aurapten and Skin-Neoplasms

NF-kappaB is a survival signaling transcription factor complex involved in the malignant phenotype of many cancers, including squamous cell carcinomas (SCC). The citrus coumarin, auraptene (AUR), and the ethno-medicinal ginger (Alpinia galanga) phenylpropanoid, 1'-acetoxychavicol acetate (ACA), were previously shown to suppress 12-O-tetradecanoylphorbol-13-acetate (TPA) induced mouse skin tumor promotion. The goal of the present study was to determine whether AUR and ACA are effective either alone or in combination with all-trans retinoic acid (ATRA) for suppressing SCC tumor growth.. We first determined the effects of orally administered ACA (100 mg/kg bw) and AUR (200 mg/kg bw) on lipopolysaccharide (LPS)-induced NF-kappaB activation in NF-kappaB-RE-luc (Oslo) luciferase reporter mice. Dietary administration of AUR and ACA +/- ATRA was next evaluated in a xenograft mouse model. Female SCID/bg mice were fed diets containing the experimental compounds, injected with 1 x 106 SRB12-p9 cells s.c., palpated and weighed twice a week for 28 days following injection.. Both ACA and AUR suppressed LPS-induced NF-kappaB activation in the report mice. In the xenograft model, AUR (1000 ppm) and ACA (500 ppm) modestly suppressed tumor volume. However, in combination with ATRA at 5, 10, and 30 ppm, ACA 500 ppm significantly inhibited tumor volume by 56%, 62%, and 98%, respectively. The effect of ATRA alone was 37%, 33%, and 93% inhibition, respectively. AUR 1000 ppm and ATRA 10 ppm were not very effective when administered alone, but when combined, strongly suppressed tumor volume by 84%.. Citrus AUR may synergize the tumor suppressive effects of ATRA, while ACA may prolong the inhibitory effects of ATRA. Further studies will be necessary to determine whether these combinations may be useful in the control of human SCC.

Topics: Animals; Antineoplastic Agents; Benzyl Alcohols; Blotting, Western; Carcinoma, Squamous Cell; Citrus; Coumarins; Drug Synergism; Drug Therapy, Combination; Female; Humans; Lipopolysaccharides; Luciferases; Male; Mice; Mice, SCID; NF-kappa B; Plant Extracts; Skin Neoplasms; Tretinoin; Tumor Cells, Cultured; Xenograft Model Antitumor Assays; Zingiber officinale

Auraptene (AUR), a citrus coumarin derivative, is one of the promising chemopreventive agents against skin, tongue, esophagus and colon carcinogenesis in rodents. We reported previously that AUR suppresses superoxide anion (O(2)(-)) generation from inflammatory leukocytes in in vitro experiments. In the present study, we investigated the anti-inflammatory activities of AUR using a 12-O:-tetradecanoylphorbol-13-acetate-treated mouse skin model, and compared them with those of umbelliferone (UMB), a structural analog of AUR that is virtually inactive toward O(2-) generation inhibition. Double pre-treatments of mouse skin with AUR, but not UMB, markedly suppressed edema formation, hydrogen peroxide production, leukocyte infiltration, and the rate of proliferating cell nuclear antigen-stained cells. These inhibitory effects by AUR are attributable to its selective blockade of the activation stage, as revealed by single pre-treatment experiments. In a murine macrophage line, RAW 264.7, AUR significantly attenuated the lipopolysaccharide-induced protein expression of inducible isoforms of both nitric oxide synthase and cyclooxygenase, with decreased production of nitrite anion and prostaglandin E(2), and yet suppressed the release of tumor necrosis factor-alpha. Conversely, UMB did not show any inhibitory effect. This contrasting activity profile between AUR and UMB was rationalized to be a result of their distinct differences in cellular uptake efficiencies, i.e. the geranyloxyl group in AUR was found to play an essential role in incorporation. Thus, our findings indicate that AUR is an effective agent to attenuate the biochemical responsiveness of inflammatory leukocytes, which may be essential for a greater understanding of the action mechanism that underlies its inhibition of inflammation-associated carcinogenesis.

Topics: Animals; Anticarcinogenic Agents; Carcinogens; Cell Division; Coumarins; Cyclooxygenase 2; Dermatitis, Contact; Edema; Female; Hydrogen Peroxide; Isoenzymes; Leukocytes; Lipopolysaccharides; Macrophage Activation; Macrophages; Mice; Mice, Inbred ICR; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Prostaglandin-Endoperoxide Synthases; Skin; Skin Neoplasms; Superoxides; Tetradecanoylphorbol Acetate; Tumor Necrosis Factor-alpha; Umbelliferones

Coumarin-related compounds, auraptene and umbelliferone, have been isolated from the cold-pressed oil of natsumikan (Citrus natsudaidai HAYATA), and tested as inhibitors of tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced Epstein-Barr virus activation in Raji cells. The 50% inhibitory concentration (IC50) of auraptene (18 microM) was almost equal to that of genistein. Umbelliferone, which lacks a geranyloxyl group present in auraptene, was less active (IC50 = 450 microM). In a two-stage carcinogenesis experiment with 7,12-dimethylbenz[a] anthracene (topical application at 0.19 mumol) and TPA (topical application at 1.6 nmol) in ICR mouse skin, topical application of auraptene (at 160 nmol) significantly reduced tumor incidence and the numbers of tumors per mouse by 27% (P < 0.01) and 23% (P < 0.05), respectively. Auraptene at a concentration of 50 microM markedly suppressed superoxide (O2-) generation induced by 100 microM TPA in differentiated human promyelocytic HL-60 cells. Having no O2(-)-scavenging potential, auraptene may inhibit the multicomponent NADPH oxidase system. Inhibition of intracellular hydroperoxide formation in differentiated HL-60 cells by auraptene was also confirmed by flow-cytometric analysis using 2',7'-dichlorofluorescein diacetate as a fluorescence probe. Quantitative analyses using high-performance liquid chromatography showed the occurrence of auraptene not only in both the peels and sarcocarps of natsumikan, but also in those of hassaku orange (C. hassaku) and grapefruit (C. paradisi), and even in their bottled fresh juice form. These results indicate that auraptene is a chemopreventer of skin tumorigenesis, and implies that suppression of leukocyte activation might be the mechanism through which it inhibits tumor promotion.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Anticarcinogenic Agents; Carcinogens; Cell Line; Citrus; Coumarins; Female; Flow Cytometry; Fluorescent Dyes; Humans; Leukemia, Promyelocytic, Acute; Leukocytes; Mice; Mice, Inbred ICR; Skin Neoplasms; Superoxides; Tetradecanoylphorbol Acetate; Umbelliferones