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Articles by M. Yamamoto
Total Records ( 4 ) for M. Yamamoto
  H Satoh , T Moriguchi , K Taguchi , J Takai , J. M Maher , T Suzuki , P. T Winnard , V Raman , M Ebina , T Nukiwa and M. Yamamoto

The Nrf2 transcription factor is crucial for regulating the cellular defense against various carcinogens. However, relationship between host Nrf2 and cancer metastasis remains unexplored. To address this issue, we examined susceptibility of Nrf2-deficient mice to pulmonary cancer metastasis following implantation of the mouse Lewis lung carcinoma (3LL) cell line. Nrf2-deficient mice reproducibly exhibited a higher number of pulmonary metastatic nodules than wild-type mice did. The lung and bone marrow (BM) of cancer-bearing Nrf2-deficient mice contained increased numbers of inflammatory cells, including myeloid-derived suppressor cells (MDSCs), a potent population of immunosuppressive cells. MDSCs can attenuate CD8+ T-cell immunity through modification of the T-cell receptor complex exploiting reactive oxygen species (ROS). MDSCs of Nrf2-deficient mice retained elevated levels of ROS relative to wild-type mice. BM transplantation experiments revealed functional disturbance in the hematopoietic and immune systems of Nrf2-deficient mice. Wild-type recipient mice with Nrf2-deficient BM cells showed increased levels of lung metastasis after cancer cell inoculation. These mice exhibited high-level accumulation of ROS in MDSCs, which showed very good coincidence to the decrease of splenic CD8+ T-cells. In contrast, Keap1-knockdown mutant mice harboring high-level Nrf2 expression displayed increased resistance against the cancer cell metastasis to the lung, accompanied by a decrease in ROS in the MDSCs fraction. Our results thus reveal a novel function for Nrf2 in the prevention of cancer metastasis, presumably by its ability to preserve the redox balance in the hematopoietic and immune systems.

  Y. Koizumi , T. Kurita-Ochiai , S. Oguchi and M. Yamamoto
  Porphyromonas gingivalis has been shown to accelerate atherosclerotic lesion development in hyperlipidemic animals. We assessed the potential of a nasal vaccine against P. gingivalis infection for the prevention of atherosclerosis. Apolipoprotein E-deficient spontaneously hyperlipidemic (Apoeshl) mice were nasally immunized with the 40-kDa outer membrane protein (OMP) of P. gingivalis plus cholera toxin (CT) as adjuvant and then challenged intravenously with P. gingivalis strain 381. The animals were euthanized 11 or 14 weeks later. Atheromatous lesions in the proximal aorta of each animal were analyzed histomorphometrically, and the serum concentrations of 40-kDa OMP-specific antibodies and cytokines were determined. The areas of the aortic sinus that were covered with atherosclerotic plaque and the serum levels of inflammatory cytokines and chemokines were increased in Apoeshl mice challenged with P. gingivalis compared to nonchallenged mice. In comparison, nasal immunization with 40-kDa OMP plus CT significantly reduced atherosclerotic plaque accumulation in the aortic sinus and lowered the serum levels of cytokines and chemokines compared to nonimmunized animals. Nasal immunization also induced 40-kDa OMP-specific serum immunoglobulin G (IgG) and saliva IgA antibody responses. These findings suggest that systemic infection with P. gingivalis accelerates atherosclerosis in Apoeshl mice, and 40-kDa OMP plus CT may be an effective nasal vaccine for the reduction of atherosclerosis accelerated by P. gingivalis in the hyperlipidemic mouse model.
  Y Watayo , H Kuramochi , K Hayashi , G Nakajima , H Kamikozuru and M. Yamamoto

Long-term hemodialysis is considered to be a significant risk factor for cancer, but little is known about the use of oxaliplatin in patients on chronic hemodialysis. A 58-year-old man on chronic hemodialysis was treated for unresectable rectal cancer with synchronous hepatic metastasis by FOLFOX6 therapy with therapeutic drug monitoring. Plasma levels of total platinum, ultrafiltrate (free) platinum and 5-fluorouracil were monitored from the start of oxaliplatin administration to 120 h after the end of oxaliplatin infusion. Pharmacokinetic data of free platinum showed a bimodal pattern, decreased rapidly during the first dialysis and subsequently rose until 48 h after oxaliplatin infusion. The free platinum area under the curve was 15.7–18.9 µg h/ml when 40 mg/m2 of oxaliplatin was administered, which was comparable to the area under the curve at 85 mg/m2 in patient with normal renal function. The total platinum level reached a peak immediately before dialysis and gradually decreased. The 5-fluorouracil level decreased rapidly after the start of dialysis and remained constant during the continuous infusion of 5-fluorouracil. Tumor response was judged to be stable disease for >6 months, and no peripheral neuropathy or other toxicity was observed even after 11 courses. FOLFOX6 therapy with reduced dose of oxaliplatin had been safely performed for >6 months without any severe toxicity. The serum levels of free platinum showed bimodal pattern, and this second peak increased the area under the curve of free platinum. This pattern seems to be unique in patients on hemodialysis.

  K Iida , J Mimura , K Itoh , C Ohyama , Y Fujii Kuriyama , T Shimazui , H Akaza and M. Yamamoto

Down-regulation of carcinogen detoxifying enzymes might be a critical factor in tumour formation by increasing the carcinogen concentration in the target organ. Previous reports revealed that the expression of UGT1A mRNA is either lost or decreased in certain human cancer tissues, including urinary bladder cancer. To elucidate this down-regulation mechanism, we used an N-nitrosobutyl (4-hydroxybutyl) amine (BBN)-induced mouse urinary bladder carcinogenesis model. Similar to human cancer, the expressions of Ugt1a6, Ugt1a9 and total Ugt1a mRNA in the BBN-induced bladder cancer were markedly decreased compared with those of normal mice. BBN down-regulated the basal Ugt1a mRNA expression in a time-dependent manner and this was reversible in the first 2 weeks of BBN treatment. However, after 4 weeks of BBN treatment the repression became persistent after the cessation of BBN treatment. Aryl hydrocarbon receptor (AhR) regulates the constitutive and inducible expression of Ugt1a mRNA. We found that the constitutive Ugt1a mRNA expression is decreased in the bladder of AhR knockout (KO) mice. Furthermore, BBN-induced Ugt1a down-regulation was lost in AhR KO mice, and the canonical AhR target gene Cyp1a1 was similarly down-regulated by BBN in the bladder. These results demonstrate that BBN repressed Ugt1a mRNA expression via suppression of AhR signaling pathway during BBN-induced carcinogenesis.

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