Claudin-7 inhibits human lung cancer cell migration and invasion through ERK/MAPK signaling pathway

Tight junctions are the most apical component of the junctional complex critical for epithelial cell barrier and polarity functions. Although its disruption is well documented during cancer progression such as epithelial–mesenchymal transition, molecular mechanisms by which tight junction integral membrane protein claudins affect this process remain largely unknown. In this report, we found that claudin-7 was normally expressed in bronchial epithelial cells of human lungs but was either downregulated or disrupted in its distribution pattern in lung cancer. To investigate the function of claudin-7 in lung cancer cells, we transfected claudin-7 cDNA into NCI-H1299, a human lung carcinoma cell line that has no detectable claudin-7 expression. We found that claudin-7 expressing cells showed a reduced response to hepatocyte growth factor (HGF) treatment, were less motile, and formed fewer foot processes than the control cells did. In addition, cells transfected with claudin-7 dramatically decreased their invasive ability after HGF treatment. These effects were mediated through the MAPK signaling pathway since the phosphorylation level of ERK1/2 was significantly lower in claudin-7 transfected cells than in control cells. PD98059, a selective inhibitor of ERK/MAPK pathway, was able to block the motile effect. Claudin-7 formed stable complexes with claudin-1 and -3 and was able to recruit them to the cell-cell junction area in claudin-7 transfected cells. When control and claudin-7 transfected cells were inoculated into nude mice, claudin-7 expressing cells produced smaller tumors than the control cells. Taken together, our study demonstrates that claudin-7 inhibits cell migration and invasion through ERK/MAPK signaling pathway in response to growth factor stimulation in human lung cancer cells.     

Cannabinoids inhibit ethanol-induced activation of liver toxicity in rats through JNK/ERK/MAPK signaling pathways

Cannabinoids (CBs) are psychoactive compounds, with reported anticancer, anti-inflammatory, and anti-neoplastic properties. The study was aimed at assessing the hepatoprotective effects of CB against ethanol (EtOH)-induced liver toxicity in rats. The animals were divided into seven groups: control (Group I) and Group II were treated with 50% ethanol (EtOH 5 mg/kg). Groups III, IV, and VI were treated with (EtOH + CB 10 mg/kg), (EtOH + CB 20 mg/kg), and (EtOH + CB 30 mg/kg), respectively. Groups V and VII consisted of animals treated with 20 and 30 mg/kg, of CB, respectively. Biochemical analysis revealed that Group IV (EtOH + CB 20 mg/kg) had reduced levels of ALT—alanine transferase, AST—aspartate aminotransferase, ALP—alanine peroxidase, MDA—malondialdehyde and increased levels of GSH-reduced glutathione. Histopathological analysis of liver and kidney tissues showed that EtOH + CB (20 and 30 mg/kg) treated animal groups exhibited normal tissue architecture similar to that of the control group. ELISA revealed that the inflammatory markers were reduced in the animal groups that were treated with EtOH + CB 20 mg/kg, in comparison to the animals treated only with EtOH. The mRNA expression levels of COX-2, CD-14, and MIP-2 showed a remarkable decrease in EtOH + CB treated animal groups to control groups. Western blot analysis revealed that CB downregulated p38/JNK/ERK thereby exhibiting its hepatoprotective property by inhibiting mitogen-activated protein kinase pathways. Thus, our findings suggest that CB is a potential candidate for the treatment of alcohol-induced hepatotoxicity.     

CXCL13 mediates prostate cancer cell proliferation through JNK signalling and invasion through ERK activation

Objectives: The focus of this study was to determine the dedicator of cytokinesis 2 (DOCK2), extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase-1 (JNK) and Akt signals involved in CXCL13-mediated prostate cancer (PCa) cell invasion and proliferation. Materials and methods: Androgen-sensitive (LNCaP), hormone-refractory (PC3) cells and normal cells (RWPE-1) were used to determine CXCL13-mediated PCa cell invasion and proliferation. Immuno-blotting, fast activated cell-based (FACE) ELISA, caspase activity, cell invasion and proliferation assays were performed to ascertain some of the signalling events involved in PCa cell proliferation and invasion. Results: Unlike androgen-sensitive LNCaP cells, we report for the first time that the hormone-refractory cell line, PC3, expresses DOCK2. CXCL13-mediated LNCaP and PC3 cell invasion was regulated by Akt and ERK1/2 activation in a DOCK2-independent fashion. CXCL13 also promoted LNCaP cell proliferation in a JNK-dependent fashion even in the absence of DOCK2. In contrast, CXCL13 induced PC3 cell proliferation through JNK activation, which required DOCK2. Conclusions: Our results show CXCL13-mediated PCa cell invasion requires Akt and ERK1/2 activation and suggests a new role for DOCK2 in proliferation of hormone-refractory CXCR5-positive PCa cells.     

TGF-β promotes invasion and metastasis of gastric cancer cells by increasing fascinl expression via ERK and JNK signal pathways

Transforming growth factor-β（TGF-β） is involved in actin cytoskeleton reorganization and tumor progression. Fascinl, an actin-binding protein, increases cell invasiveness and motility in various transformed cells. To determine whether fascinl is an important mediator of the tumor response to TGF-β, we applied the small interfering RNA （siRNA） technique to silence fascinl in gastric cancer （GC） cells MKN45. Results showed that the effects of TGF-β1 on GC cells invasion and metastasis were mediated by tumor production of fascinl; furthermore, it was found that TGF-β1- induced fascinl expression was suppressed by the specific inhibitors of JNK and ERK pathways, SP6001125 and PD98059, respectively, but not by transient transfection of Smad2 and Smad4 siRNA. Our data for the first time demonstrated that fascin 1 is an important mediator of TGF-β1-induced invasion and metastasis of GC cells, which involves JNK and ERK signaling pathways.     

CXCR4 promotes oral squamous cell carcinoma migration and invasion through inducing expression of MMP-9 and MMP-13 via the ERK signaling pathway

The increased migration and invasion of oral squamous cell carcinoma cells are key events in the development of metastasis to the lymph nodes and distant organs. Although the chemokine receptor CXCR4 and its ligand, stromal cell-derived factor-1α, have been found to play an important role in tumor invasion, its precise role and potential underlying mechanisms remain largely unknown. In this study, we showed that knockdown of CXCR4 significantly decreased Tca8113 cells migration and invasion, accompanied with the reduction of MMP-9 and MMP-13 expression. Inhibition of ligand binding to CXCR4 by a specific antagonist TN14003, also led to reduced cancer cell migration and invasion. Because the degradation of the extracellular matrix and the basement membrane by proteases, such as matrix metalloproteinases (MMP) is critical for migration and invasion of cancer cells, we investigated the expression of several MMPs and found that the expression of functional MMP-9 and MMP-13 was selectively decreased in CXCR4 knockdown cells. More importantly, decreased cell migration and invasion of CXCR4 knockdown cells were completely rescued by exogenous expression of MMP-9 or MMP-13, indicating that the two MMPs are downstream targets of CXCR4-mediated signaling. Furthermore, we found the level of phosphorylated extracellular signal-regulated kinase (ERK) was significantly decreased in CXCR4-silenced cells, suggesting that ERK may be a potential mediator of CXCR4-regulated MMP-9 and MMP-13 expression in Tca8113 cells. Taken together, our results strongly suggest the underlying mechanism of CXCR4 promoting Tca8113 migration and invasion by regulating MMP-9 and MMP-13 expression perhaps via activation of the ERK signaling pathway.     

Coordinating ERK/MAPK signalling through scaffolds and inhibitors

The pathway from Ras through Raf and MEK (MAPK and ERK kinase) to ERK/MAPK (extracellular signal-regulated kinase/mitogen-activated protein kinase) regulates many fundamental cellular processes. Recently, a number of scaffolding proteins and endogenous inhibitors have been identified, and their important roles in regulating signalling through this pathway are now emerging. Some scaffolds augment the signal flux, but also mediate crosstalk with other pathways; certain adaptors target MEK-ERK/MAPK complexes to subcellular localizations; others provide regulated inhibition. Computational modelling indicates that, together, these modulators can determine the dynamic biological behaviour of the pathway.     

Neurotrophin3 promotes hepatocellular carcinoma apoptosis through the JNK and P38 MAPK pathways

Although liver cancer is a malignant tumor with the highest mortality across the world, its pathogenesis and therapeutic targets remain unclear. Apoptosis, a natural cell death mechanism, is an important target of anticancer therapy. The discovery of effective apoptotic regulators can lead to the identification of novel therapeutic targets for treating cancer. Neurotrophin 3 (NTF3) is a member of the nerve growth factor (NGF) family that is involved in the progression of various cancers, including medulloblastoma, primitive neuroectodermal brain tumors, and breast cancer. NTF3 is under-expressed in human hepatocellular carcinoma (HCC), albeit its specific effects and the action mechanism have not been elucidated. Here, we confirmed that NTF3 expression was significantly low in HCC with reference to the GSEA database. By collecting patient data from our center and performing qRT-PCR analysis, we found that NTF3 expression was significantly downregulated in 74 patients with HCC. Low NTF3 expression was associated with a shorter overall survival (OS), recurrence-free survival (RFS), progression-free survival (PFS), and disease-specific survival (DSS). Both in vivo and in vitro experiments revealed that NTF3 considerably inhibited the progression of HCC cells. We found that the ligand NTF3 is regulated by c-Jun and binds to the p75 neurotrophin receptor (p75NTR) and then activates the JNK and P38 MAPK pathways to induce apoptosis. Entinostat (the target of HDAC1/HDAC3) can activate the NTF3/p75NTR pathway. These results indicate that NTF3 is a tumor suppressor, and that its low expression can help in predict poor clinical outcomes in HCC. Therefore, NTF3 can be used as a potential treatment molecule for HCC.     

Histamine enhances cytotrophoblast invasion by inducing intracellular calcium transients through the histamine type-1 receptor

Blastocyst implantation and placentation require molecular and cellular interactions between the uterine endometrium and blastocyst trophectoderm. Previous studies showed that histamine produced in the mouse uterine luminal epithelium interacts with trophoblast histamine type-2 receptors (H2) to initiate blastocyst implantation. However, it is unknown whether similar histamine activity is operative in humans. Using a human cell line (HTR-8/SVneo) derived from first-trimester cytotrophoblasts that expresses both histamine type-1 receptor (H1) and H2, we found that histamine promotes cytotrophoblast invasiveness specifically through activation of H1. Stimulation of H1 in human cytotrophoblasts by histamine induced intracellular Ca2+ (Ca(2+)i) transients by activating phospholipase C and the inositol trisphosphate pathway. The enhanced invasion induced by histamine was blocked by pretreatment with H1 antagonist or by chelation of Ca(2+)i. These findings suggest possible differences between rodents and humans in histamine signaling to the trophoblast.     

Endoplasmic reticulum stress-induced hepatic stellate cell apoptosis through calcium-mediated JNK/P38 MAPK and Calpain/Caspase-12 pathways

Since ischemic heart disease (IHD) is a major cause of mortality and heart failure, novel therapeutic strategies are expected to improve the clinical outcomes of patients with acute myocardial infarction. Brief episodes of ischemia/reperfusion performed at the onset of reperfusion can reduce infarct size; a phenomenon termed “ischemic postconditioning.” Extensive research has determined that different autacoids (e.g., adenosine, bradykinin, opioid, etc.) and cytokines, their respective receptors, kinase signaling pathways, and mitochondrial modulation are involved in ischemic conditioning. Modification of these factors by pharmacological agents mimics the cardioprotection by ischemic postconditioning. Here, the potential mechanisms of ischemic postconditioning, the presence of comorbidities, and the possible extrapolation to the clinical setting are reviewed. In the near future, large, multicentered, randomized, placebo-controlled, clinical trials will be required to determine whether pharmacological and/or ischemic postconditioning can improve the clinical outcomes of patients with IHD.     

Dihydroartemisinin induces apoptosis in human gastric cancer cell line BGC-823 through activation of JNK1/2 and p38 MAPK signaling pathways

Dihydroartemisinin (DHA), a semi-synthetic derivative of artemisinin, is associated with a broad range of biological properties including antitumor activity. However, the effect of DHA on gastric cancer has not been clearly clarified. The aim of this study was to investigate the role and mechanism of DHA in human gastric cancer cell line BGC-823. Cell viability was assessed by MTT assay. Cell apoptosis was analyzed with flow cytometry. The expressions of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (p38 MAPK) and their phosphorylated forms as well as apoptosis related proteins were examined by western blot analysis. The results demonstrated that DHA inhibited cell viability of BGC-823 cells in a dose- and time-dependent manner. DHA treatment upregulated the expression of Bax, cleaved caspase-3 and -9, and degraded form of PARP, and downregulated the Bcl-2 expression and Bcl-2/Bax ratio. Meanwhile, DHA increased the phosphorylation of ERK1/2, JNK1/2 and p38 MAPK. Synthetic inhibitors of JNK1/2 or p38 MAPK kinase activity, but not inhibitor of ERK1/2, significantly abolished the DHA-induced activation of caspase-3 and -9. In vivo tumor-suppression assay further indicated that DHA displayed significant inhibitory effect on BGC-823 xenografts in tumor growth. These results indicate that DHA induces apoptosis of BGC-823 cells through JNK1/2 and p38 MAPK signaling pathways and DHA could serve as a potential additional chemotherapeutic agent for treatment of gastric cancer.