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

Eun J. Kim, Young Hee Kang, Beverly S. Schaffer, Leon A. Bach, Richard G. MacDonald, Jung H.Y. Park

Research output: Contribution to journalArticle

42 Scopus citations

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 μM tRA. Ligand blot analysis of IGFBPs in conditioned media revealed that Caco-2 cells produced three IGFBPs of Mr: 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 -M 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.

Original languageEnglish (US)
Pages (from-to)92-100
Number of pages9
JournalJournal of Cellular Physiology
Volume190
Issue number1
DOIs
StatePublished - Jan 1 2002

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Cell Biology

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