Epidemiological, clinical, and laboratory studies have implicated that ultraviolet radiation (UV) is a complete environmental carcinogen and that repeated exposures can lead to the development of melanoma and nonmelanoma skin cancers. In addition to sunscreens, chemoprevention of skin cancer by natural non-toxic compounds is suggested as an effective strategy to prevent the incidence of skin cancer. Our in vitro and in vivo studies on cyanidin-3-glucoside (C3G), a compound found in blackberries and other foods, show that this compound is able to inhibit NF-:B, AP-1, COX2, and TNF1 activation/expression, neoplastic transformation, cancer cell migration and invasion, and induction of apoptosis in HL60 cells. C3G also functions as an antioxidant by inhibiting the generation of reactive oxygen species and inducing antioxidant-regulative transcription factors. These preliminary studies indicate that C3G may function as a potential chemopreventive and chemotherapeutic agent. The overall hypothesis of this application is that C3G functions as an antioxidant and inhibits oxidative stress, activation of transcription factors, and inflammatory signaling proteins, leading to protection against UVB-induced carcinogenesis.
Specific Aim 1. In vitro and in vivo investigation of antioxidant properties of C3G. Electron spin resonance (ESR) spin trapping will be used to determine the reaction rates of C3G toward hydroxyl (7OH) and superoxide (O27-) radicals, using Fenton reaction (Fe(II) + H2O2) and xanthine/xanthine oxidase as sources of these free radicals in a non-cellular system, and to investigate antioxidant activities against UVB-induced 7OH and O27- radicals in a cellular system. Low frequency (in vivo) ESR will be also used to study antioxidant activities of C3G against UVB-generated O27- and 7OH radicals in the skin of SKH-1 hairless mice.
Specific Aim 2. In vivo investigation of the effects of C3G on UVB-induced oxidative stress and activation of oxidative stress sensitive transcription factors. We will investigate the effects of C3G on UVB-induced lipid peroxidation, protein oxidation, and oxidative DNA damage in KSH mice. We will also study the effects of C3G on UVB-induced activation of activation protein (AP)-1, nuclear factor (NF)-:B, and nuclear factor of activated T cells (NAFT) in transgenic mice.
Specific Aim 3. Investigate the effects of C3G on UVB-induced inflammatory mediators. These inflammatory mediators include infiltrating leukocytes and myeloperoxidase (MPO), COX-2, PGE2, and several pro-inflammatory cytokines, TNF-1, IL-2, and IL-6.
Specific Aim 4. Investigation of the effects of C3G on UVB-induced tumorigenesis and early biomarkers. These markers include changes in thymine-positive cells, proliferative cell nuclear antigen, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and apoptotic cells together with a change in p53 and p21/cip1- positive cell population in epidermis. These studies will provide a mechanistic rationale for an early on C3G efficacy in skin cancer prevention.
The incidence of UV-induced skin cancer is a major public health concern. Present study attempts to identify cyanidin-3-glucoside, a plant-derived compound, as a mechanism-based preventive agent against UV-induced skin cancers.
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