CD95L/FasL and TRAIL in tumour surveillance and cancer therapy

EX527, a sirtuins 1 inhibitor, sensitizes T-cell leukemia to death receptor-mediated apoptosis by downregulating cellular FLICE inhibitory protein

Death receptor-mediated extrinsic apoptosis system had been developed as a promising therapeutic strategy in clinical oncology, such as TRAIL therapy. However, multiple studies have demonstrated that TRAIL resistance is the biggest problem for disappointing clinical trials despite preclinical success. Targeting cellular FLICE inhibitory protein (cFLIP) is one strategy of combinatorial therapies to overcome resistance to DR-mediated apoptosis due to its negative regulator of extrinsic apoptosis. E × 527 (Selisistat) is a specific inhibitor of SIRT1 activity with safe and well tolerance in clinical trials. Here, we show that E × 527 could strengthen significantly activation of rhFasL-mediated apoptotic signaling pathway and increased apoptotic rate of T leukemia cells with high expression of cFLIP. Mechanically, Inhibition of SIRT1 by E × 527 increased polyubiquitination level of cFLIP via increasing acetylation of Ku70, which could promote proteosomal degradation of cFLIP protein. It implied that combinatorial therapies of E × 527 plus TRAIL may have a potential as a novel clinical application for TRAIL-resistant hematologic malignancies.

Signaling controversy and future therapeutical perspectives of targeting sphingolipid network in cancer immune editing and resistance to tumor necrosis factor-α immunotherapy

Anticancer immune surveillance and immunotherapies trigger activation of cytotoxic cytokine signaling, including tumor necrosis factor-α (TNF-α) and TNF-related apoptosis-inducing ligand (TRAIL) pathways. The pro-inflammatory cytokine TNF-α may be secreted by stromal cells, tumor-associated macrophages, and by cancer cells, indicating a prominent role in the tumor microenvironment (TME). However, tumors manage to adapt, escape immune surveillance, and ultimately develop resistance to the cytotoxic effects of TNF-α. The mechanisms by which cancer cells evade host immunity is a central topic of current cancer research. Resistance to TNF-α is mediated by diverse molecular mechanisms, such as mutation or downregulation of TNF/TRAIL receptors, as well as activation of anti-apoptotic enzymes and transcription factors. TNF-α signaling is also mediated by sphingosine kinases (SphK1 and SphK2), which are responsible for synthesis of the growth-stimulating phospholipid, sphingosine-1-phosphate (S1P). Multiple studies have demonstrated the crucial role of S1P and its transmembrane receptors (S1PR) in both the regulation of inflammatory responses and progression of cancer. Considering that the SphK/S1P/S1PR axis mediates cancer resistance, this sphingolipid signaling pathway is of mechanistic significance when considering immunotherapy-resistant malignancies. However, the exact mechanism by which sphingolipids contribute to the evasion of immune surveillance and abrogation of TNF-α-induced apoptosis remains largely unclear. This study reviews mechanisms of TNF-α-resistance in cancer cells, with emphasis on the pro-survival and immunomodulatory effects of sphingolipids. Inhibition of SphK/S1P-linked pro-survival branch may facilitate reactivation of the pro-apoptotic TNF superfamily effects, although the role of SphK/S1P inhibitors in the regulation of the TME and lymphocyte trafficking should be thoroughly assessed in future studies.

Small EV in plasma of triple negative breast cancer patients induce intrinsic apoptosis in activated T cells

Small extracellular vesicles (sEV) in TNBC patients' plasma promote T cell dysfunction and tumor progression. Here we show that tumor cell-derived exosomes (TEX) carrying surface PDL-1, PD-1, Fas, FasL, TRAIL, CTLA-4 and TGF-β1 induce apoptosis of CD8+T and CD4+T cells but spare B and NK cells. Inhibitors blocking TEX-induce receptor/ligand signals and TEX pretreatments with proteinase K or heat fail to prevent T cell apoptosis. Cytochalasin D, Dynosore or Pit Stop 2, partly inhibit TEX uptake but do not prevent T cell apoptosis. TEX entry into T cells induces cytochrome C and Smac release from mitochondria and caspase-3 and PARP cleavage in the cytosol. Expression of survival proteins is reduced in T cells undergoing apoptosis. Independently of external death receptor signaling, TEX entry into T cells induces mitochondrial stress, initiating relentless intrinsic apoptosis, which is responsible for death of activated T cells in the tumor-bearing hosts. The abundance of TEX in cancer plasma represents a danger for adoptively transferred T cells, limiting their therapeutic potential.

Regulation of the tumor immune microenvironment by cancer-derived circular RNAs

Circular RNA (circRNAs) is a covalently closed circular non-coding RNA formed by reverse back-splicing from precursor messenger RNA. It is found widely in eukaryotic cells and can be released to the surrounding environment and captured by other cell types. This, circRNAs serve as connections between different cell types for the mediation of multiple signaling pathways. CircRNAs reshape the tumor microenvironment (TME), a key factor involved in all stages of cancer development, by regulating epithelial-stromal transformation, tumor vascularization, immune cell function, and inflammatory responses. Immune cells are the most abundant cellular TME components, and they have profound toxicity to cancer cells. This review summarizes circRNA regulation of immune cells, including T cells, natural killer cells, and macrophages; highlights the impact of circRNAs on tumor progression, treatment, and prognosis; and indicates new targets for tumor immunotherapy.

Vesicle Induced Receptor Sequestration: Mechanisms behind Extracellular Vesicle-Based Protein Signaling

Extracellular vesicles (EVs) are fundamental for proper physiological functioning of multicellular organisms. By shuttling nucleic acids and proteins between cells, EVs regulate a plethora of cellular processes, especially those involved in immune signalling. However, the mechanistic understanding concerning the biophysical principles underlying EV-based communication is still incomplete. Towards holistic understanding, particular mechanisms explaining why and when cells apply EV-based communication and how protein-based signalling is promoted by EV surfaces are sought. Here, the authors study vesicle-induced receptor sequestration (VIRS) as a universal mechanism augmenting the signalling potency of proteins presented on EV-membranes. By bottom-up reconstitution of synthetic EVs, the authors show that immobilization of the receptor ligands FasL and RANK on EV-like vesicles, increases their signalling potential by more than 100-fold compared to their soluble forms. Moreover, the authors perform diffusion simulations within immunological synapses to compare receptor activation between soluble and EV-presented proteins. By this the authors propose vesicle-triggered local clustering of membrane receptors as the principle structural mechanism underlying EV-based protein presentation. The authors conclude that EVs act as extracellular templates promoting the local aggregation of membrane receptors at the EV contact site, thereby fostering inter-protein interactions. The results uncover a potentially universal mechanism explaining the unique structural profit of EV-based intercellular signalling.

Protein Kinase D3 Promotes the Reconstruction of OSCC Immune Escape Niche Via Regulating MHC-I and Immune Inhibit Molecules Expression

Protein kinase D3 (PKD3) has been involved in various aspects of tumorigenesis and progression in many kinds of cancer types. However, whether PKD3 regulates immune escape in tumor microenvironment is rarely reported. Here, we explored the function and mechanism of PKD3 in reconstructing the immune escape niche of oral squamous cell carcinoma (OSCC). Both the Western blotting analysis in OSCC cells and the gene expression correlation analysis from The Cancer Genome Atlas shows that the expression of Fas and programmed cell death-ligand 1 (PD-L1) was positively correlated with PKD3, while major histocompatibility complex-I (MHC-I) was negatively correlated with PKD3. Knockdown of PKD3 significantly decreased the expression of Fas and PD-L1 and increased the expression of MHC-I. Furthermore, when PKD3 was overexpressed in oral precancerous cells, Fas, PD-L1, and MHC-I showed an opposite trend to that observed when PKD3 was knocked down. In addition, PKD3 knockdown decreased the secretion of transforming growth factor β, CC-chemokine ligand 21, interleukin-10 by OSCC cells. Finally, the tumor cell antigen, which was extracted from PKD3 knockdown OSCC cells, significantly induced the growth and activation of T lymphocytes. These results demonstrate that PKD3 promotes the immune escape of OSCC cells by regulating the expression of Fas, PD-L1, MHC-I, transforming growth factor β, CC-chemokine ligand 21, interleukin-10, and plays a key role in reconstructing the tumor immune escape niche.

Regulation of Cancer Metastasis by TRAIL/Death Receptor Signaling

Death ligands such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL; TNFSF10) and their corresponding death receptors (e.g., DR5) not only initiate apoptosis through activation of the extrinsic apoptotic pathway but also exert non-apoptotic biological functions such as regulation of inflammation and cancer metastasis. The involvement of the TRAIL/death receptor signaling pathway in the regulation of cancer invasion and metastasis is complex as both positive and negative roles have been reported. The underlying molecular mechanisms are even more complicated. This review will focus on discussing current knowledge in our understanding of the involvement of TRAIL/death receptor-mediated signaling in the regulation of cancer cell invasion and metastasis.

Downregulation of death receptor 4 is tightly associated with positive response of EGFR mutant lung cancer to EGFR-targeted therapy and improved prognosis

Death receptor 4 (DR4), a cell surface receptor, mediates apoptosis or induces inflammatory cytokine secretion upon binding to its ligand depending on cell contexts. Its prognostic impact in lung cancer and connection between EGFR-targeted therapy and DR4 modulation has not been reported and thus was the focus of this study. Methods: Intracellular protein alterations were measured by Western blotting. Cell surface protein was detected with antibody staining and flow cytometry. mRNA expression was monitored with qRT-PCR. Gene transactivation was analyzed with promoter reporter assay. Drug dynamic effects in vivo were evaluated using xenografts. Gene modulations were achieved with gene overexpression and knockdown. Proteins in human archived tissues were stained with immunohistochemistry. Results: EGFR inhibitors (e.g., osimertinib) decreased DR4 levels only in EGFR mutant NSCLC cells and tumors, being tightly associated with induction of apoptosis. This modulation was lost once cells became resistant to these inhibitors. Increased levels of DR4 were detected in cell lines with acquired osimertinib resistance and in NSCLC tissues relapsed from EGFR-targeted therapy. DR4 knockdown induced apoptosis and augmented apoptosis when combined with osimertinib in both sensitive and resistant cell lines, whereas enforced DR4 expression significantly attenuated osimertinib-induced apoptosis. Mechanistically, osimertinib induced MARCH8-mediated DR4 proteasomal degradation and suppressed MEK/ERK/AP-1-dependent DR4 transcription, resulting in DR4 downregulation. Moreover, we found that DR4 positive expression in human lung adenocarcinoma was significantly associated with poor patient survival. Conclusions: Collectively, we suggest that DR4 downregulation is coupled to therapeutic efficacy of EGFR-targeted therapy and predicts improved prognosis, revealing a previously undiscovered connection between EGFR-targeted therapy and DR4 modulation.

Tumor-induced neurogenesis and immune evasion as targets of innovative anti-cancer therapies

Normal cells are hijacked by cancer cells forming together heterogeneous tumor masses immersed in aberrant communication circuits that facilitate tumor growth and dissemination. Besides the well characterized angiogenic effect of some tumor-derived factors; others, such as BDNF, recruit peripheral nerves and leukocytes. The neurogenic switch, activated by tumor-derived neurotrophins and extracellular vesicles, attracts adjacent peripheral fibers (autonomic/sensorial) and neural progenitor cells. Strikingly, tumor-associated nerve fibers can guide cancer cell dissemination. Moreover, IL-1β, CCL2, PGE2, among other chemotactic factors, attract natural immunosuppressive cells, including T regulatory (Tregs), myeloid-derived suppressor cells (MDSCs), and M2 macrophages, to the tumor microenvironment. These leukocytes further exacerbate the aberrant communication circuit releasing factors with neurogenic effect. Furthermore, cancer cells directly evade immune surveillance and the antitumoral actions of natural killer cells by activating immunosuppressive mechanisms elicited by heterophilic complexes, joining cancer and immune cells, formed by PD-L1/PD1 and CD80/CTLA-4 plasma membrane proteins. Altogether, nervous and immune cells, together with fibroblasts, endothelial, and bone-marrow-derived cells, promote tumor growth and enhance the metastatic properties of cancer cells. Inspired by the demonstrated, but restricted, power of anti-angiogenic and immune cell-based therapies, preclinical studies are focusing on strategies aimed to inhibit tumor-induced neurogenesis. Here we discuss the potential of anti-neurogenesis and, considering the interplay between nervous and immune systems, we also focus on anti-immunosuppression-based therapies. Small molecules, antibodies and immune cells are being considered as therapeutic agents, aimed to prevent cancer cell communication with neurons and leukocytes, targeting chemotactic and neurotransmitter signaling pathways linked to perineural invasion and metastasis.

Toxicology and Pharmacokinetic Studies in Mice and Nonhuman Primates of the Nontoxic, Efficient, Targeted Hexameric FasL: CTLA4-FasL

Cytotoxic T-lymphocyte antigen 4 (CTLA4)-FasL, a homo-hexameric signal converter protein, is capable of inducing robust apoptosis in malignant cells of the B-cell lineage expressing its cognate B7 and Fas targets, while sparing nonmalignant ones. This fusion protein's striking proapoptotic efficacy stems from its complementary abilities to coordinately activate apoptotic signals and abrogate antiapoptotic ones. A limiting factor in translating FasL or Fas receptor agonists into the clinic has been lethal hepatotoxicity. Here, we establish CTLA4-FasL's in vivo efficacy in multiple murine and xenograft models, for both systemic and subcutaneous tumors. Significantly, good laboratory practice (GLP) toxicology studies in mice indicate that CTLA4-FasL given repeatedly at doses up to five times the effective dose was well-tolerated and resulted in no significant adverse events. An equivalent single dose of CTLA4-FasL administered to nonhuman primates was also well-tolerated, albeit with a moderate dose-dependent leukopenia that was completely reversible. Interestingly, monkey peripheral blood mononuclear cells were more sensitive to CTLA4-FasL-induced apoptosis when tested in vitro. In both species, there was short-term elevation in serum levels of IL6, IL2, and IFNγ, although this was not associated with clinical signs of proinflammatory cytokine release, and further, this cytokine elevation could be completely prevented by dexamethasone premedication. Liver toxicity was not observed in either species, as confirmed by serum liver enzyme levels and histopathologic assessment. In conclusion, CTLA4-FasL emerges from animal model studies as an effective and safe agent for targeted FasL-mediated treatment of B7-expressing aggressive B-cell lymphomas.

Loss of Fas Expression and Function Is Coupled with Colon Cancer Resistance to Immune Checkpoint Inhibitor Immunotherapy

Despite the remarkable efficacy of immune checkpoint inhibitor (ICI) immunotherapy in various types of human cancers, colon cancer, except for the approximately 4% microsatellite-instable (MSI) colon cancer, does not respond to ICI immunotherapy. ICI acts through activating CTLs that use the Fas-FasL pathway as one of the two effector mechanisms to suppress tumor. Cancer stem cells are often associated with resistance to therapy including immunotherapy, but the functions of Fas in colon cancer apoptosis and colon cancer stem cells are currently conflicting and highly debated. We report here that decreased Fas expression is coupled with a subset of CD133⁺CD24^lo colon cancer cells in vitro and in vivo. Consistent of the lower Fas expression level, this subset of CD133⁺CD24^loFas^lo colon cancer cells exhibits decreased sensitivity to FasL-induced apoptosis. Furthermore, FasL selectively enriches CD133⁺CD24^loFas^lo colon cancer cells. CD133⁺CD24^loFas^lo colon cancer cells exhibit increased lung colonization potential in experimental metastatic mouse models and decreased sensitivity to tumor-specific CTL adoptive transfer and ICI immunotherapies. Interestingly, FasL challenge selectively enriched this subset of colon cancer cells in microsatellite-stable (MSS) but not in the MSI human colon cancer cell lines. Consistent with the downregulation of Fas expression in CD133⁺CD24^lo cells, lower Fas expression level is significantly correlated with decreased survival in patients with human colon cancer. IMPLICATIONS: Our data determine that CD133⁺CD24^loFas^lo colon cancer cells are capable to evade Fas-FasL cytotoxicity of tumor-reactive CTLs and targeting this subset of colon cancer cells is potentially an effective approach to suppress colon cancer immune evasion.

CD56bright natural killer cells induce HBsAg reduction via cytolysis and cccDNA decay in long-term entecavir-treated patients switching to peginterferon alfa-2a

HBV surface antigen (HBsAg) reduction is well observed in chronic hepatitis B (CHB) patients treated with pegylated interferon alpha-2a (PegIFNα). However, the mechanism of HBsAg suppression has not been fully elucidated. Twenty-seven of 55 entecavir-treated CHB e antigen positive patients were switched to PegIFNα treatment (Group A) whereas 28 patients continued entecavir treatment (Group B). The percentage or absolute number of CD56^bright /CD56^dim NK cells, expression of receptors and cytokines were evaluated by flow cytometry for 48 weeks and correlated with treatment efficacy. In vitro, purified NK cells were co-cultured with HepAD38 cells for measurement of HBsAg, apoptosis and covalently closed circular DNA (cccDNA). In association with a reduction of HBsAg, the percentage and absolute number of CD56^bright NK cells was significantly elevated in patients in group A, especially in Virologic Responders (VRs, HBsAg decreased). Furthermore, the percentage of NKp30⁺ , NKp46⁺ , TRAIL⁺ , TNF-α⁺ and IFNγ⁺ CD56^bright NK cells were significantly expanded in Group A, which were positively correlated with the decline of HBsAg at week 48. In vitro, peripheral NK cells from Group A induced a decline of HBsAg in comparison with NK cells from Group B which was significantly inhibited by anti-TRAIL, anti-TNF-α and anti-IFNγ antibodies. Furthermore, apoptosis of HepAD38 cells and levels of cccDNA, were significantly reduced by TRAIL⁺ and TNF-α⁺ /IFNγ⁺ NK cells from Group A, respectively. A functional restoration of CD56^bright NK cells in entecavir-treated patients who were switched to PegIFNα contributes to HBsAg and cccDNA clearance through TRAIL-induced cytolysis and TNF-α/IFNγ-mediated noncytolytic pathways.

Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Gene Polymorphisms and Hepatitis B Virus Infection

Background:

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an apoptotic molecule with a key role in the apoptosis of tumors and virus-infected cells. The association of 1525G/A and 1595C/T polymorphisms in the region of 3’ UTR on the TRAIL gene has been shown in many cancers and diseases. Polymorphism at the positions of 1525G/A and 1595C/T might influence the clearance of hepatitis B virus (HBV).

Objectives:

This study was carried out to determine the role of the TRAIL gene polymorphisms in clinical outcome of HBV infection.

Patients and Methods:

Polymerase chain reaction-based restriction fragment length polymorphism (PCR–RFLP) was applied to genotype TRAIL polymorphisms at positions 1525G/A and 1595C/T. To evaluate the TRAIL gene polymorphism in the 3’ UTR region at position 1525G/A and 1595C/T, 147 patients with HBV infection were divided into three different groups of chronic hepatitis (n = 52), cirrhosis (n = 33), and carrier (n = 62) and there was a group of 101 healthy controls.

Results:

Our data showed that genotypes 1525G/A and 1595C/T were in complete linkage disequilibrium and the genotype frequencies at the two positions were the same. No significant differences in frequencies of genotype and alleles at positions 1525G/A and 1595C/T were observed between all the three groups (P value > 0.05).

Conclusions:

According to our result, 1525G/A and 1595C/T were in strong linkage disequilibrium and the polymorphisms of the TRAIL gene in the 3’ UTR region were not associated with the outcome of HBV infection.

CD4+VEGFR1(HIGH) T cell as a novel Treg subset regulates inflammatory bowel disease in lymphopenic mice

Regulatory T cells (Tregs) are a specialized subpopulation of T cells that control the immune response and thereby maintain immune system homeostasis and tolerance to self-antigens. Many subsets of CD4(+) Tregs have been identified, including Foxp3(+), Tr1, Th3, and Foxp3neg iT(R)35 cells. In this study, we identified a new subset of CD4(+)VEGFR1(high) Tregs that have immunosuppressive capacity. CD4(+)VEGFR1high T cells, which constitute approximately 1.0% of CD4(+) T cells, are hyporesponsive to T-cell antigen receptor stimulation. Surface marker and FoxP3 expression analysis revealed that CD4(+)VEGFR1(high) T cells are distinct from known Tregs. CD4(+)VEGFR1(high) T cells suppressed the proliferation of CD4(+)CD25(-) T cell as efficiently as CD4(+)CD25(high) natural Tregs in a contact-independent manner. Furthermore, adoptive transfer of CD4(+)VEGFR1(+) T cells from wild type to RAG-2-deficient C57BL/6 mice inhibited effector T-cell-mediated inflammatory bowel disease. Thus, we report CD4(+) VEGFR1(high) T cells as a novel subset of Tregs that regulate the inflammatory response in the intestinal tract.

RIP1 modulates death receptor mediated apoptosis and autophagy in macrophages

Macrophages are responsible for defending against diverse pathogens and play a crucial role in the innate immune system. Macrophage's lifespan is determined by homeostatic balance between survival and apoptosis. Here we report that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) triggers both apoptosis and autophagy in human U937 cells. Inhibition of autophagy facilitates TRAIL-induced apoptosis, suggesting that autophagy of macrophages protects against TRAIL-induced apoptosis. TRAIL treatment influences the expression of death receptors, indicating that TRAIL-induced apoptosis and autophagy are mediated by death receptors. RIP1 ubiquitination and expression regulate apoptosis and autophagy. Furthermore, expression and bioactivity of the p43/41-caspase-8 variant are critical to TRAIL-induced autophagy and apoptosis. Knockdown of RIP1 suppresses autophagy in macrophage. These data demonstrate that RIP1 is essential for the regulation of death receptor mediated autophagy and apoptosis. The results in this study contribute to understanding the regulation of autophagy and apoptosis in macrophages, and shed lights on death receptor-targeted therapy for cancer, inflammation and autoimmune diseases.

Systemic tumor-specific gene delivery

The objective of a systemically administered cancer gene therapy is to achieve gene expression that is isolated to the tumor tissue. Unfortunately, viral systems have strong affinity for the liver, and delivery from non-viral cationic systems often results in high expression in the lungs. Non-specific delivery to these organs must be overcome if tumors are to be aggressively treated with genes such as IL-12 which activates a tumor immune response, and TNF-alpha which can induce tumor cell apoptosis. Techniques which have led to specific expression in tumor tissue include receptor targeting through ligand conjugation, utilization of tumor specific promoters and viral mutation in order to take advantage of proteins overexpressed in tumor cells. This review analyzes these techniques applied to liposomal, PEI, dendrimer, stem cell and viral gene delivery systems in order to determine the techniques that are most effective in achieving tumor specific gene expression after systemic administration.

Critical role of the death receptor pathway in the antitumoral effects induced by hispanolone derivatives

Labdane diterpenoids have a broad spectrum of biological activities including antibacterial, antiviral and anti-inflammatory properties. However, little is known about their possible role in the apoptotic cell death machinery. Here, we report that hispanolone derivatives, a group of labdane diterpenoids, induce apoptosis in different tumor cell lines by activating caspase-8 with subsequent participation of mitochondrial signaling. Activation of caspase-8 by hispanolone derivatives was followed by a decrease in mitochondrial membrane potential, the release of apoptotic factors from mitochondria to the cytosol, and activation of caspases-9 and 3. Hispanolone derivatives also led to a time-dependent cleavage of Bid. Inhibition of caspase-8 abrogated these processes, suggesting that the death receptor pathway has a critical role in the apoptotic events induced by hispanolone derivatives. In addition, silencing death receptors with small interfering RNA s or pretreating cells with neutralizing antibodies to Fas ligand, tumor necrosis factor receptor 1 (TNF-R1), and TNF-α receptor 2 (TRAIL) inhibited diterpenoid-induced apoptosis, revealing it to be dependent on these death receptors. Interestingly, hispanolone derivatives had no effect on non-tumor cells. Consistently, in vivo bioluminescence imaging corroborates this antineoplasic effect, as hispanolone derivatives significantly decrease cancer growth in tumor xenograft assays. These data demostrate the antitumoral effects of hispanolone derivatives and provide relevant preclinical validation for the use of these compounds as potent therapeutic agents in cancer treatment.

The immune signature of CD8(+)CCR7(+) T cells in the peripheral circulation associates with disease recurrence in patients with HNSCC

PURPOSE

Patients with cancer have an increased frequency of circulating apoptosis-sensitive CD8(+)CCR7(neg) T cells and few CD8(+)CCR7(+) T cells versus normal controls. The functional and clinical significance of this imbalance was investigated using peripheral blood of patients with squamous cell carcinoma of the head and neck (HNSCC).

EXPERIMENTAL DESIGN

The frequency of circulating CD8(+) T cells co-expressing CCR7, CD45RO, CD28, and Annexin V (ANXV) was evaluated in 67 patients and 57 normal controls by flow cytometry. Spearman rank correlations among immunophenotypic profiles were analyzed. Recursive partitioning classified subjects as patients or normal controls based on CD8(+)CCR7(+) T-cell percentages. Kaplan-Meier plots estimated disease-free survival (DFS).

RESULTS

The CD8(+)CCR7(+) T-cell frequency was low, whereas that of total CD8(+)CCR7(neg) and ANXV-binding CD8(+)CCR7(neg) T cells was higher in patients with HNSCC than in normal controls (P < 0.001-0.0001). ANXV binding correlated with the absence of CCR7 on CD8(+) T cells (P < 0.001). ANXV binding was negatively correlated with the CD8(+)CD45RO(neg)CCR7(+) (T(N)) cell frequency (P < 0.01) but positively correlated (P < 0.01) with that of CD8(+)CD45RO(+)CCR7(+) (T(CM)) T cells and of the two CCR7(neg) subsets (T(PM) and T(TD)). In recursive partitioning models, the CD8(+)CCR7(+) T-cell frequency of 31% distinguished patients from normal controls with 77% to 88% accuracy after cross-validation. In 25 patients tested before any therapy, the CD8(+)CCR7(+) T-cell frequency of less than 28% predicted disease recurrence within 4 years of definitive therapy (P < 0.0115).

CONCLUSION

The CD8(+)CCR7(+) T-cell frequency in HNSCC patients' blood tested at diagnosis can discriminate them from normal controls and predicts disease recurrence.

Thiourea compound AW00178 sensitizes human H1299 lung carcinoma cells to TRAIL-mediated apoptosis

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) triggers apoptosis in a wide variety of cancer cells. Recently, cancer cell resistance to TRAIL-mediated apoptosis has become a challenging issue in the development of TRAIL-based anti-cancer therapies. In this study, we found that 1-(5-chloro-2-methyl-phenyl)-3-[4-(5-trifluoromethyl-pyrazol-1-yl)-phenyl]-thiourea (AW00178) was able to sensitize TRAIL-resistant human lung cancer H1299 cells to TRAIL-mediated apoptosis. Treatment with AW00178, either alone or in combination with TRAIL, induced the expression of CHOP, a protein related to TRAIL sensitivity, and reduced the expression of survivin, an anti-apoptotic protein involved in TRAIL resistance. Additionally, AW00178, alone or in combination with TRAIL, induced the activation of c-Jun and inactivation of Akt. A pharmacologic inhibition study revealed that c-Jun activation and Akt inactivation were strongly related to CHOP induction and survivin down-regulation, respectively. In summary, these results suggested that AW00178 mediated sensitization to TRAIL-mediated apoptosis in H1299 cells by increasing sensitivity and decreasing resistance to TRAIL via the induction of c-Jun-dependent CHOP expression and the reduction of Akt-dependent survivin expression, respectively.

CD34+ gene expression profiling of individual children with very severe aplastic anemia indicates a pathogenic role of integrin receptors and the proapoptotic death ligand TRAIL

BACKGROUND Very severe aplastic anemia is characterized by a hypoplastic bone marrow due to destruction of CD34(+) stem cells by autoreactive T cells. Investigation of the pathomechanism by patient-specific gene expression analysis of the attacked stem cells has previously been impractical because of the scarcity of these cells at diagnosis.

DESIGN AND METHODS

Employing unbiased RNA amplification, patient-specific gene expression profiling was carried out for CD34(+) cells from patients newly diagnosed with very severe aplastic anemia (n=13), refractory anemia (n=8) and healthy controls (n=10). These data were compared to profiles of myelodysplastic disease (n=55), including refractory anemia (n=18). To identify possible targets of autoimmune attack, presence of autoreactive antibodies was tested in pre-therapeutic sera of patients with very severe aplastic anemia (n=19).

RESULTS

CD34(+) gene expression profiling distinguished between healthy controls, children with aplastic or refractory anemia and clonal disease. Interferon stimulated genes such as the apoptosis inducing death ligand TRAIL were strongly up-regulated in CD34(+) cells of patients with aplastic anemia, in particular in patients responding to immunosuppressive treatment. In contrast, mRNA expression of integrin GPVI and the integrin complexes GPIa/IIa, GPIIb/IIIa, GPIB/GPIX/GPV was significantly down-regulated and corresponding antibodies were detected in 7 of 11 profiled patients and in 11 of 19 aplastic anemia patients. CONCLUSIONS As a potential diagnostic tool, patient-specific gene expression profiling of CD34(+) stem cells made it possible to make the difficult differential diagnosis of most patients with aplastic and refractory anemia. Profiling indicated a prognostic correlation of TRAIL expression and patient benefit from immunosuppressive therapy. Downregulation of integrin expression and concurrent presence of autoreactive anti-integrin-antibodies suggested a previously unrecognized pathological role of integrins in aplastic anemia.

Targeting the Fas/FasL signaling pathway in cancer therapy

INTRODUCTION

The Fas/FasL system plays a significant role in tumorigenesis. Research has shown that its impairment in cancer cells may lead to apoptosis resistance and contribute to tumor progression. Thus, the development of effective therapies targeting the Fas/FasL system may play an important role in the fight against cancer.

AREAS COVERED

In this review the recent literature on targeting the Fas/FasL system for therapeutic exploitation at different levels is reviewed. Promising pre-clinical approaches and various exceptions are highlighted. The potential of combined therapies is also explored, whereby tumor sensitivity to Fas-mediated apoptosis is restored, before an effective targeted therapy is employed.

EXPERT OPINION

The success of the Fas/FasL system targeting for therapeutics will require a better understanding of the alterations conferring resistance, in order to use the most appropriate sensitizing chemotherapeutic or radiotherapeutic agents in combination with effective targeted therapies.

The effect of lentivirus-mediated expression of tumor necrosis factor related apoptosis-inducing ligand and shRNA against Bcl-2 on the growth of lymphoma cells

It has been well established that tumor necrosis factor related apoptosis-inducing ligand (TRAIL) effectively induces apoptosis in tumor cells. However, tumor resistance to TRAIL, especially of hematological tumor cells, has become a major problem in the potential use of TRAIL in clinical practice. Among many factors that contribute to TRAIL resistance, overexpression of Bcl-2 is commonly seen in many kinds of tumors, particularly in lymphoma. In this study, we developed a lentivirus system that encodes recombinant human TRAIL cDNA for overexpression and Bcl-2 shRNA for down-regulation of Bcl-2 (lenti-TRAIL-shBcl-2) simultaneously. The efficiency of recombinant lentiviruses infecting different lymphoma cell lines was assessed by flow cytometric analysis and fluorescence microscopy. Reverse transcription polymerase chain reaction and Western blot assay were carried out to evaluate the expression of TRAIL and Bcl-2 in lymphoma cells after infection. We also examined the growth inhibition effect of recombinant lentivirus on lymphoma cell proliferation by CCK-8 (Cell Counting Kit-8) assay and its effect on bystander cells by flow cytometric analysis. The results showed that lymphoma cells were effectively infected by recombinant lentivirus and that TRAIL was exogenously expressed and Bcl-2 expression was down-regulated in lymphoma cells simultaneously. Results of this study demonstrated that lenti-TRAIL-shBcl-2 induced apoptosis in bystander cells as well as infected lymphoma cells and inhibited the growth of lymphoma cells.

High cell surface death receptor expression determines type I versus type II signaling

Previous studies have suggested that there are two signaling pathways leading from ligation of the Fas receptor to induction of apoptosis. Type I signaling involves Fas ligand-induced recruitment of large amounts of FADD (FAS-associated death domain protein) and procaspase 8, leading to direct activation of caspase 3, whereas type II signaling involves Bid-mediated mitochondrial perturbation to amplify a more modest death receptor-initiated signal. The biochemical basis for this dichotomy has previously been unclear. Here we show that type I cells have a longer half-life for Fas message and express higher amounts of cell surface Fas, explaining the increased recruitment of FADD and subsequent signaling. Moreover, we demonstrate that cells with type II Fas signaling (Jurkat or HCT-15) can signal through a type I pathway upon forced receptor overexpression and that shRNA-mediated Fas down-regulation converts cells with type I signaling (A498) to type II signaling. Importantly, the same cells can exhibit type I signaling for Fas and type II signaling for TRAIL (TNF-α-related apoptosis-inducing ligand), indicating that the choice of signaling pathway is related to the specific receptor, not some other cellular feature. Additional experiments revealed that up-regulation of cell surface death receptor 5 levels by treatment with 7-ethyl-10-hydroxy-camptothecin converted TRAIL signaling in HCT116 cells from type II to type I. Collectively, these results suggest that the type I/type II dichotomy reflects differences in cell surface death receptor expression.

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

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

Overexpression of IL-32alpha increases natural killer cell-mediated killing through up-regulation of Fas and UL16-binding protein 2 (ULBP2) expression in human chronic myeloid leukemia cells

IL-32 was recently identified as a proinflammatory cytokine that is induced by IL-18 in natural killer (NK) cells and is highly correlated with inflammatory disorders. However, the relationship between IL-32 and tumor progression is still unknown. In this study, we investigated whether overexpression of IL-32 affects susceptibility of chronic myeloid leukemia (CML) cells to NK cells. Interestingly, IL-32α-overexpressing CML cell lines, K562, Kcl22, and BV173, showed higher NK cell-mediated killing. Flow cytometry analysis revealed that overexpression of IL-32α induced increased expression of Fas and UL16-binding protein 2 (ULBP2) in CML cells. The direct relationship between overexpression of surface molecules by IL-32α and increased NK cell-mediated killing was confirmed by Fas or ULBP2 siRNA transfection. IL-32α-induced Fas and ULBP2 expression are regulated p38 MAPK. In addition, the transcription factor Ets1 plays a key role in ULBP2 specific expression by IL-32α overexpression in ULBP family members. Taken together, these data show that IL-32α stimulates Fas and ULBP2 expression via activation of p38 MAPK, which increases NK susceptibility of CML cells. Enhanced NK cell susceptibility of CML cells by IL-32α overexpression may improve the efficiency of NK cell-based immunotherapy.

TRAIL receptor signaling regulation of chemosensitivity in vivo but not in vitro

Background

Signaling by Tumor Necrosis Factor-Related Apoptosis Inducing Ligand (TRAIL) and Fas ligand (FasL) has been proposed to contribute to the chemosensitivity of tumor cells treated with various other anti-cancer agents. However, the importance of these effects and whether there are differences in vitro and in vivo is unclear.

Methodology/Principal Findings

To assess the relative contribution of death receptor pathways to this sensitivity and to determine whether these effects are intrinsic to the tumor cells, we compared the chemosensitivity of isogenic BJAB human lymphoma cells where Fas and TRAIL receptors or just TRAIL receptors were inhibited using mutants of the adaptor protein FADD or by altering the expression of the homeobox transcription factor Six1. Inhibition of TRAIL receptors did not affect in vitro tumor cell killing by various anti-cancer agents indicating that chemosensitivity is not significantly affected by the tumor cell-intrinsic activation of death receptor signaling. However, selective inhibition of TRAIL receptor signaling caused reduced tumor regression and clearance in vivo when tested in a NOD/SCID mouse model.

Conclusions

These data show that TRAIL receptor signaling in tumor cells can determine chemosensitivity in vivo but not in vitro and thus imply that TRAIL resistance makes tumors less susceptible to conventional cytotoxic anti-cancer drugs as well as drugs that directly target the TRAIL receptors.

Recombinant TFPI-2 enhances macrophage apoptosis through upregulation of Fas/FasL

Tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type serine proteinase inhibitor with inhibitory activity toward activated factor XI, plasma kallikrein, plasmin, certain matrix metalloproteinases, and the tissue factor-activated factor VII complex. In addition, TFPI-2 has other functions such as promoting cell migration and inducing apoptosis. In the present study, we investigated if TFPI-2 induced apoptosis in cultured U937-derived macrophages and the possible signal pathways that involved in the apoptotic process. Apoptotic DNA fragment detection and caspase-3,9 activity measurements indicated that rTFPI-2 promoted U937-derived macrophage apoptosis. Hoechst 33342 assay and flow cytometry further showed that rTFPI-2 induced apoptosis in cultured macrophages in a dose-dependent manner. Because death receptors of the TNF family such as Fas are the best-understood death pathways that recruit Fas-associated death domain (FADD) and procaspase-8 to the receptor in macrophages, we investigated the expression of Fas and its ligand (FasL) and downstream signal caspase-8 by Western blot analysis. The results indicated that the process of apoptosis triggered by rTFPI-2 was, at least in part, actively conducted by U937-derived macrophages possibly through Fas/FasL signal pathway. In brief, rTFPI-2 may have the potential usefulness in inducing macrophages apoptosis, which suggest TFPI-2 might have antiatherogenic effects.

Potent antitumoral activity of TRAIL through generation of tumor-targeted single-chain fusion proteins

In an attempt to improve TRAIL's (tumor necrosis factor-related apoptosis-inducing ligand) tumor selective activity a variant was designed, in which the three TRAIL protomers are expressed as a single polypeptide chain (scTRAIL). By genetic fusion with a single-chain antibody fragment (scFv) recognizing the extracellular domain of ErbB2, we further equipped scTRAIL with tumor-targeting properties. We studied tumor targeting and apoptosis induction of scFv–scTRAIL in comparison with non-targeted scTRAIL. Importantly, the tumor antigen-targeted scTRAIL fusion protein showed higher apoptotic activity in vitro, with a predominant action by TRAIL-R2 signaling. Pharmacokinetic studies revealed increased plasma half-life of the targeted scTRAIL fusion protein compared with scTRAIL. In vivo studies in a mouse tumor model with xenotransplanted Colo205 cells confirmed greater response to the ErbB2-specific scTRAIL fusion protein compared with non-targeted scTRAIL both under local and systemic application regimen. Together, in vitro and in vivo data give proof of concept of higher therapeutic activity of tumor-targeted scFv–scTRAIL molecules. Further, we envisage that through targeting of scTRAIL, potential side effects should be minimized. We propose that scFv-mediated tumor targeting of single-chain TRAIL represents a promising strategy to improve TRAIL's antitumoral action and to minimize potential unwanted actions on normal tissues.

Analysis of death receptor 5 and caspase-8 expression in primary and metastatic head and neck squamous cell carcinoma and their prognostic impact

Death receptor 5 (DR5) and caspase-8 are major components in the extrinsic apoptotic pathway. The alterations of the expression of these proteins during the metastasis of head and neck squamous cell carcinoma (HNSCC) and their prognostic impact have not been reported. The present study analyzes the expression of DR5 and caspase-8 by immunohistochemistry (IHC) in primary and metastatic HNSCCs and their impact on patient survival. Tumor samples in this study included 100 primary HNSCC with no evidence of metastasis, 100 primary HNSCC with lymph node metastasis (LNM) and 100 matching LNM. IHC analysis revealed a significant loss or downregulation of DR5 expression in primary tumors with metastasis and their matching LNM compared to primary tumors with no evidence of metastasis. A similar trend was observed in caspase-8 expression although it was not statistically significant. Downregulation of caspase-8 and DR5 expression was significantly correlated with poorly differentiated tumors compared to moderately and well differentiated tumors. Univariate analysis indicates that, in HNSCC with no metastasis, higher expression of caspase-8 significantly correlated with better disease-free survival and overall survival. However, in HNSCC with LNM, higher caspase-8 expression significantly correlated with poorer disease-free survival and overall survival. Similar results were also generated when we combined both DR5 and caspase-8. Taken together, we suggest that both DR5 and caspase-8 are involved in regulation of HNSCC metastasis. Our findings warrant further investigation on the dual role of caspase-8 in cancer development.

Cryptotanshinone sensitizes DU145 prostate cancer cells to Fas(APO1/CD95)-mediated apoptosis through Bcl-2 and MAPK regulation

Fas/APO-1/CD95, a member of the tumor necrosis factor (TNF) receptor superfamily, is a potential anti-cancer factor as it can induce apoptosis in tumor cells. However, despite the fact that many cancer cells express Fas on the membrane, some tumors such as prostate cancer display resistance to Fas-induced apoptosis. In these cases, combination therapy using chemotherapeutic agents and Fas may be more suitable than therapy using Fas alone. In the present study, we demonstrate that the apoptosis inhibitory protein, Bcl-2, was highly expressed in response to Fas in DU145 prostate cancer cells, thereby conferring resistance to apoptosis. We have screened a number of naturally occurring products that may overcome this resistance. Here we report that cryptotanshinone, the major tanshinone isolated from Salvia miltiorrhiza Bunge, can suppress Bcl-2 expression and augment Fas sensitivity in DU145 cells. We further show that JNK and p38 MAPK act upstream of Bcl-2 expression in Fas-treated DU145 cells, and that cryptotanshinone significantly blocked activation of these kinases. Moreover, cryptotanshinone sensitized several tumor cells to a broad range of anti-cancer agents. Collectively, our data suggest that cryptotanshinone has therapeutic potential in the treatment of human prostate cancer.

The role of FasL and Fas in health and disease

The FS7-associated cell surface antigen (Fas, also named CD95, APO-1 or TNFRSF6) attracted considerable interest in the field of apoptosis research since its discovery in 1989. The groups of Shin Yonehara and Peter Krammer were the first reporting extensive apoptotic cell death induction upon treating cells with Fas-specific monoclonal antibodies.1,2 Cloning of Fas3 and its ligand,4,5 FasL (also known as CD178, CD95L or TNFSF6), laid the cornerstone in establishing this receptor-ligand system as a central regulator of apoptosis in mammals. Therapeutic exploitation of FasL-Fas-mediated cytotoxicity was soon an ambitous goal and during the last decade numerous strategies have been developed for its realization. In this chapter, we will briefly introduce essential general aspects of the FasL-Fas system before reviewing its physiological and pathophysiological relevance. Finally, FasL-Fas-related therapeutic tools and concepts will be addressed.

Mutant PIK3CA licenses TRAIL and CD95L to induce non-apoptotic caspase-8-mediated ROCK activation

Constitutively active PI3K catalytic subunit alpha (PIK3CA) interfered with apoptosis induction downstream of death receptor-signaling complex formation allowing robust caspase-8 activation without triggering the execution steps of apoptosis. In mutant PIK3CA-expressing cells, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and CD95L stimulated nuclear factor kappaB (NFkappaB) activation, invasion, and transition to an amoeboid-like morphology. NFkappaB activation and adoption of amoeboid shape were inhibited by caspase-8 knockdown or FLIP-S expression, but only the cell morphology alterations required caspase-8 activity. Furthermore, we identified caspase-8-mediated, caspase-3-independent cleavage of the protein kinase rho-associated, coiled-coil containing protein kinase 1 as a novel mechanism for acquiring amoeboid shape and enhanced invasiveness in response to TRAIL and CD95L. Taken together, we provide evidence that mutated PIK3CA converts the 'tumor surveillance' activity of cancer cell-expressed death receptors and caspase-8 toward tumor promotion.

Genistein induces receptor and mitochondrial pathways and increases apoptosis during BCL-2 knockdown in human malignant neuroblastoma SK-N-DZ cells

The potent antiapoptotic molecule Bcl-2 is markedly up-regulated in a majority of cancers, including neuroblastoma. Genistein is an isoflavone with antitumor properties. The present study sought to elucidate the molecular mechanism of genistein-induced apoptosis and also to examine the effect of genistein in increasing apoptosis during Bcl-2 knockdown in human malignant neuroblastoma SK-N-DZ cells. The cells were transfected with Bcl-2 siRNA plasmid vector, treated with 10 microM genistein, or the combination, and subjected to TUNEL staining and FACS analysis. Semiquantitative and real-time RT-PCR experiments were performed for examining expression of Fas ligand (FasL), tumor necrosis factor-alpha (TNF-alpha), Fas-associated death domain (FADD), and TNFR-1-associated death domain (TRADD). The cell lysates were analyzed by Western blotting for levels of molecules involved in both receptor- and mitochondria-mediated apoptotic pathways. Treatment with the combination of Bcl-2 siRNA and genistein resulted in more than 80% inhibition of cell proliferation. TUNEL staining and FACS analysis demonstrated apoptosis in 70% of cells after treatment with the combination of both agents. Apoptosis was associated with increases in Bax:Bcl-2 ratio, mitochondrial release of cytochrome c, and activation of caspases through the mitochondria-mediated apoptotic pathway. Genistein triggered the receptor-mediated apoptotic pathway through upregulation of TNF-alpha, FasL, TRADD, and FADD and activation of caspase-8. Combination of Bcl-2 siRNA and genistein triggered a marked increase in cleavage of DFF45 and PARP that resulted in enhanced apoptosis. Our study demonstrates that Bcl-2 knockdown during genistein treatment effectively induced apoptosis in neuroblastoma cells. Therefore, this strategy could serve as a potential therapeutic regimen to inhibit the growth of human malignant neuroblastoma.

Testing the theory of immune selection in cancers that break the rules of transplantation

Modification of cancer cells likely to reduce their immunogenicity, including loss or down-regulation of MHC molecules, is now well documented and has become the main support for the concept of immune surveillance. The evidence that these modifications, in fact, result from selection by the immune system is less clear, since the possibility that they may result from reorganized metabolism associated with proliferation or from cell de-differentiation remains. Here, we (a) survey old and new transplantation experiments that test the possibility of selection and (b) survey how transmissible tumours of dogs and Tasmanian devils provide naturally evolved tests of immune surveillance.

Protein kinase Cbeta modulates ligand-induced cell surface death receptor accumulation: a mechanistic basis for enzastaurin-death ligand synergy

Although treatment with the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) is known to protect a subset of cells from induction of apoptosis by death ligands such as Fas ligand and tumor necrosis factor-alpha-related apoptosis-inducing ligand, the mechanism of this protection is unknown. This study demonstrated that protection in short term apoptosis assays and long term proliferation assays was maximal when Jurkat or HL-60 human leukemia cells were treated with 2-5 nm PMA. Immunoblotting demonstrated that multiple PKC isoforms, including PKCalpha, PKCbeta, PKCepsilon, and PKC, translocated from the cytosol to a membrane-bound fraction at these PMA concentrations. When the ability of short hairpin RNA (shRNA) constructs that specifically down-regulated each of these isoforms was examined, PKCbeta shRNA uniquely reversed PMA-induced protection against cell death. The PKCbeta-selective small molecule inhibitor enzastaurin had a similar effect. Although mass spectrometry suggested that Fas is phosphorylated on a number of serines and threonines, mutation of these sites individually or collectively had no effect on Fas-mediated death signaling or PMA protection. Further experiments demonstrated that PMA diminished ligand-induced cell surface accumulation of Fas and DR5, and PKCbeta shRNA or enzastaurin reversed this effect. Moreover, enzastaurin sensitized a variety of human tumor cell lines and clinical acute myelogenous leukemia isolates, which express abundant PKCbeta, to tumor necrosis factor-alpha related apoptosis-inducing ligand-induced death in the absence of PMA. Collectively, these results identify a specific PKC isoform that modulates death receptor-mediated cytotoxicity as well as a small molecule inhibitor that mitigates the inhibitory effects of PKC activation on ligand-induced death receptor trafficking and cell death.

A common hereditary single-nucleotide polymorphism in the gene of FAS and colorectal cancer survival

Apoptosis plays an important role in embryogenesis, autoimmunity and tumourigenesis. Cell surface death receptors such as TNFRSF6 (FAS) confer a major apoptotic effect. A single-nucleotide polymorphism in the FAS promoter gene, −670A/G, modulates apoptotic signalling and has been related to susceptibility and progression of a variety of cancers. The present study aimed to evaluate the role of this polymorphism for survival of patients with colorectal cancer. We performed a retrospective analysis including 433 patients with histologically confirmed colorectal cancer. A Cox regression model including FAS -670 genotypes, age at diagnosis, tumour grading, primary tumour size, number of lymph nodes examined, number of metastatic lymph nodes, tumour stage and application of fluorouracil-based adjuvant chemotherapy was used to estimate the effect of the FAS genotype on survival. FAS −670A/G genotype frequencies were 24.2% (AA), 46.3% (AG) and 29.5% (GG). Forty-nine patients were excluded from the Cox regression analysis because of missing values. Out of the remaining 384 patients, 69 (18%) died during a follow-up of maximum 10 years. Mean follow-up time was 58 ± 34 months (median 55 months). Carriers of the homozygous FAS -670GG genotype had a significantly lower survival rate compared with AA/AG genotype carriers (relative risk 1.76, 95% confidence interval 1.08–2.87; P= 0.023). The FAS −670A/G polymorphism may be associated with overall survival time of patients with colorectal cancer.

Death ligands designed to kill: development and application of targeted cancer therapeutics based on proapoptotic TNF family ligands

The identification of molecular markers associated with cancer development or progression, opened a new era in the development of therapeutics. The successful introduction of a few low molecular weight chemicals and recombinant protein therapeutics with targeted actions into clinical practice have raised great expectations to broadly improve cancer therapy with respect to both overall clinical responses and tolerability. Targeting the apoptotic machinery of malignant cells is an attractive concept to combat cancer, which is currently exploited for the proapoptotic members of the TNF ligand family at various stages of preclinical and clinical development. This review summarizes recent progress in this rapidly progressing field of "biologic" therapies targeting the death receptors of TNF, CD95L, and TRAIL by means of its cognate protein ligands, receptor specific antibodies, and gene therapeutic approaches. Preclinical data on newly derived variants and fusion proteins based on these death ligands, designed to act in a tumor restricted manner, thereby preventing a systemic, potentially harmful action, will also be discussed.

Tumorigenicity of IL-1alpha- and IL-1beta-deficient fibrosarcoma cells

Analyzing the growth of fibrosarcoma lines derived from IL-1alpha-, IL-1beta- , or IL-1alphabeta-knockout (-/-) mice in the immunocompetent host revealed that tumor-derived IL-1alpha and IL-1beta exert strong and opposing effects on immune response induction, which prohibited the evaluation of a potential impact on tumorigenicity. Therefore, in vivo growth of IL-1-deficient tumor lines was evaluated in nu/nu mice and was compared with in vitro growth characteristics. All IL-1-deficient fibrosarcoma lines grow in immunocompromised mice. However, IL-1alpha(-/-)beta-competent (comp) lines grow more aggressively, efficiently induce angiogenesis, and recruit inflammatory cells. Despite stronger tumorigenicity of IL-1beta(comp) lines, IL-1alpha strengthens anchorage-independent growth, but both IL-1alpha and IL-1beta support drug resistance. Corresponding to the aggressive growth, IL-1beta(comp) cells display increased matrix adhesion, motility, and cable formation on matrigel, likely supported by elevated alpha(v)/beta3 and matrix metalloroteinase expression. Recruitment of myeloid cells requires IL-1beta but is regulated by IL-1alpha, because inflammatory chemokine and cytokine expression is stronger in IL-1alpha(-/-)beta(comp) than in IL-1(wt) lines. This regulatory effect of tumor-derived IL-1alpha is restricted to the tumor environment and does not affect systemic inflammatory response induction by tumor-derived IL-1beta. Both sarcoma cell-derived IL-1alpha and IL-1beta promote tumor growth. However, IL-1alpha exerts regulatory activity on the tumor cell-matrix cross-talk, and only IL-1beta initiates systemic inflammation.

Activity of the Bcl-2 family inhibitor ABT-263 in a panel of small cell lung cancer xenograft models

PURPOSE

The purpose of this study was to characterize the activity of the Bcl-2 protein family inhibitor ABT-263 in a panel of small cell lung cancer (SCLC) xenograft models.

EXPERIMENTAL DESIGN

A panel of 11 SCLC xenograft models was established to evaluate the efficacy of ABT-263. Single agent activity was examined on a continuous dosing schedule in each of these models. The H146 model was used to further evaluate dose and schedule, comparison to standard cytotoxic agents, and induction of apoptosis.

RESULTS

ABT-263 exhibited a range of antitumor activity, leading to complete tumor regression in several models. Significant regressions of tumors as large as 1 cc were also observed. The efficacy of ABT-263 was also quite durable; in several cases, minimal tumor regrowth was noted several weeks after the cessation of treatment. Antitumor effects were equal or superior to that of several clinically approved cytotoxic agents. Regression of large established tumors was observed through several cycles of therapy and efficacy was retained in a Pgp-1 overexpressing line. Significant efficacy was observed on several dose and therapeutic schedules and was associated with significant induction of apoptosis.

CONCLUSIONS

ABT-263 is a potent, orally bioavailable inhibitor of Bcl-2 family proteins that has recently entered clinical trials. The efficacy data reported here suggest that SCLC is a promising area of clinical investigation with this agent.

Apoptotic pathways in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common causes of cancer related death. Despite the advances in understanding of the molecular pathogenesis, pancreatic cancer remains a major unsolved health problem. Overall, the 5-year survival rate is less than 5% demonstrating the insufficiency of current therapies. Most cytotoxic therapies induce apoptosis and PDAC cells have evolved a plethora of molecular mechanisms to assure survival. We will present anti-apoptotic strategies working at the level of the death receptors, the mitochondria or involving the caspase inhibitors of the IAP family. Furthermore, the survival function of the phosphotidylinositol-3' kinase (PI3K)/AKT- and NF-kappaB-pathways are illustrated. A detailed molecular knowledge of the anti-apoptotic mechanisms of PDAC cells will help to improve therapies for this dismal disease and therapeutic strategies targeting the programmed cell death machinery are in early preclinical and clinical development.

Regulation of CD95/APO-1/Fas-induced apoptosis by protein phosphatases

Triggering the CD95/APO-1/Fas receptor by CD95-L induces the assembly of the death-inducing signaling complex (DISC), which permits initiator caspases activation and progression of a signaling cascade that culminates in cellular apoptosis. Despite the CD95 receptor does not exhibit any kinase activity by itself, phosphorylation/dephosphorylation events seem important to regulate many aspects of CD95-mediated apoptosis. Here, we try to highlight particularly the importance of protein phosphatases in the modulation of the CD95 system.

Down-regulation of mcl-1 by small interfering RNA sensitizes resistant melanoma cells to fas-mediated apoptosis

Resistance of malignant melanoma cells to Fas-mediated apoptosis is among the mechanisms by which they escape immune surveillance. However, the mechanisms contributing to their resistance are not completely understood, and it is still unclear whether antiapoptotic Bcl-2-related family proteins play a role in this resistance. In this study, we report that treatment of Fas-resistant melanoma cell lines with cycloheximide, a general inhibitor of de novo protein synthesis, sensitizes them to anti-Fas monoclonal antibody (mAb)-induced apoptosis. The cycloheximide-induced sensitization to Fas-induced apoptosis is associated with a rapid down-regulation of Mcl-1 protein levels, but not that of Bcl-2 or Bcl-xL. Targeting Mcl-1 in these melanoma cell lines with specific small interfering RNA was sufficient to sensitize them to both anti-Fas mAb-induced apoptosis and activation of caspase-9. Furthermore, ectopic expression of Mcl-1 in a Fas-sensitive melanoma cell line rescues the cells from Fas-mediated apoptosis. Our results further show that the expression of Mcl-1 in melanoma cells is regulated by the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) and not by phosphatidylinositol 3-kinase/AKT signaling pathway. Inhibition of ERK signaling with the mitogen-activated protein/ERK kinase-1 inhibitor or by expressing a dominant negative form of mitogen-activated protein/ERK kinase-1 also sensitizes resistant melanoma cells to anti-Fas mAb-induced apoptosis. Thus, our study identifies mitogen-activated protein kinase/ERK/Mcl-1 as an important survival signaling pathway in the resistance of melanoma cells to Fas-mediated apoptosis and suggests that its targeting may contribute to the elimination of melanoma tumors by the immune system.

Peroxisome proliferator-activated receptor gamma activates fas ligand gene promoter inducing apoptosis in human breast cancer cells

In just over a decade, apart from established metabolic actions, peroxisome proliferator-activated receptor gamma (PPARgamma) has evolved as key therapeutic target in cancer disease. Fas ligand (FasL), a trans-membrane protein, induces apoptosis by crosslinking with the Fas receptor. Despite the FasL relevance, little is available on the regulation of its expression. In the current study, we explored for the first time the potential role of PPARgamma in triggering apoptotic events through the Fas/FasL pathway in breast cancer cells. In MCF7 cells, by reverse transcription-polymerase chain reaction and Western blotting, we showed that the synthetic PPARgamma ligand rosiglitazone (BRL) enhanced FasL expression, that was abrogated by a specific PPARgamma antagonist GW9662. Transient transfection assays demonstrated that BRL transactivated human FasL promoter gene in a PPARgamma-dependent manner. Progressive 5' deletion analysis has identified a minimal promoter fragment spanning nucleotides from -318 to -237 bp, which is still sensitive to BRL treatment. FasL promoter activity was abrogated by mithramycin, suggesting an involvement of Sp1 transcription factor in PPARgamma action. Electrophoretic mobility shift and chromatin immuno-precipitation assays demonstrated that BRL increased the binding of PPARgamma and Sp1 to the Sp1 sequence located within the FasL gene promoter. The role of PPARgamma and Fas/FasL pathways in BRL-induced apoptotic events was assessed by caspase 8 cleavage in the presence of GW as well as PPARgamma and FasL RNA interferences. Our results indicate that PPARgamma positively regulates the FasL gene expression also in MDA-MB231 and in BT20, revealing a new molecular mechanism by which BRL induces apoptosis in breast cancer cells.

Resveratrol sensitizes melanomas to TRAIL through modulation of antiapoptotic gene expression

Although many human melanomas express the death receptors TRAIL-R2/DR5 or TRAIL-R1/DR4 on cell surface, they often exhibit resistance to exogenous TRAIL. One of the main contributors to TRAIL-resistance of melanoma cells is upregulation of transcription factors STAT3 and NF-kappaB that control the expression of antiapoptotic genes, including cFLIP and Bcl-xL. On the other hand, the JNK-cJun pathway is involved in the negative regulation of cFLIP (a caspase-8 inhibitor) expression. Our observations indicated that resveratrol, a polyphenolic phytoalexin, decreased STAT3 and NF-kappaB activation, while activating JNK-cJun that finally suppressed expression of cFLIP and Bcl-xL proteins and increased sensitivity to exogenous TRAIL in DR5-positive melanomas. Interestingly, resveratrol did not increase surface expression of DR5 in human melanomas, while gamma-irradiation or sodium arsenite treatment substantially upregulated DR5 expression. Hence, an initial increase in DR5 surface expression (either by gamma-irradiation or arsenite), and subsequent downregulation of antiapoptotic cFLIP and Bcl-xL (by resveratrol), appear to constitute an efficient approach to reactivate apoptotic death pathways in TRAIL-resistant human melanomas. In spite of partial suppression of mitochondrial function and the mitochondrial death pathway, melanoma cells still retain the potential to undergo the DR5-mediated, caspase-8-dependent death pathway that could be accelerated by either an increase in DR5 surface expression or suppression of cFLIP. Taken together, these results suggest that resveratrol, in combination with TRAIL, may have a significant efficacy in the treatment of human melanomas.

Transcriptional activation of caspase-6 and -7 genes by cisplatin-induced p53 and its functional significance in cisplatin nephrotoxicity

This study examined the role of cisplatin-induced p53 activation in regulation of caspases and cellular injury during cisplatin nephrotoxicity. The executioner caspase-6 and -7 but not caspase-3 were identified as transcriptional targets of p53 in cisplatin injury as revealed by chromatin immunoprecipitation, a reporter gene and electrophoretic mobility shift assays, and real-time PCR following overexpression and inhibition of p53. DNA binding by p53 involved the first introns of the human and mouse caspase-7 gene and the mouse caspase-6 gene. Studies in human kidney, breast, ovary, colon, and prostate tumor cell lines also validated these findings. Treatment of p53 (-/-) cells with cisplatin did not induce caspase-6 and -7 expression and subsequent activation. In caspase-3 (-/-) cells, inhibition of caspase-6 and -7 activations markedly prevented cisplatin-induced cell death. In an in vivo model of cisplatin nephrotoxicity inhibition of p53 activation by a p53 inhibitor suppressed transactivation of the caspase-6 and -7 genes and prevented renal failure. p53 (-/-) mice were resistant to cisplatin nephrotoxicity as assessed by renal function and histology. These studies provide first evidence for p53-dependent transcriptional control of the caspase-6 and -7 genes and its functional significance in cisplatin injury to renal cells and functional implication of cisplatin-induced p53 induction in vitro and in vivo in cisplatin nephrotoxicity.

Soluble Fas ligand inhibits angiogenesis in rheumatoid arthritis

The characteristics of rheumatoid arthritis (RA) pathology include the infiltration of inflammatory leukocytes, the proliferation of synovial cells, and the presence of extensive angiogenesis, referred to as rheumatoid pannus. Fas ligand is critical to the homeostatic regulation of the immune response, but its role in the angiogenic process of RA remains to be defined. In this study, we investigated whether soluble Fas ligand (sFasL) induces synoviocyte apoptosis and regulates angiogenesis of endothelial cells in RA. The levels of sFasL were elevated in the synovial fluids of RA patients when compared to those of osteoarthritis (OA) patients, and they correlated inversely with vascular endothelial growth factor₁₆₅ (VEGF₁₆₅) concentrations. sFasL, ranging from 10 to 100 ng/ml, induced the apoptosis of RA fibroblast-like synoviocytes (FLS) in vitro, and thereby decreased VEGF₁₆₅ production. In addition, sFasL inhibited VEGF₁₆₅-induced migration and chemotaxis of endothelial cells to basal levels in a manner independent of the Fas-mediated cell death. sFasL dose-dependently suppressed the VEGF₁₆₅-stimulated increase in pAkt expression in endothelial cells, which might be associated with its anti-migratory effect on endothelial cells. Moreover, sFasL strongly inhibited neovascularization in the Matrigel plug in vivo. Our data suggest that sFasL shows anti-angiogenic activity within RA joints not only by inducing apoptosis of VEGF₁₆₅-producing cells but also by blocking VEGF₁₆₅-induced migration of endothelial cells, independent of Fas-mediated apoptosis.

The immunology of hepatitis B

The hepatitis B virus (HBV) is an enveloped, hepatotrophic, oncogenic hepadnavirus that is noncytopathic for hepatocytes. HBV infection results in a variety of outcomes that are determined by the quality, quantity, and kinetics of the host innate and adaptive immune responses. Whether HBV infection is cleared or persists as a progressive or nonprogressive liver disease is determined by both viral and host factors. Replicative intermediates can persist in the liver under immunologic control after resolution of acute or chronic hepatitis B, conferring a risk for reactivation following a course of immunosuppression or chemotherapy.