Hindawi Publishing Corporation Evidence-Based Complementary and Alternative Medicine Volume 2013, Article ID 429393, 12 pages http://dx.doi.org/10.1155/2013/429393 Research Article Antiproliferative Action of Conjugated Linoleic Acid on Human MCF-7 Breast Cancer Cells Mediated by Enhancement of Gap Junctional Intercellular Communication through Inactivation of NF-B Md. Abdur Rakib, 1,2 Won Sup Lee, 3 Gon Sup Kim, 4 Jae Hee Han, 5 Jeong Ok Kim, 6 and Yeong Lae Ha 1 1 Division of Applied Life Sciences (BK21 Plus), Graduate School, and Institute of Agriculture & Life Science, Gyeongsang National University, Jinju 660-701, Republic of Korea 2 Department of Biochemistry and Molecular Biology, Faculty of Science, University of Rajshahi, Rajshahi-6205, Bangladesh 3 Department of Internal Medicine and Institute of Health Sciences, Gyeongsang National University, School of Medicine, Jinju 660-702, Republic of Korea 4 Laboratory of Biochemistry (BK21 Plus), School of Veterinary Medicine, Gyeongsang National University, Jinju 660-701, Republic of Korea 5 Department of Physiology and Institute of Health Sciences, Gyeongsang National University, School of Medicine, Jinju 660-702, Republic of Korea 6 HK Biotech Co., Ltd., Jinju 660-844, Republic of Korea Correspondence should be addressed to Yeong Lae Ha; ylha@gnu.ac.kr Received 7 September 2013; Accepted 1 November 2013 Academic Editor: Shuang-En Chuang Copyright © 2013 Md. Abdur Rakib et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e major conjugated linoleic acid (CLA) isomers, c9,t11-CLA and t10,c12-CLA, have anticancer effects; however, the exact mechanisms underlying these effects are unknown. Evidence suggests that reversal of reduced gap junctional intercellular communication (GJIC) in cancer cells inhibits cell growth and induces cell death. Hence, we determined that CLA isomers enhance GJIC in human MCF-7 breast cancer cells and investigated the underlying molecular mechanisms. e CLA isomers significantly enhanced GJIC of MCF-7 cells at 40 M concentration, whereas CLA inhibited cell growth and induced caspase-dependent apoptosis. CLA increased connexin43 (Cx43) expression both at the transcriptional and translational levels. CLA inhibited nuclear factor-B (NF-B) activity and enhanced reactive oxygen species (ROS) generation. No significant difference was observed in the efficacy of c9,t11-CLA and t10,c12-CLA. ese results suggest that the anticancer effect of CLA is associated with upregulation of GJIC mediated by enhanced Cx43 expression through inactivation of NF-B and generation of ROS in MCF-7 cells. 1. Introduction Conjugated linoleic acid (CLA) is comprised of positional and geometric isomers of octadecadienoic acid (C18:2) with a conjugated double bond [1]. CLA has several health ben- efits in vivo, including anticarcinogenesis, antiatherogene- sis, antiobesity, and modulation of immune function [1–5]. Numerous anticancer and anticarcinogenic effects of CLA and individual CLA isomers have been reported. CLA inhibits 7,12-dimethylbenz[a]anthracene-induced mouse skin carcinogenesis, benzo(a)pyrene-induced mouse forestomach tumorigenesis, 2-amino-3,4-dimethylimidazo[4,5-f ] quino- line-induced rat colonic carcinogenesis, and N-methyl-N- nitrosourea-induced rat mammary carcinogenesis [1, 2, 6, 7]. Individual CLA isomers also show anticancer effects by inducing apoptosis in animals and cancer cell lines [7–9], but their mechanisms of action are still unknown. Gap junctions are transmembrane channels that con- nect the cytoplasm of neighboring cells composed of two hemichannels and each consists of six connexin proteins [10].