Transarterial Embolization for Active Gastrointestinal Bleeding: Predictors of Early Mortality and Early Rebleeding.

Background: The aim of this study was to determine predictive factors of early mortality and early rebleeding (≤30 days) following transarterial embolization (TAE) for treatment of acute gastrointestinal bleeding. Methods: All consecutive patients admitted for acute gastrointestinal bleeding to the interventional radiology department in a tertiary center between January 2012 and January 2022 were included. Exclusion criteria were patients: (1) aged < 18-year-old, (2) referred to the operation room without TAE, (3) treated for hemobilia, (4) with mesenteric hematoma, (5) lost to follow-up within 30 days after the procedure. We evaluated pre and per-procedure clinical data, biological data, outcomes, and complications. Results: Sixty-eight patients were included: 55 (80.9%) experienced upper gastrointestinal bleeding and 13 (19.1%) lower gastrointestinal bleeding. Median age was 69 (61−74) years. There were 49 (72%) males. Median hemoglobin was 7.25 (6.1−8.3) g/dL. There were 30 (50%) ulcers. Coils were used in 46 (67.6%) procedures. Early mortality was 15 (22.1%) and early rebleeding was 17 (25%). In multivariate analysis, hyperlactatemia (≥2 mmol/L) were predictive of early mortality (≤30 days). A high number of red blood cells units was associated with early rebleeding. Conclusion: This study identified some predictive factors of 30-day mortality and early rebleeding following TAE. This will assist in patient selection and may help improve the management of gastrointestinal bleeding.

Safety and efficacy of emergency transarterial embolization for mesenteric bleeding.

BACKGROUND: Patients with spontaneous or traumatic active mesenteric bleeding cannot be treated endoscopically. Transarterial embolization can serve as a potential alternative to emergency surgery. Literature on transarterial embolization for mesenteric bleeding remains very scarce. The objective of this study was to evaluate the safety and efficacy of transarterial embolization for mesenteric bleeding. We reviewed all consecutive patients admitted for mesenteric bleeding to the interventional radiology department, in a tertiary center, between January 2010 and March 2021. Mesenteric bleeding was defined as mesenteric hematoma and contrast extravasation and/or pseudoaneurysm visible on pre-operative CT scan. We evaluated technical success, clinical success, and complications. RESULTS: Among the 17 patients admitted to the interventional department for mesenteric bleeding, 15 presented with active mesenteric bleeding requiring transarterial embolization with five patients with hemodynamic instability. Mean age was 67 ± 14 years, including 12 (70.6%) males. Technical success was achieved in 14/15 (93.3%) patients. One patient with technical failure was treated by percutaneous embolization with NBCA-Lipiodol mixture. Three patients (20%) had early rebleeding: two were treated by successful repeat embolization and one by surgery. One patient (6.7%) had early death within 30 days and two patients (13.3%) had late death after 30 days. Mean length of hospitalization was 12.8 ± 7 days. There were no transarterial embolization-related ischemic complications. CONCLUSION: Transarterial embolization is a safe and effective technique for treating mesenteric bleeding even in patients with hemodynamic instability. Transarterial embolization doesn't close the door to surgery and could be proposed as first intention in case of mesenteric bleeding.

Transarterial Embolization for Spontaneous Soft-Tissue Hematomas: Predictive Factors for Early Death.

INTRODUCTION: The aim of this retrospective monocentric study was to assess the safety and efficacy of spontaneous soft-tissue hematoma transarterial embolization (TAE) and to evaluate predictive factors for early mortality (≤30 days) after TAE for spontaneous soft-tissue hematoma (SSTH). MATERIALS AND METHODS: Between January 2010 and March 2022, all patients referred to our hospital for spontaneous soft-tissue hematoma and treated by emergency TAE were reviewed. Inclusion criteria were patients: ≥18-year-old, with active bleeding shown on preoperative multidetector row computed tomography, with spontaneous soft-tissue hematoma, and treated by TAE. Exclusion criteria were patients with soft-tissue hematomas of traumatic, iatrogenic, or tumoral origin. Clinical, biological, and imaging records were reviewed. Imaging data included delimitation of hematoma volume and presence of fluid level. Univariate and multivariate analyses were performed to check for associations with early mortality. RESULTS: Fifty-six patients were included. Median age was 75.5 [9-83] ([Q1-Q3] years and 23 (41.1%) were males. Fifty-one patients (91.1%) received antiplatelet agent and/or anticoagulant therapy. All 56 patients had active bleeding shown on a preoperative CT scan. Thirty-seven (66.0%) hematomas involved the retroperitoneum. Median hemoglobin level was 7.6 [4.4-8.2] g/dL. Gelatine sponge was used in 32/56 (57.1%) procedures. Clinical success was obtained in 48/56 (85.7%) patients and early mortality occurred in 15/56 (26.8%) patients. In univariate and multivariate analysis, retroperitoneal location and volume of hematoma were associated with early mortality. CONCLUSION: Retroperitoneal location and volume of hematoma seem to be risk factors for early death in the context of TAE for spontaneous soft-tissue hematoma. Larger multicenter studies are necessary to identify others predictive factors for early mortality and to anticipate which patients may benefit from an interventional strategy with TAE.

Ezrin Is a Novel Protein Partner of Aquaporin-5 in Human Salivary Glands and Shows Altered Expression and Cellular Localization in Sjögren's Syndrome.

Sjögren's syndrome (SS) is an exocrinopathy characterized by the hypofunction of salivary glands (SGs). Aquaporin-5 (AQP5); a water channel involved in saliva formation; is aberrantly distributed in SS SG acini and contributes to glandular dysfunction. We aimed to investigate the role of ezrin in AQP5 mislocalization in SS SGs. The AQP5-ezrin interaction was assessed by immunoprecipitation and proteome analysis and by proximity ligation assay in immortalized human SG cells. We demonstrated, for the first time, an interaction between ezrin and AQP5. A model of the complex was derived by computer modeling and in silico docking; suggesting that AQP5 interacts with the ezrin FERM-domain via its C-terminus. The interaction was also investigated in human minor salivary gland (hMSG) acini from SS patients (SICCA-SS); showing that AQP5-ezrin complexes were absent or mislocalized to the basolateral side of SG acini rather than the apical region compared to controls (SICCA-NS). Furthermore, in SICCA-SS hMSG acinar cells, ezrin immunoreactivity was decreased at the acinar apical region and higher at basal or lateral regions, accounting for altered AQP5-ezrin co-localization. Our data reveal that AQP5-ezrin interactions in human SGs could be involved in the regulation of AQP5 trafficking and may contribute to AQP5-altered localization in SS patients.

A Low Total Psoas Muscle Area Index Is a Strong Prognostic Factor in Metastatic Pancreatic Cancer.

OBJECTIVES: The total psoas area index (TPI) is an emerging alternative to the total skeletal muscle area index as a prognostic factor but has never been evaluated in metastatic pancreatic cancer (mPC). METHODS: Areas were manually recorded, as previously described. Sex-specific cutoffs were identified by optimum stratification of TPI using log-rank χ2 statistic associated with mortality to define sarcopenic psoas. Progression-free survival (PFS) and overall survival (OS) were the primary objectives. Two period groups were used as internal validation. RESULTS: During the period study, 79 patients were treated for mPC. The TPI was correlated with PFS (hazards ratio, 0.81; P = 0.02) and OS (hazards ratio, 0.7; P < 0.001). Optimum thresholds defining sarcopenic psoas were less than 5.73 cm2/m2 in men and less than 4.37 cm2/m2 in women. Patients with sarcopenic psoas (62.0%) had shorter median PFS (2.9 months) compared with the others (6.6 months, adjusted P log-rank = 0.01), independently to the intensity of chemotherapy, weight loss, and performance status greater than 1. Similarly, OS was independently shorter in patients with sarcopenic psoas (7.6 months) versus the others (22.2 months, adjusted P < 0.001). These results were confirmed in the 2 period groups. CONCLUSIONS: A low TPI is a stronger independent prognostic factor in mPC.

Functional characterization of Arabidopsis ARGONAUTE 3 in reproductive tissues.

Arabidopsis encodes 10 ARGONAUTE (AGO) effectors of RNA silencing, canonically loaded with either 21-22 nucleotide (nt) long small RNAs (sRNAs) to mediate post-transcriptional gene silencing (PTGS) or 24 nt sRNAs to promote RNA-directed DNA methylation. Using full-locus constructs, we characterized the expression, biochemical properties and possible modes of action of AGO3. Although AGO3 arose from a recent duplication at the AGO2 locus, their expression patterns differ drastically, with AGO2 being expressed in both male and female gametes whereas AGO3 accumulates in aerial vascular terminations and specifically in chalazal seed integuments. Accordingly, AGO3 downregulation alters gene expression in siliques. Similar to AGO2, AGO3 binds sRNAs with a strong 5' adenosine bias, but unlike Arabidopsis AGO2, it binds 24 nt sRNAs most efficiently. AGO3 immunoprecipitation experiments in siliques revealed that these sRNAs mostly correspond to genes and intergenic regions in a manner reflecting their respective accumulation from their loci of origin. AGO3 localizes to the cytoplasm and co-fractionates with polysomes to possibly mediate PTGS via translation inhibition.

Anatomical specializations of the gizzard in soil-feeding termites (Termitidae, Apicotermitinae): Taxonomical and functional implications.

The anatomy of the workers' digestive tube is essential in taxonomical studies of soil-feeding Apicotermitinae termites, especially in soldierless lineages. Two structures, the mesenteric-proctodeal junction and the enteric valve, have long been important to distinguish genera and species. By contrast, the gizzard (proventriculus) has been almost ignored by taxonomists because of its generally regressed state in soil-feeding termites. In this study, we document in detail for the first time the sclerotized structures and ornamentations in the gizzard in the Apicotermitinae subfamily. We identified two main clusters of species: those without ornamentations and those exhibiting a sclerotized pulvillar armature, which may include spicules or spines of diverse sizes, numbers and dispositions. The latter group comprises the majority of African soldierless species, a widely diverse and dominant group in tropical forests and savannas. We outline the potential role of the anatomy of the gizzard in the taxonomy of Apicotermitinae based on the interspecific anatomical variation of the pulvillar armatures. We suggest that sclerotized ornamentations regulate the flow of food particles and break or lacerate aggregates to facilitate the access of enzymes in the midgut.

Phosphoinositide 5-phosphatases SKIP and SHIP2 in ruffles, the endoplasmic reticulum and the nucleus: An update.

Phosphoinositides (PIs) are phosphorylated derivatives of phosphatidylinositol. They act as signaling molecules linked to essential cellular mechanisms in eukaryotic cells, such as cytoskeleton organization, mitosis, polarity, migration or invasion. PIs are phosphorylated and dephosphorylated by a large number of PI kinases and PI phosphatases acting at the 5-, 4- and 3- position of the inositol ring. PI 5-phosphatases i.e. OCRL, INPP5B, SHIP1/2, Synaptojanin 1/2, INPP5E, INPP5J, SKIP (INPP5K) are enzymes that dephosphorylate the 5-phosphate position of PIs. Several human genetic diseases such as the Lowe syndrome, some congenital muscular dystrophy and opsismodysplasia are due to mutations in PI phosphatases, resulting in loss-of-function. The PI phosphatases are also up or down regulated in several human cancers such as glioblastoma or breast cancer. Their cellular localization, that is dynamic and varies in response to stimuli, is an important issue to understand function. This is the case for two members of the PI 5-phosphatase SKIP and SHIP2. Both enzymes are in ruffles, plasma membranes, the endoplasmic reticulum, a situation that is unique for SKIP, and the nucleus. Following localization, PI 5-phosphatases act on specific cellular pools of PIs, which in turn interact with target proteins. Nuclear PIs have emerged as regulators of genome functions in different area of cell signaling. They often localize to nuclear speckles, as do several PI metabolizing kinases and phosphatases. We asked whether SKIP and SHIP2 could have an impact on nuclear PI(4,5)P2. In two glioblastoma cell models, lowering SKIP expression had an impact on nuclear PI(4,5)P2. In a model of SHIP2 deletion in MCF-7 cells, no change in nuclear PI(4,5)P2 was observed. Finally, we present evidence of an anti-tumoral role of SKIP in vivo, in xenografts using as model U87shSKIP cells.

Distinct Vulnerability and Resilience of Human Neuroprogenitor Subtypes in Cerebral Organoid Model of Prenatal Hypoxic Injury.

Prenatal hypoxic injury (HI) is a leading cause of neurological disability. The immediate and long-term effects of hypoxia on progenitor homeostasis and developmental progression during early human brain development remain unclear. This gap is due to difficulty to access human fetal brain tissues and inadequate animal models to study human corticogenesis. Recent optimizations of cerebral organoid models derived from human embryonic stem (ES) cells present new opportunities to investigate pathophysiology of prenatal HI. Here, we implemented a transient HI model using human cerebral organoids with dorsal forebrain specification. We demonstrated that transient hypoxia resulted in immediate and prolonged apoptosis in cerebral organoids, with outer radial glia (oRG), a progenitor population more prominent in primates, and differentiating neuroblasts/immature neurons suffering larger losses. In contrast, neural stem cells in ventricular zone displayed relative resilience to HI and exhibited a shift of cleavage plane angle favoring symmetric division, thereby providing a mechanism to replenish the stem cell pool. Furthermore, we defined the vulnerable window and neurodifferentiation stages that are particularly sensitive to HI. Understanding cell type-specific and stage-dependent effects of prenatal HI on survival and mitotic behavior of human neuroprogenitor subtypes during early human corticogenesis helps elucidate the etiology of neurodevelopmental disorders, and provides a therapeutic starting point to protect the vulnerable populations at critical timeframes.

Extensive profiling in Arabidopsis reveals abundant polysome-associated 24-nt small RNAs including AGO5-dependent pseudogene-derived siRNAs.

In a reductionist perspective, plant silencing small (s)RNAs are often classified as mediating nuclear transcriptional gene silencing (TGS) or cytosolic posttranscriptional gene silencing (PTGS). Among the PTGS diagnostics is the association of AGOs and their sRNA cargos with the translation apparatus. In Arabidopsis, this is observed for AGO1 loaded with micro(mi)RNAs and, accordingly, translational-repression (TR) is one layer of plant miRNA action. Using AGO1:miRNA-mediated TR as a paradigm, we explored, with two unrelated polysome-isolation methods, which, among the ten Arabidopsis AGOs and numerous sRNA classes, interact with translation. We found that representatives of all three AGO-clades associate with polysomes, including the TGS-effector AGO4 and stereotypical 24-nt sRNAs that normally mediate TGS of transposons/repeats. Strikingly, approximately half of these annotated 24-nt siRNAs displayed unique matches in coding regions/introns of genes, and in pseudogenes, but not in transposons/repeats commonly found in their vicinity. Protein-coding gene-derived 24-nt sRNAs correlate with gene-body methylation. Those derived from pseudogenes belong to two main clusters defined by their parental-gene expression patterns, and are vastly enriched in AGO5, itself found on polysomes. Based on their tight expression pattern in developing and mature siliques, their biogenesis, and genomic/epigenomic features of their loci-of-origin, we discuss potential roles for these hitherto unknown polysome-enriched, pseudogene-derived siRNAs.

DMRT5, DMRT3, and EMX2 Cooperatively Repress Gsx2 at the Pallium-Subpallium Boundary to Maintain Cortical Identity in Dorsal Telencephalic Progenitors.

Specification of dorsoventral regional identity in progenitors of the developing telencephalon is a first pivotal step in the development of the cerebral cortex and basal ganglia. Previously, we demonstrated that the two zinc finger doublesex and mab-3 related (Dmrt) genes, Dmrt5 (Dmrta2) and Dmrt3, which are coexpressed in high caudomedial to low rostrolateral gradients in the cerebral cortical primordium, are separately needed for normal formation of the cortical hem, hippocampus, and caudomedial neocortex. We have now addressed the role of Dmrt3 and Dmrt5 in controlling dorsoventral division of the telencephalon in mice of either sex by comparing the phenotypes of single knock-out (KO) with double KO embryos and by misexpressing Dmrt5 in the ventral telencephalon. We find that DMRT3 and DMRT5 act as critical regulators of progenitor cell dorsoventral identity by repressing ventralizing regulators. Early ventral fate transcriptional regulators expressed in the dorsal lateral ganglionic eminence, such as Gsx2, are upregulated in the dorsal telencephalon of Dmrt3;Dmrt5 double KO embryos and downregulated when ventral telencephalic progenitors express ectopic Dmrt5 Conditional overexpression of Dmrt5 throughout the telencephalon produces gene expression and structural defects that are highly consistent with reduced GSX2 activity. Further, Emx2;Dmrt5 double KO embryos show a phenotype similar to Dmrt3;Dmrt5 double KO embryos, and both DMRT3, DMRT5 and the homeobox transcription factor EMX2 bind to a ventral telencephalon-specific enhancer in the Gsx2 locus. Together, our findings uncover cooperative functions of DMRT3, DMRT5, and EMX2 in dividing dorsal from ventral in the telencephalon.SIGNIFICANCE STATEMENT We identified the DMRT3 and DMRT5 zinc finger transcription factors as novel regulators of dorsoventral patterning in the telencephalon. Our data indicate that they have overlapping functions and compensate for one another. The double, but not the single, knock-out produces a dorsal telencephalon that is ventralized, and olfactory bulb tissue takes over most remaining cortex. Conversely, overexpressing Dmrt5 throughout the telencephalon causes expanded expression of dorsal gene determinants and smaller olfactory bulbs. Furthermore, we show that the homeobox transcription factor EMX2 that is coexpressed with DMRT3 and DMRT5 in cortical progenitors cooperates with them to maintain dorsoventral patterning in the telencephalon. Our study suggests that DMRT3/5 function with EMX2 in positioning the pallial-subpallial boundary by antagonizing the ventral homeobox transcription factor GSX2.

Inhibition of SHIP2 activity inhibits cell migration and could prevent metastasis in breast cancer cells.

Metastasis of breast cancer cells to distant organs is responsible for ∼50% of breast cancer-related deaths in women worldwide. SHIP2 (also known as INPPL1) is a phosphoinositide 5-phosphatase for phosphatidylinositol (3,4,5)-trisphosphate [PI(3,4,5)P3] and phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2]. Here we show, through depletion of SHIP2 in triple negative MDA-MB-231 cells and the use of SHIP2 inhibitors, that cell migration appears to be positively controlled by SHIP2. The effect of SHIP2 on migration, as observed in MDA-MB-231 cells, appears to be mediated by PI(3,4)P2. Adhesion on fibronectin is always increased in SHIP2-depleted cells. Apoptosis measured in MDA-MB-231 cells is also increased in SHIP2-depleted cells as compared to control cells. In xenograft mice, SHIP2-depleted MDA-MB-231 cells form significantly smaller tumors than those formed by control cells and less metastasis is detected in lung sections. Our data reveal a general role for SHIP2 in the control of cell migration in breast cancer cells and a second messenger role for PI(3,4)P2 in the migration mechanism. In MDA-MB-231 cells, SHIP2 has a function in apoptosis in cells incubated in vitro and in mouse tumor-derived cells, which could account for its role on tumor growth determined in vivo.

A targeted 3D EM and correlative microscopy method using SEM array tomography.

Using electron microscopy to localize rare cellular events or structures in complex tissue is challenging. Correlative light and electron microscopy procedures have been developed to link fluorescent protein expression with ultrastructural resolution. Here, we present an optimized scanning electron microscopy (SEM) workflow for volumetric array tomography for asymmetric samples and model organisms (Caenorhabditis elegans, Drosophila melanogaster, Danio rerio). We modified a diamond knife to simplify serial section array acquisition with minimal artifacts. After array acquisition, the arrays were transferred to a glass coverslip or silicon wafer support. Using light microscopy, the arrays were screened rapidly for initial recognition of global anatomical features (organs or body traits). Then, using SEM, an in-depth study of the cells and/or organs of interest was performed. Our manual and automatic data acquisition strategies make 3D data acquisition and correlation simpler and more precise than alternative methods. This method can be used to address questions in cell and developmental biology that require the efficient identification of a labeled cell or organelle.

A genome-wide transcriptome and translatome analysis of Arabidopsis transposons identifies a unique and conserved genome expression strategy for Ty1/Copia retroelements.

Retroelements, the prevalent class of plant transposons, have major impacts on host genome integrity and evolution. They produce multiple proteins from highly compact genomes and, similar to viruses, must have evolved original strategies to optimize gene expression, although this aspect has been seldom investigated thus far. Here, we have established a high-resolution transcriptome/translatome map for the near-entirety of Arabidopsis thaliana transposons, using two distinct DNA methylation mutants in which transposon expression is broadly de-repressed. The value of this map to study potentially intact and transcriptionally active transposons in A. thaliana is illustrated by our comprehensive analysis of the cotranscriptional and translational features of Ty1/Copia elements, a family of young and active retroelements in plant genomes, and how such features impact their biology. Genome-wide transcript profiling revealed a unique and widely conserved alternative splicing event coupled to premature termination that allows for the synthesis of a short subgenomic RNA solely dedicated to production of the GAG structural protein and that preferentially associates with polysomes for efficient translation. Mutations engineered in a transgenic version of the Arabidopsis EVD Ty1/Copia element further show how alternative splicing is crucial for the appropriate coordination of full-length and subgenomic RNA transcription. We propose that this hitherto undescribed genome expression strategy, conserved among plant Ty1/Copia elements, enables an excess of structural versus catalytic components, mandatory for mobilization.

Therapeutic Activity of Anti-AXL Antibody against Triple-Negative Breast Cancer Patient-Derived Xenografts and Metastasis.

Purpose: AXL receptor tyrosine kinase has been described as a relevant molecular marker and a key player in invasiveness, especially in triple-negative breast cancer (TNBC).Experimental Design: We evaluate the antitumor efficacy of the anti-AXL monoclonal antibody 20G7-D9 in several TNBC cell xenografts or patient-derived xenograft (PDX) models and decipher the underlying mechanisms. In a dataset of 254 basal-like breast cancer samples, genes correlated with AXL expression are enriched in EMT, migration, and invasion signaling pathways.Results: Treatment with 20G7-D9 inhibited tumor growth and bone metastasis formation in AXL-positive TNBC cell xenografts or PDX, but not in AXL-negative PDX, highlighting AXL role in cancer growth and invasion. In vitro stimulation of AXL-positive cancer cells by its ligand GAS6 induced the expression of several EMT-associated genes (SNAIL, SLUG, and VIM) through an intracellular signaling implicating the transcription factor FRA-1, important in cell invasion and plasticity, and increased their migration/invasion capacity. 20G7-D9 induced AXL degradation and inhibited all AXL/GAS6-dependent cell signaling implicated in EMT and in cell migration/invasion.Conclusions: The anti-AXL antibody 20G7-D9 represents a promising therapeutic strategy in TNBC with mesenchymal features by inhibiting AXL-dependent EMT, tumor growth, and metastasis formation. Clin Cancer Res; 23(11); 2806-16. ©2016 AACR.

Site-Directed Chemical Probing to map transient RNA/protein interactions.

RNA-protein interactions are at the bases of many biological processes, forming either tight and stable functional ribonucleoprotein (RNP) complexes (i.e. the ribosome) or transitory ones, such as the complexes involving RNA chaperone proteins. To localize the sites where a protein interacts on an RNA molecule, a common simple and inexpensive biochemical method is the footprinting technique. The protein leaves its footprint on the RNA acting as a shield to protect the regions of interaction from chemical modification or cleavages obtained with chemical or enzymatic nucleases. This method has proven its efficiency to study in vitro the organization of stable RNA-protein complexes. Nevertheless, when the protein binds the RNA very dynamically, with high off-rates, protections are very often difficult to observe. For the analysis of these transient complexes, we describe an alternative strategy adapted from the Site Directed Chemical Probing (SDCP) approach and we compare it with classical footprinting. SDCP relies on the modification of the RNA binding protein to tether an RNA probe (usually Fe-EDTA) to specific protein positions. Local cleavages on the regions of interaction can be used to localize the protein and position its domains on the RNA molecule. This method has been used in the past to monitor stable complexes; we provide here a detailed protocol and a practical example of its application to the study of Escherichia coli RNA chaperone protein S1 and its transitory complexes with mRNAs.

Vesicular trafficking regulators are new players in breast cancer progression: Role of TOM1L1 in ERBB2-dependent invasion.

ERBB2 (v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2) amplification is associated with invasive breast cancer. We discovered that TOM1L1 (target of myb1-like 1) and ERBB2 co-amplification defines a novel mechanism involved in breast cancer metastatic progression. Upregulation of the vesicular trafficking protein TOM1L1 enhances plasma membrane delivery of membrane-type 1 matrix metalloprotease (MT1-MMP) for efficient extracellular matrix degradation and tumor cell dissemination.

TOM1L1 drives membrane delivery of MT1-MMP to promote ERBB2-induced breast cancer cell invasion.

ERBB2 overexpression in human breast cancer leads to invasive carcinoma but the mechanism is not clearly understood. Here we report that TOM1L1 is co-amplified with ERBB2 and defines a subgroup of HER2(+)/ER(+) tumours with early metastatic relapse. TOM1L1 encodes a GAT domain-containing trafficking protein and is a SRC substrate that negatively regulates tyrosine kinase signalling. We demonstrate that TOM1L1 upregulation enhances the invasiveness of ERBB2-transformed cells. This pro-tumoural function does not involve SRC, but implicates membrane-bound membrane-type 1 MMP (MT1-MMP)-dependent activation of invadopodia, membrane protrusions specialized in extracellular matrix degradation. Mechanistically, ERBB2 elicits the indirect phosphorylation of TOM1L1 on Ser321. The phosphorylation event promotes GAT-dependent association of TOM1L1 with the sorting protein TOLLIP and trafficking of the metalloprotease MT1-MMP from endocytic compartments to invadopodia for tumour cell invasion. Collectively, these results show that TOM1L1 is an important element of an ERBB2-driven proteolytic invasive programme and that TOM1L1 amplification potentially enhances the metastatic progression of ERBB2-positive breast cancers.

The role of small adaptor proteins in the control of oncogenic signalingr driven by tyrosine kinases in human cancer.

Protein phosphorylation on tyrosine (Tyr) residues has evolved as an important mechanism to coordinate cell communication in multicellular organisms. The importance of this process has been revealed by the discovery of the prominent oncogenic properties of tyrosine kinases (TK) upon deregulation of their physiological activities, often due to protein overexpression and/or somatic mutation. Recent reports suggest that TK oncogenic signaling is also under the control of small adaptor proteins. These cytosolic proteins lack intrinsic catalytic activity and signal by linking two functional members of a catalytic pathway. While most adaptors display positive regulatory functions, a small group of this family exerts negative regulatory functions by targeting several components of the TK signaling cascade. Here, we review how these less studied adaptor proteins negatively control TK activities and how their loss of function induces abnormal TK signaling, promoting tumor formation. We also discuss the therapeutic consequences of this novel regulatory mechanism in human oncology.

ABL tyrosine kinase inhibition variable effects on the invasive properties of different triple negative breast cancer cell lines.

The non-receptor tyrosine kinase ABL drives myeloid progenitor expansion in human chronic myeloid leukemia. ABL inhibition by the tyrosine kinase inhibitor nilotinib is a first-line treatment for this disease. Recently, ABL has also been implicated in the transforming properties of solid tumors, including triple negative (TN) breast cancer. TN breast cancers are highly metastatic and several cell lines derived from these tumors display high invasive activity in vitro. This feature is associated with the activation of actin-rich membrane structures called invadopodia that promote extracellular matrix degradation. Here, we investigated nilotinib effect on the invasive and migratory properties of different TN breast cancer cell lines. Nilotinib decreased both matrix degradation and invasion in the TN breast cancer cell lines MDA-MB 231 and MDA-MB 468. However, and unexpectedly, nilotinib increased by two-fold the invasive properties of the TN breast cancer cell line BT-549 and of Src-transformed fibroblasts. Both display much higher levels of ABL kinase activity compared to MDA-MB 231. Similar effects were obtained by siRNA-mediated down-regulation of ABL expression, confirming ABL central role in this process. ABL anti-tumor effect in BT-549 cells and Src-transformed fibroblasts was not dependent on EGF secretion, as recently reported in neck and squamous carcinoma cells. Rather, we identified the TRIO-RAC1 axis as an important downstream element of ABL activity in these cancer cells. In conclusion, the observation that TN breast cancer cell lines respond differently to ABL inhibitors could have implications for future therapies.