Fas-mediated apoptosis and expression of related genes in human malignant hematopoietic cells

Investigation of the Relation Between FAS, FASLG Polymorphisms and Serum Fas, FasL Levels in Patients with Psoriasis

Background: Psoriasis is a multifactorial and inflammatory chronic skin disease indicated with T-cell-mediated keratinocyte hyper-proliferation. Demographic, epidemiological (family, twin), serological, and genetic studies have clearly demonstrated that psoriasis is a polygenic and multifactorial disease.

Aim: The objectives of the study are; to determine the prevalence of the polymorphisms of FAS (Fas cell surface receptor gene) -671 A>G (rs:1800682) and FASLG (Fas ligand gene) -844 T>C (rs:763110), to investigate the serum levels of sFas and sFasL, and also to discover any relationship between gene polymorphisms and serum levels in psoriatic patients.

Material and Methods: 50 treated and 69 untreated patients, and 140 healthy controls were included in the study. Polymorphisms were determined using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. The serum levels were measured in randomly selected treated (39) and untreated (40) patients, also in 84 healthy controls using micro-ELISA technique.

Results: There was no statistical difference between polymorphisms in the patient and control groups. However, sFas and sFasL levels in both treated and untreated patients were higher than that of the controls.

Conclusion: The investigated FAS and FASLG polymorphisms were not found to be directly associated with the psoriasis. Elevated sFas and sFasL levels in psoriatic patients showed that these factors may possess a significant role in the pathogenesis of psoriasis.

Fas-associated phosphatase 1 mediates Fas resistance in myeloid progenitor cells expressing the Bcr-abl oncogene

The interferon consensus sequence binding protein (Icsbp) is a transcription factor that influences multiple aspects of myelopoiesis. Expression of Icsbp is decreased in the bone marrow of human subjects with chronic myeloid leukemia (CML), and studies in murine models suggest that Icsbp functions as an anti-oncogene for CML. We previously identified a set of Icsbp target genes that may contribute to this anti-oncogene effect. The set includes PTPN13, the gene encoding Fas-associated phosphatase 1 (Fap1, a Fas antagonist). We previously demonstrated that myeloid progenitor cells from Icsbp-knockout mice exhibit Fap1-dependent Fas resistance. In the present study, we determined that the Fas resistance of Bcr-abl+cells is Icsbp- and Fap1-dependent. We also found that treatment of Bcr-abl bone marrow cells with a Fap1-blocking peptide prevents in vitro selection of a tyrosine kinase inhibitor (TKI)-resistant population. Therefore, these results have implications for therapeutic targeting of the Fas-resistant leukemia stem cell population and addressing TKI resistance in CML.

A functional variant in the core promoter of the CD95 cell death receptor gene predicts prognosis in acute promyelocytic leukemia

Up to 15% of acute promyelocytic leukemia (APL) patients fail to achieve or maintain remission. We investigated a common G > A polymorphism at position -1377 (rs2234767) in the core promoter of the CD95 cell death receptor gene in 708 subjects with acute myeloid leukemia, including 231 patients with APL. Compared with the GG genotype, carrier status for the -1377A variant was associated with a significantly worse prognosis in APL patients. Carriers were more likely to fail remission induction (odds ratio = 4.22; 95% confidence interval, 1.41-12.6, P = .01), were more likely to die during the first 8 weeks of remission induction therapy (hazard ratio = 7.26; 95% confidence interval, 2.39-22.9, P = .0005), and had a significantly worse 5-year overall survival (odds ratio = 2.14; 95% confidence interval, 1.10-4.15, P = .03). The -1377A variant destroys a binding site for the SP1 transcriptional regulator and is associated with lower transcriptional activity of the CD95 promoter. Identifying patients at high risk of life-threatening events, such as remission induction failure, is a high priority in APL, especially because such events represent a major cause of death despite the introduction of differentiation therapy.

The interferon consensus sequence binding protein (ICSBP/IRF8) activates transcription of the FANCF gene during myeloid differentiation

The interferon consensus sequence binding protein (ICSBP) is an interferon regulatory transcription factor with leukemia-suppressor activity. ICSBP regulates genes that are involved in phagocyte function, proliferation, and apoptosis. In murine models ICSBP deficiency results in a myeloproliferative disorder (MPD) with increased mature neutrophils. Over time this MPD progresses to acute myeloid leukemia (AML), suggesting that ICSBP deficiency is adequate for MPD, but additional genetic lesions are required for AML. The hypothesis of these studies is that dysregulation of key target genes predisposes to disease progression under conditions of decreased ICSBP expression. To investigate this hypothesis, we used chromatin co-immunoprecipitation to identify genes involved the ICSBP-leukemia suppressor effect. In the current studies, we identify the gene encoding Fanconi F (FANCF) as an ICSBP target gene. FancF participates in a repair of cross-linked DNA. We identify a FANCF promoter cis element, which is activated by ICSBP in differentiating myeloid cells. We also determine that DNA cross-link repair is impaired in ICSBP-deficient myeloid cells in a FancF-dependent manner. This effect is observed in differentiating cells, suggesting that ICSBP protects against the genotoxic stress of myelopoiesis. Decreased ICSBP expression is found in human AML and chronic myeloid leukemia during blast crisis (CML-BC). Our studies suggest that ICSBP deficiency may be functionally important for accumulation of chromosomal abnormalities during disease progression in these myeloid malignancies.

Caspase-8 dependent apoptosis induction in malignant myeloid cells by TLR stimulation in the presence of IFN-alpha

Pro-apoptotic signalling upon toll-like receptor (TLR) stimulation in myeloid cells is normally antagonized by the simultaneous activation of anti-apoptotic pathways. We have previously reported that IFN-alpha can sensitize human monocytes to apoptosis induction by lipopolysaccharide (LPS). Based on these results we investigated whether similarly apoptosis can be cooperatively induced in myeloid tumor cells. When testing established acute myeloid leukemia (AML) cell lines we found the monocytic cell line THP-1 to be sensitive to IFN-alpha plus LPS induced apoptosis, which was partially dependent on caspase-8 and was associated with an enhanced expression of Fas/CD95. We extended our study to 29 short term blast lines from patients with AML and observed additive effects of IFN-alpha and LPS on cell death only with few samples indicating that sensitivity to IFN-alpha plus LPS inducible apoptosis is present in a fraction of AML samples only with no obvious correlation with certain FAB phenotypes.

Granzyme B induction signalling pathway in acute myeloid leukemia cell lines stimulated by tumor necrosis factor alpha and Fas ligand

Acute myeloid leukemia (AML) cell lines treated by genotoxic agents or by Tumor Necrosis Factor alpha (TNFalpha) acquire potent cytotoxicity towards myeloid cells through activation of granzyme B (GrB)/perforin (PFN) system. Here we first extend this observation to another death receptor activator, Fas Ligand (FasL). Moreover, we analyzed GrB induction signalling pathway in TNFalpha- and FasL-stimulated AML cells. The effects of TNFalpha and FasL on GrB expression were specifically mediated by p38MAPK (Mitogen-activated-protein-kinase) activation. Otherwise, TNFalpha and FasL stimulation led to radical oxygen species (ROS) generation and ASK1 (Apoptosis-signal-regulating-kinase-1) activation. Endogenous activation of ASK1 by either H2O2 or thioredoxin (Trx) reductase inhibition had the same effects as TNFalpha and FasL on GrB up regulation. Altogether, our results suggest that TNFalpha- and FasL-stimulated AML cell lytic induction is regulated by a signalling pathway involving sequentially, ROS generation, Trx oxidation, ASK1 activation, p38MAPK stimulation and GrB induction at mRNA and protein levels.

Involvement of the TNF-α autocrine–paracrine loop, via NF-κB and YY1, in the regulation of tumor cell resistance to Fas-induced apoptosis

Many tumors are resistant to Fas ligand (FasL)-induced apoptosis. This study examined the role of tumor-derived TNF-alpha, via an autocrine/paracrine loop, in the regulation of tumor-cell resistance to FasL-induced apoptosis. We have reported that Fas expression and sensitivity to FasL is negatively regulated by the transcription repressor factor Yin Yang 1 (YY1). Thus, we hypothesized that tumor-derived TNF-alpha induces the activation of NF-kappaB and the transcription repressor YY1, both of which negatively regulate Fas expression and sensitivity to FasL-induced apoptosis. This hypothesis was tested in PC-3 prostate cancer cells which synthesize and secrete TNF-alpha and express constitutively active NF-kappaB and YY1. Treatment of PC-3 cells with TNF-alpha (10 units) resulted in increased NF-kappaB and YY1 DNA-binding activity, upregulation of YY1 expression, downregulation of surface and total Fas expression and enhanced resistance of PC-3 to apoptosis induced by the FasL agonist antibody CH-11. In contrast, blocking the binding of secreted TNF-alpha on PC-3 cells with soluble recombinant sTNF-RI resulted in significant inhibition of constitutive NF-kappaB and YY1 DNA-binding activity, downregulation of YY1 expression, upregulation of Fas expression and sensitization of tumor cells to CH-11-induced apoptosis. The regulation of YY1 expression and activity by NF-kappaB was demonstrated by the use of the NF-kappaB inhibitor Bay 11-7085 and by the use of a GFP reporter system whereby deletion of the YY1-tandem binding site in the promoter significantly enhanced GFP expression. The direct role of YY1 expression in the regulation of PC-3 resistance to CH-11-induced apoptosis was shown in cells transfected with siRNA YY1 whereby such cells exhibited upregulation of Fas expression and were sensitized to CH-11-induced apoptosis. These findings demonstrate that the TNF-alpha autocrine-paracrine loop is involved in the constitutive activation of the transcription factors NF-kappaB and YY1 in the tumor cells and this loop leads to inhibition of Fas expression and resistance to FasL-induced apoptosis. Further, these findings identify new targets such as TNF-alpha, NF-kappaB and YY1, whose inhibition can reverse tumor cell resistance to FasL-mediated apoptosis.

Cytotoxic markers and frequency predict functional capacity of natural killer cells infiltrating renal cell carcinoma

PURPOSE

Renal cell carcinoma harbors high numbers of infiltrating lymphocytes with apparent limited efficacy in tumor control. This study focused on the natural killer (NK) cells infiltrating renal cell carcinoma.

EXPERIMENTAL DESIGN

Tumor-infiltrating lymphocytes (TIL) were isolated from renal cell carcinoma and analyzed for NK cell frequency and phenotype (n = 34). NK cells were enriched and tested for effector function.

RESULTS

Two renal cell carcinoma subtypes were identified, one containing high (>20% of the lymphocyte population, n = 14), the other low (<20%, n = 20), NK cell numbers. NK cells of both groups were noncytolytic ex vivo but differed in CD16 and cytotoxic effector molecule expression as well as in their capacity to acquire cytotoxic activity: The majority of NK cells from tumors with high NK cell content (high NK-TIL) were CD16(bright), whereas few CD16bright NK cells were found in tumors with low NK cell frequencies (low NK-TIL). The CD16 dichotomy correlated with different capacities to develop cytotoxicity after short-term activation with interleukin-2 ex vivo: Low NK-TIL remained noncytolytic against K562 and unresponsive to signals via the activating receptor NKp46 despite expression of receptor and adaptor molecules. In contrast, high NK-TIL acquired cytotoxic function. As described for peripheral CD16bright NK cells, NK cells from high-NK tumors showed high per cell expression of granzyme A, granzyme B, and perforin. NK cells from low NK-TIL resembled CD16(neg/dim) peripheral NK cells with few cytotoxin+ cells and lower expression of perforin.

CONCLUSION

The extent of NK cell infiltration and the expression of markers (CD16 and cytotoxins) predict the functional capacity of NK cells infiltrating renal cell carcinoma and can be used to characterize subgroups of renal cell carcinoma.

Fas-associated phosphatase-1 promotes Fas-mediated apoptosis in human colon cancer cells: novel function of FAP-1

BACKGROUND AND AIM

Fas-associated phosphatase-1 (FAP-1) has been thought as an inhibitor in Fas-mediated apoptosis. Here, we investigated the role of FAP-1 in Fas-mediated apoptosis of human colon cancer cells.

METHOD

The viability of four colon cancer cell lines treated with agonistic anti-Fas antibody was determined using WST-1 assay and cell death detection ELISA. pRc/CMV-FAP-1 was transfected to a FAP-1-negative, Fas-resistant colon cancer cell line SW480 by lipofection and the clones expressing FAP-1 protein were selected by limiting dilution. In the clones, expression of 550 genes was analyzed by cDNA microarrays. Protein expression of FAP-1 and molecules related to apoptosis was examined by western blot.

RESULTS

We obtained two FAP-1 overexpressed clones which were much more susceptible to Fas-mediated apoptosis than control cells. In the clones, caspase 8 and caspase 3 were fully activated by agonistic anti-Fas antibody treatment. Bcl-2 family proteins were not related to the high susceptibility of these clones, because caspase 9 was not activated. Transfection of FAP-1 did not suppress the survival actions of insulin-like growth factor (IGF-1) which enhanced survival signal through Akt phosphorylation. Upregulation in 21 genes and downregulation in 29 genes was revealed by cDNA arrays. We confirmed protein expression of p21 and phosphorylated p21 were much more enhanced in the clones than in control cells.

CONCLUSIONS

Overexpression of FAP-1 enhanced susceptibility to Fas-mediated apoptosis in SW480 and upregulation of p21 may contribute to this phenomenon. Our results indicate a novel function of FAP-1 in Fas-mediated apoptosis of human colon cancer cells.

Distinct Role of Calmodulin and Calmodulin-dependent Protein Kinase-II in Lipopolysaccharide and Tumor Necrosis Factor-α-mediated Suppression of Apoptosis and Antiapoptotic c-IAP2 Gene Expression in Human Monocytic Cells

Exposure of phagocytic cells to bacterial endotoxin (lipopolysaccharide; LPS) or inflammatory cytokines confers antiapoptotic survival signals; however, in the absence of the appropriate stimulus, monocytes are programmed to undergo apoptosis. Macrophage survival may thus influence inflammatory and immune responses and susceptibility to microbial pathogens. Herein, we demonstrate that LPS and the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), enhance monocytic cell survival through the induction of the antiapoptotic c-IAP2 gene in a human promonocytic THP-1 cell line. We also investigated the role of upstream signaling molecules including the mitogen-activated protein kinases, phosphatidylinositol 3-kinase, and the calcium signaling pathways in the regulation of c-IAP2 expression and eventual survival of monocytic cells. Our results suggest that LPS and TNF-alpha-induced c-IAP2 expression was regulated by calmodulin (CaM) through the activation of calmodulin-dependent protein kinase-II (CaMKII). In addition, CaM and CaMKII regulated c-IAP2 expression in LPSand TNF-alpha-stimulated cells through NF-kappaB activation. Moreover, the CaM/CaMKII pathway also regulated LPS- and TNF-alpha-mediated inhibition of apoptosis in these cells. Taken together, these results suggest that LPS- and TNF-alpha-induced c-IAP2 expression and its associated antiapoptotic survival signals in THP-1 cells are regulated selectively by CaM/CaMKII through NF-kappaB activation.

TNFα stimulates NKG2D-mediated lytic activity of acute myeloid leukemic cells

The mechanism by which leukemic cells interfere with normal hematopoiesis remains unclear. We show here that, whereas the leukemic KG1a cells are naturally devoid from cellular cytotoxicity, once activated by TNFalpha, they display cytolytic activity toward various cellular targets including CFU-GM. This mechanism is dependent on stimulation of the granzyme B/perforin system. In addition, KG1a cells expressed the NKG2D receptor and its signal-transducing adaptator DAP 10, which were functional as confirmed by redirected lysis experiments. Interestingly, flow cytometry analysis of 20 samples of patients with acute myeloid leukemia (AML) (FAB M0-M5) revealed the expression of NKG2D (40%) and other natural cytotoxicity receptors (40% for NKp30, 74% for NKp44, 39% for NKp46) by a pool >15% of leukemic cells. Furthermore, CD34+ hematopoietic progenitors undergoing granulomonocytic differentiation expressed NKG2D ligands. Altogether, we propose a model in which, upon stimulation by TNFalpha, leukemic cells may exert cytotoxicity against myeloid progenitors. This finding may have important clinical implications in the context of diseases characterized by TNFalpha accumulation, such as AML or myelodisplasic syndromes.

p21 (Waf1/Cip1) and FasL gene activation via Sp1 and NFkappaB is required for leukemia cell survival but not for cell death induced by diverse stimuli

The molecular mechanisms of the cellular response to different apoptotic effectors are only partially understood. Herein, the role of transcription factors, Sp1 and NFkappaB in differentiation-related and etoposide-induced apoptosis was examined in a number of human leukemia cell lines (HL-60, NB4, HEL, THP-1, K562). This was investigated with respect to the recruitment of one cell-cycle regulating gene, p21 and one cell death gene, FasL. Using electrophoretic mobility shift assay (EMSA), we consistently observed Sp1 and NFkappaB binding activity to the promoter of either gene during cell differentiation and the decrease associated with apoptosis upon long-term treatment with differentiation inducers in HL-60, NB4 and HEL cells. By contrast, Sp1 and NFkappaB binding capacities were lost in all myeloid cell lines undergoing etoposide-induced fast apoptosis. This effect was eliminated by the broad-spectrum caspase inhibitor, benzyloxycarbonyl-valinyl-alaninyl-aspartyl fluoromethylketone, thus restoring transcription factors' binding activity. However, sustained NFkappaB binding to the FasL promoter was noticed in apoptosis undergoing HEL cells treated by etoposide. Our results suggest that p21 and FasL gene activation is required for myeloid leukemia cell survival or maturation but not for cell death via Sp1 and NFkappaB as regulators of these genes. The findings also support the idea of a common mechanism for cellular responses to different apoptotic effectors in malignant hematopoietic cell lines.

Sp1 and NF-kappaB transcription factor activity in the regulation of the p21 and FasL promoters during promyelocytic leukemia cell monocytic differentiation and its associated apoptosis

Treatment of human acute promyelocytic leukemia cells with phorbol 12-myristate 13-acetate (PMA) results in growth arrest and differentiation toward monocytes, which subsequently die by apoptosis. However, the relationship between terminal differentiation and apoptosis remains unclear. Here we have studied Sp1 and nuclear factor kappaB (NF-kappaB) transcription factor activity in controlling promoters of cell cycle-regulating (p21/WAF1/CIP1) and cell death (FasL) genes during monocytic differentiation and apoptosis of the human acute promyelocytic leukemia cell lines NB4 and HL-60. Using the electrophoretic mobility shift assay, we observed that PMA treatment of NB4 cells caused an early response in Sp1 binding to the p21 and FasL promoters at 8 h. The firmly adherent cell phenotype, characteristic of differentiated cells, retained Sp1-binding activity to either promoter, but it was often lost completely in detached, apoptotic cells. The association of Sp1 with the p21 promoter during monocytic differentiation correlated with the levels of expressed p21 in the cytoplasmic fraction, as detected by immunoblotting. In HL-60 cells, very weak or no Sp1 binding to either promoter was observed. Low NF-kappaB affinity for its consensus sites and to the FasL promoter was characteristic of apoptotic cells. The results of this study suggest a positive role of Sp1 and NF-kappaB, as regulators of p21 and FasL genes, in leukemic cell survival and monocytic differentiation and a negative role in apoptotic cell death.

Natural killer cell-mediated basal and interferon-enhanced cytotoxicity against liver cancer cells is significantly impaired under in vivo oxygen conditions

Current immunostimulatory treatment protocols of cancer are often met with little success. Several lines of evidence indicate that the tumour microenvironment may impair the cytotoxic activity of natural killer (NK) cells. In this study, the NK cell-mediated killing of liver-derived cells was investigated at oxygen concentrations conform to those present in the human body at physiological and pathological conditions. The in vivo-relevant oxygen concentrations corresponding to 1, 2 and 6% were compared to those of the ambient air (21%) for their effect on the lysis of four liver-derived cell lines and the highly susceptible K562 cells. Exposure to each of the hypoxic conditions had a significantly inhibitory effect on NK cytotoxicity. Treatment with interferon-alpha (IFN-alpha) in hypoxia enhanced the cytotoxic potential of the NK cells less than it enhanced the cytotoxicity at ambient oxygen conditions. In summary, the oxygen tension profoundly affects both the cytoxic activity of NK cells and their activation by IFN-alpha.

Resistance to Fas-mediated cell death in BeWo and NJG choriocarcinoma cell lines: implications in immune privilege

OBJECTIVE

An immune privileged site occurs when the allogenic tissue grafts have the propensity for prolonged survival in the host tissue. In this context, the survival and proliferation of malignant trophoblasts in the gravid uterus are currently unclear. In a previous study, we documented that Fas and FasL are coexpressed in choriocarcinoma [Gynecol. Oncol. (2003)]. This study was conducted to examine the role of the Fas/FasL pathway in immune privilege of BeWo and NJG choriocarcinoma cells in culture.

METHODS

The ability of anti-Fas mAb (CH-11) to sensitize choriocarcinoma cell lines to Fas-mediated cytotoxicity was assessed by MTT assays. Coculture experiments with Fas-sensitive Jurkat cells were used to demonstrate functional FasL from choriocarcinoma. RT-PCR was used to assess the expression of cFLIP.

RESULTS

The mean cell viability of BeWo and NJG cells declined to about 58 and 63% compared to controls after 72 h of culture in the presence of anti-Fas mAb (CH-11) while the Fas-sensitive Jurkat cells showed viability of only 10%. This resistance to Fas-mediated apoptosis in choriocarcinoma cells is reversed in the presence of cycloheximide (0.5 micro g/ml) which further decreased the viability to 36 and 32%, respectively, at a dose of 300 ng/ml (P < 0.05). The observed resistance to Fas-mediated apoptosis therefore could be attributed to the short-lived endogenous inhibitor, cFLIP as demonstrated by the RT-PCR technique. In coculture experiments, FasL from choriocarcinoma cells induced apoptosis in the Fas-sensitive Jurkat cells, thereby indicating the capacity to evade immune attack.

CONCLUSIONS

Decreased sensitivity to Fas-mediated apoptosis and counterattacking the lymphocytes may impart immune privilege in these malignant trophoblasts for prolonged survival in the host.

Granule-dependent cytolysis of Mycobacterium tuberculosis-infected macrophages by human gammadelta+ T cells has no effect on intracellular mycobacterial viability

One of the most important effector functions of activated gammadelta+ T cells in tuberculosis is their strong cytolytic activity against a variety of target cells, including M. tuberculosis-infected macrophages. In the present study, we investigated the relationship between the mechanism of cytolysis utilized by gammadelta+ CTL and intracellular M. tuberculosis survival using a panel of cytolytic human M. tuberculosis-specific gammadelta+ CTL clones. Cytolysis mediated by the gammadelta+ T-cell clones was found to be Ca2+-dependent, sensitive to Cyclosporin A, and was completely abrogated following Sr2+-induced de-granulation of the gammadelta+ T cell effectors. These data demonstrate that gammadelta+ T-cell-mediated cytoxicity was mediated via the granule exocytosis/perforin pathway. Despite significant cytolytic activity against mycobacteria infected U937 cells, the gammadelta+ CTL clones had no impact on the survival of intracellular M. tuberculosis.