Conjugated linoleic acid stimulates an anti-tumorigenic protein NAG-1 in an isomer specific manner

Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA.
Carcinogenesis (Impact Factor: 5.33). 06/2006; 27(5):972-81. DOI: 10.1093/carcin/bgi268
Source: PubMed


Conjugated linoleic acids (CLAs), naturally occurring fatty acids in ruminant food products, have anti-tumorigenic and pro-apoptotic properties in animal as well as in vitro models of cancer. However, the cellular mechanism has not been fully understood. NAG-1 (non-steroidal anti-inflammatory drug-activated gene-1) is induced by several dietary compounds and belongs to a TGF-beta superfamily gene associated with pro-apoptotic and anti-tumorigenic activities. The present study was performed to elucidate the molecular mechanism by which CLA stimulates anti-tumorigenic activity in human colorectal cancer (CRC) cells. The trans-10, cis-12-CLA (t10,c12-CLA) repressed cell proliferation and induced apoptosis, whereas linoleic acid or c9,t11-CLA showed no effect on cell proliferation and apoptosis. We also found that t10,c12-CLA induced the expression of a pro-apoptotic gene, NAG-1, in human CRC cells. Inhibition of NAG-1 expression by small interference RNA (siRNA) results in repression of t10,c12-CLA-induced apoptosis. Microarray analysis using t10,c12-CLA-treated HCT-116 cells revealed that activating transcription factor 3 (ATF3) was induced and its expression was confirmed by western analysis. The t10,c12-CLA treatment followed by the overexpression of ATF3 increased NAG-1 promoter activity in HCT-116 cells. We further provide the evidence that t10,c12-CLA inhibited the phosphorylation of AKT and the blockage of GSK-3 by siRNA abolished t10,c12-CLA-induced ATF3 and NAG-1 expression. The current study demonstrates that t10,c12-CLA stimulates ATF3/NAG-1 expression and subsequently induces apoptosis in an isomer specific manner. These effects may be through inhibition of AKT/GSK-3beta pathway in human CRC cells.

Download full-text


Available from: Seung Joon Baek
  • Source
    • "There are growing evidences that the ATF3 expression was repressed in normal cells but might be rapidly induced by various pathological stimuli [44,45]. Moreover, ATF3 expression plays an important role in apoptosis induced by a variety of anti-cancer compounds such as berberine [46], conjugated linoleic acid [47], curcumin [48] and 3,3′-diindolylmethane [49] in human colorectal cancer cells, which indicates that ATF3 could function as a pro-apoptotic mediator. We found that MRBE induced cell growth arrest and apoptosis, and activated ATF3 expression in the levels of mRNA and protein in SW480. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Root bark of mulberry (Morus alba L.) has been used in herbal medicine as anti-phlogistic, liver protective, kidney protective, hypotensive, diuretic, anti-cough and analgesic agent. However, the anti-cancer activity and the potential anti-cancer mechanisms of mulberry root bark have not been elucidated. We performed in vitro study to investigate whether mulberry root bark extract (MRBE) shows anti-inflammatory and anti-cancer activity. Methods In anti-inflammatory activity, NO was measured using the griess method. iNOS and proteins regulating NF-κB and ERK1/2 signaling were analyzed by Western blot. In anti-cancer activity, cell growth was measured by MTT assay. Cleaved PARP, ATF3 and cyclin D1 were analyzed by Western blot. Results In anti-inflammatory effect, MRBE blocked NO production via suppressing iNOS over-expression in LPS-stimulated RAW264.7 cells. In addition, MRBE inhibited NF-κB activation through p65 nuclear translocation via blocking IκB-α degradation and ERK1/2 activation via its hyper-phosphorylation. In anti-cancer activity, MRBE deos-dependently induced cell growth arrest and apoptosis in human colorectal cancer cells, SW480. MRBE treatment to SW480 cells activated ATF3 expression and down-regulated cyclin D1 level. We also observed that MRBE-induced ATF3 expression was dependent on ROS and GSK3β. Moreover, MRBE-induced cyclin D1 down-regulation was mediated from cyclin D1 proteasomal degradation, which was dependent on ROS. Conclusions These findings suggest that mulberry root bark exerts anti-inflammatory and anti-cancer activity.
    Full-text · Article · Jun 2014 · BMC Complementary and Alternative Medicine
  • Source
    • "Specifically, t10,c12-CLA has revealed a more efficient activity, respect to c9,t11-CLA isomer, in modulating apoptosis or cell cycle. In human prostatic carcinoma cells, t10,c12-CLA anticancer effect associates to decreased Bcl-2 and increased p21(WAF1/Cip1) mRNA levels [30] while in human colon or bladder cancer cells it was accompanied by the activation of ATF/NAG-1 [31] or Insulin Growth Factor signaling [32]. Moreover, it was reported that t10,c12-CLA was able to down-regulate Fatty Acid Synthase [33] or antioxidant defence systems [21,22,34] in different human cancer cells. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This study describes the investigation of the efficiency of conjugated linoleic acid (CLA) isomers in reducing cancer cells viability exploring the role of the oxidative stress and acylpeptide hydrolase (APEH)/proteasome mediated pathways on pro-apoptotic activity of the isomer trans10,cis12 (t10,c12)-CLA. The basal activity/expression levels of APEH and proteasome (β-5 subunit) were preliminarily measured in eight cancer cell lines and the functional relationship between these enzymes was clearly demonstrated through their strong positive correlation. t10,c12-CLA efficiently inhibited the activity of APEH and proteasome isoforms in cell-free assays and the negative correlation between cell viability and caspase 3 activity confirmed the pro-apoptotic role of this isomer. Finally, modulatory effects of t10,c12-CLA on cellular redox status (intracellular glutathione, mRNA levels of antioxidant/detoxifying enzymes activated through NF-E2-related factor 2, Nrf2, pathway) and on APEH/β-5 activity/expression levels, were investigated in A375 melanoma cells. Dose- and time-dependent variations of the considered parameters were established and the resulting pro-apoptotic effects were shown to be associated with an alteration of the redox status and a down-regulation of APEH/proteasome pathway. Therefore, our results support the idea that these events are involved in ROS-dependent apoptosis of t10,c12-CLA-treated A375 cells. The combined inhibition, triggered by t10,c12-CLA, via the modulation of APEH/proteasome and Nrf2 pathway for treating melanoma, is suggested as a subject for further in vivo studies.
    Full-text · Article · Nov 2013 · PLoS ONE
  • Source
    • "Park and coworkers studied the consumption of CLA on calcium absorption in mice and found that CLA may stimulate calcium absorption given that extra calcium (0.66%) in the diet improved CLA effects on bone mass in male mice (Park & Pariza 2008). In addition, CLA has also shown anticarcinogenic effects against several types of experimental cancer, including skin and breast cancer with unresolved mechanisms (Lee et al. 2006). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Numerous studies have found an association between the consumption of certain bioactive lipids and improved human health, e.g., the prevention, delay, or treatment of chronic and acute diseases, such as cancer, cardiovascular disease (CVD), osteoporosis, and immune disorders. In this review, we discuss food-based sources and potential beneficial attributes of major dietary bioactive lipids: polyunsaturated fatty acids; carotenoids; phytosterols and phytostanols; and fat-soluble vitamins. We summarize the various challenges associated with incorporating these bioactive lipids into foods and beverages, such as poor water solubility, high melting point, and low chemical stability. Finally, we propose several techniques that have been used to solve the challenges and integrate dietary bioactive lipids into foods for improved health. Expected final online publication date for the Annual Review of Food Science and Technology Volume 4 is February 28, 2013. Please see for revised estimates.
    Full-text · Article · Dec 2012 · Review of Food Science and Technology
Show more