Insulin-like growth factor-I-mediated survival from anoikis: role of cell aggregation and focal adhesion kinase.
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.
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
B
B
Valentinis
K
K
Reiss
R
R
Baserga
D016475:3T3 Cells / Q000737:chemistry / Q000166:cytology / Q000201:enzymology; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002449:Cell Aggregation / Q000502:physiology; D002461:Cell Line, Transformed / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D016391:Genes, src / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology*; D051379:Mice; D010766:Phosphorylation; D011102:Polyhydroxyethyl Methacrylate; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*
D015815:Cell Adhesion Molecules; D011102:Polyhydroxyethyl Methacrylate; D007334:Insulin-Like Growth Factor I; D004247:DNA; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse