Carcinogenesis Advance Access originally published online on December 10, 2008
Carcinogenesis 2009 30(2):321-330; doi:10.1093/carcin/bgn282
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Caffeic acid, a phenolic phytochemical in coffee, directly inhibits Fyn kinase activity and UVB-induced COX-2 expression
1 The Hormel Institute, University of Minnesota, 801 16th Avenue NE, Austin, MN 55912, USA
2 Department of Agricultural Biotechnology and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-742, Republic of Korea
3 Department of Bioscience and Biotechnology
4 Department of Chemistry, Konkuk University, Seoul 143-701, Republic of Korea
* To whom correspondence should be addressed. Tel: +1 507 437 9600; Fax: +1 507 437 9606; Email: zgdong{at}hi.umn.edu
Correspondence may also be addressed to Hyong Joo Lee. Tel: +82 2 880 4860; Fax: +82 2 873 5095; Email: leehyjo{at}snu.ac.kr
Caffeic acid (3,4-dihydroxycinnamic acid) is a well-known phenolic phytochemical present in many foods, including coffee. Recent studies suggested that caffeic acid exerts anticarcinogenic effects, but little is known about the underlying molecular mechanisms and specific target proteins. In this study, we found that Fyn, one of the members of the non-receptor protein tyrosine kinase family, was required for ultraviolet (UV) B-induced cyclooxygenase-2 (COX-2) expression, and caffeic acid suppressed UVB-induced skin carcinogenesis by directly inhibiting Fyn kinase activity. Caffeic acid more effectively suppressed UVB-induced COX-2 expression and subsequent prostaglandin E2 production in JB6 P+ mouse skin epidermal (JB6 P+) cells compared with chlorogenic acid (5-O-caffeoylquinic acid), an ester of caffeic acid with quinic acid. Data also revealed that caffeic acid more effectively induced the downregulation of COX-2 expression at the transcriptional level mediated through the inhibition of activator protein-1 (AP-1) and nuclear factor-
B transcription activity compared with chlorogenic acid. Fyn kinase activity was suppressed more effectively by caffeic acid than by chlorogenic acid, and downstream mitogen-activated protein kinases (MAPKs) were subsequently blocked. Pharmacological Fyn kinase inhibitor (3-(4-chlorophenyl)1-(1,1-dimethylethyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine and leflunomide) data also revealed that Fyn is involved in UVB-induced COX-2 expression mediated through the phosphorylation of MAPKs in JB6 P+ cells. Pull-down assays revealed that caffeic acid directly bound with Fyn and non-competitively with adenosine triphosphate. In vivo data from mouse skin also supported the idea that caffeic acid suppressed UVB-induced COX-2 expression by blocking Fyn kinase activity. These results suggested that this compound could act as a potent chemopreventive agent against skin cancer.
Abbreviations: AP-1, activator protein-1; ATP, adenosine triphosphate; COX-2, cyclooxygenase-2; DTT, dithiothreitol; EDTA, ethylenediaminetetraacetic acid; ERK, extracellular signal-regulated kinase; FBS, fetal bovine serum; JNK, c-jun N-terminal kinase; MAPK, mitogen-activated protein kinase; MEM, minimum essential medium; NF-B, nuclear factor-B; PP2, (3-(4-chlorophenyl)1-(1,1-dimethylethyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine; PGE2, prostaglandin E2; PMSF, phenylmethylsulfonyl fluoride; SH, Src homology; UV, ultraviolet
These authors contributed equally to this work. Received September 20, 2008; revised December 1, 2008; accepted December 3, 2008.