XPO1 Enables Adaptive Regulation of mRNA Export Required for Genotoxic Stress Tolerance in Cancer Cells

Exportin-1 (XPO1), the main soluble nuclear export receptor in eukaryotic cells, is frequently overexpressed in diffuse large B-cell lymphoma (DLBCL). A selective XPO1 inhibitor, selinexor, received approval as single agent for relapsed or refractory (R/R) DLBCL. Elucidating the mechanisms by which XPO1 overexpression supports cancer cells could facilitate further clinical development of XPO1 inhibitors. We uncovered here that XPO1 overexpression increases tolerance to genotoxic stress, leading to a poor response to chemoimmunotherapy. Upon DNA damage induced by MYC expression or exogenous compounds, XPO1 bound and exported EIF4E and THOC4 carrying DNA damage repair mRNAs, thereby increasing synthesis of DNA damage repair proteins under conditions of increased turnover. Consequently, XPO1 inhibition decreased the capacity of lymphoma cells to repair DNA damage and ultimately resulted in increased cytotoxicity. In a phase I clinical trial conducted in R/R DLBCL, the combination of selinexor with second-line chemoimmunotherapy was tolerated with early indication of efficacy. Overall, this study reveals that XPO1 overexpression plays a critical role in the increased tolerance of cancer cells to DNA damage while providing new insights to optimize the clinical development of XPO1 inhibitors.

SIGNIFICANCE

XPO1 regulates the dynamic ribonucleoprotein nuclear export in response to genotoxic stress to support tolerance and can be targeted to enhance the sensitivity of cancer cells to endogenous and exogenous DNA damage. See related commentary by Knittel and Reinhardt, p. 3.

Endothelial cell-leukemia interactions remodel drug responses, uncovering T-ALL vulnerabilities

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive and often incurable disease. To uncover therapeutic vulnerabilities, we first developed T-ALL patient-derived tumor xenografts (PDXs) and exposed PDX cells to a library of 433 clinical-stage compounds in vitro. We identified 39 broadly active drugs with antileukemia activity. Because endothelial cells (ECs) can alter drug responses in T-ALL, we developed an EC/T-ALL coculture system. We found that ECs provide protumorigenic signals and mitigate drug responses in T-ALL PDXs. Whereas ECs broadly rescued several compounds in most models, for some drugs the rescue was restricted to individual PDXs, suggesting unique crosstalk interactions and/or intrinsic tumor features. Mechanistically, cocultured T-ALL cells and ECs underwent bidirectional transcriptomic changes at the single-cell level, highlighting distinct "education signatures." These changes were linked to bidirectional regulation of multiple pathways in T-ALL cells as well as in ECs. Remarkably, in vitro EC-educated T-ALL cells transcriptionally mirrored ex vivo splenic T-ALL at single-cell resolution. Last, 5 effective drugs from the 2 drug screenings were tested in vivo and shown to effectively delay tumor growth and dissemination thus prolonging overall survival. In sum, we developed a T-ALL/EC platform that elucidated leukemia-microenvironment interactions and identified effective compounds and therapeutic vulnerabilities.

Abstract A28: BCL10 mutations define distinct dependencies guiding precision therapy for DLBCL

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoid malignancy and the activated B cell-like subtype (ABC-DLBCL) is the most aggressive form and harbors frequent mutations of immune signaling pathways that culminate in constitutive activation of CARD11-MALT1-BCL10 (CBM) complex and downstream NF-κB pathway. CBM complexes form large macromolecular structures due to signal-induced polymerization of the BCL10 subunit, which is affected by recurrent somatic mutations in ABC-DLBCLs. Through biochemical, structural and functional dissection of these mutations, we find that BCL10 mutations fall into two functionally distinct classes: missense mutations of the BCL10 CARD domain (hotspot R58Q) and truncation of its C-terminal tail (hotspot E140X). To explore the functional consequences of BCL10 mutations, we established reporter systems to evaluate their impact on MALT1 and NF-𝜅B activities which are BCL10 downstream signaling cascades. We found that almost all mutants induced aberrantly strong NF-𝜅B and MALT1 activities in lymphoma cells as compared to WT BCL10, indicating the gain-of-function effect of BCL10 mutations. By performing immunohistochemistry staining of p65 in a set of tumor tissue microarray from DLBCL patients (n=298), we revealed that BCL10 mutant tumors have significantly (Mann-Whitney p<0.0001) increased p65 nuclear staining score compared to BCL10 WT tumors, suggesting enhanced NF-𝜅B activity. To investigate the biochemical impact of BCL10 mutants on CBM complex formation, we performed fluorescence polarization and filamentation formation assays with purified WT and mutant BCL10 proteins and found that both BCL10R58Q and BCL10E140X manifested faster and more spontaneous polarization compared to BCL10WT. Surprisingly, through mapping the BCL10-MALT1 interaction, we found that truncating mutation (E140X) abrogated a novel protein interaction motif through which MALT1 inhibits BCL10 polymerization, thus unleashing spontaneous CBM filament formation and inducing addiction to MALT1 activity. In marked contrast, the CARD missense mutation (R58Q) on BCL10 filament interface not only does not disrupt but enhances filament formation and it also alters CBM complex kinetics forming glutamine network structures that stabilize BCL10 filaments, but this still may require the upstream signal to activate MALT1. Importantly, we found that BCL10 mutant cells were less dependent on upstream CARD11 activation in MALT1 activation, NF-𝜅B signaling and cell growth assays performed in ABC-DLBCL lines. Furthermore, in vitro and in vivo xenograft studies revealed that BCL10 mutant lymphomas are resistant to BTK inhibitors, whereas BCL10 truncating (E140X) but not missense CARD (R58Q) mutants were hypersensitive to MALT1 protease inhibitors. Therefore, BCL10 mutations are potential biomarkers for BTK inhibitor resistance in ABC-DLBCL and further precision can be achieved by tailoring therapy (e.g. MALT1 inhibitors that are currently being tested in clinical trials) according to specific biochemical effects of distinct mutation classes.

Citation Format: Min Xia, Liron David, Matthew R Teater, Johana Gutierrez, Xiang Wang, Cem Meydan, Andrew Lytle, Graham Slack, David Scott, Ozlem Onder, Kojo Elenitoba-Johnson, Nahuel Zamponi, Leandro Cerchietti, Tianbao Lu, Ulrike Philippar, Lorena Fontan, Hao Wu, Ari Melnick. BCL10 mutations define distinct dependencies guiding precision therapy for DLBCL [abstract]. In: Proceedings of the Third AACR International Meeting: Advances in Malignant Lymphoma: Maximizing the Basic-Translational Interface for Clinical Application; 2022 Jun 23-26; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2022;3(5_Suppl):Abstract nr A28.

BCL10 Mutations Define Distinct Dependencies Guiding Precision Therapy for DLBCL

Activated B cell-like diffuse large B-cell lymphomas (ABC-DLBCL) have unfavorable outcomes and chronic activation of CARD11-BCL10-MALT1 (CBM) signal amplification complexes that form due to polymerization of BCL10 subunits, which is affected by recurrent somatic mutations in ABC-DLBCLs. Herein, we show that BCL10 mutants fall into at least two functionally distinct classes: missense mutations of the BCL10 CARD domain and truncation of its C-terminal tail. Truncating mutations abrogated a motif through which MALT1 inhibits BCL10 polymerization, trapping MALT1 in its activated filament-bound state. CARD missense mutations enhanced BCL10 filament formation, forming glutamine network structures that stabilize BCL10 filaments. Mutant forms of BCL10 were less dependent on upstream CARD11 activation and thus manifested resistance to BTK inhibitors, whereas BCL10 truncating but not CARD mutants were hypersensitive to MALT1 inhibitors. Therefore, BCL10 mutations are potential biomarkers for BTK inhibitor resistance in ABC-DLBCL, and further precision can be achieved by selecting therapy based on specific biochemical effects of distinct mutation classes.

SIGNIFICANCE

ABC-DLBCLs feature frequent mutations of signaling mediators that converge on the CBM complex. We use structure-function approaches to reveal that BCL10 mutations fall into two distinct biochemical classes. Both classes confer resistance to BTK inhibitors, whereas BCL10 truncations confer hyperresponsiveness to MALT1 inhibitors, providing a road map for precision therapies in ABC-DLBCLs. See related commentary by Phelan and Oellerich, p. 1844. This article is highlighted in the In This Issue feature, p. 1825.

Inhibition of integrin αVβ3 signaling improves the antineoplastic effect of bexarotene in cutaneous T-cell lymphoma

Bexarotene is a specific RXR agonist that has been used for the treatment of cutaneous T-cell lymphoma (CTCL). Since bexarotene causes hypothyroidism, it requires the administration of levothyroxine. However, levothyroxine, in addition to its ubiquitous nuclear receptors, can activate the αVβ3 integrin that is overexpressed in CTCL, potentially interfering the antineoplastic effect of bexarotene. We thus investigated the biological effect of levothyroxine in relation to bexarotene treatment. Although in isolated CTCL cells levothyroxine decreased, in an αVβ3 -dependent manner, the antineoplastic effect of bexarotene; levothyroxine supplementation in pre-clinical models was necessary to avoid suppression of lymphoma immunity. Accordingly, selective genetic and pharmacologic inhibition of integrin αVβ3 3 improved the antineoplastic effect of bexarotene plus levothyroxine replacement while maintaining lymphoma immunity. Our results provide a mechanistic rationale for clinical testing of integrin αVβ3 inhibitors as part of CTCL regimens based on bexarotene administration.

Oncogenic HSP90 Facilitates Metabolic Alterations in Aggressive B-cell Lymphomas

HSP90 is critical for maintenance of the cellular proteostasis. In cancer cells, HSP90 also becomes a nucleating site for the stabilization of multiprotein complexes including signaling pathways and transcription complexes. Here we described the role of this HSP90 form, referred to as oncogenic HSP90, in the regulation of cytosolic metabolic pathways in proliferating B-cell lymphoma cells. Oncogenic HSP90 assisted in the organization of metabolic enzymes into non-membrane-bound functional compartments. Under experimental conditions that conserved cellular proteostasis, oncogenic HSP90 coordinated and sustained multiple metabolic pathways required for energy production and maintenance of cellular biomass as well as for secretion of extracellular metabolites. Conversely, inhibition of oncogenic HSP90, in absence of apparent client protein degradation, decreased the efficiency of MYC-driven metabolic reprogramming. This study reveals that oncogenic HSP90 supports metabolism in B-cell lymphoma cells and patients with diffuse large B-cell lymphoma, providing a novel mechanism of activity for HSP90 inhibitors. SIGNIFICANCE: The oncogenic form of HSP90 organizes and maintains functional multienzymatic metabolic hubs in cancer cells, suggesting the potential of repurposing oncogenic HSP90 selective inhibitors to disrupt metabolism in lymphoma cells.

Deep brain stimulation in patients with long history of drug resistant epilepsy and poor functional status: Outcomes based on the different targets

BACKGROUND

Deep brain stimulation (DBS) is a widely used surgical procedure for the treatment of patients with drug resistant epilepsy (DRE) and several anatomical target have been described. Indications for DBS includes patients with focal, partial seizure and those for which resective or disconnective surgery are contraindicated, such as involvement of eloquent cortex or significant comorbidities. Despite the SANTE trial has clearly indicated the efficacy of DBS of anterior nucleus of the thalamus (ANT), specific indications regarding the best anatomical target and outcome in patients with severe disability are lacking. Here we described our case series of patients underwent DBS of three different target including ANT, centromedian thalamic nucleus (CMN) and subthalamic nucleus (STN).

METHOD

Six patients with DRE have been treated with DBS of ANT (n = 3), STN (n = 2) and CMN (n = 1). Outcome has been expressed as seizures frequency reduction and patients functional status after surgery with a follow-up of 5-11 years.

RESULTS

Four out of six patients show no reduction of seizures frequency after DBS implant with one case of increasing atypical absence. Two cases, one ANT and one CMN, show a significant reduction of seizures frequency of 50-60%. No patients improve relative to functional outcome and one showed psychiatric symptoms worsening.

CONCLUSIONS

For patients with DRE and severe functional disability, DBS may reduce seizure frequency in some cases, but it does not improve functional outcome.

Fractional re-distribution among cell motility states during ageing

Ageing in humans is associated with the decreased capacity to regulate cell physiology. Cellular properties, such as cell morphology and mechanics, encode ageing information, and can therefore be used as robust biomarkers of ageing. Using a panel of dermal fibroblasts derived from healthy donors spanning a wide age range, we observe an age-associated decrease in cell motility. By taking advantage of the single-cell nature of our motility data, we classified cells based on spatial and activity patterns to define age-dependent motility states. We show that the age-dependent decrease in cell motility is not due to the reduced motility of all cells, but results from the fractional re-distribution among motility states. These findings highlight an important feature of ageing cells characterized by a reduction of cellular heterogeneity in older adults relative to post-adolescent/adults. Furthermore, these results point to a mechanistic framework of ageing, with potential applications in deciphering emergent ageing phenotypes and biomarker development.

Nrf2 stabilization prevents critical oxidative damage in Down syndrome cells

Mounting evidence implicates chronic oxidative stress as a critical driver of the aging process. Down syndrome (DS) is characterized by a complex phenotype, including early senescence. DS cells display increased levels of reactive oxygen species (ROS) and mitochondrial structural and metabolic dysfunction, which are counterbalanced by sustained Nrf2-mediated transcription of cellular antioxidant response elements (ARE). Here, we show that caspase 3/PKCδdependent activation of the Nrf2 pathway in DS and Dp16 (a mouse model of DS) cells is necessary to protect against chronic oxidative damage and to preserve cellular functionality. Mitochondria-targeted catalase (mCAT) significantly reduced oxidative stress, restored mitochondrial structure and function, normalized replicative and wound healing capacity, and rendered the Nrf2-mediated antioxidant response dispensable. These results highlight the critical role of Nrf2/ARE in the maintenance of DS cell homeostasis and validate mitochondrial-specific interventions as a key aspect of antioxidant and antiaging therapies.

Effectiveness and tolerability of perampanel in children and adolescents with refractory epilepsies-An Italian observational multicenter study

PURPOSE

To evaluate the efficacy and tolerability of Perampanel (PER) in children and adolescents with refractory epilepsies in daily clinical practice conditions.

PATIENTS AND METHODS

This Italian multicenter retrospective observational study was performed in 16 paediatric epilepsy centres. Inclusion criteria were: (i) ≤18 years of age, (ii) history of refractory epilepsy, (iii) a follow-up ≥5 months of PER add-on therapy. Exclusion criteria were: (i) a diagnosis of primary idiopathic generalized epilepsy, (ii) variation of concomitant AEDs during the previous 4 weeks. Response was defined as a ≥50% reduction in monthly seizure frequency compared with the baseline.

RESULTS

62 patients suffering from various refractory epilepsies were included in this study: 53% were males, the mean age was 14.2 years (range 6-18 years), 8 patients aged <12 years. Mean age at epilepsy onset was 3.4 years and the mean duration of epilepsy was 10.8 years (range 1-16), which ranged from 2 seizures per-month up to several seizures per-day (mean number=96.5). Symptomatic focal epilepsy was reported in 62.9% of cases. Mean number of AEDs used in the past was 7.1; mean number of concomitant AEDs was 2.48, with carbamazepine used in 43.5% of patients. Mean PER daily dose was 7.1mg (2-12mg). After an average of 6.6 months of follow-up (5-13 months), the retention rate was 77.4% (48/62). The response rate was 50%; 16% of patients achieved ≥75% seizure frequency reduction and 5% became completely seizure free. Seizure aggravation was observed in 9.7% of patients. Adverse events were reported in 19 patients (30.6%) and led to PER discontinuation in 4 patients (6.5%). The most common adverse events were behaviour disturbance (irritability and aggressiveness), dizziness, sedation and fatigue.

CONCLUSION

PER was found to be a safe and effective treatment when used as adjunctive therapy in paediatric patients with uncontrolled epilepsy.

Leigh Syndrome: An MR Study of Three Cases

Leigh syndrome (LS), or subacute necrotizing encephalomyelopathy, is the most common childhood mitochondrial encephalopathy, accounting for more than 50% of cases in this age group. Its estimated incidence is 1:40,000 – 1:77,000 liveborn infants a year. LS is a rare progressive multisystem fatal disorder inherited by autosomal recessive, X-linked and maternal transmission. Clinical onset is predominantly in the first two years of life (average: six months); 50% of patients die within a year, even though there are later- and even adult-onset forms with a more protracted evolution. LS is due to a deficit of various respiratory chain and Krebs cycle enzymes resulting in insufficient production of adenosine triphosphate (ATP), in particular cytochrome-c-oxidase (COX), pyruvate carboxylase, pyruvate dehydrogenase complex and complex I of the respiratory chain, which share an autosomal recessive and X-linked mode of transmission. Cases with maternal inheritance (MILS) are due to a mitochondrial DNA (mtDNA) point mutation. LS is clinically heterogeneous in relation to the severity of the metabolic dysfunction and is characterized by muscle involvement and especially CNS disorders, particularly psychomotor retardation, ocular symptoms, hypotonia and pyramidal signs. Death is most commonly due to respiratory failure, status epilepticus and sudden coma. The major neuropathological findings, first described by Leigh in 1951, are symmetrical foci of spongy necrosis associated with vessel proliferation and reactive gliosis in basal nuclei, brainstem and thalamus grey matter. The neuronal metabolic alteration can also affect the white matter, resulting in delayed myelination or hypomyelination. The diagnosis rests on clinical signs, elevated CSF lactate, pyruvate and alanine, and biochemical and neuroradiological data. We describe two patients with LS studied with morphological MR associated with diffusion and spectroscopy techniques to assess the diagnostic potential of standard MR imaging and establish whether the association of functional MR methods can improve its diagnostic accuracy. A case of LS with a post-mortem MR study is also described. Three patients with a diagnosis of LS based on clinical, CSF and laboratory data were studied on a GE SIGNA EXCITE 1.5 T unit using an eight-channel phased-array head coil to acquire standard sequences (SE T1; TSE DP T2; FLAIR) and echo-planar diffusion-weighted sequences (DWI; b= 1000 s/mm2) with calculation of ADC maps. The spectroscopic study used single-voxel (TE/TR ms ? 144/1500) and multi-voxel techniques (TE/TR ms = 144/1000) at the level of the basal nuclei. Bilateral and symmetrical involvement of basal nuclei grey matter with T2 hyperintensity was a consistent finding in the morphological MR study. In one patient, associated white matter involvement with T2 hyperintensity in periventricular and retrotrigonal areas reflected delayed myelination or hypomyelination. The deep grey matter changes, sometimes associated with white matter lesions, suggested a diagnosis of subacute necrotizing encephalomyelopathy, in line with the literature. Acute-phase ADC values in affected areas were lower than those of normal grey and white matter and displayed signal hyperintensity on DWI. Reduced ADC values are associated with restricted water diffusivity typical of cytotoxic edema. Spectroscopy showed a high lactate peak, reflecting altered anaerobic glycolysis, and a reduced NAA peak in affected areas, which are however non-specific findings. The most informative study in these patients is standard MR associated with functional techniques, which can confirm the diagnosis obtained with morphological imaging.

Clinical dissection of childhood occipital epilepsy of Gastaut and prognostic implication

BACKGROUND AND PURPOSE

Our aim was to describe the clinical and electrical features and the long-term evolution of childhood occipital epilepsy of Gastaut (COE-G) in a cohort of patients and to compare long-term prognosis between patients with and without other epileptic syndromes.

METHODS

This was a retrospective analysis of the long-term outcome of epilepsy in 129 patients with COE-G who were referred to 23 Italian epilepsy centres and one in Austria between 1991 and 2004. Patients were evaluated clinically and with electroencephalograms for 10.1-23.0 years. The following clinical characteristics were evaluated: gender, patient age at seizure onset, history of febrile seizures and migraine, family history of epilepsy, duration and seizure manifestations, circadian distribution and frequency of seizures, history of medications including the number of drugs, therapeutic response and final outcome.

RESULTS

Visual hallucinations were the first symptom in 62% and the only manifestation in 38.8% of patients. Patients were subdivided into two groups: group A with isolated COE-G; group B with other epileptic syndromes associated with COE-G. The most significant (P < 0.05) difference concerned antiepileptic therapy: in group A, 45 children responded to monotherapy; in group B only 15 children responded to monotherapy. At the end of follow-up, the percentage of seizure-free patients was significantly higher in group A than in group B.

CONCLUSIONS

Childhood occipital epilepsy of Gastaut has an overall favourable prognosis and a good response to antiepileptic therapy with resolution of seizures and of electroencephalogram abnormalities. The association of typical COE-G symptoms with other types of seizure could be related to a poor epilepsy outcome.

The giardial ENTH protein participates in lysosomal protein trafficking and endocytosis

In the protozoa parasite Giardia lamblia, endocytosis and lysosomal protein trafficking are vital parasite-specific processes that involve the action of the adaptor complexes AP-1 and AP-2 and clathrin. In this work, we have identified a single gene in Giardia encoding a protein containing an ENTH domain that defines monomeric adaptor proteins of the epsin family. This domain is present in the epsin or epsin-related (epsinR) adaptor proteins, which are implicated in endocytosis and Golgi-to-endosome protein trafficking, respectively, in other eukaryotic cells. We found that GlENTHp (for G. lamblia ENTH protein) localized in the cytosol, strongly interacted with PI3,4,5P3, was associated with the alpha subunit of AP-2, clathrin and ubiquitin and was involved in receptor-mediated endocytosis. It also bonded PI4P, the gamma subunit of AP-1 and was implicated in ER-to-PV trafficking. Alteration of the GlENTHp function severely affected trophozoite growth showing an unusual accumulation of dense material in the lysosome-like peripheral vacuoles (PVs), indicating that GlENTHp might be implicated in the maintenance of PV homeostasis. In this study, we showed evidence suggesting that GlENTHp might function as a monomeric adaptor protein supporting the findings of other group indicating that GlENTHp might be placed at the beginning of the ENTH family.

Identification of Giardia lamblia DHHC proteins and the role of protein S-palmitoylation in the encystation process

Protein S-palmitoylation, a hydrophobic post-translational modification, is performed by protein acyltransferases that have a common DHHC Cys-rich domain (DHHC proteins), and provides a regulatory switch for protein membrane association. In this work, we analyzed the presence of DHHC proteins in the protozoa parasite Giardia lamblia and the function of the reversible S-palmitoylation of proteins during parasite differentiation into cyst. Two specific events were observed: encysting cells displayed a larger amount of palmitoylated proteins, and parasites treated with palmitoylation inhibitors produced a reduced number of mature cysts. With bioinformatics tools, we found nine DHHC proteins, potential protein acyltransferases, in the Giardia proteome. These proteins displayed a conserved structure when compared to different organisms and are distributed in different monophyletic clades. Although all Giardia DHHC proteins were found to be present in trophozoites and encysting cells, these proteins showed a different intracellular localization in trophozoites and seemed to be differently involved in the encystation process when they were overexpressed. dhhc transgenic parasites showed a different pattern of cyst wall protein expression and yielded different amounts of mature cysts when they were induced to encyst. Our findings disclosed some important issues regarding the role of DHHC proteins and palmitoylation during Giardia encystation.

Giardiasis is a major cause of non-viral/non-bacterial diarrheal disease worldwide and has been included within the WHO Neglected Disease Initiative since 2004. Infection begins with the ingestion of Giardia lamblia in cyst form, which, after exposure to gastric acid in the host stomach and proteases in the duodenum, gives rise to trophozoites. The inverse process is called encystation and begins when the trophozoites migrate to the lower part of the small intestine where they receive signals that trigger synthesis of the components of the cyst wall. The cyst form enables the parasite to survive in the environment, infect a new host and evade the immune response. In this work, we explored the role of protein S-palmitoylation, a unique reversible post-translational modification, during Giardia encystation, because de novo generation of endomembrane compartments, protein sorting and vesicle fusion occur in this process. Our findings may contribute to the design of therapeutic agents against this important human pathogen.

SUMOylation and deimination of proteins: two epigenetic modifications involved in Giardia encystation

SUMOylation, a posttranslational modification of proteins, has been recently described as vital in eukaryotic cells. In a previous work, we analyzed the role of SUMO protein and the genes encoding the putative enzymes of the SUMOylation pathway in the parasite Giardia lamblia. Although we observed several SUMOylated proteins, only the enzyme Arginine Deiminase (ADI) was confirmed as a SUMOylated substrate. ADI is involved in the survival of the parasite and, besides its role in ATP production, it also catalyzes the modification of arginine residues to citrulline in the cytoplasmic tail of surface proteins. During encystation, however, ADI translocates to the nuclei and downregulates the expression of the Cyst Wall Protein 2 (CWP2). In this work, we made site-specific mutation of the ADI SUMOylation site (Lys101) and observed that transgenic trophozoites did not translocate to the nuclei at the first steps of encystation but shuttled in the nuclei late during this process through classic nuclear localization signals. Inside the nuclei, ADI acts as a peptidyl arginine deiminase, being probably involved in the downregulation of CWPs expression and cyst wall formation. Our results strongly indicate that ADI plays a regulatory role during encystation in which posttranslational modifications of proteins are key players.

Vacuolar protein sorting receptor in Giardia lamblia

In Giardia, lysosome-like peripheral vacuoles (PVs) need to specifically coordinate their endosomal and lysosomal functions to be able to successfully perform endocytosis, protein degradation and protein delivery, but how cargo, ligands and molecular components generate specific routes to the PVs remains poorly understood. Recently, we found that delivering membrane Cathepsin C and the soluble acid phosphatase (AcPh) to the PVs is adaptin (AP1)-dependent. However, the receptor that links AcPh and AP1 was never described. We have studied protein-binding to AcPh by using H6-tagged AcPh, and found that a membrane protein interacted with AcPh. This protein, named GlVps (for Giardia lamblia Vacuolar protein sorting), mainly localized to the ER-nuclear envelope and in some PVs, probably functioning as the sorting receptor for AcPh. The tyrosine-binding motif found in the C-terminal cytoplasmic tail domain of GlVps was essential for its exit from the endoplasmic reticulum and transport to the vacuoles, with this motif being necessary for the interaction with the medium subunit of AP1. Thus, the mechanism by which soluble proteins, such as AcPh, reach the peripheral vacuoles in Giardia appears to be very similar to the mechanism of lysosomal protein-sorting in more evolved eukaryotic cells.

SUMOylation in Giardia lamblia: A Conserved Post-Translational Modification in One of the Earliest Divergent Eukaryotes

Post-translational modifications are able to regulate protein function and cellular processes in a rapid and reversible way. SUMOylation, the post-translational modification of proteins by the addition of SUMO, is a highly conserved process that seems to be present in modern cells. However, the mechanism of protein SUMOylation in earlier divergent eukaryotes, such as Giardia lamblia, is only starting to become apparent. In this work, we report the presence of a single SUMO gene encoding to SUMO protein in Giardia. Monoclonal antibodies against recombinant Giardia SUMO protein revealed the cytoplasmic localization of native SUMO in wild-type trophozoites. Moreover, the over-expression of SUMO protein showed a mainly cytoplasmic localization, though also neighboring the plasma membrane, flagella, and around and even inside the nuclei. Western blot assays revealed a number of SUMOylated proteins in a range between 20 and 120 kDa. The genes corresponding to putative enzymes involved in the SUMOylation pathway were also explored. Our results as a whole suggest that SUMOylation is a process conserved in the eukaryotic lineage, and that its study is significant for understanding the biology of this interesting parasite and the role of post-translational modification in its evolution.

Effectiveness of vagal nerve stimulation (VNS) in patients with drop-attacks and different epileptic syndromes

PURPOSE

The effectiveness of VNS was evaluated in thirty-nine encephalopatic patients with drug-resistant epilepsy characterized by multiple seizures and drop attacks. Twenty-five patients were affected by severe epilepsy with multiple independent spike foci (SE-MISF) and fourteen patients by Lennox-Gastaut syndrome (LGS).

METHOD

Changes in seizure frequency, cognition, adaptive behaviour and quality of life were assessed before and after VNS implant until three years. Outcome assessment for all seizure types included the number of seizures/month and the reduction in seizure frequency rate at each follow-up. Moreover, the effect of VNS on frequency, duration and intensity of drop attacks was separately addressed by a modification of McHugh scale.

RESULTS

VNS produced a mean seizure rate reduction of 41% at six months, 50% at twelve months, and 54% at thirty-six months. After one year of stimulation, thirteen patients with SE-MISF (52%) and three patients with LGS (21%) showed a reduction above 50% in all seizures' frequency rate. As for drop attacks, eight patients (20%) gained a reduction above 50%, while seven patients (17%) showed a reduction only in intensity and duration. Cognitive level and adaptive behaviour were unchanged, while a better quality of life was reported in half out of the patients.

CONCLUSIONS

VNS had a greater effect in reducing seizures frequency and drop attacks' intensity and duration in SE-MISF patients than LGS patients. An improved quality of life was observed also in those patients who only reduced the intensity and duration of drop attacks.

Cingulate epilepsy in a child with a low-grade glioma

INTRODUCTION

Anterior cingulate epilepsy is a peculiar epileptic syndrome with a broad range of clinical manifestations, depending on the numerous projections of anterior cingulate into motor systems. Its diagnosis is often delayed, as seizures mostly occur during sleep and are typically misdiagnosed as parasomnias. Moreover, most focal anterior cingulate epilepsies are believed to be cryptogenic or idiopathic, even if there are some reports of anterior cingulate cortical dysplasia, while anterior cingulate neoplasms underlying epilepsy are rare.

CASE REPORT

Here, we report a 30-month-old boy who developed, at the age of 20 months, cingulate epilepsy associated with a low-grade oligodendroglial tumor. It must outlined that the clinical presentation was characterized by very frequent and disabling seizures as the only symptom of the disease, while the results of several neuropsychological tests suggested intact intellectual and behavioral abilities.

DISCUSSION AND CONCLUSION

Seizures disappeared completely after surgical removal of the lesion and neuropsychological child's performances remained completely normal. Long-term follow-up and observation are essential for evaluating the future clinical course.

Efficacy and safety of levetiracetam in infants and young children with refractory epilepsy

The aim of this multicentric, retrospective, and uncontrolled study was to evaluate the efficacy and safety of levetiracetam (LEV) in 81 children younger than 4 years with refractory epilepsy. At an average follow-up period of 9 months, LEV administration was found to be effective in 30% of patients (responders showing more than a 50% decrease in seizure frequency) of whom 10 (12%) became seizure free. This efficacy was observed for focal (46%) as well as for generalized seizures (42%). In addition, in a group of 48 patients, we compared the initial efficacy (evaluated at an average of 3 months of follow-up) and the retention at a mean of 12 months of LEV, with regard to loss of efficacy (defined as the return to the baseline seizure frequency). Twenty-two patients (46%) were initial responders. After a minimum of 12 months of follow-up, 9 of 48 patients (19%) maintained the improvement, 4 (8%) of whom remained seizure free. A loss of efficacy was observed in 13 of the initial responders (59%). Maintained LEV efficacy was noted in patients with focal epilepsy and West syndrome. LEV was well tolerated. Adverse events were seen in 18 (34%) patients. The main side effects were drowsiness and nervousness. Adverse events were either tolerable or resolved in time with dosage reduction or discontinuation of the drug. We conclude that LEV is safe and effective for a wide range of epileptic seizures and epilepsy syndromes and, therefore, represents a valid therapeutic option in infants and young children affected by epilepsy.

Atypical Clinical Picture in a Patient with Benign Occipital Epilepsy: Diagnostic Contribution of Morpho-Functional MR. A Case Report

Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is a maternally inherited disease due to mitochondrial DNA (mtDNA) point mutations. The clinical phenotype varies in relation to the systems affected, age at onset and disease severity. The characteristic signs of MELAS are nausea and vomiting due to acidosis, headache, epilepsy, ataxia or generalized weakness, ophthalmoplegia, motor and sensory focal neurological deficits. The clinical course may improve due to partial regression of the typical lesions, but the prognosis is usually adverse. A 19-year-old man with a diagnosis of benign occipital epilepsy and resumption of seizure activity with focal occipital attacks since the age of 14 years came to our attention for the recent onset of drug-resistant electroclinical seizures of long duration with complex symptoms, where the dominant clinical feature was an intense, persistent bilateral periorbital migraine with nausea and vomiting, scintillation scotomata and blurring of vision. MR studies were performed at our institution in the immediate post-seizure phase and then at one week, three and six months. The acute-phase morphological scans showed a right cortical-subcortical area with altered signal in the occipitopolar region that was hypointense on T1 and hyperintense on T2 and FLAIR, with cortical thickening and effacement of the sulci. Contrast-enhanced scans did not demonstrate BBB alterations. The DWI scans showed a right temporo-occipital cortical area with higher signal intensity. In the subsequent examinations the area with altered signal shrank gradually and significantly in parallel with improvement in clinical conditions. The diagnostic hypothesis of benign occipital epilepsy was consistent neither with the clinical course, characterized by persistent headache, visual disturbance and refractoriness to antiepileptic drugs, nor with the temporal-occipital cortical MR findings, which resembled ischemic lesions but displayed a non-territorial pattern as well as reversibility over time. These elements guided in the diagnosis of MELAS, which was subsequently confirmed by identification of the typical gene mutation. On DWI the stroke-like lesions of MELAS are seen more frequently as focal hyperintense areas compared with healthy parenchyma. Such high signal intensity likely corresponds to T2 shine-through rather than cytotoxic edema. Indeed, several studies have demonstrated that in acute-phase scans of MELAS stroke-like lesions DWI hyperintensity is associated with increased ADC values that are not associated with restricted water diffusivity, reflecting the metabolic rather than anoxic-ischemic nature of these changes. In the present case, morphological MR associated with DWI was very helpful in guiding the diagnosis by demonstrating some pathognomonic features of MELAS stroke-like lesions such as cortical-subcortical involvement of the posterior hemispheres, the non-territorial pattern, lesion reversibility and the pathophysiological role of vasogenic edema in inducing an increase in extracellular water and thus in diffusion values.

Diagnosing Sjögren-Larsson syndrome in a 7-year-old Moroccan boy

Sjögren-Larsson syndrome (SLS) is an autosomal recessively inherited neurocutaneous disorder characterized by the triad of congenital ichthyosis, mental deficiency, and spastic diplegia or tetraplegia. Less common features are retinal changes, short stature, kyphoscoliosis, preterm birth, photophobia, reduction of visual acuity, seizures, and delayed speech. SLS is characterized by a genetic block in the oxidation of fatty alcohol to fatty acid because of deficient activity of fatty aldehyde dehydrogenase (FALDH), a component of the fatty alcohol: NAD oxidoreductase enzyme complex. As in other rare multisystem diseases, the diagnosis of SLS is often delayed. The definitive test for SLS is considered the measurement of FALDH or fatty alcohol: NAD oxidoreductase in cultured skin fibroblasts. Nevertheless, if specific FALDH activity test or DNA FALDH gene mutation tests are not available (as in our country), a reliable diagnosis of SLS is also possible when it is based on the matching of peculiar clinical, histologic and ultrastructural, laboratoristic, and imaging features. The simultaneous presence of cutaneous histologic features including hyperkeratosis, orthokeratosis, thickening of granular layer, abnormal lamellar inclusions in the cytoplasm of granular and horny cells (demonstrated by light and electron microscopy) in a child with ichthyosis, and typical neurologic abnormalities is highly suggestive of SLS. We describe the case of a young Moroccan boy presenting with ichthyosis, mental retardation, spastic diplegia, and peculiar skin histologic findings.

Complications of vagal nerve stimulation for epilepsy in children

Vagal nerve stimulation (VNS) is a surgical option to treat drug-resistant epilepsy. A few side effects have been described, mainly as anecdotal reports. We analysed our material concerning a juvenile population to identify the most common and most important complications, discussing them with the literature. Thirty-six patients were studied (18 months-18 years old). The children were assessed before the VNS implant and 3, 6, 12, 24 and 36 months after surgery. The mean follow-up was 30 months. Four patients required a second surgery: two for changing the device 3 years after implant; one for revision of an imperfect implant; one for removing a non-functioning device. In one patient a transient vocal cord paralysis was observed. Hoarseness was the main complaint (38.8%). More infrequent was mild sleep apnoea (8.3%), sternocleidomastoid muscle spasm, drooling and snoring in one patient each. Skin scars were reported with a different frequency according to the surgical technique. At variance with the literature reports, we did not observe infections. Side effects of VNS can be minimised, but not avoided completely, with a correct technical procedure, which in turn depends upon a thorough knowledge of vagus nerve anatomy.

Central pattern generators for a common semiology in fronto-limbic seizures and in parasomnias. A neuroethologic approach

Central pattern generators (CPGs) are genetically determined neuronal aggregates in the mesencephalon, pons and spinal cord subserving innate motor behaviours essential for survival (feeding, locomotion, reproduction etc.). In higher primates CPGs are largely under neocortical control. We describe how certain motor events observed in parasomnias and epileptic seizures could have similar features and resemble motor behaviours, which can be the expression of the same CPG. Both epilepsy and sleep can lead to a temporary loss of control of neomammalian cortex that facilitates through a common platform (arousal) the emergences of stereotyped inborn fixed action patterns. Therefore we suggest that, independently from the nature of the trigger, be it a seizure or a parasomnia, the same CPGs can be involved, "caught up", leading to a common motor semiology (the "Carillon theory").

Joubert syndrome with associated corpus callosum agenesis

In 1969, Joubert et al. studied a family where four of six children had a severe clinical condition with episodic alternate hyperpnoea and apnoea, hypotonia, ataxia, psychomotor delay, and abnormal ocular movements. Two of the four had agenesis of the posterior-inferior part of the cerebellar vermis and two had complete agenesis of the vermis. We report a 5-month-old girl with Joubert syndrome in whom MRI shows both features typical of this condition and associated corpus callosum agenesis. To our knowledge, complete callosal agenesis has been infrequently reported in children with Joubert syndrome; consequently, it might be regarded as a casual finding. Nevertheless, the hypothesis of a developmental abnormality of midline structures extended to the supratentorial compartment is rather attractive.

Autosomal recessive polymicrogyria with infantile spasms and limb deformities

We describe two siblings, a girl and a boy, aged 4 and 2 years and 10 months respectively, born from non-consanguineous parents,with diffuse polymicrogyria, lower limb deformities, infantile spasms and developmental delay. Spasms had a good outcome under antiepileptic drug treatment. Clinical and imaging features were of identical severity in both siblings. Muscle biopsy,creatine kinase, metabolic investigations and chromosomal analysis were normal. This combination of anatomo-clinical features and their occurrence in siblings of both sexes suggests an autosomal recessive malformation syndrome.

Multicentric glioma with unusual clinical presentation

Multiple glioma is a well-recognized but uncommon entity. They are grouped in two categories: multifocal and multicentric gliomas. Multifocal gliomas grow through dissemination along an established route, spreading through commissural pathways, CSF channels, or the blood or by local extension through satellite formation; at the opposite end of the spectrum, multicentric gliomas are widely separated lesions whose simultaneous presence cannot be attributed to any of the above pathways. Reports in the literature refer to single cases or small series of multicentric gliomas, almost always in adult patients, their occurrence in children being even less frequent. We report the case of a 12-year-old boy with multicentric glioma, atypical acute clinical onset and fast growth of three other tumors in 8 months, and then discuss the problems of diagnosis and therapy.

Chronic neuroborreliosis in infancy

Lyme disease is a polymorphic and multisystemic disease caused by Borrelia burgdorferi. Neurological manifestations are found in 10%-50% of cases. We present 2 cases followed for 5 and 6 years of chronic relapsing-remitting neuroborreliosis. Diagnosis of neuroborreliosis in these cases was based on serum and cerebrospinal fluid findings. We discuss clinical, neurophysiological, laboratory and instrumental aspects regarding the difficulties of reaching a correct diagnosis. Further studies, especially in the field of immunology, should help identify the mechanisms responsible for the disease becoming chronic. With this knowledge, it may be possible to design immunological therapies for relapses, and to prevent the evolution of the disease.

Open comparative long-term study of vigabatrin vs carbamazepine in newly diagnosed partial seizures in children

OBJECTIVE

To compare vigabatrin with carbamazepine as monotherapy in newly diagnosed children with partial epilepsy in order to evaluate the efficacy and tolerability of both drugs.

DESIGN

Open and randomized with a 2-year follow-up period.

SETTING

The Infantile Neuropsychiatric Division of the Regional Pediatric Hospital, Ancona, Italy.

PATIENTS

Seventy children with newly diagnosed partial epilepsy were treated with vigabatrin (38 patients) or carbamazepine (32 patients).

INTERVENTION

Vigabatrin, 50 to 60 mg/kg per day, or carbamazepine, 15 to 20 mg/kg per day, split into twice-a-day doses.

OUTCOME MEASURES

The efficacy and tolerability of vigabatrin were compared with those of the standard treatment (carbamazepine) for this patient group.

RESULTS

The efficacy of vigabatrin and carbamazepine was similar, with the suggestion of a better side effect profile with vigabatrin.

CONCLUSIONS

Vigabatrin monotherapy should be considered as a monotherapeutic treatment option in patients with newly diagnosed epilepsy. However, more studies are needed to evaluate other issues of concern, such as the cognitive and behavioral adverse effects of antiepileptic drugs, to determine the most suitable therapy.

Endocranial calcifications, infantile celiac disease, and epilepsy

The authors report on five patients (three female, two male) with multiple brain calcifications, infantile celiac disease, and epilepsy. The clinical, neuroradiological, neurophysiological, EEG and evolutional aspects are assessed. The authors propose that all patients with brain calcifications which cannot be traced to other known pathologies should undergo diagnostic tests for a malabsorption syndrome; analogously, patients affected with infantile celiac disease should undergo EEG, followed by a neuroradiological examination if the EEG pattern is found to be altered.

Spielmeyer-Vogt disease: clinical and neurophysiological aspects

Recent neurophysiological studies have identified a characteristic profile in the case of certain progressive infantile encephalopathies which, together with clinical data, may assist with the diagnosis. The authors report a case of juvenile ceroid lipofuscinosis (Spielmeyer-Vogt disease) and stress the importance of carrying out neurophysiological investigations for diagnostic purposes and for controlling the progression of the disease. The effect of antioxidant therapy (sodium selenite and vitamin E) on these investigations and on the natural evolution of the disease is also discussed.

Hearing assessment in developmentally impaired infants: classical conditioning as a supplement to brainstem-evoked response audiometry (BERA)

The brainstem-evoked response audiometry (BERA) is probably the most common approach to hearing assessment in high-risk and developmentally handicapped infants. It is usually suggested, however, that BERA should not be the sole assessment method. In an attempt to determine an effective supplement to BERA, the present study evaluated a classical conditioning procedure with developmentally impaired babies. Within this procedure, different tones served as conditioned stimuli while an air-puff was used as the unconditioned stimulus. Results indicate that this procedure could be successfully applied with almost all of the babies.