increase in leukemia risks was the first and most striking late effect of radiation exposure seen among the Hiroshima and Nagasaki atomic bomb survivors. This article presents analyses of radiation effects on leukemia, lymphoma and multiple myeloma incidence in the Life Span Study cohort of atomic bomb survivors updated 14 years since the last comprehensive report on these malignancies. These analyses make use of tumor- and leukemia-registry based incidence data on 113,011 cohort members with 3.6 million person-years of follow-up from late 1950 through the end of 2001. In addition to a detailed analysis of the excess risk for all leukemias other than chronic lymphocytic leukemia or adult T-cell leukemia (neither of which appear to be radiation-related), we present results for the major hematopoietic malignancy types: acute lymphoblastic leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, chronic myeloid leukemia, adult T-cell leukemia, Hodgkin and non-Hodgkin lymphoma and multiple myeloma. Poisson regression methods were used to characterize the shape of the radiation dose-response relationship and, to the extent the data allowed, to investigate variation in the excess risks with gender, attained age, exposure age and time since exposure. In contrast to the previous report that focused on describing excess absolute rates, we considered both excess absolute rate (EAR) and excess relative risk (ERR) models and found that ERR models can often provide equivalent and sometimes more parsimonious descriptions of the excess risk than EAR models. The leukemia results indicated that there was a nonlinear dose response for leukemias other than chronic lymphocytic leukemia or adult T-cell leukemia, which varied markedly with time and age at exposure, with much of the evidence for this nonlinearity arising from the acute myeloid leukemia risks. Although the leukemia excess risks generally declined with attained age or time since exposure, there was evidence that the radiation-associated excess leukemia risks, especially for acute myeloid leukemia, had persisted throughout the follow-up period out to 55 years after the bombings. As in earlier analyses, there was a weak suggestion of a radiation dose response for non-Hodgkin lymphoma among men, with no indication of such an effect among women. There was no evidence of radiation-associated excess risks for either Hodgkin lymphoma or multiple myeloma.

Mutations of a novel human RAD54 homologue, RAD54B , in primary cancer

Association of breast tumor susceptibility gene products BRCA1 and BRCA2 with the RAD51 recombination protein suggested that cancer could arise through defects in recombination. The identification of NBS1, responsible for Nijmegen breakage syndrome, from the MRE11/RAD50 recombination protein complex also supports this hypothesis. However, our mutation analysis revealed that known members of the RAD52 epistasis group are rarely mutated in human primary cancer. Here we describe the isolation of a novel member of the SNF2 superfamily, characterized with sequence motifs similar to those in DNA and RNA helicases. The gene, designated RAD54B, is significantly homologous to the RAD54 recombination gene. The expression of RAD54B was high in testis and spleen, which are active in meiotic and mitotic recombination. These findings suggest that RAD54B may play an active role in recombination processes in concert with other members of the RAD52 epistasis group. RAD54B maps to human chromosome 8q21.3-q22 in a region associated with cancer-related chromosomal abnormalities. Homozygous mutations at highly conserved positions of RAD54B were observed in human primary lymphoma and colon cancer. These findings suggest that some cancers arise through alterations of the RAD54B function.

Mutations in the RAD54 recombination gene in primary cancers

Association of a recombinational repair protein RAD51 with tumor suppressors BRCA1 and BRCA2 suggests that defects in homologous recombination are responsible for tumor formation. Also recent findings that a protein associated with the MRE11/RAD50 repair complex is mutated in Nijmegen breakage syndrome characterized by increased cancer incidence and ionizing radiation sensitivity strongly support this idea. However, the direct roles of BRCA proteins and the protein responsible for NBS in recombinational repair are not clear though they are associated with the recombinational repair complexes. Since RAD51 forms a complex with other members of the RAD52 epistasis group and with BRCA proteins, it is reasonable to ask if alterations of members of the RAD52 epistasis group lead to tumor development. Here we describe missense mutations at functional regions of RAD54 and the absence of the wild-type RAD54 expression resulting from aberrant splicing in primary cancers. Since RAD54 is a recombinational protein associated with RAD51, this is the first genetic evidence that cancer arises from a defect in repair processes involving homologous recombination.

A summary of cytogenetic studies on 534 cases of chronic myelocytic leukemia in Japan

Cytogenetic and clinical data on 534 patients with chronic myelocytic leukemia (CML) were collected from 10 institutions in Japan. The results of the analysis of the data were in substantial accord with those of the First International Workshop on Chromosomes in Leukemia and other published data, but certain differences were noted in the frequency of Philadelphia chromosome (Ph1)-negative cases, unusual and complex Ph1 translocations, and additional chromosome changes. Some of the findings are discussed with respect to the origin of unusual and complex Ph1 translocations, the relationship between chromosome abnormalities and survival, and geographic differences in chromosome abnormalities.

Multiple possible sites of BRAC2 interacting with DNA repair protein RAD51

To investigate the biological consequences of aberrant BRCA2 protein during mammary carcinogenesis, we attempted to identify proteins that normally interact with BRCA2. By using a yeast two‐hybrid system with a hybrid protein that contained residues 639–1,508 of BRCA2 protein fused to the GAL4 DNA‐binding domain, we isolated five independent cDNA clones that encoded parts of RAD51 protein, a human homolog of bacterial RecA. In vitro experiments using anti‐RAD51 antibody confirmed interaction of BRCA2 with RAD51. The RAD51‐binding region of BRCA2 detected in the present study was distinct from the region reported recently. Further studies using smaller portions of BRCA2 defined at least two additional RAD51‐binding domains, residues 982–1,066 and 1,139–1,266. Our results suggest that BRCA2 can interact with RAD51 through multiple sites of BRCA2 and that control of mitotic and meiotic recombination and/or of genomic integrity through binding to RAD51 may be a crucial mechanism by which BRCA2 suppresses abnormal proliferation of mammary cells. Genes Chromosomes Cancer 21:217–222, 1998.

Evidence for RAD51L1/HMGIC fusion in the pathogenesis of uterine leiomyoma.

Chromosome rearrangements involving 12q15 are frequently observed in a variety of human mesenchymal tumors. The high mobility group protein gene HMGIC has been identified as the target involved in these rearrangements. Uterine leiomyomas frequently use chromosome band 14q24 as a translocation partner to HMGIC. Recent studies within the chromosome 14 breakpoint region in cell lines carrying t(12;14)(q15;q23–24) revealed that RAD51L1, a member of the RAD51 recombination gene family, is the HMGIC partner. Using RT‐PCR, we screened a panel of 81 uterine leiomyomas removed from 30 women for rearrangement between RAD51L1 and HMGIC. This is the first molecular analysis in which primary tumors have been examined for the RAD51L1/HMGIC transcripts. The chimeric transcripts were identified from two cases in which exon 7 of the RAD51L1 gene is fused in frame to either exon 2 or exon 3 of the HMGIC gene. These transcripts encode fusion proteins containing RAD51L1 nucleotide binding domains and the HMGIC protein lacking the N‐terminal AT hook motifs. The detection of the RAD51L1/HMGIC fusion in primary tumors adds to the accumulating evidence implicating this fusion in a proportion of uterine leiomyoma patients.

Risk-directed treatment of infant acute lymphoblastic leukaemia based on early assessment of MLL gene status: results of the Japan Infant Leukaemia Study (MLL96).

Summary.  We studied the effectiveness of risk‐directed therapy for infants younger than 13 months of age with acute lymphoblastic leukaemia (ALL). Fifty‐five infants were assigned to different treatment programs (from December 1995 to December 1998) on the basis of their MLL gene status at diagnosis. Forty‐two cases (76·3%) had a rearranged MLL gene (MLL+) and were treated with remission induction therapy followed by sequential intensive chemotherapy, including multiple genotoxic agents (MLL9601 protocol). Haematopoietic stem cell transplantation (HSCT) was attempted if suitable donors were available. Thirteen infants (23·7%) were classified as MLL– and treated for 2·5 years with intensive chemotherapy for high‐risk B‐ALL (MLL9602 protocol). Complete remission was induced in 38 of the 42 infants (90·5%) with MLL+ ALL and in all 13 patients (100%) with MLL– disease. In the MLL+ subgroup, the estimated event‐free survival (EFS) rate at 3 years post diagnosis was 34·0% ± 7·5%, compared with 92·3% ± 7·4% in the MLL– subgroup (overall comparison, P = 0·001 by log‐rank analysis). Both age less than 6 months (hazard ratio = 6·87, 95% CI = 0·91–52·3; P = 0·013) and central nervous system (CNS) involvement at diagnosis (hazard ratio = 2·92 95% CI = 1·29–6·63; P = 0·015) were significant independent predictors of an inferior outcome. These findings indicate a strategic advantage in classifying infant ALL as either MLL+ or MLL– early in the clinical course and selecting therapy accordingly. Standard chemotherapy for high‐risk B‐lineage ALL appeared adequate for MLL– cases. Novel therapeutic initiatives are warranted for infants with MLL+ disease, particularly those with initial CNS leukaemic involvement or age less than 6 months, or both.

Malignant fibrous histiocytoma. A tumor of facultative histiocytes showing mesenchymal differentiation in cultured cell lines.

The histogenesis of malignant fibrous histiocytoma (MFH) is controversial. To elucidate the cellular origin and characteristics of this neoplasm, the authors analyzed cell lines grown from 17 patients (15 soft tissue MFH and 2 bone MFH) by using light and electron microscopy, immunocytochemistry, enzyme cytochemistry, and functional tests for receptors for the Fc portion of immunoglobulin (Fc receptors) and immunophagocytosis. Each culture exhibited a storiform/pleomorphic pattern with mixed cellular populations consisting of spindle cells, polygonal cells, and bizarre giant cells; these morphologic features corresponded to the histologio characteristics of the primary tumors. The cells in each MFH line displayed histiocytic functional markers such as lysosomal enzymes, Fc receptors, and immunophagocytosis. However, these cells differed from monocyte‐derived macrophages (histiocytes) in immunoreactivity; the MFH cells expressed a mesenchymal antigen (FU3) distributed among perivascular cells and fibroblasts but demonstrated no positive reactions with Leu‐M1 (CD15) and Leu‐M3 (CD14), which recognize the cells of the monocyte‐macrophage lineage. In conclusion, these findings suggest that MFH is not a tumor of true histiocytes but of facultative histiocytes showing mesenchymal differentiation in vitro. Chromosomal analysis performed in one MFH line demonstrated abnormal karyotypes; the modal chromosome number was 58, with 5 marker chromosomes.

Heterogeneous fusion transcripts involving the NUP98 gene and HOXD13 gene activation in a case of acute myeloid leukemia with the t(2;11)(q31;p15) translocation

We report the characterization of a rare chromosomal translocation, a t(2;11)(q31;p15), which occurred in a patient with de novo acute myeloid leukemia (AML-M4). By 3′-RACE and RT-PCR analyses, two kinds of NUP98-HOXD13 fusion transcript were detected. In addition, we identified a novel fusion transcript, NUP98-FN1, in the same patient. Ectopic expression of the wild-type HOXD13 gene was also observed in the patient, suggesting that HOXD13 contributes to the development of this type of leukemia. The NUP98-HOXD13 fusion transcript was predicted to encode a 552 or 569-amino acid protein containing the Phe-Gly (FG) repeat region of NUP98 and the homeodomain of HOXD13. The NUP98-FN1 fusion transcript was predicted to encode a 482 or 499-amino acid protein consisting of the same N-terminal region of NUP98 and a C-terminal region of 12 amino acids derived from a previously unidentified sequence. We isolated and characterized the chromosomal breakpoints. The breakpoint at 11p15 is mapped within a LINE repetitive element in a 9 kb intron of NUP98, and more than 60% of the sequenced 3 kb region surrounding the breakpoint junction consists of repetitive elements. The other breakpoint at 2q31 is in an intron of FN1, which is located 7 kb upstream of HOXD13, and the repetitive sequence content of the breakpoint junction is low. Local sequence duplications at genomic breakpoints suggest that the t(2;11) translocation is mediated through staggered double-strand DNA breaks. These results throw light on the mechanisms responsible for the generation of t(2;11) translocation and on the processes leading to t(2;11) leukemia. Leukemia (2000) 14, 1621–1629.