Inhibition of Caco-2 cell proliferation by all-trans retinoic acid: role of insulin-like growth factor binding protein-6.

Abstract

The present study examined the effects of all-trans retinoic acid (tRA) on proliferation and expression of the IGF system in Caco-2 human colon adenocarcinoma cells. tRA inhibited Caco-2 cell proliferation in a dose-dependent manner, with a 40 +/- 2% decrease in cell number observed 48 h after the addition of 1 microM tRA. Ligand blot analysis of IGFBPs in conditioned media revealed that Caco-2 cells produced three IGFBPs of M(r): 34,000 (IGFBP-2), 24,000 (IGFBP-4), and 32,000 (IGFBP-6). The concentrations of IGFBP-2 and IGFBP-4 decreased by 48 +/- 6 and 70 +/- 13%, respectively, whereas that of IGFBP-6 increased by 698 +/- 20% with 1 microM tRA. tRA decreased mRNA levels of IGFBP-2 and IGFBP-4 by 20 +/- 3 and 50 +/- 8%, respectively, whereas tRA increased IGFBP-6 mRNA by 660 +/- 20%. tRA did not alter levels of IGF-II mRNA or peptide. To examine if endogenous IGFBP-6 inhibits cell proliferation, Caco-2 cells were transfected with an IGFBP-6 cDNA expression construct or pcDNA3 vector only and stable clones were selected. Clones overexpressing IGFBP-6 grew more slowly than vector controls and achieved final densities 30-55% lower than those of vector controls. Accumulation of IGFBP-6 mRNA and concentrations of IGFBP-6 peptide in conditioned media were increased by 200-250 and 220-250%, respectively, in the IGFBP-6 clones compared with controls. Increased expression of IGFBP-6, which has a high binding affinity for IGF-II, following tRA treatment suggests that the decreased proliferation caused by tRA may result, at least in part, from IGFBP-6-mediated disruption of the IGF-II autocrine loop in these colon cancer cells.

• Authors: Eun J Kim, Young-Hee Kang, Beverly S Schaffer, Leon A Bach, Richard G MacDonald, Jung H Y Park
• Journal: Journal of cellular physiology (J Cell Physiol) Vol. 190 Issue 1 Pg. 92-100 (Jan 2002) ISSN: 0021-9541 [Print] United States
• PMID: 11807815 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright 2002 Wiley-Liss, Inc.

Chemical References

• Culture Media, Conditioned
• Culture Media, Serum-Free
• Insulin-Like Growth Factor Binding Protein 2
• Insulin-Like Growth Factor Binding Protein 4
• Insulin-Like Growth Factor Binding Protein 6
• RNA, Messenger
• Tretinoin
• Insulin-Like Growth Factor II

Topics

• Caco-2 Cells (cytology, drug effects, metabolism)
• Cell Count
• Cell Division (drug effects)
• Cell Line
• Culture Media, Conditioned (chemistry, metabolism)
• Culture Media, Serum-Free (pharmacology)
• Dose-Response Relationship, Drug
• Humans
• Immunoblotting
• Insulin-Like Growth Factor Binding Protein 2 (genetics, metabolism)
• Insulin-Like Growth Factor Binding Protein 4 (genetics, metabolism)
• Insulin-Like Growth Factor Binding Protein 6 (genetics, metabolism)
• Insulin-Like Growth Factor II
• Molecular Weight
• RNA, Messenger (metabolism)
• Time Factors
• Transfection
• Tretinoin (pharmacology)