Identification of TGF-β-activated kinase 1 as a possible novel target for renal cell carcinoma intervention

Renal cell carcinoma (RCC) is common renal malignancy within poor prognosis. TGF-β-activated kinase 1 (TAK1) plays vital roles in cell survival, apoptosis-resistance and carcinogenesis through regulating nuclear factor-κB (NF-κB) and other cancer-related pathways. Here we found that TAK1 inhibitors (LYTAK1, 5Z-7-oxozeanol (5Z) and NG-25) suppressed NF-κB activation and RCC cell (786-O and A489 lines) survival. TAK1 inhibitors induced apoptotic cytotoxicity against RCC cells, which was largely inhibited by the broad or specific caspase inhibitors. Further, shRNA-mediated partial depletion of TAK1 reduced 786-O cell viability whiling activating apoptosis. Significantly, TAK1 was over-expressed in human RCC tissues, and its level was correlated with phosphorylated NF-κB. Finally, kinase inhibition or genetic depletion of TAK1 enhanced the activity of vinblastine sulfate (VLB) in RCC cells. Together, these results suggest that TAK1 may be an important oncogene or an effective target for RCC intervention.     

NF-κB mediates the induction of Fas receptor and Fas ligand by microcystin-LR in HepG2 cells

Microcystin-LR (MC-LR) is the most frequent and most toxic microcystin identified. This natural toxin has multiple features, including inhibitor of protein phosphatases 1 and 2A, inducer of oxidative stress, as well as, tumor initiator and promoter. One unique character of MC-LR is this chemical can accumulate into liver after contacting and lead to severe damage to hepatocytes, such as apoptosis. Fas receptor (Fas) and Fas ligand (FasL) system is a critical signaling system initiating apoptosis. In current study, we explored whether MC-LR could induce Fas and FasL expression in HepG2 cells, a well used in vitro model for the study of human hepatocytes. The data showed MC-LR induced Fas and FasL expression, at both mRNA and protein levels. We also found MC-LR induced apoptosis at the same incubation condition at which it induced Fas and FasL expression. The data also revealed MC-LR promoted nuclear translocation and activation of p65 subunit of NF-κB. By applying siRNA to knock down p65 in HepG2 cells, we successfully impaired the activation of NF-κB by MC-LR. In these p65 knockdown cells, we also observed significant reduction of MC-LR-induced Fas expression, FasL expression, and apoptosis. These findings demonstrate that the NF-κB mediates the induction of Fas and FasL as well as cellular apoptosis by MC-LR in HepG2 cells. The results bring important information for understanding how MC-LR induces apoptosis in hepatocytes.     

In mouse embryonic fibroblasts, neither caspase-8 nor cellular FLICE-inhibitory protein (FLIP) is necessary for TNF to activate NF-κB, but caspase-8 is required for TNF to cause cell death, and induction of FLIP by NF-κB is required to prevent it

Binding of TNF to TNF receptor-1 can give a pro-survival signal through activation of p65/RelA NF-κB, but also signals cell death. To determine the roles of FLICE-inhibitory protein (FLIP) and caspase-8 in TNF-induced activation of NF-κB and apoptosis, we used mouse embryonic fibroblasts derived from FLIP and caspase-8 gene-deleted mice, and treated them with TNF and a smac-mimetic compound that causes degradation of cellular inhibitor of apoptosis proteins (cIAPs). In cells treated with smac mimetic, TNF and Fas Ligand caused wild-type and FLIP(-/-) MEFs to die, whereas caspase-8(-/-) MEFs survived, indicating that caspase-8 is necessary for death of MEFs triggered by these ligands when IAPs are degraded. By contrast, neither caspase-8 nor FLIP was required for TNF to activate p65/RelA NF-κB, because IκB was degraded, p65 translocated to the nucleus, and an NF-κB reporter gene activated normally in caspase-8(-/-) or FLIP(-/-) MEFs. Reconstitution of FLIP(-/-) MEFs with the FLIP isoforms FLIP-L, FLIP-R, or FLIP-p43 protected these cells from dying when treated with TNF or FasL, whether or not cIAPs were depleted. These results show that in MEFs, caspase-8 is necessary for TNF- and FasL-induced death, and FLIP is needed to prevent it, but neither caspase-8 nor FLIP is required for TNF to activate NF-κB.     

Induction of apoptosis through extrinsic/intrinsic pathways and suppression of ERK/NF-κB signalling participate in anti-glioblastoma of imipramine

Glioblastomas are the most aggressive type of brain tumour, with poor prognosis even after standard treatment such as surgical resection, temozolomide and radiation therapy. The overexpression of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in glioblastomas is recognized as an important treatment target. Thus, an urgent need regarding glioblastomas is the development of a new, suitable agent that may show potential for the inhibition of extracellular signal-regulated kinase (ERK)/NF-κB–mediated glioblastoma progression. Imipramine, a tricyclic antidepressant, has anti-inflammatory actions against inflamed glial cells; additionally, imipramine can induce glioblastoma toxicity via the activation of autophagy. However, whether imipramine can suppress glioblastoma progression via the induction of apoptosis and blockage of ERK/NF-κB signalling remains unclear. The main purpose of this study was to investigate the effects of imipramine on apoptotic signalling and ERK/NF-κB–mediated glioblastoma progression by using cell proliferation (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide [MTT] assay), flow cytometry, Western blotting, and cell invasion/migration assay analysis in vitro. The ERK and NF-κB inhibitory capacity of imipramine is detected by NF-κB reporter gene assay and Western blotting. Additionally, a glioblastoma-bearing animal model was used to validate the therapeutic efficacy and general toxicity of imipramine. Our results demonstrated that imipramine successfully triggered apoptosis through extrinsic/intrinsic pathways and suppressed the invasion/migration ability of glioblastoma cells. Furthermore, imipramine effectively suppressed glioblastoma progression in vivo via the inhibition of the ERK/NF-κB pathway. In summary, imipramine is a potential anti-glioblastoma drug which induces apoptosis and has the capacity to inhibit ERK/NF-κB signalling.     

Fas/FasL-mediated apoptosis in perinatal murine lungs

Postcanalicular lung development is characterized by a time-specific increase in alveolar epithelial type II cell apoptosis. We have previously demonstrated that, in fetal rabbits, developmental type II cell apoptosis coincides with transient upregulation of the cell death regulator Fas ligand (FasL). The aims of this study were 1) to determine the spatiotemporal patterns of pulmonary apoptosis and Fas/FasL gene expression in the murine model [embryonic day 17 (E17) through postnatal day 5 (P5)], and 2) to investigate the functional involvement of the Fas/FasL system by determining the effect of Fas activation and inhibition on perinatal pulmonary apoptosis. The apoptotic activity of alveolar epithelial type II cells, determined by combined TUNEL labeling and anti-surfactant protein B immunohistochemistry, showed a dramatic increase during the perinatal transition (type II cell apoptotic index <0.1% at E17, 1.5% at P1-P3, and 0.3% at P5). This timing of enhanced type II cell apoptosis coincided with a robust 14-fold increase in Fas mRNA and protein levels and a threefold increase in FasL protein levels; both Fas and FasL immunolocalized to type II and bronchial epithelial cells. In vitro and in vivo exposure of fetal and postnatal murine type II cells to anti-Fas antibody induced a fourfold increase in apoptotic activity that was prevented by administration of a broad-spectrum caspase inhibitor; the pulmonary apoptotic activity of Fas-deficient lpr mice remained unchanged. Conversely, administration of a caspase inhibitor to newborn mice (P1) resulted in marked diminution of pulmonary apoptotic activity. These combined findings strongly implicate the Fas/FasL system as a critical regulator of perinatal type II cell apoptosis. The developmental time dependence of apoptosis-related events in the murine model should facilitate investigations of the regulation of perinatal pulmonary apoptotic gene expression.     

I-κBα depletion by transglutaminase 2 and μ-calpain occurs in parallel with the ubiquitin-proteasome pathway

Transglutaminase 2 (TGase2) is a calcium-dependent, cross-linking enzyme that catalyzes iso-peptide bond formation between peptide-bound lysine and glutamine residues. TGase 2 can activate NF-κB through the polymerization-mediated depletion of I-κBα without IKK activation. This NF-κB activation mechanism is associated with drug resistance in cancer cells. However, the polymers cannot be detected in cells, while TGase 2 over-expression depletes free I-κBα, which raises the question of how the polymerized I-κBα can be metabolized in cells. Among proteasome, lysosome and calpain systems, calpain inhibition was found to effectively increase the accumulation of I-κBα polymers in MCF7 cells transfected with TGase 2, and induced high levels of I-κBα polymers as well in MDA-MB-231 breast cancer cells that naturally express a high level of TGase 2. Inhibition of calpain also boosted the level of I-κBα polymers in HEK-293 cells in case of TGase 2 transfection either with I-κBα or I-κBα mutant (S32A, S36A). Interestingly, the combined inhibition of calpain and the proteasome resulted in an increased accumulation of both I-κBα polymers and I-κBα, concurrent with an inhibition of NF-κB activity in MDA-MB-231 cells. This suggests that μ-calpain proteasome-dependent I-κBα polymer degradation may contribute to cancer progression through constitutive NF-κB activation.     

TCR-induced,PKC-θ-mediated NF-κB activation is regulated by a caspase-8–caspase-9–caspase-3 cascade

It has been documented that caspase-8, a central player in apoptosis, is also crucial for TCR-mediated NF-κB activation. However, whether other caspases are also involved this process is unknown. In this report, we showed that in addition to caspase-8, caspase-9 is required for TCR-mediated NF-κB activation. Caspase-9 induces activation of PKC-θ, phosphorylation of Bcl10 and NF-κB activation in a caspase-3-dependent manner, but it appears that Bcl10 phosphorylation is uncoupled from NF-κB activation. Furthermore, caspase-8 lies upstream of caspase-9 during T cell activation. Therefore, TCR ligation elicits a caspase cascade involving caspase-8, caspase-9 and caspase-3 which initiates PKC-θ-dependent pathway leading to NF-κB activation and PKC-θ-independent Bcl10 phosphorylation which limits NF-kB activity.     

Morusin induces apoptosis and suppresses NF-kappaB activity in human colorectal cancer HT-29 cells

Morusin is a pure compound isolated from root bark of Morusaustralis (Moraceae). In this study, we demonstrated that morusin significantly inhibited the growth and clonogenicity of human colorectal cancer HT-29 cells. Apoptosis induced by morusin was characterized by accumulation of cells at the sub-G₁ phase, fragmentation of DNA, and condensation of chromatin. Morusin also inhibited the phosphorylation of IKK-α, IKK-β and IκB-α, increased expression of IκB-α, and suppressed nuclear translocation of NF-κB and its DNA binding activity. Dephosphorylation of NF-κB upstream regulators PI3K, Akt and PDK1 was also displayed. In addition, activation of caspase-8, change of mitochondrial membrane potential, release of cytochrome c and Smac/DIABLO, and activation of caspase-9 and -3 were observed at the early time point. Downregulation in the expression of Ku70 and XIAP was exhibited afterward. Caspase-8 or wide-ranging caspase inhibitor suppressed morusin-induced apoptosis. Therefore, the antitumor mechanism of morusin in HT-29 cells may be via activation of caspases and inhibition of NF-κB.     

干扰FSCN1基因表达对前列腺癌细胞凋亡、活性氧水平影响的研究

目的探讨干扰FSCN1基因表达对前列腺癌细胞凋亡、活性氧(ROS)水平影响及机制。方法以正常前列腺上皮细胞RWPE-1为对照细胞,通过RT-PCR及Western blot检测前列腺癌LNCaP、DU145和PC-3细胞中FSCN1 mRNA及蛋白表达;以LipofectamineTM 2000为载体,DU145细胞分为si-FSCN1组(靶向抑制FSCN1的小干扰RNAs转染DU145细胞)、阴性对照组(随机序列转染DU145细胞)及空白对照组(未转染的细胞),siRNA转染48 h,Western blot检测FSCN1、PCNA、NF-κB p65、p-NF-κB p65、IKKα和p-IKKα的蛋白表达。CCK8检测细胞活力,流式细胞术检测细胞凋亡率及ROS水平。多组间比较采用单因素方差分析,组间两两比较采用SNK-q检验。结果与RWPE-1细胞比较,LNCaP、DU145和PC-3细胞中FSCN1 mRNA(1比2.561±0.189、7.183±0.882、4.796±0.567、4.796±0.567)及蛋白表达(0.053±0.007比0.217±0.013、0.654±0.058、0.316±0.035)均升高,差异具有统计学意义(P均<0.05)。与阴性对照组比较,si-FSCN1组FSCN1表达(0.473±0.052比0.086±0.010)降低,差异具有统计学意义(P均<0.05)。与si-FSCN1组比较,空白对照组、阴性对照组细胞活力(0.302±0.033比0.787±0.069、0.764±0.063)均升高,凋亡率(24.54﹪±1.47﹪比3.04﹪±0.36﹪、3.28﹪±0.40﹪)和ROS相对荧光强度(90.04±5.73比47.88±3.62、49.62±4.11)均降低,差异具有统计学意义(P均<0.05)。与si-FSCN1组比较,空白对照组、阴性对照组PCNA(0.255±0.032比0.654±0.062、0.631±0.058)、NF-κB p65(0.092±0.011比0.296±0.032、0.318±0.037)、p-NF-κB p65(0.042±0.008比0.155±0.018、0.151±0.016)、IKKα(0.112±0.01比0.172±0.020、0.192±0.023)和p-IKKα的蛋白表达(0.051±0.005比0.102±0.011、0.091±0.009)均升高,Cleaved caspase3蛋白表达(0.206±0.018比0.074±0.009、0.085±0.010)均降低,差异具有统计学意义(P均<0.05)。阴性对照组与空白对照组细胞活力、凋亡率、ROS水平及FSCN1、PCNA、Cleaved caspase3、NF-κB p65、p-NF-κB p65、IKKα和p-IKKα的蛋白表达差异均无统计学意义(P>0.05)。结论干扰FSCN1基因表达可降低前列腺癌细胞活力及诱导凋亡,机制可能与ROS水平升高及NF-κB信号下调有关。     

7-ketocholesterol induces apoptosis in differentiated PC12 cells via reactive oxygen species-dependent activation of NF-κB and Akt pathways

Cholesterol oxidation products formed under the enhanced oxidative stress in the brain are suggested to induce neuronal cell death. However, it is still unknown whether oxysterol-induced apoptosis in neuronal cells is mediated by Akt and NF-κB pathways. We assessed the apoptotic effect of 7-ketocholesterol against differentiated PC12 cells in relation to activation of the reactive oxygen species-dependent nuclear factor (NF)-κB, which is mediated by the Akt pathway. 7-Ketocholesterol induced a decrease in cytosolic Bid and Bcl-2 levels, increase in cytosolic Bax levels, cytochrome c release, caspase-3 activation and upregulation of p53. 7-Ketocholesterol induced an increase in phosphorylated inhibitory κB-α, NF-κB p65 and NF-κB p50 levels, binding of NF-κB p65 to DNA, and activation of Akt. Treatment with Bay 11-7085 (an inhibitor of NF-κB activation) and oxidant scavengers, including N-acetylcysteine, prevented the 7-ketocholesterol-induced formation of reactive oxygen species, activation of NF-κB, Akt and apoptosis-related proteins, and cell death. Results from this study suggest that 7-ketocholesterol may exert an apoptotic effect against PC12 cells by inducing activation of the caspase-8-dependent pathway as well as activation of the mitochondria-mediated cell death pathway, leading to activation of caspases, via the reactive oxygen species-dependent activation of NF-κB, which is mediated by the Akt pathway.     

Activated T cell exosomes promote tumor invasion via Fas signaling pathway

Activated T cells release bioactive Fas ligand (FasL) in exosomes, which subsequently induce self-apoptosis of T cells. However, their potential effects on cell apoptosis in tumors are still unknown. In this study, we purified exosomes expressing FasL from activated CD8(+) T cell from OT-I mice and found that activated T cell exosomes had little effect on apoptosis and proliferation of tumor cells but promoted the invasion of B16 and 3LL cancer cells in vitro via the Fas/FasL pathway. Activated T cell exosomes increased the amount of cellular FLICE inhibitory proteins and subsequently activated the ERK and NF-κB pathways, which subsequently increased MMP9 expression in the B16 murine melanoma cells. In a tumor-invasive model in vivo, we observed that the activated T cell exosomes promoted the migration of B16 tumor cells to lung. Interestingly, pretreatment with FasL mAb significantly reduced the migration of B16 tumor cells to lung. Furthermore, CD8 and FasL double-positive exosomes from tumor mice, but not normal mice, also increased the expression of MMP9 and promoted the invasive ability of B16 murine melanoma and 3LL lung cancer cells. In conclusion, our results indicate that activated T cell exosomes promote melanoma and lung cancer cell metastasis by increasing the expression of MMP9 via Fas signaling, revealing a new mechanism of tumor immune escape.     

蒽贝素(Embelin)通过阻断NF-κB信号通路抑制肝癌细胞Bel-7404生长的研究

蒽贝素(Embelin)是一种X连锁凋亡抑制蛋白(X-linked inhibitor of apoptosis protein, XIAP)的小分子抑制剂,可以抑制XIAP的生成和活性,从而解除XIAP的抗凋亡作用,使凋亡顺利进行．研究了Embelin抑制肝癌细胞Bel-7404增殖的机制．采用不同浓度梯度,通过荧光显微镜、Hochest33342染色、MTT检测、AnnexinⅤ/PI流式细胞术和Western blot分别检测Embelin对Bel-7404细胞的形态学变化、凋亡小体形成、细胞存活率、细胞凋亡水平、凋亡信号转导相关蛋白表达的影响．结果显示,Embelin能明显抑制Bel-7404细胞增殖,并通过激活caspase通路以及阻断NF-κB信号通路诱导Bel-7404细胞凋亡,为进一步利用Embelin进行肝癌治疗的研究打下一定的基础．     

Cell Cycle Effects and Caspase-Dependent and Independent Death of HL-60 and Jurkat Cells Treated with the Inhibitor of NF-6B Parthenolide

The sesquiterpene parthenolide (PRT) is an active component of Mexican-Indian medicinal plants and also of the common herb of European origin feverfew. PRT is considered to be a specific inhibitor of NF-6B. Human leukemic HL-60, Jurkat, and Jurkat IκB·M cells, the latter expressing a dominant-negative IκB· and thus having non-functional NF-6B, were treated with PRT and activation of caspases, plasma membrane integrity, DNA fragmentation, chromatin condensation (probed by DNA susceptibility to denaturation), and changes in cell morphology were determined. As a positive control for apoptosis cells were treated with topotecan (TPT) and H2O2 . At 2–8 μM concentration PRT induced transient cell arrest in G2 and M followed by apoptosis. A narrow range of PRT concentration (2–10 μM) spanned its cytostatic effect, induction of apoptosis and induction of necrosis. In fact, necrotic cells were often seen concurrently with apoptotic cells at the same PRT concentration. Atypical apoptosis was characterized by loss of plasma membrane integrity very shortly after caspases activation. In contrast, a prolonged phase of caspase activation with preserved integrity of plasma membrane was seen during apoptosis induced by TPT or H2O2. Necrosis induced by PRT was also atypical, characterized by rapid rupture of plasma membrane and no increase in DNA susceptibility to denaturation. Using Jurkat cells with inactive NF-κB we demonstrate that cell cycle arrest and the mode of cell death induced by PRT were not caused by inhibition of NF-κB. The data suggest that regardless of caspase activation PRT targets plasma membrane causing its destruction. A caution, therefore, should be exercised in interpreting data of the experiments in which PRT is used with the intention to specifically prevent activation of NF-κB.     

Hyperoxia-induced apoptosis and Fas/FasL expression in lung epithelial cells

Alveolar epithelial apoptosis is an important feature of hyperoxia-induced lung injury in vivo and has been described in the early stages of bronchopulmonary dysplasia (chronic lung disease of preterm newborn). Molecular regulation of hyperoxia-induced alveolar epithelial cell death remains incompletely understood. In view of functional involvement of Fas/FasL system in physiological postcanalicular type II cell apoptosis, we speculated this system may also be a critical regulator of hyperoxia-induced apoptosis. The aim of this study was to investigate the effects of hyperoxia on apoptosis and apoptotic gene expression in alveolar epithelial cells. Apoptosis was studied by TUNEL, electron microscopy, DNA size analysis, and caspase assays. Fas/FasL expression was determined by Western blot analysis and RPA. We determined that in MLE-12 cells exposed to hyperoxia, caspase-mediated apoptosis was the first morphologically and biochemically recognizable mode of cell death, followed by necrosis of residual adherent cells. The apoptotic stage was associated with a threefold upregulation of Fas mRNA and protein expression and increased susceptibility to direct Fas receptor activation, concomitant with a threefold increase of FasL protein levels. Fas gene silencing by siRNAs significantly reduced hyperoxia-induced apoptosis. In murine fetal type II cells, hyperoxia similarly induced markedly increased Fas/FasL protein expression, confirming validity of results obtained in transformed MLE-12 cells. Our findings implicate the Fas/FasL system as an important regulator of hyperoxia-induced type II cell apoptosis. Elucidation of regulation of hyperoxia-induced lung apoptosis may lead to alternative therapeutic strategies for perinatal or adult pulmonary diseases characterized by dysregulated type II cell apoptosis.