Cilengitide inhibits osteoclast adhesion through blocking the αvß3-mediated FAK/Src signaling pathway.

The remodeling of actin cytoskeleton of osteoclasts on the bone matrix is essential for osteoclastic resorption activity. A specific regulator of the osteoclast cytoskeleton, integrin αvß3, is known to provide a key role in the degradation of mineralized bone matrixes. Cilengitide is a potent inhibitor of integrins and is capable of affecting αvß3 receptors, and has anti-tumor and anti-angiogenic and apoptosis-inducing effects. However, its function on osteoclasts is not fully understood. Here, the cilengitide role on nuclear factor κB ligand-receptor activator (RANKL)-induced osteoclasts was explored. Cells were cultured with varying concentrations of cilengitide (0,0.002,0.2 and 20 µM) for 7 days, followed by detected via Cell Counting Kit-8, staining for tartrate resistant acid phosphatase (TRAP), F-actin ring formation, bone resorption assays, adhesion assays, immunoblotting assays, and real-time fluorescent quantitative PCR. Results demonstrated that cilengitide effectively restrained the functionality and formation of osteoclasts in a concentration-dependent manner, without causing any cytotoxic effects. Mechanistically, cilengitide inhibited osteoclast-relevant genes expression; meanwhile, cilengitide downregulated the expression of key signaling molecules associated with the osteoclast cytoskeleton, including focal adhesion kinase (FAK), integrin αvß3 and c-Src. Therefore, this results have confirmed that cilengitide regulates osteoclast activity by blocking the integrin αvß3 signal pathway resulting in diminished adhesion and bone resorption of osteoclasts.

G0/G1 Switch 2 Induces Cell Survival and Metastasis through Integrin-Mediated Signal Transduction in Human Invasive Breast Cancer Cells.

Human breast cancer cell line, MDA-MB-231, is highly invasive and aggressive, compared to less invasive cell line, MCF-7. To explore the genes that might influence the malignancy of MDA-MB-231, DNA microarray analysis was performed. The results showed that G0/G1 switch 2 (G0S2) was one of the most highly expressed genes among the genes upregulated in MDA-MB-231. Although G0S2 acts as a direct inhibitor of adipose triglyceride lipase, action of G0S2 in cancer progression is not yet understood. To investigate whether G0S2 affects invasiveness of MDA-MB-231 cells, G0S2 expression was inhibited using siRNA, which led to decreased cell proliferation, migration, and invasion of MDA-MB-231 cells. Consequently, G0S2 inhibition inactivated integrinregulated FAK-Src signaling, which promoted Hippo signaling and inactivated ERK1/2 signaling. In addition, G0S2 downregulation decreased ß-catenin expression, while E-cadherin expression was increased. It was demonstrated for the first time that G0S2 mediates the Hippo pathway and induces epithelial to mesenchymal transition (EMT). Taken together, our results suggest that G0S2 is a major factor contributing to cell survival and metastasis of MDA-MB-231 cells.

FBXW5 Promotes Tumorigenesis and Metastasis in Gastric Cancer via Activation of the FAK-Src Signaling Pathway.

: F-box/WD repeat-containing protein 5 (FBXW5) is a member of the FBXW subclass of F-box proteins. Despite its known function as a component of the Skp1-Cullin-F-box (SCF) ubiquitin ligase complex, the role of FBXW5 in gastric cancer tumorigenesis and metastasis has not been investigated. The present study investigates the role of FBXW5 in tumorigenesis and metastasis, as well as the regulation of key signaling pathways in gastric cancer; using in-vitro FBXW5 knockdown/overexpression cell line and in-vivo models. In-vitro knockdown of FBXW5 results in a decrease in cell proliferation and cell cycle progression, with a concomitant increase in cell apoptosis and caspase-3 activity. Furthermore, knockdown of FBXW5 also leads to a down regulation in cell migration and adhesion, characterized by a reduction in actin polymerization, focal adhesion turnover and traction forces. This study also delineates the mechanistic role of FBXW5 in oncogenic signaling as its inhibition down regulates RhoA-ROCK 1 (Rho-associated protein kinase 1) and focal adhesion kinase (FAK) signaling cascades. Overexpression of FBXW5 promotes in-vivo tumor growth, whereas its inhibition down regulates in-vivo tumor metastasis. When considered together, our study identifies the novel oncogenic role of FBXW5 in gastric cancer and draws further interest regarding its clinical utility as a potential therapeutic target.

Overexpression of Hsc70 promotes proliferation, migration, and invasion of human glioma cells.

Migration and invasion are often recognized as the main reasons for the high recurrence and death rates of glioma and limit the efficacy of surgery and other antitumor therapies. In this study, we found over activation of heat shock cognate protein 70 (Hsc70) in human glioma specimens, which was closely related to glioma grade. We investigated whether Hsc70 induced the migration and invasion of glioma cells. Wound healing and transwell migration assay were used to determine the migration and invasion ability of human glioma U251 and U87 cells, in which the expression of Hsc70 was knocked down by small interfering RNA. Western blot analysis was performed to determine the expression of FAK-Src signaling in malignant glioma cells. The results showed that Hsc70 deficiency significantly retarded migration and invasion and reduced the phosphorylation of FAK, Src, and Pyk2 in U251 and U87 cells. Overall, our results indicate that the migration and invasion capacity of human brain glioma cells is at least partly induced by Hsc70-dependent activation of FAK-Src signaling.

Acidic pHe regulates cytoskeletal dynamics through conformational integrin ß1 activation and promotes membrane protrusion.

An acidic extracellular pH (pHe) in the tumor microenvironment has been suggested to facilitate tumor growth and metastasis. However, the molecular mechanisms by which tumor cells sense acidic signal to induce a transition to an aggressive phenotype remain elusive. Here, we showed that an acidic pHe (pH 6.5) stimulation resulted in protrusion and epithelial-mesenchymal transition (EMT) of cancer cells, which promoted migration and matrix degeneration. Using computational molecular dynamics simulations, we reported acidic pHe-induced opening of the Integrin dimers (α5ß1) headpiece which indicated the activation of integrin. Moreover, acidic pHe promoted maturation of focal adhesions, temporal activation of Rho GTPases and microfilament reorganization through integrin ß1-activated FAK signaling. Furthermore, mechanical balance of cytoskeleton (actin, tubulin and vimentin) contributed to acidic pHe-triggered protrusion and morphology change. Taken together, these findings revealed that integrin ß1 could be a novel pH-regulated sensitive molecule which confers protrusion and malignant phenotype of cancer cells.