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Biomedical subjects

H Fujiki

Publications and source records attributed to H Fujiki.

At least 253 records · Page 14Linked to original sources
PubMed1983

Inhibition of specific binding of [3H]phorbol-12,13-dipropionate to an epidermal fraction by certain irritants and irritant promoters of mouse skin.

Specific binding of [3H]phorbol-12,13-dipropionate ([3H]PDPr) to a particulate fraction of mouse skin is demonstrated (KD = 35 nM; Rt = 1.2 pmol/mg protein). A series of compounds of the diterpene ester, indole akaloid and polyacetate types with different degrees of activity as skin tumor promoters and/or irritants have been tested for their capacity to inhibit specific [3H]PDPr binding. Three main categories are found: (i) compounds which exhibit a positive correlation between their potency as irritants and promoters in vivo and their inhibition of specific binding in vitro: 12-O-tetradecanoylphorbol-13-acetate, 3-O-tetradecanoylingenol, pimelea factor P2, 'teleocidin', dihydroteleocidin B, and lyngbyatoxin are active in vivo and in vitro, whereas phorbol and ingenol are inactive and 4-O-methyl-12-O-tetradecanoyl-phorbol-13-acetate is weakly active; (ii) compounds which are strong irritants and inhibitors of binding but are weak or practically non-promoters: mezerein, 12-O-retinoylphorbol-13-acetate and milliamine C; (iii) strong irritants which are weak or marginally active inhibitors of binding: debromoaplysiatoxin and resiniferatoxin. Some consequences of these findings with respect to interpretations of the biochemical mechanism(s) of tumor promotion are discussed.

Animals↗
PubMed1983

New classes of environmental tumor promoters: indole alkaloids and polyacetates.

Tumor promoters are known to induce ODC activity in mouse skin and that this induction can be inhibited by the application of 13-cis-retinoic acid. These two properties of tumor promoters were utilized for screening new tumor promoters in our environment. Two new classes of tumor promoters are presented: indole alkaloids (teleocidin and lyngbyatoxin A) and polyacetates (aplysiatoxin and debromoaplysiatoxin). Teleocidin from streptomyces and lyngbyatoxin A, from the blue-green alga, Lyngbya majuscula, were able to induce ODC activity in mouse skin and showed various biological activities similar to those of TPA. Teleocidin and lyngbyatoxin A are indole alkaloids. Their tumor promoting activities became apparent in the mouse skin through a two-stage carcinogenicity test. The tumor incidence of the group treated with DMBA plus teleocidin was 100% at week 30, which was similar to that of the group given DMBA and TPA. The in vivo carcinogenicity test with lyngbyatoxin A is still underway. The tumor incidence of the group treated with DMBA plus lyngbyatoxin A is 80% at week 21. A second new class of tumor promoter is polyacetate. Aplysiatoxin and debromoaplysiatoxin were isolated from another variety of blue-green alga. Aplysiatoxin and debromoaplysiatoxin induce ODC to the same degree of potency. However, aplysiatoxin induced various membrane effects, such as adhesion of cells and turnover of phospholipid with a similar concentration of TPA, teleocidin and lyngbyatoxin A. On the other hand, debromoaplysiatoxin required an amount almost 100 times greater to achieve the same effects. We are convinced of the possibility that various classes of tumor promoters exist in our environment.

Acetates↗
PubMed1983

Nakahara memorial lecture. New classes of tumor promoters: teleocidin, aplysiatoxin, and palytoxin.

Teleocidin and aplysiatoxin, which are structurally different from 12-O-tetradecanoylphorbol-13-acetate (TPA), were found to be potent tumor promoters in two-step mouse skin carcinogenesis. The class of teleocidin includes dihydroteleocidin B, teleocidin, and lyngbyatoxin A. Teleocidin, which is a mixture of 93% teleocidin A and 7% teleocidin B, was isolated from Streptomyces mediocidicus as a strong skin irritant. Teleocidin A consists of C-14S-teleocidin A and C-14R-teleocidin A. One teleocidin A-isomer corresponds to lyngbyatoxin A, which was isolated from the blue-green alga, Lyngbya majuscula. Teleocidin B has four isomers, C-14, C-17-diastereomers. The two teleocidin A-isomers and three of the teleocidin B-isomers (all but one, which was obtained in too low yield) were shown to be biologically active and also potent tumor promoters. Synthetic analogues (indolactams) of teleocidin were obtained and their structure-activity relations were examined by several biological tests. The finding that only (-)-indolactam-V was active showed that the S, S configuration of native teleocidin was necessary for expression of the activity. The class of aplysiatoxin, which was isolated from the blue-green alga, L. majuscula, includes debromoaplysiatoxin, aplysiatoxin, bromoaplysiatoxin, and oscillatoxin A (nordebromoaplysiatoxin). The former three were potent tumor promoters, while oscillatoxin A was a moderate one. Dibromoaplysiatoxin, which is a chemically brominated derivative of debromoaplysiatoxin, in addition to aplysiatoxin and bromoaplysiatoxin, possessed the same promoting activity as that of oscillatoxin A.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylamides↗
PubMed1983

Distinct inhibitory effects of dihydroteleocidin B and the phorbol ester tumor promoters on the adipocyte differentiation of 3T3-L1 cells.

An indole alkaloid tumor promoter, dihydroteleocidin B, was able to modulate a membrane property of 3T3-L1 preadipocytes, showing an almost complete reduction of epidermal growth factor binding capacity. This receptor modulating potency of dihydroteleocidin B, was 10 times that of a phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Dihydroteleocidin B, however, had little effect on the epidermal growth factor receptors of the adipocyte stage of 3T3-L1. Adipocyte differentiation was induced by treating growth-arrested 3T3-L1 cells with dexamethasone and 1-methyl-3-isobutylxanthine for 48 hr. These inducers initiated DNA synthesis, led to one full cycle of cell division, and triggered the adipocyte differentiation program. Dihydroteleocidin B almost completely inhibited this differentiation at concentrations of 1 to 10 ng/ml (10(-9) to 10(-8) M). The inhibition was observed regardless of when the tumor promoter was added: before, during, or after the addition of inducers. Similar inhibition was also observed by TPA, but with over 90% less efficiency than that of dihydroteleocidin B. TPA was most effective when it was added during the inducer treatment. Both dihydroteleocidin B and TPA stimulated DNA synthesis to the same level during the initial 22 hr. The DNA synthesis stimulated by dihydroteleocidin B resulted in extraordinary enhancement of cell proliferation, whereas TPA-treated 3T3-L1 cells did not divide. These findings suggest that dihydroteleocidin B and TPA have distinct potencies in interfering with the mechanisms of adipocyte differentiation and that presumably they are different in action of tumorigenesis.

1-Methyl-3-isobutylxanthine↗
PubMed1983

Comparative effects of aplysiatoxin, debromoaplysiatoxin, and teleocidin on receptor binding and phospholipid metabolism.

We have compared the activities of aplysiatoxin and debromoaplysiatoxin, two polyacetate marine algae toxins, with teleocidin, a tumor-promoting indole alkaloid from Streptomyces, with respect to inhibition of specific binding of epidermal growth factor, and phorbol-12,13-dibutyrate to their respective receptors and ability to stimulate the release of radioactivity from cells prelabeled with choline or arachidonic acid. Although these compounds have chemical structures that are quite different from the phorbol esters, both aplysiatoxin and teleocidin are essentially equipotent with the potent tumor promoter 12-O-tetradecanoylphorbol-13-acetate in all four assays. The fact that aplysiatoxin and teleocidin inhibit phorbol-12,13-dibutyrate-receptor binding suggests that their biological activities are mediated by binding to the same receptors utilized by the phorbol esters. Debromoaplysiatoxin, a debrominated form of aplysiatoxin, is about 10-fold weaker than aplysiatoxin in inhibiting epidermal growth factor and phorbol-12,13-dibutyrate-receptor binding, but is equipotent with aplysiatoxin in stimulating the release of lipid metabolites from the prelabeled cells. The results are discussed in terms of possible heterogeneity of cellular receptors for this group of compounds.

Alkaloids↗
PubMed1983

Critical biochemical and regulatory events in malignant transformation in vitro.

Oncogenic transformation of hamster embryo cells and mouse C3H 10T1/2 can be modified by a variety of agents and conditions which alter events at early stages of initiation and at later stages of promotion. Inhibition of poly(ADP-ribose) synthesis by low concentrations of benzamide and 3-aminobenzamide inhibits the induction of transformation by ultraviolet light, X-rays, and chemical carcinogens as well as inhibiting the enhancement of transformation by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). The suppression of transformation by the benzamides is observed under conditions where the inhibitors reduce poly(ADP-polymerization) by about 75%, have no influence on damage induced by X-rays or alkylating chemicals and enhance sister chromatid exchanges. A modification of the physiological state of the cells by rendering them hypothyroid also results in an inhibition of transformation by radiation and chemical carcinogens and a suppression of promotion by teleocidin and TPA. When thyroid hormone is added to the medium radiogenic transformation and its dramatic enhancement by the tumor promoters is observed, with teleocidin being over 100 times as effective as a promotor as TPA. Our results suggest that mechanisms regulating initiation and promotion are associated with alterations in poly(ADP-ribosylation), causing changes in gene control and expression and may differ from those associated with the induction of sister chromatid exchanges. The results also suggest that genetic events taking place in both the early events (initiation) and late events (promotion) in malignant transformation are highly dependent on the presence of thyroid hormones.

Animals↗
PubMed1983

Increase in the synthesis of a Mr 32,000 protein in BALB/c 3T3 cells treated with tumor-promoting indole alkaloids or polyacetates.

The synthesis of a unique protein with a molecular weight of 32,000 (p32) in BALB/c 3T3 cells has been shown previously to increase after treatment with potent tumor-promoting phorbol esters (Hiwasa et al., Proc. Natl. Acad. Sci. U. S. A., 79: 1800, 1982). In the present study, two new classes of tumor promoters which are structurally different from phorbol esters were investigated for their potencies to enhance p32 synthesis. Teleocidin, dihydroteleocidin B, and lyngbyatoxin A, which are indole alkaloid tumor promoters, enhanced p32 synthesis to the same extent that 12-O-tetradecanoylphorbol-13-acetate did. However, no increase was observed by treatment with the biologically inactive hydrolysate of teleocidin. Polyacetate tumor promoters such as aplysiatoxin and debromoaplysiatoxin also stimulated p32 synthesis, but their effective concentrations were higher than those of 12-O-tetradecanoylphorbol-13-acetate. When 3T3 cells were treated with a combination of two of the three tumor promoters, TPA, teleocidin, and aplysiatoxin, no synergistic effect of p32 synthesis was observed. This implies that these tumor promoters enhance the synthesis of p32 through the same mechanism.

Alkaloids↗
PubMed1983

Effects of tumor promoters on the frequency of metallothionein I gene amplification in cells exposed to cadmium.

Three potent tumor promoters of different classes, 12-O-tetradecanoylphorbol-13-acetate, dihydroteleocidin B, and aplysiatoxin, and two moderate tumor promoters, mezerein and debromoaplysiatoxin, enhanced the frequency of appearance of cadmium-resistant Chinese hamster lung cells when the cells were exposed to cytotoxic levels of CdCl2. With these compounds, the activity to induce cadmium-resistant cells correlated well with the potency of tumor-promoting activity. Cadmium resistance, which persisted after removal of the tumor promoters, was associated with the overproduction of metallothionein I messenger RNA. The amplified metallothionein I genes were shown by Southern blotting experiments. The relevance of the gene amplification caused by tumor promoters is discussed in relation to cancer development and progression.

Alkaloids↗
PubMed1983

Distinct responses of 3T3-L1 cells to dihydroteleocidin B and the phorbol ester tumor promoters: relation to adipocyte differentiation, DNA synthesis and cell division.

We have recently shown that an indole alkaloid tumor promoter, dihydroteleocidin B (DHTB) is significantly different from the phorbol ester tumor promoters such as 12-O-tetradecanoylphorbol-13-acetate (TPA) in its potency and mode of inhibiting the adipocyte differentiation of 3T3-L1 cells (1). DHTB almost completely inhibited the differentiation induced by dexamethasone (DEX) and 1-methyl-3-isobutylxanthine (MIX) regardless of when the tumor promoter was added: before, during, or after the addition of inducers. Similar inhibition was observed by TPA with over 90% less efficiency and only when it was added during the inducer treatment. Both DHTB and TPA stimulated DNA synthesis to the same level during the initial 22 hr. The DNA synthesis of resting 3T3-L1 cells triggered by DHTB resulted in cell division, whereas TPA-stimulated DNA synthesis did not facilitate cell division. This observation is in sharp contrast to the previous findings that both DHTB and TPA stimulate a number of growth-arrested fibroblasts (2), including Swiss/3T3 from which 3T3-L1 cells were derived, to initiate DNA synthesis and undergo cell division (3). In order to further clarify this point we attempted to isolate cell variants which were no longer responsive to the mitogenic action of DHTB. Among 14 variant lines isolated, we found two stable variant lines, 1-2 and 2-3, whose DNA synthesis was not initiated by DHTB. DNA synthesis of another variant line, 3-4, was stimulated by DHTB but not followed by cell division. From these findings it is proposed that the modes of action of DHTB and TPA are similar in triggering DNA synthesis of G1-arrested 3T3-L1 cells, but DHTB can further act on 3T3-L1 cells at a point during or after S phase to stimulate events of mitosis.

Adipose Tissue↗
PubMed1983

Increase in frequency of appearance of cadmium-resistant cells induced by various tumor promoters; evidence for the induction of gene amplification.

When Chinese hamster lung (CHL) cells were cultured in medium containing 25 microM cadmium chloride, resistant cells appeared at a frequency of 0.04%. When one of three tumor promoters, 12-O-tetradecanoylphorbol-13-acetate (TPA), aplysiatoxin and dihydroteleocidin B, was added during selection with cadmium chloride, the frequency of appearance of resistant cells increased more than 50-fold. Two of the resistant clones obtained were characterized. Both clones produced much higher levels of metallothionein I mRNA than the parental CHL cells. Southern blot analysis showed that in these resistant cells, metallothionein I genes were amplified approximately 5-fold. Therefore, it seems that tumor promoters can enhance the frequency of gene amplification. One possible mechanism of the action of tumor promoters in oncogenesis is amplification of activated c-onc genes. Consistent with this idea, it has been reported that c-onc genes are amplified in various cancer cells. We also found that the c-Ha-ras and c-myc genes were amplified in a bladder cancer removed surgically and in a transplanted rat hepatocellular carcinoma, Morris hepatoma 7794A, respectively.

Animals↗
PubMed1983

Tumor promoter-dependent mouse leukemia cell line.

From a spontaneous AKR/Ms thymic leukemia symbiotically cultured with thymic epithelial reticular cells, a tumor promoter-dependent cell line A65T was established by passaging the cells in medium containing 12-O-tetradecanoylphorbol-13-acetate (10 ng/ml). The in vitro growth of A65T was strictly dependent on the presence of active tumor promoters. Their action was reversible, since withdrawal of 12-O-tetradecanoylphorbol-13-acetate resulted in rapid decrease in viability of the cells. Three classes of chemically unrelated compounds sharing tumor-promoting activity in mouse skin could support the in vitro growth of A65T: plant diterpene esters; indole alkaloids; and polyacetates. Their growth effect on A65T cells quantitatively correlated well with the tumor-promoting activity in mouse skin. However, other growth stimulators of epidermal cells such as cholera toxin and epidermal growth factor failed to support the growth of A65T. It is suggested that lymphokines such as interleukin-2 and interleukin-3 were not responsible for 12-O-tetradecanoylphorbol-13-acetate-stimulated growth of A65T because concanavalin A-stimulated spleen cell-conditioned medium containing both interleukin-2 and interleukin-3 activities as well as WEHI-3 cell culture supernatant containing potent interleukin-3 activity did not stimulate the proliferation of A65T cells. Furthermore, 12-O-tetradecanoylphorbol-13-acetate did not induce production of any significant amount of either activity in A65T cells. This cell line is useful for the screening of tumor promoters in environments although, so far, all the compounds capable of stimulating A65T growth have been limited to those competing with phorbol esters for the cellular receptor. Also, the cell line provides a potential model for analyzing growth requirements of developing mouse thymic leukemias.

Acetates↗
PubMed1982

A new tumor-promoting agent, dihydroteleocidin B, markedly enhances chemically induced malignant cell transformation.

Teleocidin, which was isolated from mycelia of Streptomyces, is a potent tumor promoter in mouse skin. The catalytically hydrogenated compound dihydroteleocidin B markedly enhanced malignant cell transformation induced by 3-methylcholanthrene or ultraviolet radiation. Dihydroteleocidin B was at least 100 times more effective in enhancing transformation than 12-O-tetradecanoyl phorbol-13-acetate, the strongest promoter known until now, whereas both promoters showed equal capacities to induce early membrane effects and DNA synthesis.

Alkaloids↗
PubMed1982

Induction of supermelanin synthesis and morphological changes in interspecific reconstituted cells and its reversal by tumor promoter.

Chloramphenicol-resistant (CAPr) reconstituted cells and cybrids were isolated by fusion of karyoplasts (or intact cells) of mouse amelanotic melanoma B16 cells with cytoplasts of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) -deficient, CAPr rat myoblastic cells, L6TG.CAPr, and double selection in HAT medium containing CAP. Reconstituted cells or cybrids exhibited unique cellular arrangement, and about one third of the isolated clones expressed high tyrosinase activity and marked melanin synthesis, although the parental mouse cells expressed low tyrosinase activity and the parental rat cells did not express tyrosinase activity. These phenotypic changes have been stable for more than a year. The phenotypic reversions of these clonal cells were induced by treatment with a tumor promoter. There were changes in the morphology of the treated cells to that of the mouse B16 cells and extinction of tyrosinase activity and melanin synthesis in pigmented clonal cells. These phenotypic changes and reversions induced by a promoter were repeatedly reversible.

Animals↗
PubMed1982

Teleocidin from Streptomyces is a potent promoter of mouse skin carcinogenesis.

Teleocidin, isolated from Streptomyces mediocidicus ISP 5021, is an indole alkaloid. The teleocidin used was composed of teleocidin A, teleocidin B and their isomers. A hydrogenated derivative of teleocidin B, dihydroteleocidin B, was recently reported to have tumor promoting activity in vivo and various biological activities in vitro, with a specific activity comparable to that of 12-O-tetradecanoylphorbol-13-acetate (TPA). This paper describes the potent tumor promoting activity of the parent compound of dihydroteleocidins, teleocidin, on mouse skin in two-stage carcinogenesis. The tumor promoting activity was evaluated by measuring the incidence and yield of tumors, and by histological examination. Groups of mice were given a single application of 100 micrograms of 7,12-dimethylbenz[a]anthracene (DMBA) and then 2.5 micrograms of teleocidin twice weekly or the same dose of DMBA plus 2.5 micrograms of TPA twice weekly. Both groups showed 100% tumor incidence after 24 weeks, and the tumor yields were 4.0 tumors per mouse in the former group and 9.8 per mouse in the latter group in week 30. We confirmed, through this experiment, that teleocidin is as potent as TPA in in vivo two-stage carcinogenesis in mouse skin. These two structurally unrelated classes, indole alkaloid and phorbol ester, showed tumor promoting activity in almost the same range.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1982

Effects of teleocidin and the phorbol ester tumor promoters on cell transformation, differentiation, and phospholipid metabolism.

The potent tumor-promoting agent 12-O-tetradecanoylphorbol-13-acetate (TPA) and related diterpene phorbol esters have been shown to enhance viral transformation and anchorage-independent growth, inhibit differentiation, and stimulate phosphatidylcholine turnover in various cell culture systems. In the present study, we report that teleocidin, and indole alkaloid isolated from Streptomyces, induces several biological effects similar to those of TPA in cell culture. Both TPA and teleocidin enhanced transformation of a clone of Fischer rat embryo cells (CREF) by a temperature-sensitive mutant of adenovirus type 5 (H5ts125); enhanced the cloning efficiency in agar of E11 cells, a clone of H5ts125-transformed Sprague-Dawley rat embryo cells; inhibited melanogenesis in murine B-16 melanoma cells; inhibited myogenesis in myoblast cultures established from normal human skeletal muscle; and stimulated choline release from prelabeled phospholipids of C3H10T 1/2 mouse cells. In general, TPA and teleocidin were equipotent in inducing these biological effects and were most active in the 3- to 10-ng/ml range, i.e., approximately 10(-8) to 10(-9) M. These studies provide further evidence that teleocidin represents a new class of tumor-promoting agents with properties similar to, if not identical with, those of the phorbol ester tumor promoters. These findings also suggest that cell culture systems can be used to identify new types of tumor-promoting agents in addition to the diterpene phorbol esters.

Adenoviruses, Human↗