Expression of the insulin-like growth factors (IGFs) and the IGF-binding proteins (IGFBPs) in human gastric cancer cells

Insulin-like growth factor (IGF)-I and -II are potent mitogens and postulated to exert autocrine, and paracrine effects on growth regulation in human gastric cancer. Their mitogenic effects are tightly regulated by the IGF binding proteins (IGFBPs). In this study, we evaluated the mRNA expression of IGF-I, IGF-II and the IGFBPs in a panel of human gastric cancer cell lines, and normal and tumour tissue specimens from patients with gastric cancer by reverse transcriptase-polymerase chain reaction (RT-PCR) and competitive PCR. Conditioned media (CM) of the gastric cancer cell lines were studied for the secretion of the IGFBPs by western ligand blot (WLB) and western immunoblot (WIB). IGF-I and IGF-II were expressed in all of the gastric cancer cell lines, and the normal and tumour tissue specimens. Overexpression of the IGFs, in particular, IGF-II, was observed in the tumour tissues. The expression pattern of IGFBPs was heterogeneous among the gastric cancer cell lines. IGFBP-2 was expressed in all of the gastric cancer cell lines, whereas IGFBP-1 was not detected in any cell lines. IGFBP-4 was expressed in the most of cell lines. IGFBP-3, IGFBP-5 and IGFBP-6 were expressed in approximately 50% of cell lines. In addition, exogenous IGF-I and IGF-II stimulated the proliferation of gastric cancer cells, suggesting the existence of a functional IGF system in gastric cancer. Taken together, our data-suggest that the IGF-IGFBP system may play an important role in the initiation, progression and metastasis of gastric cancer. Further studies are needed to understand the exact role of IGFs and IGFBPs in gastric neoplasia.