Activity of pyridyl-pyrazolone derivatives against Trypanosoma cruzi.

New affordable drugs are needed for the treatment of infection with the protozoan parasite Trypanosoma cruzi responsible for the Chagas disease (CD). Only two old drugs are currently available, nifurtimox and benznidazole (Bz) but they exhibit unwanted side effects and display a weak activity in the late chronic phase of the disease. In this context, we evaluated the activity of a series of aryl-pyrazolone derivatives against T cruzi, using both bloodstream trypomastigote and intracellular amastigote forms of the parasite. The test compounds originate from a series of anticancer agents targeting the immune checkpoint ligand PD-L1 and bear an analogy with known anti-trypanosomal pyrazolones. A first group of 6 phenyl-pyrazolones was tested, revealing the activity of a single pyridyl-pyrazolone derivative. Then a second group of 8 compounds with a common pyridyl-pyrazolone core was evaluated. The in vitro testing process led to the identification of two non-cytotoxic and highly potent molecules against the intracellular form of T. cruzi, with an activity comparable to Bz. Moreover, one compound revealed an activity largely superior to that of Bz against bloodstream trypomastigotes, while being non-cytotoxic (selectivity index >1000). Unfortunately, the compound showed little activity in vivo, most likely due to its very limited plasma stability. However, the study opens novel perspectives for the design of new anti-trypanosomal products and the mechanism of action of the compounds is discussed.

MYC dependency in GLS1 and NAMPT is a therapeutic vulnerability in multiple myeloma.

Multiple myeloma (MM) is an incurable hematological malignancy in which MYC alterations contribute to the malignant phenotype. Nevertheless, MYC lacks therapeutic druggability. Here, we leveraged large-scale loss-of-function screens and conducted a small molecule screen to identify genes and pathways with enhanced essentiality correlated with MYC expression. We reported a specific gene dependency in glutaminase (GLS1), essential for the viability and proliferation of MYC overexpressing cells. Conversely, the analysis of isogenic models, as well as cell lines dataset (CCLE) and patient datasets, revealed GLS1 as a non-oncogenic dependency in MYC-driven cells. We functionally delineated the differential modulation of glutamine to maintain mitochondrial function and cellular biosynthesis in MYC overexpressing cells. Furthermore, we observed that pharmaceutical inhibition of NAMPT selectively affects MYC upregulated cells. We demonstrate the effectiveness of combining GLS1 and NAMPT inhibitors, suggesting that targeting glutaminolysis and NAD synthesis may be a promising strategy to target MYC-driven MM.

Novel PD-L1-Targeted Phenyl-Pyrazolone Derivatives with Antioxidant Properties.

Orally-active anticancer small molecules targeting the PD-1/PD-L1 immune checkpoint are actively searched. Phenyl-pyrazolone derivatives with a high affinity for PD-L1 have been designed and characterized. In addition, the phenyl-pyrazolone unit acts as a scavenger of oxygen free radicals, providing antioxidant effects. The mechanism is known for the drug edaravone (1) which is also an aldehyde-reactive molecule. The present study reports the synthesis and functional characterization of new molecules (2-5) with an improved anti-PD-L1 activity. The leading fluorinated molecule 5 emerges as a potent checkpoint inhibitor, avidly binding to PD-L1, inducing its dimerization, blocking PD-1/PD-L1 signaling mediated by phosphatase SHP-2 and reactivating the proliferation of CTLL-2 cells in the presence of PD-L1. In parallel, the compound maintains a significant antioxidant activity, characterized using electron paramagnetic resonance (EPR)-based free radical scavenging assays with the probes DPPH and DMPO. The aldehyde reactivity of the molecules was investigated using 4-hydroxynonenal (4-HNE), which is a major lipid peroxidation product. The formation of drug-HNE adducts, monitored by high resolution mass spectrometry (HRMS), was clearly identified and compared for each compound. The study leads to the selection of compound 5 and the dichlorophenyl-pyrazolone unit as a scaffold for the design of small molecule PD-L1 inhibitors endowed with antioxidant properties.

Targeting of Tetraspanin CD81 with Monoclonal Antibodies and Small Molecules to Combat Cancers and Viral Diseases.

Tetraspanin CD81 plays major roles in cell-cell interactions and the regulation of cellular trafficking. This cholesterol-embarking transmembrane protein is a co-receptor for several viruses, including HCV, HIV-1 and Chikungunya virus, which exploits the large extracellular loop EC2 for cell entry. CD81 is also an anticancer target implicated in cancer cell proliferation and mobility, and in tumor metastasis. CD81 signaling contributes to the development of solid tumors (notably colorectal, liver and gastric cancers) and has been implicated in the aggressivity of B-cell lymphomas. A variety of protein partners can interact with CD81, either to regulate attachment and uptake of viruses (HCV E2, claudin-1, IFIM1) or to contribute to tumor growth and dissemination (CD19, CD44, EWI-2). CD81-protein interactions can be modulated with molecules targeting the extracellular domain of CD81, investigated as antiviral and/or anticancer agents. Several monoclonal antibodies anti-CD81 have been developed, notably mAb 5A6 active against invasion and metastasis of triple-negative breast cancer cells. CD81-EC2 can also be targeted with natural products (trachelogenin and harzianoic acids A-B) and synthetic compounds (such as benzothiazole-quinoline derivatives). They are weak CD81 binders but offer templates for the design of new compounds targeting the open EC2 loop. There is no anti-CD81 compound in clinical development at present, but this structurally well-characterized tetraspanin warrants more substantial considerations as a drug target.

A Potential Off-Target Effect of the Wnt/ß-Catenin Inhibitor KYA1797K: PD-L1 Binding and Checkpoint Inhibition.

Introduction: The quest for small molecule inhibitors of the PD-1/PD-L1 checkpoint continues in parallel to the extensive development of monoclonal antibodies directed against this immune checkpoint. Drug screening strategies are being set up to identify novel PD-L1 inhibitors. Methods: A virtual screening based on molecular docking with the PD-L1 protein dimer has been performed to identify a new binder. Binding of the identified ligand to PD-L1 has been validated experimentally using a microscale thermophoresis (MST) assay. The cellular effect of the compound was evidenced using a fluorescence resonance energy transfer (FRET) assay based on activation of tyrosine phosphatase SHP-2. Results: We have identified the potent Wnt/ß-catenin inhibitor KYA1797K as a weak PD-L1 binder. Molecular docking suggested that the compound can bind to the interface of a PD-L1 dimer, with a geometry superimposable to that of the reference PD-L1 inhibitor BMS-202. The atypical 2-thioxo-4-thiazolidinone motif of KYA1797K, derived from the natural product rhodanine, plays a major role in the interaction with PD-L1. Binding of KYA1797K to recombinant hPD-L1 was validated experimentally, using MST. The drug was found to bind modestly but effectively to hPD-L1. The FRET assay confirmed the weak capacity of KYA1797K to interfere with the activation of SHP-2 upon its interaction with human PD-1. Discussion: Collectively, the data show that KYA1797K could function as a weak modulator of the PD-1/PD-L1 checkpoint. This effect may contribute, at least partially, to the reported capacity of the ß-catenin inhibitor to downregulate PD-L1 in cancer cells. The work also underlines the interest to further consider the rhodanine moiety as a chemical motif for the design of new PD-L1 binders.

Soluble TIM-3 as a biomarker of progression and therapeutic response in cancers and other of human diseases.

Immune checkpoints inhibition is a privileged approach to combat cancers and other human diseases. The TIM-3 (T cell immunoglobulin and mucin-domain containing-3) inhibitory checkpoint expressed on different types of immune cells is actively investigated as an anticancer target, with a dozen of monoclonal antibodies in (pre)clinical development. A soluble form sTIM-3 can be found in the plasma of patients with cancer and other diseases. This active circulating protein originates from the proteolytic cleavage by two ADAM metalloproteases of the membrane receptor shared by tumor and non-tumor cells, and extracellular vesicles. In most cancers but not all, overexpression of mTIM-3 at the cell surface leads to high level of sTIM-3. Similarly, elevated levels of sTIM-3 have been reported in chronic autoimmune diseases, inflammatory gastro-intestinal diseases, certain viral and parasitic diseases, but also in cases of organ transplantation and in pregnancy-related pathologies. We have analyzed the origin of sTIM-3, its methods of dosage in blood or plasma, its presence in multiple diseases and its potential role as a biomarker to follow disease progression and/or the treatment response. In contrast to sPD-L1 generated by different classes of proteases and by alternative splicing, sTIM-3 is uniquely produced upon ADAM-dependent shedding, providing a more homogenous molecular entity and a possibly more reliable molecular marker. However, the biological functionality of sTIM-3 remains insufficiently characterized. The review shed light on pathologies associated with an altered expression of sTIM-3 in human plasma and the possibility to use sTIM-3 as a diagnostic or therapeutic marker.

IL-2 is inactivated by the acidic pH environment of tumors enabling engineering of a pH-selective mutein.

Cytokines interact with their receptors in the extracellular space to control immune responses. How the physicochemical properties of the extracellular space influence cytokine signaling is incompletely elucidated. Here, we show that the activity of interleukin-2 (IL-2), a cytokine critical to T cell immunity, is profoundly affected by pH, limiting IL-2 signaling within the acidic environment of tumors. Generation of lactic acid by tumors limits STAT5 activation, effector differentiation, and antitumor immunity by CD8+ T cells and renders high-dose IL-2 therapy poorly effective. Directed evolution enabled selection of a pH-selective IL-2 mutein (Switch-2). Switch-2 binds the IL-2 receptor subunit IL-2Rα with higher affinity, triggers STAT5 activation, and drives CD8+ T cell effector function more potently at acidic pH than at neutral pH. Consequently, high-dose Switch-2 therapy induces potent immune activation and tumor rejection with reduced on-target toxicity in normal tissues. Last, we show that sensitivity to pH is a generalizable property of a diverse range of cytokines with broad relevance to immunity and immunotherapy in healthy and diseased tissues.

Drug Repurposing to Enhance Antitumor Response to PD-1/PD-L1 Immune Checkpoint Inhibitors.

Monoclonal antibodies targeting the PD-1/PD-L1 immune checkpoint have considerably improved the treatment of some cancers, but novel drugs, new combinations, and treatment modalities are needed to reinvigorate immunosurveillance in immune-refractory tumors. An option to elicit antitumor immunity against cancer consists of using approved and marketed drugs known for their capacity to modulate the expression and functioning of the PD-1/PD-L1 checkpoint. Here, we have reviewed several types of drugs known to alter the checkpoint, either directly via the blockade of PD-L1 or indirectly via an action on upstream effectors (such as STAT3) to suppress PD-L1 transcription or to induce its proteasomal degradation. Specifically, the repositioning of the approved drugs liothyronine, azelnidipine (and related dihydropyridine calcium channel blockers), niclosamide, albendazole/flubendazole, and a few other modulators of the PD-1/PD-L1 checkpoint (repaglinide, pimozide, fenofibrate, lonazolac, propranolol) is presented. Their capacity to bind to PD-L1 or to repress its expression and function offer novel perspectives for combination with PD-1 targeted biotherapeutics. These known and affordable drugs could be useful to improve the therapy of cancer.

Antioxidant Properties and Aldehyde Reactivity of PD-L1 Targeted Aryl-Pyrazolone Anticancer Agents.

Small molecules targeting the PD-1/PD-L1 checkpoint are actively searched to complement the anticancer arsenal. Different molecular scaffolds have been reported, including phenyl-pyrazolone derivatives which potently inhibit binding of PD-L1 to PD-1. These molecules are structurally close to antioxidant drug edaravone (EDA) used to treat amyotrophic lateral sclerosis. For this reason, we investigated the capacity of five PD-L1-binding phenyl-pyrazolone compounds (1-5) to scavenge the formation of oxygen free radicals using electron spin resonance spectroscopy with DPPH/DMPO probes. In addition, the reactivity of the compounds toward the oxidized base 5-formyluracil (5fU) was assessed using chromatography coupled to mass spectrometry and photodiode array detectors. The data revealed that the phenyl-pyrazolone derivatives display antioxidant properties and exhibit a variable reactivity toward 5fU. Compound 2 with a N-dichlorophenyl-pyrazolone moiety cumulates the three properties, being a potent PD-L1 binder, a robust antioxidant and an aldehyde-reactive compound. On the opposite, the adamantane derivative 5 is a potent PD-L1 binding with a reduced antioxidant potential and no aldehyde reactivity. The nature of the substituent on the phenyl-pyrazolone core modulates the antioxidant capacity and reactivity toward aromatic aldehydes. The molecular signature of the compound can be adapted at will, to confer additional properties to these PD-L1 binders.

Pyrazolones as inhibitors of immune checkpoint blocking the PD-1/PD-L1 interaction.

Immuno-therapy has become a leading strategy to fight cancer. Over the past few years, immuno-therapies using checkpoint inhibitor monoclonal antibodies (mAbs) against programmed death receptor 1 (PD-1) and programmed death ligand 1 (PD-L1) have demonstrated improved survival compared with chemotherapy. We describe the microwave-assisted synthesis and the characterization of an innovative series of synthetic compounds endowed with nanomolar activity against PD-L1. The properties of the compounds were characterized using several biophysical techniques including microscale thermophoresis (MST) and fluorescence resonance energy transfer (FRET) measurements. A few small molecules demonstrated a high affinity for human PD-L1, potently disrupted the PD-L1:PD-1 interaction and inhibited Src homology region 2 domain-containing phosphatase (SHP2) recruitment to PD-1. More than 30 molecules from the pyrazolone family have been synthesized and 5 highly potent "PD-L1 silencing compounds" have been identified, based on in vitro measurements. Structure-activity relationships have been defined and ADME properties were evaluated. The phenyl-pyrazolone unit offers novel perspectives to design PD-L1-targeting agents, potentially useful to combat cancer and other pathologies implicating the PD-1/PD-L1 checkpoint.

Direct interaction of TrkA/CD44v3 is essential for NGF-promoted aggressiveness of breast cancer cells.

BACKGROUND: CD44 is a multifunctional membrane glycoprotein. Through its heparan sulfate chain, CD44 presents growth factors to their receptors. We have shown that CD44 and Tropomyosin kinase A (TrkA) form a complex following nerve growth factor (NGF) induction. Our study aimed to understand how CD44 and TrkA interact and the consequences of inhibiting this interaction regarding the pro-tumoral effect of NGF in breast cancer. METHODS: After determining which CD44 isoforms (variants) are involved in forming the TrkA/CD44 complex using proximity ligation assays, we investigated the molecular determinants of this interaction. By molecular modeling, we isolated the amino acids involved and confirmed their involvement using mutations. A CD44v3 mimetic peptide was then synthesized to block the TrkA/CD44v3 interaction. The effects of this peptide on the growth, migration and invasion of xenografted triple-negative breast cancer cells were assessed. Finally, we investigated the correlations between the expression of the TrkA/CD44v3 complex in tumors and histo-pronostic parameters. RESULTS: We demonstrated that isoform v3 (CD44v3), but not v6, binds to TrkA in response to NGF stimulation. The final 10 amino acids of exon v3 and the TrkA H112 residue are necessary for the association of CD44v3 with TrkA. Functionally, the CD44v3 mimetic peptide impairs not only NGF-induced RhoA activation, clonogenicity, and migration/invasion of breast cancer cells in vitro but also tumor growth and metastasis in a xenograft mouse model. We also detected TrkA/CD44v3 only in cancerous cells, not in normal adjacent tissues. CONCLUSION: Collectively, our results suggest that blocking the CD44v3/TrkA interaction can be a new therapeutic option for triple-negative breast cancers.

p65/RelA NF-κB fragments generated by RIPK3 activity regulate tumorigenicity, cell metabolism, and stemness characteristics.

Receptor-interacting protein kinase 3 (RIPK3) can induce necroptosis, apoptosis, or cell proliferation and is silenced in several hematological malignancies. We previously reported that RIPK3 activity independent of its kinase domain induces caspase-mediated p65/RelA cleavage, resulting in N-terminal 1-361 and C-terminal 362-549 fragments. We show here that a noncleavable p65/RelA D361E mutant expressed in DA1-3b leukemia cells decreases mouse survival times and that coexpression of p65/RelA fragments increases the tumorigenicity of B16F1 melanoma cells. This aggressiveness in vivo did not correlate with NF-κB activity measured in vitro. The fragments and p65/RelA D361E mutant induced different expression profiles in DA1-3b and B16F1 cells. Stemness markers were affected: p65/RelA D361E increased ALDH activity in DA1-3b cells, and fragment expression increased melanoma sphere formation in B16/F1 cells. p65/RelA fragments and the D361E noncleavable mutant decreased oxidative or glycolytic cell metabolism, with differences observed between models. Thus, p65/RelA cleavage initiated by kinase-independent RIPK3 activity in cancer cells is not neutral and induces pleiotropic effects in vitro and in vivo that may vary across tumor types.

Modulation of the Gal-9/TIM-3 Immune Checkpoint with α-Lactose. Does Anomery of Lactose Matter?

The disaccharide lactose is an excipient commonly used in pharmaceutical products. The two anomers, α- and ß-lactose (α-L/ß-L), differ by the orientation of the C-1 hydroxyl group on the glucose unit. In aqueous solution, a mutarotation process leads to an equilibrium of about 40% α-L and 60% ß-L at room temperature. Beyond a pharmaceutical excipient in solid products, α-L has immuno-modulatory effects and functions as a major regulator of TIM-3/Gal-9 immune checkpoint, through direct binding to the ß-galactoside-binding lectin galectin-9. The blockade of the co-inhibitory checkpoint TIM-3 expressed on T cells with anti-TIM-3 antibodies represents a promising approach to combat different onco-hematological diseases, in particular myelodysplastic syndromes and acute myeloid leukemia. In parallel, the discovery and development of anti-TIM-3 small molecule ligands is emerging, including peptides, RNA aptamers and a few specifically designed heterocyclic molecules. An alternative option consists of targeting the different ligands of TIM-3, notably Gal-9 recognized by α-lactose. Modulation of the TIM-3/Gal-9 checkpoint can be achieved with both α- and ß-lactose. Moreover, lactose is a quasi-pan-galectin ligand, capable of modulating the functions of most of the 16 galectin molecules. The present review provides a complete analysis of the pharmaceutical and galectin-related biological functions of (α/ß)-lactose. A focus is made on the capacity of lactose and Gal-9 to modulate both the TIM-3/Gal-9 and PD-1/PD-L1 immune checkpoints in oncology. Modulation of the TIM-3/Gal-9 checkpoint is a promising approach for the treatment of cancers and the role of lactose in this context is discussed. The review highlights the immuno-regulatory functions of lactose, and the benefit of the molecule well beyond its use as a pharmaceutical excipient.

Tau Stabilizes Chromatin Compaction.

An extensive body of literature suggested a possible role of the microtubule-associated protein Tau in chromatin functions and/or organization in neuronal, non-neuronal, and cancer cells. How Tau functions in these processes remains elusive. Here we report that Tau expression in breast cancer cell lines causes resistance to the anti-cancer effects of histone deacetylase inhibitors, by preventing histone deacetylase inhibitor-inducible gene expression and remodeling of chromatin structure. We identify Tau as a protein recognizing and binding to core histone when H3 and H4 are devoid of any post-translational modifications or acetylated H4 that increases the Tau's affinity. Consistent with chromatin structure alterations in neurons found in frontotemporal lobar degeneration, Tau mutations did not prevent histone deacetylase-inhibitor-induced higher chromatin structure remodeling by suppressing Tau binding to histones. In addition, we demonstrate that the interaction between Tau and histones prevents further histone H3 post-translational modifications induced by histone deacetylase-inhibitor treatment by maintaining a more compact chromatin structure. Altogether, these results highlight a new cellular role for Tau as a chromatin reader, which opens new therapeutic avenues to exploit Tau biology in neuronal and cancer cells.

The EGF Domains of MUC4 Oncomucin Mediate HER2 Binding Affinity and Promote Pancreatic Cancer Cell Tumorigenesis.

The HER2 receptor and its MUC4 mucin partner form an oncogenic complex via an extracellular region of MUC4 encompassing three EGF domains that promotes tumor progression of pancreatic cancer (PC) cells. However, the molecular mechanism of interaction remains poorly understood. Herein, we decipher at the molecular level the role and impact of the MUC4EGF domains in the mediation of the binding affinities with HER2 and the PC cell tumorigenicity. We used an integrative approach combining in vitro bioinformatic, biophysical, biochemical, and biological approaches, as well as an in vivo study on a xenograft model of PC. In this study, we specified the binding mode of MUC4EGF domains with HER2 and demonstrate their "growth factor-like" biological activities in PC cells leading to stimulation of several signaling proteins (mTOR pathway, Akt, and ß-catenin) contributing to PC progression. Molecular dynamics simulations of the MUC4EGF/HER2 complexes led to 3D homology models and identification of binding hotspots mediating binding affinity with HER2 and PC cell proliferation. These results will pave the way to the design of potential MUC4/HER2 inhibitors targeting the EGF domains of MUC4. This strategy will represent a new efficient alternative to treat cancers associated with MUC4/HER2 overexpression and HER2-targeted therapy failure as a new adapted treatment to patients.

Discovery of a cryptic site at the interface 2 of TEAD - Towards a new family of YAP/TAZ-TEAD inhibitors.

The Hippo pathway is involved in organ size control and tissue homeostasis by regulating cell growth, proliferation and apoptosis. It controls the phosphorylation of the transcription co-activator YAP (Yes associated protein) and TAZ (Transcriptional coactivator with PDZ-binding motif) in order to control their nuclear import and their interaction with TEAD (Transcriptional Enhanced Associated Domain). YAP, TAZ and TEADs are dysregulated in several cancers making YAP/TAZ-TEAD interaction a new emerging anti-cancer target. We report the synthesis of a set of trisubstituted pyrazoles which bind to hTEAD2 at the interface 2 revealing for the first time a cryptic pocket created by the movement of the phenol ring of Y382. Compound 6 disrupts YAP/TAZ-TEAD interaction in HEK293T cells and inhibits TEAD target genes and cell proliferation in MDA-MB-231 cells. Compound 6 is therefore the first inhibitor of YAP/TAZ-TEAD targeting interface 2. This molecule could serve with other pan-TEAD inhibitors such as interface 3 ligands, for the delineation of the relative importance of VGLL vs YAP/TAZ in a given cellular model.

Soluble Programmed Death Ligand-1 (sPD-L1): A Pool of Circulating Proteins Implicated in Health and Diseases.

Upon T-cell receptor stimulation, the Programmed cell Death-1 receptor (PD-1) expressed on T-cells can interact with its ligand PD-L1 expressed at the surface of cancer cells or antigen-presenting cells. Monoclonal antibodies targeting PD-1 or PD-L1 are routinely used for the treatment of cancers, but their clinical efficacy varies largely across the variety of tumor types. A part of the variability is linked to the existence of several forms of PD-L1, either expressed on the plasma membrane (mPD-L1), at the surface of secreted cellular exosomes (exoPD-L1), in cell nuclei (nPD-L1), or as a circulating, soluble protein (sPD-L1). Here, we have reviewed the different origins and roles of sPD-L1 in humans to highlight the biochemical and functional heterogeneity of the soluble protein. sPD-L1 isoforms can be generated essentially by two non-exclusive processes: (i) proteolysis of m/exoPD-L1 by metalloproteases, such as metalloproteinases (MMP) and A disintegrin and metalloproteases (ADAM), which are capable of shedding membrane PD-L1 to release an active soluble form, and (ii) the alternative splicing of PD-L1 pre-mRNA, leading in some cases to the release of sPD-L1 protein isoforms lacking the transmembrane domain. The expression and secretion of sPD-L1 have been observed in a large variety of pathologies, well beyond cancer, notably in different pulmonary diseases, chronic inflammatory and autoimmune disorders, and viral diseases. The expression and role of sPD-L1 during pregnancy are also evoked. The structural heterogeneity of sPD-L1 proteins, and associated functional/cellular plurality, should be kept in mind when considering sPD-L1 as a biomarker or as a drug target. The membrane, exosomal and soluble forms of PD-L1 are all integral parts of the highly dynamic PD-1/PD-L1 signaling pathway, essential for immune-tolerance or immune-escape.

Properties and reactivity of the folic acid and folate photoproduct 6-formylpterin.

Folates (vitamin B9) are essential components of our diet and our gut microbiota. They are omnipresent in our cells and blood. Folates are necessary for DNA synthesis, methylation, and other vital bioprocesses. Folic acid (FA), as the synthetic form of folates, is largely found in supplements and fortified foods. FA and folate drugs are also extensively used as therapeutics. Therefore, we are continuously exposed to the pterin derivatives, and their photo-degradation products, such as 6-formylpterin (6-FPT) and pterin-6-carboxylic acid. During ultraviolet radiation, these two photolytic products generate reactive oxygen species (ROS) responsible for the cellular oxidative stress. 6-FPT can exhibit variable pro/anti-oxidative roles depending on the cell type and its environment (acting as a cell protector in normal cells, or as an enhancer of drug-induced cell death in cancer cells). The ROS-modulating capacity of 6-FPT is well-known, whereas its intrinsic reactivity has been much less investigated. Here, we have reviewed the properties of 6-FPT and highlighted its capacity to form covalent adducts with the ROS-scavenging drug edaravone (used to treat stroke and amyotrophic lateral sclerosis) as well as its implication in immune surveillance. 6-FPT and its analogue acetyl-6-FPT function as small molecule antigens, recognized by the major histocompatibility complex-related class I-like molecule, MR1, for presentation to mucosal-associated invariant T (MAIT) cells. As modulators of the MR1/MAIT machinery, 6-FPT derivatives could play a significant immuno-regulatory role in different diseases. This brief review shed light on the multiple properties and cellular activities of 6-FPT, well beyond its primary ROS-generating activity.

Aggressiveness Potential of Spontaneous Canine Mucosal Melanoma Can Dictate Distinct Cancer Stem Cell Compartment Behaviors in Regard to Their Initial Size and Expansion Abilities.

Mucosal melanoma represents one of the most highly metastatic and aggressive subtypes of melanoma. The biology of mucosal melanoma is poorly documented, and the lack of experimental models makes it difficult to design and test new therapies. Dogs are frequently affected by melanomas of the oral cavity, making spontaneous canine melanoma a potentially predictable model for their human counterpart. We recently established and characterized two new canine mucosal melanoma cell lines named OCR_OCMM1 and OCR_OCMM2. Here, we identified quiescent cancer stem cell (CSC) subpopulations in both canine cell lines that displayed similarities to human quiescent CSCs: canine melanoma CSCs had the ability to self-renew, produced nonstem cell (SC) progeny, and formed melanospheres that recapitulated the phenotypic profile of the parental tumor. These CSCs also formed melanoma in immunodeficient mice, and the inhibition of PI3K/AKT signaling expanded the CSC pool. A subset of non-CSCs transitioned to become CSCs. OCR_OCMM1 and OCR_OCMM2 displayed different CSC compartment behaviors in regard to their initial size and expansion abilities. Collectively, this study showed that the OCR_OCMM1 and OCR_OCMM2 canine melanoma cell lines are powerful cellular tools to study melanoma SCs, not only for mucosal but also for the more common human cutaneous melanoma.

Chemical reactivity and uses of 1-phenyl-3-methyl-5-pyrazolone (PMP), also known as edaravone.

1-Phenyl-3-methyl-5-pyrazolone is a reagent, known as PMP, used to derivatize monosaccharides for the study of polysaccharides composition and structure, and for the dosage of carbohydrates in complex media. The same molecule is also known as edaravone, a drug approved for the treatment of stroke and amyotrophic lateral sclerosis. It is also a reactive molecule susceptible to form stable adducts with aromatic aldehydes, such as formylpterin and vanillin. In addition, the molecule serves as a scaffold to design of edaravone analogs and drug conjugates, with various pharmacological properties (antioxidant, anticancer, antiviral). We have analyzed the multiple usages of PMP/edaravone to highlight the reactivity of the molecule and its wide range of applications. This phenyl-pyrazolone compound, considered by many as a biochemical reagent and by other as a clinically useful drug, has not yet revealed the full extent of its capacities and benefits.