Maa MC, Lee JC, Chen YJ, Chen YJ, Lee YC, Wang ST et al.. EPS8 facilitates cellular growth and motility of colon cancer cells by increasing the expression and activity of focal adhesion kinase. J Biol Chem 282: 19399-19409
ABSTRACT In an attempt to study the role of Eps8 in human carcinogenesis, we observe that ectopic overexpression of Eps8 in SW480 cells (low Eps8 expression) increases cell proliferation. By contrast, expressing eps8 small interference RNA in SW620 and WiDr cells (high Eps8 expression) reduces their proliferation rate. Interestingly, attenuation of Eps8 decreases Src Pi-Tyr-416, Shc Pi-Tyr-317, and serum-induced FAK Pi-Tyr-397 and Pi-Tyr-861. Remarkably, by virtue of mammalian target of rapamycin/STAT3 Pi-Ser-727, Eps8 modulates FAK expression required for cell proliferation. Within 62% of colorectal tumor specimens examined, >2-fold enhancement of Eps8 as compared with their normal counterparts is observed, especially for those from the advanced stage. In agreement with the modulation of FAK by Eps8, the concomitant expression of these two proteins in tumor specimens is observed. Notably, Eps8 attenuation also impedes the motility of SW620 and WiDr cells, which can be rescued by ectopically expressed FAK. This finding discloses the indispensability of Eps8 and FAK in cell locomotion. These results provide a novel mechanism for Eps8-mediated FAK expression and activation in colon cancer cells.
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- "In addition, it has been shown that integrins target Rac1 to the plasma membrane in lipid rafts, localizing GTP-ase activity to areas within the cell where actin remodeling is required and, in migrating cells, inhibition of FAK suppresses lipid raft internalization, thereby maintaining Rac1 activation (del Pozo et al., 2000, 2004). Eps8 has been shown to regulate FAK expression and activation (Maa et al., 2007), which suggests an additional mechanism by which Eps8 may regulate the activation and localization of Rac1. "
ABSTRACT: Oral squamous cell carcinoma (OSCC) is a lethal disease and early death usually occurs as a result of local invasion and regional lymph node metastases. Current treatment regimens are, to a certain degree, inadequate, with a 5-year mortality rate of around 50% and novel therapeutic targets are urgently required. Using expression microarrays, we identified the eps8 gene as being overexpressed in OSCC cell lines relative to normal oral keratinocytes, and confirmed these findings using RT-PCR and western blotting. In human tissues, we found that Eps8 was upregulated in OSCC (32% of primary tumors) compared with normal oral mucosa, and that expression correlated significantly with lymph node metastasis (P=0.032), suggesting a disease-promoting effect. Using OSCC cell lines, we assessed the functional role of Eps8 in tumor cells. Although suppression of Eps8 produced no effect on cell proliferation, both cell spreading and migration were markedly inhibited. The latter cell functions may be modulated through the small GTP-ase, Rac1 and we used pull-down assays to investigate the role of Eps8 in Rac1 signaling. We found that alphavbeta6- and alpha5beta1-integrin-dependent activation of Rac1 was mediated through Eps8. Knockdown of either Eps8 or Rac1, inhibited integrin-dependent cell migration similarly and transient expression of constitutively active Rac1 restored migration of cells in which Eps8 expression had been suppressed. We also showed that knockdown of Eps8 inhibited tumor cell invasion in an organotypic model of OSCC. These data suggest that Eps8 and Rac1 are part of an integrated signaling pathway modulating integrin-dependent tumour cell motility and identify Eps8 as a possible therapeutic target.Oncogene 06/2009; 28(27):2524-34. DOI:10.1038/onc.2009.105 · 8.56 Impact Factor
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- "Cell Tissue Res (2009) 336:213–223 221 TGFβ modulation of protein synthesis via mTOR not having previously been reported, this model is consistent with a previous report that ERK signaling is implicated in translational control upstream of mTOR via phosphorylation of TSC2 enabling mTOR signaling (Ma et al. 2005), and with the observation that another cytokine, Cyr61, upregulates hypoxia-inducing factor-1α protein in gastric cancer cells via mTOR-dependent stimulation of de novo protein synthesis (Lin et al. 2008). Although we have not specifically studied the adaptor protein Eps8 here, Eps8 has also been linked to the upregulation of FAK expression via mTOR activation in human colon cancer cell lines (Maa et al. 2007). Despite other transcription factors possibly playing a role in the TGFβ-independent regulation of FAK, we have observed the rapid activation of mTOR, p70 S6 , and 4E-BP1 kinase in 5–15 min after TGFβ treatment. "
ABSTRACT: Increasing evidence is available showing the importance of the FAK (focal adhesion kinase) protein level in the migration and homeostasis of intestinal cells. TGFβ (transforming growth factor beta) modulates FAK protein expression in a complex fashion not only by inducing the activation of p38 and Smad signaling resulting in increased fak promoter activity and increased FAK protein levels, but also by activating ERK (extracellular signal regulated kinases), p38, and the Smad pathway. We show that the blockade of ERK signaling by a specific MEK (MAPK kinase) inhibitor attenuates TGFβ−induced FAK mRNA stability and reduces FAK protein levels in rat IEC-6 intestinal epithelial cells. The mTOR (mammalian target of rapamycin)-specific inhibitor rapamycin and small interfering RNAs for mTOR and p70S6 kinase also block TGFβ−induced FAK protein synthesis. Furthermore, we have found that a TGFβ−induced increase in wound closures in monolayers of these cells is abolished in the presence ERK or mTOR inhibition. Thus, TGFβ also modulates FAK protein levels in cultured rat IEC-6 intestinal epithelial cells via ERK activation, acting at the transcriptional level to complement Smad signaling and at on the translational level via the mTOR pathway downstream of ERK, which in turn promotes intestinal epithelial cell migration.Cell and Tissue Research 05/2009; 336(2):213-223. DOI:10.1007/s00441-009-0776-z · 3.33 Impact Factor
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ABSTRACT: Focal adhesion kinase (FAK) regulates cell migration, proliferation, and apoptosis. FAK protein is reduced at the edge of migrating gut epithelial sheets in vitro, but it has not been characterized in restitutive gut mucosa in vivo. Here we show that FAK and activated phospho-FAK (FAK(397)) immunoreactivity was lower in epithelial cells immediately adjacent to human gastric and colonic ulcers in vivo, but dramatically increased in epithelia near the ulcers, possibly reflecting stimulation by growth factors absent in vitro. Transforming growth factor (TGF)-beta, but not fibroblast growth factor, platelet-derived growth factor, or vascular endothelial growth factor, increased FAK levels in Caco-2 and IEC-6 cells. Epithelial immunoreactivity to TGF-beta and phospho-Smad3 was also higher near the ulcers, varying in parallel with FAK. The TGF-beta receptor antagonist SB431542 completely blocked TGF-beta-induced Smad2/3 and p38 activation in IEC-6 cells. SB431542, the p38 antagonist SB203580, and siRNA-mediated reduction of Smad2 and p38alpha prevented TGF-beta stimulation of both FAK transcription and translation (as measured via a FAK promoter-luciferase construct). FAK(397) levels were directly related to total FAK protein expression. Although gut epithelial motility is associated with direct inhibition of FAK protein adjacent to mucosal wounds, TGF-beta may increase FAK protein near but not bordering mucosal ulcers via Smad2/3 and p38 signals. Our results show that regulation of FAK expression may be as important as FAK phosphorylation in critically influencing gut epithelial cell migration after mucosal injury.American Journal Of Pathology 07/2008; 173(2):385-99. DOI:10.2353/ajpath.2008.070729 · 4.60 Impact Factor