Browsing by Author "Chen, Chin-Yu"

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5-Demethyltangeretin is more potent than tangeretin in inhibiting dimethylbenz(a)anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin tumorigenesis
(2014-11-01)
Ma, Nianhan
;
Lai, Ching-Shu
;
Chung, Chih-Han
;
Yang, Jinn-Moon
;
Hsu, Kai-Cheng
5-Demethyltangeretin (5-DTAN), an autohydrolysis product of tangeretin (TAN) found in citrus peel, exhibited more potent anti-proliferative activity in human cancer cells than TAN itself. In this study, we investigated the anti-tumor promoting effect and underlying molecular mechanism of 5-DTAN on 7,12-dimethyl-benz(a)anthracene (DMBA)-induced and 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted skin carcinogenesis. Application of 5-DTAN prior to each TPA-treatment was more effective than that of TAN on reducing the number, incidence and size of papillomas in DMBA-initiated mouse skin. Moreover, 5-DTAN suppressed cyclooxygenase-2 (COX-2) protein expression more strongly than TAN through interfering with phosphatidylinositiol 3-kinase (PI3K)/Akt signaling and further activation of transcription factor NF-kappa B. Taken together, these results revealed for the first time the in vivo chemopreventive efficacy of 5-DTAN on inhibition of skin carcinogenesis through promoting apoptosis and molecular interactions with residues of PI3K, COX-2, and AKT that may potentially serve as a novel functional agent capable of preventing inflammation-associated tumorigenesis. (C) 2014 Elsevier Ltd. All rights reserved.
Optical properties associated with strain relaxations in thick InGaN epitaxial films
(2014-03-10)
Tsai, Wen-Che
;
Hsu, Chia-He
;
Fu, Shao-Fu
;
Lee, Fang-Wei
;
Chen, Chin-Yu
Structural and optical properties of thick InGaN layers with strain and composition inhomogeneities are investigated. High resolution x-ray diffractions (XRD) and reciprocal space mapping (RSM) along an asymmetric axis reveal that the In composition inhomogeneity is accompanied by strain relaxations during the growth of thick InGaN layers. According to the structural analysis, the commonly observed double photoluminescence (PL) peaks have been confirmed to be associated with the strain relaxation in thick InGaN films. Temperature-dependent PL measurements further indicate that the relaxed phase in InGaN films exhibits better emission efficiency than the strained phase. Recombination dynamics reveal that the carrier localization effect is more pronounced in the relaxed phase due to the compositional pulling effect. The correlations between emission efficiency and localization effect in thick InGaN films are discussed. (C)2014 Optical Society of America