A fibrillar form of fibronectin induces apoptosis by activating SHP-2 and stress fiber formation

Abstract

Fibronectin (FN) is an endogenous ligand of integrins, which plays a critical role in cell adhesion and growth. Here, we converted globular FN (G-FN) into a fibrillar form (F-FN) and found that, even though both G-FN and F-FN interacted with integrin alpha5beta1, G-FN induced cellular proliferation, whereas F-FN resulted in apoptosis that was associated with deactivation of Akt/GSK-3beta and phosphorylation of SHP-2. SHP-2 inhibitor and anti-sense oligodeoxynucleotide decreased SHP-2 level and reversed the F-FN mediated apoptosis. F-FN also induced stress fiber formation associated with activation of RhoA, Rho kinase (ROCK), and filamin. Inhibition of ROCK by ROCK inhibitor or dominant negative plasmid treatment modulated F-FN mediated apoptosis. Pharmacological studies revealed that F-FN was effective in inhibiting the survival of SKOV-3 and MCF-7 cancer cells. These findings thus demonstrate that unlike G-FN, F-FN exhibits fibrillar structure to induce cell apoptosis that is associated with phosphorylation of SHP-2, activation of RhoA/ROCK and formation of stress fibers as well as deactivation of Akt/GSK-3beta.

Akt and RhoA inhibition promotes anoikis of aggregated B16F10 melanoma cells

“…Aggregates are embedded in secreted FN, which makes it possible to both activate α5β1 integrin and phosphorylate FAK on Tyr 397 , thereby producing slower, but detectable, cell proliferation than that of monolayer cultures and preventing anoikis (Hindie et al, 2005). Huang et al (2010) showed that in SKOV‐3 and MCF‐7 cancer cells, globular FN causes proliferation, whereas fibrillar FN triggers apoptosis, even though both types of FN interact with α5β1 integrins. Apoptosis is thus associated with the activation of RhoA/ROCK and the deactivation of Akt/downstream protein GSK‐3β (glycogen synthase kinase‐3β).…”

Fibrillar Human Serum Albumin Suppresses Breast Cancer Cell Growth and Metastasis

“…Further, our own studies recently found that fibrillar bovine serum albumin (F-BSA) induced apoptosis in human breast duct carcinoma cell line T47D, and fibrillar fibronectin (F-FN) induced apoptosis in human breast cancer cell line MCF-7. F-BSA and F-FN induced BHK-21 cell (baby hamster kidney cell) apoptosis through negatively regulating the integrin/FAK/Akt/GSK-3 signaling pathway and activating SHP-2 and RhoA/ROCK (Huang et al, 2009;Huang et al, 2010). Together these results suggest that inhibition of the 1 integrin signaling pathway may provide a promising therapeutic approach to breast cancer metastasis.…”

“…Previously, we demonstrated that F-BSA and F-FN induced apoptosis in the less malignant T47D and MCF-7 breast cancer cell lines, respectively (Huang et al, 2009;Huang et al, 2010). In this study, we examine whether F-HSA induced cytotoxicity in the more malignant breast www.intechopen.com cancer cell lines, TS/A and MDA-MB-231, using a 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT)-colorimetry assay to measure the cell viability (MERCK, Darmstadt, Germany).…”

“…Whether the fibrillar proteins may be used as anti-cancer drugs in the cancer therapies is largely unclear. We have developed a novel process to convert globular proteins, bovine serum albumin and fibronectin, to fibrillar forms using detergent assisted refolding chromatography (Huang et al, 2009;Huang et al, 2010). This procedure is easier to perform than other methods reported to convert proteins to fibrillar structures such as glycation, sonication, or high temperature incubation (Azakami et al, 2005;Taboada et al, 2006).…”

“…Integrin signaling is activated by ECM proteins or growth factors through focal adhesion kinase (FAK), PI3K, and Akt, a major downstream target of PI3K signaling, known to be involved in various cellular processes such as cell survival, cell cycle, metabolism, protein synthesis, and transcriptional regulation (Mitra & Schlaepfer, 2006). We showed that fibrillar proteins induced cellular apoptosis (Huang et al, 2009;Huang et al, 2010). The mechanism of the cytotoxic effects of F-BSA in BHK-21 cells (baby hamster kidney cell) was due to modulation of the 51 integrin/FAK/Akt/GSK-3 /caspase-3 signaling pathway.…”