An altered fibronectin matrix induces anoikis of human squamous cell carcinoma cells by suppressing integrin alpha v levels and phosphorylation of FAK and ERK

Abstract

Fibronectin regulates many cellular processes, including migration, proliferation, differentiation, and survival. Previously, we showed that squamous cell carcinoma (SCC) cell aggregates escape suspension-induced, p53-mediated anoikis by engaging in fibronectin-mediated survival signals through focal adhesion kinase (FAK). Here we report that an altered matrix, consisting of a mutated, nonfunctional high-affinity heparin-binding domain and the V region of fibronectin (V+H-), induced anoikis in human SCC cells; this response was blocked by inhibitors of caspase-8 and caspase-3. Anoikis was mediated by downregulation of integrin alpha v in a panel of SCC cells and was shown to be proteasome-dependent. Overexpression of integrin alpha v or FAK inhibited the increase in caspase-3 activation and apoptosis, whereas suppression of alpha v or FAK triggered a further significant increase in apoptosis, indicating that the apoptosis was mediated by suppression of integrin alpha v levels and dephosphorylation of FAK. Treatment with V+H- decreased the phosphorylation of extracellular signal-regulated kinase (ERK) 1 and 2, and direct activation of ERK by constitutively active MEK1, an ERK kinase, increased ERK1 and ERK2 phosphorylation and inhibited the increase in apoptosis induced by V+H-. ERK acted downstream from alpha v and FAK signals, since alpha v and FAK overexpression inhibited both the decrease in ERK phosphorylation and the increase in anoikis triggered by V+H-. These findings provide evidence that mutations in the high-affinity heparin-binding domain in association with the V region of fibronectin, or altered fibronectin matrices, induce anoikis in human SCC cells by modulating integrin alpha v-mediated phosphorylation of FAK and ERK.

The effect of RGD peptides on osseointegration of hydroxyapatite biomaterials

“…Hence, the RGD sequence by itself elicits weaker integrin activation than full length adhesion proteins [20,21]. For example, integrin binding to full length FN and VN activates the downstream signaling molecules FAK and ERK [31], leading to the induction of osteogenic gene expression [32], alkaline phosphatase activity, calcium deposition [33,34], and runx2 activation [33]. In contrast, cell adhesion to RGD was shown to activate FAK, but not ERK [35].…”

Tumour–stroma crosstalk in the development of squamous cell carcinoma

“…The fibronectins themselves are large extracellular matrix glycoproteins often found in the plasma and other body fluids. They participate in cell adhesion, migration, invasion, and survival by activating integrin and proteoglycan receptors thru specific signalling pathways such as the extracellular signal-regulated kinase (ERK) (Kamarajan and Kapila 2007). Studies using an altered fibronectin protein showed that SCC cells escape suspensioninduced death (anoikis) by forming multicellular aggregates which avail themselves of fibronectin survival signals mediated by integrin αV and focal adhesion kinase activation (Zhang, Lu et al 2004).…”

Induction of apoptosis of detached oral squamous cell carcinoma cells by safingol. Possible role of Bim, focal adhesion kinase and endonuclease G

“…Disruption of FAK signaling by various techniques induces cell death in cancers after the induction of cell rounding and detachment from the substratum. It was also reported that anoikis was associated with reduced levels of FAK [21,22].…”