Insulin-like growth factor-I-mediated survival from Anoikis: Role of cell aggregation and focal adhesion kinase

Abstract

Anoikis is a form of cell death that occurs when cells are denied attachment to the extra-cellular matrix. Using p6 cells, that are 3T3 cells overexpressing the type 1 insulin-like growth factor receptor (IGF-IR), we show that these cells undergo apoptosis when seeded on polyHEMA plates in serum-free medium (SFM). IGF-I protects p6 cells from anoikis, without inducing mitogenesis or DNA synthesis. In the surviving p6 cells in suspension cultures, the focal adhesion kinase (FAK) is tyrosyl phosphorylated by IGF-I, although this phosphorylation occurs only after several hours. The importance of FAK in protection from anoikis is confirmed by v-src-transformed R-cells, in which FAK is constitutively phosphorylated, that survive even in SFM. Surviving cells, whether p6 or v-src transformed, tend to form large cell aggregates, whose appearance precedes the phosphorylation of FAK. These and other findings suggest that FAK phosphorylation in the case of IGF-I is a mediated effect rather than a direct one. When p6 cells are plated on polyHEMA dishes, IGF-I induces cell aggregation and this aggregation correlates with survival and the eventual phosphorylation of FAK.

The p42/p44 MAP Kinase Pathway Prevents Apoptosis Induced by Anchorage and Serum Removal

“…It was reported a few years ago that normal cells deprived of matrix attachment undergo programmed cell death, termed anoikis (reviewed in Ruoslahti and Reed [1994]). Although first demonstrated in epithelial and endothelial cells (Frisch and Francis, 1994;Re et al, 1994), anoikis has now been observed to varying extents in a number of cell types, including smooth muscle and neuronal cells as well as various fibroblastic cells (Ishizaki et al, 1995;McGill et al, 1997;Meredith and Schwartz, 1997;Valentinis et al, 1998Valentinis et al, , 1999, and is reviewed in Meredith and Schwartz (1997). One biologically significant consequence of this phenomenon may be suppression of tumorogenesis, because the loss of anchorage dependence is one of the best correlates of tumoral growth in vivo.…”

Insulin-Like Growth Factor-I and Transferrin Mediate Growth and Survival of Chinese Hamster Ovary Cells

“…It does so in the absence of cell division. Hence, the mitogenic activity of IGF-I may be distinct from its survival activity as previously suggested (21)(22)(23).…”

Insulin-Like Growth Factor I Receptor Signaling System in JC Virus T Antigen-Induced Primitive Neuroectodermal Tumors--Medulloblastomas

“…Data from JCV T antigen-positive and -negative murine medulloblastoma cell lines (Krynska et al, 2000;Wang et al, 2001) indicate that the activation of mitogenic and antiapoptotic signals from the IGF-IR are modulated by the presence of JCV T antigen ( Figure 2). To deny attachment, cells were cultured on 35-mm dishes covered with polyHEMA as previously described Valentinis et al, 1998). In suspension, JCV T antigen-positive cells (BsB8) survive well in serum-free medium.…”

“…JCV T antigen-positive (BsB8) cells, T antigen-negative (Bs-1a) cells, and Bs-1a cells stably transfected with JCV T antigen cDNA (pCDNA-3/zeo/JCV-T), Bs-1a/JCT cells, were cultured on PolyHema-coated plates to avoid cell attachment (Valentinis et al, 1998). The cells were cultured either in serum-free medium (SFM) or were stimulated with 50 ng/ml IGF-I (IGF).…”

“…Cells were stably transduced with the empty retroviral vector (EV) or with the vector containing PH/PTB cDNA under the control of CMV promoter. Cell growth and survival was evaluated on PolyHema-coated dishes in the presence or absence of IGF-I, as previously described (Valentinis et al, 1998). Cell number was determined within 1 h after plating (T0), and at 48 h later.…”