Involvement of ERK1/2/NF-κB signal transduction pathway in TF/FVIIa/PAR2-induced proliferation and migration of colon cancer cell SW620

Our previous study has demonstrated that TF/FVIIa and protease-activated receptor 2 (PAR2) are closely related to the proliferation and migration of colon cancer cell line SW620. However, the detailed signaling cascades and underlying molecular mechanisms remain unclear. This study has investigated whether extracellular signal-regulated kinase 1 and 2 (ERK1/2) and nuclear factor kappaB (NF-κB) signaling pathways are involved in the events. The results revealed that PAR2-activating peptide (PAR2-AP) or FVIIa elicited time-dependent upregulation of ERK1/2 phosphorylation in SW620 cells, and the effect of FVIIa was significantly attenuated by anti-TF antibody. PAR2-AP or FVIIa also increased NF-κB (p65/RelA) levels among cell nuclear proteins and simultaneously decreased IκB-α levels in the cytoplasmic proteins. Such effects of FVIIa can be inhibited with anti-PAR2 or anti-TF antibodies. While ERK1/2 inhibitor (U0126) intervened with the regulatory effects of PAR2-AP and FVIIa on IκB-α/NF-κB (p65/Rel) expression in the cells, NF-κB inhibitor (PDTC) partially blocked the enhancing effects of PAR2-AP and FVIIa on the proliferating and migratory ability of SW620 cells. Furthermore, the regulatory effects of PAR2-AP and FVIIa on expressions of certain proteins (IL-8, caspase-7, and TF) were also significantly abolished by PDTC. Collectively, the data in this study suggest that the interaction between FVIIa and TF induces PAR2 activation, thereby triggers the ERK1/2 and IκB-α/NF-κB signal transduction pathway to regulate the gene expression of IL-8, TF, and caspase-7, and ultimately promotes SW620 cell proliferation and migration.     

Participation of Bcl-2/Bax-α in Glutamate-induced Apoptosis of Human Glioblastoma Cells

Glutamate has been shown to function as a toxic agent in neuronal and glial cells, as well as an excitatory neurotransmitter throughout the central nervous system. In the present study, we examined the effect of increasing glutamate concentration on the induction of apoptosis in the two human glioblastoma cell lines GB-4 and GB-12. Glutamate exposure caused cell death of GB-4 and GB-12 in a dose-dependent manner. The cells were found to die via apoptosis in response to glutamate based on the following criteria: propidium iodide (PI) staining, H–E staining, electron microscopic analysis, and the TdT-mediated dUTP-biotin nick end labeling (TUNEL) method. The glutamate-induced apoptosis appears to involve the modulation of Bcl-2 family gene products such as Bcl-2, Bcl-xL, and Bax-. Both Bcl-2 and Bcl-xL were down-regulated by glutamate at 24 h and further at 48 h. The apoptosis-promoting product p21 Bax- was also down-regulated in GB-12 but slightly up-regulated in GB-4, accompanied by generation of variant form of p18 Bax- in both cell lines. These findings suggest that glutamate toxicity results in cellular death via an apoptotic mechanism which appears to involve the Bcl-2/Bax- molecular complex.     

Activation of Akt/GSK3β and Akt/Bcl-2 signaling pathways in nickel-transformed BEAS-2B cells

The Akt signaling pathway has been implicated in a wide range of cellular functions involving cell survival and proliferation, angiogenesis, metabolism and cell migration. Accumulating evidence suggests that Akt perturbations play an important role in human malignancy. Here, we investigated Akt perturbation in nickel-transformed cells. Chronic treatment of human bronchial epithelial BEAS-2B cells with low doses of nickel chloride resulted in cell transformation demonstrated by anchorage-independent (AI) growth, increased cell growth and alterations of cell growth pattern. Western blot assays show that phosphorylation of Akt at Ser473, but not that of p38, JNK and ERK, was increased in nickel-transformed cells compared with controls. Inhibition of Akt or PI3K by pharmacological or biochemical interference suppressed nickel AI growth and cell growth of transformed cells. Activation of Akt led to inhibition of GSK3β by phosphorylation at Ser9 in nickel-transformed cells. In addition, two major anti-apoptotic proteins of the Bcl family, Bcl-2 and Bcl-XL, were increased in nickel-transformed cells. By employing the small interfering RNA technique (siRNA), our results showed that siRNA Akt attenuated the expression of Bcl-2 and Bcl-XL in nickel-transformed cells, indicating that induction of Bcl-2 and Bcl-XL was likely mediated through Akt. ROS generation was decreased in nickel-transformed cells compared with controls. Moreover, down-regulation of retinoblastoma protein (Rb) was observed in nickel-transformed cells. Taken together, these findings demonstrate that activation of Akt, followed by GSK3β inhibition and Bcl-2, Bcl-XL up-regulation and decrease of ROS generation, along with a synergistic effect of Rb down-regulation may cause apoptosis resistance, contributing to the overall mechanism of nickel carcinogenesis.     

Expression of Toll-like Receptor 2/4 on Alveolar Macrophage in the Model of Total Hepatic Ischemia/Reperfusion Injury in Mice

Objective： To explore the expression and meaning of Toll-like receptor 2/4 in alveolar macrophage during the process of total hepatic ischemia in mice. Methods： BALB/c mice were used in a model of total hepatic ischemia/reperfusion. Alveolar Macrophage were collected at the time point of lh, 6h and 12h by the means of bronchoalveolar lavage （BAL）, and its TLR2/4 mRNA and protein were detected with Flow Cytometry and Real-time PCR. The level of TNF in BAL fluid were measured. The concentration of MPO, the ratio of wet/dry and lung histological scores were used to assess the degrees of lung injuries. Results： At the three time points of hepatic ischemia reperfusion, the expression of TLR2/4 protein of and mRNA were up-regulated and the level of TLR2 was on the rise continually. TLR4 at the time of 6 h reached the peak value （P〈0.01）. The level of TNF-2 in BAL fluid reached the highest point at the time of 6 h （P〈0.01）. The ratio of wet/dry rose continually during hepatic ischemia reperfusion. After 1 h, the level of MPO increased rapidly. Then it reached the peak value during the period of 6 h to 12 h. Conclusion： TLR2/4 on the mice of alveolar macrophage were activated in the process of hepatic ischemia/reperfusion and involved in the injury of lung.     

Overexpression of HER2 signaling to WAVE2–Arp2/3 complex activates MMP-independent migration in breast cancer

The final signal for triggering the formation of lamellipodia that initiate directional migration of mammalian cells is binding of the Wiskott–Aldrich syndrome (WASP)/WASP family verproline-homologous protein 2 (WAVE2) to the actin-related protein 2 and 3 (Arp2/3) complex. This WAVE2–Arp2/3 signal is suggested to be enhanced in some breast cancers, facilitating invasion, and/or metastasis. Here, we demonstrated one cause of the enhanced signal using four breast cancer cell lines (SKBR3, AU565, MCF7, and MDA-MB-231). The WAVE2–Arp2/3 signal was estimated semi-quantitatively by counting the number of lamellipodia expressing both WAVE2 and Arp2 using high-power confocal laser microscopy. Higher expression of the WAVE2–Arp2/3 signal was detected in SKBR3 and AU565, which have HER2 gene amplification, than in the other two cell lines that lack HER2 gene amplification. Trastuzumab suppressed both the formation of lamellipodia and migration in a Boyden chamber experiment in SKBR3 and AU565. When the HER2 gene was transfected into MCF7, the number of both lamellipodia and migrated cells was increased. This enhancement of migration did not occur in the presence of extracellular matrix, and zymographic analysis showed no clear difference between HER2 gene-transfected cells and MCF7 cells. Immunohistochemical analysis of 115 cases of breast cancer revealed that coexpression of WAVE2 and Arp2 was significantly correlated with HER2-overexpression (P < 0.0001). These data indicate that an abnormal signal resulting from HER2 gene amplification activates lamellipodia formation in breast cancer cells, which initiates their metalloproteinase-independent migration.     

Nuclear factor-E2 (Nrf2) is regulated through the differential activation of ERK1/2 and PKC α/βII by Gymnasterkoreayne B

Phytochemicals are well known to have cancer chemopreventive effects by induction of phase II detoxification enzymes including quinone reductase (NQO-1) and glutathione-S-transferases. These detoxification enzymes are commonly regulated by nuclear factor-E2 (Nrf2), which is a representative antioxidant and cytoprotective factor involved in cancer chemoprevention. As one of the known quinone reductase (QR) inducers and Nrf2 activators, Gymnasterkoreayne B (GKB) isolated from Gymnaster (Aster) koraiensis was used to elucidate the upstream signalling pathway for Nrf2 regulation. In this study, we confirmed that GKB significantly increases expression levels of Nrf2 in HCT116 human colon cancer cells. We found the probable mechanism of upstream signalling pathways to activate Nrf2 by GKB. To reveal the pathway that affects Nrf2 translocation by GKB, we examined changes in various kinases in HCT116 cells treated with GKB. We observed that ERK and PKC pathways are particularly involved in the activation of Nrf2 by GKB, followed by translocation of Nrf2 and induction of NQO-1. These results suggest that GKB induces Nrf2 translocation and expression by differential regulation of ERK and PKC pathways in HCT116 cells.     

Efficacy and Safety of Regorafenib With 2/1 Schedule for Patients ≥ 75 Years With Metastatic Colorectal Cancer (mCRC) After Failure of 2 Lines of Chemotherapy

Background

In the CORRECT (patients with metastatic COloRectal Cancer treated with REgorafenib or plaCebo after failure of standard Therapy) trial, regorafenib was proven to extend survival of patients with metastatic colorectal cancer (mCRC) that progressed after all available therapies. Grade 3 to 4 toxicity occurred in 54% of patients, and data on the activity and tolerability of regorafenib in elderly patients were scarce. The aim of this study was to evaluate the efficacy and safety of an alternative schedule, 2-week-on treatment and 1 week-off (2/1 schedule), of regorafenib for elderly patients with mCRC.

Generation and characterization of a monoclonal antibody against importin α7/NPI-2

Many nuclear proteins are transported into the nucleus via the importin α/β-mediated pathway. Importin α comprises a multigene family. In this study, we generated and characterized a rat monoclonal antibody (MAb) 3F8 to importin α7. The antibody was generated by the hybridization of mouse myeloma cells with lymph node cells from an immunized rat. The MAb 3F8 specifically recognized importin α7 among importin α isoforms as evidenced by immunoblotting analysis. Furthermore, MAb 3F8 detected exogenous importin α7 in COS-7 cells by immunofluorescence. This MAb will be useful in the analysis of the isoform-specific function of importin α7.     

Slit2/Robo1 signaling promotes intestinal tumorigenesis through Src-mediated activation of the Wnt/β-catenin pathway

Slit2 is often overexpressed in cancers. Slit2 is a secreted protein that binds to Roundabout (Robo) receptors to regulate cell growth and migration. Here, we employed several complementary mouse models of intestinal cancers, including the Slit2 transgenic mice, the Apc^Min/+ spontaneous intestinal adenoma mouse model, and the DMH/DSS-induced colorectal carcinoma model to clarify function of Slit2/Robo1 signaling in intestinal tumorigenesis. We showed that Slit2 and Robo1 are overexpressed in intestinal tumors and may contribute to tumor generation. The Slit2/Robo1 signaling can induce precancerous lesions of the intestine and tumor progression. Ectopic expression of Slit2 activated Slit2/Robo1 signaling and promoted tumorigenesis and tumor growth. This was mediated in part through activation of the Src signaling, which then down-regulated E-cadherin, thereby activating Wnt/β-catenin signaling. Thus, Slit2/Robo1 signaling is oncogenic in intestinal tumorigenesis.     

RasGRF2 promotes migration and invasion of colorectal cancer cells by modulating expression of MMP9 through Src/Akt/NF-κB pathway

Ras-specific guanine nucleotide-releasing factor 2 (RasGRF2) is a member of the guanine nucleotide exchange factors family which is expressed in a variety of tissues and cancer. However, the role of RasGRF2 in cancer is less reported, especially in colorectal cancer(CRC). Hence, the present study aimed to investigated the function of RasGRF2 and ways in which it affects tumor progression in CRC samples and cell lines. We first measured RasGRF2 mRNA level in 26 paired tumor and nontumor colon tissues after colon cancer surgical resection, and determined RasGRF2 protein level in 97 paired paraffin-embedded colon cancer tissues, and found that levels of RasGRF2 mRNA and protein were increased in colorectal tumor tissues, compared with adjacent non-tumor tissues. We then examined the effects of RasGRF2 knockdown on proliferation, migration and invasion were analyzed in CRC cells (SW480, HCT116 and LS174T). HCT116 cells with RasGRF2 knockdown were injected into the tail vein in nude mice to yield metastatic model, and tumor metastasis was measured as well. We found that knockdown of RasGRF2 in CRC cells reduced their migration and invasion in vitro and metastasis in mice. Furthermore, we explored the underlying molecular mechanism for RasGRF2-mediated CRC migration and invasion. The results showed that knockdown of RasGRF2 in CRC cells impairing the expression of MMP9 and inhibiting the activation of Src/Akt and NF-κB signaling. We conclude that RasGRF2 plays a role in controlling migration and invasion of CRC and modulates the expression of MMP9 through Src/PI 3-kinase and the NF-κB pathways.     

Involvement of PKCα activation in TF/VIIa/PAR2-induced proliferation, migration, and survival of colon cancer cell SW620

Our previous study has demonstrated that protease-activated receptor 2 (PAR2) activation mediated by tissue factor (TF)/VIIa complex triggers the ERK1/2/NF-κB signaling pathway, which further contributes to the proliferation and migration of colon cancer cell line SW620. However, the detailed mechanisms remain unclear. This study was to investigate whether protein kinase Cα (PKCα) is involved in these events and the possible mechanism. The results revealed that PAR2-activating peptide or VIIa could induce time-dependent upregulation of PKCα phosphorylation in SW620 cells and PKCα translocation from the cytoplasm to the perinuclear region and nucleus. The activation of PKCα was sufficient to induce ERK1/2 and NF-κB phosphorylation. The VIIa effect was obviously blocked by both anti-TF and anti-PAR2 antibodies. The PKCα inhibitor, safingol, inhibited ERK1/2 phosphorylation and NF-κB activation that is induced by VIIa and abrogated the enhanced proliferation, migration, and survival of SW620 cells by VIIa treatment. Both safingol and PDTC (NF-κB inhibitor) could apparently rescue the effects of VIIa on expression of MMP-9, caspase-3, TF, and Bcl-2/bax in SW620 cells. Collectively, the data in this study suggest that TF/VIIa/PAR2-induced SW620 cell proliferation, migration, and survival are ascribed to the activation of PKCα, and these effects are achieved through PKCα downstream signaling pathways, ERK1/2 and NF-κB.     

The role of DNA synthesis inhibition in the cytotoxicity of 2′,2′-difluoro-2′-deoxycytidine

Purpose Cytotoxicity from the anticancer drug 2,2-difluoro-2-deoxycytidine (dFdCyd) has been correlated with its incorporation into DNA. However, cytotoxicity may also result from inhibition of DNA synthesis, due to either (1) dFdCyd diphosphate-mediated inhibition of ribonucleotide reductase, or (2) direct inhibition of DNA polymerases by the 5-triphosphate of dFdCyd (dFdCTP). To elucidate the role of DNA synthesis inhibition in the cytotoxicity of dFdCyd, we compared dFdCyd to hydroxyurea (HU), a ribonucleotide reductase inhibitor, and aphidicolin, an inhibitor of DNA polymerases, in the U251 and D54 human glioblastoma cell lines.Methods Sensitivity to dFdCyd, HU, and aphidicolin were determined using a colony formation assay. The effects of these drugs on DNA synthesis were measured by dual parameter flow cytometry, while the effects on nucleotide pool levels were analyzed by high-performance liquid chromatography.Results HU and aphidicolin elicited substantially less cytotoxicity than the multi-log killing with dFdCyd. When used at equitoxic concentrations (24-h IC₅₀ values), dFdCyd and HU decreased purine dNTP pools primarily, but dFdCyd was less effective than HU. dFdCyd had decreased dATP by about 80% after 4–12 h, and required 8–24 h to decrease DNA synthesis by 50%. In contrast, HU rapidly depleted dATP by >98% within 2 h, which resulted in >90% inhibition of DNA synthesis. Aphidicolin at a concentration similar to its K_i values for DNA polymerases (1 M) decreased DNA synthesis by >70% within 2 h. However, this decreased cell survival by only 10% (U251 cells) and 40% (D54 cells).Conclusions These results demonstrate that HU and aphidicolin produced a more rapid and profound inhibition of DNA synthesis than dFdCyd, but resulted in significantly less cytotoxicity. This suggests that inhibition of DNA synthesis accounted for less than one log of the multi-log cytotoxicity observed with dFdCyd, whereas incorporation of dFdCTP into DNA is a more lethal event.     

Anti-angiogenic effects of differentiation-inducing factor-1 involving VEGFR-2 expression inhibition independent of the Wnt/β-catenin signaling pathway

Background  

Differentiation-inducing factor-1 (DIF-1) is a putative morphogen that induces cell differentiation in Dictyostelium discoideum. DIF-1 inhibits proliferation of various mammalian tumor cells by suppressing the canonical Wnt/β-catenin signaling pathway. To assess the potential of a novel cancer chemotherapy based on the pharmacological effect of DIF-1, we investigated whether DIF-1 exhibits anti-angiogenic effects in vitro and in vivo.