Study of the Mechanism for the Growth Inhibitory Effects of Conjugated Linoleic Acid on Caco-2 Colon Cancer Cells.
- Author:
Eun Ji OH
1
;
Yoon Sin OH
;
Hyun Sook LEE
;
Hyun Suh PARK
;
Jung Han YOON
Author Information
1. Silver Biotechnology Research Center, Hallym University, Chunchon, Korea.
- Publication Type:Original Article
- Keywords:
conjugated linoleic acid;
colon cancer cells;
insulin-like growth factor-II;
insulin-like growth factor-binding proteins
- MeSH:
Adenocarcinoma;
Blotting, Northern;
Caco-2 Cells;
Cell Line;
Colon*;
Colonic Neoplasms*;
Culture Media, Conditioned;
Humans;
Insulin-Like Growth Factor Binding Protein 2;
Insulin-Like Growth Factor Binding Protein 4;
Insulin-Like Growth Factor Binding Proteins;
Insulin-Like Growth Factor II;
Linoleic Acid*;
Models, Animal;
RNA, Messenger
- From:The Korean Journal of Nutrition
2003;36(3):270-279
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
Conjugated linoleic acid (CLA) is a group of positional and geometric isomers of linoleic acid (LA) and exhibits anticarcinogenic activity in a variety of animal models. We have previously observed that CLA inhibited the growth of Caco-2 cells, a human colon adenocarcinoma cell line. The present study was performed to determine whether the growth inhibitory effect of CLA is related to change in secretion of IGF- II and/or IGF-binding proteins (IGFBPs) that have been shown to regulate Caco-2 cell proliferation by an autocrine mechanism. Cells were incubated in serum-free medium with various concentrations of CLA or linoleic acid (LA). Immunoblot analysis of 24-hours, serum-free, conditioned medium using a monoclonal anti-IGF-IIantibody revealed that Caco-2 cells secreted both mature 6,500 Mr and higher Mr forms of pro IGF-II. The levels of pro IGF-II and mature IGF-IIwere decreased by 43+/-2% and 53+/-6%, respectively by treatment with 50 micrometer CLA. LA slightly increased pro IGF- II levels. Results from Northern blot analysis showed that CLA decreased IGF-II mRNA levels at 50 micrometer concentration suggesting that CLA regulation of IGF-II protein expression occurs partly at the transcriptional level. Ligand blot analysis of conditioned media using 1251-IGF-II revealed that CLA slightly decreased IGFBP-2 levels and increased IGFBP-4 levels. We confirmed our previous results that CLA inhibited cell growth in a dose-dependent manner but LA slightly increased cell growth. Exogenous IGF-II mitigated the growth inhibitory effect of CLA. These results indicate that the growth inhibitory effect of CLA may be at least in part mediated by decreasing IGF-II and IGFBP-2 secretion and increasing IGFBP-4 secretion in Caco-2 cells.
