Risk of antiangiogenic adverse events in metastatic colorectal cancer patients receiving aflibercept in combination with chemotherapy: A meta-analysis.

BACKGROUND: Aflibercept has been approved for the treatment of metastatic colorectal cancer for more than a decade, but its antiangiogenesis adverse effect profile during treatment remains unclear. This study is conducted to systematically review the risk of antiangiogenic adverse events in patients with metastatic colorectal cancer receiving aflibercept plus chemotherapy. METHODS: We searched databases, including PubMed, Embase and the Cochrane Library up to September 9, 2021. Relevant randomized controlled trials (RCTs) and single-arm studies were included in the review. Statistical analyses were performed using R to calculate the summary incidence rate of antiangiogenic-related adverse events, odds ratios and 95% CIs. Heterogeneity among the included studies was assessed by subgroup analysis. Publication bias analysis and sensitivity analysis were performed to confirm the reliability of the results. RESULTS: A total of 2889 patients from 10 studies met the inclusion criteria. The quality of the included studies was evaluated as qualified for further quantitative synthesis. In part of single-arm studies, the occurrence rates were 44.2% (95%CI, 39.7-48.7%) for hypertension, 31.3% (95% CI, 19.3-43.3%) for proteinuria, 27.3% (95%CI, 21.2-33.4%) for epistaxis, 22.5% (95%CI, 7.8-37.3%) for hemorrhage events, 8.0% (95%CI, 2.0-14 .0%) for venous thromboembolic event in all grades and 22.6% (95%CI, 19.1-26.2%) for grade III/IV hypertension, 7.4% (95%CI, 6.2-8.5%) for grade III/IV proteinuria. In part of RCT, compared to its counterpart, aflibercept containing arm was associated with the increased incidence rate in hypertension (OR:6.30, 95%CI: 3.49-11.36), proteinuria (OR:4.12, 95%CI: 1.25-13.61), epistaxis (OR:3.71, 95%CI: 2.84-4.85), III/IV hypertension (OR:7.20, 95%CI: 5.23-9.92), III/IV proteinuria (OR:5.13, 95%CI: 3.13-8.41). The funnel plot, Begg test and Egger test were carried out on the primary endpoints, III/IV hypertension rate and III/IV proteinuria rate, the result of which detected no obvious publication bias. No significant difference was observed in subgroup analysis in the primary endpoint between the subgroups stratified by treatment line (firstline or non-firstline), chemotherapy regime (FOLFIRI or others) and study design (RCTs or single-arm trials). CONCLUSION: The available evidence suggests that using aflibercept is associated with an increased risk of antiangiogenic adverse events compared with controls. Further studies are needed to investigate this association. In the appropriate clinical scenario, the use of aflibercept in its approved indications remains justified. However, the results of this study should be interpreted with caution, as some of the evidence comes from single-arm clinical trials.

FMRP-dependent Mdm2 dephosphorylation is required for MEF2-induced synapse elimination.

The Myocyte Enhancer Factor 2 (MEF2) transcription factors suppress an excitatory synapse number by promoting degradation of the synaptic scaffold protein, postsynaptic density protein 95 (PSD-95), a process that is deficient in the mouse model of Fragile X Syndrome, Fmr1 KO. How MEF2 activation results in PSD-95 degradation and why this is defective in Fmr1 KO neurons is unknown. Here we report that MEF2 induces a Protein phosphatase 2A (PP2A)-mediated dephosphorylation of murine double minute-2 (Mdm2), the ubiquitin E3 ligase for PSD-95, which results in nuclear export and synaptic accumulation of Mdm2 as well as PSD-95 degradation and synapse elimination. In Fmr1 KO neurons, Mdm2 is hyperphosphorylated, nuclear localized basally, and unaffected by MEF2 activation, which our data suggest due to an enhanced interaction with Eukaryotic Elongation Factor 1α (EF1α), whose protein levels are elevated in Fmr1 KO. Expression of a dephosphomimetic of Mdm2 rescues PSD-95 ubiquitination, degradation and synapse elimination in Fmr1 KO neurons. This work reveals detailed mechanisms of synapse elimination in health and a developmental brain disorder.

Increased Metabotropic Glutamate Receptor 5 Signaling Underlies Obsessive-Compulsive Disorder-like Behavioral and Striatal Circuit Abnormalities in Mice.

BACKGROUND: Development of treatments for obsessive-compulsive disorder (OCD) is hampered by a lack of mechanistic understanding about this prevalent neuropsychiatric condition. Although circuit changes such as elevated frontostriatal activity are linked to OCD, the underlying molecular signaling that drives OCD-related behaviors remains largely unknown. Here, we examine the significance of type 5 metabotropic glutamate receptors (mGluR5s) for behavioral and circuit abnormalities relevant to OCD. METHODS: Sapap3 knockout (KO) mice treated acutely with an mGluR5 antagonist were evaluated for OCD-relevant phenotypes of self-grooming, anxiety-like behaviors, and increased striatal activity. The role of mGluR5 in the striatal circuit abnormalities of Sapap3 KO mice was further explored using two-photon calcium imaging to monitor striatal output from the direct and indirect pathways. A contribution of constitutive signaling to increased striatal mGluR5 activity in Sapap3 KO mice was investigated using pharmacologic and biochemical approaches. Finally, sufficiency of mGluR5 to drive OCD-like behavior in wild-type mice was tested by potentiating mGluR5 with a positive allosteric modulator. RESULTS: Excessive mGluR5 signaling underlies OCD-like behaviors and striatal circuit abnormalities in Sapap3 KO mice. Accordingly, enhancing mGluR5 activity acutely recapitulates these behavioral phenotypes in wild-type mice. In Sapap3 KO mice, elevated mGluR5 signaling is associated with constitutively active receptors and increased and imbalanced striatal output that is acutely corrected by antagonizing striatal mGluR5. CONCLUSIONS: These findings demonstrate a causal role for increased mGluR5 signaling in driving striatal output abnormalities and behaviors with relevance to OCD and show the tractability of acute mGluR5 inhibition to remedy circuit and behavioral abnormalities.

Selective Disruption of Metabotropic Glutamate Receptor 5-Homer Interactions Mimics Phenotypes of Fragile X Syndrome in Mice.

Altered function of the Gq-coupled, Group 1 metabotropic glutamate receptors, specifically mGlu5, is implicated in multiple mouse models of autism and intellectual disability. mGlu5 dysfunction has been most well characterized in the fragile X syndrome mouse model, the Fmr1 knock-out (KO) mouse, where pharmacological and genetic reduction of mGlu5 reverses many phenotypes. mGlu5 is less associated with its scaffolding protein Homer in Fmr1 KO mice, and restoration of mGlu5-Homer interactions by genetic deletion of a short, dominant negative of Homer, H1a, rescues many phenotypes of Fmr1 KO mice. These results suggested that disruption of mGlu5-Homer leads to phenotypes of FXS. To test this idea, we examined mice with a knockin mutation of mGlu5 (F1128R; mGlu5(R/R)) that abrogates binding to Homer. Although FMRP levels were normal, mGlu5(R/R) mice mimicked multiple phenotypes of Fmr1 KO mice, including reduced mGlu5 association with the postsynaptic density, enhanced constitutive mGlu5 signaling to protein synthesis, deficits in agonist-induced translational control, protein synthesis-independent LTD, neocortical hyperexcitability, audiogenic seizures, and altered behaviors, including anxiety and sensorimotor gating. These results reveal new roles for the Homer scaffolds in regulation of mGlu5 function and implicate a specific molecular mechanism in a complex brain disease. SIGNIFICANCE STATEMENT: Abnormal function of the metabotropic, or Gq-coupled, glutamate receptor 5 (mGlu5) has been implicated in neurodevelopmental disorders, including a genetic cause of intellectual disability and autism called fragile X syndrome. In brains of a mouse model of fragile X, mGlu5 is less associated with its binding partner Homer, a scaffolding protein that regulates mGlu5 localization to synapses and its ability to activate biochemical signaling pathways. Here we show that a mouse expressing a mutant mGlu5 that cannot bind to Homer is sufficient to mimic many of the biochemical, neurophysiological, and behavioral symptoms observed in the fragile X mouse. This work provides strong evidence that Homer-mGlu5 binding contributes to symptoms associated with neurodevelopmental disorders.

Elevated CaMKIIα and Hyperphosphorylation of Homer Mediate Circuit Dysfunction in a Fragile X Syndrome Mouse Model.

Abnormal metabotropic glutamate receptor 5 (mGluR5) function, as a result of disrupted scaffolding with its binding partner Homer, contributes to the pathophysiology of fragile X syndrome, a common inherited form of intellectual disability and autism caused by mutations in Fmr1. How loss of Fmr1 disrupts mGluR5-Homer scaffolds is unknown, and little is known about the dynamic regulation of mGluR5-Homer scaffolds in wild-type neurons. Here, we demonstrate that brief (minutes-long) elevations in neural activity cause CaMKIIα-mediated phosphorylation of long Homer proteins and dissociation from mGluR5 at synapses. In Fmr1 knockout (KO) cortex, Homers are hyperphosphorylated as a result of elevated CaMKIIα protein. Genetic or pharmacological inhibition of CaMKIIα or replacement of Homers with dephosphomimetics restores mGluR5-Homer scaffolds and multiple Fmr1 KO phenotypes, including circuit hyperexcitability and/or seizures. This work links translational control of an FMRP target mRNA, CaMKIIα, to the molecular-, cellular-, and circuit-level brain dysfunction in a complex neurodevelopmental disorder.

Multiple autism-linked genes mediate synapse elimination via proteasomal degradation of a synaptic scaffold PSD-95.

The activity-dependent transcription factor myocyte enhancer factor 2 (MEF2) induces excitatory synapse elimination in mouse neurons, which requires fragile X mental retardation protein (FMRP), an RNA-binding protein implicated in human cognitive dysfunction and autism. We report here that protocadherin 10 (Pcdh10), an autism-spectrum disorders gene, is necessary for this process. MEF2 and FMRP cooperatively regulate the expression of Pcdh10. Upon MEF2 activation, PSD-95 is ubiquitinated by the ubiquitin E3 ligase murine double minute 2 (Mdm2) and then binds to Pcdh10, which links it to the proteasome for degradation. Blockade of the Pcdh10-proteasome interaction inhibits MEF2-induced PSD-95 degradation and synapse elimination. In FMRP-lacking neurons, elevated protein levels of eukaryotic translation elongation factor 1 α (EF1α), an Mdm2-interacting protein and FMRP target mRNA, sequester Mdm2 and prevent MEF2-induced PSD-95 ubiquitination and synapse elimination. Together, our findings reveal roles for multiple autism-linked genes in activity-dependent synapse elimination.

Disrupted Homer scaffolds mediate abnormal mGluR5 function in a mouse model of fragile X syndrome.

Enhanced metabotropic glutamate receptor subunit 5 (mGluR5) function is causally associated with the pathophysiology of fragile X syndrome, a leading inherited cause of intellectual disability and autism. Here we provide evidence that altered mGluR5-Homer scaffolds contribute to mGluR5 dysfunction and phenotypes in the fragile X syndrome mouse model, Fmr1 knockout (Fmr1(-/y)). In Fmr1(-/y) mice, mGluR5 was less associated with long Homer isoforms but more associated with the short Homer1a. Genetic deletion of Homer1a restored mGluR5-long Homer scaffolds and corrected several phenotypes in Fmr1(-/y) mice, including altered mGluR5 signaling, neocortical circuit dysfunction and behavior. Acute, peptide-mediated disruption of mGluR5-Homer scaffolds in wild-type mice mimicked many Fmr1(-/y) phenotypes. In contrast, Homer1a deletion did not rescue altered mGluR-dependent long-term synaptic depression or translational control of target mRNAs of fragile X mental retardation protein, the gene product of Fmr1. Our findings reveal new functions for mGluR5-Homer interactions in the brain and delineate distinct mechanisms of mGluR5 dysfunction in a mouse model of cognitive dysfunction and autism.

An ALS-associated mutation affecting TDP-43 enhances protein aggregation, fibril formation and neurotoxicity.

Mutations in TARDBP, encoding TAR DNA-binding protein-43 (TDP-43), are associated with TDP-43 proteinopathies, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). We compared wild-type TDP-43 and an ALS-associated mutant TDP-43 in vitro and in vivo. The A315T mutant enhances neurotoxicity and the formation of aberrant TDP-43 species, including protease-resistant fragments. The C terminus of TDP-43 shows sequence similarity to prion proteins. Synthetic peptides flanking residue 315 form amyloid fibrils in vitro and cause neuronal death in primary cultures. These data provide evidence for biochemical similarities between TDP-43 and prion proteins, raising the possibility that TDP-43 derivatives may cause spreading of the disease phenotype among neighboring neurons. Our work also suggests that decreasing the abundance of neurotoxic TDP-43 species, enhancing degradation or clearance of such TDP-43 derivatives and blocking the spread of the disease phenotype may have therapeutic potential for TDP-43 proteinopathies.

A Drosophila model for TDP-43 proteinopathy.

Neuropathology involving TAR DNA binding protein-43 (TDP-43) has been identified in a wide spectrum of neurodegenerative diseases collectively named as TDP-43 proteinopathy, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar dementia (FTLD). To test whether increased expression of wide-type human TDP-43 (hTDP-43) may cause neurotoxicity in vivo, we generated transgenic flies expressing hTDP-43 in various neuronal subpopulations. Expression in the fly eyes of the full-length hTDP-43, but not a mutant lacking its amino-terminal domain, led to progressive loss of ommatidia with remarkable signs of neurodegeneration. Expressing hTDP-43 in mushroom bodies (MBs) resulted in dramatic axon losses and neuronal death. Furthermore, hTDP-43 expression in motor neurons led to axon swelling, reduction in axon branches and bouton numbers, and motor neuron loss together with functional deficits. Thus, our transgenic flies expressing hTDP-43 recapitulate important neuropathological and clinical features of human TDP-43 proteinopathy, providing a powerful animal model for this group of devastating diseases. Our study indicates that simply increasing hTDP-43 expression is sufficient to cause neurotoxicity in vivo, suggesting that aberrant regulation of TDP-43 expression or decreased clearance of hTDP-43 may contribute to the pathogenesis of TDP-43 proteinopathy.