Abstract
Insulin-like growth factor-I (IGF-I), its receptor and its binding proteins are expressed by ovarian cancer cells. In this study, we examined oestradiol (E 2) regulation of IGF-I and IGF binding proteins (IGFBP) in an oestrogen-responsive ovarian cancer cell line, PE04. In serum-free conditions, PE04 cell monolayer growth was increased 1.64-fold by 3 nmol/l E 2 compared with controls, although IGF-I mRNA levels were not increased. In contrast to IGF-I mRNA, IGFBP mRNA was regulated by E 2. E 2 caused a marked decrease in IGFBP-3 RNA, but IGFBP-2, -4 and -6 levels were only minimally depressed. IGFBP-5 mRNA levels were increased by E 2. Tamoxifen had less effect on IGFBP mRNA regulation. Ligand blotting showed that E 2 reduced IGFBP levels in conditioned media. IGFBP RNA was also detected in human ovarian tissue samples. Thus, IGFBP expression can be regulated in oestrogen-responsive ovarian cancer by E 2.
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