IGF-independent effects of IGFBP-2 on the human breast cancer cell line Hs578T.
There is evidence that insulin-like growth factor-binding protein (IGFBP-2), a modulator of the actions of IGFs, also has IGF-independent effects in human tumor cell lines. These involve specific binding of IGFBP-2 to alpha5beta1-integrin, followed by alterations in the phosphorylation status of downstream signaling molecules. Previously, IGFBP-2 has also been shown to be associated with cell proliferation, adhesion and migration. Here, we investigated direct effects of IGFBP-2 on apoptosis and alterations in the expression of related proteins. The breast cancer cell line Hs578T, which shows no IGFBP-2 production of its own and is independent of the IGF-I receptor, was treated with human recombinant IGFBP-2 in order to study the changes in gene expression induced by IGFBP-2. The methods employed for this purpose were oligonucleotide microarrays, real-time RT-PCR, western blotting, and immunoassays. Out of the 440 genes covered by the Oligo GEArray Human Cancer Microarray OHS-802, the expression of 77 genes was directly influenced by IGFBP-2. By the use of real-time quantitative RT-PCR, the gene expression of Nuclear Factor (NF)kappaB, p53, transforming growth factor beta (TGF beta-1), LAMB1 (Laminin, Beta 1), Bcl-2, and IIp45 was found to be significantly upregulated (by 1.2- to 3.05-fold; all P < 0.001). Accordingly, NFkappaB, p53, and TGF beta-1 proteins, as measured by Western blotting and immunoassay, were upregulated > 1.5-fold. By using an ELISA-based and a flow cytometry-based apoptosis assay, IGFBP-2 was found to have a pro-apoptotic effect on Hs578T cells. Our results suggest that IGFBP-2-induced gene expressions are of functional significance for proliferation, cell adhesion, cell migration and apoptosis, and showed that IGFBP-2 can promote apoptosis in tumor cells independent of IGF.
Frommer
Klaus W
KW
Pediatric Endocrinology Section, University Children's Hospital, 72076 Tuebingen, Germany.
Reichenmiller
Katharina
K
Schutt
Burkhardt S
BS
Hoeflich
Andreas
A
Ranke
Michael B
MB
Dodt
Gabriele
G
Elmlinger
Martin W
MW
D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001943:Breast Neoplasms / Q000378:metabolism*; D002448:Cell Adhesion / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D013002:Somatomedins / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
D018971:Insulin-Like Growth Factor Binding Protein 2; D016328:NF-kappa B; D013002:Somatomedins; D053773:Transforming Growth Factor beta1; D016159:Tumor Suppressor Protein p53