Search PubMed⌕ Search

Biomedical subjects

M Suganuma

Publications and source records attributed to M Suganuma.

At least 55 records · Page 3Linked to original sources
PubMed1996

Superinduction of mouse epidermal ornithine decarboxylase activity by repeated 12-o-tetradecanoylphorbol-13-acetate treatments.

A correlation of the levels of epidermal protein kinase C (PKC) isozymes, steady state levels of ornithine decarboxylase (ODC) mRNA, and ODC antizyme with the induction of ornithine decarboxylase (ODC) activity by a second repeat 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment to mouse skin was determined. A single application of TPA to female CD-1 mouse skin leads to a dramatic induction of ODC activity (approximately 3 nmol CO2/60 min/mg protein) which peaks at about 5 h after treatment. However, a superinduction of ODC activity (approximately 13 CO2/60 min/mg protein) is observed upon the second TPA application at 48 or 72 h after the first TPA treatment. Prior application of a tumor initiating dose of 7,12-dimethylbenz[a]anthracine to mouse skin did not influence the degree of induction of ODC by a repeat TPA treatment. Western Blot analyses using antibodies specific to PKC alpha, beta, gamma, delta and epsilon indicate detectable levels of PKC alpha, beta, delta and epsilon in mouse epidermal extracts. A time course of the effects of a single topical application of 20 nmol of TPA to the mouse skin indicate that none of PKC isozymes (alpha, beta, gamma, delta and epsilon) were completely downregulated at times (72 h) when ODC was overinduced by TPA. TPA-induced steady state levels of ODC mRNA did not correlate with the degree of superinduction of ODC activity by TPA. The second TPA treatment, 72 h after the first TPA treatment, which leads to superinduction of ODC activity did not decrease the levels of the ODC-antizyme. The results indicate that superinduction of mouse epidermal ODC activity is regulated in part post-transcriptionally and may not be the result of either a loss of PKC isoform(s) or a decrease in the levels of ODC antizyme.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

Anti-tumor promoting activity of canventol and its synthetic analogs through inhibition of protein isoprenylation.

Canventol, a synthetic compound, is a new inhibitor of tumor promotion on mouse skin by okadaic acid. We previously reported that canventol acts by inhibiting both protein isoprenylation and tumor necrosis factor-alpha (TNF-alpha) release. In this study we examined the potencies of 10 newly synthesized canventol analogs through their effect on mevalonate metabolism, and then examined 3 representative analogs for inhibition of protein isoprenylation. Since canventol in vitro did not directly inhibit farnesyl protein transferase or geranylgeranyl protein transferase-I, the effects of canventol and its synthetic analogs on the fate of [3H]mevalonate in cells were studied. Canventol at 500 microM changed the ratio of newly synthesized sterols (cholesterol and lathosterol) to ubiquinones from 0.7 to 8.2 in NIH/3T3 cells which had previously been labeled with [3H]mevalonate, suggesting that the altered pattern of mevalonate metabolism is associated with inhibition of protein isoprenylation in the cells. We named this ratio the inhibition of protein isoprenylation index (IPI index). The 10 analogs showed a wide range of IPI indices. Two analogs, S3 and S9 had effects similar to, or stronger than, canventol. Three analogs, C44, C46 and C47, with lower IPI indices, inhibited tumor promotion on mouse skin slightly less than canventol itself did. This study shows that inhibition of protein isoprenylation in the cells, indicated by an increase in the IPI index, is a new biomarker for estimating inhibition of tumor promotion.

3T3 Cells↗
PubMed1995

Inhibition of N-methyl-N'-nitro-N-nitrosoguanidine-induced carcinogenesis by (-)-epigallocatechin gallate in the rat glandular stomach.

Recently, an epidemiological study showed a lower risk of gastric cancer among people who consume a large amount of green tea. (-)-Epigallocatechin gallate (EGCG), one of the main constituents of green tea, inhibited tumor promotion by teleocidin in a two-stage carcinogenesis experiment with the use of mouse skin. The inhibitory effect of EGCG on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced carcinogenesis of the glandular stomach in rats was examined. The percentage of tumor-bearing rats in the group treated with MNNG plus EGCG was 31%, compared to 62% in the MNNG group. The difference was statistically significant (P < 0.05). To assess the effect of p.o. administration of EGCG, the gastric mucosal cellular kinetics was examined with the use of the bromodeoxyuridine labeling index, ornithine decarboxylase activity, and tissue polyamine levels. The labeling index of the EGCG treatment group decreased significantly (P < 0.05) compared to the EGCG plus MNNG treatment group. The ornithine decarboxylase activity and tissue spermidine levels were also decreased. On the other hand, the tissue putrescine and spermine levels were partly increased. These findings suggest that EGCG inhibits the cellular kinetics of the gastric mucosa during the promotion stage of MNNG-induced gastric carcinogenesis. EGCG may be useful in preventing gastric carcinogenesis. Moreover, EGCG may be applied clinically without any harmful effects and at a low cost.

Adenocarcinoma↗
PubMed1995

Novel monoclonal antibodies against microcystin and their protective activity for hepatotoxicity.

Six monoclonal antibodies (MAbs) to microcystin-LR (MCLR), a cyclic heptapeptide hepatotoxin isolated from the cyanobacterium Microcystis aeruginosa, were produced. They showed the protective effects on hepatotoxicity of MCLR in vitro and in vivo, and on the inhibition of protein phosphatase by MCLR. Competitive enzyme-linked immunosorbent assays with various microcystins revealed that the six MAbs recognized a part of the molecule, in particular, a tertial structure around Adda, 3-amino-9-methoxy-2,6,8,-trimethyl-10-phenyldeca-4,6-dienoic acid. The specificity of these MAbs varied slightly. In primary rat hepatocyte cultures, all MAbs showed protective effects against the MCLR-induced cell damages, assessed by morphological changes, lactate dehydrogenase release into the medium, and a calorimetric assay to measure the cell viability using a tetrazolium dye. The M8H5 MAb showing the highest affinity for MCLR blocked the lethal effects and hepatocellular damage to mice. In addition, M8H5 MAb recovered protein phosphatase 2A inhibition by MCLR in a dose-dependent manner, while phosphatase inhibition by okadaic acid was not affected. Thus, the MAbs specifically reacted with the microcystins and prevented their biological activities. This is the first report on the protective effects of specific monoclonal antibodies on MCLR-induced toxicity.

Animals↗
PubMed1995

Tautomycin: an inhibitor of protein phosphatases 1 and 2A but not a tumor promoter on mouse skin and in rat glandular stomach.

Tautomycin isolated from Streptomyces spiroverticillatus is an inhibitor of protein phosphatases 1 and 2A. Tautomycin induced hyperphosphorylation of cytokeratin peptides in human keratinocytes (PHK 16-I cells) 30 times less strongly than did okadaic acid. Repeated applications of tautomycin (30 micrograms, 40 nmol/application) did not induce tumor promotion in a two-stage carcinogenesis experiment on mouse skin initiated with 7,12-dimethylbenz[a]anthracene, whereas okadaic acid (1 microgram, 1.2 nmol/application) as a control induced tumor promotion strongly. As for mucosa of rat glandular stomach, tautomycin induced ornithine decarboxylase 4 h after intubation into the stomach. The tumor-promoting activity of tautomycin was next studied in the glandular stomach initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Administration of tautomycin in the diet (1 mg rat-1 day-1), from week 9 to week 52 of the experiment, inhibited rather than enhanced tumor development in the glandular stomach initiated with MNNG. The percentages of tumor-bearing rats of the groups treated with MNNG plus tautomycin, MNNG alone, and tautomycin alone were 20.0%, 40.6%, and 0% respectively in week 52. The reason for the absence of tumor-promoting activity of tautomycin was studied in relation to tumor necrosis factor alpha (TNF alpha), an endogenous tumor promoter. We found that tautomycin neither enhanced TNF alpha mRNA expression in mouse skin nor induced TNF alpha release in a human stomach cancer cell line (KATO III cells), whereas okadaic acid did both. These results indicate that not all inhibitors of protein phosphatases are tumor promoters, and suggest that tumor promotion of the okadaic acid class of compounds is mediated by TNF alpha.

Animals↗
PubMed1995

Specific protein interacting with a tumor promoter, debromoaplysiatoxin, in bovine serum is alpha 1-acid glycoprotein.

Aplysiatoxin and debromoaplysiatoxin, a debrominated form of aplysiatoxin, have both been shown to be potent tumor promoters in a two-stage carcinogenesis experiment on mouse skin. However, debromoaplysiatoxin did not behave like aplysiatoxin in most of the biological assay systems using cultured cells. The discrepancy was supposed to be due to a factor in the bovine serum used for culture, a similar factor not being present in sera of eight other animal species examined. The factor was purified to homogeneity from bovine serum by ammonium sulfate fractionation and chromatographies on DEAE-cellulose, Sephadex G-150, hydroxyapatite, and a reversed-phase HPLC column. The factor was a 40-kDa protein, and partial amino-acid sequencing of its tryptic peptides indicated that the factor is alpha 1-acid glycoprotein. Both the purified factor and the commercially available bovine alpha 1-acid glycoprotein abolished in vitro the activation of protein kinase C by debromoaplysiatoxin but not that by aplysiatoxin. Debromoaplysiatoxin induced differentiation of HL-60 cells into macrophages at a comparable concentration to aplysiatoxin, when serum-free medium was used. These results suggest that alpha 1-acid glycoprotein, which interacts specifically with debromoaplysiatoxin, contained in bovine serum must have masked the in vitro properties of the tumor promoter in the biological assay systems.

3T3 Cells↗
PubMed1995

Activation of protein kinase C by mycobacterial cord factor, trehalose 6-monomycolate, resulting in tumor necrosis factor-alpha release in mouse lung tissues.

Cord factors are mycoloyl glycolipids in cell walls of bacteria belonging to Actinomycetales, such as Mycobacterium, Nocardia and Rhodococcus. They induce granuloma formation in the lung and interstitial pneumonitis, associated with production of macrophage-derived cytokines. We studied how cord factors induce biological activities in the cells. Cord factors isolated from M. tuberculosis, trehalose 6-monomycolate (mTMM) and trehalose 6,6'-dimycolate (mTDM), enhanced protein kinase C (PKC) activation in the presence of phosphatidylserine (PtdSer), diacylglycerol and Ca2+, and mTMM activated PKC alpha more strongly than PKC beta or gamma under the same assay conditions. Kinetic studies of mTMM in response to PKC activation revealed that mTMM increased the apparent affinity of PKC to Ca2+ in the presence of both PtdSer and diolein. Although this is similar to observations with unsaturated fatty acids, such as arachidonic acid, mTMM was synergistic with PtdSer for PKC activation, but arachidonic acid was not. mTMM was also different as regards PKC activation, as phorbol ester was. A single i.p. administration of mTMM to mouse induced tumor necrosis factor-alpha (TNF-alpha) in serum and in the lung, which is a unique target tissue of cord factors. Based on our recent finding that TNF-alpha is an endogenous tumor promoter, the correlation between lung cancer and pulmonary tuberculosis is discussed.

Animals↗
PubMed1994

Nodularin, a potent inhibitor of protein phosphatases 1 and 2A, is a new environmental carcinogen in male F344 rat liver.

Nodularin and microcystin-LR are cyanobacterial toxins and environmental hazards. Nodularin inhibits protein phosphatases 1 and 2A with the same potency as does microcystin-LR, which has recently been identified as a potent tumor promoter in rat liver. Our results suggested that nodularin is also a new tumor promoter in rat liver. A two-stage carcinogenesis experiment in rat liver initiated with diethylnitrosamine and without partial hepatectomy revealed that nodularin stimulated glutathione S-transferase placental form-positive foci in rat liver more effectively than did microcystin-LR, and that nodularin alone induced glutathione S-transferase placental form-positive foci as well as did diethylnitrosamine alone. Thus, nodularin itself is a new liver carcinogen, and microcystin-LR is a tumor promoter rather than a carcinogen. Nodularin induced hyperphosphorylation of cytokeratin peptides 8 and 18 in primary cultured rat hepatocytes 20% more effectively than did microcystin-LR, suggesting that nodularin penetrates more easily into the hepatocytes than does microcystin-LR. Nodularin up-regulated induction of c-jun, jun-B,jun-D,c-fos,fos-B, and fra-1 mRNA transcripts in rat liver after i.p. administration, and the accumulation of the mRNA transcripts was sustained for over 9 h after treatment. The environmental hazards of cyanobacterial toxins are discussed in relation to human primary liver cancer in Qidong county in the People's Republic of China. Our results support this hypothesis and indicate the need for prevention measures against cyanobacterial toxins.

Animals↗
PubMed1994

Two significant aspects of microcystin-LR: specific binding and liver specificity.

Microcystin-LR is a unique and potent liver tumor promoter, belonging to the okadaic acid class compounds. Although microcystin-LR is a potent inhibitor of protein phosphatases 1 and 2A, as is okadaic acid, microcystin-LR has liver specificity dominance. Two significant aspects, specific binding and liver specificity of [3H]dihydromicrocystin-LR, a reduced form of microcystin-LR, were studied and compared with those of [3H]okadaic acid. [3H]-Dihydromicrocystin-LR had higher affinity for the receptors in both the particulate and cytosolic fractions of rat liver and various tissues than had [3H]okadaic acid. Intraperitoneal administration of [3H]dihydromicrocystin-LR into mice resulted in the highest uptake into the liver, 71.5 +/- 6.9% of the total administered radioactivity, whereas p.o. administration resulted in less than 1% uptake into the liver, suggesting that the mechanisms of the incorporation of microcystin-LR into the liver by i.p. and p.o. administrations are greatly different. The presence of associated forms of [3H]dihydromicrocystin-LR with macromolecules in the liver indicates a need for further investigation.

Animals↗
PubMed1994

Increase of labeling indices in gastrointestinal mucosae of mice and rats by compounds of the okadaic acid type.

Effects of compounds of the okadaic acid type (okadaic acid, dinophysistoxin-1, calyculin A and tautomycin) on proliferation by digestive-tract epithelial cells were investigated in mice and rats. In mice, a single oral administration of these agents caused significant enhancement of BrdU labeling indices in a dose/response manner. Exceptions showing no response were limited to the pyloric mucosa for okadaic acid, the pyloric and fundic mucosa for calyculin A and the pyloric mucosa for tautomycin. Sequential analysis of labeling indices after a single oral administration of dinophysistoxin-1 revealed two peaks of cell proliferation at 18 h and 36 h in the esophagus, ileum and colon. The labeling indices of the forestomach, fundus, pylorus and jejunum, on the other hand, continuously increased from 6 h after the administration. Elevated proliferation was also observed in the skin after 30 h or after, but no effects on the liver or kidney were evident. A single oral administration of the okadaic acid type of compounds also dose-dependently enhanced cell proliferation of the rat digestive tract. These results strongly suggest that the okadaic acid class of compounds may exert promoting potential for the gastrointestinal mucosa when administered orally.

Administration, Oral↗
PubMed1994

Tumor necrosis factor-alpha, a new tumor promoter, engendered by biochemical studies of okadaic acid.

Okadaic acid is a potent tumor promoter on mouse skin and in rat glandular stomach, and an inhibitor of PP-1 and PP-2A. How okadaic acid biochemically induces tumor promotion in these tissues was reviewed. Okadaic acid bound to a catalytic subunit of PP-1 and PP-2A and induced hyperphosphorylation of proteins, such as vimentin, cytokeratins, HSP 27, and tumor suppressor gene products. Since one of the okadaic acid class compounds, microcystin-LR, induced tumor promotion in rat liver, the okadaic acid pathway mediated through inhibition of PP-1 and PP-2A is seen to be a general biochemical process of tumor promotion in various organs. The biochemical mimicry of okadaic acid by TNF-alpha led us to find that TNF-alpha is an endogenous tumor promoter. The study of tumor promotion in two-stage carcinogenesis experiments with the okadaic acid class of compounds engendered a new tumor promoter applicable to human cancer development.

Animals↗
PubMed1994

Inhibitory effects of (-)-epigallocatechin gallate on spontaneous hepatoma in C3H/HeNCrj mice and human hepatoma-derived PLC/PRF/5 cells.

The inhibitory effect of (-)-epigallocatechin gallate (EGCG), a main constituent of Japanese green tea, on spontaneous hepatoma in C3H/HeNCrj mice was investigated. A total of 72 mice were divided into three groups; the control group without EGCG, and two experimental groups receiving 0.05% (w/w) or 0.1% EGCG in drinking water. EGCG reduced the incidence of hepatoma-bearing mice from 83.3% (control) to 56.0% (0.05% EGCG) and 52.2% (0.1% EGCG), and also reduced the average number of hepatomas per mouse from 1.83 (control) to 0.72 (0.05% EGCG) and 0.91 (0.1% EGCG) at week 65. Ridit analysis of the distribution of the number of hepatomas in each group revealed that EGCG significantly increased the rate of mice without hepatoma in the two EGCG groups as compared to the control. EGCG did not affect body weight gain, food consumption or any serum biochemical parameter. EGCG inhibited the growth and secretion of alpha-fetoprotein by human hepatoma-derived PLC/PRF/5 cells without decreasing their viability. These results indicate that EGCG may be a practical, nontoxic preventive agent against human hepatoma.

Animals↗
PubMed1994

Sarcophytol A: a new chemotherapeutic and chemopreventive agent for pancreatic cancer.

Sarcophytol A (SaA), a cembrane-type diterpene isolated from the marine soft coral Sarcophyton glaucum showed anticancer and cancer preventive effects in two different experiments. Growth of transplanted human pancreatic cancer cells (MIA paca-2, 1 x 10(7)) in nude mice (BALB/C 4W female) (Experiment 1) and pancreatic carcinogenesis induced by N-nitrobis-(2-hydroxypropyl) amine (BHP, 500 mg/kg) in Syrian golden hamsters (7W female) (Experiment 2) were inhibited by feeding the animals a diet containing 0.01% SaA. In Experiment 1, on day 29 after transplantation, tumor volume was significantly less in the SaA group than in the control group (1,759 + 310 mm3 vs. 2,364 + 467 mm3) (p < 0.05). In Experiment 2, the incidence of pancreatic tumors in the SaA group was 42.8% and that in the control group was 90.0% at 25-27 weeks. Thus, pancreatic carcinoma developed more slowly in the SaA group than in the control group. In addition, the incidence of atypical ductal hyperplasia and carcinoma in situ was lower in the SaA group. These results indicate that oral SaA administration is an effective vehicle for inhibition of certain types of cancer in hamsters.

Animals↗
PubMed1994

A new tumor promotion pathway and its inhibitors.

Tumor promotion is a critical point in multistage carcinogenesis in humans. We have identified a common biochemical and molecular tumor promotion mechanism, the okadaic acid pathway, applicable in various organs. Tumor promotion by the okadaic acid class of compounds is mediated through inhibition of protein phosphatases 1 and 2A, resulting in an increase of protein phosphorylation and a subsequent expression of cell proliferation genes. Recently, we demonstrated that okadaic acid induced the release of mouse tumor necrosis factor-alpha (mTNF-alpha) from BALB/3T3 cells. The first part of this review discusses the link between the okadaic acid pathway and TNF-alpha as endogenous tumor promoters in vivo. Inhibitors of tumor promotion are varied. For the purpose of cancer chemoprevention in humans, the inhibitors sarcophytol A, canventol, and (-)-epigallocatechin gallate (EGCG) were studied and the results are presented. The inhibitory mechanisms also were varied: sarcophytol A inhibited H2O2 formation by TPA-activated human polymorphonuclear leukocytes; canventol inhibited protein isoprenylation in the cells; and EGCG, which is a main constituent of Japanese green tea, is an antioxidant. These inhibitors are promising cancer chemopreventive agents. Study of the essential tumor promotion mechanisms will facilitate the development of cancer chemopreventive agents.

Anticarcinogenic Agents↗
PubMed1993

Canventol inhibits tumor promotion in CD-1 mouse skin through inhibition of tumor necrosis factor alpha release and of protein isoprenylation.

A synthetic compound named canventol, 2-isopropyl-4-isopropylidencyclohex-2-ene-1-ol, inhibited tumor promotion of okadaic acid on mouse skin initiated with 7,12-dimethylbenz(a)anthracene in two-stage carcinogenesis experiments more strongly than sarcophytol A, isolated from a soft coral, although canventol has a simpler structure than sarcophytol A. Their mechanisms of action were studied based on our recent evidence that tumor necrosis factor alpha release induced by okadaic acid is an essential mechanism of tumor promotion. Canventol inhibited mouse tumor necrosis factor alpha release from BALB/3T3 cells less strongly than sarcophytol A, indicating that canventol has additional activity. Canventol inhibited isoprenylation of proteins with various molecular weights, such as M(r) 22,000, 17,000, and 13,000, whereas sarcophytol A did not show significant inhibition. Thus, a potent anticarcinogenic activity of canventol is mediated through the inhibitory bifunctions of tumor necrosis factor alpha release and of protein isoprenylation. Since canventol is less toxic to cells than sarcophytol A, these bifunctions are useful markers for screening for new cancer chemopreventive agents.

3T3 Cells↗
PubMed1993

Tumor necrosis factor acts as a tumor promoter in BALB/3T3 cell transformation.

Tumor necrosis factor (TNF), a cytokine, and okadaic acid, a tumor promoter, strongly phosphorylated the same proteins, vimentin and heat shock protein 27, although their time courses were different. Human TNF-alpha at a concentration of 0.6 nM markedly stimulated transformation of BALB/3T3 cells initiated with 3-methylcholanthrene. The human TNF-alpha was about 1000 times more effective than the chemical tumor promoters, okadaic acid and 12-O-tetradecanoylphorbol-13-acetate. TNF induced growth of v-Ha-ras transfected BALB/3T3 cells (Bhas 42 cells), whereas it did not induce growth of nontransfected BALB/3T3 cells. Okadiac acid induced mouse TNF-alpha from Bhas 42 and BALB/3T3 cells. The results suggest that a chemical tumor promoter induces the secretion of TNF-alpha from various cells. The TNF then acts as an endogenous tumor promoter in vivo.

3T3 Cells↗
PubMed1993

Hyperphosphorylation of cytokeratins by okadaic acid class tumor promoters in primary human keratinocytes.

Okadaic acid, dinophysistoxin-1 (35-methylokadaic acid), and calyculin A are potent tumor promoters on mouse skin (H. Fujiki, M. Suganuma, S. Nishiwaki, S. Yoshizawa, J. Yatsunami, R. Matsushima, H. Furuya, S. Okabe, S. Matsunaga, and T. Sugimura. In: R. D'Amato, T. J. Slaga, W. Farland, and C. Henry (eds.), Relevance of Animal Studies to the Evaluation of Human Cancer Risk, pp. 337-350. New York: John Wiley and Sons, Inc., 1992). These tumor promoters, which are also inhibitors of protein phosphatases 1 and 2A, induced hyperphosphorylation of M(r) 60,000, M(r) 58,000, M(r) 56,000, M(r) 52,000, M(r) 42,000, and M(r) 27,000 proteins in PHK 16-I cells, human keratinocytes immortalized by human papillomavirus type 16. Except for the M(r) 27,000 protein, these hyperphosphorylated proteins were identified to be cytokeratin peptides (CK) CK 5, CK 6, CK 7, CK 16, and CK 19, by anti-cytokeratin antibodies. CK 5 and CK 6 were more strongly phosphorylated than CK 16 and CK 19. The in vitro hyperphosphorylation of these cytokeratins was also found by incubation with an enzyme fraction containing a mixture of protein phosphatase 2A and protein kinases isolated from mouse brain and various concentrations of dinophysistoxin-1. Indirect immunofluorescence microscopy with anti-cytokeratin antibodies revealed that the hyperphosphorylated cytokeratins had retracted to the perinuclear area. The hyperphosphorylated M(r) 27,000 protein was identified as a heat shock protein, HSP27. Hyperphosphorylation of HSP27 and intermediate filaments, such as cytokeratins, is one of the early biochemical changes, or pleiotropic effects, in cells induced by the okadaic acid class of tumor promoters.

Blotting, Western↗