The effect of focal adhesion kinase gene silencing on 5‐fluorouracil chemosensitivity involves an Akt/NF‐κB signaling pathway in colorectal carcinomas

Abstract

Multicellular resistance (MCR) is produced because multicellular spheroids (MCSs) are formed with a broad cell-cell connection when cultured in three-dimensions, which limits the clinical treatment efficacy in solid tumors. Focal adhesion kinase (FAK) plays an important role in apoptosis, survival and cell adhesion between cells and their extracellular matrix. In this study, we investigated the expressions of FAK, Akt and NF-jB in human colorectal cancer (CRC), and the effects of FAK gene silencing on MCSs formation and 5-fluorouracil (5-FU) chemosensitivity in colon carcinoma MCSs culture cells. In CRC samples, FAK, Akt and NF-jB were overexpressed. The positive expression of FAK correlated notably with lymph node metastasis and cellular differentiation. Positive expressions of Akt and NF-jB were significantly related to cellular differentiation and lymph node metastasis, respectively. Furthermore, positive expression of FAK correlated with that of Akt and NF-jB. The expression of FAK was inhibited significantly by a small hairpin RNA targeting FAK. Knockdown of FAK reversed the formation and aggregation of MCSs, significantly decreased the 50% inhibitory concentration of 5-FU, and markedly increased MCS culture cells apoptosis. These effects were associated with reduced levels of Akt and NF-jB. These results indicate that suppressing FAK expression potentiated 5-FU-induced cytotoxicity and contributed to its chemosensitizing effect by suppressing Akt/NF-jB signaling in colon carcinoma MCS culture cells. These data also imply that FAK mediates MCR of CRC through the survival signaling pathway FAK/Akt/NF-jB.Focal adhesion kinase (FAK) is a protein tyrosine kinase involved in the control of interactions between cells and their extracellular matrix. Moreover, FAK plays an important role in cell spreading, migration, motility, apoptosis and survival as a key regulator of these cellular signaling events.

High glucose-induced resistance to 5-fluorouracil in pancreatic cancer cells alleviated by 2-deoxy-D-glucose

“…The results demonstrated that active PI3K-Akt by high-glucose concentrations decreased the antitumor effect of 5-Fu, which is in agreement with previous studies (19,(27)(28)(29)(30)(31). Of note, 2-DG significantly reversed the resistance to 5-Fu in 25 mM of glucose.…”

Focal adhesion kinase antagonizes doxorubicin cardiotoxicity via p21Cip1

“…However, it has been shown that chronic DOX cardiotoxicity also involves myocyte apoptosis [64], indicating the likelihood that similar pathways are involved. Our conclusion fits with the fact that FAK is frequently up-regulated in a variety of cancers, is associated with poor prognosis and patient survival, and that inactivation of FAK in breast cancer cells exaggerated DOX-induced apoptosis [11, 14-19, 65]. …”

“…Since integrins lack intrinsic kinase activity, transduction of integrin-mediated survival signals requires cytoplasmic signaling molecules. Focal adhesion kinase (FAK), a nonreceptor protein tyrosine kinase, associates with the cytoplasmic tails of all β1-containing integrins and its activity is critical for integrin signaling, including the signals that mediate cancer cell resistance to cytotoxic agents [11, 14-19]. …”

Fibronectin extra domain A (EDA) sustains CD133+/CD44+ subpopulation of colorectal cancer cells

“…Indeed, EDA silencing in SW480 cells dramatically reduced phosphorylation of FAK as well as the two FAK downstream kinases Akt and Erk1/2 (Cabodi et al, 2010) (Figure 5b). We have previously generated a plasmid expressing FAK shRNA that can efficiently silence FAK in SW480 cells (Chen et al, 2010). To determine if EDA requires FAK to activate β-catenin, this FAK shRNA plasmid was transiently transfected into SW480-derived CD133 + /CD44 + cells stably overexpressing EDA.…”