Apoptosis, proliferation and NF-kappaB activation induced by agonistic Fas antibodies in the human myeloma cell line OH-2: amplification of Fas-mediated apoptosis by tumor necrosis factor

Pentoxifylline abrogates cardiotoxicity induced by the administration of a single high dose or multiple low doses of doxorubicin in rats

Doxorubicin (DOX) possesses a broad-spectrum antineoplastic activity; however, its clinical application is impeded by cardiotoxicity. This study aimed to investigate the protective effect of pentoxifylline (PXF), which possesses antioxidant and anti-inflammatory properties against cardiotoxicity induced by a single high dose (15 mg/kg, i.p.) or multiple low doses (2.5 mg/kg, i.p., three times per week for 2 weeks) of DOX. At the end of the experimental period, the serum creatine kinase (CK)-MB and lactate dehydrogenase (LDH) activities were measured. The hearts were then removed for evaluating TNF-α, NO, malondialdehyde (MDA), and reduced glutathione (GSH) levels, superoxide dismutase (SOD) and catalase (CAT) activities, and the expression of iNOS, NF-κB, Fas ligand (FasL), and caspase-3. The administration of DOX in both dose regimens caused increases in serum CK-MB and LDH activities, in cardiac TNF-α, NO and MDA levels, as well as in the cardiac expression of iNOS, NF-κB, FasL and caspase-3, whereas it significantly reduced the cardiac GSH level, as well as SOD and CAT activities (P < 0.05). Prophylactic treatment of rats with PXF diminished DOX-induced alterations in theses parameters. Our results warrant the clinical use of PXF as an adjuvant therapy to abrogate cardiotoxicity of DOX and extend its clinical applications.

TNFα sensitizes neuroblastoma cells to FasL-, cisplatin- and etoposide-induced cell death by NF-κB-mediated expression of Fas

BACKGROUND

Patients with high-risk neuroblastoma (NBL) tumors have a high mortality rate. Consequently, there is an urgent need for the development of new treatments for this condition. Targeting death receptor signaling has been proposed as an alternative to standard chemo- and radio-therapies in various tumors. In NBL, this therapeutic strategy has been largely disregarded, possibly because ~50-70% of all human NBLs are characterized by caspase-8 silencing. However, the expression of caspase-8 is detected in a significant group of NBL patients, and they could therefore benefit from treatments that induce cell death through death receptor activation. Given that cytokines, such as TNFα, are able to upregulate Fas expression, we sought to address the therapeutic relevance of co-treatment with TNFα and FasL in NBL.

METHODS

For the purpose of the study we used a set of eight NBL cell lines. Here we explore the cell death induced by TNFα, FasL, cisplatin, and etoposide, or a combination thereof by Hoechst staining and calcein viability assay. Further assessment of the signaling pathways involved was performed by caspase activity assays and Western blot experiments. Characterization of Fas expression levels was achieved by qRT-PCR, cell surface biotinylation assays, and cytometry.

RESULTS

We have found that TNFα is able to increase FasL-induced cell death by a mechanism that involves the NF-κB-mediated induction of the Fas receptor. Moreover, TNFα sensitized NBL cells to DNA-damaging agents (i.e. cisplatin and etoposide) that induce the expression of FasL. Priming to FasL-, cisplatin-, and etoposide-induced cell death could only be achieved in NBLs that display TNFα-induced upregulation of Fas. Further analysis denotes that the high degree of heterogeneity between NBLs is also manifested in Fas expression and modulation thereof by TNFα.

CONCLUSIONS

In summary, our findings reveal that TNFα sensitizes NBL cells to FasL-induced cell death by NF-κB-mediated upregulation of Fas and unveil a new mechanism through which TNFα enhances the efficacy of currently used NBL treatments, cisplatin and etoposide.

Cellular FLICE-like inhibitory protein deviates myofibroblast fas-induced apoptosis toward proliferation during lung fibrosis

A prominent feature of fibrotic tissue in general and of lungs in particular is fibroblast proliferation and accumulation. In patients overcoming fibrosis, apoptosis limits this excessive cell growth. We have previously shown resistance to Fas-induced apoptosis of primary lung fibroblasts from mice with bleomycin-induced lung fibrosis, their escape from immune surveillance, and continued accumulation in spite of overexpression of the Fas death receptor. Cellular FLICE-like inhibitory protein (c-FLIP) is a regulator of cell death receptor-induced apoptosis in many cell types. We aimed to determine c-FLIP levels in myofibroblasts from fibrotic lungs and to directly assess c-FLIP's role in apoptosis and proliferation of primary lung myofibroblasts. c-FLIP levels were determined by apoptosis gene array, flow cytometry, Western blot, and immunofluorescence before and after down-regulation with a specific small interfering RNA. Apoptosis was assessed by caspase cleavage in Western blot and by Annexin V affinity labeling after FACS and tissue immunofluorescence. Proliferation was assessed by BrdU uptake, also using FACS and immunofluorescence. We show that myofibroblasts from lungs of humans with idiopathic pulmonary fibrosis and from bleomycin-treated versus normal saline-treated mice up-regulate c-FLIP levels. Using the animal model, we show that fibrotic lung myofibroblasts divert Fas signaling from apoptosis to proliferation and that this requires signaling by TNF receptor-associated factor (TRAF) and NF-κB. c-FLIP down-regulation reverses the effect of Fas activation, causing increased apoptosis, decreased proliferation, and diminished recruitment of TRAF to the DISC complex. This indicates that c-FLIP is essential for myofibroblast accumulation and may serve as a potential target to manipulate tissue fibrosis.

Bone morphogenetic proteins induce apoptosis in multiple myeloma cells by Smad-dependent repression of MYC

Bone morphogenetic proteins (BMPs) have been shown to induce apoptosis and growth arrest in myeloma cells. However, the molecular mechanisms behind these events are not known. The MYC oncogene is a master regulator of cell growth and protein synthesis and MYC overexpression has been proposed to be associated with the progression of multiple myeloma. Here, we show that BMP-induced apoptosis in myeloma cells is dependent on downregulation of MYC. Moreover, the results suggest that targeting the MYC addiction in multiple myeloma is an efficient way of killing a majority of primary myeloma clones. We also found that myeloma cells harboring immunoglobulin (IG)-MYC translocations evaded BMP-induced apoptosis, suggesting a novel way for myeloma cells to overcome potential tumor suppression by BMPs.

Antioxidant c-FLIP inhibits Fas ligand-induced NF-kappaB activation in a phosphatidylinositol 3-kinase/Akt-dependent manner

Fas ligand (FasL) belongs to the TNF family of death ligands, and its binding to the FasR leads to activation of several downstream signaling pathways and proteins, including NF-κB and PI3K/Akt. However, it is not known whether cross-talk exists between NF-κB and PI3K/Akt in the context of FasL signaling. We demonstrate using both human renal epithelial 293T cells and Jurkat T-lymphocyte cells that although FasL activates both Akt and NF-κB, Akt inhibits FasL-dependent NF-κB activity in a reactive oxygen species-dependent manner. Cellular FLICE-inhibitory protein (c-FLIP), an antioxidant and an important component of the death-inducing signaling complex, also represses NF-κB upstream of the regulatory IκB kinase-γ protein subunit in the NF-κB signaling pathway, and positive cross-talk exists between Akt and c-FLIP in the context of inhibition of FasL-induced NF-κB activity. The presence of two death effector domains of c-FLIP and S-nitrosylation of its caspase-like domain were found to be important for mediating c-FLIP-dependent downregulation of NF-κB activity. Taken together, our study reveals a novel link between NF-κB and PI3K/Akt and establishes c-FLIP as an important regulator of FasL-mediated cell death.

TNFR1 and TNFR2 regulate the extrinsic apoptotic pathway in myeloma cells by multiple mechanisms

The huge majority of myeloma cell lines express TNFR2 while a substantial subset of them failed to show TNFR1 expression. Stimulation of TNFR1 in the TNFR1-expressing subset of MM cell lines had no or only a very mild effect on cellular viability. Surprisingly, however, TNF stimulation enhanced cell death induction by CD95L and attenuated the apoptotic effect of TRAIL. The contrasting regulation of TRAIL- and CD95L-induced cell death by TNF could be traced back to the concomitant NFκB-mediated upregulation of CD95 and the antiapoptotic FLIP protein. It appeared that CD95 induction, due to its strength, overcompensated a rather moderate upregulation of FLIP so that the net effect of TNF-induced NFκB activation in the context of CD95 signaling is pro-apoptotic. TRAIL-induced cell death, however, was antagonized in response to TNF because in this context only the induction of FLIP is relevant. Stimulation of TNFR2 in myeloma cells leads to TRAF2 depletion. In line with this, we observed cell death induction in TNFR1-TNFR2-costimulated JJN3 cells. Our studies revealed that the TNF-TNF receptor system adjusts the responsiveness of the extrinsic apoptotic pathway in myeloma cells by multiple mechanisms that generate a highly context-dependent net effect on myeloma cell survival.

NFκB1 and NFκBIA polymorphisms are associated with increased risk for sporadic colorectal cancer in a southern Chinese population

BACKGROUND

Nuclear factor κB (NFκB) plays a key role in the regulation of apoptosis. The function of NFκB is inhibited by binding to NFκB inhibitor (IκB), and disruption of the balance of NFκB and IκB is related to the development of many diseases, including tumors. Therefore, we hypothesized that the NFκB1 (-94del/insATTG) and NFκBIA (2758 A>G) polymorphisms were associated with colorectal cancer (CRC) susceptibility.

METHODS

In a hospital-based case-control study of 1001 CRC patients and 1005 cancer-free controls frequency matched by age and sex, we genotyped polymorphisms using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method and performed luciferase assays and Western blotting analysis to identify whether genetic variants in NFκBIA alter its gene expressions and functions and thus cancer risk.

RESULTS

We found that both NFκB1-94 ins/delATTG and NFκBIA 2758 A>G polymorphisms were correlated with CRC risk (OR = 1.47; 95%CI = 1.14-1.86, and OR = 1.38; 95% CI = 1.14-1.66, respectively). Furthermore, when evaluated these two polymorphisms together, the combined genotypes with 2 variant (risk) alleles (2758GG and -94ins/ins+del/ins) were associated with an increased risk of CRC (OR = 1.71; 95% CI = 1.23-2.38) compared to 0 variant, and the significant trend for 2 variant (risk) alleles were more pronounced among subgroups of aged <60 years, women, never drinkers, never smokers, persons with a normal BMI and those with a family history of cancer(P(trend)<0.01). Moreover, luciferase assays showed that the G allele in the 3'UTR significantly decreased NFκBIA mRNA stability and the A allele regulation by miRNA449a in vitro and that the NFκBIA protein expression levels of the AA+AG variant carriers were significantly higher in peritumoral tissues than those of the 2758GG genotype.

CONCLUSION

NFκB1 and NFκBIA polymorphisms appear to jointly contribute to risk of CRC. These two variants may be a genetic modifier for CRC susceptibility in this southern Chinese population.

The Fas system confers protection against alveolar disruption in hyperoxia-exposed newborn mice

The functional significance of the Fas/Fas-ligand (FasL) system in hyperoxia-induced lung injury and alveolar disruption in newborn lungs in vivo remains undetermined. To assess the role of the Fas/FasL system, we compared the effects of hyperoxia (95% O2 from birth to Postnatal Day [P]7) in Fas-deficient lpr mice and wild-type mice. Alveolar disruption was more severe in hyperoxic lpr mice than in wild-type mice. In addition, a transient alveolarization defect was noted in normoxic lpr mice. Hyperoxia induced marked up-regulation of pulmonary Fas expression in wild-type mice, as well as elevated mRNA levels of pro-apoptotic Bax, Bad, and Bak. Pulmonary apoptotic activity was similar in hyperoxic wild-type and lpr mice. In contrast, lung growth and proliferation, assessed by stereologic volumetry and Ki67 proliferation studies, were significantly higher in hyperoxic wild-type mice compared with lpr mice, suggesting the Fas/FasL system has a pro-proliferative role in hyperoxic conditions. Levels of the prosurvival MAPkinase, pERK1/2, were significantly higher in hyperoxic wild-type mice compared with lpr mice, while pAkt levels were similar. These data suggest that the primary role of the Fas/FasL system in hyperoxic newborn lungs is pro-proliferative, rather than pro-apoptotic, and likely mediated through a Fas-ERK1/2 pathway. Fas-induced proliferation and lung growth in hyperoxic newborn lungs may counteract, in part, the detrimental effects of apoptosis mediated by non-Fas pathways, such as pro-apoptotic Bax/Bcl-2 family members. The capacity of the Fas/FasL signaling pathway to mediate protective rather than destructive functions in hyperoxic newborn lungs highlights the versatility of this complex pathway.

Nonapoptotic functions of FADD-binding death receptors and their signaling molecules

Death receptors (DRs) are surface receptors that when triggered have the capacity to induce apoptosis in cells by forming the death-inducing signaling complex (DISC). The first protein recruited to form the DISC is the adaptor protein FADD/Mort1. Some members of the DR family, CD95 and the TRAIL receptors DR4 and DR5, directly bind FADD, whereas others, such as TNF receptor I and DR3, initially bind another adaptor protein, TRADD, which then recruits FADD. While all DRs can activate both apoptotic and non-apoptotic pathways, it has been widely assumed that the main physiological role of FADD-binding death receptors is to trigger apoptosis. However, recent work has ascribed multiple non-apoptotic activities to these receptors and/or the signaling components of the DISC.

Correlation of sera TNF-alpha with percentage of bone marrow plasma cells, LDH, beta2-microglobulin, and clinical stage in multiple myeloma

Tumor necrosis factor-alpha (TNF-alpha) is important for function, differentiation, and transformation of B-lymphocytes in multiple myeloma (MM) but can also induce apoptosis of myeloma cells. Based on this opposite effect, it is very crucial to analyze the correlation of the serum level of TNF-alpha with clinical parameters of the patients. In this article, we analyzed 18 MM patients, 48% male and 52% female, with a mean age of 52 yr (range: 35-81 yr), clinical stage I in 21.4%, stage II in 26.4%, and stage III in 52.2% of patients. Patients with advanced clinical stage, presence of osteolysis, and elevated lactate dehydrogenase (LDH) had a significant difference (Mann-Whitney U-test, p < 0.05) in the serum level of TNF-alpha in comparison with those in the early stage, without osteolysis, and normal LDH. The correlation of individual values of TNF-alpha with the percentage of plasma cells in the bone marrow, LDH, beta2-microglobulin, fibrinogen, and sedimentation rate was significant (p < 0.05). However, we have not found a significant correlation between TNF-alpha and concentration of hemoglobin, the number of white blood cells or platelets (p > 0.05). We concluded that our data indicate determination of TNF-alpha as a good parameter for estimation of tumor mass presence, among individual patients with MM, and may by used for monitoring during application of different therapy protocols.

An MMP-2/MMP-9 inhibitor, 5a, enhances apoptosis induced by ligands of the TNF receptor superfamily in cancer cells

Several studies have shown that matrix metalloproteases (MMPs) promote tumor growth, invasion, and metastasis. Consequently, MMP inhibitors have been developed as a new class of anticancer drugs, many of which are in clinical trials. The exact mechanism of the antineoplastic activity of MMP antagonists is unknown. To investigate the mechanism, we hypothesized that MMP inhibitors enhance the actions of apoptosis-inducing agents. To test this hypothesis, we treated breast, melanoma, leukemia, osteosarcoma, and normal breast epithelial cells with (2R)-2-[(4-biphenylsulfonyl)amino]-3-phenylproprionic acid (compound 5a), an organic inhibitor of MMP-2/MMP-9, alone or in combination with TNFalpha or other apoptotic agents. FACS analysis showed that 5a interacted synergistically with ligands of the TNF receptor superfamily, including TNFalpha and TNF receptor-like apoptosis-inducing ligand (TRAIL), and with a Fas-cross-linking antibody (CH11), UV, paclitaxel, thapsigargin, and staurosporin, to induce apoptosis in a cell-type-specific manner. Other MMP inhibitors did not synergize with TNFalpha. Compound 5a did not act directly on the mitochondrion or via changes in protein synthesis. Instead, the mechanism requires ligand-receptor interaction and caspase 8 activation. Investigation of the effect of 5a on tumor growth in vivo revealed that continuous treatment of subcutaneous melanoma with a combination of 5a plus TRAIL reduced tumor growth and angiogenesis in nude mice. Our data demonstrate that 5a possesses a novel proapoptotic function, thus providing an alternative mechanism for its antineoplastic action. These observations have important implications for combination cancer therapy.

Regulation of Fas (CD95)-induced apoptosis by nuclear factor-kappaB and tumor necrosis factor-alpha in macrophages

The APO-1/Fas ligand (FasL) and tumor necrosis factor-alpha (TNF-alpha) are two functionally related molecules that induce apoptosis of susceptible cells. Although the two molecules have been reported to induce apoptosis via distinct signaling pathways, we have shown that FasL can also upregulate the expression of TNF-alpha, raising the possibility that TNF-alpha may be involved in FasL-induced apoptosis. Because TNF-alpha gene expression is under the control of nuclear factor-kappaB (NF-kappaB), we investigated whether FasL can induce NF-kappaB activation and whether such activation plays a role in FasL-mediated cell death in macrophages. Gene transfection studies using NF-kappaB-dependent reporter plasmid showed that FasL did activate NF-kappaB promoter activity. Gel shift studies also revealed that FasL mobilized the p50/p65 heterodimeric form of NF-kappaB. Inhibition of NF-kappaB by a specific NF-kappaB inhibitor, caffeic acid phenylethyl ester, or by dominant expression of the NF-kappaB inhibitory subunit IkappaB caused an increase in FasL-induced apoptosis and a reduction in TNF-alpha expression. However, neutralization of TNF-alpha by specific anti-TNF-alpha antibody had no effect on FasL-induced apoptosis. These results indicate that FasL-mediated cell death in macrophages is regulated through NF-kappaB and is independent of TNF-alpha activation, suggesting the antiapoptotic role of NF-kappaB and a separate death signaling pathway mediated by FasL.

Regulation of CD95 (Fas/APO-1)-induced apoptosis in human chondrocytes

OBJECTIVE

To examine the role of nuclear factor kappaB (NF-kappaB) and caspases 3, 8, and 9 in CD95-mediated apoptosis of normal chondrocytes.

METHODS

First-passage chondrocytes from normal human knee cartilage were stimulated with CD95 antibody, and cell death was determined by annexin V binding and by an enzyme-linked immunosorbent assay. Activation of caspases 3, 8, and 9 was measured by Western blotting, and their role in death signaling was evaluated using caspase-specific small peptide inhibitors. The influence of NF-kappaB was determined by electrophoretic mobility shift assay (EMSA) and proteasome inhibition-dependent blocking of the degradation of inhibitor of NF-kappaB.

RESULTS

Low levels of NF-kappaB activity were detected by EMSA in unstimulated chondrocytes. NF-kappaB activity was increased in response to agonistic CD95 antibody. CD95 antibody-induced apoptosis was potentiated by the proteasome inhibitors MG-132 and PS1, and this was associated with a reduced nuclear translocation of NF-kappaB. Proteasome inhibitors also caused the induction of DNA fragmentation by tumor necrosis factor alpha. Procaspase 3 processing was enhanced by the proteasome inhibitor MG-132. Procaspase 8 was undetectable by immunoblotting in whole cell lysates of chondrocytes, but caspase 8 messenger RNA was detected by reverse transcription-polymerase chain reaction. Furthermore, apoptosis induced by CD95 stimulation and proteasome inhibitors was blocked by the caspase 8-specific inhibitor Ac-IETD-CHO. Processing of procaspase 9 was not observed, and inhibition of CD95-dependent cell death by the caspase 9 inhibitor Ac-LEHD-CHO was not significant.

CONCLUSION

These results suggest that CD95-dependent cell death is enhanced by NF-kappaB inhibition at and/or downstream of caspase 8 activation and that caspase 9 activation is not involved in CD95-mediated apoptosis in chondrocytes.

Bone morphogenetic protein-4 inhibits proliferation and induces apoptosis of multiple myeloma cells

Bone morphogenetic proteins (BMPs) can be isolated from organic bone matrix and are able to initiate de novo cartilage and bone formation. Here it is shown that BMP-4 inhibited DNA synthesis in a dose-dependent manner in 3 IL-6-dependent multiple myeloma (MM) cell lines (OH-2, IH-1, and ANBL-6). In contrast, no effect on DNA synthesis was observed in 3 IL-6-independent MM cell lines (JJN-3, U266, and RPMI 8226). BMP-4 induced cell cycle growth arrest in the G(0)/G(1) phase in OH-2 and ANBL-6 cells but not in IH-1 cells. BMP-4 induced apoptosis in OH-2 and IH-1 cells, but not significantly in ANBL-6 cells. Furthermore, BMP-4 induced apoptosis in freshly isolated MM cells from 4 of 13 patients. In the OH-2 and ANBL-6 cell lines and in a patient sample, immunoblotting showed that BMP-4 down-regulated IL-6-induced tyrosine phosphorylation of Stat3, suggesting a mechanism for the apparent antagonism between IL-6 and BMP-4. BMP-4 or analogues may be attractive therapeutic agents in MM because of possible beneficial effects on both tumor burden and bone disease.

Regulation of Fas-mediated apoptosis by NF-kappaB activity in human hepatocyte derived cell lines

Nuclear Factor-kappaB (NF-kappaB) is known to be one of the key regulators of genes involved in survival signaling. The purpose of this study is to investigate the role of NF-kappaB activity in signaling events related to cell survival in hepatocytes, which has been supposed to be one of the most sensitive organs against Fas-induced cytotoxicity. The functions of NF-kappaB activity on Fas-mediated apoptosis in different human cell lines were investigated by a magnetic concentration system for cells with exogenous protein production. We demonstrated that the activation of NF-kappaB was triggered by anti-Fas treatment in hepatocyte derived cell lines, HepG2 and Huh-7 cells. Overexpression of kinase-inactive NF-kappaB-inducing kinase (NIK) and IkappaB kinase (IKK) inhibited the activation of NF-kappaB introduced by anti-Fas treatment in these cells. Notably, inactivation of NF-kappaB by the production of IkappaB-alpha protein made these cells more susceptible to apoptosis induced by Fas stimulation. In contrast, transient expression of NIK showed a suppressive effect on Fas-mediated apoptosis in the same cell lines. These findings suggest the involvement of NF-kappaB in suppression of Fas-mediated apoptosis in human hepatocyte derived cell lines, in which concomitant activation of this transcriptional factor was observed through the stimulation of Fas signaling.