Beyond the barrier: the immune-inspired pathways of tumor extravasation

Extravasation is a fundamental step in the metastatic journey, where cancer cells exit the bloodstream and breach the endothelial cell barrier to infiltrate target tissues. The tactics cancer cells employ are sophisticated, closely reflecting those used by the immune system for tissue surveillance. Remarkably, tumor cells have been observed to form distinct associations or clusters with immune cells where neutrophils stand out as particularly crucial partners. These interactions are not accidental; they are critical for cancer cells to exploit the immune functions of neutrophils and successfully extravasate. In another strategy, tumor cells mimic the behavior and characteristics of immune cells. They release a suite of inflammatory mediators, which under normal circumstances, guide the processes of endothelium reshaping and facilitate the entry and movement of immune cells within tissues. In this review, we offer a new perspective on the tactics employed by cancer cells to extravasate and infiltrate target tissues. We delve into the myriad mechanisms that tumor cells borrow, adapt, and refine from the immune playbook. Video Abstract.

Molecular insights into RmcA-mediated c-di-GMP consumption: Linking redox potential to biofilm morphogenesis in Pseudomonas aeruginosa

The ability of many bacteria to form biofilms contributes to their resilience and makes infections more difficult to treat. Biofilm growth leads to the formation of internal oxygen gradients, creating hypoxic subzones where cellular reducing power accumulates, and metabolic activities can be limited. The pathogen Pseudomonas aeruginosa counteracts the redox imbalance in the hypoxic biofilm subzones by producing redox-active electron shuttles (phenazines) and by secreting extracellular matrix, leading to an increased surface area-to-volume ratio, which favors gas exchange. Matrix production is regulated by the second messenger bis-(3',5')-cyclic-dimeric-guanosine monophosphate (c-di-GMP) in response to different environmental cues. RmcA (Redox modulator of c-di-GMP) from P. aeruginosa is a multidomain phosphodiesterase (PDE) that modulates c-di-GMP levels in response to phenazine availability. RmcA can also sense the fermentable carbon source arginine via a periplasmic domain, which is linked via a transmembrane domain to four cytoplasmic Per-Arnt-Sim (PAS) domains followed by a diguanylate cyclase (DGC) and a PDE domain. The biochemical characterization of the cytoplasmic portion of RmcA reported in this work shows that the PAS domain adjacent to the catalytic domain tunes RmcA PDE activity in a redox-dependent manner, by differentially controlling protein conformation in response to FAD or FADH2. This redox-dependent mechanism likely links the redox state of phenazines (via FAD/FADH2 ratio) to matrix production as indicated by a hyperwrinkling phenotype in a macrocolony biofilm assay. This study provides insights into the role of RmcA in transducing cellular redox information into a structural response of the biofilm at the population level. Conditions of resource (i.e. oxygen and nutrient) limitation arise during chronic infection, affecting the cellular redox state and promoting antibiotic tolerance. An understanding of the molecular linkages between condition sensing and biofilm structure is therefore of crucial importance from both biological and engineering standpoints.

Targeting the Grb2 cSH3 domain: Design, synthesis and biological evaluation of the first series of modulators

Growth factor receptor bound protein 2 (Grb2) is an adaptor protein featured by a nSH3-SH2-cSH3 domains. Grb2 finely regulates important cellular pathways such as growth, proliferation and metabolism and a minor lapse of this tight control may totally change the entire pathway to the oncogenic. Indeed, Grb2 is found overexpressed in many tumours type. Consequently, Grb2 is an attractive therapeutic target for the development of new anticancer drug. Herein, we reported the synthesis and the biological evaluation of a series of Grb2 inhibitors, developed starting from a hit-compound already reported by this research unit. The newly synthesized compounds were evaluated by kinetic binding experiments, and the most promising derivatives were assayed in a short panel of cancer cells. Five of the newly synthesized derivatives proved to be able to bind the targeted protein with valuable inhibitory concentration in one-digit micromolar concentration. The most active compound of this series, derivative 12, showed an inhibitory concentration of about 6 μM for glioblastoma and ovarian cancer cells, and an IC50 of 1.67 for lung cancer cell. For derivative 12, the metabolic stability and the ROS production was also evaluated. The biological data together with the docking studies led to rationalize an early structure activity relationship.

Extracellular serine empowers epidermal proliferation and psoriasis-like symptoms

The contribution of nutrient availability to control epidermal cell proliferation, inflammation, and hyperproliferative diseases remains unknown. Here, we studied extracellular serine and serine/glycine metabolism using human keratinocytes, human skin biopsies, and a mouse model of psoriasis-like disease. We focused on a metabolic enzyme, serine hydroxymethyltransferase (SHMT), that converts serine into glycine and tetrahydrofolate-bound one‑carbon units to support cell growth. We found that keratinocytes are both serine and glycine auxotrophs. Metabolomic profiling and hypoxanthine supplementation indicated that SHMT silencing/inhibition reduced cell growth through purine depletion, leading to nucleotide loss. In addition, topical application of an SHMT inhibitor suppressed both keratinocyte proliferation and inflammation in the imiquimod model and resulted in a decrease in psoriasis-associated gene expression. In conclusion, our study highlights SHMT2 activity and serine/glycine availability as an important metabolic hub controlling both keratinocyte proliferation and inflammatory cell expansion in psoriasis and holds promise for additional approaches to treat skin diseases.

Inhibition of Glycolysis Impairs Retinoic Acid-Inducible Gene I–Mediated Antiviral Responses in Primary Human Dendritic Cells

Dendritic cells (DCs) are important mediators of the induction and regulation of adaptive immune responses following microbial infection and inflammation. Sensing environmental danger signals including viruses, microbial products, or inflammatory stimuli by DCs leads to the rapid transition from a resting state to an activated mature state. DC maturation involves enhanced capturing and processing of antigens for presentation by major histocompatibility complex (MHC) class I and class II, upregulation of chemokines and their receptors, cytokines and costimulatory molecules, and migration to lymphoid tissues where they prime naive T cells. Orchestrating a cellular response to environmental threats requires a high bioenergetic cost that accompanies the metabolic reprogramming of DCs during activation. We previously demonstrated that DCs undergo a striking functional transition after stimulation of the retinoic acid-inducible gene I (RIG-I) pathway with a synthetic 5′ triphosphate containing RNA (termed M8), consisting of the upregulation of interferon (IFN)–stimulated antiviral genes, increased DC phagocytosis, activation of a proinflammatory phenotype, and induction of markers associated with immunogenic cell death. In the present study, we set out to determine the metabolic changes associated with RIG-I stimulation by M8. The rate of glycolysis in primary human DCs was increased in response to RIG-I activation, and glycolytic reprogramming was an essential requirement for DC activation. Pharmacological inhibition of glycolysis in monocyte-derived dendritic cells (MoDCs) impaired type I IFN induction and signaling by disrupting the TBK1-IRF3-STAT1 axis, thereby countering the antiviral activity induced by M8. Functionally, the impaired IFN response resulted in enhanced viral replication of dengue, coronavirus 229E, and Coxsackie B5.

Anticancer Activity of (S)-5-Chloro-3-((3,5-dimethylphenyl)sulfonyl)-N-(1-oxo-1-((pyridin-4-ylmethyl)amino)propan-2-yl)-1H-indole-2-carboxamide (RS4690), a New Dishevelled 1 Inhibitor

Simple Summary

The WNT/β-catenin pathway regulates a huge number of cellular functions, and its dysregulation is correlated to the development of cancer. In this work, we focused on the interaction between Dishevelled 1 (DVL1) protein, an important player in this pathway, and its cognate receptor Frizzled via a shared PDZ domain. Computational studies led to the discovery of racemate RS4690 (1) showing selective inhibition of DVL1 binding. After separation of the racemic mixture, enantiomer (S)-1 inhibited DVL1 with an EC₅₀ of 0.49 ± 0.11 μM and the growth of HCT116 cells that did not present the APC mutation with an EC₅₀ value 7.1 ± 0.6 μM, and caused a high level of ROS production. Compound (S)-1 shows potential as a new therapeutic agent against WNT-dependent colon cancer.

Abstract

Wingless/integrase-11 (WNT)/β-catenin pathway is a crucial upstream regulator of a huge array of cellular functions. Its dysregulation is correlated to neoplastic cellular transition and cancer proliferation. Members of the Dishevelled (DVL) family of proteins play an important role in the transduction of WNT signaling by contacting its cognate receptor, Frizzled, via a shared PDZ domain. Thus, negative modulators of DVL1 are able to impair the binding to Frizzled receptors, turning off the aberrant activation of the WNT pathway and leading to anti-cancer activity. Through structure-based virtual screening studies, we identified racemic compound RS4690 (1), which showed a promising selective DVL1 binding inhibition with an EC₅₀ of 0.74 ± 0.08 μM. Molecular dynamic simulations suggested a different binding mode for the enantiomers. In the in vitro assays, enantiomer (S)-1 showed better inhibition of DVL1 with an EC₅₀ of 0.49 ± 0.11 μM compared to the (R)-enantiomer. Compound (S)-1 inhibited the growth of HCT116 cells expressing wild-type APC with an EC₅₀ of 7.1 ± 0.6 μM and caused a high level of ROS production. These results highlight (S)-1 as a lead compound for the development of new therapeutic agents against WNT-dependent colon cancer.

Cytosolic localization and in vitro assembly of human de novo thymidylate synthesis complex

De novo thymidylate synthesis is a crucial pathway for normal and cancer cells. Deoxythymidine monophosphate (dTMP) is synthesized by the combined action of three enzymes: serine hydroxymethyltransferase (SHMT1), dihydrofolate reductase (DHFR) and thymidylate synthase (TYMS), with the latter two being targets of widely used chemotherapeutics such as antifolates and 5‐fluorouracil. These proteins translocate to the nucleus after SUMOylation and are suggested to assemble in this compartment into the thymidylate synthesis complex. We report the intracellular dynamics of the complex in cancer cells by an in situ proximity ligation assay, showing that it is also detected in the cytoplasm. This result indicates that the role of the thymidylate synthesis complex assembly may go beyond dTMP synthesis. We have successfully assembled the dTMP synthesis complex in vitro, employing tetrameric SHMT1 and a bifunctional chimeric enzyme comprising human thymidylate synthase and dihydrofolate reductase. We show that the SHMT1 tetrameric state is required for efficient complex assembly, indicating that this aggregation state is evolutionarily selected in eukaryotes to optimize protein–protein interactions. Lastly, our results regarding the activity of the complete thymidylate cycle in vitro may provide a useful tool with respect to developing drugs targeting the entire complex instead of the individual components.

The Emerging Role of Amino Acids of the Brain Microenvironment in the Process of Metastasis Formation

Brain metastases are the most severe clinical manifestation of aggressive tumors. Melanoma, breast, and lung cancers are the types that prefer the brain as a site of metastasis formation, even if the reasons for this phenomenon still remain to be clarified. One of the main characteristics that makes a cancer cell able to form metastases in the brain is the ability to interact with the endothelial cells of the microvasculature, cross the blood-brain barrier, and metabolically adapt to the nutrients available in the new microenvironment. In this review, we analyzed what makes the brain a suitable site for the development of metastases and how this microenvironment, through the continuous release of neurotransmitters and amino acids in the extracellular milieu, is able to support the metabolic needs of metastasizing cells. We also suggested a possible role for amino acids released by the brain through the endothelial cells of the blood-brain barrier into the bloodstream in triggering the process of extravasation/invasion of the brain parenchyma.

Modelling of SHMT1 riboregulation predicts dynamic changes of serine and glycine levels across cellular compartments

Human serine hydroxymethyltransferase (SHMT) regulates the serine-glycine one carbon metabolism and plays a role in cancer metabolic reprogramming. Two SHMT isozymes are acting in the cell: SHMT1 encoding the cytoplasmic isozyme, and SHMT2 encoding the mitochondrial one. Here we present a molecular model built on experimental data reporting the interaction between SHMT1 protein and SHMT2 mRNA, recently discovered in lung cancer cells. Using a stochastic dynamic model, we show that RNA moieties dynamically regulate serine and glycine concentration, shaping the system behaviour. For the first time we observe an active functional role of the RNA in the regulation of the serine-glycine metabolism and availability, which unravels a complex layer of regulation that cancer cells exploit to fine tune amino acids availability according to their metabolic needs. The quantitative model, complemented by an experimental validation in the lung adenocarcinoma cell line H1299, exploits RNA molecules as metabolic switches of the SHMT1 activity. Our results pave the way for the development of RNA-based molecules able to unbalance serine metabolism in cancer cells.

Biophysical characterization of melanoma cell phenotype markers during metastatic progression

Melanoma is the most fatal form of skin cancer, with increasing prevalence worldwide. The most common melanoma genetic driver is mutation of the proto-oncogene serine/threonine kinase BRAF; thus, the inhibition of its MAP kinase pathway by specific inhibitors is a commonly applied therapy. However, many patients are resistant, or develop resistance to this type of monotherapy, and therefore combined therapies which target other signaling pathways through various molecular mechanisms are required. A possible strategy may involve targeting cellular energy metabolism, which has been recognized as crucial for cancer development and progression and which connects through glycolysis to cell surface glycan biosynthetic pathways. Protein glycosylation is a hallmark of more than 50% of the human proteome and it has been recognized that altered glycosylation occurs during the metastatic progression of melanoma cells which, in turn facilitates their migration. This review provides a description of recent advances in the search for factors able to remodel cell metabolism between glycolysis and oxidative phosphorylation, and of changes in specific markers and in the biophysical properties of cells during melanoma development from a nevus to metastasis. This development is accompanied by changes in the expression of surface glycans, with corresponding changes in ligand-receptor affinity, giving rise to structural features and viscoelastic parameters particularly well suited to study by label-free biophysical methods.

High-Fat Diet Leads to Reduced Protein O-GlcNAcylation and Mitochondrial Defects Promoting the Development of Alzheimer's Disease Signatures

The disturbance of protein O-GlcNAcylation is emerging as a possible link between altered brain metabolism and the progression of neurodegeneration. As observed in brains with Alzheimer's disease (AD), flaws of the cerebral glucose uptake translate into reduced protein O-GlcNAcylation, which promote the formation of pathological hallmarks. A high-fat diet (HFD) is known to foster metabolic dysregulation and insulin resistance in the brain and such effects have been associated with the reduction of cognitive performances. Remarkably, a significant role in HFD-related cognitive decline might be played by aberrant protein O-GlcNAcylation by triggering the development of AD signature and mitochondrial impairment. Our data support the impairment of total protein O-GlcNAcylation profile both in the brain of mice subjected to a 6-week high-fat-diet (HFD) and in our in vitro transposition on SH-SY5Y cells. The reduction of protein O-GlcNAcylation was associated with the development of insulin resistance, induced by overfeeding (i.e., defective insulin signaling and reduced mitochondrial activity), which promoted the dysregulation of the hexosamine biosynthetic pathway (HBP) flux, through the AMPK-driven reduction of GFAT1 activation. Further, we observed that a HFD induced the selective impairment of O-GlcNAcylated-tau and of O-GlcNAcylated-Complex I subunit NDUFB8, thus resulting in tau toxicity and reduced respiratory chain functionality respectively, highlighting the involvement of this posttranslational modification in the neurodegenerative process.

Cytosolic serine hydroxymethyltransferase controls lung adenocarcinoma cells migratory ability by modulating AMP kinase activity

Nutrient utilization and reshaping of metabolism in cancer cells is a well-known driver of malignant transformation. Less clear is the influence of the local microenvironment on metastasis formation and choice of the final organ to invade. Here we show that the level of the amino acid serine in the cytosol affects the migratory properties of lung adenocarcinoma (LUAD) cells. Inhibition of serine or glycine uptake from the extracellular milieu, as well as knockdown of the cytosolic one-carbon metabolism enzyme serine hydroxymethyltransferase (SHMT1), abolishes migration. Using rescue experiments with a brain extracellular extract, and direct measurements, we demonstrate that cytosolic serine starvation controls cell movement by increasing reactive oxygen species formation and decreasing ATP levels, thereby promoting activation of the AMP sensor kinase (AMPK) by phosphorylation. Activation of AMPK induces remodeling of the cytoskeleton and finally controls cell motility. These results highlight that cytosolic serine metabolism plays a key role in controlling motility, suggesting that cells are able to dynamically exploit the compartmentalization of this metabolism to adapt their metabolic needs to different cell functions (movement vs. proliferation). We propose a model to explain the relevance of serine/glycine metabolism in the preferential colonization of the brain by LUAD cells and suggest that the inhibition of serine/glycine uptake and/or cytosolic SHMT1 might represent a successful strategy to limit the formation of brain metastasis from primary tumors, a major cause of death in these patients.

Lung cancer is a very aggressive tumor that often forms brain metastases. We show that lung cancer cells motility, fundamental for the formation of metastases, is controlled by amino acids such as serine and glycine, abundant in brain microenvironment.

The moonlighting RNA-binding activity of cytosolic serine hydroxymethyltransferase contributes to control compartmentalization of serine metabolism

Enzymes of intermediary metabolism are often reported to have moonlighting functions as RNA-binding proteins and have regulatory roles beyond their primary activities. Human serine hydroxymethyltransferase (SHMT) is essential for the one-carbon metabolism, which sustains growth and proliferation in normal and tumour cells. Here, we characterize the RNA-binding function of cytosolic SHMT (SHMT1) in vitro and using cancer cell models. We show that SHMT1 controls the expression of its mitochondrial counterpart (SHMT2) by binding to the 5'untranslated region of the SHMT2 transcript (UTR2). Importantly, binding to RNA is modulated by metabolites in vitro and the formation of the SHMT1-UTR2 complex inhibits the serine cleavage activity of the SHMT1, without affecting the reverse reaction. Transfection of UTR2 in cancer cells controls SHMT1 activity and reduces cell viability. We propose a novel mechanism of SHMT regulation, which interconnects RNA and metabolites levels to control the cross-talk between cytosolic and mitochondrial compartments of serine metabolism.

Linking Infection and Prostate Cancer Progression: Toll-like Receptor3 Stimulation Rewires Glucose Metabolism in Prostate Cells

BACKGROUND/AIM

The connection between prostate cancer and inflammation has been proposed many years ago, but very little is known about the metabolic adaptations of prostate cells in case of infection or inflammation. The aim of this study was to examine the effect of the stimulation of Toll-like receptor 3 (TLR3) on the metabolism of prostate cancer (PCa) cell lines and benign prostate cells.

MATERIALS AND METHODS

Cytofluorimetry, qRT-PCR, western blot and Gas-chromatography/Mass-spectrometry were used.

RESULTS

Reprogramming of glucose utilization involving hypoxia-inducible factor 1-alpha (HIF-1α) and the extracellular adenosine axis was observed. TLR3 stimulation synergized with adenosine receptor A2b on PCa cells, and induced a strong production of lactate, exacerbating the Warburg effect. Moreover, stimulation of benign prostate cells with poly I:C reduced lactate secretion, a characteristic typical of the neoplastic transformation.

CONCLUSION

TLR3 stimulation promotes metabolic adaptations likely involved in the mechanisms of disease onset and progression.

Beyond nitrogen metabolism: nitric oxide, cyclic-di-GMP and bacterial biofilms

The nitrogen cycle pathways are responsible for the circulation of inorganic and organic N-containing molecules in nature. Among these pathways, those involving amino acids, N-oxides and in particular nitric oxide (NO) play strategic roles in the metabolism of microorganisms in natural environments and in host-pathogen interactions. Beyond their role in the N-cycle, amino acids and NO are also signalling molecules able to influence group behaviour in microorganisms and cell-cell communication in multicellular organisms, including humans. In this minireview, we summarise the role of these compounds in the homeostasis of the bacterial communities called biofilms, commonly found in environmental, industrial and medical settings. Biofilms are difficult to eradicate since they are highly resistant to antimicrobials and to the host immune system. We highlight the effect of amino acids such as glutamate, glutamine and arginine and of NO on the signalling pathways involved in the metabolism of 3',5'-cyclic diguanylic acid (c-di-GMP), a master regulator of motility, attachment and group behaviour in bacteria. The study of the metabolic routes involving these N-containing compounds represents an attractive topic to identify targets for biofilm control in both natural and medical settings.

Fractalkine Modulates Microglia Metabolism in Brain Ischemia

In the CNS, the chemokine CX3CL1 (fractalkine) is expressed on neurons while its specific receptor CX3CR1 is expressed on microglia and macrophages. Microglia play an important role in health and disease through CX3CL1/CX3CR1 signaling, and in many neurodegenerative disorders, microglia dysregulation has been associated with neuro-inflammation. We have previously shown that CX3CL1 has neuroprotective effects against cerebral ischemia injury. Here, we investigated the involvement of CX3CL1 in the modulation of microglia phenotype and the underlying neuroprotective effect on ischemia injury. The expression profiles of anti- and pro-inflammatory genes showed that CX3CL1 markedly inhibited microglial activation both in vitro and in vivo after permanent middle cerebral artery occlusion (pMCAO), accompanied by an increase in the expression of anti-inflammatory genes. Moreover, CX3CL1 induces a metabolic switch in microglial cells with an increase in the expression of genes related to the oxidative pathway and a reduction in those related to the glycolytic pathway, which is the metabolic state associated to the pro-inflammatory phenotype for energy production. The data reported in this paper suggest that CX3CL1 protects against cerebral ischemia modulating the activation state of microglia and its metabolism in order to restrain inflammation and organize a neuroprotective response against the ischemic insult.

A novel bacterial l-arginine sensor controlling c-di-GMP levels in Pseudomonas aeruginosa

Nutrients such as amino acids play key roles in shaping the metabolism of microorganisms in natural environments and in host-pathogen interactions. Beyond taking part to cellular metabolism and to protein synthesis, amino acids are also signaling molecules able to influence group behavior in microorganisms, such as biofilm formation. This lifestyle switch involves complex metabolic reprogramming controlled by local variation of the second messenger 3', 5'-cyclic diguanylic acid (c-di-GMP). The intracellular levels of this dinucleotide are finely tuned by the opposite activity of dedicated diguanylate cyclases (GGDEF signature) and phosphodiesterases (EAL and HD-GYP signatures), which are usually allosterically controlled by a plethora of environmental and metabolic clues. Among the genes putatively involved in controlling c-di-GMP levels in P. aeruginosa, we found that the multidomain transmembrane protein PA0575, bearing the tandem signature GGDEF-EAL, is an l-arginine sensor able to hydrolyse c-di-GMP. Here, we investigate the basis of arginine recognition by integrating bioinformatics, molecular biophysics and microbiology. Although the role of nutrients such as l-arginine in controlling the cellular fate in P. aeruginosa (including biofilm, pathogenicity and virulence) is already well established, we identified the first l-arginine sensor able to link environment sensing, c-di-GMP signaling and biofilm formation in this bacterium.

Insights into the GTP-dependent allosteric control of c-di-GMP hydrolysis from the crystal structure of PA0575 protein from Pseudomonas aeruginosa

Bis-(3'-5')-cyclic diguanylic acid (c-di-GMP) belongs to the class of cyclic dinucleotides, key carriers of cellular information in prokaryotic and eukaryotic signal transduction pathways. In bacteria, the intracellular levels of c-di-GMP and their complex physiological outputs are dynamically regulated by environmental and internal stimuli, which control the antagonistic activities of diguanylate cyclases (DGCs) and c-di-GMP specific phosphodiesterases (PDEs). Allostery is one of the major modulators of the c-di-GMP-dependent response. Both the c-di-GMP molecule and the proteins interacting with this second messenger are characterized by an extraordinary structural plasticity, which has to be taken into account when defining and possibly predicting c-di-GMP-related processes. Here, we report a structure-function relationship study on the catalytic portion of the PA0575 protein from Pseudomonas aeruginosa, bearing both putative DGC and PDE domains. The kinetic and structural studies indicate that the GGDEF-EAL portion is a GTP-dependent PDE. Moreover, the crystal structure confirms the high degree of conformational flexibility of this module. We combined structural analysis and protein engineering studies to propose the possible molecular mechanism guiding the nucleotide-dependent allosteric control of catalysis; we propose that the role exerted by GTP via the GGDEF domain is to allow the two EAL domains to form a dimer, the species competent to enter PDE catalysis.

The catalytic activity of serine hydroxymethyltransferase is essential for de novo nuclear dTMP synthesis in lung cancer cells

Cancer cells reprogramme one-carbon metabolism (OCM) to sustain growth and proliferation. Depending on cell demands, serine hydroxymethyltransferase (SHMT) dynamically changes the fluxes of OCM by reversibly converting serine and tetrahydrofolate (THF) into 5,10-methylene-THF and glycine. SHMT is a tetrameric enzyme that mainly exists in three isoforms; two localize in the cytosol (SHMT1/SHMT2α) and one (SHMT2) in the mitochondria. Both the cytosolic isoforms can also translocate to the nucleus to sustain de novo thymidylate synthesis and support cell proliferation. Finally, the expression levels of the different isoforms are regulated to a certain extent by a yet unknown crosstalk mechanism. We have designed and fully characterized a set of three SHMT1 mutants, which uncouple the oligomeric state of the enzyme from its catalytic activity. We have then investigated the effects of the mutations on SHMT1 nuclear localization, cell viability and crosstalk in lung cancer cells (A549; H1299). Our data reveal that in these cell lines de novo thymidylate synthesis requires SHMT1 to be active, regardless of its oligomeric state. We have also confirmed that the crosstalk between the cytosolic and mitochondrial SHMT actually takes place and regulates the expression of the two isoforms. Apparently, the crosstalk mechanism is independent from the oligomeric state and the catalytic activity of SHMT1.

DATABASE

Structural data are available in the PDB under the accession number 6FL5.

Differential inhibitory effect of a pyrazolopyran compound on human serine hydroxymethyltransferase-amino acid complexes

Serine hydroxymethyltransferase (SHMT) is a pivotal enzyme in one-carbon metabolism that catalyses the reversible conversion of serine and tetrahydrofolate into glycine and methylenetetrahydrofolate. It exists in cytosolic (SHMT1) and mitochondrial (SHMT2) isoforms. Research on one-carbon metabolism in cancer cell lines has shown that SHMT1 preferentially catalyses serine synthesis, whereas in mitochondria SHMT2 is involved in serine breakdown. Recent research has focused on the identification of inhibitors that bind at the folate pocket. We have previously found that a representative derivative of the pyrazolopyran scaffold, namely 2.12, inhibits both SHMT isoforms, with a preference for SHMT1, causing apoptosis in lung cancer cell lines. Here we show that the affinity of 2.12 for SHMT depends on the identity of the amino acid substrate bound to the enzyme. The dissociation constant of 2.12 is 50-fold lower when it binds to SHMT1 enzyme-serine complex, as compared to the enzyme-glycine complex. Evidence is presented for a similar behaviour of compound 2.12 in the cellular environment. These findings suggest that the presence and identity of the amino acid substrate should be considered when designing SHMT inhibitors. Moreover, our data provide the proof-of-concept that SHMT inhibitors selectively targeting the directionality of one-carbon metabolism flux could be designed.

Glucose Metabolism in the Progression of Prostate Cancer

Prostate cancer is one of the most common types of cancer in western country males but the mechanisms involved in the transformation processes have not been clearly elucidated. Alteration in cellular metabolism in cancer cells is recognized as a hallmark of malignant transformation, although it is becoming clear that the biological features of metabolic reprogramming not only differ in different cancers, but also among different cells in a type of cancer. Normal prostate epithelial cells have a peculiar and very inefficient energy metabolism as they use glucose to synthesize citrate that is secreted as part of the seminal liquid. During the transformation process, prostate cancer cells modify their energy metabolism from inefficient to highly efficient, often taking advantage of the interaction with other cell types in the tumor microenvironment that are corrupted to produce and secrete metabolic intermediates used by cancer cells in catabolic and anabolic processes. We recapitulate the metabolic transformations occurring in the prostate from the normal cell to the metastasis, highlighting the role of the microenvironment and summarizing what is known on the molecular mechanisms involved in the process.

A pyrazolopyran derivative preferentially inhibits the activity of human cytosolic serine hydroxymethyltransferase and induces cell death in lung cancer cells

Serine hydroxymethyltransferase (SHMT) is a central enzyme in the metabolic reprogramming of cancer cells, providing activated one-carbon units in the serine-glycine one-carbon metabolism. Previous studies demonstrated that the cytoplasmic isoform of SHMT (SHMT1) plays a relevant role in lung cancer. SHMT1 is overexpressed in lung cancer patients and NSCLC cell lines. Moreover, SHMT1 is required to maintain DNA integrity. Depletion in lung cancer cell lines causes cell cycle arrest and uracil accumulation and ultimately leads to apoptosis. We found that a pyrazolopyran compound, namely 2.12, preferentially inhibits SHMT1 compared to the mitochondrial counterpart SHMT2. Computational and crystallographic approaches suggest binding at the active site of SHMT1 and a competitive inhibition mechanism. A radio isotopic activity assay shows that inhibition of SHMT by 2.12 also occurs in living cells. Moreover, administration of 2.12 in A549 and H1299 lung cancer cell lines causes apoptosis at LD50 34 μM and rescue experiments underlined selectivity towards SHMT1. These data not only further highlight the relevance of the cytoplasmic isoform SHMT1 in lung cancer but, more importantly, demonstrate that, at least in vitro, it is possible to find selective inhibitors against one specific isoform of SHMT, a key target in metabolic reprogramming of many cancer types.

How pyridoxal 5'-phosphate differentially regulates human cytosolic and mitochondrial serine hydroxymethyltransferase oligomeric state

Adaptive metabolic reprogramming gives cancer cells a proliferative advantage. Tumour cells extensively use glycolysis to sustain anabolism and produce serine, which not only refuels the one-carbon units necessary for the synthesis of nucleotide precursors and for DNA methylation, but also affects the cellular redox homeostasis. Given its central role in serine metabolism, serine hydroxymethyltransferase (SHMT), a pyridoxal 5'-phosphate (PLP)-dependent enzyme, is an attractive target for tumour chemotherapy. In humans, the cytosolic isoform (SHMT1) and the mitochondrial isoform (SHMT2) have distinct cellular roles, but high sequence identity and comparable catalytic properties, which may complicate development of successful therapeutic strategies. Here, we investigated how binding of the cofactor PLP controls the oligomeric state of the human isoforms. The fact that eukaryotic SHMTs are tetrameric proteins while bacterial SHMTs function as dimers may suggest that the quaternary assembly in eukaryotes provides an advantage to fine-tune SHMT function and differentially regulate intertwined metabolic fluxes, and may provide a tool to address the specificity problem. We determined the crystal structure of SHMT2, and compared it to the apo-enzyme structure, showing that PLP binding triggers a disorder-to-order transition accompanied by a large rigid-body movement of the two cofactor-binding domains. Moreover, we demonstrated that SHMT1 exists in solution as a tetramer, both in the absence and presence of PLP, while SHMT2 undergoes a dimer-to-tetramer transition upon PLP binding. These findings indicate an unexpected structural difference between the two human SHMT isoforms, which opens new perspectives for understanding their differing behaviours, roles or regulation mechanisms in response to PLP availability in vivo.

Screening and in vitro testing of antifolate inhibitors of human cytosolic serine hydroxymethyltransferase

Metabolic reprogramming of tumor cells toward serine catabolism is now recognized as a hallmark of cancer. Serine hydroxymethyltransferase (SHMT), the enzyme providing one-carbon units by converting serine and tetrahydrofolate (H4 PteGlu) to glycine and 5,10-CH2 -H4 PteGlu, therefore represents a target of interest in developing new chemotherapeutic drugs. In this study, 13 folate analogues under clinical evaluation or in therapeutic use were in silico screened against SHMT, ultimately identifying four antifolate agents worthy of closer evaluation. The interaction mode of SHMT with these four antifolate drugs (lometrexol, nolatrexed, raltitrexed, and methotrexate) was assessed. The mechanism of SHMT inhibition by the selected antifolate agents was investigated in vitro using the human cytosolic isozyme. The results of this study showed that lometrexol competitively inhibits SHMT with inhibition constant (Ki ) values in the low micromolar. The binding mode of lometrexol to SHMT was further investigated by molecular docking. These results thus provide insights into the mechanism of action of antifolate drugs and constitute the basis for the rational design of novel and more potent inhibitors of SHMT.

An analysis of genetic factors related to risk of inflammatory bowel disease and colon cancer

BACKGROUND AND AIMS

Patients with inflammatory bowel disease (IBD) have a higher risk of developing colorectal cancer than the general population. Genome-wide association studies have identified and replicated several loci associated with risk of IBD; however, it is currently unknown whether these loci are also associated with colon cancer risk.

METHODS

We selected 15 validated SNPs associated with risk of either Crohn's disease, ulcerative colitis, or both in previous GWAS and tested whether these loci were also associated with colon cancer risk in a two-stage study design.

RESULTS

We found that rs744166 in STAT3 was associated with colon cancer risk in two studies; however, the direction of the observation was reversed in TP53 mutant tumors possibly due to a nullification of the effect by mutant p53. The SNP, which lies within intron 1 of the STAT3 gene, was associated with lower expression of STAT3 mRNA in TP53 wild-type, but not mutant, tumors.

CONCLUSIONS

These data suggest that the STAT3 locus is associated with both IBD and cancer. Further understanding the function of this variant in relation to TP53 could possibly explain the role of this gene in autoimmunity and cancer. Furthermore, an analysis of this locus, specifically in a population with IBD, could help to resolve the relationship between this SNP and cancer.

MicroRNA-135b promotes cancer progression by acting as a downstream effector of oncogenic pathways in colon cancer

MicroRNA deregulation is frequent in human colorectal cancers (CRCs), but little is known as to whether it represents a bystander event or actually drives tumor progression in vivo. We show that miR-135b overexpression is triggered in mice and humans by APC loss, PTEN/PI3K pathway deregulation, and SRC overexpression and promotes tumor transformation and progression. We show that miR-135b upregulation is common in sporadic and inflammatory bowel disease-associated human CRCs and correlates with tumor stage and poor clinical outcome. Inhibition of miR-135b in CRC mouse models reduces tumor growth by controlling genes involved in proliferation, invasion, and apoptosis. We identify miR-135b as a key downsteam effector of oncogenic pathways and a potential target for CRC treatment.

A new role for microRNAs, as ligands of Toll-like receptors

Tumor microenvironment plays a central role in the development and dissemination of cancer cells. In addition to study each specific cellular component of the microenvironment, it has become clear that it is the type and amount of information that cells exchange that ultimately affects cancer phenotype. Recently, it has been discovered that intercellular communication occurs through the release of microvesicles and exosomes, whose cargo represents the information released by one cell to a recipient cell. A key component of this cargo is represented by microRNAs (miRNAs), small non-coding RNAs with gene regulatory functions. We discovered that miRNAs released by cancer cells within microvesicles can reach and bind to Toll-like receptors (TLRs) in surrounding immune cells, and activate them in a paracrine loop. As a result, immune cells produce cytokines that increase cell proliferation and metastatic potential. This discovery provides the rationale for the development of new drugs that might be used in the treatment of cancer as well as other inflammation-related diseases.

Epigenetic regulation of miRNAs in cancer

MicroRNAs (miRNAs) are short noncoding RNAs with gene regulatory functions. It has been demonstrated that the genes encoding for miRNAs undergo the same regulatory epigenetic processes of protein coding genes. In turn, a specific subgroup of miRNAs, called epi-miRNAs, is able to directly target key enzymatic effectors of the epigenetic machinery (such as DNA methyltransferases, histone deacetylases, and polycomb genes), therefore indirectly affecting the expression of epigenetically regulated oncogenes and tumor suppressor genes. Also, several of the epigenetic drugs currently approved as anticancer agents affect the expression of miRNAs and this might explain part of their mechanism of action. This chapter focuses on the tight relationship between epigenetics and miRNAs and provides some insights on the translational implications of these findings, leading to the upcoming introduction of epigenetically related miRNAs in the treatment of cancer.

miR-EdiTar: a database of predicted A-to-I edited miRNA target sites

MOTIVATION

A-to-I RNA editing is an important mechanism that consists of the conversion of specific adenosines into inosines in RNA molecules. Its dysregulation has been associated to several human diseases including cancer. Recent work has demonstrated a role for A-to-I editing in microRNA (miRNA)-mediated gene expression regulation. In fact, edited forms of mature miRNAs can target sets of genes that differ from the targets of their unedited forms. The specific deamination of mRNAs can generate novel binding sites in addition to potentially altering existing ones.

RESULTS

This work presents miR-EdiTar, a database of predicted A-to-I edited miRNA binding sites. The database contains predicted miRNA binding sites that could be affected by A-to-I editing and sites that could become miRNA binding sites as a result of A-to-I editing.

AVAILABILITY

miR-EdiTar is freely available online at http://microrna.osumc.edu/mireditar.

CONTACT

alessandro.lagana@osumc.edu or carlo.croce@osumc.edu

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

rs4919510 in hsa-mir-608 is associated with outcome but not risk of colorectal cancer

BACKGROUND

Colorectal cancer is the third most incident cancer and cause of cancer-related death in the United States. MicroRNAs, a class of small non-coding RNAs, have been implicated in the pathogenesis and prognosis of colorectal cancer, although few studies have examined the relationship between germline mutation in the microRNAs with risk and prognosis. We therefore investigated the association between a SNP in hsa-mir-608, which lies within the 10q24 locus, and colorectal cancer.

METHODS AND RESULTS

A cohort consisting of 245 cases and 446 controls was genotyped for rs4919510. The frequency of the GG genotype was significantly higher in African Americans (15%) compared to Caucasians (3%) controls. There was no significant association between rs4919510 and colorectal cancer risk (African American: OR(GG vs. CC) 0.89 [95% CI, 0.41-1.80]) (Caucasian: OR(GG vs. CC) 1.76, ([95% CI, 0.48-6.39]). However, we did observe an association with survival. The GG genotype was associated with an increased risk of death in Caucasians (HR(GG vs. CC) 3.54 ([95% CI, 1.38-9.12]) and with a reduced risk of death in African Americans (HR(GG vs. CC) 0.36 ([95% CI 0.12-1.07).

CONCLUSIONS

These results suggest that rs4910510 may be associated with colorectal cancer survival in a manner that is dependent on race.

Anti-miR-135b in colon cancer treatment: Results from a preclinical study

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Background: MicroRNAs (miRs) are small non coding RNAs involved in cell homeostasis. miRs are deregulated in colorectal cancer (CRC). Our study aimed at identifying miRs with a driver role in carcinogenesis altered by similar mechanisms in both human and mouse CRC. Goal of the study was to use CRC mouse models for the pre-clinical development of anti-miRs as therapeutic drugs.

Methods: Azoximetane (AOM)/Dextran-Sulfate (DSS) treated mice or CDX2-CRE/APC-/- mice were used to study inflammation-associated and sporadic APC-related CRC. Human Inflammatory Bowel Disease associated (n=30), and sporadic (n=90) CRC with their matched normal tissues were collected according to Good Clinical Practice recommendation and subjected to RNA extraction using Trizol. miR and gene expression profiling was assessed by nCounter technology (Nanostring Seattle). Anti-miR-135b and scrambled probes for in vivo studies were synthesized by Girindus.

Results: miRs profiling from AOM/DSS and CDX2-CRE/APC-/- CRC. revealed that miR-135b is one of the most up-regulated miRs in both models. In humans miR-135b over-expression was found in both IBD and sporadic CRC and was associated with reduced Progression Free Survival and Overall Survival in CRC patients. Molecular studies in Mouse Embryo Fibroblast and human CRC cell lines highlighted the role of two major pathways in the upstream activation of miR-135b: APC-β-Catenin and SRC-PI3K. MiR-135b up-regulation resulted in reduced apoptosis and increased invasion and metastasis due to the down-regulation of TGFRB2, DAPK1, APC and HIF1AN. Silencing of miR-135b in vivo reduced tumor multiplicity and tumor load in the AOM/DSS CRC model. Mice treated with anti-miR-135b showed well differentiated tumors and microacinar pattern while tumors in the control groups showed low differentiation and adenomatous pattern.

Conclusions: Our data suggest that miR-135b is a key molecule whose activation is downstream of oncogenes and oncosuppressor genes frequently altered in CRC. Our study defines specific pathways that converge on the activation of the same microrna. The “in vivo” silencing of miR-135 shows preclinical efficacy with low toxicity and represents the first in vivo study for the use of antimiRs in CRC treatment.

Abstract B14: Anti-miR-135b in colon cancer treatment

Background: MicroRNAs (miRs) are small non coding RNAs involved in cell homeostasis. miRs are deregulated in colorectal cancer (CRC). Our study aimed at identifying miRs with a driver role in carcinogenesis altered by similar mechanisms in both human and mouse CRC. Goal of the study was to use CRC mouse models for the pre-clinical development of anti-miRs as therapeutic drugs. Methods: Azoximetane (AOM)/Dextran-Sulfate (DSS) treated mice or CDX2Cre-APC f/wt mice were used to study inflammation-associated and sporadic APC-related CRC. Human Inflammatory Bowel Disease associated (n=30), and sporadic (n=90) CRC with their matched normal tissues were collected according to Good Clinical Practice recommendation and subjected to RNA extraction using Trizol. miR and gene expression profiling was assessed by nCounter technology (Nanostring Seattle). AntimiR-135b and scrambled probes for in vivo studies were synthesized by Girindus. Results: miRs profiling from AOM/DSS and CDX2Cre-APC f/wt CRC. revealed that miR-135b is one of the most up-regulated miRs in both models. In humans miR-135b over-expression was found in both IBD and sporadic CRC and was associated with reduced Progression Free Survival and Overall Survival in CRC patients. Molecular studies in Mouse Embryo Fibroblast and human CRC cell lines highlighted the role of two major pathways in the upstream activation of miR-135b: APC-β-Catenin and SRC-PI3K. MiR-135b up-regulation resulted in reduced apoptosis and increased invasion and metastasis due to the down-regulation of TGFRB2, DAPK1, APC and HIF1AN. Silencing of miR-135b in vivo reduced tumor multiplicity and tumor load in the AOM/DSS CRC model. Mice treated with anti-miR-135b showed well differentiated tumors and acinar pattern while tumors in the control groups showed low differentiation and adenomatous pattern. Conclusions: Our data suggest that miR-135b is a key molecule whose activation is downstream of oncogenes and oncosuppressor genes frequently altered in CRC. Our study defines specific pathways that converge on the activation of the same microrna. The “in vivo” silencing of miR-135 shows preclinical efficacy with low toxicity and represents the first in vivo study for the use of antimiRs in CRC treatment

Note: This abstract was not presented at the conference because the presenter was unable to attend.

Citation Format: Nicola Valeri, Roberta Gafa', Gerard Nuovo, Giovanni Lanza, Wendy Frankel, Peter K. Vogt, Joanna Groden, Michael Karin, Carlo M. Croce, Chiara Braconi, Pierluigi Gasparini, Sergei Grivennikov, Jonathan R. Hart, Alessio Paone, Francesca Lovat, Muller Fabbri. Anti-miR-135b in colon cancer treatment [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer; 2012 Jan 8-11; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(2 Suppl):Abstract nr B14.

MicroRNAs as New Characters in the Plot between Epigenetics and Prostate Cancer

Prostate cancer (PCA) still represents a leading cause of death. An increasing number of studies have documented that microRNAs (miRNAs), a subgroup of non-coding RNAs with gene regulatory functions, are differentially expressed in PCA respect to the normal tissue counterpart, suggesting their involvement in prostate carcinogenesis and dissemination. Interestingly, it has been shown that miRNAs undergo the same regulatory mechanisms than any other protein coding gene, including epigenetic regulation. In turn, miRNAs can also affect the expression of oncogenes and tumor suppressor genes by targeting effectors of the epigenetic machinery, therefore indirectly affecting the epigenetic controls on these genes. Among the genes that undergo this complex regulation, there is the androgen receptor (AR), a key therapeutic target for PCA. This review will focus on the role of epigenetically regulated and epigenetically regulating miRNAs in PCA and on the fine regulation of AR expression, as mediated by this miRNA–epigenetics interaction.

Effect of miR-21 on resistance to 5-fluorouracil and regulation of MSH2

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Background: MicroRNAs are small non coding RNAs controlling cell homeostasis. Defects in mismatch repair (MMR) genes cause resistance to 5-fluorouracil (5FU). miR-21 is up-regulated in colorectal cancer (CRC) and is associated with poor benefit from adjuvant 5FU. We aimed at studying if miR-21 may induce 5FU resistance by down-regulating MSH2.

Methods: Fresh frozen (32) and paraffin-embedded (50) cases of CRC and matched normal tissues were studied for miR-21 expression (Northern Blotting and in situ Hybridization) and MSH2 expression (Western Blotting and Immunohistochemistry). CRC Colo-320DM, SW620 and isogenic Lovo cells with [Lovo(MSH2+)] and without MSH2 [Lovo(MSH2-)] were used. Pre-miR-21 was used for over-expression experiments. Luciferase vectors with MSH2 (Luc-MSH2) and MSH6 (Luc-MSH6) 3'UTRs downstream of the Luciferase gene were used. Cell cycle modifications after 5FU (10uM) were assessed by FACS analysis. Lentiviral vectors encoding for miR-21 or siRNA to MSH2 or empty vectors were used for stable infection. Stable clones were injected in the flank of nude mice. Mice were treated with 5FU i.p. for 2 weeks. Tumor volume was measured once a week and calculated according to the formula Volume=LxW2/2.

Results: A statistically significant inverse correlation between miR-21 and MSH2 expression was observed by Parson's test in the two CRC cohorts. miR-21 over-expression caused reduction in MSH2 and MSH6 protein expression and in Luciferase activity after transfection with Luc-MSH2 or Luc-MSH6 vectors confirming that miR-21 directly regulates MSH2 and MSH6. miR-21 up-regulation reduced 5FU induced apoptosis and G2/M arrest at the same extent of siRNA to MSH2 in all MMR proficient cells while no significant effect was observed in Lovo(MSH2-). Complementation experiments with plasmid encoding for MSH2 promoted 5FU induced apoptosis that was inhibited by co-transfection with miR-21. Xenograft tumors over-expressing miR-21 or siRNA anti MSH2 achieved the same response to 5FU and both showed to be less responsive to 5FU than controls.

Conclusions: miR-21 causes resistance to 5FU in a MSH2 dependent manner and might be a useful marker in predicting therapeutic outcome in CRC patients.

No significant financial relationships to disclose.

TLR stimulation of prostate tumor cells induces chemokine-mediated recruitment of specific immune cell types

TLRs boost antimicrobial response mechanisms by epithelial cells and represent the first line of defense at mucosal sites. In view of these immunomodulatory properties, TLR stimulation may represent a novel means to activate anticancer immune responses. In the present study, the ability of TLR ligands to affect the recruitment of different immune cell populations by human prostate cancer cell lines and the underlying mechanisms were investigated. We showed that LNCaP and DU-145 cells express functionally active TLR3 and TLR5. Treatment with their respective agonists, polyinosinic:polycytidylic acid and flagellin, rapidly triggered NF-kappaB-dependent upregulation of different inflammatory molecules, as assayed by microarray and ELISA. Furthermore, we demonstrated that conditioned media from polyinosinic:polycytidylic acid- and flagellin-treated LNCaP and DU-145 cells induced the recruitment of different leukocyte subpopulations, suggesting that TLR stimulation is able to activate the earliest step of immune response mediated by soluble factors. Interestingly, the more aggressive cancer cell line PC3 expressed TLR3 and TLR5 but failed to respond to TLR agonists in terms of NF-kappaB activation and the ability to attract immune effectors. Overall, these data show for the first time that TLR3 and TLR5 stimulation of human prostate cancer cells triggers the production of chemokines, which, in turn, favor the attraction of immune effectors, thereby representing a tool to enhance the efficacy of conventional therapies by stimulating anticancer immune responses.

Toll-like receptor 3 activation induces antiviral immune responses in mouse sertoli cells

Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns and elicit antimicrobial immune responses. In the testis, viruses can induce pathological conditions, such as orchitis, and may participate in the etiology of testicular cancer; however, the molecular mechanisms involved remain under investigation. It has been suggested that because they constitutively express interferon (IFN)-inducible antiviral proteins, Sertoli cells participate in the testicular antiviral defense system. Previously, we demonstrated a key function of mouse Sertoli cells in the bactericidal testicular defense mechanism mediated by a panel of TLRs. To better characterize the potential role of Sertoli cells in the response against testicular viral infections, we investigated the TLR3 expression and function in these cells. Sertoli cells express TLR3, and under stimulation with the synthetic double-stranded RNA analogue poly (I:C), they produce the proinflammatory molecule ICAM1 and secrete functionally active CCL2 chemokine. Using both pharmacological and genetic approaches, we found that these effects are TLR3-dependent. Moreover, using ELISA, we found that IFNA is constitutively produced and not further inducible, whereas IFNB1 is absent and dramatically induced only by transfected poly (I:C), indicating different control mechanisms underlying IFNA and IFNB1 production. To conclude, poly (I:C) elicits both inflammatory and antiviral responses in Sertoli cells.

Toll-like receptor 3 triggers apoptosis of human prostate cancer cells through a PKC-alpha-dependent mechanism

Toll-like receptors (TLRs) are known to play a key role in the innate immune system particularly in inflammatory response against invading pathogens. Recent reports strongly indicate that they play important roles in cancer cells. Prostate cancer represents one of the most common cancer for which no cure is available once metastatic and androgen refractory. Since TLR3 has been recently suggested as a possible therapeutic target in some cancer cell lines, we studied TLR3 expression and functionality in two human prostate cancer cell lines, LNCaP and PC3. We report that both cell lines express TLR3 and that the TLR3 agonist poly (I:C) activates mitogen-activated protein kinases and induces inhibition of proliferation as well as caspase-dependent apoptosis. By using pharmacological and genetic approaches, we demonstrate the involvement of TLR3 in poly (I:C)-induced effects. We also show that a novel interferon-independent pathway involving protein kinase C (PKC)-alpha activation, upstream of p38 and c-jun N-terminal kinase, is responsible for poly (I:C) pro-apoptotic effects on LNCaP cells. To our knowledge, this is the first report describing a role of PKC-alpha in poly (I:C)-mediated apoptosis. The comprehension of the mechanisms underlying TLR3-mediated apoptosis can contribute tools to develop new agonists useful for the treatment of prostate cancer.

c-Flip(L) is expressed in undifferentiated mouse male germ cells

Apoptosis represents a fundamental process during fetal/post-natal testis development. Therefore pro- and anti-apoptotic proteins are essential to regulate testis physiology. c-Flip(L) is a known inhibitor of caspase 8/10 activity; in this study its perinatal expression in mouse male germ cells was investigated. In testis sections and seminiferous tubule whole mount c-Flip(L) was found to be expressed in undifferentiated spermatogonia and to co-localize with germ stem cells markers. In vivo investigations in the vitamin-A deficient mouse, lacking differentiated germ cells, confirmed c-Flip(L) expression in undifferentiated spermatogonia. Further analyses showed Fas expression but no significant caspase 8/10 activity when c-Flip(L) was highly expressed. Altogether these data suggest that c-Flip may control the survival rate of undifferentiated spermatogonia.

c-Flip expression and function in fetal mouse gonocytes

Apoptosis is a key mechanism in spermatogenesis, and in testis, most gonocytes degenerate at fetal and postnatal ages to select a cell subset committed to become germ stem cells. The aim of the present study is to investigate mechanisms controlling the massive apoptosis of fetal gonocytes. We evaluated the expression and function of c-Flip, an apoptosis inhibitor known to interfere with the proapoptotic Fas-signaling pathway in a variety of cell types, but never investigated in fetal testis. Expression of c-Flip long isoform (c-FlipL) within fetal testis was localized in gonocytes at 16.5 and 18.5 days post coitum (dpc), both at the mRNA and protein level, while it was weakly expressed or undetectable at earlier stages. Moreover, Fas protein was found in fetal testes at 13.5, 16.5, and 18.5 dpc. Testes at 18.5 dpc, expressing high levels of c-FlipL, were resistant to Fas-induced apoptosis while they became highly sensitive when c-FlipL was inhibited by antisense c-Flip oligos. In addition, there was an inverse relation between gonocyte spontaneous apoptosis sensitivity and c-FlipL levels. Furthermore, caspase-10 activity was inversely related with c-FlipL expression, suggesting that caspase-10 might be a target of c-FlipL. These data represent the first evidence demonstrating c-Flip expression in fetal testes and its role in protecting gonocytes from Fas-dependent apoptosis.

Ureteral occlusion prosthesis

Although temporary or definitive complete ureteral occlusion is rarely needed, there is a considerable number of reports introducing different devices to achieve this goal, most of which can be inserted with minimally invasive procedures. Easy placement is considered of paramount importance, as the candidates are very often in bad general condition as a result of previous surgery, radiotherapy, or other palliative treatments for cancer. A device that can be inserted and removed percutaneously is presented herein. It can be employed in cases of ureteral fistulas resulting from radiotherapy and ureterosigmoidostomy with good results. The technique is simple and not time consuming.

Induction of mutations in V79-4 mammalian cells under hypoxic and aerobic conditions by the cytotoxic 2-nitroimidazole-aziridines, RSU-1069 and RSU-1131. The influence of cellular glutathione

Incubation of the 2-nitroimidazole-aziridine, RSU-1069 [1-(2-nitro-1-imidazolyl)-3-(1-aziridinyl)-2-propanol], and its monomethylaziridine analogue, RSU-1131 [1-(2-nitro-1-imidazolyl)-3-(1-(2-methylaziridinyl))-2-propanol], with V79-4 mammalian cells for 2 hr under aerobic or hypoxic conditions induces mutations as measured at the hypoxanthine phosphoribosyl transferase locus. The ability of these agents to induce mutations is increased by a factor of 12-14 under hypoxic conditions. The increased cytotoxicity of these agents under hypoxic conditions was confirmed following a 2 hr incubation period. Decreasing the glutathione (GSH) content of the cells with buthionine-(S,R)-sulphoximine to < 1% of the control generally results in an increase in the cytotoxicity and mutagenicity of these agents under both aerobic and hypoxic conditions. Since these agents do not modify the cellular GSH levels, it is inferred that the thiols partially detoxify through removal of a reactive metabolite of the agents, under hypoxic conditions, or removal of known DNA adducts, and not through their interaction with the agents themselves. Under aerobic conditions, the formation of mutations is consistent with the established monofunctional action of these agents whereas under hypoxic conditions the bifunctional action predominates for mutation induction, based upon the large differential aerobic:hypoxic effect. From a comparison of the number of mutations per lethal event, the effect of thiol depletion is more pronounced for cytotoxicity than for mutation induction by these agents. In summary, these agents are considered to be weak mutagens towards V79-4 cells under aerobic conditions when compared with other DNA alkylating agents, although they are more potent under anoxic conditions.