Hiroo Nakajima

Transgenerational transmission of radiation- and chemically induced tumors and congenital anomalies in mice: studies of their possible relationship to induced chromosomal and molecular changes

This article provides a broad overview of our earlier studies on the induction of tumors and congenital anomalies in the progeny of X-irradiated or chemically treated mice and our subsequent (published, hitherto unpublished and on-going) investigations aimed at identifying potential relationships between genetic changes induced in germ cells and the adverse effects manifest as tumors and congenital anomalies using cytogenetic and molecular approaches. The earlier studies document the fact that tumors and congenital anomalies can be induced by irradiation or treatment with certain chemicals such as urethane and that these phenotypes are heritable i.e., transmitted to generations beyond the first generation. These findings support the view that transmissible induced genetic changes are involved. The induced rates of congenital abnormalities and tumors are about two orders of magnitude higher than those recorded in the literature from classical mutation studies with specific locus mutations. The cytogenetic studies addressed the question of whether there were any relationships between induced translocations and induced tumors. The available data permit the inference that gross chromosomal changes may not be involved but do not exclude smaller induced genetic changes that are beyond the resolution of the techniques used in these studies. Other work on possible relationship between visible chromosomal anomalies (in bone marrow preparations) and tumors were likewise negative. However, there were indications that some induced cytogenetic changes might underlie induced congenital anomalies, i.e., trisomies, deletions and inversions were observed in induced and transmissible congenital anomalies (such as dwarfs, tail anomalies). Studies that explored possible relationships between induction of minisatellite mutations at the Pc-3 locus and tumors were negative. However, gene expression analysis of tumor (hepatoma)-susceptible offspring of progeny descended from irradiated male mice showed abnormal expression of many genes. Of these, only very few were oncogenes. This lends some support to our hypothesis that cumulative changes in gene expression of many genes, which perform normal cellular functions, may contribute to the occurrence of tumors in the offspring of irradiated or chemically treated mice.

No Evidence of Increased Mutation Rates at Microsatellite Loci in Offspring of A-Bomb Survivors

Abstract To evaluate the genetic effects of A-bomb radiation, we examined mutations at 40 microsatellite loci in exposed families (father-mother-offspring, mostly uni-parental exposures), which consisted of 66 offspring having a mean paternal dose of 1.87 Gy and a mean maternal dose of 1.27 Gy. The control families consisted of 63 offspring whose parents either were exposed to low doses of radiation (< 0.01 Gy) or were not in the cities of Hiroshima or Nagasaki at the time of the bombs. We found seven mutations in the exposed alleles (7/2,789; mutation rate 0.25 × 10−2/locus/generation) and 26 in the unexposed alleles (26/7,465; 0.35 × 10−2/locus/generation), which does not indicate an effect from parental exposure to radiation. Although we could not assign the parental origins of four mutations, the conclusion may hold since even if we assume that these four mutations had occurred in the exposed alleles, the estimated mean mutation rate would be 0.39 × 10−2 in the exposed group [(7 + 4)/2,789)], which is slightly higher than 0.35 × 10−2 in the control group, but the difference is not statistically significant.

Condensin mutations and abnormal chromosomal structures in pyothorax‐associated lymphoma

Transfer of genetic information during mitosis is accurately conducted by proper condensation and segregation of chromosomes, for which condensins play a central role. Both condensin I and II have common structural maintenance of chromosomes subunits, named hCAP‐C and hCAP‐E. Pyothorax‐associated lymphoma (PAL) is a non‐Hodgkins lymphoma developing in the pleural cavity of patients with long‐standing pyothorax. Mutations of hCAP‐C and hCAP‐E were investigated in 24 leukemia–lymphoma cell lines including eight PAL cell lines, and their influences in chromosome morphology were evaluated. Heterozygous point mutations within hCAP‐C were found in two PAL cell lines and corresponding tumor samples (OPL‐3 and OPL‐7). Deletion of exon 24 within hCAP‐E and a point mutation at the donor splice site of intron 24 were detected in OPL‐5 and original tumor samples. OPL‐5 showed an extensive reduction in expression of not only hCAP‐E but also hCAP‐C proteins. OPL‐5 occasionally showed the chromosome bridge in anaphase and telophase, indicating that segregation is not accurate. OPL‐7 showed reduced hCAP‐C protein expression, abnormality in chromosome length and width, and abnormal aggregates of hCAP‐C protein. These findings indicated that condensin gene alteration might play a role in genome instability, which accelerates the accumulation of other gene alterations in PAL. (Cancer Sci 2007; 98: 1041–1047)

Dose rate effectiveness and potentially lethal damage repair in normal and double-strand break repair deficient murine cells by γ-rays and 5-fluorouracil

SCID (severe combined immunodeficiency) fibroblasts established from C.B 17-scid/scid embryos showed higher sensitivity to high (1.105 Gy/min) and low (0.00069 Gy/min) dose rate gamma-rays and also to 5-fluorouracil, a cancer sedative producing double-strand breaks, than wildtype cells from C.B17- +/+ embryos. Furthermore, SCID cells were deficient in repairing DNA damage induced by high dose rate gamma-rays even after dose fractionation and after 24 h recovery periods, while wildtype cells showed an apparent repair ability on DNA damage after these gamma-ray exposures. This is the first report to prove that SCID cells lack the repair of gamma-ray-induced potentially lethal damage and also of 5-fluorouracil-induced double-strand breaks. However, SCID cells showed a significantly higher survival rate by low dose rate exposure than by high dose rate exposure as in the case of wildtype cells, indicating that SCID cells have a deficiency in DNA repair for high dose rate gamma-rays, but not for low dose rate exposure. This suggests an important finding that the dose rate effect (diminution of cell killing by low dose rate exposure) is caused not only by the repair of double-strand breaks induced by gamma-rays but in most parts by less yields of double-strand breaks due to dispersed or low intensity ionization in the cell.

Morphology and function of human benign tumors and normal thyroid tissues maintained in severe combined immunodeficient mice

In the improved SCID (severe combined immunodeficient) mice, various human benign tumors of the head and neck region were well maintained morphologically and functionally for 3 years until the experiments were terminated, e.g. transplanted parathyroid adenoma secreted parathyroid hormone (PTH) in the SCID mice for more than 1 year. Normal human thyroid tissue was also well maintained in the SCID mice for 3 years. Rapid and high uptake of radioiodine into the transplanted human thyroid tissue was observed. Furthermore, transplanted human thyroid tissue secreted thyroid hormone (T3) and T3 secretion was stimulated by the injection of human thyroid stimulating hormone (TSH). These findings suggest that the improved SCID mice will provide an invaluable experimental system for investigating the function of normal human tissues and the influence of endogenous and exogenous factors on human tissues.

Inhibiting effects of nicotinamide on urethane-induced malformations and tumors in mice☆

The antipellagratic vitamin, nicotinamide, significantly suppressed urethane-induced malformations, when it was given intraperitoneally to pregnant JCL:ICR mice immediately after a single subcutaneous injection of urethane (1.0 mg/g) on the 9th day of gestation. The level of inhibition increased with the doses of nicotinamide: 33.0, 55.8, and 70.0% at doses of 0.1, 0.3, and 0.5 mg/g, respectively. Polydactyly and tail anomalies were markedly suppressed by the post-treatment with nicotinamide, while cleft palates were less effectively suppressed. Nicotinamide was still effective, when it was given during the period of 24-48 h after urethane treatment. Furthermore, dietary administration of nicotinamide also reduced urethane-induced malformations. The level of inhibition was 39.4 and 61.1% at 0.5 and 1.0% of nicotinamide in the diet, respectively. Higher doses of nicotinamide (3 and 5% in diet) also inhibited urethane-induced malformations, but not so effectively as lower doses. The inhibiting effects of nicotinamide on the spontaneous incidence of cleft lips and palates in CL/Fr mice were significant at a low dose (0.5% in diet), but not at a higher dose (1.0%). When [carbonyl-14C]nicotinamide was given to pregnant mice, nicotinamide and small amounts of nicotinamide adenine dinucleotide (NAD+), but not nicotinic acid, were detected chromatographically in the fetus and placenta, indicating that nicotinamide or NAD+ acts directly on the fetus to suppress urethane-induced malformations. A preliminary study revealed that urethane-induced lung tumorigenesis in JCL:ICR mice was also inhibited by post-treatment with nicotinamide in the diet. The level of inhibition was proportional to the dose of nicotinamide, that is, 35.0 and 62.8% at 1.0 and 2.5% of nicotinamide in the diet, respectively.

Reduction of leaky lymphocyte clones producing immunoglobulins and thymic lymphocytic leukemia by selective inbreeding of SCID (severe combined immunodeficiency) mice.

Selective inbreeding of C.B17-scid/scid mouse pairs showing undetectable IgG and IgM has been carried out in order to reduce the mortality of mice by early occurrence of thymic lymphocytic leukemia and abnormal lymphocyte clones producing immunoglobulins, both of which inhibit the successful heterotransplantation of normal and neoplastic human tissues. Although the majority of C.B17-scid/scid mice showed undetectable (< 1 microgram/ml) or low level (< or = 25 micrograms/ml) of serum IgG and IgM, some produced abnormally high concentrations of IgG and IgM (> 25 micrograms/ml). The incidence of such mice showing higher levels of IgG was very high at F1 and F2 generation (10/55, 18.2%), but significantly low after the F3 generation (18/446, 4.0%, p << 0.001). Although leukemia incidence was very high at F4 to F5 generations (8/40, 20.0%), death from leukemia was not observed early in life (4-6 months after birth) at F7 to F10 generations (0/36, 0%, p < 0.01) and was very low during the age of 6-10 months after the F8 generation (11/66, 16.7% at F4 and F5 vs 4/93, 4.3% at F8-10), p < 0.01). Scid mice improved by the selective inbreeding will provide an invaluable experimental system for the heterotransplantation of normal and neoplastic human tissues.

A Molecular Clock Regulates Angiopoietin-Like Protein 2 Expression

Various physiological and behavioral processes exhibit circadian rhythmicity. These rhythms are usually maintained by negative feedback loops of core clock genes, namely, CLOCK, BMAL, PER, and CRY. Recently, dysfunction in the circadian clock has been recognized as an important foundation for the pathophysiology of lifestyle-related diseases, such as obesity, cardiovascular disease, and some cancers. We have reported that angiopoietin-like protein 2 (ANGPTL2) contributes to the pathogenesis of these lifestyle-related diseases by inducing chronic inflammation. However, molecular mechanisms underlying regulation of ANGPTL2 expression are poorly understood. Here, we assess circadian rhythmicity of ANGPTL2 expression in various mouse tissues. We observed that ANGPTL2 rhythmicity was similar to that of the PER2 gene, which is regulated by the CLOCK/BMAL1 complex. Promoter activity of the human ANGPTL2 gene was significantly induced by CLOCK and BMAL1, an induction markedly attenuated by CRY co-expression. We also identified functional E-boxes in the ANGPTL2 promoter and observed occupancy of these sites by endogenous CLOCK in human osteosarcoma cells. Furthermore, Cry-deficient mice exhibited arrhythmic Angptl2 expression. Taken together, these data suggest that periodic expression of ANGPTL2 is regulated by a molecular clock.

A rapid and easy method for the qualitative detection of intracellular deposition of inhaled nanoparticles

UNLABELLED In recent years, nanoparticle exposure risk has drawn increasing attention from the research community and the general public. However, analysis of nanoparticles is hindered by their small size, which prevents the development of methods for their detection in cells and tissues. For risk assessment of nanoparticle exposure, it is important to measure the exact amount of deposited material in pulmonary tissue. Using a nanoparticle exposure device, A/JJmsSlc mice were chronically exposed transtracheally to anatase-type titanium dioxide particles. A microscope-integrated laser Raman spectrometer was used to detect differentially stained macrophages in a pulmonary wash obtained from the mice exposed to the particles. This detection method allowed rapid and easy sample collection and qualitative analysis, and the method may be useful for conducting large-scale evaluations in workers exposed to environments heavily contaminated with nanoparticles. FROM THE CLINICAL EDITOR This paper discusses a microscope-integrated laser Raman spectrometer method to measure the exact amount of nanoparticles deposited in pulmonary tissue. This method allows rapid sample collection, qualitative analysis, and may be useful for large-scale evaluations.

Telomere dysfunction and inactivation of the p16INK4a/Rb pathway in pyothorax‐associated lymphoma

Previous studies have indicated that genome instability is involved in the lymphomagenesis of pyothorax‐associated lymphoma (PAL), which develops in patients with a long‐standing history of pyothorax. One of the well‐known causes of genome instability is telomere dysfunction. In the present study, the condition of telomeres was analyzed in the cell lines and clinical samples from PAL. Telomere length (TL) in PAL cell lines was extremely short (<4.5 kbp). TL in tumor samples was broad in range, and shorter than that in the peripheral blood leukocytes from the matched patients. Three of five PAL cell lines showed frequent loss of telomere signals (telomere erosion); however, telomerase activity in PAL cell lines was similar to that in Burkitt lymphoma cell lines. Rb expression was detected in three PAL cell lines and four of 15 clinical samples, respectively. Rb protein expressed in three PAL cell lines was heavily phosphorylated, indicating that function of Rb protein was suppressed. p16INK4a expression was not detected in either cell lines or clinical samples. The promoter region in p16INK4a was heavily methylated in all cell lines as well as the clinical samples. Inactivation of the p16INK4a/Rb pathway may allow continuous cell division and critical telomere shortening, which induce genome instability, finally leading to malignant transformation. Taken together, telomere dysfunction and inactivation of the p16INK4a/Rb pathway might play a role for PAL development. (Cancer Sci 2007; 98: 978–984)