Autocrine Transforming Growth Factor α Regulates Cell Adhesion by Multiple Signaling via Specific Phosphorylation Sites of p70S6 Kinase in Colon Cancer Cells

Abstract

Recently, we showed that autocrine transforming growth factor ␣ (TGF␣) controls the epidermal growth factor receptor (EGFR)-mediated basal expression of integrin ␣ 2 , cell adhesion and motility in highly progressed HCT116 colon cancer cells. We also reported that the expression of basal integrin ␣ 2 and its biological effects are critically controlled by the constitutive activation of the ERK/MAPK pathway (Sawhney, R. S., Sharma, B., Humphrey, L. E., and Brattain, M. G. (2003)

Regulation of mTOR and S6K1 activation by the nPKC isoforms, PKCε and PKCδ, in adult cardiac muscle cells

“…Several recent studies have identified a critical role for the nPKC isoforms in the activation of S6K1 (41,47). In a recent study the novel PKC isoforms, PKC ε and PKC δ , but not the classical PKC isoforms, PKC α or PKC β , were shown to be involved in PE-stimulated S6K1 phosphorylation of adult rat cardiomyocytes (as measured through electrophoretic mobility shifting of S6K1) (41).…”

Integrin α2-mediated ERK and Calpain Activation Play a Critical Role in Cell Adhesion and Motility via Focal Adhesion Kinase Signaling

“…GEO cells were cultured in a humidified incubator at 37°C for 3-4 days with 5% CO 2 in a chemically defined serum-free medium. At about 80% confluence, the medium was changed to supplemented McCoy's (SM) medium (8). Cells were harvested with trypsin (0.125%) at 37°C and pelleted by gentle centrifugation at 800 ϫ g in a clinical centrifuge.…”

“…GEO cells were grown in serum-free medium containing 4 g/ml transferrin and 20 g/ml insulin at 37°C with 5% CO 2 . For transient transfection experiments, cells were grown to 50 -60% confluence, medium was changed to SM, and transfections were carried out using FUGENE 6 according to our previous report (8). The ratio of FUGENE 6 to DNA was maintained at 10 l of FUGENE 6 to 2.5 g of DNA.…”

“…Subsequently, the MTT procedure was followed as described previously (6,8). After trypsinization (0.125% trypsin in EDTA), GEO cells were preincubated at 37°C with or without inhibitors for 2 h to determine cell adhesion.…”

The Akt of translational control

“…Therefore, further experiments need to be performed to identify the components responsible for control of 5 0 TOP mRNA translation downstream of the PI3K pathway. Importantly, the activity of S6K1 and 2 is upregulated in tumors from different histological origins Sahin et al, 2004;Savinska et al, 2004;Sawhney et al, 2004;Surace et al, 2004) and, remarkably, cancer cells harboring mutations that aberrantly upregulate the PI3K/Akt pathway display a hyperactivation of S6K activity (Ruggero and Pandolfi, 2003;Stephens et al, 2005).…”