Hiroko Nagamura

RNA from decades-old archival tissue blocks for retrospective studies.

The validity of molecular studies using DNA and RNA extracted from decades-old formalin-fixed and paraffinembedded tissue blocks has been demonstrated. The quality and usability of DNA and RNA from archival tissues are modified by various factors, such as the fixative, the fixation time, and the postmortem time. However, in contrast to DNA, there are no comprehensive studies quantitatively addressing the feasibility of RNA from old (more than 10 years) archival samples. This study examined the integrity of RNA extracted from 738 autopsy liver and 63 autopsy thyroid cancer tissue blocks procured during a span of nearly four decades, beginning in 1952 and ending in 1989, from the atomic bomb survivors. The integrity of RNA was assessed by amplification of c-BCR messenger RNA (mRNA) between two sequential exons with an intervening intron by reverse-transcription polymerase chain reaction (RT-PCR). The integrity of RNA was influenced by the age of the samples and the postmortem time, but not by the formalin-fixation period. It was possible to amplify more than 60% of the samples. Using these RNAs, the HCV genome in liver cancers and the H4-RET gene in thyroid cancers were detectable. This study illustrates the possibility of molecular studies using RNA from routinely prepared paraffin blocks stored for long periods and provides the statistics and critical factors to consider in assessing the feasibility of such contemplated studies.

Preferential induction of RET/PTC1 rearrangement by X-ray irradiation.

Ionizing radiation is a well known risk factor of thyroid cancer development, but the mechanism of radiation induced carcinogenesis is not clear. The RETPTC oncogene, an activated form of the RET proto-oncogene, is frequently observed in papillary thyroid carcinoma (PTC); RETPTC1, -2 and -3 are known to be the three major forms. High frequencies of RETPTC rearrangements have been observed in radiation-associated PTC, such as those appearing post-Chernobyl or post-radiotherapy, but the rearrangement types differ between these two populations. We investigated whether a specific type of RETPTC rearrangement was induced by X-rays in vivo and in vitro. In human normal thyroid tissues transplanted in scid mice, the RETPTC1 rearrangement was predominantly detected throughout the observation period (up to 60 days) after X-ray exposure of 50 Gy. On the other hand, RETPTC3 was detected only 7 days after X-irradiation, and no transcript of RETPTC2 was detected. These results are supported by the results of an in vitro study. The RETPTC1 rearrangement was preferentially induced in a dose-dependent manner by X-rays within a high dose range (10, 50 and 100 Gy) in four cell lines. On the other hand, RETPTC3 was induced at a much lower frequency, and no induction of RETPTC2 was observed. These results suggest that the preferential induction of the RETPTC1 rearrangement may play an important role in the early steps of thyroid carcinogenesis induced by acute X-irradiation.

Effects of IL-10 Haplotype and Atomic Bomb Radiation Exposure on Gastric Cancer Risk

Gastric cancer (GC) is one of the cancers that reveal increased risk of mortality and incidence in atomic bomb survivors. The incidence of gastric cancer in the Life Span Study cohort of the Radiation Effects Research Foundation (RERF) increased with radiation dose (gender-averaged excess relative risk per Gy = 0.28) and remains high more than 65 years after exposure. To assess a possible role of gene-environment interaction, we examined the dose response for gastric cancer incidence based on immunosuppression-related IL-10 genotype, in a cohort study with 200 cancer cases (93 intestinal, 96 diffuse and 11 other types) among 4,690 atomic bomb survivors participating in an immunological substudy. Using a single haplotype block composed of four haplotype-tagging SNPs (comprising the major haplotype allele IL-10-ATTA and the minor haplotype allele IL-10-GGCG, which are categorized by IL-10 polymorphisms at −819A>G and −592T>G, +1177T>C and +1589A>G), multiplicative and additive models for joint effects of radiation and this IL-10 haplotyping were examined. The IL-10 minor haplotype allele(s) was a risk factor for intestinal type gastric cancer but not for diffuse type gastric cancer. Radiation was not associated with intestinal type gastric cancer. In diffuse type gastric cancer, the haplotype-specific excess relative risk (ERR) for radiation was statistically significant only in the major homozygote category of IL-10 (ERR = 0.46/Gy, P = 0.037), whereas estimated ERR for radiation with the minor IL-10 homozygotes was close to 0 and nonsignificant. Thus, the minor IL-10 haplotype might act to reduce the radiation related risk of diffuse-type gastric cancer. The results suggest that this IL-10 haplotyping might be involved in development of radiation-associated gastric cancer of the diffuse type, and that IL-10 haplotypes may explain individual differences in the radiation-related risk of gastric cancer.

Long term effects of radiation exposure on telomere lengths of leukocytes and its associated biomarkers among atomic-bomb survivors

Ionizing radiation (IR) is a major source of cellular damage and the immediate cellular response to IR has been well characterized. But the long-term impact of IR on cell function and its relationship with aging are not known. Here, we examined the IR effects on telomere length and other biomarkers 50 to 68 years post-exposure (two time points per person) in survivors of the atomic bombing at Hiroshima during WWII. We found that telomere length of leukocytes was inversely correlated with the dose of IR (p=0.008), and this effect was primarily found in survivors who were exposed at younger ages; specifically those <12 years old (p=0.0004). Although a dose-related retardation of telomere shortening with age was observed in the cross-sectional data, longitudinal follow-up after 11 years did not show IR exposure-related alteration of the rate of telomere shortening with age. In addition, IR diminished the associations between telomere length and selected aging biomarkers that were observed in survivors with no dose. These included uric acid metabolism, cytokines, and blood T cell counts. These findings showed long-lasting detrimental effects of IR on telomere length of leukocytes in both dose- and age-at-exposure dependent manner, and on alterations of biomarkers with aging.

Caspase-independent cell death without generation of reactive oxygen species in irradiated MOLT-4 human leukemia cells

To improve our understanding of ionizing radiation effects on immune cells, we investigated steps leading to radiation-induced cell death in MOLT-4, a thymus-derived human leukemia cell. After exposure of MOLT-4 cells to 4 Gy of X-rays, irradiated cells sequentially showed increase in intracellular reactive oxygen species (ROS), decrease in mitochondrial membrane potential, and eventually apoptotic cell death. In the presence of the caspase inhibitor z-VAD-fmk, irradiated cells exhibited necrotic characteristics such as mitochondrial swelling instead of apoptosis. ROS generation was not detected during this necrotic cell death process. These results indicate that radiation-induced apoptosis in MOLT-4 cells requires elevation of intracellular ROS as well as activation of a series of caspases, whereas the cryptic necrosis program--which is independent of intracellular ROS generation and caspase activation--is activated when the apoptosis pathway is blocked.

Impact of early life exposure to ionizing radiation on influenza vaccine response in an elderly Japanese cohort

The objective of this study was to evaluate effects of whole body radiation exposure early in life on influenza vaccination immune responses much later in life. A total of 292 volunteers recruited from the cohort members of ongoing Adult Health Study (AHS) of Japanese atomic bomb (A-bomb) survivors completed this observational study spanning two influenza seasons (2011-2012 and 2012-2013). Peripheral blood samples were collected prior to and three weeks after vaccination. Serum hemagglutination inhibition (HAI) antibody titers were measured as well as concentrations of 25 cytokines and chemokines in culture supernatant from peripheral blood mononuclear cells, with and without in vitro stimulation with influenza vaccine. We found that influenza vaccination modestly enhanced serum HAI titers in this unique cohort of elderly subjects, with seroprotection ranging from 18 to 48% for specific antigen/season combinations. Twelve percent of subjects were seroprotected against all three vaccine antigens post-vaccination. Males were generally more likely to be seroprotected for one or more antigens post-vaccination, with no differences in vaccine responses based on age at vaccination or radiation exposure in early life. These results show that early life exposure to ionizing radiation does not prevent responses of elderly A-bomb survivors to seasonal influenza vaccine.

Abstract 4715: Genetic susceptibility to radiation-associated colon and rectum cancers among atomic-bomb survivors with special reference to the CD14 gene

Past epidemiology studies reported that atomic-bomb (A-bomb) radiation exposure enhanced risk of colon cancer, but not rectum cancer, among the survivors. The reason for this different sensitivity to radiation remains to be elucidated. Colorectal cancer is a multi-factorial disease, the onset of which is attributed to both environmental and genetic factors, with animal experiments showing that intestinal bacterial toxins accelerate carcinogenesis. It was recently reported that single nucleotide polymorphisms (SNPs) identified in the promoter region of CD14, encoding a receptor for the lipopolysaccharide component of the outer membrane of Gram-negative bacteria, regulate CD14 gene expression and thereby affect susceptibility to inflammatory diseases such as atopic dermatitis, coronary artery disease, and hepatic diseases. This study investigated relationship between a novel CD14 gene polymorphism and the development of radiation-associated colon and rectum cancers among an A-bomb survivor cohort, in terms of a case-cohort study. On the basis of this T/G polymorphism, we determined CD14 genotypes with 210 colorectal cancer cases and with a subcohort of 2,160 individuals who were randomly selected from the cohort. Our results showed that the individuals exposed to A-bomb radiation (≥5 mGy) were at an increased risk of colon cancer, but not rectum cancer, with relative risk (RR) of 1.19/Gy (95%CI: 1.04-1.36). When we divided the study subjects into three groups for radiation dose and into two groups for CD14 genotypes, significantly high risk of colon cancer was found with RR of 2.40 (95%CI: 1.37-4.23) for the combined category of CD14-T/T homozygote and the highest dose (≥0.7Gy), compared with the baseline category (CD14-T/G or G/G and no dose). These results suggest that CD14-related inflammatory response might be involved in the development of radiation-associated colon cancer, not rectum cancer, among A-bomb survivors, and that the CD14 genotyping might be involved in individual risk of colon cancer together with radiation dose. To find a functional significance of this polymorphism, we are currently working on ELISA-based assay to measure serum levels of soluble CD14 among healthy individuals in relation to the CD14 genotyping. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4715.