Intrinsic FAK activity and Y925 phosphorylation facilitate an angiogenic switch in tumors

Abstract

Elevated focal adhesion kinase (FAK) expression occurs in advanced cancers, yet a signaling role for FAK in tumor progression remains undefined. Here, we suppressed FAK activity in 4T1 breast carcinoma cells resulting in reduced FAK Y925 phosphorylation, Grb2 adaptor protein binding to FAK, and signaling to mitogen-activated protein (MAP) kinase (MAPK). Loss of a FAK-Grb2-MAPK linkage did not affect 4T1 cell proliferation or survival in culture, yet FAK inhibition reduced vascular endothelial growth factor (VEGF) expression and resulted in small avascular tumors in mice. This FAK-Grb2-MAPK linkage was essential in promoting angiogenesis as reconstitution experiments using Src-transformed FAK-null fibroblasts revealed that point mutations affecting FAK catalytic activity (R454) or Y925 phosphorylation (F925) disrupted the ability of FAK to promote MAPK- and VEGF-associated tumor growth. Notably, in both FAK-inhibited 4T1 and Src-transformed FAK-null cells, constitutively activated (CA) mitogen-activated protein kinase kinase 1 (MEK1) restored VEGF production and CA-MEK1 or added VEGF rescued tumor growth and angiogenesis. These studies provide the first biological support for Y925 FAK phosphorylation and define a novel role for FAK activity in promoting a MAPK-associated angiogenic switch during tumor progression.

Δ9-Tetrahydrocannabinol inhibits epithelial growth factor-induced lung cancer cell migration in vitro as well as its growth and metastasis in vivo

“…The reduction in angiogenesis (CD31 immunostaining), proliferation (Ki67 immunostaining) and phosphorylation of FAK, ERK1/2 and AKT in tumors from THC-treated animals may be responsible for the reduced tumor growth. Tumor progression has been shown to be associated with FAK, AKT and MAPK activity (Mitra et al, 2006). These results correlate with the previously observed antiangiogenic effects of cannabinoids .…”

Pyk2 Controls Integrin-Dependent CTL Migration through Regulation of De-Adhesion

“…It is possible that the Pyk2 FAT domain interferes with endogenous Pyk2 Y881 phosphorylation at the trailing edge, which may serve an important role in trailing edge de-adhesion. In support of this, expression of the C-terminal domain of FAK reduces Y925 (equivalent to Y881 on Pyk2) phosphorylation of endogenous FAK (51). Expression of the Pyk2 FAT domain could potentially block endogenous Pyk2 Y881 phosphorylation by competing with endogenous Pyk2 or other regulatory factors, thereby preventing disassembly of adhesion structures at the trailing edge.…”

Morphogenesis of human endothelial cells is inhibited by DAB2 via Src

“…3C). Emerging evidence supports the important role for FAK in the endothelial cell motility response [28]. Since in cancer cells specific Src-dependent phosphorylation of FAK Y925 is associated with the ability of cells to dynamically regulate cell adhesions [29], we next investigated the phosphorylation state of FAK in endothelial cells silenced for DAB2.…”

“…DAB2 affects MAPK signaling, endothelial cell viability and proliferation Since Y925 in FAK is involved in intra-and inter-molecular signalling crosstalk and activation of downstream pathways [28], we next examined the impact of DAB2 knockdown on the activation status of the MAPK family, ERK-1/2, JNK and p38 serine/threonine protein kinases that are involved in proliferation and migration of endothelial cells. As expected, in growth factor-depleted conditions, control endothelial cells did not show ERK phosphorylation.…”