Expression of insulin-like growth factor-II and insulin-like growth factor binding proteins during Caco-2 cell proliferation and differentiation.
The components of the insulin-like growth factor (IGF) axis and their roles in regulating proliferation and differentiation of the human colon adenocarcinoma cell line, Caco-2, have been investigated. Caco-2 cells proliferated in serum-free medium at 75% the rate observed in medium containing 10% fetal bovine serum. IGF-I (10 nM) increased Caco-2 cell growth in serum-free medium, but not to the rate seen with serum. Multiple IGF-II mRNA species were produced by Caco-2 cells, but IGF-I mRNA was undetectable. Secretion of radioimmunoassayable IGF-II corresponded with steady-state levels of IGF-II mRNA, neither of which was observed to change markedly over the course of 16 days of Caco-2 cell differentiation. Levels of sucrase-isomaltase mRNA, a marker for enterocytic differentiation, increased 12-fold between days 5 and 16 of culture. Northern blotting of total RNA and ligand blot and immunoblot analyses of serum-free conditioned medium revealed that Caco-2 cells produce several IGF binding proteins (IGFBPs), including IGFBP-2, -3, and -4, as well as a 31,000 M(r) species that was not identified. The pattern of IGFBP secretion changed dramatically during Caco-2 cell differentiation: IGFBP-3 and IGFBP-2 increased 8.5-fold and 5-fold, respectively, whereas IGFBP-4 and the 31,000 M(r) species decreased 43% and 90%. Caco-2 cell clones stably transfected with a human IGFBP-4 cDNA construct exhibited a 60% increase in steady-state level of IGFBP-4 mRNA, and secreted twice as much IGFBP-4 protein as controls. Moreover, IGFBP-4-overexpressing cells proliferated at only 25% the rate of control cells in serum-free medium, in conjunction with a 70% increase in expression of sucrase-isomaltase. In summary, these studies indicate that a complex IGF axis is involved in autocrine regulation of Caco-2 cell proliferation and differentiation.
Park
J H
JH
Department of Pediatrics, Creighton University, Omaha, Nebraska, USA.
Corkins
M R
MR
Vanderhoof
J A
JA
Caruso
N M
NM
Hrbek
M J
MJ
Schaffer
B S
BS
Slentz
D H
DH
McCusker
R H
RH
MacDonald
R G
RG
D018938:Caco-2 Cells; D002454:Cell Differentiation; D002455:Cell Division; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000096:biosynthesis / Q000235:genetics; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis*; D007335:Insulin-Like Growth Factor II / Q000096:biosynthesis*; D007413:Intestinal Mucosa / Q000166:cytology* / Q000378:metabolism*; D009834:Oligo-1,6-Glucosidase / Q000378:metabolism; D011994:Recombinant Proteins; D013393:Sucrase / Q000378:metabolism; D014162:Transfection
D018076:DNA, Complementary; D018974:Insulin-Like Growth Factor Binding Protein 4; D018969:Insulin-Like Growth Factor Binding Proteins; D011994:Recombinant Proteins; D007335:Insulin-Like Growth Factor II; D009834:Oligo-1,6-Glucosidase; D013393:Sucrase