ITPRIPL1 binds CD3ε to impede T cell activation and enable tumor immune evasion.

Cancer immunotherapy has transformed treatment possibilities, but its effectiveness differs significantly among patients, indicating the presence of alternative pathways for immune evasion. Here, we show that ITPRIPL1 functions as an inhibitory ligand of CD3ε, and its expression inhibits T cells in the tumor microenvironment. The binding of ITPRIPL1 extracellular domain to CD3ε on T cells significantly decreased calcium influx and ZAP70 phosphorylation, impeding initial T cell activation. Treatment with a neutralizing antibody against ITPRIPL1 restrained tumor growth and promoted T cell infiltration in mouse models across various solid tumor types. The antibody targeting canine ITPRIPL1 exhibited notable therapeutic efficacy against naturally occurring tumors in pet clinics. These findings highlight the role of ITPRIPL1 (or CD3L1, CD3ε ligand 1) in impeding T cell activation during the critical "signal one" phase. This discovery positions ITPRIPL1 as a promising therapeutic target against multiple tumor types.

Whole Central and Peripheral Nervous System Mice Dissection.

Animal models represent the workhorse of the neuroscience field. Despite this, today, there is still no step-by-step protocol to dissect a complete rodent nervous system, nor is there a complete schematic representing it that is freely available. Only methods to harvest the brain, the spinal cord, a specific dorsal root ganglion, and the sciatic nerve (separately) are available. Here, we provide detailed pictures and a schematic of the central and peripheral murine nervous system. More importantly, we outline a robust procedure to perform its dissection. The 30 min pre-dissection step allows isolating the intact nervous system within the vertebra with muscles free of viscera and skin. A 2-4 h dissection follows it under a micro-dissection microscope to expose the spinal cord and the thoracic nerves, and finally peel the whole central and peripheral nervous system off the carcass. This protocol represents a significant step forward in studying the anatomy and pathophysiology of the nervous system globally. For example, the dissected dorsal root ganglions from a neurofibromatosis type I mice model can be further processed for histology to unravel changes in tumor progression.

A peptidic inhibitor for PD-1 palmitoylation targets its expression and functions.

Programmed cell death protein 1 (PD-1) is a crucial anticancer target, but the relatively low response rate and acquired resistance to existing antibody drugs highlight an urgent need to develop alternative targeting strategies. Here, we report the palmitoylation of PD-1, discover the main DHHC enzyme for this modification, reveal the mechanism of its effect on PD-1 protein stability, and rationally develop a peptide for targeting PD-1 expression. Palmitoylation promoted the trafficking of PD-1 to the recycling endosome, thus preventing its lysosome-dependent degradation. Palmitoylation of PD-1, but not of PD-L1, promoted mTOR signaling and tumor cell proliferation, and targeting palmitoylation displayed significant anti-tumor effects in a three-dimensional culture system. A peptide was designed to competitively inhibit PD-1 palmitoylation and expression, opening a new route for developing PD-1 inhibitors and combinatorial cancer immunotherapy.

Toward Understanding the Mechanisms of Malignant Peripheral Nerve Sheath Tumor Development.

Malignant peripheral nerve sheath tumors (MPNSTs) originate from the neural crest lineage and are associated with the neurofibromatosis type I syndrome. MPNST is an unmet clinical need. In this review article, we summarize the knowledge and discuss research perspectives related to (1) the natural history of MPNST development; (2) the mouse models recapitulating the progression from precursor lesions to MPNST; (3) the role of the tumor microenvironment in MPNST development, and (4) the signaling pathways linked to MPNST development.

Human cutaneous neurofibroma matrisome revealed by single-cell RNA sequencing.

Neurofibromatosis Type I (NF1) is a neurocutaneous genetic syndrome characterized by a wide spectrum of clinical presentations, including benign peripheral nerve sheath tumor called neurofibroma. These tumors originate from the Schwann cell lineage but other cell types as well as extracellular matrix (ECM) in the neurofibroma microenvironment constitute the majority of the tumor mass. In fact, collagen accounts for up to 50% of the neurofibroma's dry weight. Although the presence of collagens in neurofibroma is indisputable, the exact repertoire of ECM genes and ECM-associated genes (i.e. the matrisome) and their functions are unknown. Here, transcriptome profiling by single-cell RNA sequencing reveals the matrisome of human cutaneous neurofibroma (cNF). We discovered that classic pro-fibrogenic collagen I myofibroblasts are rare in neurofibroma. In contrast, collagen VI, a pro-tumorigenic ECM, is abundant and mainly secreted by neurofibroma fibroblasts. This study also identified potential cell type-specific markers to further elucidate the biology of the cNF microenvironment.

Targeted degradation of immune checkpoint proteins: emerging strategies for cancer immunotherapy.

Cancer immunotherapy using immune-checkpoint blockade has displayed promising clinical effects, but prevalent antibody-based inhibitors face multiple challenges such as low response rate, acquired resistance, and adverse effects. The intracellular expression of PD-1/PD-L1 in recycling endosomes and their active trafficking to membrane highlight the importance of depleting rather than interfering with checkpoint proteins. Preclinical investigations on the therapeutic effects of lead compounds that function by degrading immune checkpoint ligands and receptors have reported highly promising results. By harnessing the degradation capabilities of the lysosome, proteasome and autophagosomes, different small molecules and peptides potently induced degradation of checkpoint proteins and enhanced anti-tumor immunity. Both in vitro and in vivo experiments support the therapeutic efficacy of these molecules. Thus, targeted degradation through endo-lysosomal, autophagic, proteasomal, or endoplasmic reticulum-related pathways may provide promising strategies for tackling the challenges in cancer immunotherapy.

Schwannoma development is mediated by Hippo pathway dysregulation and modified by RAS/MAPK signaling.

Schwannomas are tumors of the Schwann cells that cause chronic pain, numbness, and potentially life-threatening impairment of vital organs. Despite the identification of causative genes, including NF2 (Merlin), INI1/SMARCB1, and LZTR1, the exact molecular mechanism of schwannoma development is still poorly understood. Several studies have identified Merlin as a key regulator of the Hippo, MAPK, and PI3K signaling pathways; however, definitive evidence demonstrating the importance of these pathways in schwannoma pathogenesis is absent. Here, we provide direct genetic evidence that dysregulation of the Hippo pathway in the Schwann cell lineage causes development of multiple schwannomas in mice. We found that canonical Hippo signaling through the effectors YAP/TAZ is required for schwannomagenesis and that MAPK signaling modifies schwannoma formation. Furthermore, cotargeting YAP/TAZ transcriptional activity and MAPK signaling demonstrated a synergistic therapeutic effect on schwannomas. Our new model provides a tractable platform to dissect the molecular mechanisms underpinning schwannoma formation and the role of combinatorial targeted therapy in schwannoma treatment.

Translating current basic research into future therapies for neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is a hereditary tumour syndrome that predisposes to benign and malignant tumours originating from neural crest cells. Biallelic inactivation of the tumour-suppressor gene NF1 in glial cells in the skin, along a nerve plexus or in the brain results in the development of benign tumours: cutaneous neurofibroma, plexiform neurofibroma and glioma, respectively. Despite more than 40 years of research, only one medication was recently approved for treatment of plexiform neurofibroma and no drugs have been specifically approved for the management of other tumours. Work carried out over the past several years indicates that inhibiting different cellular signalling pathways (such as Hippo, Janus kinase/signal transducer and activator of transcription, mitogen-activated protein kinase and those mediated by sex hormones) in tumour cells or targeting cells in the microenvironment (nerve cells, macrophages, mast cells and T cells) might benefit NF1 patients. In this review, we outline previous strategies aimed at targeting these signalling pathways or cells in the microenvironment, agents that are currently in clinical trials, and the latest advances in basic research that could culminate in the development of novel therapeutics for patients with NF1.

Regulations on Messenger RNA: Wires and Nodes.

Somatic cells of an organism virtually share the same DNA but it is the timely expression of specific genes that determine their phenotype and cellular identity. A series of complex molecular machinery allows for the regulated process of RNA transcription, splicing, and translation. In addition, microRNAs and specialized RNA binding proteins can trigger the degradation of mRNAs. Long non-coding RNAs can also regulate mRNA fate in multiple ways. In this chapter, we reviewed the RNA processing mechanisms directly regulating immune checkpoint genes. We also cover RNA-based therapeutic strategies aiming at restoring immunity by targeting immune checkpoint genes.

Heterozygous Tumor Suppressor Microenvironment in Cancer Development.

Hereditary cancer syndromes are typically caused by mutations of a tumor suppressor gene that lead to the early development of multifocal benign neoplasms followed by their malignant progression. However, the term 'hereditary cancer syndrome' may be misleading, as a large subgroup of syndromes are characterized by highly penetrant benign tumors. The reason why these cardinal tumors rarely progress to malignancy has been an elusive question in cancer biology. In this opinion article, we propose a framework where a heterozygous tumor suppressor gene microenvironment has antagonistic roles in tumorigenesis, by accelerating development of benign tumors while restraining further progression to malignant cancers.

Author Correction: Inhibiting PD-L1 palmitoylation enhances T-cell immune responses against tumours.

In the version of this Article originally published, 'palmitoyltransferase ZDHHC3 (DHHC3)' was incorrectly referred to as an 'acetyltransferase' rather than an as an 'acyltransferase'; this has now been corrected in five instances. In Fig. 3a, the label for the bottom row of the blots was mistakenly written as 'GAPHD'; it should have read 'GAPDH'. In the two right-most panels of Fig. 4j, the antibody labels 'α-PD-L1' for the reciprocal co-immunoprecipitation of DHHC3 were incorrect; they should have been 'α-DHHC3'. These errors have been corrected in all versions of the Article.

Inhibiting PD-L1 palmitoylation enhances T-cell immune responses against tumours.

Checkpoint blockade therapy targeting the programmed-death ligand 1 (PD-L1) and its receptor programmed cell death 1 promotes T-cell-mediated immunosurveillance against tumours, and has been associated with marked clinical benefit in cancer patients. Antibodies against PD-L1 function by blocking PD-L1 on the cell surface, but intracellular storage of PD-L1 and its active redistribution to the cell membrane can minimize the therapeutic benefits, which highlights the importance of targeting PD-L1 throughout the whole cell. Here, we show that PD-L1 is palmitoylated in its cytoplasmic domain, and that this lipid modification stabilizes PD-L1 by blocking its ubiquitination, consequently suppressing PD-L1 degradation by lysosomes. We identified palmitoyltransferase ZDHHC3 (DHHC3) as the main acetyltransferase required for the palmitoylation of PD-L1, and show that the inhibition of PD-L1 palmitoylation via 2-bromopalmitate, or the silencing of DHHC3, activates antitumour immunity in vitro and in mice bearing MC38 tumour cells. We also designed a competitive inhibitor of PD-L1 palmitoylation that decreases PD-L1 expression in tumour cells to enhance T-cell immunity against the tumours. These findings suggest new strategies for overcoming PD-L1-mediated immune evasion in cancer.

Spatiotemporal Loss of NF1 in Schwann Cell Lineage Leads to Different Types of Cutaneous Neurofibroma Susceptible to Modification by the Hippo Pathway.

Neurofibromatosis type 1 (NF1) is a cancer predisposition disorder that results from inactivation of the tumor suppressor neurofibromin, a negative regulator of RAS signaling. Patients with NF1 present with a wide range of clinical manifestations, and the tumor with highest prevalence is cutaneous neurofibroma (cNF). Most patients harboring cNF suffer greatly from the burden of those tumors, which have no effective medical treatment. Ironically, none of the numerous NF1 mouse models developed so far recapitulate cNF. Here, we discovered that HOXB7 serves as a lineage marker to trace the developmental origin of cNF neoplastic cells. Ablating Nf1 in the HOXB7 lineage faithfully recapitulates both human cutaneous and plexiform neurofibroma. In addition, we discovered that modulation of the Hippo pathway acts as a "modifier" for neurofibroma tumorigenesis. This mouse model opens the doors for deciphering the evolution of cNF to identify effective therapies, where none exist today. SIGNIFICANCE: This study provides insights into the developmental origin of cNF, the most common tumor in NF1, and generates the first mouse model that faithfully recapitulates both human cutaneous and plexiform neurofibroma. The study also demonstrates that the Hippo pathway can modify neurofibromagenesis, suggesting that dampening the Hippo pathway could be an attractive therapeutic target.This article is highlighted in the In This Issue feature, p. 1.

NF1 heterozygosity fosters de novo tumorigenesis but impairs malignant transformation.

Neurofibromatosis type 1 (NF1) is an autosomal genetic disorder. Patients with NF1 are associated with mono-allelic loss of the tumor suppressor gene NF1 in their germline, which predisposes them to develop a wide array of benign lesions. Intriguingly, recent sequencing efforts revealed that the NF1 gene is frequently mutated in multiple malignant tumors not typically associated with NF1 patients, suggesting that NF1 heterozygosity is refractory to at least some cancer types. In two orthogonal mouse models representing NF1- and non-NF1-related tumors, we discover that an Nf1+/- microenvironment accelerates the formation of benign tumors but impairs further progression to malignancy. Analysis of benign and malignant tumors commonly associated with NF1 patients, as well as those with high NF1 gene mutation frequency, reveals an antagonistic role for NF1 heterozygosity in tumor initiation and malignant transformation and helps to reconciliate the role of the NF1 gene in both NF1 and non-NF1 patient contexts.

The biology of cutaneous neurofibromas: Consensus recommendations for setting research priorities.

OBJECTIVE: A group of experts in dermatology, genetics, neuroscience, and regenerative medicine collaborated to summarize current knowledge on the defined factors contributing to cutaneous neurofibroma (cNF) development and to provide consensus recommendations for future research priorities to gain an improved understanding of the biology of cNF. METHODS: The group members reviewed published and unpublished data on cNF and related diseases via literature search, defined a set of key topic areas deemed critical in cNF pathogenesis, and developed recommendations in a series of consensus meetings. RESULTS: Five specific topic areas were identified as being relevant to providing an enhanced understanding of the biology of cNF: (1) defining the human cells of origin; (2) understanding the role of the microenvironment, focusing on neurons, mast cells, and fibroblasts; (3) defining the genetic and molecular differences between the cNFs, focusing on size and number; (4) understanding if sex hormones are critical for cNF development or progression; and (5) identifying challenges in establishing in vitro and in vivo models representing human cNF. CONCLUSIONS: The complexity of cNF biology stems from its heterogeneity at multiple levels including genetic, spatial involvement, temporal development, and cellular composition. We propose a unified working model for cNF that builds a framework to address the key questions about cNF that, when answered, will provide the necessary understanding of cNF biology to allow meaningful development of therapies.

Contributions of inflammation and tumor microenvironment to neurofibroma tumorigenesis.

Neurofibromatosis type 1 associates with multiple neoplasms, and the Schwann cell tumor neurofibroma is the most prevalent. A hallmark feature of neurofibroma is mast cell infiltration, which is recruited by chemoattractant stem cell factor (SCF) and has been suggested to sustain neurofibroma tumorigenesis. In the present study, we use new, genetically engineered Scf mice to decipher the contributions of tumor-derived SCF and mast cells to neurofibroma development. We demonstrate that mast cell infiltration is dependent on SCF from tumor Schwann cells. However, removal of mast cells by depleting the main SCF source only slightly affects neurofibroma progression. Other inflammation signatures show that all neurofibromas are associated with high levels of macrophages regardless of Scf status. These findings suggest an active inflammation in neurofibromas and partly explain why mast cell removal alone is not sufficient to relieve tumor burden in this experimental neurofibroma model. Furthermore, we show that plexiform neurofibromas are highly associated with injury-prone spinal nerves that are close to flexible vertebras. In summary, our study details the role of inflammation in neurofibromagenesis. Our data indicate that prevention of inflammation and possibly also nerve injury at the observed tumor locations are therapeutic approaches for neurofibroma prophylaxis and that such treatment should be explored.

Splicing isoform-specific functional genomic in cancer cells

Alternative splicing is a regulated process whereby one gene can generate multiple mRNA isoforms susceptible to be translated into protein isoforms of various functions. Several publications report the aberrant expression of splicing isoforms in cancer cells and tissues. However, in most cases, their function remains to be established. In this review article, I will discuss the molecular tool available to perform isoform-specific functional genomics, the methodologies to quantify their effectiveness and the resulting isoform-specific phenotype in human cancer cell lines (AU)

Tumor microenvironment-associated modifications of alternative splicing.

Pre-mRNA alternative splicing is modified in cancer, but the origin and specificity of these changes remain unclear. Here, we probed ovarian tumors to identify cancer-associated splicing isoforms and define the mechanism by which splicing is modified in cancer cells. Using high-throughput quantitative PCR, we monitored the expression of splice variants in laser-dissected tissues from ovarian tumors. Surprisingly, changes in alternative splicing were not limited to the tumor tissues but were also found in the tumor microenvironment. Changes in the tumor-associated splicing events were found to be regulated by splicing factors that are differentially expressed in cancer tissues. Overall, ∼20% of the alternative splicing events affected by the down-regulation of the splicing factors QKI and RBFOX2 were altered in the microenvironment of ovarian tumors. Together, our results indicate that the tumor microenvironment undergoes specific changes in alternative splicing orchestrated by a limited number of splicing factors.

Redirecting splicing with bifunctional oligonucleotides.

Ectopic modulators of alternative splicing are important tools to study the function of splice variants and for correcting mis-splicing events that cause human diseases. Such modulators can be bifunctional oligonucleotides made of an antisense portion that determines target specificity, and a non-hybridizing tail that recruits proteins or RNA/protein complexes that affect splice site selection (TOSS and TOES, respectively, for targeted oligonucleotide silencer of splicing and targeted oligonucleotide enhancer of splicing). The use of TOSS and TOES has been restricted to a handful of targets. To generalize the applicability and demonstrate the robustness of TOSS, we have tested this approach on more than 50 alternative splicing events. Moreover, we have developed an algorithm that can design active TOSS with a success rate of 80%. To produce bifunctional oligonucleotides capable of stimulating splicing, we built on the observation that binding sites for TDP-43 can stimulate splicing and improve U1 snRNP binding when inserted downstream from 5' splice sites. A TOES designed to recruit TDP-43 improved exon 7 inclusion in SMN2. Overall, our study shows that bifunctional oligonucleotides can redirect splicing on a variety of genes, justifying their inclusion in the molecular arsenal that aims to alter the production of splice variants.

8-BuS-ATP derivatives as specific NTPDase1 inhibitors.

BACKGROUND AND PURPOSE: Ectonucleotidases control extracellular nucleotide levels and consequently, their (patho)physiological responses. Among these enzymes, nucleoside triphosphate diphosphohydrolase-1 (NTPDase1), -2, -3 and -8 are the major ectonucleotidases responsible for nucleotide hydrolysis at the cell surface under physiological conditions, and NTPDase1 is predominantly located at the surface of vascular endothelial cells and leukocytes. Efficacious inhibitors of NTPDase1 are required to modulate responses induced by nucleotides in a number of pathological situations such as thrombosis, inflammation and cancer. EXPERIMENTAL APPROACH: Here, we present the synthesis and enzymatic characterization of five 8-BuS-adenine nucleotide derivatives as potent and selective inhibitors of NTPDase1. KEY RESULTS: The compounds 8-BuS-AMP, 8-BuS-ADP and 8-BuS-ATP inhibit recombinant human and mouse NTPDase1 by mixed type inhibition, predominantly competitive with Ki values <1 µM. In contrast to 8-BuS-ATP which could be hydrolyzed by other NTPDases, the other BuS derivatives were resistant to hydrolysis by either NTPDase1, -2, -3 or -8. 8-BuS-AMP and 8-BuS-ADP were the most potent and selective inhibitors of NTPDase1 expressed in human umbilical vein endothelial cells as well as in situ in human and mouse tissues. As expected, as a result of their inhibition of recombinant human NTPDase1, 8-BuS-AMP and 8-BuS-ADP impaired the ability of this enzyme to block platelet aggregation. Importantly, neither of these two inhibitors triggered platelet aggregation nor prevented ADP-induced platelet aggregation, in support of their inactivity towards P2Y1 and P2Y12 receptors. CONCLUSIONS AND IMPLICATIONS: The 8-BuS-AMP and 8-BuS-ADP have therefore potential to serve as drugs for the treatment of pathologies regulated by NTPDase1.