Korean J Nutr.  2003 Apr;36(3):270-279.

Study of the Mechanism for the Growth Inhibitory Effects of Conjugated Linoleic Acid on Caco-2 Colon Cancer Cells

• Oh EJ
• Oh YS
• Lee HS
• Park HS
• Yoon JH

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.

Keyword

conjugated linoleic acid; colon cancer cells; insulin-like growth factor-II; insulin-like growth factor-binding proteins

MeSH Terms

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
Culture Media, Conditioned
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
RNA, Messenger