Transcriptome analysis of a human colorectal cancer cell line shows molecular targets of insulin-like growth factor-binding protein-4 overexpression.

Insulin-like growth factor II (IGF-II) is expressed commonly in colorectal tumors. IGF-binding protein-4 (IGFBP-4) counteracts the tumor promoting activities of IGF-II by binding this growth factor. We have shown previously that in LS1034 cells, which highly express IGF-II, overexpression of IGFBP-4 led to a strong reduction in proliferation, colony formation and invasive capacity. To investigate the effects of IGFBP-4 at the molecular level we analyzed growth parameters of LS1034 human colon cancer cells vs. cells expressing the murine IGFBP-4 (mIGFBP-4) and used a subtractive cDNA library approach in combination with cDNA array hybridization to detect changes in the mRNA expression profiles. The mRNA levels for several proteins that are known to affect important biological properties of neoplastic cells, such as proteolysis, proliferation and differentiation were altered by overexpression of IGFBP-4. Transcript levels for tumor markers, like the carcinoembryonic antigen-related cell adhesion molecule (CEACAM), were reduced by elevated mIGFBP-4. Changes at the mRNA level were confirmed by Western blotting for CST1 (proteolysis or protease inhibitor), COX-2 (cell motility) and CEACAM5 (tumor marker). Furthermore, the effect of mIGFBP-4 on apoptosis was investigated and no increase of apoptosis could be detected in the IGFBP-4 overexpressing LS1034 cells. Our data indicate that IGFBP-4 is involved in the regulation of gene products that are known or supposed to be important for the pathogenesis of colon cancer cells.