Masashi Kuchide

Cancer chemopreventive agents, 4-phenylcoumarins from Calophyllum inophyllum

In a search for anti-tumor-promoting agents, we carried out a primary screening of ten 4-phenylcoumarins isolated from Calophyllum inophyllum L. (Guttiferae), by examining their possible inhibitory effects on Epstein--Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate in Raji cells. All of the compounds tested in this study showed inhibitory activity against EBV, without showing any cytotoxicity. Calocoumarin-A (5) showed more potent activity than any of the other compounds tested. Furthermore, calocoumarin-A (5) exhibited a marked inhibitory effect on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. The results of the present investigation indicate that some of these 4-phenylcoumarins might be valuable as potential cancer chemopreventive agents (anti-tumor-promoters).

Cancer chemopreventive activity of Achyranthes aspera leaves on Epstein-Barr virus activation and two-stage mouse skin carcinogenesis.

Achyranthes aspera leaves have been assessed for chemopreventive activity. The MeOH extract, alkaloid, non-alkaloid and saponin fractions exhibited significant inhibitory effects (concentration 100 microg) on the Epstein-Barr virus early antigen activation induced by the tumor promotor 12-O-tetradecanoylphorbol-13-acetate in Raji cells. In this in vitro assay the non-alkaloid fraction containing mainly non-polar compounds showed the most significant inhibitory activity (96.9%; 60% viability). In the in vivo two-stage mouse skin carcinogenesis test the total methanolic extract possessed a pronounced anticarcinogenic effect (76%). The present study suggests that A. aspera leaf extract and the non-alkaloid fraction are valuable antitumor promotors in carcinogenesis.

Chemopreventive effects of emodin and cassiamin B in mouse skin carcinogenesis

In continuation of our works of natural and synthetic products as cancer chemopreventive agents, we have examined emodin and cassiamin B, which were isolated from Cassia siamea. These compounds exhibited the remarkable anti-tumor promoting effect on two-stage carcinogenesis test of mouse skin tumors induced by 7,12-dimethylbenz[a]anthracene as an initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as a promoter by both topical application. Furthermore, emodin exhibited potent inhibitory activity on two-stage carcinogenesis test of mouse skin tumors induced by nitric oxide donor, (+/-)-(E)-methyl-2-[(E)-hydroxyimino]-5-nitro-6-methoxy-3-hexeneamide as an initiator and TPA as a promoter.

Anti-tumor-promoting effects of glycoglycerolipid analogues on two-stage mouse skin carcinogenesis.

Four glycoglycerolipid analogues, 1-O-hexanoyl-2-O-beta-D-glucopyranosyl-sn-glycerol (1), 1-O-hexanoyl-2-O-beta-D-galactopyranosyl-sn-glycerol (2), 2-O-(6-O-hexanoyl-beta-D-galactopyranosyl)-sn-glycerol (3) and 2-O-(6-O-hexanoyl-alpha-D-galactopyranosyl)-sn-glycerol (4), potent in vitro inhibitors of 12-O-tetradecanoylphorbol-13-acetate (TPA) induced Epstein-Barr virus early antigen (EBV-EA) activation, were submitted to an in vivo two-stage mouse skin carcinogenesis test, using dimethylbenz[a]anthracene (DMBA) and TPA. The study was extended to two deacylated galactosylglycerol structures, 1-O-beta-D-galactopyranosyl-sn-glycerol (5) and 3-O-beta-D-galactopyranosyl-sn-glycerol (6). All the tested compounds exhibited remarkable anti-tumor-promoting effects on mouse skin tumor promotion, the 1-hexanoate 2 being the most active among the glycoglycerolipids until now studied.

Inhibitory effect of stabilized analogues of glycoglycerolipids on Epstein–Barr virus activation and mouse skin tumor promotion

Nine new synthetic compounds, structurally related to the most active glycoglycerolipid analogues carrying a hexanoyl chain, were tested for their anti-tumor-promoting activity using a short-term in vitro assay for Epstein-Barr virus (EBV) activation. All these compounds, in which the ester function is replaced by different metabolically more stable groups, were almost as active as their ester reference compounds in inhibiting the EBV activation promoted by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Two of these, devoid of any functionality on the lipophilic chain, when tested in an in vivo two-stage carcinogenesis test, exhibited marked inhibitory effects on mouse skin tumor promotion.

Cancer chemopreventive effects of oral feeding α-tocopherol on ultraviolet light B induced photocarcinogenesis of hairless mouse

Ultraviolet light is the most common cause of skin cancers in humans and several effects of ultraviolet light B (UVB: 290-320 nm) are thought to contribute to skin photocarcinogenesis. The generation of free radicals and related oxidants produced by UVB exposure, result in photocarcinogenesis by directly damaging DNA. On the other side, activating of transcription factor, activator protein 1 (AP-1) induced by UVB exposure causes tumor promotion. alpha-tocopherol has two principal physiological activities and one is an antioxidant activity through which alpha-tocopherol protects unsaturated fatty acids, protein and DNA from oxidation. The other activity is to stabilize the structure of the biomembrane. In addition to these two activities, it has been recently established that alpha-tocopherol plays important roles in cell signal transduction. In course of these studies, we examined such effects of alpha-tocopherol on UVB induced skin photocarcinogenesis in hairless mice. These results indicate that oral feeding of alpha-tocopherol including diet exhibited a marked inhibitory effects on both tumor incidence and multiplicity in UVB induced mouse skin photocarcinogenesis.

The effect of rebamipide on Helicobacter pylori extract-mediated changes of gene expression in gastric epithelial cells

Background : Recent studies have shown that Helicobacter pylori affects intracellular signal transduction in host cells, leading to the activation of transcriptional factors and the induction of pro‐inflammatory cytokines. On the other hand, rebamipide, an anti‐gastritis and anti‐ulcer agent, could scavenge reactive oxygen species and reduce interleukin‐8 (IL‐8) expression in gastric epithelial cells induced by H. pylori‐stimulation through the attenuated activation of nuclear factor‐κB (NF‐κB).

Effects of bile acids and acidic exposure on IL-8 expression in human esophageal epithelial cells

exposed on the surface of remaining tissue Primary squamous oesophageal epithelial cells (Sq cells) were isolated by explant tissue culture of normal oesophageal nmcosa. These cells were subsequently propagated in a low Ca + + serum-free tissue culture maintenance medium Sq cells were allowed to adhere to the luminal basement membrane of either Sq BM orCLO BM. Sq cells cultured in this orientation are at an airdiqind interface, which allow prolderation, stratification and dift?rentiation in response to the high Ca + + medium and interaction with the ECM and basement membrane. Results: The model was cultured for three weeks and histology confirmed sqnamous epithelium colonises sqnamous BM Laminin, an abundant ECM component was characterised by immunohistochemical staining. Conclusions: Tile role of the basement membrane in CLO on Sq cell proliferation and diflerentiation can be examined using this model

Tumor initiating activity of Helicobacter pylori water extract on mouse skin carcinogenesis.

Helicobacter pylori (H. pylori) infection has been associated with gastric carcinogenesis, but responsible and detail mechanisms are insufficient by the absence of adequate data. To obtain direct evidence regarding the carcinogenicity of H. pylori, we investigated the initiating and promoting activity of H. pylori water extract (HPE) in two-stage mouse skin carcinogenesis model. HPE treatment, as an initiation, significantly enhanced tumor formation compared with control group. Moreover, HPE treatment increased production of 8-hydroxydeoxyguanosine in epidermal cells and HPE-initiated/TPA-promoted papillomas demonstrated a point mutation of the Ha-ras gene. These results suggest an initiating activity of HPE on two-stage mouse skin carcinogenesis.