Soluble Fas/APO-1 in tumor cells: a potential regulator of apoptosis?

Tumor necrosis factor superfamily signaling: life and death in cancer

Immune checkpoint inhibitors have shaped the landscape of cancer treatment. However, many patients either do not respond or suffer from later progression. Numerous proteins can control immune system activity, including multiple tumor necrosis factor (TNF) superfamily (TNFSF) and TNF receptor superfamily (TNFRSF) members; these proteins play a complex role in regulating cell survival and death, cellular differentiation, and immune system activity. Notably, TNFSF/TNFRSF molecules may display either pro-tumoral or anti-tumoral activity, or even both, depending on tumor type. Therefore, TNF is a prototype of an enigmatic two-faced mediator in oncogenesis. To date, multiple anti-TNF agents have been approved and/or included in guidelines for treating autoimmune disorders and immune-related toxicities after immune checkpoint blockade for cancer. A confirmed role for the TNFSF/TNFRSF members in treating cancer has proven more elusive. In this review, we highlight the cancer-relevant TNFSF/TNFRSF family members, focusing on the death domain-containing and co-stimulation members and their signaling pathways, as well as their complicated role in the life and death of cancer cells.

Hypoxia alters splicing of the cancer associated Fas gene

The removal of introns from mRNA precursors (pre-mRNAs) is an essential step in eukaryotic gene expression. The splicing machinery heavily contributes to biological complexity and especially to the ability of cells to adapt to altered cellular conditions. Hypoxia also plays a key role in the pathophysiology of many disease states. Recent studies have revealed that tumorigenesis and hypoxia involve large-scale alterations in alternative pre-mRNA splicing. Cancer associated Fas protein plays a central role in the physiological regulation of programmed cell death and has been implicated in the pathogenesis of various malignancies and diseases of the immune system. Fas pre-mRNA is alternatively spliced by excluding exon 6 to produce soluble Fas (sFas) protein that lacks a transmembrane domain and acts by inhibiting Fas mediated apoptosis. Another cancer related protein Rac1 plays an important regulatory role specifically in cells' motility, growth and survival. Rac pre-mRNA is alternatively spliced to produce Rac1b protein, which is upregulated in metastatic diseases. In the present study we, for the first time, show that anti-apoptotic Fas mRNA isoform formation is regulated by cellular microenvironment - hypoxia. Hypoxic microenvironment, however, does not influence Rac1 pre-mRNAs alternative splicing. Also our presented results indicate that splicing factors hnRNP A1 and SPF45, previously shown to regulate Fas alternative splicing in normoxic cells, are not involved in hypoxia dependent alternative Fas pre-mRNA splicing regulation in an amount dependent manner. Our observations on hypoxia dependent alternative Fas pre-mRNA splicing regulation indicate a probable involvement of other, yet unidentified splicing factors. Presented data also shows the contribution of pre-mRNA splicing to cell survival under unfavorable conditions.

FAS promoter polymorphisms and serum sFas level are associated with increased risk of nerve damage in Bangladeshi patients with Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an autoimmune disorder of the peripheral nervous system triggered by molecular mimicry between pathogen lipopolysaccharides and host nerve gangliosides. Polymorphisms in the Fas receptor (FAS) and Fas ligand (FASL) genes may potentially alter the elimination of autoreactive immune cells and affect disease susceptibility or disease severity in GBS. We detected single nucleotide polymorphisms (SNPs) in FAS (-1377G/A and -670A/G) and FASL (-843C/T) in a prospective cohort of 300 patients with GBS and 300 healthy controls from the Bangladeshi population. Genotype distributions were not significantly different between patients with GBS and healthy controls. The FAS -670 AG heterozygous (P = 0.0005, OR = 2.5, 95% CI = 1.5–4.2) and GG homozygous (P = 0.0048, OR = 2.6, 95% CI = 1.3–5.0) genotypes were more common in patients with anti-GM1 antibodies than patients without anti-GM1 antibodies. The FAS -670 G allele was more prevalent in anti-GM1 antibody-positive than -negative patients (P = 0.0002, OR = 1.9, 95% CI = 1.4–2.7) and also in patients with the axonal subtype than demyelinating subtype (P < 0.0001, OR = 4.8, 95% CI = 2.3–10.1). The 1377G/-670G GG haplotype was significantly associated with the axonal subtype (P < 0.0001) and anti-ganglioside antibody-positivity (P = 0.0008) in GBS. Serum sFas (237.5 pg/mL vs. 159.5 pg/mL; P < 0.0001) and sFasL (225.1 pg/mL vs. 183.4 pg/mL; P = 0.0069) were elevated in patients with GBS compared to healthy controls, and among patients with high serum sFas was associated with severe GBS (P = 0.0406). In conclusion, this study indicates FAS-FASL promoter SNPs may promote the production of cross-reactive anti-ganglioside antibodies in GBS.

Beclin-1-mediated Autophagy Protects Against Cadmium-activated Apoptosis via the Fas/FasL Pathway in Primary Rat Proximal Tubular Cell Culture

The Fas/FasL signaling pathway is one of the primary apoptosis pathways, but the involvement and regulatory mechanism of this pathway by autophagy remain unclear. Here we demonstrated that cadmium (Cd) activated the Fas/FasL apoptosis pathway in rat proximal tubular (rPT) cells; this was accompanied by simultaneous activation of autophagy resulted in reduced apoptosis. In this model, we induced autophagy through RAPA and further demonstrated that autophagy protects against activation of Fas/FasL signaling and apoptosis. The antiapoptotic effect of autophagy was blocked by 3-MA, an autophagy inhibitor. The interactions between Beclin-1 and Fas, FasL, FADD, caspase-8 and BID/tBID were relatively weak, with the exception of cleaved caspase-8, indicated that minimal interactions between these proteins and Beclin-1 are involved in maintaining the balance of autophagy and apoptosis. Beclin-1 precipitated with cleaved caspase-8 in a dose-dependent mannter, and the expression was increased by siRNA against Beclin-1. These data suggested that Beclin-1-mediated autophagy impairs the expression and function of cleaved caspase-8 to protect against Cd-induced activation of apopotosis through Fas/FasL signaling pathway.

Evolving Role of Serum Biomarkers in the Management of Ovarian Cancer

The availability of an ideal serum tumor marker would be of great clinical benefit for both the diagnosis and management of patients with epithelial ovarian cancer. Serum cancer antigen 125 assay significantly increases the diagnostic reliability of ultrasound in discriminating a malignant from a benign ovarian mass, especially in postmenopausal women, and it is the only well validated tumor marker for monitoring disease course. Several other tumor-associated antigens have been assessed, including glycoprotein antigens other than cancer antigen 125, soluble cytokeratin fragments, kallikreins, cytokines and cytokine receptors, vascular endothelial growth factor, D-dimer, and lisophosphatidic acid. This article assesses the potential diagnostic and prognostic role of these novel biomarkers, both alone and in combination with cancer antigen 125. The future for serum tumor marker research is represented by the emerging technology of proteomics, which may allow scientific advances comparable to those achieved with the introduction of monoclonal antibody technology.

Systemic immune response after laparoscopic and open cholecystectomy

The laparoscopic approach is thought to reduce the postoperative immunologic and metabolic effects of an open operation. This study was designed with the aim of comparing the systemic immune response after laparoscopic and open cholecystectomy. Seventeen patients with gallbladder stones were assigned to undergo either a laparoscopic (n = 9) or open (n = 8) approach. The postoperative immune response was assessed by measuring the serum levels of soluble Fas (sFas), soluble L-selectin (sL-selectin), and transforming growth factor-beta1 (TGFbeta1) preoperatively and 2 hours, 1 day, and 2 days postoperatively. Both approaches resulted in a significant decrease in sFas levels 1 and 2 days postoperatively. The open approach evoked a transient increase in sL-selectin levels 2 hours postoperatively. Moreover, the open approach resulted in a persistent, significant increase in TGFbeta1 levels postoperatively. Comparison of open versus laparoscopic cholecystectomy has shown no significant difference in sFas level and a statistically significant increase of sL-selectin (within 2 hours) and TGFbeta levels after open surgery. Although both laparoscopic and open cholecystectomy evoked an alteration of the systemic immune response, our data showed that such immune response may be less after the laparoscopic approach.

Changes of cytokines in patients with liver cirrhosis and advanced hepatocellular carcinoma treated by sorafenib

PURPOSE

Recently, the oral multikinase inhibitor sorafenib has been used to treat advanced hepatocellular carcinoma (aHCC). Tumor necrosis factor (TNF) induces apoptosis of tumor cells by binding to TNF-related apoptosis-inducing ligand, while binding of the Fas ligand on cytotoxic T lymphocytes to the Fas receptor on hepatocytes also causes apoptosis. The aim of this study was to retrospectively evaluate changes of cytokines in patients with liver cirrhosis (LC) and aHCC receiving sorafenib therapy.

METHODS

Fifty-seven adult Japanese LC patients received sorafenib for aHCC (200-800 mg/day for 4 weeks) between 2009 and 2012 at our hospital. Blood samples were collected in the early morning before and after treatment, and the serum levels of soluble TNF-alpha (sTNF-alpha), soluble TNF receptor (sTNF-R), soluble Fas ligand (sFas L), and soluble Fas (sFas) were evaluated.

RESULTS

Ten patients were treated with sorafenib at 200 mg/day (200 mg group), 37 patients were given 400 mg/day (400 mg group), and 10 patients received 800 mg/day (800 mg group). The serum level of sTNF-alpha was significantly increased after treatment compared with before treatment in the 400 and 800 mg groups. The serum level of sTNF-R also showed a significant increase after treatment in the 400 mg group, although there was no significant difference of sTNF-R between before and after treatment in the 200 and 800 mg groups. sFas showed a significant decrease after treatment compared with before treatment in the 400 and 800 mg groups, although the serum level of sFas L never exceeded 0.15 ng/ml.

CONCLUSIONS

These findings suggest that treatment with sorafenib at doses ≥400 mg/day might promote TNF-related or Fas-related apoptosis by increasing the circulating level of TNF-alpha or decreasing that of sFas.

Functional polymorphisms in cell death pathway genes FAS and FAS ligand and risk of prostate cancer in a Chinese population

BACKGROUND

Apoptosis is the physiological mechanism of programmed cell death and abnormal regulation of this pathway can lead to carcinogenesis. We hypothesized that the FAS -1377G>A, -670A>G, and FASL -844T>C polymorphisms are associated with risk of prostate cancer (PCa).

MATERIALS AND METHODS

We genotyped polymorphisms in a hospital-based case-control study of 602 patients diagnosed with PCa and 703 cancer-free controls in a Chinese population using polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

We found a significantly decreased risk associated with FAS -1377GA [adjusted odds ratio (OR) = 0.71, 95% confidence interval (CI) = 0.56-0.90] genotype compared with the -1377GG genotype and decreased risk associated with FAS -670AG and -670GG genotypes (OR 0.75, 95% CI: 0.59-0.95; OR 0.70, 95% CI: 0.50-0.96) compared with the -670AA genotype. Consistently, we found that individuals carrying haplotype genotype with 0 or 1 risk allele (-1377G and -670A) had a lower risk of PCa than those with two risk alleles (OR 0.48, 95% CI: 0.28-0.80; OR 0.60, 95% CI: 0.41-0.87; OR 0.82, 95% CI: 0.69-0.97 for the AA, GG, and AG haplotype, respectively). In addition, when we evaluated these two FAS polymorphisms together, we found that the combined genotype with 4 risk alleles was associated with a significantly increased risk of PCa compared with those with 0-3 variants (OR 1.51, 95% CI: 1.19-1.91), and this increased risk was more pronounced among subgroups of Gleason score <7 and >7, and PSA > 20 ng/ml (OR 1.49, 95% CI: 1.08-2.04; OR 1.72, 95% CI: 1.25-2.44; OR 1.61, 95% CI: 1.23-2.13, respectively).

CONCLUSIONS

These results suggested that the FAS polymorphisms may contribute to PCa risk in a Chinese population.

Sodium valproate, a histone deacetylase inhibitor, decreases the secretion of soluble Fas by human osteosarcoma cells and increases their sensitivity to Fas-mediated cell death

PURPOSE

Effects of valproic acid (VPA), a histone deacetylase inhibitor, on the susceptibility to cell death induced by agonistic anti-Fas antibody were examined using four human osteosarcoma cell lines.

METHOD

Cell growth, secretion of soluble Fas, expression of cell-surface Fas, and sensitivity to Fas-mediated cell death were examined using cell proliferation assay, flow cytometry, enzyme-linked immunosorbent assay, and agonistic anti-Fas antibody, respectively.

RESULTS

VPA suppressed the growth of all the four osteosarcoma cell lines and the secretion of soluble Fas from these cells. VPA showed no or slight suppressive effect on the expression of cell-surface Fas in the four osteosarcoma cell lines, but increased the sensitivity of three of four osteosarcoma cell lines to Fas-mediated cell death.

CONCLUSION

VPA enhances the susceptibility of human osteosarcoma cells to Fas-ligand-induced cell death by decreasing the secretion of soluble Fas and increasing the sensitivity to Fas-mediated cell death.

Serum and tissue biomarkers as predictive and prognostic variables in epithelial ovarian cancer

Tumour stage, residual disease after initial surgery, histological type and tumour grade are the most important clinical-pathological factors related to the clinical outcome of patients with epithelial ovarian cancer. In the last years, several investigations have assessed different biological variables in sera and in tissue samples from patients with this malignancy in order to detect biomarkers able to reflect either the response to chemotherapy or survival. The present paper reviewed the literature data about the predictive or prognostic relevance of serum CA 125, soluble cytokeratin fragments, serum human kallikreins, serum cytokines, serum vascular endothelial growth factor and plasma d-dimer as well as of tissue expression of cell cycle- and apoptosis-regulatory proteins, human telomerase reverse transcriptase, membrane tyrosine kinase receptors and matrix metalloproteinases. A next future microarray technology will hopefully offer interesting perspectives of translational research for the identification of novel predictive and prognostic biomarkers for epithelial ovarian cancer.

Correlation between soluble Fas level and apoptosis of T cells in ovarian carcinoma

OBJECTIVES

The objectives were to examine the correlation between soluble Fas (sFas) level and apoptosis of T cells in peripheral blood and peritoneal fluid of patients with ovarian carcinoma and to investigate the possible sFas effect on T cell apoptosis.

STUDY DESIGN

Patients with stages I-II ovarian carcinoma (n=10) and patients with stages III-IV ovarian carcinoma (n=22), as well as ovarian benign tumors (n=8), were enrolled in the study. Apoptosis of and Fas expression on T cells from peripheral blood and peritoneal fluids were assessed by flow cytometry. Soluble Fas level was assayed using an ELISA kit. The effects of peritoneal fluid on Jurkat cell apoptosis with or without depletion of sFas were evaluated and compared in vitro.

RESULTS

The sFas level and apoptosis of T cells in peripheral blood and peritoneal fluid from stages III-IV ovarian carcinoma were significantly higher than those from stages I-II ovarian carcinoma (p<0.01 in all instances) and benign ovarian tumor (p<0.01 in all instances). In peritoneal fluid, the sFas level and apoptosis of T cells from stages I-II ovarian carcinoma were significantly higher than those from benign ovarian tumor (p<0.01 in all instances), and the Fas expression on T cells from ovarian carcinoma were higher than those from benign ovarian tumor (p<0.05 in all instances). There was a positive correlation between the sFas level and the apoptosis of T cells in peritoneal fluids from stages III-IV ovarian carcinoma (r=0.647, p=0.001). Peritoneal fluid of ovarian carcinoma could induce significant Jurkat cell apoptosis. The blocking of Fas expression on the Jurkat cell surface, but not the deletion of sFas, may remarkably restrain the apoptosis level.

CONCLUSIONS

Elevated sFas is correlated with apoptosis of T cells in peripheral blood and peritoneal fluid from ovarian carcinoma. Soluble Fas evidently does not affect T cell apoptosis, which is probably due to elevated Fas expression on T cells.

A polymorphism in FAS gene promoter correlated with circulating soluble FAS levels

The -670FAS (A/G) polymorphism and elevated concentrations of the soluble form of FAS (sFAS) have been associated with neoplasic and autoimmune diseases. This polymorphism in the Fas promoter gene could modulate the transcription of Fas expression and therefore, contribute to these pathologies. The in vivo functional significance of the FAS polymorphism was investigated by assessing the correlation between FAS genotypes and the serum-circulating FAS (sFAS) levels. We determined the FAS polymorphism distributions by restriction fragment-length polymorphism-polymerase chain reaction in 170 normal subjects. We used enzyme-linked immunosorbent assay to evaluate the sFAS levels in 44 of these individuals. Assessment of the concentration of sFAS indicated that the level of sFAS in subjects carrying the FAS-A/A genotype was significantly higher than that of those carrying the G/G genotype (3.90 ng mL(-1) vs. 3.12 ng mL(-1), P = 0.035). Our results demonstrated that FAS promoter polymorphism was significantly associated with the level of soluble FAS production in normal subjects.

Current concepts in apoptosis: the physiological suicide program revisited

Apoptosis, or programmed cell death (PCD), involves a complex network of biochemical pathways that normally ensure a homeostatic balance between cellular proliferation and turnover in nearly all tissues. Apoptosis is essential for the body, as its deregulation can lead to several diseases. It plays a major role in a variety of physiological events, including embryonic development, tissue renewal, hormone-induced tissue atrophy, removal of inflammatory cells, and the evolution of granulation tissue into scar tissue. It also has an essential role in wound repair. The various cellular and biochemical mechanisms involved in apoptosis are not fully understood. However, there are two major pathways, the extrinsic pathway (receptor-mediated apoptotic pathway) and the intrinsic pathway (mitochondria-mediated apoptotic pathway), which are both well established. The key component in both is the activation of the caspase cascade. Caspases belong to the family of proteases that ultimately, by cleaving a set of proteins, cause disassembly of the cell. Although the caspase-mediated proteolytic cascade represents a central point in the apoptotic response, its initiation is tightly regulated by a variety of other factors. Among them, Bcl-2 family proteins, TNF and p53 play pivotal roles in the regulation of caspase activation and in the regulation of apoptosis. This review summarizes the established concepts in apoptosis as a physiological cell suicide program, highlighting the recent and significant advances in its study.

Modulation of apoptosis as a target for liver disease

Apoptosis mediated via extrinsic or intrinsic pathways is essential for maintaining cellular homeostasis in the liver. The extrinsic pathway is triggered from the cell surface by engagement of death receptors as CD95, TRAIL (TNF-related apoptosis inducing ligand) and TNF (tumour necrosis factor) or TGF-beta (transforming growth factor beta) receptors. The intrinsic pathway is initiated from the mitochondria and can be influenced by Bcl-2 family members. Both pathways are intertwined and play a physiological role in the liver. Dysregulation of apoptosis pathways contributes to diseases as hepatocellular carcinoma, viral hepatitis, autoimmune hepatitis, ischaemia-reperfusion injury, iron or copper deposition disorders, toxic liver damage and acute liver failure. The apoptosis defects are often central pathogenetic events; hence molecular mechanisms of apoptosis give not only insight into disease mechanisms but also provide potential corresponding therapeutic candidates in liver disease. The focus of this review is the identification of apoptotic signalling components in the liver as therapeutic targets.

Soluble Fas receptor and soluble Fas ligand in the serum of women with uterine tumors

It is commonly accepted that apoptosis plays an important role in the death of normal and neoplastic cells. Related proteins and their receptors on cell surfaces regulate apoptosis. One of the best-characterized systems is the Fas-Fas ligand system. The aim of the study was to examine the concentrations of soluble Fas receptor (sFas) and the soluble ligand for the Fas receptor (sFasL) in serum of women with uterine tumors. The study included 42 women with uterine tumors. As a normal control, sera were obtained from 20 healthy female volunteers. The concentrations of sFas and sFasL in serum were measured by enzyme-linked immunosorbent assay ELISA. Significant increases of the mean value of sFas and sFasL were found in the serum of women with uterine tumor compared to the control group (p < 0.0001). The mean levels of these parameters increased in consecutive stages of the clinical extent of the uterine cancer (I-III). The lowest concentration was observed in women with stage I and the highest in women with stage III of clinical extent according to FIGO. Apoptosis that appears to occur in the cancerous cells of malignant uterine tumors is associated with high levels of sFas and sFasL in serum.

Close localization of DAP-kinase positive tumour-associated macrophages and apoptotic colorectal cancer cells

The death-associated protein kinase (DAP-kinase) is a cytoskeleton-associated protein crucially involved in the induction of early apoptotic pathways. Aberrant hypermethylation of the DAP-kinase promoter plays a major role in tumorigenesis. We aimed to investigate the inactivation of DAP-kinase and its association with apoptotic cell death in 94 colorectal carcinomas. DAP-kinase promoter hypermethylation and mRNA expression were investigated using methylation-specific PCR and real-time RT-PCR, respectively. The expression of DAP-kinase, Fas, and Fas-ligand (FasL) proteins was studied by immunohistochemistry and immunofluorescence. Apoptosis of tumour cells was investigated using the TUNEL assay. DAP-kinase was expressed in tumour cells and tumour-invading macrophages and was closely associated with high numbers of apoptotic tumour cells. DAP-kinase expression co-localized with FasL overexpression in tumour-associated macrophages, and aberrant promoter hypermethylation was verified in more than 50% of carcinomas. There was a tendency for proximal tumours to show DAP-kinase promoter methylation more frequently (p = 0.07). Promoter methylation resulted in a decrease or loss of DAP-kinase protein expression in tumour cells and tumour-associated macrophages. Simultaneously, a decreased apoptotic count and loss of Fas/FasL expression was observed in tumour cells. Our study is the first to demonstrate DAP-kinase expression in invading tumour-associated macrophages in colorectal cancer. The presence of similar expression levels of DAP-kinase in tumour cells and associated macrophages, and their dependence on the promoter methylation status of the tumour cells, suggests cross talk between these cell types during apoptotic cell death.

Modulation of sFas indicates apoptosis in human herpes simplex encephalitis

Herpes simplex encephalitis (HSE) is the most common cause of non-epidemic, acute and fatal viral encephalitis. A pronounced mortality and morbidity remains in HSE despite antiviral treatment. There is evidence of a vigorous intrathecal immune activity in acute phases of HSE and of persistently increased activity at follow-ups after years. The role of apoptosis of neuronal cells in HSE patients as a mechanism of damage has been brought up lately. We hypothesize that the severity and the progression of the cerebral injury resulting from HSE can be evaluated by quantitative measurement of a compartment of immune activation molecules i.e. soluble Fas (sFas) involved in apoptosis through the Fas/Fas Ligand pathway. Consecutive cerebrospinal fluid (CSF) samples from a prospectively followed cohort, included in an antiviral treatment trial in HSE, were enrolled for quantitative measurement of sFas using commercial capture ELISA. In total, CSF samples from 49 patients with HSE, 63 patients with non-HSE encephalitis and 18 healthy individuals were studied. High levels of sFas were expressed in CSF samples collected between days 0-45 after neurological onset in 41/49 (84%) HSE patients, whereas only 21/63 (33%) of non-HSE patients and none of 18 healthy controls demonstrated measurable levels of sFas. Following the consecutive CSF sFas levels over the time and considering the clinical state of patients at admission, their neurological or lethal outcome at 12 months, and antiviral treatment, we observed that HSE patients with severe neurological sequels revealed an increase in changes of CSF sFas as compared to patients with mild or moderate neurological outcome (57.6+/-55.6 pg/ml, n=10 versus 26.3+/-97.5 pg/ml, n=14; P=0.008). Also HSE patients undergoing vidarabine treatment expressed significantly higher levels of changes of CSF sFas when compared to acyclovir-treated patients (63.7+/-52.8 pg/ml, n=9 versus 26.1+/-98.4 pg/ml, n=14; P=0.003). Interestingly, regardless of the clinical state at admission, and subsequent disease progression of the HSE patients, we could not observe any significant differences in the CSF sFas levels during the first 7 days of neurological symptoms. These observations underline the role of immunological response throughout the course of HSV infection in the brain and the role of the Fas/FasL pathway in particular in disease progression of HSE. The findings further enforce the need of expanding the knowledge of the pathogenesis of HSE to direct to more effective, in particular not only antiviral but also anti-apoptotic or anti-inflammatory treatment.

Inhibition by interleukin-18 of the growth of Dunn osteosarcoma cells

To examine the usefulness of interleukin-18 (IL-18) in the treatment of osteosarcomas, the effect of IL-18 on the growth of Dunn osteosarcoma cells was investigated. Daily intraperitoneal (i.p.) injection of mouse recombinant IL-18 (2 microg/mouse) suppressed the growth of Dunn osteosarcoma cells transplanted subcutaneously (s.c.) into syngeneic C3H mice. This IL-18-induced suppression was not affected by simultaneous treatment with anti-asialo GM1 serum, which inactivates natural killer (NK) cells. However, IL-18 failed to suppress the growth of Dunn osteosarcoma cells transplanted into BALB/c-nude mice devoid of T lymphocytes or C3H-gld/gld mice deficient in functional Fas ligand (FasL). IL-18 also failed to suppress the growth of Dunn osteosarcoma cells in vitro, although expression of IL-18 receptor mRNA and MyD88 mRNA as well as Fas mRNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). On the other hand, antimouse Fas antibody showed cytotoxicity against Dunn osteosarcoma cells in a dose-dependent manner in vitro. In addition, treatment of C3H mice with IL-18 enhanced the cytotoxic activity of CD8(+) T lymphocytes against Dunn osteosarcoma cells. These results indicate that IL-18 inhibits the growth of Dunn osteosarcoma cells in vivo by enhancing the cytotoxic activity of CD8(+) T lymphocytes through the FasL-Fas system.

Identification of SCN3B as a novel p53-inducible proapoptotic gene

Tumor suppressor p53 is a transcription factor that induces growth arrest and/or apoptosis in response to cellular stress. To identify novel p53-inducible genes, we compared the expression of genes in normal mouse embryo fibroblasts (MEFs) to p53-null cells by cDNA representational difference analysis. We report here that expression of endogenous sodium channel subunit beta 3 (SCN3B) is upregulated in mouse embryonic fibroblasts by DNA damage in a p53-dependent manner. In addition, we found that SCN3B levels are upregulated in human cancer cell lines by DNA damaging agents, as well as by overexpression of p53, but not significantly by p63 or p73. Furthermore, we identified two putative p53-binding sites upstream of the first exon (RE1) and in the third intron (RE2). The p53 protein can directly interact with the putative p53-binding sites in vivo, as assessed by chromatin immunoprecipitation. A reporter gene assay revealed that these two p53-binding sites are functional response elements. The SCN3B protein appears to be localized to the endoplasmic reticulum (ER). Introduction of the SCN3B gene into T98G and Saos2 cells potently suppressed colony formation. Furthermore, we found that adenovirus-mediated transfer of SCN3B induced apoptosis when combined with anticancer agents. The results presented here suggest that SCN3B mediates a p53-dependent apoptotic pathway and may be a candidate for gene therapy combined with anticancer drugs.

In vivo mitochondrial p53 translocation triggers a rapid first wave of cell death in response to DNA damage that can precede p53 target gene activation

p53 promotes apoptosis in response to death stimuli by transactivation of target genes and by transcription-independent mechanisms. We recently showed that wild-type p53 rapidly translocates to mitochondria in response to multiple death stimuli in cultured cells. Mitochondrial p53 physically interacts with antiapoptotic Bcl proteins, induces Bak oligomerization, permeabilizes mitochondrial membranes, and rapidly induces cytochrome c release. Here we characterize the mitochondrial p53 response in vivo. Mice were subjected to gamma irradiation or intravenous etoposide administration, followed by cell fractionation and immunofluorescence studies of various organs. Mitochondrial p53 accumulation occurred in radiosensitive organs like thymus, spleen, testis, and brain but not in liver and kidney. Of note, mitochondrial p53 translocation was rapid (detectable at 30 min in thymus and spleen) and triggered an early wave of marked caspase 3 activation and apoptosis. This caspase 3-mediated apoptosis was entirely p53 dependent, as shown by p53 null mice, and preceded p53 target gene activation. The transcriptional p53 program had a longer lag phase than the rapid mitochondrial p53 program. In thymus, the earliest apoptotic target gene products PUMA, Noxa, and Bax appeared at 2, 4, and 8 h, respectively, while Bid, Killer/DR5, and p53DinP1 remained uninduced even after 20 h. Target gene induction then led to further increase in active caspase 3. Similar biphasic kinetics was seen in cultured human cells. Our results suggest that in sensitive organs mitochondrial p53 accumulation in vivo occurs soon after a death stimulus, triggering a rapid first wave of apoptosis that is transcription independent and may precede a second slower wave that is transcription dependent.

Synthetic retinoids as inducers of apoptosis in ovarian carcinoma cell lines

Apoptosis is also known as programmed cell death. Apoptosis plays an essential role in maintaining normal tissue and cell physiology in multicellular organisms. Clearance of aberrant or pre-cancerous cells occurs through the induction of apoptosis. It has been reported that many tumors and tumor cell lines have dysfunctional apoptosis signaling, causing these tumors to escape immune monitoring and internal cellular control mechanisms. One potential cause of this dysfunctional apoptosis is the tumor suppressor p53, an important regulator of growth arrest and apoptosis that is mutated in over 50% of all cancers. Retinoids have great potential in the areas of cancer therapy and chemoprevention. While some tumor cells are sensitive to the growth inhibitory effects of natural retinoids such as all-trans-retinoic acid (ATRA), many ovarian tumor cells are not. 6-[3-(1-Admantyl)]-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) and fenretinide N-[4-hydroxyphenyl] retinamide (4-HPR) are conformationally restricted synthetic retinoids that induce growth arrest and apoptosis in both ATRA-sensitive and ATRA-resistant ovarian tumor cell lines. Recently, we have identified the molecular pathways of apoptosis induced by treatment of ovarian carcinoma cells with mutated p53 by CD437 and 4-HPR.

Circulating soluble Fas levels and risk of ovarian cancer

BACKGROUND

Dysregulation of apoptosis, specifically overexpression of soluble Fas (sFas), has been proposed to play a role in the development of ovarian cancer. The main objective of the present study was to evaluate serum sFas as a potential biomarker of ovarian cancer risk.

METHODS

The association between serum sFas levels and the risk of ovarian cancer was examined in a case-control study nested within three prospective cohorts in New York (USA), Umeå (Sweden), and Milan (Italy). Case subjects were 138 women with primary invasive epithelial ovarian cancer diagnosed between 2 months and 13.2 years after the initial blood donation. Control subjects were 263 women who were free of cancer, and matched the case on cohort, menopausal status, age, and enrollment date. Serum sFas levels were determined using a quantitative sandwich enzyme immunoassay.

RESULTS

Serum sFas levels were similar in women subsequently diagnosed with ovarian cancer (median, 6.5 ng/mL; range, 4.4-10.2) and in controls (median, 6.8 ng/mL; range, 4.5-10.1). Statistically significant trends of increasing serum sFas with age were observed among cases (r = 0.39, p < 0.0001) and controls (r = 0.42, p < 0.0001). Compared to women in the lowest third, women in the highest third of serum sFas were not at increased risk of ovarian cancer after adjustment for potential confounders (odd ratio (OR), 0.87; 95% confidence interval (CI), 0.42-1.82).

CONCLUSION

The results suggest that serum sFas may not be a suitable marker for identification of women at increased risk of ovarian cancer.

Gene expression profiles in human cells submitted to genotoxic stress

Cell response to genotoxic agents is complex and involves the participation of different classes of genes (DNA repair, cell cycle control, signal transduction, apoptosis and oncogenesis). In this report, we present three approaches to document gene expression profiles, dealing with the evaluation of cellular responses to genotoxic agents (gamma-rays from 60Cobalt and cyclophosphamide). We used the method of cDNA arrays to analyze the differential gene expression profiles that were displayed by lymphocytes from radiation-exposed individuals, a human fibroblast cell line, and T lymphocytes from systemic lupus erythematosus (SLE) patients who were treated with cyclophosphamide. A preliminary analysis performed in lymphocytes from three radiation-workers showed that several induced genes can be associated with cell response to ionizing radiation: TRRAP (cell cycle regulation), Ligase IV (DNA repair), MAPK8IP1 and MAPK10 (signal transduction), RASSF2 (apoptosis induction/tumorigenesis), p53 (damage response/maintenance of genetic stability). The in vitro irradiated normal VH16 cell line (primary) showed a complex response to the genotoxic stress at the molecular level. Many apoptotic pathways were concomitantly induced. In addition, several genes involved in signaling and cell cycle arrest/control were significantly modulated after irradiation. Many genes involved in oxidative damage were also induced, indicating that this mechanism seems to be an important component of cell response. After treatment of the SLE patients with cyclophosphamide, 154 genes were differentially and significantly induced. Among them, we identified those associated with drug detoxification, cell cycle control, apoptosis, and tumor-suppressor. These findings indicate that at least two apoptotic pathways were induced after cyclophosphamide treatment. The induction of APAF1 and two genes coding for two subunits of cytochrome c supports a previous report showing increased apoptosis in lymphocytes from SLE patients. The present study provides new information on the molecular mechanism underlying the cell response to genotoxic stress, with relevance to basic and clinical research.

P53 and radiation responses

Cells have evolved elaborate mechanisms (checkpoints) to monitor genomic integrity in order to ensure the high-fidelity transmission of genetic information. Cells harboring defects in checkpoint pathways respond to DNA damage improperly, which in turn may enhance the rate of cancer development. Ionizing radiation (IR) primarily leads to double-strand DNA breaks (DSBs), which activate DNA damage checkpoints to initiate signals ultimately leading to a binary decision between cell death and cell survival. TP53 has been recognized as an important checkpoint protein, functioning mainly through transcriptional control of target genes that influence multiple response pathways and leading to the diversity of responses to IR in mammalian cells. We review how the tumor suppressor P53 is involved in the complex response to IR to enforce the cell's fate to live by inducing the growth arrest coupled to DNA damage repair or to die by inducing irreversible growth arrest or apoptosis. Moreover, recent insights have emerged in our understanding of how P53 modulates radiosensitivity in tissues following IR as well as its role in sensitizing cells to chemo- and radiotherapy. The P53 pathway remains an attractive target for exploitation in the war on cancer.

HIV-1 and IL-1 beta regulate Fas ligand expression in human astrocytes through the NF-kappa B pathway

Reactive astrogliosis is a prominent pathological feature of HIV-1-associated dementia (HAD). We hypothesized that in HAD, astrocytes activated with proinflammatory stimuli such as IL-1beta express Fas ligand (FasL), a death protein. IL-1beta and HIV-1-activated astrocytes expressed FasL mRNA and protein. Luciferase reporter constructs showed that IL-1beta and HIV-1 upregulated FasL promoter activity (p<0.001). The NF-kappaB pathway was involved as shown by inhibition with SN50 and dominant negative IkappaBalpha mutants. Brain extracts from HAD patients had significantly elevated FasL levels compared to HIV-seropositive (p<0.001) and seronegative individuals (p<0.01). We propose that astrocyte expression of FasL may participate in neuronal injury in HAD.

Soluble Fas (sFas) and soluble Fas ligand (sFas-L) balance in laryngeal carcinoma before and after surgical treatment

BACKGROUND AND OBJECTIVES

Fas and its specific ligand (Fas-L), both of which are involved in apoptosis, exist in membrane-bound and soluble forms. The soluble forms (sFas and sFas-L) have been observed in various tumours, but their clinical significance has not yet been clarified. The aim of this study was to assess serum sFas and sFas-L levels in patients with laryngeal squamous cell carcinoma (LSCC) and their possible correlations with surgical treatment.

METHODS

Serum sFas and sFas-L levels were determined by ELISA in samples taken from 26 LSCC patients on the day before surgery (T0), and 2 weeks (T1) and 6 months after surgery (T2), and in samples taken from 35 healthy volunteers.

RESULTS

The mean serum sFas levels in the 35 healthy volunteers and the 26 LSCC patients at T0 were respectively 5941 +/- 411 pg/ml and 6290 +/- 652 pg/ml (P = 0.63), and the mean serum sFas-L levels were 0.1 +/- 0.05 ng/ml and 2.95 +/- 0.8 ng/ml (P < 0.0001). After surgery, there was a statistically significant decrease in sFas at both T1 (P < 0.05) and T2 (P < 0.01), and in sFas-L at T2 (P < 0.01).

CONCLUSIONS

The decrease in sFas and sFas-L levels after surgery suggest that they may be produced by or closely linked to tumour cells. Larger prospective clinical studies of patients with LSCC will be needed to establish the clinical significance of sFas and sFas-L, as reported for other neoplasms.

Soluble Fas in malignant pleural effusion and its expression in lung cancer cells

Soluble Fas (sFas) has the ability to block Fas-mediated apoptosis, suggesting that sFas at tumor sites might inhibit tumor cell-killing by immune effector cells. We examined the sFas level in pleural effusion associated with lung cancer. The level of sFas in malignant pleural effusion was significantly higher than those in transudate and tuberculous pleural effusion. There was no significant difference in the sFas concentration among various histological types of lung cancer. The cytotoxicity mediated by anti-Fas agonistic antibody against Jurkat cells was inhibited by the addition of malignant pleural effusion, being inversely correlated with the sFas concentration. When Fas expression was examined using flow cytometry, eight of ten (80%) lung cancer cell lines expressed cell surface Fas. On the other hand, sFas protein and mRNA were detected in six of ten (60%) lung cancer cell lines, but there was no correlation between Fas and sFas expression. Furthermore, although the expressions of Fas and sFas were clearly detected in tumor cells derived from malignant effusion, the sFas expression was down-regulated in an in vitro culture. These results suggest that sFas in malignant pleural effusion is at least in part produced by lung cancer cells, and might play a role in local immunosuppression by tumor cells.

Increased apoptosis of peripheral blood mononuclear cells in patients with perennial allergic asthma/rhinitis: relation to serum markers of apoptosis

BACKGROUND

The goal of our study was to examine spontaneous and stimulated apoptosis of peripheral blood MNC from allergic patients, sensitized to Der p I antigen as compared to cells from non-atopic subjects. Furthermore we aimed to investigate which populations of mononuclear cells (lymphocytes, monocytes) undergo the apoptosis and to determine relations between apoptosis and serum levels of sFas/APO-1, ICE/caspase-1 or TNF-alpha.

METHODS

The study included 17 patients with perennial, allergic asthma and/or allergic rhinitis [6 male and 11 female; mean age 29,5 years; (range 15-49)]. Apoptosis was assessed by fluorescence technique and confirmed by flow-cytometric method and DNA ladder. Serum levels of sFas, ICE/caspase-1 or TNF-alpha were determined by immunoassays (ELISA).

RESULTS

Apoptotic index of unfractionated mononuclear cells (MNC) and lymphocytes (but not monocytes) were significantly higher in allergic patients as compared to non-allergic subjects after 48 and 72 hours of culture (p<0.05). Incubation of cells with ConA (10 microg/ml) resulted in a significant increase in the proportion of apoptotic cells in all populations once the apoptotic index for MNC and lymphocytes (but not monocytes) was again significantly higher in allergic as compared to non-allergic subjects after 24, 48 and 72 hour of culture. In allergic patients, mean serum sFas level, was significantly lower then in non-allergic group (mean value 624.8 pg/ml +/- 25.67 versus 802.0 pg/ml +/- 31.91; p = 0.003) and in both groups sFas level correlated inversely with apoptosis of MNC. The mean ICE/caspase-1 concentration was significantly higher in sera of allergic patients as compared to non-allergic group (mean value 27.71 pg/ml +/- 3.79 vs 23.54 pg/ml respectively; p<0.01). ICE/caspase-1 levels in allergic patients correlated with apoptotic index of mononuclear cells (r = 0.57; p<0.001).

CONCLUSIONS

An increased spontaneous and mitogen-induced apoptosis of MNC from peripheral blood of atopic patients as well as different serum levels of sFas and ICE/caspase-1 correlating with apoptosis, suggest different regulation of apoptotic process in peripheral blood mononuclear cells of patients with allergic asthma and/or rhinitis.

p53 and Fas ligand are required for psoralen and UVA-induced apoptosis in mouse epidermal cells

A combination of 8-methoxypsoralen (8-MOP) and ultraviolet-A (UVA) radiation (320-400 nm) (PUVA) is widely used in the treatment of psoriasis and other skin diseases. PUVA is highly effective in eliminating hyperproliferative cells in the epidermis, but its mechanism of action has not been fully elucidated. In this study, we used immortalized JB6 mouse epidermal cells, p53(-/-), and Fas ligand deficient (gld) mice to investigate the molecular mechanism by which PUVA induces cell death. The results indicate that PUVA treatment induces apoptosis in JB6 cells. In addition, PUVA treatment of JB6 cells results in p53 stabilization, phosphorylation, and nuclear localization as well as induction of p21(Waf/Cip1) and caspase-3 activity. In vivo studies reveal that PUVA treatment induces significantly less apoptosis in the epidermis of p53(-/-) mice compared to p53(+/+) mice. Furthermore, FasL-deficient (gld) mice are completely resistant to PUVA-induced apoptosis compared to wild-type mice. These results indicate that PUVA treatment induces apoptosis in mouse epidermal cells in vitro and in vivo and that p53 and Fas/Fas ligand interactions are required for this process, at least in vivo. This implies that similar mechanisms may be involved in the elimination of psoriatic keratinocytes from human skin following PUVA therapy.

Induction of apoptosis in malignant pleural mesothelioma cells by activation of the Fas (Apo-1/CD95) death-signal pathway

OBJECTIVE

Although well characterized in several solid tumors, the effects of Fas/Fas ligand interactions in malignant pleural mesothelioma cells have not been defined. The present study was undertaken to examine the functional status of the Fas/Fas ligand pathway in malignant pleural mesothelioma cells and to determine the feasibility of targeting this death-signal pathway for molecular intervention in patients with mesotheliomas.

METHODS

Fas expression in primary normal human bronchial epithelial cells and 6 malignant pleural mesothelioma cell lines was quantified by means of flow cytometry. The caspase components of the Fas-mediated apoptotic pathway were evaluated by means of Western blot techniques. Soluble Fas ligand-mediated cytotoxicity and apoptosis were evaluated by means of MTS and TUNEL assays, respectively. Cisplatin (3 microg/mL) and lymphokine-activated killer cells were used to enhance mesothelioma sensitivity to soluble Fas ligand. An H2373 nude mouse xenograft model of malignant pleural mesothelioma was established to assess the in vivo effects of soluble Fas ligand.

RESULTS

Four of 6 malignant pleural mesothelioma lines exhibited high levels of Fas expression, and 2 of 4 were inherently susceptible to soluble Fas ligand-mediated cytotoxicity (soluble Fas ligand 50% inhibitory concentration, < 15 ng/mL). Two soluble Fas ligand refractory cell lines (H2052 and H513) exhibited high levels of Fas receptor. Pretreatment with cisplatin resulted in a reduction of 50% inhibitory concentration from infinity to 4.17 +/- 0.14 ng/mL and 10.23 +/- 1.58 ng/mL, respectively. Two additional soluble Fas ligand refractory cell lines (H2595 and REN) expressed low levels of Fas. Exposure of these cells to lymphokine-activated killer cells or lymphokine-activated killer cell-conditioned medium followed by a 24-hour treatment with cisplatin resulted in a significant reduction in 50% inhibitory concentration of soluble Fas ligand and pronounced induction of apoptosis. Intraperitoneally administered soluble Fas ligand mediated regression of H2373 xenografts.

CONCLUSION

The Fas/Fas ligand pathway in mesothelioma cells is either intrinsically intact or can be rendered functional with chemotherapeutic agents or immune effector cells. These preclinical data support further evaluation of strategies to enhance Fas-mediated apoptosis in mesotheliomas.

Basic fibroblast growth factor (bFGF)-induced cell death is mediated through a caspase-dependent and p53-independent cell death receptor pathway

The mechanism of bFGF-induced cell death in tumours of the Ewing's sarcoma family (ESFT) has been investigated. bFGF-induces phosphorylation of FGFr 1 and activation of Ras/ERK in ESFT cells that die when exposed to bFGF. Induction of cell death was associated with activation of both initiator (caspases-2, -8 and -10) and effector (caspases-3, -6 and -7) caspases. Moreover, the general caspase inhibitor Z-VAD-FMK protected cells from bFGF-induced cell death. After treatment with bFGF, a loss of mitochondrial transmembrane potential was accompanied by down-regulation of Bcl-2. However, the observed cell death was not associated with release of cytochrome c from the mitochondria. Furthermore, expression of wild-type p53 was not required for bFGF-induced cell death. These observations suggest that bFGF-induced cell death may be mediated through a cell death receptor mechanism, supported by up-regulation of the p75 neurotrophin receptor. bFGF-induced cell death was associated with up-regulation of p21 and p53, down-regulation of PCNA and cyclin A and a decrease in active pRb1, changes consistent with accumulation of cells in G1. These data demonstrate that bFGF-induced cell death is effected through a caspase-dependent and p53-independent mechanism, that may be mediated through a cell death receptor pathway.

Fas ligand expression and depletion of T-cell infiltration in astrocytic tumors

Fas (APO-1/CD95) ligand (FasL) and its receptor, Fas, play a key role in the regulation of apoptosis in the immune system. FasL acts as a cytotoxic effector molecule to Fas-expressing malignant tumor cells; however, it has recently been suggested that FasL also acts as a possible mediator of tumor immune privilege. We studied FasL expression in glioblastoma cell lines and a series of human glioma specimens by Western blotting and immunohistochemistry. In addition, quantitative analysis of T-cell infiltration in these tumors was performed. FasL expression was seen in all cell lines and in 9 of 14 specimens by Western blotting and immunohistochemistry. The distribution of FasL was recognized in the cytoplasm of tumor cells (5 of 9) and in the vascular endothelium (4 of 9). Both types of FasL expression were associated with a significant reduction (p < 0.05) in T-cell infiltration when compared with FasL-negative areas within the same tumor or FasL-negative specimens. Since T-cell apoptosis could be induced by FasL-expressing tumor cells, the present findings suggest that apoptosis induction by FasL expressed on tumor cells and/or vascular endothelium might be one mechanism for T-cell depletion in astrocytic tumor tissues.

Prolonged intrathecal release of soluble Fas following severe traumatic brain injury in humans

The mechanisms underlying cell death following traumatic brain injury (TBI) are not fully understood. Apoptosis is believed to be one mechanism contributing to a marked and prolonged neuronal cell loss following TBI. Recent data suggest a role for Fas (APO-1, CD95), a type I transmembrane receptor glycoprotein of the nerve growth factor/tumor necrosis factor superfamily, and its ligand (Fas ligand, FasL) in apoptotic events in the central nervous system. A truncated form of the Fas receptor, soluble Fas (sFas) may indicate activation of the Fas/FasL system and act as a negative feedback mechanism, thereby inhibiting Fas mediated apoptosis. Soluble Fas was measured in cerebrospinal fluid (CSF) and serum of 10 patients with severe TBI (GCS< or =8) for up to 15 days post-trauma. No sFas was detected in CSF samples from patients without neurological pathologies. Conversely, after TBI 118 out of 120 CSF samples showed elevated sFas concentrations ranging from 56 to 4327 mU/ml. Paired serum samples showed above normal (8.5 U/ml) sFas concentrations in 5 of 10 patients. Serum levels of sFas were always higher than CSF levels. However, there was no correlation between concentrations measured in CSF and in serum (r(2)=0.078, p=0.02), suggesting that the concentrations in the two compartments are independently regulated. Also, no correlation was found between sFas in CSF and blood brain barrier (BBB) dysfunction as assessed by the albumin CSF/serum quotient (Q(A)), and concentrations of the cytotoxic cytokine tumor necrosis factor-alpha in CSF, respectively. Furthermore, there was no correlation with two markers of immune activation (soluble interleukin-2 receptor and neopterin) in CSF. Maximal CSF levels of sFas correlated significantly (r(2)=0.8191, p<0.001) with the early peaks of neuron-specific enolase in CSF (a marker for neuronal cell destruction), indicating that activation of the Fas mediated pathway of apoptosis may be in part the direct result of the initial trauma. However, the prolonged elevation of sFas in CSF may be caused by the ongoing inflammatory response to trauma and delayed apoptotic cell death.

Soluble Fas and Fas-ligand in bladder cancer in vitro and in vivo

Circulating soluble Fas (sFas) and expression of Fas-ligand on cancer cells are mechanisms of immune escape. The aim of the present study was to investigate expression and production of Fas and Fas-ligand on bladder cancer cell lines of different grade as a basic mechanism of their secretion in vivo. sFas and sFas-ligand serum levels of patients with different stage of bladder cancer were examined to determine the possible clinical use of these molecules as tumor markers. Bladder cancer cell lines RT4 (G1), RT112 (G1), T24 (G3) and SUP (G4) were analyzed by flowcytometry for Fas and Fas-ligand expression. To determine if the Fas-ligand gene is transcribed in these bladder cancer cell lines, RT-PCR was performed on mRNA extracted from these cell lines. Production of sFas and sFas-ligand was examined in cell culture supernatants of the cancer cells as well as in the serum of 62 patients with bladder cancer by a specific ELISA test. We demonstrate that Fas is expressed in similar levels on all human bladder carcinoma cell lines. In T24 (G3) and SUP (G4) cell lines we were able to detect the Fas-ligand protein, whereas no Fas-ligand protein could be found in RT4 and RT112 (G1) cells. Fas-ligand mRNA was expressed in all bladder cancer cell lines. Furthermore, all bladder cancer cell lines produce sFas but no sFas-ligand in spite of mRNA expression. The range of sFas levels in the serum of all patients with bladder cancer was large and did not show a correlation to the histopathological stage of bladder cancer. Although there is in vitro evidence that sFas and Fas-ligand play a role in bladder cancer, no correlation between the sFas and s Fas-ligand serum levels and the histopathological stage of bladder cancer could be found. Therefore, serum sFas and sFas-ligand have to date limited clinical relevance.

Bladder cancer cells acquire competent mechanisms to escape Fas-mediated apoptosis and immune surveillance in the course of malignant transformation

Mechanisms of resistance against Fas-mediated cell killing have been reported in different malignancies. However, the biological response of immune escape mechanisms might depend on malignant transformation of cancer cells. In this study we investigated different mechanisms of immune escape in 2 well-differentiated low-grade (RT4 and RT112) and 2 poorly differentiated high-grade (T24 and TCCSUP) bladder cancer cell lines. Fas, the receptor of Fas-ligand, is expressed and shedded by human transitional bladder carcinoma cell lines RT4, RT112, T24 and TCCSUP. Cytotoxicity and apoptosis assays demonstrate that in spite of the Fas expression, poorly differentiated T24 and TCCSUP cells are insensitive towards either recombinant Fas-ligand or agonistic apoptosis-inducing monoclonal antibody against Fas. In poorly differentiated T24 and TCCSUP cell lines we were able to detect marked Fas-ligand protein by flow cytometry and Western blot analysis. In grade 1 RT4 and RT112 cells only minor expression of Fas-ligand possibly because of proteinase action. Fas-ligand mRNA translation or post-translational processing seems to be regulated differentially in the cancer cell lines depending on malignant transformation. In co-culture experiments we show that poorly differentiated cells can induce apoptosis and cell death in Jurkat cells and activated peripheral blood mononuclear cells. This in vitro study suggests that bladder cancer cells can take advantage of different mechanisms of immune evasion and become more competent in avoiding immune surveillance during transformation to higher-grade malignant disease. © 2001 Cancer Research Campaign www.bjcancer.com

Presence of Fas-Fas ligand system and bcl-2 gene products in cells and fluids from gonadotropin-stimulated human ovaries

Apoptosis, or programmed cell death, is an important mechanism for the regulation of embryonic development and tissue homeostasis. It is coordinated by a number of molecules including the Fas-Fas ligand (FasL) system and bcl-2. The purpose of this study was to characterize the expression of these molecules in human oocytes and cumulus cells from gonadotropin-stimulated human ovaries and to determine whether the presence of soluble Fas (sFas), soluble FasL, or interferon-gamma in follicular fluid (FF) correlated with apoptosis in cumulus cells, oocyte maturation, and embryo quality. Levels of sFas were significantly higher in FF containing immature oocytes compared with those containing atretic oocytes (P < 0.05; FF containing mature oocytes had highly variable levels of sFas. Levels of sFas in FF did not correlate with either fertilization, embryo quality resulting from fertilized oocytes, or apoptosis rate in cumulus cells. Fas was expressed in both unfertilized oocytes and cumulus cells, whereas FasL expression was not usually detected in these cell types. Messenger RNA for bcl-2 was detectable in both freshly isolated oocytes and cumulus cells but was not demonstrable following 24 h of culture that coincided with a significant increase of apoptosis in cumulus cells. Our results indicate that soluble forms of the Fas-FasL system are present in FF from gonadotropin-stimulated human ovaries and suggest that this system may play a role in preventing oocyte atresia during folliculogenesis but is probably not important for apoptotic events in cumulus cells and oocytes after fertilization failure. Apoptosis in this case may be facilitated by the downregulation of bcl-2. Further studies on the expression of these molecules in follicles containing atretic oocytes and immature oocytes are needed to confirm this new hypothesis.

Plasma Fas ligand, an inducer of apoptosis, and plasma soluble Fas, an inhibitor of apoptosis, in advanced melanoma

The transmembrane receptor Fas/APO-1, together with its protein-binding partner (Fas ligand), is a key regulator of programmed cell death and induces apoptosis when it binds Fas ligand (FasL) or soluble Fas ligand (sFasL). However, soluble Fas (sFas) blocks apoptosis by inhibiting binding between Fas and FasL or sFasL. At present, the status of sFas and sFasL in metastatic malignant melanoma remains unknown. This study sought to evaluate the relationship between plasma levels of sFas and/or sFasL and clinical response in 45 metastatic malignant melanoma patients treated by biochemotherapy. sFas and sFasL were measured by specific enzyme-linked immunosorbent assay (ELISA) tests in the sera from patients and 34 healthy donors. Overall, sFas and sFasL levels in patients were significantly higher (P < 0.0001) than in healthy donors. Before the biochemotherapy treatment the sFas level was about the same in biochemorefractory (n = 26) as in responder patients (n = 19). In contrast, the sFasL level was very high only in biochemorefractory patients. At the end of the treatment, in biochemorefractory patients the sFas level was extremely significantly increased (P < 0.0001) and a significant decrease in the plasma levels of sFasL was observed (P = 0.0002). In responder patients, no change in sFas and sFasL was detected. In conclusion, elevated levels of sFas and sFasL might be associated with poor prognosis in advanced melanoma; their possible role in the regulation of apoptosis in influencing the response to biochemotherapy should be further explored.

Serum soluble Fas (CD95) and Fas ligand profiles in chronic kidney failure

Apoptosis, or programmed cell death, is an active form of cell death that is initiated by a number of stimuli and is intricately regulated. Apoptosis in both excessive and reduced amounts has pathophysiologic implications. Accelerated programmed cell death has been observed in leukocytes among patients with chronic renal failure (CRF). This has been ascribed in part to the retention of uremic toxins. The Fas/Fas ligand (FasL) system is a key regulatory apoptotic pathway. Membrane-bound Fas is a cell-surface receptor that transduces apoptosis after interaction with membrane-bound or soluble FasL (sFasL). By contrast, soluble Fas (sFas) binds sFasL and inhibits its activity. In an attempt to examine the balance between these soluble factors in uremia, we measured soluble sFas and sFasL levels in the serum of healthy control subjects and patients with various degrees of CRF and examined the distribution of the various molecular mass fractions of these proteins in uremic serum. In brief, serum was obtained from 15 healthy volunteers, 17 patients with CRF, 11 patients undergoing maintenance hemodialysis (HD), and 7 patients undergoing peritoneal dialysis (PD). Serum sFas and sFasL were measured by enzyme-linked immunosorbent assay, and their molecular distribution was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblot. Compared with results in healthy control subjects, sFas levels were significantly higher in patients with CRF and in patients undergoing dialysis. There was a significant inverse correlation between sFas levels and creatinine clearance. Serum sFasL levels were not different among the four groups. However, the sFas-to-sFasL ratio was significantly lower in healthy control subjects as compared with patients with CRF and patients undergoing dialysis. Immunoblots and densitometric analyses of sFas and sFasL depicted a known 48-kd sFas, a known 27-kd sFasL, and a 60-kd sFas-sFasL protein aggregate signal. In conclusion, serum sFas levels are increased in patients with various degrees of CRF and may bind circulating sFasL, thereby minimizing mediation of cellular apoptosis.

Altered mechanisms of apoptosis in colon cancer: Fas resistance and counterattack in the tumor-immune conflict

Fas (CD95/APO-1) is a cell surface "death receptor" that mediates apoptosis upon engagement by its ligand, FasL. Fas-mediated apoptosis of lymphocytes normally serves immunoregulatory roles, including tolerance acquisition, immune response termination, and maintenance of immune privilege in certain organs. Colon tumors can exploit this lymphocyte death program by expressing FasL. This may enable colon tumors to mount a "Fas counterattack" against antitumor lymphocytes, impairing antitumor immune responses. FasL-expressing colon tumor-derived cell lines can trigger Fas-mediated apoptosis of cocultured T cells in vitro. FasL expressed in esophageal cancer has been significantly associated with apoptosis and depletion of tumor-infiltrating lymphocytes (TIL) in vivo. FasL may also facilitate metastatic colonization of Fas-sensitive organs such as the liver, by inducing apoptosis of target organ cells. Normal colonic epithelial cells express Fas and are relatively sensitive to Fas-mediated apoptosis. By contrast, colon tumor-derived cell lines are usually resistant to induction of Fas-mediated apoptosis, and colon cancer cells frequently coexpress Fas and FasL. The mechanisms allowing resistance to Fas-mediated apoptosis are complex, and defects have been identified at several levels of Fas signal transduction. The "Bcl-2 rheostat" may be pitched against apoptosis in colon cancer, inasmuch as overexpression of Bcl-2, downregulation of Bak, and mutation of Bax are common defects in colon tumors. Caspase-1 is also downregulated in colon cancer. The high frequency of p53 mutations in late-stage cancers may also inhibit Fas signaling. Fundamental defects in apoptosis signaling may contribute to both immuno- and chemoresistance in colon cancer and allow expression of FasL to counterattack antitumor lymphocytes.

Adenoviral vector which delivers FasL-GFP fusion protein regulated by the tet-inducible expression system

Fas ligand (FasL) is a member of the tumor necrosis family and when bound to its receptor, Fas, induces apoptosis. It plays important roles in immune response, degenerative and lymphoproliferative diseases, development and tumorigenesis. It is also involved in generation of immune privilege sites in the eye and testis. Harnessing the power of this molecule is expected to lead to a powerful chemotherapeutic. We describe the construction and characterization of replication-deficient adenoviral vectors that express a fusion of murine FasL and green fluorescent protein (GFP). FasL-GFP retains full activity of wild-type FasL, at the same time allowing for easy visualization and quantification in both living and fixed cells. The fusion protein is under the control of a tetracycline-regulated gene expression system. Tight control of expression is achieved by creating a novel 'double recombinant' Ad vector, in which the tet-responsive element and the transactivator element are built into the opposite ends of the same vector to avoid enhancer interference. Expression can be conveniently regulated by tetracycline or its derivatives in a dose-dependent manner. The vector was able to deliver FasL-GFP gene to cells in vitro efficiently, and the expression level and function of the fusion protein was modulated by the concentration of doxycycline. This regulation allows us to produce high titers of the vector by inhibiting FasL expression in an apoptosis-resistant cell line. Induction of apoptosis was demonstrated in all cell lines tested. These results indicate that our vector is a potentially valuable tool for FasL-based gene therapy of cancer and for the study of FasL/Fas-mediated apoptosis and immune privilege.

Fas/APO-1 protein is increased in spaceflown lymphocytes (Jurkat)

Human lymphocytes flown on the Space Shuttle respond poorly to mitogen stimulation and populations of the lymphoblastoid T cell line, Jurkat, manifest growth arrest, increase in apoptosis and time- and microgravity-dependent increases in the soluble form of the cell death factor, Fas/APO-1 (sFas). The potential role of apoptosis in population dynamics of space-flown lymphocytes has not been investigated previously. We flew Jurkat cells on Space Transportation System (STS)-80 and STS-95 to determine whether apoptosis and the apparent microgravity-related release of sFas are characteristic of lymphocytes in microgravity. The effects of spaceflight and ground-based tests simulating spaceflight experimental conditions, including high cell density and low serum concentration, were assessed. Immunofluorescence microscopy showed increased cell associated Fas in flown cells. Results of STS-80 and STS-95 confirmed increase in apoptosis during spaceflight and the release of sFas as a repeatable, time-dependent and microgravity-related response. Ground-based tests showed that holding cells at 1.5 million/ml in medium containing 2% serum before launch did not increase sFas. Reports of increased Fas in cells of the elderly and the increases in spaceflown cells suggest possible similarities between aging and spaceflight effects on lymphocytes.

Does programmed cell death (apoptosis) play a role in the development of multiple organ dysfunction in critically ill patients? a review and a theoretical framework

OBJECTIVES

To critically review the current understanding of the pathophysiologic events leading to the development of secondary multiple organ dysfunction (MODS) in critical illness and to examine the role of apoptosis (programmed cell death) as a mechanism involved in the progression of MODS.

DATA SOURCES

Research and review articles published since 1982 on the pathophysiology of MODS, particularly the role of cytokines, reactive oxygen species, heat shock proteins, and apoptosis. Research and review articles on the physiology of apoptosis. Articles include human/animal and in vitro/in vivo studies.

DATA EXTRACTION

The most prevalent mediating factors of MODS were examined for their potential to induce apoptosis, as reported in the literature. The combination of several of the above factors was also examined in terms of apoptosis-triggering potential.

DATA SYNTHESIS

Specific pathophysiologic conditions related to the onset of MODS have been shown to affect apoptotic rates in organ tissue cells and their respective endothelial cells in animal and in vitro models. These conditions include the following: a) increased release of inflammation-related cytokines; b) increased production of oxygen free radicals associated with ischemia/reperfusion injury and states of low tissue perfusion; c) expression and release of heat shock proteins from tissue cells and the liver; d) elevated glucocorticoid concentrations after adrenal cortex activation; and e) release of bacterial products into the systemic circulation.

CONCLUSION

The most important MODS-related pathophysiologic conditions known to date have been shown to affect programmed cell death rates in almost all cell types. Organ-specific cell death involving both parenchymal and microvasculature endothelial cells is conceivably underlying organ dysfunction. The hypothesis that increased apoptotic rates are involved in organ dysfunction may provide a unifying theory for the pathophysiology of MODS.

Ionizing radiation alters Fas antigen ligand at the cell surface and on exfoliated plasma membrane-derived vesicles: implications for apoptosis and intercellular signaling

Resident proteins that reside on the plasma membrane are continually exfoliated from the cell surface. Exfoliation is a selective, energy-dependent process that mediates intercellular communication. Ionizing radiation modulates the expression of many plasma membrane-bound growth regulators, including the "death" ligand, TNFSF6 (formerly known as FasL, CD95L). Here we report that ionizing radiation induces dose-dependent up-regulation of TNFSF6 on plasma membranes purified from SW620 cells, a TNFSF6-expressing colon cancer cell line. Serum-free medium conditioned by exposed and control cells was collected and exfoliated vesicles were obtained by ultracentrifugation. Western blot analysis of vesicles from unexposed cells and from cells treated with 10 Gy showed increased amounts of TNFSF6 compared to that on vesicles from unexposed cells. Cells treated with 4 Gy released vesicles having a low level of TNFSF6 on their surface relative to that on vesicles exfoliated from unexposed cells. When assayed for bioactivity, vesicles from unexposed cells induced the greatest level of apoptosis in TNFRSF6 (formerly known as FAS) receptor-bearing Jurkat cells (cell surviving fraction of 43.7 +/- 6.1; P < 0.05), followed by vesicles collected from cells treated with 4 Gy (79.6 +/- 2.6%; P < 0.05). Despite having a high level of TNFSF6 by Western analysis, vesicles collected from cells exposed to 10 Gy display minimal biological activity (77.9 +/- 3.2%; P < 0.05), suggesting that modification of the vesicle-associated ligand has occurred. Our results indicate that ionizing radiation increases the level of TNFSF6 exfoliated on extracellular vesicles. The data may provide a mechanism for abscopal and bystander effects after irradiation.

Soluble Fas in serum from patients with renal cell carcinoma

OBJECTIVES

Fas/APO- 1 is an apoptosis-signaling cell-surface receptor belonging to the tumor necrosis factor receptor family. The Fas-Fas ligand system plays an important role in cytotoxic T-lymphocyte-mediated or natural killer cell-mediated cytotoxicity against tumor cells. Soluble Fas (sFas), generated by alternative splicing, has been reported to antagonize the interaction of cell-surface Fas with Fas ligand. This study examined the level of sFas in the serum of patients with renal cell carcinoma (RCC) and investigated the correlation between the sFas level and clinicopathologic parameters of RCC.

METHODS

Using reverse transcriptase-polymerase chain reaction, we examined the production of sFas messenger RNA (mRNA) from the cultured human RCC cell lines ACHN and OUR-10 and from surgical specimens. We also measured sFas levels in the serum of 31 patients with RCC before and after nephrectomy using an sFas-specific enzyme-linked immunosorbent assay.

RESULTS

mRNA of sFas was identified both in cultured ACHN cells and human RCC tissues, although mRNA of wild-type Fas was exclusively predominant. The level of sFas in the serum of patients with RCC was significantly higher than that of normal controls, but sFas was not detectable in the supernatant of cultured renal cancer cells. Preoperative and postoperative serum sFas levels did not clearly correlate with the patients' age or sex or with histologic stage, grade, or cell type of RCC. The serum sFas level in patients with RCC correlated with tumor size. In 24 of the 31 cases, radical nephrectomy reduced the serum sFas level within 3 months.

CONCLUSIONS

Our results suggest that the elevated serum sFas level in patients with RCC might not be derived from the tumor itself but might reflect an immune response to the tumor burden. Serum sFas may be a useful indicator of tumor burden in patients with RCC.

Different serum soluble Fas levels in patients with allergic rhinitis and bronchial asthma

BACKGROUND

The pathogeneses of allergic rhinitis and bronchial asthma are believed to be closely mutually related because of the similar dynamics of allergy-inducing cells and molecules and clinical overlap. In this study, we compared these diseases in the dynamics of cell apoptosis-regulating molecules.

METHODS

Allergic rhinitis patients (n=36), bronchial asthma patients (n=22), and healthy subjects (n=32) were subjected to measurement of serum (soluble Fas) (sFas) levels during the stable and attack disease phases by a sandwich enzyme-linked immunosorbent assay.

RESULTS

Serum sFas levels in patients with allergic rhinitis during the attack phase were significantly lower (P<0.0001) than those in healthy individuals. There were no differences between them during the attack and stable disease phases. In contrast, serum sFas levels in patients with bronchial asthma during the attack phase were higher (P<0.0005) than those in healthy individuals. Interestingly, the levels during the attack phase were lower (P<0.002) than those during the stable phase.

CONCLUSIONS

Our results suggest a different pathogenesis for allergic rhinitis and bronchial asthma at the cell apoptosis-linked step.