TNF increases camptothecin-induced apoptosis by inhibition of NF-kappaB

Functional interaction between hMYH and hTRADD in the TNF-α-mediated survival and death pathways of HeLa cells

The tumor necrosis factor (TNF) signaling pathway is a classical immune system pathway that plays a key role in regulating cell survival and apoptosis. The TNF receptor-associated death domain (TRADD) protein is recruited to the death domain of TNF receptor 1 (TNFR1), where it interacts with TNF receptor-associated factor 2 (TRAF2) and receptor-interacting protein (RIP) for the induction of apoptosis, necrosis, nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB), and mitogen-activated protein (MAP) kinase activation. In this study, we found that the human MutY homolog (hMYH) interacted with human TRADD (hTRADD) via the C-terminal domain of hMYH. Moreover, under conditions promoting TNF-α-induced cell death or survival in HeLa cells, this interaction was weakened or enhanced, respectively. The interaction between hMYH and hTRADD was important for signaling pathways mediated by TNF-α. Our results also suggested that the hTRADD-hMYH association was involved in the nuclear translocation of NFκB and formation of the TNFR1-TRADD complex. Thus, this study identified a novel mechanism through which the hMYH-hTRADD interaction may affect the TNF-α signaling pathway.

IMPLICATIONS

In HeLa cells, the hTRADD-hMYH interaction functioned in both cell survival and apoptosis pathways following TNF-α stimulation.

A simple and efficient method to detect nuclear factor activation in human neutrophils by flow cytometry

Neutrophils are the most abundant leukocytes in peripheral blood. These cells are the first to appear at sites of inflammation and infection, thus becoming the first line of defense against invading microorganisms. Neutrophils possess important antimicrobial functions such as phagocytosis, release of lytic enzymes, and production of reactive oxygen species. In addition to these important defense functions, neutrophils perform other tasks in response to infection such as production of proinflammatory cytokines and inhibition of apoptosis. Cytokines recruit other leukocytes that help clear the infection, and inhibition of apoptosis allows the neutrophil to live longer at the site of infection. These functions are regulated at the level of transcription. However, because neutrophils are short-lived cells, the study of transcriptionally regulated responses in these cells cannot be performed with conventional reporter gene methods since there are no efficient techniques for neutrophil transfection. Here, we present a simple and efficient method that allows detection and quantification of nuclear factors in isolated and immunolabeled nuclei by flow cytometry. We describe techniques to isolate pure neutrophils from human peripheral blood, stimulate these cells with anti-receptor antibodies, isolate and immunolabel nuclei, and analyze nuclei by flow cytometry. The method has been successfully used to detect NF-κB and Elk-1 nuclear factors in nuclei from neutrophils and other cell types. Thus, this method represents an option for analyzing activation of transcription factors in isolated nuclei from a variety of cell types.

Irinotecan pharmacogenomics

Irinotecan is a camptothecin analog used as an anticancer drug. Severe, potentially life-threatening toxicities can occur from irinotecan treatment. Although multiple genes may play a role in irinotecan activity, the majority of evidence to date suggests that variation in expression of UGT1A1 caused by a common promoter polymorphism (UGT1A1*28) is strongly associated with toxicity; however, this link is dose dependent. Variations in other pharmacokinetic genes, particularly the transporter ABCC2, also contribute to irinotecan toxicity. In addition, recent studies have shown that pharmacodynamic genes such as TDP1 and XRCC1 can also play a role in both toxicity and response.

Lipopolysaccharide mitagates methamphetamine-induced striatal dopamine depletion via modulating local TNF-alpha and dopamine transporter expression

Systemic lipopolysaccharide (LPS) treatment may affect methamphetamine (MA)-induced nigrostriatal dopamine (DA) depletion. This study was undertaken to determine the critical time window for the protective effects of LPS treatment and the underlying mechanisms. An LPS injection (1 mg/kg) 72 h before or 2 h after MA treatment [three consecutive, subcutaneous injections of MA (10 mg/kg each) at 2-h intervals] diminished the MA-induced DA depletion in mouse striatum. Such an LPS-associated effect was independent of MA-produced hyperthermia. TNF-alpha, IL-1beta, IL-6 expressions were all elevated in striatal tissues following a systemic injection with LPS, indicating that peripheral LPS treatment affected striatal pro-inflammatory cytokine expression. Striatal TNF-alpha expression was dramatically increased at 72 and 96 h after the MA treatment, while such TNF-alpha elevation was abolished by the LPS pretreatment protocol. Moreover, MA-produced activation of nuclear NFkappaB, a transcription factor following TNF-alpha activation, in striatum was abolished by the LPS (1 mg/kg) pretreatment. Furthermore, thalidomide, a TNF-alpha antagonist, treatment abolished the LPS pretreatment-associated protective effects. Pretreatment with mouse recombinant TNF-alpha in striatum diminished the MA-produced DA depletion. Finally, single LPS treatment caused a rapid down-regulation of dopamine transporter (DAT) in striatum. Taken together, we conclude that peripheral LPS treatment protects nigrostriatal DA neurons against MA-induced toxicity, in part, by reversing elevated TNF-alpha expression and subsequent signaling cascade and causing a rapid DAT down-regulation in striatum.

Nuclear factor activation by FcgammaR in human peripheral blood neutrophils detected by a novel flow cytometry-based method

In mammals, neutrophils are the most abundant circulating leukocytes. Neutrophils are short-lived cells presenting at least two important transcriptionally regulated cellular responses, initiated by cell activation: the production of pro-inflammatory cytokines and the inhibition of apoptosis. The study of transcriptionally regulated processes in these cells cannot be approached through conventional reporter gene strategies, as there are currently not available methods for neutrophil transfection. Here we describe a novel flow cytometry-based method that allowed quantification of nuclear factor NF-kappaB activation in neutrophils, in response to FcgammaIIA and FcgammaRIIIB stimulation. The sensitivity of this method allowed the detection of small changes in NF-kappaB activation, due to pharmacological inhibition of receptor-initiated signaling pathways. NF-kappaB activation was also detected by this method in various leukocyte cell lines. In addition, quantification of Fcgamma receptor-initiated nuclear activation of ERK and Elk-1 was successfully achieved through this method. The broad applicability and versatility of this flow cytometry-based method position it as a fast and reliable alternative to traditional methods for analyzing activation of transcription factors in a variety of cell types.

The C-terminal CD47/IAP-binding domain of thrombospondin-1 prevents camptothecin- and doxorubicin-induced apoptosis in human thyroid carcinoma cells

Camptothecin and doxorubicin belong to a family of anticancer drugs that exert cytotoxic effects by triggering apoptosis in various cell types. However there have only been few investigations showing that matricellular proteins like thrombospondin-1 (TSP-1) could be involved in the underlying mechanism of this cytotoxicity. In this report, using Hoechst reagent staining, reactive oxygen species production and caspase-3 activity measurement, we determined that both camptothecin and doxorubicin induced apoptosis in human thyroid carcinoma cells (FTC-133). On the one hand, we demonstrated that camptothecin and doxorubicin inhibited TSP-1 expression mainly occurring at the transcriptional level. On the other hand, drug-induced apoptosis determined by western blot analysis for PARP cleavage and caspase-3 activity measurement, was significantly decreased in presence of exogenous TSP-1. In order to identify the sequence responsible for this effect, we used the CD47/IAP-binding peptide 4N1 (RFYVVMWK), derived from the C-terminal domain of TSP-1, and known to play a role in apoptosis. Thus, in presence of 4N1, camptothecin and doxorubicin-induced pro-apoptotic activity was considerably inhibited. These findings suggest that induction of apoptosis by camptothecin or doxorubicin in FTC-133 cells is greatly dependent by a down-regulation of TSP-1 expression and shed new light on a possible role for TSP-1 in drug resistance.

Cisplatin and TNF-alpha downregulate transcription of Bcl-xL in murine malignant mesothelioma cells

Malignant mesothelioma (MM) is an aggressive and highly chemo-resistant tumour. In this study, we examined cisplatin-induced apoptosis in mouse models of this disease and investigated the role of constitutive and inducible expression of apoptosis related genes in this process. All of the four mouse MM cell lines examined expressed Bax, Bcl-xL, c-Myc, and caspase-3 but not Bcl-2. Cisplatin-induced apoptosis characterised by DNA fragmentation and cell death while caspase-3/7 was activated in 3 of 4 cell lines. Quantitation of basal gene expression showed significant differences but there was no correlation between single genes and cisplatin sensitivity. In the AC29 and AB1 models, both cisplatin and TNF-alpha downregulated Bcl-xL gene expression, indicating that this gene was a common transcriptional target in these cells. The findings of the present study provide insights into apoptotic mechanisms in mesothelioma cells and show similar patterns of gene expression to that reported in the human disease.

Neuroprotection by stem cell factor in rat cortical neurons involves AKT and NFκB

Stem cell factor (SCF) is a highly expressed cytokine in the central nervous system. In the present study, we demonstrate a neuroprotective role for SCF and its tyrosine kinase receptor, c-kit, against camptothecin-induced apoptosis and glutamate excitotoxicity in rat cortical neurons. This protection was blocked by pharmacological or molecular inhibition of either the MEK/ERK or PI3K/Akt signaling pathways. The importance of these pathways was further confirmed by the activation of both ERK, in a MEK-dependent manner, and Akt, via PI3K. Activation of Akt increased the binding of the p50 and p65 subunits of NFkappaB, which was also important for neuroprotection. Akt inhibition prevented NFkappaB binding, suggesting a role for Akt in SCF-induced NFkappaB. Pharmacological inhibition of NFkappaB or dominant negative IkappaB also prevented neuroprotection by SCF. SCF up-regulated the anti-apoptotic genes, bcl-2 and bcl-xL in an NFkappaB-dependent manner. Together, these findings demonstrate a neuroprotective role for SCF in cortical neurons, an effect that was mediated by Akt and ERK, as well as NFkappaB-mediated gene transcription. SCF represents a novel therapeutic target in the treatment of neurodegenerative disease.

Farnesyltransferase inhibitors and human malignant pleural mesothelioma: a first-step comparative translational study

It is known that the potential clinical use of farnesyltransferase inhibitors (FTI) could be expanded to include cancers harboring activated receptor tyrosine kinases. Approximately 70% of malignant pleural mesotheliomas (MPM) overexpress epidermal growth factor receptors (EGFR) and a subset express both EGFR and transforming growth factor alpha (TGF-alpha), suggesting an autocrine role for EGFR in MPM. We checked on MPM cells (10 human cell lines, 11 primary cultures obtained by human biopsies, and 7 short-term normal mesothelial cell cultures) concerning the following: (a) the relative overexpression of EGFR (Western blotting, flow cytometry, immunohistochemistry), (b) the relative expression of EGFR ligands (EGF, amphiregulin, TGF-alpha, ELISA), (c) the relative increase of the activated form of Ras (Ras-bound GTP) after EGF stimulation (Ras activation assay), (d) the efficacy of five different FTIs (HDJ2 prenylation, cell cytotoxicity, and apoptosis using ApopTag and gel ladder). EGFR was overexpressed in MPM cells compared with normal pleural mesothelial cells in equivalent levels as in non-small cell lung cancer cells A459. MPM cells constitutively expressed EGFR ligands; however, Ras activation was attenuated at high EGF concentrations (100 ng/mL). Growth of MPM cells was substantially not affected by treatment with different FTIs (SCH66336, BMS-214662, R115777, RPR-115135, and Manumycin). Among these, BMS-214662 was the only one moderately active. BMS-214662 triggered apoptosis in a small fraction of cells (not higher than 30%) that was paralleled by a slight decrease in the levels of TGF-alpha secreted by treated MPM cells. Our data highlighted the concept that the same signaling pathway can be regulated in different ways and these regulations can differ between different cells of different origin.

Retracted: Tumor necrosis factor enhances SN38-mediated apoptosis in mesothelioma cells

BACKGROUND

Despite the best and most aggressive, often integrated, standard therapeutic approaches for mesothelioma, overall survival remains very poor. The actual failure points out clearly the need for the development of novel therapy. One of the promising paths of experimentation is artificial induction of apoptosis. A therapeutic strategy that relies on the down-regulation of BCL-XL inhibition nuclear factor kappaB (NF-kappaB) with a combination of SN38 and tumor necrosis factor (TNF) was studied in human mesothelioma cell lines (MSTO-221H, IST-MES1, IST-MES2, MPP89, H28, H513, H2052, and H290).

METHODS AND RESULTS

Cell proliferation (clonogenic assay) was inhibited strongly by the combination of TNF and SN38. Examining the persistence of the NF-kappaB complexes using an electrophoretic mobility-shift assay, it appeared that they still were present at 24 hours in TNF-treated cells. In SN38-treated cells, NF-kappaB complexes persisted for 6 hours. In cells that were treated with combined SN38 and TNF, NF-kappaB complexes disappeared quickly and became undetectable at 6 hours. In flow cytometry analysis, only cells that were treated with combined SN38 and TNF demonstrated significant cellular accumulation in the sub-G0-G1 phase, suggesting a specific induction of apoptosis. Morphologic examination (4,6-diamidino-2-phenylindole staining and electron microscopy) and internucleosomal DNA fragmentation (gel ladder) confirmed rigorously the induction of apoptosis.

CONCLUSIONS

Because of NF-kappaB inhibition with the combination of SN38 and TNF, the expression of BCL-XL (both the protein [Western blot analysis] and the mRNA [reverse transcriptase-polymerase chain reaction analysis]) was down-regulated, cytochrome c was released into the cytoplasm, caspase 3 was activated (Western blot analysis), and, consequently, apoptosis was triggered. The authors hope that the results of the current study may contribute to the design and implementation of a novel therapeutic approach that improves patients' responses to treatment for mesothelioma.

Pharmacogenetics of irinotecan toxicity

Irinotecan is an anticancer drug approved in combination therapy for advanced colorectal cancer. Severe, life-threatening toxicities can occur from irinotecan treatment. Although multiple genes may play a role in irinotecan activity, the UDP glycuronosyltransferase 1 family, polypeptide A1 (UGT1A1) enzyme has been strongly associated with toxicity. A common dinucleotide repeat polymorphism in the UGT1A1 promoter region (UGT1A1*28) has been correlated with severe toxicity in cancer patients receiving irinotecan-containing therapy. Prospective screening of patients prior to chemotherapy selection may reduce the frequency of severe toxicities by allowing alternate therapy selections for patients carrying the UGT1A1*28 polymorphism.

Topoisomerase inhibitor camptothecin sensitizes mouse hepatocytes in vitro and in vivo to TNF-mediated apoptosis

Topoisomerases are nuclear enzymes that maintain and modulate DNA structure. Inhibitors of topoisomerases like camptothecin (CPT), etoposide, and others are widely used antitumor drugs that interfere with transcription, induce DNA strand breaks, and trigger apoptosis preferentially in dividing cells. Because transcription inhibitors (actinomycin D, galactosamine, alpha-amanitin) sensitize primary hepatocytes to the cytotoxic action of tumor necrosis factor (TNF), we reasoned whether topoisomerase inhibitors would act similarly. CPT alone was not toxic to primary cultured murine hepatocytes. When incubated with CPT, murine hepatocytes displayed an inhibition of protein synthesis and were thereby rendered sensitive to apoptosis induction by TNF. Apoptosis was characterized by morphology (condensed/fragmented nuclei, membrane blebbing), caspase-3-like protease activity, fragmentation of nuclear DNA, and late cytolysis. Hepatocytes derived from TNF receptor-1 knockout mice were resistant to CPT/TNF-induced apoptosis. CPT treatment completely abrogated the TNF-induced NF-kappa B activation, and mRNA expression of the antiapoptotic factors TNF-receptor associated factor 2, FLICE-inhibitory protein, and X-linked inhibitor of apoptosis protein was also inhibited by CPT. The caspase inhibitors benzyloxycarbonyl-Val-Ala-Asp-(OMe)-fluoromethylketone (zVAD-fmk) and benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-chloromethylketone (zDEVD-fmk), as well as depletion of intracellular ATP by fructose prevented CPT/TNF-induced apoptosis. In vivo, CPT treatment sensitized mice to TNF-induced liver damage. In conclusion, the combination of topoisomerase inhibition and TNF blocks survival signaling and elicits a type of hepatocyte death similar to actinomycin D/TNF or galactosamine/TNF. During antitumor treatment with topoisomerase inhibitors, an impaired immune function often results in opportunistic infections, a situation where the systemic presence of TNF might be critical for the hepatotoxicity reported in clinical topoisomerase inhibitor studies.