Epithelial-mesenchymal transition in human gastric cancer cell lines induced by TNF-α-inducing protein of Helicobacter pylori

Helicobacter pylori strains produce tumor necrosis factor-α (TNF-α)-inducing protein, Tipα as a carcinogenic factor in the gastric epithelium. Tipα acts as a homodimer with 38-kDa protein, whereas del-Tipα is an inactive monomer. H. pylori isolated from gastric cancer patients secreted large amounts of Tipα, which are incorporated into gastric cancer cells by directly binding to nucleolin on the cell surface, which is a receptor of Tipα. The binding complex induces expression of TNF-α and chemokine genes, and activates NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells). To understand the mechanisms of Tipα in tumor progression, we looked at numerous effects of Tipα on human gastric cancer cell lines. Induction of cell migration and elongation was found to be mediated through the binding to surface nucleolin, which was inhibited by the nucleolin-targeted siRNAs. Tipα induced formation of filopodia in MKN-1 cells, suggesting invasive morphological changes. Tipα enhanced the phosphorylation of 11 cancer-related proteins in serine, threonine and tyrosine, indicating activation of MEK-ERK signal cascade. Although the downregulation of E-cadherin was not shown in MKN-1 cells, Tipα induced the expression of vimentin, a significant marker of the epithelial-mesenchymal transition (EMT). It is of great importance to note that Tipα reduced the Young's modulus of MKN-1 cells determined by atomic force microscopy: This shows lower cell stiffness and increased cell motility. The morphological changes induced in human gastric cancer cells by Tipα are significant phenotypes of EMT. This is the first report that Tipα is a new inducer of EMT, probably associated with tumor progression in human gastric carcinogenesis.

Curcumin induces apoptosis and inhibits growth of orthotopic human non-small cell lung cancer xenografts

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality. Curcumin is involved in various biological pathways leading to inhibition of NSCLC growth. The purpose of this study was to evaluate the effect of curcumin on expression of nuclear factor κB-related proteins in vitro and in vivo and on growth and metastasis in an intralung tumor mouse model. H1975 NSCLC cells were treated with curcumin (0-50 μM) alone, or combined with gemcitabine or cisplatin. The effects of curcumin were evaluated in cell cultures and in vivo, using ectopic and orthotopic lung tumor mouse models. Twenty mice were randomly selected into two equal groups, one that received AIN-076 control diet and one that received the same food but with the addition of 0.6% curcumin 14 days prior to cell implantation and until the end of the experiment. To generate orthotopic tumor, lung cancer cells in Matrigel were injected percutaneously into the left lung of CD-1 nude mice. Western blot analysis showed that the expressions of IkB, nuclear p65, cyclooxygenase 2 (COX-2) and p-ERK1/2 were down-regulated by curcumin in vitro. Curcumin potentiated the gemcitabine- or cisplatin-mediated antitumor effects. Curcumin reduced COX-2 expression in subcutaneous tumors in vivo and caused a 36% decrease in weight of intralung tumors (P=.048) accompanied by a significant survival rate increase (hazard ratio=2.728, P=.036). Curcumin inhibition of COX-2, p65 expression and ERK1/2 activity in NSCLC cells was associated with decreased survival and increased induction of apoptosis. Curcumin significantly reduced tumor growth of orthotopic human NSCLC xenografts and increased survival of treated athymic mice. To evaluate the role of curcumin in chemoprevention and treatment of NSCLC, further clinical trials are required.

Antitumor effects of celecoxib in COX-2 expressing and non-expressing canine melanoma cell lines

Cyclooxygenase-2 (COX-2) is a potential target for chemoprevention and cancer therapy. Celecoxib, a selective COX-2 inhibitor, inhibits cell growth of various types of human cancer including malignant melanoma. In dogs, oral malignant melanoma represents the most common oral tumor and is often a fatal disease. Therefore, there is a desperate need to develop additional therapeutic strategies. The purpose of this study was to investigate the anticancer effects of celecoxib on canine malignant melanoma cell lines that express varying levels of COX-2. Celecoxib induced a significant anti-proliferative effect in both LMeC and CMeC-1 cells. In the CMeC cells, treatment of 50 μM celecoxib caused an increase in cells in the G0/G1 and a decreased proportion of cells in G-2 phase. In the LMeC cells, 50 μM of celecoxib led to an increase in the percentage of cells in the sub-G1 phase and a significant activation of caspase-3 when compared to CMeC-1 cells. In conclusion, these results demonstrate that celecoxib exhibits antitumor effects on canine melanoma LMeC and CMeC-1 cells by induction of G1-S cell cycle arrest and apoptosis. Our data suggest that celecoxib might be effective as a chemotherapeutic agent against canine malignant melanoma.

TFIIB-related factor 2 is associated with poor prognosis of nonsmall cell lung cancer patients through promoting tumor epithelial-mesenchymal transition

In this study, we found that increased BRF2 protein expression was prevalent in NSCLC. Overexpression of BRF2 correlated with abnormal expression of E-cadherin, N-cadherin, and snail. Additionally, expression of BRF2 was found to be an independent prognostic factor in NSCLC patients. Furthermore, we showed that targeted knockdown of BRF2 expression could inhibit the migratory and invasive abilities of NSCLC cells and induced loss of the epithelial-mesenchymal transition of NSCLC cells. These results suggested that BRF2 overexpression in tumor tissues is significantly associated with the poor prognosis of NSCLC patients through promoting epithelial-mesenchymal transition (EMT) program.

MMP-7 is upregulated by COX-2 and promotes proliferation and invasion of lung adenocarcinoma cells

Matrix metalloproteinases (MMPs) have been implicated in a variety of pathophysiological conditions, of which MMP-7 is expressed by tumor cells of epithelial and mesenchymal origin. However, the function of MMP-7 in human lung adenocarcinoma (LAC) is unclear. In the present study the expression of MMP-7 in LAC was examined by immunohistochemical assay using a tissue microarray procedure. A loss-of-function experiment was performed to explore the effects and molecular mechanisms of lentiviral vector-mediated MMP-7 siRNA (siMMP-7) on cell proliferation and invasive potential in LAC A549 cells, measured by MTT and Transwell assays, respectively. It was found that, the expression of MMP-7 protein in LAC was significantly increased compared with that in adjacent non-cancerous tissues (ANCT) (76.0% vs 44.0%, P<0.001), and positively correlated with lymph node metastases of the tumor (P=0.014). Furthermore, targeted inhibition of cyclooxygenase-2 (COX-2) by siRNA downregulated the expression of MMP-7 and inhibited invasion of LAC cells, and knockdown of MMP-7 suppressed tumor proliferation and invasion in LAC cells. Taken together, our findings indicate that increased expression of MMP-7 is associated with lymph node metastasis and upregulated by COX-2, and promotes the tumorigenesis of LAC, suggesting that MMP-7 may be a potential therapeutic target for the treatment of cancer.

Anti-tumor activity of non-steroidal anti-inflammatory drugs: cyclooxygenase-independent targets

Non-steroidal anti-inflammatory drugs (NSAIDs) are used extensively for analgesic and antipyretic treatments. In addition, NSAIDs reduce the risk and mortality to several cancers. Their mechanisms in anti-tumorigenesis are not fully understood, but both cyclooxygenase (COX)-dependent and -independent pathways play a role. We and others have been interested in elucidating molecular targets of NSAID-induced apoptosis. In this review, we summarize updated literature regarding cellular and molecular targets modulated by NSAIDs. Among those NSAIDs, sulindac sulfide and tolfenamic acid are emphasized in this review because these two drugs have been well investigated for their anti-tumorigenic activity in many different types of cancer.

The role of EPH receptors in cancer-related epithelial-mesenchymal transition

Erythropoietin-producing hepatoma (EPH) receptors are considered the largest family of receptor tyrosine kinases and play key roles in physiological and pathologic processes in development and disease. EPH receptors are often overexpressed in human malignancies and are associated with poor prognosis. However, the functions of EPH receptors in epithelial-mesenchymal transition (EMT) remain largely unknown. This review depicts the relationship between EPH receptors and the EMT marker E-cadherin as well as the crosstalk between EPH receptors and the signaling pathways involved EMT. Further discussion is focused on the clinical significance of EPH receptors as candidates for targeting in cancer therapeutics. Finally, we summarize how targeted inhibition of both EPH receptors and EMT-related signaling pathways represents a novel strategy for cancer treatment.

TGF-β1 downregulates COX-2 expression leading to decrease of PGE2 production in human lung cancer A549 cells, which is involved in fibrotic response to TGF-β1

Transforming growth factor-ß1 (TGF-β1) is a multifunctional cytokine that is involved in various pathophysiological processes, including cancer progression and fibrotic disorders. Here, we show that treatment with TGF-β1 (5 ng/mL) induced downregulation of cyclooxygenase-2 (COX-2), leading to reduced synthesis of prostaglandin E2 (PGE2), in human lung cancer A549 cells. Treatment of cells with specific inhibitors of COX-2 or PGE2 receptor resulted in growth inhibition, indicating that the COX-2/PGE2 pathway contributes to proliferation in an autocrine manner. TGF-β1 treatment induced growth inhibition, which was attenuated by exogenous PGE2. TGF-β1 is also a potent inducer of epithelial mesenchymal transition (EMT), a phenotype change in which epithelial cells differentiate into fibroblastoid cells. Supplementation with PGE2 or PGE2 receptor EP4 agonist PGE1-alcohol, as compared with EP1/3 agonist sulprostone, inhibited TGF-β1-induced expression of fibronectin and collagen I (extracellular matrix components). Exogenous PGE2 or PGE2 receptor agonists also suppressed actin remodeling induced by TGF-β1. These results suggest that PGE2 has an anti-fibrotic effect. We conclude that TGF-β1-induced downregulation of COX-2/PGE2 signaling is involved in facilitation of fibrotic EMT response in A549 cells.

Ursolic acid simultaneously targets multiple signaling pathways to suppress proliferation and induce apoptosis in colon cancer cells

Ursolic acid (UA), a natural pentacyclic triterpenoid carboxylic acid distributed in medical herbs, exerts antitumor effects and is emerging as a promising compound for cancer prevention and therapy, but its excise mechanisms of action in colon cancer cells remains largely unknown. Here, we identified the molecular mechanisms by which UA inhibited cell proliferation and induced apoptosis in human colon cancer SW480 and LoVo cells. Treatment with UA led to significant inhibitions in cell viability and clone formation and changes in cell morphology and spreading. UA also suppressed colon cancer cell migration by inhibiting MMP9 and upregulating CDH1 expression. Further studies showed that UA inhibited the phosphorylation of Akt and ERK proteins. Pretreatment with an Akt or ERK-specific inhibitor considerably abrogated the proliferation inhibition by UA. UA also significantly inhibited colon cancer cell COX-2 expression and PGE2 production. Pretreatment with a COX-2 inhibitor (celecoxib) abrogated the UA-induced cell proliferation. Moreover, we found that UA effectively promoted NF-κB and p300 translocation from cell nuclei to cytoplasm, and attenuated the p300-mediated acetylation of NF-κB and CREB2. Pretreatment with a p300 inhibitor (roscovitine) abrogated the UA-induced cell proliferation, which is reversed by p300 overexpression. Furthermore, UA treatment induced colon cancer cell apoptosis, increased the cleavage of PARP, caspase-3 and 9, and trigged the release of cytochrome c from mitochondrial inter-membrane space into cytosol. These results indicate that UA inhibits cell proliferation and induces apoptosis in colon cancer cells through simultaneous modulation of the multiple signaling pathways such as MMP9/CDH1, Akt/ERK, COX-2/PGE2, p300/NF-κB/CREB2, and cytochrome c/caspase pathways.