Role of tissue transglutaminase 2 in the acquisition of a mesenchymal-like phenotype in highly invasive A431 tumor cells.

Background: Cancer progression is closely linked to the epithelial-mesenchymal transition (EMT) process. Studies have shown that there is increased expression of tissue tranglutaminase (TG2) in advanced invasive cancer cells. TG2 catalyzes the covalent cross-linking of proteins, exhibits G protein activity, and has been implicated in the modulation of cell adhesion, migration, invasion and cancer metastasis.

Effects of dietary flavonoids, luteolin, and quercetin on the reversal of epithelial-mesenchymal transition in A431 epidermal cancer cells.

Highly invasive A431-III cells, which are derived from parental A431-P cells, were originally isolated by three successive passages through a Boyden chamber using a Matrigel-coated membrane support. The greater invasion potential shown by A431-III cells was due to their increased ability to spread/migrate, which was associated with enhanced MMP activity. The tumor progression events evoked by A431-P cells compared to A431-III cells may help identify useful strategies for evaluating the epithelial-mesenchymal transition (EMT) and these cell lines could be a reliable model for evaluating tumor metastasis events.

Matrix metalloproteinase-9 cooperates with transcription factor Snail to induce epithelial-mesenchymal transition.

One of the most fundamental biological processes in tumor metastasis is the process of epithelial-mesenchymal transition (EMT). During EMT, zinc-finger-family of transcription factors such as Snail, Slug and Twist, and matrix metalloproteinases (MMPs) are upregulated, and this correlates with increased tumor cell invasion and motility. We previously obtained a highly invasive A431-III tumor subline, which is a rich source of MMP-9 and observed a plausible link between MMP levels and the promotion of EMT.

Up-regulation of fibronectin and tissue transglutaminase promotes cell invasion involving increased association with integrin and MMP expression in A431 cells.

In human tumors, fibronectin (FN) expression is positively associated with tumor metastatic potential and matrix metalloproteinase (MMP) secretion. Additionally, tissue transglutaminase (TG2) is implicated as playing an important role in tumor progression, and acts as a co-receptor for integrin-mediated cell binding to FN. This study explored the involvement of FN and TG2 in cancer cell metastasis using the recently established highly invasive A431-III subline.

Dephosphorylation of cancer protein by tyrosine phosphatases in response to analogs of luteinizing hormone-releasing hormone and somatostatin.

Protein phosphorylation/dephosphorylation of tyrosine residues is an important regulatory mechanism in cell growth and differentiation. Previously it has been reported that RC-160, an octapeptide analog of somatostatin, and [D-Trp6]LHRH, an agonist of luteinizing hormone-releasing hormone (LHRH), stimulate receptor-mediated activity of tyrosine phosphatases (PTP) and reverse growth promotion of the tyrosine kinase (PTK) class of oncogenes in tumor cells. The effect of RC-160 and [D-Trp6]LHRH on protein phosphorylation was further examined in surgical specimens of human carcinomas.

Investigation of MMP-2 and -9 in a highly invasive A431 tumor cell sub-line selected from a Boyden chamber assay.

In this study, highly invasive tumor cell lines (designated A431-I, -II and -III) derived from parental A431 tumor cells (A431-P) were isolated by three successive passages through a Boyden chamber with matrigel-coated membrane support. The invasive potential and the activity of secreted MMP-9 of each sub-line increased significantly compared to the A431-P (A431-III > A431-II > A431-I) as evidenced by the in vitro invasion assay, gelatin zymography and immunoblotting analyses. RT-PCR results also revealed the elevated expression of MMP-9 in A431-III.

Critical involvement of ILK in TGFbeta1-stimulated invasion/migration of human ovarian cancer cells is associated with urokinase plasminogen activator system.

The present study investigated the role of integrin-linked kinase (ILK) in TGFbeta1-stimulated invasion/migration of human ovarian cancer cells. We investigated TGFbeta1 regulation of ILK, and effects of ILK knockdown on TGFbeta1-stimulated invasion/migration and the associated proteinase systems, urokinase plasminogen activator (uPA) and matrix metalloproteinases (MMPs) in SKOV3 cells. TGFbeta1 stimulated ILK kinase activity, and had no effect on ILK protein/mRNA levels.

Targeting of focal adhesion kinase by flavonoids and small-interfering RNAs reduces tumor cell migration ability.

Focal adhesion kinase (FAK), a member of a growing family of structurally distinct protein tyrosine kinases (PTK), has been linked to specific phosphorylation events, and the elevation of FAK activity in human carcinoma cells is associated with increased invasive potential. In the present study, therefore, we developed two experiments to test the hypothesis that FAK is a determinant of, and plays an important role in, regulating tumor cell migration. In the first, the biological functions of FAK were examined using flavonoid inhibition.

The antitumor activities of flavonoids.

The flavonoids are polyphenolic compounds found as integral components of the human diet. They are universally present as constituents of flowering plants, particularly of food plants. The flavonoids are phenyl substituted chromones (benzopyran derivatives) consisting of a 15-carbon basic skeleton (C6-C3-C6), composed of a chroman (C6-C3) nucleus (the benzo ring A and the heterocyclic ring C), also shared by the tocopherols, with a phenyl (the aromatic ring B) substitution usually at the 2-position.

Transinactivation of the epidermal growth factor receptor tyrosine kinase and focal adhesion kinase phosphorylation by dietary flavonoids: effect on invasive potential of human carcinoma cells.

Focal adhesion kinase (FAK), a member of a growing family of structurally distinct protein tyrosine kinases (PTK), has been linked to specific phosphorylation events, and the elevation of FAK activity in human carcinoma cells correlated with increased invasive potential. Transactivation of the epidermal growth factor receptor (EGFR) tyrosine kinase activity is proposed to stimulate cell migration and the subsequent activation of downstream signaling pathways. Quercetin (Qu) and luteolin (Lu), are potent PTK inhibitors as well as putative chemopreventive agents.

Blockade of the epidermal growth factor receptor tyrosine kinase activity by quercetin and luteolin leads to growth inhibition and apoptosis of pancreatic tumor cells.

To glean insights into the mechanism of their action, we assessed the effects of two flavonoids, quercetin (Qu) and luteolin (Lu), on the growth and epidermal growth factor receptor (EGFR) tyrosine kinase activity of MiaPaCa-2 cancer cells. Exposure of these EGFR-expressing cells to 20 microM Qu or Lu resulted in concomitant decreases in cellular protein phosphorylation and growth. On the cellular level, Qu and Lu sensitivity correlated with EGFR levels and rapid cell proliferation, indicating the possibility of targeting those cells most prone to neoplastic progression.

Inhibitory effects of a luteinizing hormone-releasing hormone agonist on basal and epidermal growth factor-induced cell proliferation and metastasis-associated properties in human epidermoid carcinoma A431 cells.

The purpose of this study was to investigate the effects of a potent LHRH agonist, [D-Trp(6)]LHRH on the basal and EGF-induced cell proliferation and the metastasis-associated properties in A431 human epidermoid carcinoma. [D-Trp(6)]LHRH time-dependently inhibited the basal and EGF-stimulated growth of A431 cancer cells. It is assumed that phosphorylation/dephosphorylation of cellular proteins is highly related to cell growth.