IGFBP-1 inhibits EGF mitogenic activity in cultured endometrial stromal cells

The properties of the insulin-like growth factor-binding proteins (IGFBP-1 to 6) are not limited to modulation of IGF actions. IGFBP-1, which shares an Arg-Gly-Asp (RGD) motif in its C-terminal domain, modulates cell motility by binding to integrin alpha5beta1. The cross-talks between integrins and growth factor receptor signalling pathways are extensively documented, particularly in the case of the epidermal growth factor receptor (EGFR). However, whether IGFBP-1 can modulate growth factor signalling through its interaction with integrin alpha5beta1 has not yet been studied. As EGF is involved in the decidualisation of endometrial stromal cells (ESCs) and as decidualised ESCs are a source of IGFBP-1, we investigated if IGFBP-1 can modulate EGF effects on ESCs. RGD- and IGF-independent inhibition of EGF mitogenic activity and EGFR signalling by IGFBP-1 were demonstrated in ESC primary cultures, A431, cells and in mouse fibroblasts lacking IGF receptors.