The Effects of Insulin-Like Growth Factors on Human G292 Osteosarcoma Cells

Abstract

Introduction: Osteosarcoma is the most common bone sarcoma in children and adolescents. It is an aggressive primary bone cancer recognized by abnormal cell proliferation and function. The insulin-like growth factor (IGF) system plays an integral role in the growth, differentiation, and developmental processes, and is involved in various physiological and pathological events. The IGF system consists of IGF I and II, their cell surface receptors and insulin-like growth factor binding proteins (IGFBP). IGF-binding proteins (IGFBPs) are important modulators of IGF signaling. IGF-II is a potent mitogen whose deregulation is linked to diverse pathologies and plays a role in tumorigenesis, development of different types of cancers such as liver, breast and prostate cancers, metastasis and resistance to existing forms of cancer therapy. Chromeceptin is a synthetic small molecule that induces expression of IGF inhibitory genes. It has been shown that chromeceptin inhibits insulin-induced adipogenesis and decreases the growth and viability of hepatocellular carcinoma cells that overexpress IGF-II. The involvement of IGF-II and IGFBP1 in cancer suggests that the analysis of their regulation may provide us with a better understanding of human cancers and new therapeutic approaches. Aim of the study : To study the effect of IGF-II on the activity of human G292 osteosarcoma cells, focusing both on the effects of endogenous and exogenous IGF-II levels. In addition, to study the role of IGFBPs and chromeceptin on G292 osteosarcoma cell activity. Material and Methods: The MTT assay was used to assess the activity of G292 (Clone A141B1) human osteosarcoma cells. Growth activity was analyzed after various periods of incubation in serum-free media. Enzyme-linked Immunosorbent Assays (ELISA) were used to detect the endogenous levels of IGF-II and IGFBP1 in the treated G292 human osteosarcoma cells. Result: Our experimental results show that chromeceptin plays a significant role in the activity of G292 osteosarcoma cells, since chromeceptin alone decreased cell activity of G292 osteosarcoma cells compared to the control group. With the concentrations of IGF-II added exogenously, very small effects were observed under the conditions studied. G292 cells appear to thrive in serum free medium and to be dependent in an autocrine manner on IGF-II and paracrine effects of this growth factor are minimal. In addition, we tested the effects of chromeceptin on IGFBP-1 in G292 cells and observed significant decreases in IGF-II levels. At concentrations that had significant effects on G292 cell activity and IGF-II levels, chromeceptin produced small, but significant increases in IGFBP1 levels. Conclusions: Our studies with the drug, chromeceptin, presented here strongly suggest a role of endogenous IGF-II in cell activity of G292 human osteosarcoma cells with a role of IGFBP-1 in this process as well. In general, our studies on the involvement of IGF-II in the human G292 osteosarcoma cell suggest that the further analysis of IGF-II regulation may lead to a better understanding of human bone cancers and possible new cancer therapies.