Insulin-Like Growth Factor Binding Protein-2 Binding to Extracellular Matrix Plays a Critical Role in Neuroblastoma Cell Proliferation, Migration, and Invasion

Abstract

IGF binding proteins (IGFBPs) modulate IGF cellular bioavailability and may directly regulate tumor growth and invasion. We have previously shown that IGFBP-2 binds and localizes IGF-I to the pericellular matrix and have provided some evidence suggesting that the heparin binding domain (HBD) or the arginine-glycine-aspartic acid (RGD) integrin binding motif may be involved in these interactions. However, the precise mechanisms involved remain to be elucidated. We therefore mutated the HBD or RGD sequence of IGFBP-2 and investigated consequent effects on extracellular matrix (ECM) binding, IGF-induced proliferation, and migration of neuroblastoma cells. IGFBP-2 and its arginine-glycine-glutamic acid (RGE) mutant similarly bound ECM components, whereas binding of mutant HBD-IGFBP-2 to each of the ECM substrates was markedly reduced by 70-80% (P < 0.05). IGF-I (100 ng/ml) increased incorporation of 3H-thymidine in neuroblastoma SK-N-SHEP cells by approximately 30%, an effect blunted by exogenously added native or either mutant IGFBP-2. Overexpression of IGFBP-2 and its RGE mutant potently promoted SHEP cell proliferation (5-fold), whereas SHEP cell proliferation was negligible when HBD-IGFBP-2 was overexpressed. Addition or overexpression of IGFBP-2 and its RGE mutant potently (P < 0.05) enhanced SHEP cell migration/invasion through the ECM. However, overexpression of the HBD-IGFBP-2 mutant potently inhibited (50-60%) SHEP cell invasion through ECM. Thus, IGFBP-2, which binds to the ECM, enhances proliferation and metastatic behavior of neuroblastoma cells, functions that directly or indirectly use the HBD but not the integrin binding sequence. Our novel findings thus point to a key role for the HBD of IGFBP-2 in the control and regulation of neuroblastoma growth and invasion.

Promotion of Cancer Cell Migration

“…For example, IGFBP-1 promotes cell migration by its C-terminal Arg-Gly-Asp (RGD) sequence binding to the ␣5␤1 integrin and activating focal adhesion kinase and MAPK (30,31). The heparin binding domains of IGFBP-5 and IGFBP-2 play important roles in stimulating cell migration and invasion (32,33). However, IGFBP-2 also inhibits IGF-dependent migration by an RGD-independent interaction with the ␣V␤3 integrin (34).…”

Insulin-Like Growth Factor Binding Protein-2: A Possible Regulator of Invasive Growth in Glioblastoma

“…IGFBP2 does, however, have an arginine-glycine-aspartic acid (RGD) motif, which binds to cell surface integrins, and a heparin-binding domain, which facilitates association with extracellular matrices (Figure 1). Both regions are able to localize IGFBP2 and IGFBP2/IGF complexes on/around the cell surface (Schutt et al, 2004;Russo et al, 2005;Wang et al, 2006). Among the six IGFBPs, only IGFBP1 and IGFBP2 possess a RGD motif (Table 1).…”

“…By virtue of its IGF binding capacity, IGFBP2 was initially considered to be an inhibitory factor of IGFs, particularly of IGF-II with K D values for IGF-I and IGF-II to be 1.14 and 0.37, espectively (Hwa et al, 1999;Russo et al, 2005). However, it was subsequently found to prolong the half-life of IGFs.…”

Primary pigmented nodular adrenocortical disease reveals insulin-like growth factor binding protein-2 regulation by protein kinase A

“…Proposed mechanisms include induction of metalloproteinase-2 in invasive bladder cancer [41] and glioblastoma cells [42], increased catalase activity in the malignant Y-1 and Caco-2 human colon tumor cells [43], and interactions with integrins in Ewing's sarcoma and breast cancer cells [44;45]. IGFBP-2's heparin binding domain was implicated in its enhancement of neuroblastoma cell migration and invasiveness [46], while its RGD motif was found to bind invasion inhibitory protein 45 (IIp45) and play a role in the invasiveness of glioblastoma multiforme cells [47]. Much remains to be elucidated about IGFBP-2 effects on cell proliferation and neoplasia, and the field is likely complicated by tissue-specific mechanisms and modifiers.…”