Enhanced v-Src-induced oncogenic transformation in the absence of focal adhesion kinase is mediated by phosphatidylinositol 3-kinase.
We showed previously [K. Moissoglu, I.H. Gelman, J. Biol. Chem. 278 (2003) 47946-47959] that oncogenic v-Src could induce 7- to 10-fold greater anchorage-independent growth (AIG) in FAK-null mouse embryo fibroblasts (MEF) compared to those expressing FAK. Here, we demonstrate that the enhanced AIG (eAIG) correlates with increased activation levels of phosphatidylinositol 3-kinase (PI3K) and not with changes in the protein levels of the p85 regulatory subunit of PI3K, PDK1 or PTEN- modulators, and/or mediators of PI3K activity. eAIG could be blunted selectively by treatment with the PI3K inhibitor, LY294002, or by overexpression of either the PI3K antagonist, PTEN, dominant-interfering alleles of PI3K or a downstream PI3K mediator, AKT, but not by the MEK inhibitor, PD98059, dominant-interfering alleles of MEK or the signal transducer and activator of transcription (STAT)-3. In contrast, RNAi-mediated knockdown of FAK resulted in increased v-Src-induced AIG. Expression of a constitutively active PI3K allele was sufficient to induce higher levels of AIG, whereas overexpression of v-Src produced only larger-sized colonies in soft agar. Interestingly, FAK was required for full activation of PI3K by PDGF whereas the activation of PI3K by insulin was significantly increased in FAK-/- cells. Thus, although FAK is dispensable for v-Src-induced oncogenic transformation in vitro, it may exert either positive or negative effects on signaling or motility depending on which pathways are activated in cancer cells.
Moissoglu
Konstadinos
K
Department of Cancer Genetics, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14623, USA.
Sachdev
Sanjay
S
Gelman
Irwin H
IH
D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D004789:Enzyme Activation; D005419:Flavonoids / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D017353:Gene Deletion; D051379:Mice; D018345:Mice, Knockout; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism
D005419:Flavonoids; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D015688:Oncogene Protein pp60(v-src); C496051:Ptk2 protein, mouse; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one