Tomonori Hayashi

Serum interleukin-6 associated with hepatocellular carcinoma risk: A nested case-control study

Inflammatory markers have been associated with increased risk of several cancers, including colon, lung, breast and liver, but the evidence is inconsistent. We conducted a nested case–control study in the longitudinal cohort of atomic‐bomb survivors. The study included 224 hepatocellular carcinoma (HCC) cases and 644 controls individually matched to cases on gender, age, city and time and method of serum storage, and countermatched on radiation dose. We measured C‐reactive protein (CRP) and interleukin (IL)‐6 using stored sera obtained within 6 years before HCC diagnosis from 188 HCC cases and 605 controls with adequate volumes of donated blood. Analyses with adjustment for hepatitis virus infection, alcohol consumption, smoking habit, body mass index (BMI) and radiation dose showed that relative risk (RR) of HCC [95% confidence interval (CI)] in the highest tertile of CRP levels was 1.94 (0.72–5.51) compared to the lowest tertile (p = 0.20). RR of HCC (95% CI) in the highest tertile of IL‐6 levels was 5.12 (1.54–20.1) compared to the lowest tertile (p = 0.007). Among subjects with BMI > 25.0 kg/m2, a stronger association was found between a 1‐standard deviation (SD) increase in log IL‐6 and HCC risk compared to subjects in the middle quintile of BMI (21.3–22.9 kg/m2), resulting in adjusted RR (95% CI) of 3.09 (1.78–5.81; p = 0.015). The results indicate that higher serum levels of IL‐6 are associated with increased HCC risk, independently of hepatitis virus infection, lifestyle‐related factors and radiation exposure. The association is especially pronounced among subjects with obesity.

T-Cell Immunosenescence and Inflammatory Response in Atomic Bomb Survivors

Abstract In this paper we summarize the long-term effects of A-bomb radiation on the T-cell system and discuss the possible involvement of attenuated T-cell immunity in the disease development observed in A-bomb survivors. Our previous observations on such effects include impaired mitogen-dependent proliferation and IL-2 production, decreases in naive T-cell populations, and increased proportions of anergic and functionally weak memory CD4 T-cell subsets. In addition, we recently found a radiation dose-dependent increase in the percentages of CD25+/CD127− regulatory T cells in the CD4 T-cell population of the survivors. All these effects of radiation on T-cell immunity resemble effects of aging on the immune system, suggesting that ionizing radiation might direct the T-cell system toward a compromised phenotype and thereby might contribute to an enhanced immunosenescence. Furthermore, there are inverse, significant associations between plasma levels of inflammatory cytokines and the relative number of naïve CD4 T cells, also suggesting that the elevated levels of inflammatory markers found in A-bomb survivors can be ascribed in part to T-cell immunosenescence. We suggest that radiation-induced T-cell immunosenescence may result in activation of inflammatory responses and may be partly involved in the development of aging-associated and inflammation-related diseases frequently observed in A-bomb survivors.

Evaluation of systemic markers of inflammation in atomic-bomb survivors with special reference to radiation and age effects

Past exposure to atomic bomb (A‐bomb) radiation has exerted various long‐lasting deleterious effects on the health of survivors. Some of these effects are seen even after > 60 yr. In this study, we evaluated the subclinical inflammatory status of 442 A‐bomb survivors, in terms of 8 inflammation‐related cytokines or markers, comprised of plasma levels of reactive oxygen species (ROS), interleukin (IL)‐6, tumor necrosis factor α (TNF‐α), C‐reactive protein (CRP), IL‐4, IL‐10, and immunoglobulins, and erythrocyte sedimentation rate (ESR). The effects of past radiation exposure and natural aging on these markers were individually assessed and compared. Next, to assess the biologically significant relationship between inflammation and radiation exposure or aging, which was masked by the interrelationship of those cytokines/markers, we used multivariate statistical analyses and evaluated the systemic markers of inflammation as scores being calculated by linear combinations of selected cytokines and markers. Our results indicate that a linear combination of ROS, IL‐6, CRP, and ESR generated a score that was the most indicative of inflammation and revealed clear dependences on radiation dose and aging that were found to be statistically significant. The results suggest that collectively, radiation exposure, in conjunction with natural aging, may enhance the persistent inflammatory status of A‐bomb survivors.—Hayashi, T., Morishita, Y., Khattree, R., Misumi, M., Sasaki, K., Hayashi, I., Yoshida, K., Kajimura, J., Kyoizumi, S., Imai, K., Kusunoki, Y., Nakachi, K. Evaluation of systemic markers of inflammation in atomic‐bomb survivors with special reference to radiation and age effects. FASEB J. 26, 4765–4773 (2012). www.fasebj.org

Conventional case–cohort design and analysis for studies of interaction

BACKGROUNDnThe case-cohort study design has received significant methodological attention in the statistical and epidemiological literature but has not been used as widely as other cohort-based sampling designs, such as the nested case-control design. Despite its efficiency and practicality for a wide range of epidemiological study purposes, researchers may not yet be aware of the fact that the design can be analysed using standard software with only minor adjustments. Furthermore, although the large number of options for design and analysis of case-cohort studies may be daunting, they can be reduced to a few simple recommendations.nnnMETHODSnWe review conventional methods for the design and analysis of case-cohort studies and describe empirical comparisons based on a study of radiation, gene polymorphisms and cancer in the Japanese atomic bomb survivor cohort.nnnRESULTSnStratified, as opposed to simple, random subcohort selection is recommended, especially for studies of gene-environment interaction, which are notorious for lacking statistical power. Methods based on the score-unbiased exact pseudo-likelihood (or its analogue with stratified case-cohort data) are recommended for use in conjunction with the asymptotic variance estimator.nnnCONCLUSIONSnWe present an example of how to implement case-cohort analysis methods using SPSS, a popular statistical package that lacks some of the features necessary to directly adapt and implement published methods based on other software platforms. We also illustrate case-control analysis using Epicure, which provides greater risk-modelling flexibility than other software. Our conclusions and recommendations should help investigators to better understand and apply the case-cohort design in epidemiological research.

Age-Associated Changes in the Differentiation Potentials of Human Circulating Hematopoietic Progenitors to T- or NK-Lineage Cells

Age-associated changes of T and NK cell (T/NK) potential of human hematopoietic stem cells are unknown. In this study, we enumerate and characterize T/NK precursors among CD34+Lin− cell populations circulating in normal human adult peripheral blood (PB) by a limiting-dilution assay using coculture with OP9-DL1 stroma cells expressing Notch 1 ligand, Delta–like 1. The frequency of T cell precursors in CD34+Lin− cells was found to decrease with donor age, whereas the ratio of NK to T cell precursor frequency (NK/T ratio) increased with age, suggesting that lymphoid differentiation potential of PB progenitors shifts from T to NK cell lineage with aging. Clonal analyses of CD34+Lin− cells showed that differences in the NK/T ratio were attributable to different distributions of single- and dual-lineage T/NK precursor clones. Because nearly all of the clones retained monocyte and/or granulocyte differentiation potentials in coculture with OP9-DL1 cells, T/NK precursors in PB are considered to be contained in the pool of T/NK/myeloid multipotent progenitors. The age-associated increase in NK over T cell commitment might occur in precursor cells with T/NK/myeloid potential.

Lung cancer susceptibility among atomic bomb survivors in relation to CA repeat number polymorphism of epidermal growth factor receptor gene and radiation dose

Lung cancer is a leading cause of cancer death worldwide. Prevention could be improved by identifying susceptible individuals as well as improving understanding of interactions between genes and etiological environmental agents, including radiation exposure. The epidermal growth factor receptor (EGFR)-signaling pathway, regulating cellular radiation sensitivity, is an oncogenic cascade involved in lung cancer, especially adenocarcinoma. The cytosine adenine (CA) repeat number polymorphism in the first intron of EGFR has been shown to be inversely correlated with EGFR production. It is hypothesized that CA repeat number may modulate individual susceptibility to lung cancer. Thus, we carried out a case-cohort study within the Japanese atomic bomb (A-bomb) survivor cohort to evaluate a possible association of CA repeat polymorphism with lung cancer risk in radiation-exposed or negligibly exposed (<5 mGy) A-bomb survivors. First, by dividing study subjects into Short and Long genotypes, defined as the summed CA repeat number of two alleles < or = 37 and > or = 38, respectively, we found that the Short genotype was significantly associated with an increased risk of lung cancer, specifically adenocarcinoma, among negligibly exposed subjects. Next, we found that prior radiation exposure significantly enhanced lung cancer risk of survivors with the Long genotype, whereas the risk for the Short genotype did not show any significant increase with radiation dose, resulting in indistinguishable risks between these genotypes at a high radiation dose. Our findings imply that the EGFR pathway plays a crucial role in assessing individual susceptibility to lung adenocarcinoma in relation to radiation exposure.

Inverse Associations between Obesity Indicators and Thymic T-Cell Production Levels in Aging Atomic-Bomb Survivors

Reduction of the naive T-cell population represents a deteriorating state in the immune system that occurs with advancing age. In animal model studies, obesity compromises the T-cell immune system as a result of enhanced adipogenesis in primary lymphoid organs and systemic inflammation. In this study, to test the hypothesis that obesity may contribute to the aging of human T-cell immunity, a thousand atomic-bomb survivors were examined for obesity status and ability to produce naive T cells, i.e., T-cell receptor excision circle (TREC) numbers in CD4 and CD8 T cells. The number of TRECs showed a strong positive correlation with naive T cell numbers, and lower TREC numbers were associated with higher age. We found that the TREC number was inversely associated with levels of obesity indicators (BMI, hemoglobin A1c) and serum CRP levels. Development of type-2 diabetes and fatty liver was also associated with lower TREC numbers. This population study suggests that obesity with enhanced inflammation is involved in aging of the human T-cell immune system. Given the fact that obesity increases the risk of numerous age-related diseases, attenuated immune competence is a possible mechanistic link between obesity and disease development among the elderly.

Associations of Ionizing Radiation and Breast Cancer-Related Serum Hormone and Growth Factor Levels in Cancer-Free Female A-Bomb Survivors

Levels of exposure to ionizing radiation are increasing for women worldwide due to the widespread use of CT and other radiologic diagnostic modalities. Exposure to ionizing radiation as well as increased levels of estradiol and other sex hormones are acknowledged breast cancer risk factors, but the effects of whole-body radiation on serum hormone levels in cancer-free women are unknown. This study examined whether ionizing radiation exposure is associated with levels of serum hormones and other markers that may mediate radiation-associated breast cancer risk. Serum samples were measured from cancer-free women who attended biennial health examinations with a wide range of past radiation exposure levels (N u200a=u200a 412, ages 26–79). The women were selected as controls for separate case-control studies from a cohort of A-bomb survivors. Outcome measures included serum levels of total estradiol, bioavailable estradiol, testosterone, progesterone, prolactin, insulin-like growth factor-1 (IGF1), insulin-like growth factor-binding protein 3 (IGFBP-3), and ferritin. Relationships were assessed using repeated-measures regression models fitted with generalized estimating equations. Geometric mean serum levels of total estradiol and bioavailable estradiol increased with 1 Gy of radiation dose among samples collected from postmenopausal women (17%1Gy, 95% CI: 1%–36% and 21%1Gy, 95% CI: 4%–40%, respectively), while they decreased in samples collected from premenopausal women (−11%1Gy, 95% CI: −20%–1% and −12%1Gy, 95% CI: −20%– −2%, respectively). Interactions by menopausal status were significant (P u200a=u200a 0.003 and P < 0.001, respectively). Testosterone levels increased with radiation dose in postmenopausal samples (30.0%1Gy, 95% CI: 13%–49%) while they marginally decreased in premenopausal samples (−10%1Gy, 95% CI: −19%–0%) and the interaction by menopausal status was significant (P < 0.001). Serum levels of IGF1 increased linearly with radiation dose (11%1Gy, 95% CI: 2%–18%) and there was a significant interaction by menopausal status (P u200a=u200a 0.014). Radiation-associated changes in serum levels of estradiol, bioavailable estradiol, testosterone and IGF1 were modified by menopausal status at the time of collection. No associations with radiation were observed in serum levels of progesterone, prolactin, IGFBP-3 or ferritin.

Linkage between Dendritic and T Cell Commitments in Human Circulating Hematopoietic Progenitors

The relationships between commitments of dendritic cells (DCs) and T cells in human hematopoietic stem cells are not well understood. In this study, we enumerate and characterize conventional DC and plasmacytoid DC precursors in association with T cell and thymus-derived types of NK cell precursors among CD34+ hematopoietic progenitor cells (HPCs) circulating in human peripheral blood. By limiting-dilution analyses using coculture with stroma cells expressing Notch1 ligand, the precursor frequencies (PFs) of DCs in HPCs were found to significantly correlate with T cell PFs, but not with NK cell PFs, among healthy donors. Clonal analyses showed that the majority of T/NK dual- and T single-lineage precursors—but only a minority of NK single-lineage precursors—were associated with the generation of DC progenies. All clones producing both DC and T cell progenies were found with monocyte and/or granulocyte progenies, suggesting DC differentiation via myeloid DC pathways. Analyses of peripheral blood HPC subpopulations revealed that the lineage split between DC and T/NK cell progenitor occurs at the stage prior to bifurcation into T and NK cell lineages. The findings suggest a strong linkage between DC and T cell commitments, which may be imprinted in circulating lymphoid-primed multipotent progenitors or in more upstream HPCs.

Lymphocyte subset characterization associated with persistent hepatitis C virus infection and subsequent progression of liver fibrosis.

This study aims to deepen the understanding of lymphocyte phenotypes related to the course of hepatitis C virus (HCV) infection and progression of liver fibrosis in a cohort of atomic bomb survivors. The study subjects comprise 3 groups: 162 HCV persistently infected, 145 spontaneously cleared, and 3,511 uninfected individuals. We observed increased percentages of peripheral blood T(H)1 and total CD8 T cells and decreased percentages of natural killer (NK) cells in the HCV persistence group compared with the other 2 groups after adjustment for age, gender, and radiation exposure dose. Subsequently, we determined that increased T(H)1 cell percentages in the HCV persistence group were significantly associated with an accelerated time-course reduction in platelet counts-accelerated progression of liver fibrosis-whereas T(C)1 and NK cell percentages were inversely associated with progression. This study suggests that T(H)1 immunity is enhanced by persistent HCV infection and that percentages of peripheral T(H)1, T(C)1, and NK cells may help predict progression of liver fibrosis.