Expression of Fas and Fas-related molecules in human hepatocellular carcinoma

Burning down the house: Pyroptosis in the tumor microenvironment of hepatocellular carcinoma

A high mortality rate makes hepatocellular carcinoma (HCC) a difficult cancer to treat. When surgery is not possible, liver cancer patients are treated with chemotherapy. However, HCC management and treatment are difficult. Sorafenib, which is a first-line treatment for hepatocellular carcinoma, initially slows disease progression. However, sorafenib resistance limits patient survival. Recent studies have linked HCC to programmed cell death, which has increased researcher interest in therapies targeting cell death. Pyroptosis, which is an inflammatory mode of programmed cell death, may be targeted to treat HCC. Pyroptosis pathways, executors, and effects are examined in this paper. This review summarizes how pyroptosis affects the tumor microenvironment (TME) in HCC, including the role of cytokines such as IL-1β and IL-18 in regulating immune responses. The use of chemotherapies and their ability to induce cancer cell pyroptosis as alternative treatments and combining them with other drugs to reduce side effects is also discussed. In conclusion, we highlight the potential of inducing pyroptosis to treat HCC and suggest ways to improve patient outcomes. Studies on cancer cell pyroptosis may lead to new HCC treatments.

Possible mechanisms associated with immune escape and apoptosis on anti-hepatocellular carcinoma effect of Mu Ji Fang granules

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common digestive system cancers with high mortality rates worldwide. The main ingredients in Mu Ji Fang Granules (MJF) are alkaloids, flavonoids, and polysaccharides. MJF has been used in the clinical treatment of hepatitis, cirrhosis and HCC for more than 30 years. Few previous studies have focused on the mechanism of MJF on tumor immu-nology in the treatment of HCC.

AIM

To explore the mechanism of action of MJF on tumor immunology in the treatment of HCC.

METHODS

The absorbable ingredients of MJF were identified using Molecule Network related to High Performance Liquid Chromatography-Electron Spray Ionization-Time of Flight- Mass Spectrometry, and hub potential anti-HCC targets were screened using network pharmacology and pathway enrichment analysis. Forty male mice were randomly divided into the Blank, Model, and MJF groups (1.8, 5.4, and 10.8 g/kg/d) following 7 d of oral administration. Average body weight gain, spleen and thymus indices were calculated, tumor tissues were stained with hematoxylin and eosin, and Interferon gamma (IFN-γ), Tumor necrosis factor α (TNF-α), Interleukin-2, aspartate aminotransferase, alanine aminotransferase, alpha-fetoprotein (AFP), Fas, and FasL were measured by Enzyme-linked Immunosorbent Assay. Relevant mRNA expression of Bax and Bcl2 was evaluated by Real Time Quantitative PCR (RT-qPCR) and protein expression of Transforming growth factor β1 (TGF-β1) and Mothers against decapentaplegic homolog (SMAD) 4 was assessed by Western blotting. The HepG2 cell line was treated with 10 mg/mL, 20 mg/mL, 30 mg/mL, 40 mg/mL of MJF, and another 3 groups were treated with TGF-β1 inhibitor (LY364947) and different doses of MJF. Relevant mRNA expression of TNF-α, IFN-γ, Bax and Bcl2 was evaluated by RT-qPCR and protein expression of TGF-β1, SMAD2, p-SMAD2, SMAD4, and SMAD7 was assessed by Western blotting.

RESULTS

It was shown that MJF improved body weight gain and tumor inhibition rate in H22 tumor-bearing mice, protected immune organs and liver function, reduced the HCC indicator AFP, affected immunity and apoptosis, and up-regulated the TGF-β1/SMAD signaling pathway, by increasing the relative expression of TGF-β1, SMAD2, p-SMAD2 and SMAD4 and decreasing SMAD7, reducing immune factors TNF-α and IFN-γ, decreasing apoptosis cytokines Fas, FasL and Bcl2/Bax, and inhibiting the effect of LY364947 in HepG2 cells.

CONCLUSION

MJF inhibits HCC by activating the TGF-β1/SMAD signaling pathway, and affecting immune and apoptotic cytokines, which may be due to MJF adjusting immune escape and apoptosis.

Serum Soluble Fas Levels and Incidence of Liver Cancer in Nested Case-Control Study

BACKGROUND

Soluble Fas (sFas) plays various roles in carcinogenesis and tumor dissemination by preventing apoptosis via binding to Fas ligand. We analyzed associations of serum sFas levels with the incidence of liver cancer in a prospective case-control study nested in the Japan Collaborative Cohort Study.

METHODS

A baseline survey was conducted from 1988, with blood samples obtained from 39,242 subjects. Patients diagnosed with liver cancer were regarded as cases. Two or three controls were selected and matched for sex, age, and geographic area. Conditional logistic regression was used to estimate ORs for cancer incidence associated with sFas.

RESULTS

This study contained 86 cases and 249 controls. After controlling for alcohol intake, body mass index, smoking, and hepatitis viral infection, participants with high sFas showed elevated risk of cancer (Ptrend = 0.003) and the third tertile of sFas showed a higher risk compared with the first tertile [OR, 3.53; 95% confidence interval (CI), 1.28-9.69]. In hepatocellular carcinoma, high sFas was associated with elevated risk (Ptrend < 0.001). In men and the elderly, subjects in the highest tertiles showed higher cancer risk. Limiting subjects to those followed for 3 years, high sFas was related to liver cancer risk (Ptrend = 0.033) and the third tertile showed a higher risk compared with the first (OR, 2.94; 95% CI, 0.94-9.14).

CONCLUSIONS

High serum sFas may be related to future risk of liver cancer.

IMPACT

Our findings highlight this biomarker for further analysis in pooled investigations with different/larger prospective cohorts.

RNA Therapeutic Options to Manage Aberrant Signaling Pathways in Hepatocellular Carcinoma: Dream or Reality?

Despite the early promise of RNA therapeutics as a magic bullet to modulate aberrant signaling in cancer, this field remains a work-in-progress. Nevertheless, RNA therapeutics is now a reality for the treatment of viral diseases (COVID-19) and offers great promise for cancer. This review paper specifically investigates RNAi as a therapeutic option for HCC and discusses a range of RNAi technology including anti-sense oligonucleotides (ASOs), Aptamers, small interfering RNA (siRNA), ribozymes, riboswitches and CRISPR/Cas9 technology. The use of these RNAi based interventions is specifically outlined in three primary strategies, namely, repressing angiogenesis, the suppression of cell proliferation and the promotion of apoptosis. We also discuss some of the inherent chemical and delivery problems, as well as targeting issues and immunogenic reaction to RNAi interventions.

Fas -670 A/G polymorphism predicts prognosis of hepatocellular carcinoma after curative resection in Chinese Han population

BACKGROUND

Apoptosis, also called programmed cell death, is a genetically controlled process against hyperproliferation and malignancy. The Fas-Fas ligand (FasL) system is considered a major pathway for apoptosis in cells and tissues. Thus, this study aimed to investigate whether single nucleotide polymorphisms (SNPs) in Fas and FasL gene may have effects on the recurrence and survival of patients with hepatocellular carcinoma (HCC) after curative hepatectomy.

METHODS

We investigated the relationship between Fas rs1800682, rs2234767 and FasL rs763110 polymorphisms and recurrence-free survival (RFS) as well as overall survival (OS) in 117 Chinese Han patients with HCC who underwent hepatectomy.

RESULTS

In Kaplan-Meier survival analysis, only Fas rs1800682 (-670 A/G) was associated with RFS and OS. Compared with AA genotype, the AG/GG genotype was significantly associated with better RFS (P = 0.008) and OS (P = 0.020). Moreover, multivariate Cox regression analysis showed that Fas rs1800682 remained as a significant independent predictor of RFS for HCC patients with hepatectomy [AG/GG vs. AA: adjusted hazard ratio = 0.464, 95% confidence interval: 0.275-0.782, P = 0.004], but was not an independent predictor of OS (P = 0.395).

CONCLUSIONS

This study demonstrated that Fas -670 G allele may play a protective role in the recurrence and survival of HCC patients with hepatectomy. Furthermore, Fas rs1800682 polymorphism might be a promising biomarker for HCC patients after hepatectomy.

Soluble CD95L in cancers and chronic inflammatory disorders, a new therapeutic target?

Although CD95L (also known as FasL) is still predominantly considered as a death ligand that induces apoptosis in infected and transformed cells, substantial evidence indicate that it can also trigger non-apoptotic signaling pathways whose pathophysiological roles remain to be fully elucidated. The transmembrane ligand CD95L belongs to the tumor necrosis factor (TNF) superfamily. After cleavage by metalloprotease, its soluble form (s-CD95L) fails to trigger the apoptotic program but instead induces signaling pathways promoting the aggressiveness of certain inflammatory disorders such as autoimmune diseases and cancers. We propose to evaluate the various pathologies in which the metalloprotease-cleaved CD95L is accumulated and analyze whether this soluble ligand may play a significant role in the pathology progression. Based on the TNFα-targeting therapeutics, we envision that targeting the soluble form of CD95L may represent a very attractive therapeutic option in the pathologies depicted herein.

Activated platelets contribute to the progression of hepatocellular carcinoma by altering the tumor environment

AIM

Hepatocellular carcinoma (HCC) is a primary liver cancer that usually develops in a background of chronic liver disease and prolonged inflammation. A major contributor in the complex molecular pathogenesis of HCC is the highly intertwined cross-talk between the tumor and the surrounding stromal cells, such as hepatic stellate cells, endothelial cells, macrophages and other immune cells. These tumor-stroma interactions actively fuel tumor growth and modulate the hepatic microenvironment to benefit tumor invasion and disease progression. Platelets have been reported to interact with different cell types in the tumor microenvironment, including tumor cells, stellate cells and macrophages.

MATERIALS AND METHODS

Mice were treated with hepatocarcinogenic compound diethylnitrosamine for 25 weeks to induce HCC in the background of fibrosis and inflammation. From week 10, anti-platelet drug Clopidogrel was added to the drinking water and mice were given ad libitum access.

KEY FINDINGS

In this study, we show that activated platelets promote tumor cell proliferation and contribute to the adverse tumor-stroma cross-talk that fuels tumor progression. We also show that inhibiting platelet activation with the P2Y12-inhibitor Clopidogrel decreases the number of tumors in a chemically induced mouse model for HCC.

SIGNIFICANCE

These results suggest an important role for platelets in the pathogenesis of HCC and that the use of anti-platelet drugs may be therapeutically relevant for patients with liver cancer.

Dynamics of m6A RNA Methylome on the Hallmarks of Hepatocellular Carcinoma

Epidemiological data consistently rank hepatocellular carcinoma (HCC) as one of the leading causes of cancer-related deaths worldwide, often posing severe economic burden on health care. While the molecular etiopathogenesis associated with genetic and epigenetic modifications has been extensively explored, the biological influence of the emerging field of epitranscriptomics and its associated aberrant RNA modifications on tumorigenesis is a largely unexplored territory with immense potential for discovering new therapeutic approaches. In particular, the underlying cellular mechanisms of different hallmarks of hepatocarcinogenesis that are governed by the complex dynamics of m6A RNA methylation demand further investigation. In this review, we reveal the up-to-date knowledge on the mechanistic and functional link between m6A RNA methylation and pathogenesis of HCC.

Pogostemon cablin Triggered ROS-Induced DNA Damage to Arrest Cell Cycle Progression and Induce Apoptosis on Human Hepatocellular Carcinoma In Vitro and In Vivo

The purpose of the study was to elucidate the anti-hepatoma effects and mechanisms of Pogostemon cablin essential oils (PPa extract) in vitro and in vivo. PPa extract exhibited an inhibitory effect on hepatocellular carcinoma (HCC) cells and was less cytotoxic to normal cells, especially normal liver cells, than it was to HCC cells, exerting a good selective index. Additionally, PPa extract inhibited HCC cell growth by blocking the cell cycle at the G₀/G₁ phase via p53 dependent or independent pathway to down regulated cell cycle regulators. Moreover, PPa extract induced the FAS-FASL-caspase-8 system to activate the extrinsic apoptosis pathway, and it increased the bax/bcl-2 ratio and reduced ΔΨm to activate the intrinsic apoptosis pathway that might be due to lots of reactive oxygen species (ROS) production which was induced by PPa extract. In addition, PPa extract presented to the potential to act synergistically with sorafenib to effectively inhibit HCC cell proliferation through the Akt/mTOR pathway and reduce regrowth of HCC cells. In an animal model, PPa extract suppressed HCC tumor growth and prolonged lifespan by reducing the VEGF/VEGFR axis and inducing tumor cell apoptosis in vivo. Ultimately, PPa extract demonstrated nearly no or low system-wide, physiological, or pathological toxicity in vivo. In conclusion, PPa extract effectively inhibited HCC cell growth through inducing cell cycle arrest and activating apoptosis in vitro and in vivo. Furthermore, PPa extract exhibits less toxicity toward normal cells and organs than it does toward HCC cells, which might lead to fewer side effects in clinical applications. PPa extract may be developed into a clinical drug to suppress tumor growth or functional food to prevent HCC initiation or chemoprotection of HCC recurrence.

The multi-faceted functioning portrait of LRF/ZBTB7A

Transcription factors (TFs) consisting of zinc fingers combined with BTB (for broad-complex, tram-track, and bric-a-brac) domain (ZBTB) are a highly conserved protein family that comprises a multifunctional and heterogeneous group of TFs, mainly modulating cell developmental events and cell fate. LRF/ZBTB7A, in particular, is reported to be implicated in a wide variety of physiological and cancer-related cell events. These physiological processes include regulation of erythrocyte maturation, B/T cell differentiation, adipogenesis, and thymic insulin expression affecting consequently insulin self-tolerance. In cancer, LRF/ZBTB7A has been reported to act either as oncogenic or as oncosuppressive factor by affecting specific cell processes (proliferation, apoptosis, invasion, migration, metastasis, etc) in opposed ways, depending on cancer type and molecular interactions. The molecular mechanisms via which LRF/ZBTB7A is known to exert either physiological or cancer-related cellular effects include chromatin organization and remodeling, regulation of the Notch signaling axis, cellular response to DNA damage stimulus, epigenetic-dependent regulation of transcription, regulation of the expression and activity of NF-κB and p53, and regulation of aerobic glycolysis and oxidative phosphorylation (Warburg effect). It is a pleiotropic TF, and thus, alterations to its expression status become detrimental for cell survival. This review summarizes its implication in different cellular activities and the commonly invoked molecular mechanisms triggered by LRF/ZBTB7A’s orchestrated action.

Fas and FasL promoter polymorphisms and susceptibility to HBV infection: A systematic review and meta-analysis

Apoptosis is a universal cellular defense mechanism against senescent, damaged, genetically mutated, or virally-infected cells. It also is critical for the maintenance of liver health. Fas and FasL system act as a major death pathway that triggers apoptosis cascade in the liver. In this systematic review and meta-analysis, we aimed to investigate the relationship between four major polymorphisms of Fas and FasL genes with susceptibility to or clearance of HBV infection. All the eligible studies were extracted from PubMed and Scopus with no date and language restriction. ORs with 95% CIs were used to evaluate the strength of the association based on the following genetic models: (1) the allelic, (2) the homozygote, (3) the dominant, and (4) the recessive models. Totally 7 related articles were included in this meta-analysis; 5 studies of 7 related articles investigated FasL -844C/T (rs763110) polymorphism, 4 studies investigated FasL IVS2nt-124, 6 studies investigated Fas -670 A/G (rs1800682), and 4 studies investigated Fas -1377 A/G (rs2234767) polymorphism. This meta-analysis showed that there is no statistically significant association between the risk or clearance of HBV infection and four studied Fas and FasL polymorphisms in their allelic comparison or genetic models. Fas -670, Fas -1377, FasL -124, and FasL -844 polymorphisms did not show any significant association with the clearance or risk of HBV infection. Therefore, it seems that susceptibility to HBV infection or clearance of it is not affected by Fas and FasL genetic polymorphisms. But, to reach a definitive conclusion, further studies with a larger sample size of different ethnicity are still needed.

Protein tyrosine phosphatase L1 inhibits high-grade serous ovarian carcinoma progression by targeting IκBα

Background

High-grade serous ovarian cancer (HGSOC) represents most of the ovarian cancers and accounts for 70%-80 % of related deaths. The overall survival of HGSOC has not been remarkably improved in the past decades, due to the tumor dissemination in peritoneal cavity and invasion of adjacent organs. Therefore, identifying molecular biomarkers is invaluable in helping predicting clinical outcomes and developing targeted chemotherapies. Although there have been studies revealing the prognostic significance of protein tyrosine phosphatase L1 (PTPL1) in breast cancer and lung cancer, its involvement and functions in HGSOC remains to be elucidated.

Methods

We retrospectively enrolled a cohort of HGSOC patients after surgical resection. And analyzed the mRNA and protein levels of PTPL1 in tissue samples.

Results

We found that PTPL1 presented a lower expression in HGSOC tissues than in adjacent normal ovarian tissues. Besides, the PTPL1 level was negatively correlated with tumor stage, implying its potential role as a tumor suppressor. Univariate and multivariate analyses identified that patients with higher PTPL1 showed a better overall survival compared to those with lower PTPL1 expression. In addition, cellular experiments confirmed the role of PTPL1 in suppressing tumor proliferation and invasion. Furthermore, we demonstrated that PTPL1 negatively regulated phosphorylation of tyrosine 42 on IκBα (IκBα-pY42). To our knowledge, this is the initial finding on PTPL1 targeting IκBα-pY42 site. Finally, our data indicated that PTPL1 suppressed tumor progression by dephosphorylating IκBα-pY42, which stabilized IκBα and attenuated nucleus translocation of NF-κB.

Conclusion

Our study revealed a tumor-suppressing role of PTPL1 in HGSOC by targeting IκBα.

Apoptotic Mechanisms of Peroxisome Proliferator-Activated Receptor-γ Activation in Acinar Cells During Acute Pancreatitis

OBJECTIVE

The objective of this study was to determine the mechanism by which activation of peroxisome proliferator-activated receptor-γ promotes apoptosis of acinar cells in pancreatitis.

METHODS

AR42j cells pretreated with the peroxisome proliferator-activated receptor-γ agonist pioglitazone were activated by cerulein as an in vitro model of acute pancreatitis. Inflammatory cytokines and amylase were detected by enzyme-linked immunosorbent assay. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis was measured by flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. Activity of caspases was determined. Bax and Bcl-2 levels were assayed by Western blot.

RESULTS

Cytokines, amylase, and cellular proliferation decreased in pioglitazone-pretreated cells. Pioglitazone increased the activity of caspases 3, 8, and 9 in cerulein-activated AR42j cells as well as in the pancreas of rats 3 hours after induction of severe acute pancreatitis. Acinar cell apoptosis was induced by reducing the mitochondrial membrane potential in the pioglitazone group. Pioglitazone increased expression of proapoptotic Bax proteins and decreased antiapoptotic Bcl-2 in cerulein-induced AR42j cells and decreased Bcl-2 levels in pancreatic tissue of severe acute pancreatitis rats 1 and 3 hours after induction.

CONCLUSION

Pioglitazone may promote apoptosis of acinar cells through both intrinsic and extrinsic apoptotic pathways in acute pancreatitis.

Apoptosis in liver carcinogenesis and chemotherapy

Hepatocellular carcinoma (HCC) is a major health problem. In human hepatocarcinogenesis, the balance between cell death and proliferation is deregulated, tipping the scales for a situation where antiapoptotic signals are overpowering the death-triggering stimuli. HCC cells harbor a wide variety of mutations that alter the regulation of apoptosis and hence the response to chemotherapeutical drugs, making them resistant to the proapoptotic signals. Considering all these modifications found in HCC cells, therapeutic approaches need to be carefully studied in order to specifically target the antiapoptotic signals. This review deals with the recent relevant contributions reporting molecular alterations for HCC that lead to a deregulation of apoptosis, as well as the challenge of death-inducing chemotherapeutics in current HCC treatment.

Antitumoral gene-based strategy involving nitric oxide synthase type III overexpression in hepatocellular carcinoma

Hepatocellular carcinoma develops in cirrhotic liver. The nitric oxide (NO) synthase type III (NOS-3) overexpression induces cell death in hepatoblastoma cells. The study developed gene therapy designed to specifically overexpress NOS-3 in cultured hepatoma cells, and in tumors derived from orthotopically implanted tumor cells in fibrotic livers. Liver fibrosis was induced by CCl4 administration in mice. The first-generation adenoviruses were designed to overexpress NOS-3 or green fluorescent protein, and luciferase complementary DNA under the regulation of murine alpha-fetoprotein (AFP) and Rous Sarcoma Virus (RSV) promoters, respectively. Both adenovirus and Hepa 1-6 cells were used for in vitro and in vivo experiments. Adenoviruses were administered through the tail vein 2 weeks after orthotopic tumor cell implantation. AFP-NOS-3/RSV-luciferase increased oxidative-related DNA damage, p53, CD95/CD95L expression and caspase-8, -9 and -3 activities in cultured Hepa 1-6 cells. The increased expression of CD95/CD95L and caspase-8 activity was abolished by Nω-nitro-l-arginine methyl ester hydrochloride, p53 and CD95 small interfering RNA. AFP-NOS-3/RSV-luciferase adenovirus increased cell death markers, and reduced cell proliferation of established tumors in fibrotic livers. The increase of oxidative/nitrosative stress induced by NOS-3 overexpression induced DNA damage, p53, CD95/CD95L expression and cell death in hepatocellular carcinoma cells. The effectiveness of the gene therapy has been demonstrated in vitro and in vivo.

Regulation of cell death receptor S-nitrosylation and apoptotic signaling by Sorafenib in hepatoblastoma cells

Nitric oxide (NO) plays a relevant role during cell death regulation in tumor cells. The overexpression of nitric oxide synthase type III (NOS-3) induces oxidative and nitrosative stress, p53 and cell death receptor expression and apoptosis in hepatoblastoma cells. S-nitrosylation of cell death receptor modulates apoptosis. Sorafenib is the unique recommended molecular-targeted drug for the treatment of patients with advanced hepatocellular carcinoma. The present study was addressed to elucidate the potential role of NO during Sorafenib-induced cell death in HepG2 cells. We determined the intra- and extracellular NO concentration, cell death receptor expression and their S-nitrosylation modifications, and apoptotic signaling in Sorafenib-treated HepG2 cells. The effect of NO donors on above parameters has also been determined. Sorafenib induced apoptosis in HepG2 cells. However, low concentration of the drug (10nM) increased cell death receptor expression, as well as caspase-8 and -9 activation, but without activation of downstream apoptotic markers. In contrast, Sorafenib (10 µM) reduced upstream apoptotic parameters but increased caspase-3 activation and DNA fragmentation in HepG2 cells. The shift of cell death signaling pathway was associated with a reduction of S-nitrosylation of cell death receptors in Sorafenib-treated cells. The administration of NO donors increased S-nitrosylation of cell death receptors and overall induction of cell death markers in control and Sorafenib-treated cells. In conclusion, Sorafenib induced alteration of cell death receptor S-nitrosylation status which may have a relevant repercussion on cell death signaling in hepatoblastoma cells.

5-Azacitidine induces demethylation of PTPL1 and inhibits growth in non-Hodgkin lymphoma

Non-Hodgkin lymphoma (NHL) consists of various lymphoid malignancies with a diverse clinical pathology and biological characteristics. Methylation of cytosine residues by DNA methyltransferases at CpG dinucleotides in the promoter region of the genes is a major epigenetic modification in mammalian genomes that can have profound effects on gene expression. The PTPL1 methylation pattern was screened by methylation‑specific polymerase chain reaction (MSP) in 7 lymphoma‑derived cell lines and in 47 samples of diffuse large B cell lymphoma (DLBCL). The PTPL1 gene was hypermethylated in the CA46, Raji, Jurkat and DB cell lines; however, it was unmethylated in the Hut78, Maver and Z138 cell lines. The expression of PTPL1 mRNA was re‑inducible by 5‑azacytidine (5‑Aza), an agent of DNA demethylation. The methylations were detected in 59.6% of DLBCL versus 6.3% in reactive lymph node proliferation. Therefore, the present data showed that PTPL1 was epigenetically regulated in NHL suggesting an involvement of the PTPL1 tumor‑suppressor genes in NHL, and highlights 5-Aza as a potential therapeutic candidate for NHL.

Protein tyrosine phosphatases as potential therapeutic targets

Protein tyrosine phosphorylation is a key regulatory process in virtually all aspects of cellular functions. Dysregulation of protein tyrosine phosphorylation is a major cause of human diseases, such as cancers, diabetes, autoimmune disorders, and neurological diseases. Indeed, protein tyrosine phosphorylation-mediated signaling events offer ample therapeutic targets, and drug discovery efforts to date have brought over two dozen kinase inhibitors to the clinic. Accordingly, protein tyrosine phosphatases (PTPs) are considered next-generation drug targets. For instance, PTP1B is a well-known targets of type 2 diabetes and obesity, and recent studies indicate that it is also a promising target for breast cancer. SHP2 is a bona-fide oncoprotein, mutations of which cause juvenile myelomonocytic leukemia, acute myeloid leukemia, and solid tumors. In addition, LYP is strongly associated with type 1 diabetes and many other autoimmune diseases. This review summarizes recent findings on several highly recognized PTP family drug targets, including PTP1B, Src homology phosphotyrosyl phosphatase 2(SHP2), lymphoid-specific tyrosine phosphatase (LYP), CD45, Fas associated phosphatase-1 (FAP-1), striatal enriched tyrosine phosphatases (STEP), mitogen-activated protein kinase/dual-specificity phosphatase 1 (MKP-1), phosphatases of regenerating liver-1 (PRL), low molecular weight PTPs (LMWPTP), and CDC25. Given that there are over 100 family members, we hope this review will serve as a road map for innovative drug discovery targeting PTPs.

Global PROTOMAP profiling to search for biomarkers of early-recurrent hepatocellular carcinoma

This study used global protein expression profiling to search for biomarkers to predict early recurrent hepatocellular carcinoma (HCC). HCC tissues surgically resected from patients with or without recurrence within 2 years (early recurrent) after surgery were compared with adjacent nontumor tissue and with normal liver tissue. We used the PROTOMAP strategy for comparative profiling, which integrates denaturing polyacrylamide gel electrophoresis migratory rates and high-resolution, semiquantitative mass-spectrometry-based identification of in-gel-digested tryptic peptides. PROTOMAP allows examination of global changes in the size, topography, and abundance of proteins in complex tissue samples. This approach identified 8438 unique proteins from 45 708 nonredundant peptides and generated a proteome-wide map of changes in expression and proteolytic events potentially induced by intrinsic apoptotic/necrotic pathways. In the early recurrent HCC tissue, 87 proteins were differentially expressed (≥20-fold) relative to the other tissues, 46 of which were up-regulated or specifically proteolyzed and 41 of which were down-regulated. This data set consisted of proteins that fell into various functional categories, including signal transduction and cell organization and, notably, the major catalytic pathways responsible for liver function, such as the urea cycle and detoxification metabolism. We found that aberrant proteolysis appeared to occur frequently during recurrence of HCC in several key signal transducers, including STAT1 and δ-catenin. Further investigation of these proteins will facilitate the development of novel clinical applications.

Characterization of calmodulin-Fas death domain interaction: an integrated experimental and computational study

The Fas death receptor-activated death-inducing signaling complex (DISC) regulates apoptosis in many normal and cancer cells. Qualitative biochemical experiments demonstrate that calmodulin (CaM) binds to the death domain of Fas. The interaction between CaM and Fas regulates Fas-mediated DISC formation. A quantitative understanding of the interaction between CaM and Fas is important for the optimal design of antagonists for CaM or Fas to regulate the CaM-Fas interaction, thus modulating Fas-mediated DISC formation and apoptosis. The V254N mutation of the Fas death domain (Fas DD) is analogous to an identified mutant allele of Fas in lpr-cg mice that have a deficiency in Fas-mediated apoptosis. In this study, the interactions of CaM with the Fas DD wild type (Fas DD WT) and with the Fas DD V254N mutant were characterized using isothermal titration calorimetry (ITC), circular dichroism spectroscopy (CD), and molecular dynamics (MD) simulations. ITC results reveal an endothermic binding characteristic and an entropy-driven interaction of CaM with Fas DD WT or with Fas DD V254N. The Fas DD V254N mutation decreased the association constant (Ka) for CaM-Fas DD binding from (1.79 ± 0.20) × 10(6) to (0.88 ± 0.14) × 10(6) M(-1) and slightly increased a standard state Gibbs free energy (ΔG°) for CaM-Fas DD binding from -8.87 ± 0.07 to -8.43 ± 0.10 kcal/mol. CD secondary structure analysis and MD simulation results did not show significant secondary structural changes of the Fas DD caused by the V254N mutation. The conformational and dynamical motion analyses, the analyses of hydrogen bond formation within the CaM binding region, the contact numbers of each residue, and the electrostatic potential for the CaM binding region based on MD simulations demonstrated changes caused by the Fas DD V254N mutation. These changes caused by the Fas DD V254N mutation could affect the van der Waals interactions and electrostatic interactions between CaM and Fas DD, thereby affecting CaM-Fas DD interactions. Results from this study characterize CaM-Fas DD interactions in a quantitative way, providing structural and thermodynamic evidence of the role of the Fas DD V254N mutation in the CaM-Fas DD interaction. Furthermore, the results could help to identify novel strategies for regulating CaM-Fas DD interactions and Fas DD conformation and thus to modulate Fas-mediated DISC formation and thus Fas-mediated apoptosis.

Identification of SLAMF3 (CD229) as an inhibitor of hepatocellular carcinoma cell proliferation and tumour progression

Although hepatocellular carcinoma (HCC) is one of the most common malignancies and constitutes the third leading cause of cancer-related deaths, the underlying molecular mechanisms are not fully understood. In the present study, we demonstrate for the first time that hepatocytes express signalling lymphocytic activation molecule family member 3 (SLAMF3/CD229) but not other SLAMF members. We provide evidence to show that SLAMF3 is involved in the control of hepatocyte proliferation and in hepatocellular carcinogenesis. SLAMF3 expression is significantly lower in primary human HCC samples and HCC cell lines than in human healthy primary hepatocytes. In HCC cell lines, the restoration of high levels of SLAMF3 expression inhibited cell proliferation and migration and enhanced apoptosis. Furthermore, SLAMF3 expression was associated with inhibition of HCC xenograft progression in the nude mouse model. The restoration of SLAMF3 expression levels also decreased the phosphorylation of MAPK ERK1/2, JNK and mTOR. In samples from resected HCC patients, SLAMF3 expression levels were significantly lower in tumorous tissues than in peritumoral tissues. Our results identify SLAMF3 as a specific marker of normal hepatocytes and provide evidence for its potential role in the control of proliferation of HCC cells.

Silencing of Pokemon enhances caspase-dependent apoptosis via fas- and mitochondria-mediated pathways in hepatocellular carcinoma cells

The role of Pokemon (POK erythroid myeloid ontogenic actor), a recently identified POK transcription factor with proto-oncogenic activity, in hepatocellular carcinogenesis has only been assessed by a few studies. Our previous study revealed that Pokemon is overexpressed in hepatocellular carcinomas (HCC) and promotes HCC cell proliferation and migration via an AKT- and ERK- dependent manner. In the present study, we used the TUNEL assay and FACS analysis to demonstrate that oxaliplatin induced apoptosis was significantly increased in cells with silenced Pokemon. Western blots showed that p53 expression and phosphorylation were significantly increased in Pokemon defective cells, thereby initiating the mitochondria-mediated and death receptor-mediated apoptotic pathways. In the mitochondria-mediated pathway, expression of pro-apoptotic Bcl-2 family members (including Bad, Bid, Bim and Puma) as well as AIF was increased and decreasing the mitochondrial membrane potential resulted in cytochrome C released from mitochondrial in HepG2 si-Pokemon cells. In addition, upon oxaliplatin treatment of Pokemon-silenced cells, the FAS receptor, FADD and their downstream targets caspase-10 and caspase-8 were activated, causing increased release of caspase-8 active fragments p18 and p10. Increased activated caspase-8-mediated cleavage and activation of downstream effector caspases such as caspase-9 and caspase-3 was observed in HepG2 si-Pokemon cells as compared to control. Therefore, Pokemon might serve as an important mediator of crosstalk between intrinsic and extrinsic apoptotic pathways in HCC cells. Moreover, our findings suggest that Pokemon could be an attractive therapeutic target gene for human cancer therapy.

Targeting hepatoma using nitric oxide donor strategies

AIMS

The study evaluated the role of increased intracellular nitric oxide (NO) concentration using NO donors or stably NO synthase-3 (NOS-3) overexpression during CD95-dependent cell death in hepatoma cells. The expression of cell death receptors and caspase activation, RhoA kinase activity, NOS-3 expression/activity, oxidative/nitrosative stress, and p53 expression were analyzed. The antitumoral activity of NO was also evaluated in the subcutaneous implantation of NOS-3-overexpressing hepatoma cells, as well NO donor injection into wild-type hepatoma-derived tumors implanted in xenograft mouse models.

RESULTS

NO donor increased CD95 expression and activation of caspase-8 and 3 in HepG2, Huh7, and Hep3B cells. NOS-3 overexpression increased oxidative/nitrosative stress, p53 and CD95 expression, cellular Fas-associated death domain (FADD)-like IL-1beta converting enzyme (FLICE) inhibitory protein long (cFLIP(L)) and its short isoform (cFLIP(S)) shift, and cell death in HepG2 (4TO-NOS) cells. The inhibition of RhoA kinase and p53 knockdown using RNA interference reduced cell death in 4TO-NOS cells. The supplementation with hydrogen peroxide (H(2)O(2)) increased NOS-3 activity and cell death in 4TO-NOS cells. NOS-3 overexpression or NO donor injection into hepatoma-derived tumors reduced the size and increased p53 and cell death receptor expression in nude mice.

INNOVATION AND CONCLUSIONS

The increase of intracellular NO concentration promoted oxidative and nitrosative stress, Rho kinase activity, p53 and CD95 expression, and cell death in cultured hepatoma cells. NOS-3-overexpressed HepG2 cells or intratumoral NO donor administration reduced tumor cell growth and increased the expression of p53 and cell death receptors in tumors developed in a xenograft mouse model.

Functional polymorphisms of FAS and FASL gene and risk of breast cancer - pilot study of 134 cases

Fas/Fas ligand (FasL) system is one of the key apoptotic signaling entities in the extrinsic apoptotic pathway. De-regulation of this pathway, i.e. by mutations may prevent the immune system from the removal of newly-formed tumor cells, and thus lead to tumor formation. The present study investigated the association between −1377 G/A (rs2234767) and −670 A/G (rs1800682) polymorphisms in Fas as well as single nucleotide polymorphisms INV2nt −124 A/G (rs5030772) and −844 C/T (rs763110) in FasL in a sample of Iranian patients with breast cancer. This case-control study was done on 134 breast cancer patients and 152 normal women. Genomic DNA was extracted from whole blood samples. The polymorphisms were determined by using tetra-ARMS-PCR method. There was no significant difference in the genotype distribution of FAS rs2234767 polymorphism between cases and controls. FAS rs1800682, FASL rs5030772, and FASL rs763110 genotypes showed significant associations with an increasing risk of breast cancer (odds ratio OR = 3.18, P = 0.019; OR = 5.08, P = 0.012; OR = 2.40, P = 0.024, respectively). In conclusion, FAS rs2234767 was not associated with breast cancer risk. Though, FAS rs1800682, FASL rs5030772, and FASL rs763110 polymorphisms were associated with the risk of breast cancer in the examined population.

Expression of apoptosis-related genes in the endometrium of polycystic ovary syndrome patients during the window of implantation

The present study investigated the expression of the apoptosis-related genes fas-associated via death domain (FADD) and Bcl-2 in the endometrium during the window of implantation in polycystic ovary syndrome (PCOS) patients. The aim was to explore the role of cell apoptosis in endometrial receptivity during this period. The subjects were divided into experimental and control group. The experimental group comprised 12 infertile women with PCOS, and the control group comprised 12 women who were infertile because of tubal pathological factors but had normal menstrual cycles. Endometria were collected by biopsy 7d after ovulation. Six samples from each group were randomly selected and subjected to gene chip analyses. The expression of endometrial FADD and Bcl-2 was determined by immunohistochemistry, and cell apoptosis was detected by the TUNEL method. Compared with the control group, 194 differentially expressed genes were found in the PCOS group, 102 of which were upregulated and 92 were downregulated. The differentially expressed genes were divided into 15 types according to function. Among the nine genes related to cell apoptosis, five (including Bcl-2) were upregulated and four were downregulated (including FADD). Bcl-2 expression during the window of implantation in the PCOS group increased compared with the control group, showing a significant difference (P<0.05). FADD expression in the PCOS group notably decreased compared with that in the control group, which also showed a significant difference (P<0.05). Cell apoptosis analysis showed a significant difference between the average apoptotic indices in the PCOS and control groups (P<0.05). Significant differences were observed between the endometrial gene expression in the PCOS and control groups. The decrease in cell apoptosis during the window of implantation in PCOS patients may be one of the causes of the reduced endometrial receptivity.

ErbB2, EphrinB1, Src kinase and PTPN13 signaling complex regulates MAP kinase signaling in human cancers

In non-cancerous cells, phosphorylated proteins exist transiently, becoming de-phosphorylated by specific phosphatases that terminate propagation of signaling pathways. In cancers, compromised phosphatase activity and/or expression occur and contribute to tumor phenotype. The non-receptor phosphatase, PTPN13, has recently been dubbed a putative tumor suppressor. It decreased expression in breast cancer correlates with decreased overall survival. Here we show that PTPN13 regulates a new signaling complex in breast cancer consisting of ErbB2, Src, and EphrinB1. To our knowledge, this signaling complex has not been previously described. Co-immunoprecipitation and localization studies demonstrate that EphrinB1, a PTPN13 substrate, interacts with ErbB2. In addition, the oncogenic V660E ErbB2 mutation enhances this interaction, while Src kinase mediates EphrinB1 phosphorylation and subsequent MAP Kinase signaling. Decreased PTPN13 function further enhances signaling. The association of oncogene kinases (ErbB2, Src), a signaling transmembrane ligand (EphrinB1) and a phosphatase tumor suppressor (PTPN13) suggest that EphrinB1 may be a relevant therapeutic target in breast cancers harboring ErbB2-activating mutations and decreased PTPN13 expression.

Trifluoperazine regulation of calmodulin binding to Fas: a computational study

Death-inducing signaling complex (DISC) formation is a critical step in Fas-mediated signaling for apoptosis. Previous experiments have demonstrated that the calmodulin (CaM) antagonist, trifluoperazine (TFP) regulates CaM-Fas binding and affects Fas-mediated DISC formation. In this study, we investigated the anti-cooperative characteristics of TFP binding to CaM and the effect of TFP on the CaM-Fas interaction from both structural and thermodynamic perspectives using combined molecular dynamics simulations and binding free energy analyses. We studied the interactions of different numbers of TFP molecules with CaM and explored the effects of the resulting conformational changes in CaM on CaM-Fas binding. Results from these analyses showed that the number of TFP molecules bound to CaM directly influenced α-helix formation and hydrogen bond occupancy within the α-helices of CaM, contributing to the conformational and motion changes in CaM. These changes affected CaM binding to Fas, resulting in secondary structural changes in Fas and conformational and motion changes of Fas in CaM-Fas complexes, potentially perturbing the recruitment of Fas-associated death domain for DISC formation. The computational results from this study reveal the structural and molecular mechanisms that underlie the role of the CaM antagonist, TFP, in regulation of CaM-Fas binding and Fas-mediated DISC formation in a concentration-dependent manner.

Characterization of chronic HCV infection-induced apoptosis

Background

To understand the complex and largely not well-understood apoptotic pathway and immune system evasion mechanisms in hepatitis C virus (HCV)-associated hepatocellular carcinoma (HCC) and HCV associated chronic hepatitis (CH), we studied the expression patterns of a number of pro-apoptotic and anti-apoptotic genes (Fas, FasL, Bcl-2, Bcl-xL and Bak) in HepG2 cell line harboring HCV- genotype-4 replication. For confirmation, we also assessed the expression levels of the same group of genes in clinical samples obtained from 35 HCC and 34 CH patients.

Methods

Viral replication was assessed in the tissue culture medium by RT-PCR, quantitative Real-Time PCR (qRT-PCR); detection of HCV core protein by western blot and inhibition of HCV replication with siRNA. The expression level of Fas, FasL, Bcl-2, Bcl-xL and Bak was assessed by immunohistochemistry and RT-PCR whereas caspases 3, 8 and 9 were assessed by colorimetric assay kits up to 135 days post infection.

Results

There was a consistent increase in apoptotic activity for the first 4 weeks post-CV infection followed by a consistent decrease up to the end of the experiment. The concordance between the changes in the expression levels of Fas, FasL, Bcl-2, Bcl-xL and Bak in vitro and in situ was statistically significant (p < 0.05). Fas was highly expressed at early stages of infection in cell lines and in normal control liver tissues followed by a dramatic reduction post-HCV infection and an increase in the expression level of FasL post HCV infection. The effect of HCV infection on other apoptotic proteins started very early post-infection, suggesting that hepatitis C modulating apoptosis by modulating intracellular pro-apoptotic signals.

Conclusions

Chronic HCV infection differently modulates the apoptotic machinery during the course of infection, where the virus induces apoptosis early in the course of infection, and as the disease progresses apoptosis is modulated. This study could open a new opportunity for understanding the various signaling of apoptosis and in the developing a targeted therapy to inhibit viral persistence and HCC development.

Potential targets for molecular imaging of apoptosis resistance in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers, which is mainly a concern in Southeast Asia. Apoptosis resistance in HCC is one of the significant factors for hepatocarcinogenesis and tumour progression. Recent advances of apoptosis resistance mechanisms in HCC could serve as potential targets for molecular imaging, which would be of considerable value to explore the molecular processes involved in HCC progression and to evaluate responses of certain anti-HCC therapies. Disruptions in the balance of anti-apoptotic and pro-apoptotic processes have been found to be involved in apoptosis resistance in HCC. Loss of response to death receptors, transformation of growth factor-β induced apoptosis, upregulation of anti-apoptotic Bcl-2 subgroup, as well as downregulation of pro-apoptotic Bax subgroup and BH3-only subgroup, are associated with apoptosis resistance in HCC. Mutation of p53 gene, dysregulation of NF-κB and survivin are also of interest because of their contribution to HCC development. In this review, the aim is to identify potential targets for molecular imaging of apoptosis resistance in HCC.

Cell death and hepatocarcinogenesis: Dysregulation of apoptosis signaling pathways

Hepatocellular carcinoma (HCC) remains a disease with a poor prognosis despite recent advances in the pathophysiology and treatment. Although the disease is biologically heterogeneous, dysregulation of cellular proliferation and apoptosis both occur frequently and contribute to the malignant phenotype. Chronic liver disease is associated with intrahepatic inflammation which promotes dysregulation of cellular signaling pathways; this triggers proliferation and thus lays the ground for expansion of premalignant cells. Cancer emerges when immunological control fails and transformed cells develop resistance against cell death signaling pathways. The same mechanisms underlie the poor responsiveness of HCC towards chemotherapy. Only recently advances in understanding the signaling pathways involved has led to the development of an effective pharmacological therapy for advanced disease. The current review will discuss apoptosis signaling pathways and focus on apoptosis resistance of HCC involving derangements in cell death receptors (e.g. tumor necrosis factor-alpha [TNF], CD95/Apo-1, TNF-related apoptosis-inducing ligand [TRAIL]) and associated adapter molecules (e.g. FADD and FLIP) of apoptotic signaling pathways. In addition, the role of the transcription factor nuclear factor-kappaB (NFκB) and members of the B cell leukemia-2 (Bcl-2) family that contribute to the regulation of apoptosis in hepatocytes are discussed. Eventually, the delineation of cell death signaling pathways could contribute to the implementation of new therapeutic strategies to treat HCC.

Apoptosis as a mechanism for liver disease progression

Hepatocyte injury is ubiquitous in clinical practice, and the mode of cell death associated with this injury is often apoptosis, especially by death receptors. Information from experimental systems demonstrates that hepatocyte apoptosis is sufficient to cause liver hepatic fibrogenesis. The mechanisms linking hepatocyte apoptosis to hepatic fibrosis remain incompletely understood, but likely relate to engulfment of apoptotic bodies by professional phagocytic cells and stellate cells, and release of mediators by cells undergoing apoptosis. Inhibition of apoptosis with caspase inhibitors has demonstrated beneficial effects in murine models of hepatic fibrosis. Recent studies implicating Toll-like receptor 9 in liver injury and fibrosis are also of particular interest. Engulfment of apoptotic bodies is one mechanism by which the TLR9 ligand (CpG DNA motifs) could be delivered to this intracellular receptor. These concepts suggest therapy focused on interrupting the cellular mechanisms linking apoptosis to fibrosis would be useful in human liver diseases.

miR-200c regulates induction of apoptosis through CD95 by targeting FAP-1

Tumor progression shares many characteristics with the process of epithelial-to-mesenchymal transition (EMT). Cells that have undergone an EMT are known to have an increased resistance to apoptosis. CD95/Fas is an apoptosis-inducing receptor expressed on many tissues and tumor cells. During tumor progression CD95 is frequently downregulated, and tumor cells lose apoptosis sensitivity. miR-200 microRNAs repress both the EMT-inducing ZEB1 and ZEB2 transcription factors. We now demonstrate that miR-200c sensitizes cells to apoptosis mediated by CD95. We have identified the apoptosis inhibitor FAP-1 as a target for miR-200c. FAP-1 was demonstrated to be responsible for the reduced sensitivity to CD95-mediated apoptosis in cells with inhibited miR-200. The identification of FAP-1 as an miR-200c target provides a molecular mechanism to explain both the downregulation of CD95 expression and the reduction in sensitivity of cells to CD95-mediated apoptosis that is observed in the context of reduced miR-200 expression during tumor progression.

Genetic polymorphisms in the PTPN13 gene and risk of squamous cell carcinoma of head and neck

Fas-associated phosphatase-1 is encoded by the protein tyrosine phosphatase, non-receptor type 13 (PTPN13) gene and attributes to the resistance to Fas-mediated apoptosis in several tumors, including squamous cell carcinoma of the head and neck (SCCHN). However, no epidemiological studies have investigated the roles of PTPN13 polymorphisms in SCCHN risk. In this hospital-based case-control study of 1069 SCCHN patients and 1102 non-Hispanic white cancer-free controls, we evaluated the associations between three single-nucleotide polymorphisms c.4068 T>G F1356L (rs10033029), c.4566 A>G I1522M (rs2230600) and c.6241 T>G Y2081D (rs989902) located in the coding region of PTPN13 and SCCHN risk. We found that a significantly increased SCCHN risk was associated with the c.4566 I1522M GG genotype [odds ratio (OR), 1.89; 95% confidence interval (CI), 1.27-2.79] and c.6241 Y2081D GT genotype (OR, 1.26; 95% CI, 1.03-1.53) compared with the c.4566 I1522M AA and c.6241 Y2081D TT genotypes, respectively. Further stratified analyses showed that risk associated with the c.4566 I1522M GG genotype was more profound in the subgroups of young (< or = 57 years), males, never smokers, current drinkers and patients with pharyngeal cancer; that risk associated with c.6241 Y2081D GT genotype persisted in subgroups of old (>57 years), males, current drinkers and patients with pharyngeal and laryngeal cancers and that risk associated with c.6241 Y2081D GG genotype was borderline in patients with laryngeal cancer. In conclusion, polymorphisms in the PTPN13 coding region may be biomarkers for susceptibility to SCCHN in USA populations.

Dysregulation of apoptosis in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a major health problem, being the sixth most common cancer world-wide. Dysregulation of the balance between proliferation and cell death represents a pro-tumorigenic principle in human hepatocarcinogenesis. This review updates the recent relevant contributions reporting molecular alterations for HCC that induce an imbalance in the regulation of apoptosis. Alterations in the expression and/or activation of p53 are frequent in HCC cells, which confer on them resistance to chemotherapeutic drugs. Many HCCs are also insensitive to apoptosis induced either by death receptor ligands, such as FasL or TRAIL, or by transforming growth factor-beta (TGF-β). Although the expression of some pro-apoptotic genes is decreased, the balance between death and survival is dysregulated in HCC mainly due to overactivation of anti-apoptotic pathways. Indeed, some molecules involved in counteracting apoptosis, such as Bcl-X_L, Mcl-1, c-IAP1, XIAP or survivin are over-expressed in HCC cells. Furthermore, some growth factors that mediate cell survival are up-regulated in HCC, as well as the molecules involved in the machinery responsible for cleavage of their pro-forms to an active peptide. The expression and/or activation of the JAK/STAT, PI3K/AKT and RAS/ERKs pathways are enhanced in many HCC cells, conferring on them resistance to apoptotic stimuli. Finally, recent evidence indicates that inflammatory processes, as well as the epithelial-mesenchymal transitions that occur in HCC cells to facilitate their dissemination, are related to cell survival. Therefore, therapeutic strategies to selectively inhibit anti-apoptotic signals in liver tumor cells have the potential to provide powerful tools to treat HCC.

PTPL1: a large phosphatase with a split personality

Protein tyrosine phosphatase, PTPL1, (also known as PTPN13, FAP-1, PTP-BAS, PTP1E) is a non-receptor type PTP and, at 270 kDa, is the largest phosphatase within this group. In addition to the well-conserved PTP domain, PTPL1 contains at least 7 putative macromolecular interaction domains. This structural complexity indicates that PTPL1 may modulate diverse cellular functions, perhaps exerting both positive and negative effects. In accordance with this idea, while certain studies suggest that PTPL1 can act as a tumor-promoting gene other experimental studies have suggested that PTPL1 may function as a tumor suppressor. The role of PTPL1 in the cancer cell is therefore likely to be both complex and context dependent with possible roles including the modulation of growth, stress-response, and cytoskeletal remodeling pathways. Understanding the nature of molecular complexes containing PTPL1, its interaction partners, substrates, regulation and subcellular localization are key to unraveling the complex personality of this protein phosphatase.

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.

Fas / FasL system, IL-1beta expression and apoptosis in chronic HBV and HCV liver disease

The Fas / Fas-ligand (FasL) system is an important death signal pathway in the liver. An enhanced local inflammatory response prompted by FasL expression, which contributes to neutrophil recruitment and interleukin-1 beta (IL-1beta) release, seems to be crucial to chronic liver damage, persistence of viral infections, and probably initiation and / or promotion of HCC. In order to evaluate the expression of Fas, FasL, and IL-1beta in different stages of human liver disease and to determine whether hepatitis B virus (HBV) and hepatitis C virus (HCV) infections modulate their expression, also in relation to apoptosis, we examined 87 liver samples obtained from patients with: chronic hepatitis (CH) (n.42), cirrhosis (n.9) and hepatocellular carcinoma (HCC) (n.16) and corresponding peritumoural tissues (n.16); histologically-normal liver (n.4) as controls. Fas, FasL and IL-1beta mRNA were quantified using reverse transcriptase-polymerase chain reaction. The apoptotic index was evaluated by TUNEL analysis. Our data showed a progressive Fas / FasL increase from CH to cirrhosis followed by a decline from the latter to HCC. In histological sections apoptosis was detected in HCC. A significant difference emerged between HCV and HBV-related disease for IL-1beta expression only in CH. A significant positive correlation between IL-1beta and FasL in HCV-related disease (P = 0.014) and an inverse correlation between IL-1beta and Fas in HBV-related disease (P = 0.021) were observed. The different pattern of IL-1beta, Fas and FasL expression found in HCV- and HBV-mediated liver disease, points to a different modulation of immune response B and C virus induced, while the decline in Fas / FasL expression in HCC may be related to defence mechanisms adopted by HCC cells against the immune system.

Expressional and mutational analysis of pro-apoptotic Bcl-2 member PUMA in hepatocellular carcinomas

Deregulation of apoptosis is involved in mechanisms of cancer development. PUMA is a pro-apoptotic member of the Bcl-2 family and mediates p53-dependent and -independent apoptosis. The aim of this study was to investigate whether alterations of PUMA protein expression and somatic mutations of PUMA gene are characteristics of human hepatocellular carcinoma (HCC). We analyzed expression of PUMA protein in 20 HCCs using immunohistochemistry. Also, we analyzed mutation of the Bcl-2 homology 3 (BH3) domain of PUMA gene, which is an important domain in apoptosis function of PUMA by single-strand conformation polymorphism (SSCP) in 69 HCCs. PUMA protein expression was detected in both HCC cells and non-tumor hepatocytes in all of the 20 HCCs. In 10 of these HCCs, cancer cells showed higher PUMA expression than non-tumor (cirrhotic) hepatocytes of the same patients; whereas in the remaining 10, cancer cells and non-tumor hepatocytes showed similar levels. Mutational analysis revealed no PUMA BH3 domain mutation in the 69 HCCs, suggesting that PUMA BH3 domain mutation is not a direct target of inactivation in hepatocellular cancer development. The increased expression of PUMA in malignant hepatocellular cells relative to that in non-tumor hepatocytes suggests that PUMA expression may play a role in HCC development.

Importance of FAS-1377, FAS-670, and FASL-844 polymorphisms in tumor onset, progression, and pigment phenotypes of Swedish patients with melanoma: a case-control analysis

PURPOSE

Human skin melanoma at later stages usually has an extremely poor prognosis. It is of importance to search for biologic markers to identify and monitor individuals at risk for melanoma for early diagnosis and to avoid tumor progression. The FAS gene and its natural ligand (FASL) gene initiate the death signal cascade, playing a central role in the apoptotic signaling pathway and tumor growth and metastasis.

PATIENTS AND METHODS

In this study, we analyzed polymorphisms in 229 patients with melanoma and 351 age- and gender-matched tumor-free individuals. Genomic DNAs were isolated from mononuclear cells in peripheral vein blood, and the polymorphisms were examined with polymerase chain reaction-restriction fragment length polymorphism techniques. Frequency in distribution of the polymorphisms was compared between the patients with melanoma and the healthy control subjects, and associations with patients' pigment phenotypes, age at diagnosis, and melanoma characteristics were analyzed.

RESULTS AND CONCLUSIONS

The FAS-1377, FAS-670, and FASL-844 polymorphisms were not found to be markers of melanoma risk (P > 0.05). In patients with melanoma, frequencies of the FAS-1377, FAS-670, and FASL-844 polymorphisms were different between the patients aged <50 and > or =50 years (P < or = 0.025, P < or = 0.025, and P < or = 0.01). Moreover, the FAS-670 polymorphism correlated with tumor Breslow thickness (P < or = 0.01) and Clark level (P < or = 0.001) and was associated with tumors developing in sun-exposed locations (P < or = 0.001). FAS and FASL were not markers for melanoma risk but might be important in the development and progression of sun-induced melanoma independently of skin type.

Putative association of Fas and FasL gene polymorphisms with clinical outcomes of hepatitis B virus infection

OBJECTIVE

Fas/FasL polymorphisms, which are related to apoptosis, might influence the clearance of hepatitis B virus (HBV) infection and the occurrence of hepatocellular carcinoma (HCC). This study was performed to determine whether Fas and FasL promoter polymorphisms are associated with clinical outcome in chronic HBV infection.

METHODS

A total of 1,095 Korean subjects were prospectively allocated to two different groups: 'the chronic carrier group' (CC; n = 666), who were repeatedly hepatitis B surface antigen (HBsAg)-positive, and 'the spontaneous recovery group' (SR; n = 429), who were HBsAg-negative with antibodies to HBsAg and hepatitis B core antigen. In addition, the CC group was subcategorized into chronic hepatitis and HCC subgroups. Fas promoter polymorphisms at -1377G>A and -670A>G and the FasL promoter polymorphism at -844C>T were analyzed for and the genotype distributions of subjects were compared.

RESULTS

There were no significant associations between Fas or FasL promoter polymorphism with the HBV clearance and HBeAg clearance. However, -1377G>A in Fas promoter region showed protective effect to HCC occurrence (RH = 0.70, p = 0.03).

CONCLUSIONS

Fas-1377G>A polymorphisms might be involved in the pathogenesis of human HCC.

FAP-1-mediated activation of NF-kappaB induces resistance of head and neck cancer to Fas-induced apoptosis

Molecular mechanisms responsible for tumor resistance to apoptosis often involve the Fas/FasL pathway. While squamous cell carcinomas of the head and neck (SCCHN) express both Fas and FasL, their resistance to self-induced apoptosis or apoptosis mediated by Fas agonistic antibody (CH-11Ab) was independent of the level of Fas surface expression or the presence of soluble Fas in supernatants of primary or metastatic SCCHN cell lines. By in vitro immunoselection, using PCI-15A cell line treated with successive cycles of CH-11 Ab, Fas-resistant sublines with the parental genotype were selected. Such sublines failed to cleave caspase-8 upon Fas engagement and were resistant to CH-11 Ab, although they remained sensitive to VP-16 or staurosporin. In the presence of cycloheximide, the selected SCCHN sublines become susceptible to CH-11 Ab, and showed cleavage of caspase-8, suggesting that apoptosis resistance was mediated by an inhibitory protein(s) acting upstream of caspase-8. Overexpression of Fas-associated phosphatase 1 (FAP-1), but not cellular FLICE-inhibitory protein (cFLIP) in SCCHN sublines was documented by Western blots and RT-PCR analyses. The FAP-1+ selected sublines also downregulated cell surface Fas. A high phosphorylation level of IkappaB kappa, NFkappaB activation and upregulation of Bcl-2 expression were observed in the FAP-1+ sublines. Treatment with the phosphatase inhibitor, orthovanadate, or silencing of FAP-1 with siRNA abolished their resistance to apoptosis, suggesting that FAP-1 phosphatase activity could be responsible for NF-kappaB activation and resistance of SCCHN cells to Fas-mediated apoptosis.

Regulation of TRP channel TRPM2 by the tyrosine phosphatase PTPL1

TRPM2, a member of the transient receptor potential (TRP) superfamily, is a Ca(2+)-permeable channel, which mediates susceptibility to cell death following activation by oxidative stress, TNFalpha, or beta-amyloid peptide. We determined that TRPM2 is rapidly tyrosine phosphorylated after stimulation with H(2)O(2) or TNFalpha. Inhibition of tyrosine phosphorylation with the tyrosine kinase inhibitors genistein or PP2 significantly reduced the increase in [Ca(2+)](i) observed after H(2)O(2) or TNFalpha treatment in TRPM2-expressing cells, suggesting that phosphorylation is important in TRPM2 activation. Utilizing a TransSignal PDZ domain array blot to identify proteins which interact with TRPM2, we identified PTPL1 as a potential binding protein. PTPL1 is a widely expressed tyrosine phosphatase, which has a role in cell survival and tumorigenesis. Immunoprecipitation and glutathione-S-transferase pull-down assays confirmed that TRPM2 and PTPL1 interact. To examine the ability of PTPL1 to modulate phosphorylation or activation of TRPM2, PTPL1 was coexpressed with TRPM2 in human embryonic kidney-293T cells. This resulted in significantly reduced TRPM2 tyrosine phosphorylation, and inhibited the rise in [Ca(2+)](i) and the loss of cell viability, which follow H(2)O(2) or TNFalpha treatment. Consistent with these findings, reduction in endogenous PTPL1 expression with small interfering RNA resulted in increased TRPM2 tyrosine phosphorylation, a significantly greater rise in [Ca(2+)](i) following H(2)O(2) treatment, and enhanced susceptibility to H(2)O(2)-induced cell death. Endogenous TRPM2 and PTPL1 was associated in U937-ecoR cells, confirming the physiological relevance of this interaction. These data demonstrate that tyrosine phosphorylation of TRPM2 is important in its activation and function and that inhibition of TRPM2 tyrosine phosphorylation reduces Ca(2+) influx and protects cell viability. They also suggest that modulation of TRPM2 tyrosine phosphorylation is a mechanism through which PTPL1 may mediate resistance to cell death.

Cyclo-oxygenase 2 expression impairs serum-withdrawal-induced apoptosis in liver cells

We have investigated the mechanism of COX-2 (cyclo-oxygenase 2)-dependent inhibition of apoptosis in liver, a key pathway underlying proliferative actions of COX-2 in liver cancers, cirrhosis, chronic hepatitis C infection and regeneration after partial hepatectomy. Stable expression of COX-2 in CHL (Chang liver) cells induced proliferation, with an increase in the proportion of cells in S-phase, but no other significant changes in cell-cycle distribution. This was associated with a marked inhibition of the apoptotic response to serum deprivation, an effect mimicked by treating empty-vector-transfected control cells (CHL-V cells) with prostaglandin E2 and prevented in COX-2-expressing cells (CHL-C cells) treated with selective inhibitors of COX-2. Serum-deprived CHL-V cells displayed several indicators of activation of intrinsic apoptosis: caspases 9 and 3 activated within 6 h and caspase 8 within 18 h, Bax expression was induced, cytochrome c was released to the cytosol, and PARP-1 [poly(ADP-ribose) polymerase 1] cleavage was evident in nuclei. COX-2 expression blocked these events, concomitant with reduced expression of p53 and promotion of Akt phosphorylation, the latter indicating activation of survival pathways. CHL cells were resistant to stimulation of the extrinsic pathway with anti-Fas antibody. Moreover, in vivo expression of GFP (green fluorescent protein)-labelled COX-2 in mice by hydrodynamics-based transient transfection conferred resistance to caspase 3 activation and apoptosis induced by stimulation of Fas.

L’apoptose hépatique

Apoptosis or programmed cell death occurs in the liver as in other organs. In the normal state it is not a frequent mode of hepatic cell destruction. Morphological and biochemical characteristics of liver cell apoptosis do not differ from what is observed in other cells. The Fas receptor pathway, a frequent hepatic apoptotic pathway among various others, involves intra-cellular signals amplified by mitochondria. Although hepatic apoptosis may occur by following several others pathways, Fas, which is abundantly expressed in the plasma membrane of hepatocytes, is very often involved in hepatocyte demise during B or C viral hepatitis irrespective of their clinical form, alcoholic hepatitis, cholestasis due to accumulation of hepatic biliary salts, or certain types of drug-induced hepatitis. Fas is also probably responsible for the death of biliary cells in primary biliary cirrhosis. In contrast one of the causes of resistance to apoptosis of hepatic cancerous cells could be related to an alteration of the Fas receptor. This is why much experimental work is presently performed to achieve inhibition of the Fas receptor either at the mRNA level or at the level of Fas-inductible proteolytic enzymes called caspases. One perspective is a specific treatment of apoptosis as an adjuvant treatment of liver diseases.

The role of the tumor necrosis factor (TNF)--Fas L and HCV in the development of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major public health problem in Egypt due to the high prevalence of hepatitis C viral (HCV) infection. The mechanism by which HCV exerts its carcinogenic effect on the liver is not yet understood. Previous research has suggested that perturbations of the Fas-Fas L tumor necrosis system could result in uncontrolled cancerous cell growth in the liver. This study aims to assess the relationship of Fas ligand (Fas L) to HCC. A total of 28 cases (HCC) and 56 controls (28 cirrhosis and 28 chronic hepatitis) were included in the study. Sera and tissue biopsies were tested for HCV antibody and HCV-RNA. Fas ligand expression in tissue was examined immunohistochemically using a rabbit purified polyclonal antibody. Levels of soluble Fas L were determined in serum by ELISA. The HCC cases were graded as: 17.9% Grade I, 32.1% Grade II, 35.7% Grade III and 14.3% were Grade IV. Among the cases, 81% had evidence of cirrhosis. All the cases and controls were positive for HCV-RNA. Tissue and serum PCR results were identical within the same subjects. Fas ligand cytoplasmic expression was more pronounced in HCC than in cirrhosis, and in cirrhosis more than in chronic hepatitis. This expression was higher with increasing grades of malignancy and in tissues adjacent to the tumor, than in those without nearby tumor. Soluble Fas L levels were higher in cases than in controls, with similar results as that of immunohistochemical expression. These results suggest that HCV and Fas ligand play a key role in hepatocarcinogenesis, consistent with the hypothesis that HCV induces overexpression of Fas ligand in the liver cells, resulting in escape from killing by the immune system cells, with subsequent uncontrolled growth of tissue and the development of malignancy.

Mechanism of counterattack of colorectal cancer cell by Fas/Fas ligand system

AIM: To determine the role of Fas/Fas ligand (FasL) in the immune escape of colon cancer cells.

METHODS: Immunohistochemistry was used to observe the expression of Fas and FasL in the tissues of colon cancer patients.In situ hybridization was used to detect the localization of FasL mRNA expression in cancer tissues. Terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay and CD45 staining were performed to detect the apoptosis of tumor-infiltrating lymphocytes (TILs). Co-culture assays of colon cancer cells (SW480) and Jurkat cells (Fas-sensitive cells) were performed to observe the counterattack of colon cancer cells to lymphocytes.

RESULTS: Of 53 cases of colon carcinomas, 23 cases (43.4%) expressed Fas which was significantly lower as compared to the normal colonic mucosa (73.3%, P<0.01), and 45 cases (84.9%) of colon carcinomas expressed FasL, whereas only two cases (3.75%) in normal mucosa expressed FasL. FasL expression in the colon cancer cells was found to be associated with increased cell death of TILs. The apoptotic rate of TIL in the FasL-positive staining regions of tumor cells was significantly higher than that in the FasL-negative staining region (54.84 ± 2.79% vs 25.73 ± 1.98%, P<0.01). The co-culture of SW480 cells and Jurkat cells confirmed the function of FasL on the SW480 cells. The apoptotic rates of Jurkat cells were found to be related with the amount of SW480 cells.

CONCLUSION: Colon cancer cells can escape the immune surveillance and killing via decreasing Fas expression, and can counterattack the immune system via increasing FasL expression. Fas/FasL can serve as potential targets for effective antitumor therapy.

Effects of alpha fetoprotein on escape of Bel 7402 cells from attack of lymphocytes

Background

Involvement of AFP against apoptosis of tumor cell has been implicated in its evasion of immune surveillance. However, the molecular events of immune escape mechanisms are still unknown. The major observations reported here relate to a possible mechanism by which heptoloma Bel 7402 cells escape immune surveillance in vitro.

Methods

Western blotting and a well-characterized cofocal scanning image were performed to analyze the expression of Fas/FasL and caspase-3 in co-cultured Bel 7402 and Jurkat cells.

Results

After co-culture with Jurkat cells, up-regulated Fas and reduced FasL expression could be observed. Treatment with AFP could remarkably inhibit the elevated Fas and, whereas, induce the FasL expression in co-cultured Bel 7402 cells. Cells co-culture could induce the expression of caspase-3 in both cells line. The elevated caspase-3 in Bel 7402 cells was abolished following the treatment of AFP. The expression of caspase-3 was elevated in co-cultured Jurkat cells treated with AFP. No detectable change on the expression of survivin was examined in both cells line. Monoclonal antibody against AFP treatment alone did not obviously influence the growth of cells, as well as the expression of Fas/FasL and caspase-3. However, the effect of AFP could be blocked by antibody.

Conclusions

our results provide evidence that AFP could promote the escape of liver cancer cells from immune surveillance through blocking the caspase signal pathway of tumor cells and triggering the Fas/FasL interaction between tumor cells and lymphocytes.

Effects of alpha fetoprotein on escape of Bel 7402 cells from attack of lymphocytes

BACKGROUND

Involvement of AFP against apoptosis of tumor cell has been implicated in its evasion of immune surveillance. However, the molecular events of immune escape mechanisms are still unknown. The major observations reported here relate to a possible mechanism by which heptoloma Bel 7402 cells escape immune surveillance in vitro.

METHODS

Western blotting and a well-characterized cofocal scanning image were performed to analyze the expression of Fas/FasL and caspase-3 in co-cultured Bel 7402 and Jurkat cells.

RESULTS

After co-culture with Jurkat cells, up-regulated Fas and reduced FasL expression could be observed. Treatment with AFP could remarkably inhibit the elevated Fas and, whereas, induce the FasL expression in co-cultured Bel 7402 cells. Cells co-culture could induce the expression of caspase-3 in both cells line. The elevated caspase-3 in Bel 7402 cells was abolished following the treatment of AFP. The expression of caspase-3 was elevated in co-cultured Jurkat cells treated with AFP. No detectable change on the expression of survivin was examined in both cells line. Monoclonal antibody against AFP treatment alone did not obviously influence the growth of cells, as well as the expression of Fas/FasL and caspase-3. However, the effect of AFP could be blocked by antibody.

CONCLUSIONS

our results provide evidence that AFP could promote the escape of liver cancer cells from immune surveillance through blocking the caspase signal pathway of tumor cells and triggering the Fas/FasL interaction between tumor cells and lymphocytes.