Management of side effects of mTOR inhibitors in tuberous sclerosis patients

Everolimus and sirolimus in the treatment of cardiac rhabdomyomas in neonates

BACKGROUND AND OBJECTIVES

Cardiac rhabdomyoma (CR) is the principal cardiac tumor diagnosed in pediatric age and is commonly associated with tuberous sclerosis complex. In some patients, these masses can cause heart failure and difficult-to-control arrhythmias. There are multiple case reports on use of mammalian target of rapamycin (mTOR) inhibitors, everolimus or sirolimus, in treatment of CRs. We reviewed the current data regarding effectiveness of everolimus and sirolimus in treating of CRs in newborns with hemodynamic repercussions.

METHODS

This systematic review was reported according to the PRISMA guidelines. The EBSCO, PubMed, EMBASE, and Lilacs databases were searched for full-text articles reporting the use of everolimus or sirolimus in the treatment of CRs in neonates and infants.

RESULTS

Thirty-one articles met inclusion criteria, totaling 48 patients. Hemodynamic instability prompted treatment in 89.5% of cases. Everolimus was used in 83.3% of cases and sirolimus in 16.6%. The median treatment duration was 67 days, with a 57 ± 23% average CR size reduction. Common adverse events included hypertriglyceridemia, infections, and hematological abnormalities.

CONCLUSIONS

mTOR inhibitors appear effective and safe for treating CRs in neonates and infants. The average daily doses were 1.03 mg/m²/day for everolimus and 1.37 mg/m²/day for sirolimus. Randomized controlled clinical trials are necessary to confirm these findings and establish optimal treatment protocols.

IMPACT

Currently, there are no results from randomized clinical trials evaluating the efficacy of mammalian target of rapamycin inhibitors in patients with symptomatic cardiac rhabdomyomas. This is the first systematic review that evaluates the efficacy and safety of the use of everolimus and sirolimus in the non-surgical treatment of cardiac rhabdomyomas with hemodynamic repercussions in neonates. Everolimus and sirolimus may be particularly useful in the neonatal period when the hemodynamic complications caused by cardiac rhabdomyomas are more severe.

Subependymal Giant Cell Astrocytoma: The Molecular Landscape and Treatment Advances

Subependymal giant cell astrocytoma (SEGA) is most often found in patients with TSC (Tuberous Sclerosis Complex). Although it has been classified as a benign tumor, it may create a serious medical problem leading to grave consequences, including young patient demise. Surgery and chemotherapy belong to the gold standard of treatment. A broader pharmacological approach involves the ever-growing number of rapalogs and ATP-competitive inhibitors, as well as compounds targeting other kinases, such as dual PI3K/mTOR inhibitors and CK2 kinase inhibitors. Novel approaches may utilize noncoding RNA-based therapeutics and are extensively investigated to this end. The purpose of our review was to characterize SEGA and discuss the latest trends in the diagnosis and therapy of this disease.

Cardiac Rhabdomyomas Presenting with Critical Cardiac Obstruction in Neonates and Infants: Treatment Strategies and Outcome, A Single-Center Experience

Cardiac rhabdomyomas are the most common benign pediatric heart tumor in infancy, which are commonly associated with tuberous sclerosis complex (TSC). Most rhabdomyomas are asymptomatic and spontaneously regress over time. However, some cases especially in neonates or small infants can present with hemodynamic instability. Surgical resection of the tumor, which has been the gold standard in alleviating obstruction, is not always possible and may be associated with significant morbidity and mortality. Recently, mammalian target of rapamycin inhibitors (mTORi) have been shown to be safe and effective in the treatment of TSC. We present the outcomes of neonates and an infant who received treatment for symptomatic rhabdomyomas at a tertiary cardiology center. Medical records were reviewed to obtain clinical, demographic, and outcome data. Six patients received interventions for symptomatic rhabdomyomas, median age at presentation was 1 day old (range from 1 to 121 days old), and 67% of the patients had a pathogenic mutation in TSC gene. One patient underwent surgical resection of solitary tumor at right ventricular outflow tract (RVOT) successfully. In the four patients with left ventricular outflow tract (LVOT) obstruction, two patients received combined therapy of surgical debulking of LVOT tumor, Stage I palliation procedure, and mTORi and two patients received mTORi therapy. One patient with RVOT obstruction underwent ductal stenting and received synergistic mTORi. Four of the five patients had good response to mTORi demonstrated by the rapid regression of rhabdomyoma size. 83% of patients are still alive at their latest follow-up, at two to eight years of age. One patient died on day 17 post-LVOT tumor resection and Hybrid stage one due to failure of hemostasis, in the background of familial factor VII deficiency. Treatment of symptomatic rhabdomyoma requires individualized treatment strategy based on the underlying pathophysiology, with involvement of multidisciplinary teams. mTORi is effective and safe in inducing rapid regression of rhabdomyomas. A standardized mTORi prescription and monitoring guide will ensure medication safety in neonates and infants with symptomatic cardiac rhabdomyoma. Although the majority of tumors responded to mTORi, some prove to be resistant. Further studies are warranted, ideally involving multiple international centers with a larger number of patients.

Effectiveness and safety of everolimus treatment in patients with tuberous sclerosis complex in real-world clinical practice

BACKGROUND

The randomised double-blinded placebo-controlled EXIST-1-3 studies have showed everolimus effective with adverse effects reported as acceptable in treatment of symptoms in patients with tuberous sclerosis complex (TSC), although evidence of outcomes in clinical practice remains limited. This study aimed to investigate, in clinical practice, the effectiveness and safety of everolimus for epilepsy, renal angiomyolipoma (rAML), and subependymal giant cell astrocytoma (SEGA) in patients with TSC.

RESULTS

The study included 64 patients with TSC (median age: 19, range 0.9-54 years) receiving everolimus treatment (Norway: n = 35; Denmark: n = 29). Among 45 patients with epilepsy, 14 (31%) were responders experiencing ≥ 50% reduction in seizure frequency in the last 3 months of treatment compared with the last 3 months before treatment. Nineteen (42%) patients changed their anti-seizure medications (ASMs). Responders were more common among patients < 18 years (46%) than among patients ≥ 18 years (14%, p = 0.03). In 29 patients with rAML, everolimus reduced (≥ 30% decrease) and stabilized (< 20% increase, ≤ 30% decrease) longest diameter of rAML in 38% and 59%, respectively, after a mean treatment duration of 37 months. SEGA volume was reduced in three patients by 71%, 43%, and 48% after 39, 34, and 82 months. Adverse effects were reported in 61 of 64 patients (95%) after a median treatment duration of 31 months (range 0-106), with oral ulceration/stomatitis (63%) and upper respiratory tract infections (38%) being the most common. The most common laboratory abnormalities were increased cholesterol (41%), anaemia (30%), and leucopoenia (25%). Grade 3-4 adverse effects were reported in 36% of cases, and life-threatening conditions were reported in two patients. Nine patients discontinued everolimus treatment.

CONCLUSIONS

Seizure reduction in this study sample was consistent with results from EXIST, but might be lower than expected, given that changes in concomitant ASMs are part of clinical practice. Seizure reduction was associated with younger age. As with EXIST, everolimus reduced or stabilised rAML size in most patients. SEGA volume was reduced in all three patients. Close follow-up is needed for this group, especially for children and patients who may not be able to report adverse effects.

Subependymal Giant Cell Astrocytomas in Tuberous Sclerosis Complex-Current Views on Their Pathogenesis and Management

Introduction, Tuberous sclerosis complex (TSC) is an autosomal-dominant disorder caused by mutations inactivating TSC1 or TSC2 genes and characterized by the presence of tumors involving many organs, including the brain, heart, kidneys, and skin. Subependymal giant cell astrocytoma (SEGA) is a slow-growing brain tumor almost exclusively associated with TSC.

STATE OF THE ART

Despite the fact that SEGAs are benign, they require well-considered decisions regarding the timing and modality of pharmacological or surgical treatment. In TSC children and adolescents, SEGA is the major cause of mortality and morbidity.

CLINICAL IMPLICATIONS

Until recently, surgical resection has been the standard therapy for SEGAs but the discovery of the role of the mTOR pathway and the introduction of mTOR inhibitors to clinical practice changed the therapeutic landscape of these tumors. In the current paper, we discuss the pros and cons of mTOR inhibitors and surgical approaches in SEGA treatment.

FUTURE DIRECTIONS

In 2021, the International Tuberous Sclerosis Complex Consensus Group proposed a new integrative strategy for SEGA management. In the following review, we discuss the proposed recommendations and report the results of the literature search for the latest treatment directions.

Monitoring and Managing Patients with Tuberous Sclerosis Complex: Current State of Knowledge

Tuberous sclerosis complex (TSC) is a rare genetic disease of autosomal dominant transmission that, in most cases, results from the presence of pathogenic variants of the TSC1 or TSC2 genes, encoding hamartin and tuberin, respectively. It is a multisystemic disease, affecting most frequently the brain, skin, kidney, and heart. The wide variety of possible clinical manifestations, given this multisystem dimension, makes the follow-up of patients with TSC an exercise of multidisciplinarity. In fact, these patients may require the intervention of various medical specialties, which thus have to combine their efforts to practice a medicine that is truly holistic. The past few years have witnessed a dramatic leap not only in the diagnosis and management of TSC patients, with standard monitoring recommendations, but also in the therapeutic field, with the use of mTORC1 inhibitors. In this article, we review the clinical manifestations associated with TSC, as well as the treatment and follow-up strategies that should be implemented, from a multidisciplinary perspective.

The long-term effect of mTOR inhibition on lipid and glucose metabolism in tuberous sclerosis complex: data from the Dutch TSC registry

Background

MTOR inhibition is an effective treatment for many manifestations of tuberous sclerosis complex. Because mTOR inhibition is a disease modifying therapy, lifelong use will most likely be necessary. This study addresses the long-term effects of mTOR inhibitors on lipid and glucose metabolism and aims to provide better insight in the incidence and time course of these metabolic adverse effects in treated TSC patients.

Methods

All patients who gave informed consent for the nationwide TSC Registry and were ever treated with mTOR inhibitors (sirolimus and/or everolimus) were included. Lipid profiles, HbA1c and medication were analysed in all patients before and during mTOR inhibitor treatment.

Results

We included 141 patients, the median age was 36 years, median use of mTOR inhibitors 5.1 years (aimed serum levels 3.0–5.0 µg/l). Total cholesterol, LDL- and HDL-cholesterol levels at baseline were similar to healthy reference data. After start of mTOR inhibition therapy, total cholesterol, LDL-cholesterol and triglycerides increased significantly and were higher compared to healthy reference population. Mean total cholesterol levels increased by 1.0 mmol/L after 3–6 months of mTOR inhibition therapy but did not increase further during follow-up. In this study, 2.5% (3/118) of patients developed diabetes (defined as an HbA1c ≥ 48 mmol/mol) during a median follow-up of 5 years.

Conclusions

Hypercholesterolemia is a frequent side effect of mTOR inhibition in TSC patients, and predominantly occurs within the first year of treatment. Although hyperglycemia is a frequent side effect in other indications for mTOR inhibition, incidence of diabetes mellitus in TSC patients was only 2.5%. This may reflect the difference of mTOR inhibition in patients with normal mTOR complex pathway function versus patients with overactive mTOR complex signaling due to a genetic defect (TSC patients).

Antiepileptic Effect and Safety Profile of Rapamycin in Pediatric Patients With Tuberous Sclerosis Complex

Background

Epilepsy develops in 70–90% of children with Tuberous Sclerosis Complex (TSC) and is often resistant to medication. Treatment with mTOR pathway inhibitors is an important therapeutic option in drug-resistant epilepsy associated with TSC. Our study evaluated the antiepileptic effect of rapamycin in the pediatric population of patients diagnosed with TSC.

Methods

This single center, open-label study evaluated safety and anti-epileptic efficacy of 12 months of rapamycin treatment in 32 patients aged from 11 months to 14 years with drug-resistant TSC- associated epilepsy.

Results

After the first 6 months of treatment, the improvement in seizure frequency, defined as at least a 50% reduction in the number of seizures per week compared to baseline, was seen in 18 individuals (56.25%). We observed no change in 12 individuals (37.5%) and worsening, defined as increase in the number of seizures—in 2 patients (6.25%). The overall improvement defined as at least a 50% reduction in seizure frequency was found in 65.6% of all patients after 12 months with 28% of patients obtaining complete remission. Another five patients experienced at least an 80% reduction in the frequency of seizures. Concomitant treatment with vigabatrin, and to a much lesser extent topiramate and levetiracetam, was an additional favorable prognostic factor for the success of the therapy. A linear relationship between the cumulative dose of rapamycin and its therapeutic effect was observed. The safety profile of the drug was satisfactory. In none of the observed cases did the adverse events reach the level that required withdrawal of the rapamycin treatment. The reason for dropouts was insufficient drug efficacy in 3 cases.

Conclusions

Long-term use of rapamycin, especially in combination with vigabatrin, might be a beneficial therapeutic option in the treatment of drug-resistant epilepsy in children with TSC.

Perfect match: mTOR inhibitors and tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant syndrome that presents with diverse and complex clinical features and involves multiple human systems. TSC-related neurological abnormalities and organ dysfunction greatly affect the quality of life and can even result in death in patients with TSC. It is widely accepted that most TSC-related clinical manifestations are associated with hyperactivation of the mammalian target of rapamycin (mTOR) pathway caused by loss‑of‑function mutations in TSC1 or TSC2. Remarkable progress in basic and translational research has led to encouraging clinical advances. Although mTOR inhibitors (rapamycin/everolimus) demonstrate great potential in TSC management, two major concerns hamper their generalized application. One is the frequent manifestation of adverse events, such as stomatitis, infections, and menstrual disorders; and the other is the poor response in certain patients. Thus, indicators are required to effectively predict the efficacy of mTOR inhibitors. Herein, we have summarized the current utilization of mTOR inhibitors in the treatment of TSC and focused on their efficacy and safety, in an attempt to provide a reference to guide the treatment of TSC.

Hyperactivation of mammalian target of rapamycin (mTOR) is essential in the pathogenesis of tuberous sclerosis complex (TSC) and can serve as a therapeutic target.

mTOR inhibitors have shown considerable success in multiple clinical trials for the treatment of TSC, including neurological, pulmonary, cardiac, renal, and cutaneous phenotypes.

mTOR inhibitors are associated with adverse events, which should be considered during the management of TSC.

Indicators to predict mTOR inhibitor efficacy are required to select patients who are likely to benefit from such therapy.

Benign tumors in TSC are amenable to treatment by GD3 CAR T cells in mice

Mutations underlying disease in tuberous sclerosis complex (TSC) give rise to tumors with biallelic mutations in TSC1 or TSC2 and hyperactive mammalian target of rapamycin complex 1 (mTORC1). Benign tumors might exhibit de novo expression of immunogens, targetable by immunotherapy. As tumors may rely on ganglioside D3 (GD3) expression for mTORC1 activation and growth, we compared GD3 expression in tissues from patients with TSC and controls. GD3 was overexpressed in affected tissues from patients with TSC and also in aging Tsc2+/- mice. As GD3 overexpression was not accompanied by marked natural immune responses to the target molecule, we performed preclinical studies with GD3 chimeric antigen receptor (CAR) T cells. Polyfunctional CAR T cells were cytotoxic toward GD3-overexpressing targets. In mice challenged with Tsc2-/- tumor cells, CAR T cells substantially and durably reduced the tumor burden, correlating with increased T cell infiltration. We also treated aged Tsc2+/- heterozygous (>60 weeks) mice that carry spontaneous Tsc2-/- tumors with GD3 CAR or untransduced T cells and evaluated them at endpoint. Following CAR T cell treatment, the majority of mice were tumor free while all control animals carried tumors. The outcomes demonstrate a strong treatment effect and suggest that targeting GD3 can be successful in TSC.

Trends of rapamycin in survival benefits of liver transplantation for hepatocellular carcinoma

The proportion of liver transplantation (LT) for hepatocellular carcinoma (HCC) has kept on increasing over the past years and account for 20%-40% of all LT. Post-transplant HCC recurrence is considered the most important factor affecting the long-term survival of patients. The use of different types of immunosuppressive agents after LT is closely associated with an increased risk for HCC recurrence. The most commonly used conventional immunosuppressive drugs include the calcineurin inhibitors tacrolimus (FK506) and mammalian target of rapamycin inhibitor rapamycin (RAPA). Compared with tacrolimus, RAPA may carry an advantage in survival benefit because of its anti-tumor effects. However, no sufficient evidence to date has proven that RAPA could increase long-term recurrence-free survival and its anti-tumor mechanism of combined therapy remains incompletely clear. In this review, we will focus on recent advances in clinical application experience and basic research results of RAPA in patients undergoing LT for HCC to further guide the clinical practice.

Structural Aspects of mTOR Inhibitors: In Progress to Search Potential Compounds

mTOR (mammalian target of rapamycin) is a catalytic subunit composed of two multi-protein complexes that indicate mTORC1, mTORC2. It plays a crucial role in various fundamental cell processes like cell proliferation, metabolism, survival, cell growth, etc. Various first line mTOR inhibitors such as Rapamycin, Temsirolimus, Everolimus, Ridaforolimus, Umirolimus, Zotarolimus have been used popularly. Whereas, several mTOR inhibitors such as Gedatolisib (PF-05212384) are under phase 2 clinical trials studies for the treatment of triple-negative breast cancer. The mTOR inhibitors bearing heterocyclic moieties such as quinazoline, thiophene, morpholine, imidazole, pyrazine, furan, quinoline are under investigation against various cancer cell lines (U87MG, PC-3, MCF-7, A549, MDA-231). In this review, we summarized updated research related to mTOR inhibitors, their structure-activity relationship which may help scientists for the development of potent inhibitors against cancer.

Mammalian/mechanistic target of rapamycin (mTOR) complexes in neurodegeneration

Novel targets to arrest neurodegeneration in several dementing conditions involving misfolded protein accumulations may be found in the diverse signaling pathways of the Mammalian/mechanistic target of rapamycin (mTOR). As a nutrient sensor, mTOR has important homeostatic functions to regulate energy metabolism and support neuronal growth and plasticity. However, in Alzheimer's disease (AD), mTOR alternately plays important pathogenic roles by inhibiting both insulin signaling and autophagic removal of β-amyloid (Aβ) and phospho-tau (ptau) aggregates. It also plays a role in the cerebrovascular dysfunction of AD. mTOR is a serine/threonine kinase residing at the core in either of two multiprotein complexes termed mTORC1 and mTORC2. Recent data suggest that their balanced actions also have implications for Parkinson's disease (PD) and Huntington's disease (HD), Frontotemporal dementia (FTD) and Amyotrophic Lateral Sclerosis (ALS). Beyond rapamycin; an mTOR inhibitor, there are rapalogs having greater tolerability and micro delivery modes, that hold promise in arresting these age dependent conditions.

Treatment of Cardiac Rhabdomyomas with mTOR Inhibitors in Children with Tuberous Sclerosis Complex-A Systematic Review

BACKGROUND

Cardiac rhabdomyomas (CRs) are the earliest sign of tuberous sclerosis complex (TSC). Most of them spontaneously regress after birth. However, multiple and/or large tumors may result in heart failure or cardiac arrhythmia. Recently, the attempts to treat CRs with mTOR inhibitors (mTORi) have been undertaken. We reviewed the current data regarding the effectiveness and safety of mTORi in the treatment of CRs in children with TSC.

METHODS

The review was conducted according to the PRISMA guidelines. Medline, Embase, Cochrane library, and ClinicalTrial.gov databases were searched for original, full-text articles reporting the use of mTORi (everolimus or sirolimus) in the treatment of CRs in children with TSC.

RESULTS

Thirty articles describing 41 patients were identified (mostly case reports, no randomized or large cohort studies). Thirty-three children (80.5%) had symptomatic CRs and mTORi therapy resulted in clinical improvement in 30 of them (90.9%). CRs size reduction was reported in 95.1%. Some CRs regrew after mTORi withdrawal but usually without clinical symptoms recurrence. The observed side effects were mostly mild.

CONCLUSIONS

mTORi may be considered as a temporary and safe treatment for symptomatic CRs in children with TSC, especially in high-risk or inoperable tumors. However, high-quality, randomized trials are still lacking.

Maintenance Therapy With Everolimus for Subependymal Giant Cell Astrocytoma in Patients With Tuberous Sclerosis - Final Results From the EMINENTS Study

The aim of this EMINENTS prospective, single-center, open-label, single-arm study was to evaluate the cumulative efficacy and safety of reduced doses of everolimus (maintenance therapy) in patients with tuberous sclerosis and subependymal giant cell astrocytoma (SEGA). Methods: The trial included 15 patients who had undergone at least 12 months of treatment with a standard everolimus dose. The dose of everolimus was reduced to three times a week, with a daily dose as in standard regimen. Data of 14 patients were analyzed. SEGA volume (SV) was evaluated at study entry and subsequent time points by an experienced radiologist. Adverse events (AEs) noted during maintenance therapy were compared to the AEs of standard dose period. Results: Patients were followed over a mean duration 58.37 months (95%CI: 45.95-70.78). The differences in SEGA volume between subsequent time points (0, 3, 6,12, 18, 24, 36, 48, and 60 months) were not statistically significant (p = 0.16). At the end of the study, 7 out of 10 patients had stable SEGA volume. No clinical symptoms of progression were observed in any patients. No patient or tumor-related risk factors of progression were identified. Regarding AEs, infections (stomatitis, bronchitis, diarrhea) and laboratory abnormalities (neutropenia, anemia, hyperglycemia) occurred less frequently during maintenance therapy compared to the standard dose regimen. Conclusions: Final results from EMINENTS study confirm that maintenance therapy with everolimus might represent a rational therapeutic option for patients TSC and SEGA after effective full dose treatment. It could be an option for patients who experienced everolimus-related AEs, instead of discontinuation of therapy. Careful evaluation of possible progression, especially concerning first six months of maintenance therapy should be advised. Clinical Trial Registration: www.drks.de, identifier DRKS00005584.

TuberOus SClerosis registry to increAse disease awareness (TOSCA) Post-Authorisation Safety Study of Everolimus in Patients With Tuberous Sclerosis Complex

This non-interventional post-authorisation safety study (PASS) assessed the long-term safety of everolimus in patients with tuberous sclerosis complex (TSC) who participated in the TuberOus SClerosis registry to increase disease Awareness (TOSCA) clinical study and received everolimus for the licensed indications in the European Union. The rate of adverse events (AEs), AEs that led to dose adjustments or treatment discontinuation, AEs of potential clinical interest, treatment-related AEs (TRAEs), serious AEs (SAEs), and deaths were documented. One hundred seventy-nine patients were included in the first 5 years of observation; 118 of 179 patients had an AE of any grade, with the most common AEs being stomatitis (7.8%) and headache (7.3%). AEs caused dose adjustments in 56 patients (31.3%) and treatment discontinuation in nine patients (5%). AEs appeared to be more frequent and severe in children. On Tanner staging, all patients displayed signs of age-appropriate sexual maturation. Twenty-two of 106 female (20.8%) patients had menstrual cycle disorders. The most frequent TRAEs were stomatitis (6.7%) and aphthous mouth ulcer (5.6%). SAEs were reported in 54 patients (30.2%); the most frequent SAE was pneumonia (>3% patients; grade 2, 1.1%, and grade 3, 2.8%). Three deaths were reported, all in patients who had discontinued everolimus for more than 28 days, and none were thought to be related to everolimus according to the treating physicians. The PASS sub-study reflects the safety and tolerability of everolimus in the management of TSC in real-world routine clinical practice.

The coding and non-coding transcriptional landscape of subependymal giant cell astrocytomas

Tuberous sclerosis complex (TSC) is an autosomal dominantly inherited neurocutaneous disorder caused by inactivating mutations in TSC1 or TSC2, key regulators of the mechanistic target of rapamycin complex 1 (mTORC1) pathway. In the CNS, TSC is characterized by cortical tubers, subependymal nodules and subependymal giant cell astrocytomas (SEGAs). SEGAs may lead to impaired circulation of CSF resulting in hydrocephalus and raised intracranial pressure in patients with TSC. Currently, surgical resection and mTORC1 inhibitors are the recommended treatment options for patients with SEGA. In the present study, high-throughput RNA-sequencing (SEGAs n = 19, periventricular control n = 8) was used in combination with computational approaches to unravel the complexity of SEGA development. We identified 9400 mRNAs and 94 microRNAs differentially expressed in SEGAs compared to control tissue. The SEGA transcriptome profile was enriched for the mitogen-activated protein kinase (MAPK) pathway, a major regulator of cell proliferation and survival. Analysis at the protein level confirmed that extracellular signal-regulated kinase (ERK) is activated in SEGAs. Subsequently, the inhibition of ERK independently of mTORC1 blockade decreased efficiently the proliferation of primary patient-derived SEGA cultures. Furthermore, we found that LAMTOR1, LAMTOR2, LAMTOR3, LAMTOR4 and LAMTOR5 were overexpressed at both gene and protein levels in SEGA compared to control tissue. Taken together LAMTOR1-5 can form a complex, known as the 'Ragulator' complex, which is known to activate both mTORC1 and MAPK/ERK pathways. Overall, this study shows that the MAPK/ERK pathway could be used as a target for treatment independent of, or in combination with mTORC1 inhibitors for TSC patients. Moreover, our study provides initial evidence of a possible link between the constitutive activated mTORC1 pathway and a secondary driver pathway of tumour growth.

Modifying genetic epilepsies - Results from studies on tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant neurocutaneous disorder affecting approximately 1 in 6,000 in general population and represents one of the most common genetic causes of epilepsy. Epilepsy affects 90% of the patients and appears in the first 2 years of life in the majority of them. Early onset of epilepsy in the first year of life is associated with high risk of cognitive decline and neuropsychiatric problems including autism. Recently TSC has been recognized as a model of genetic epilepsies. TSC is a genetic condition with known dysregulated mTOR pathway and is increasingly viewed as a model for human epileptogenesis. Moreover, TSC is characterized by a hyperactivation of mTOR (mammalian target of rapamycin) pathway, and mTOR activation was showed to be implicated in epileptogenesis in many animal models and human epilepsies. Recently published studies documented positive effect of preventive or disease modifying treatment of epilepsy in infants with high risk of epilepsy with significantly lower incidence of epilepsy and better cognitive outcome. Further studies on preventive treatment of epilepsy in other genetic epilepsies of early childhood are considered. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Renal toxicity with mammalian target of rapamycin inhibitors: A meta-analysis of randomized clinical trials

A meta-analysis of randomized clinical trials (RCT) was done to determine the relative risk (RR) of acute kidney injury (AKI) with the use of mammalian target of rapamycin (mTOR) inhibitors. Citations from PubMed/Medline, clinical trials.gov, package inserts and abstracts from major conferences were reviewed to include RCTs comparing arms with or without mTOR inhibitors. The RR of all grade AKI in patients taking mTOR inhibitors compared to patients not on mTOR inhibitors was 1.55 (95% CI: 1.11 to 2.16, P=0.010). There was no significant difference in the risk of high-grade AKI for the two groups (RR=1.29, P=0.118, 95% CI: 0.94 to 1.77). There was no significant difference in the incidence rates for either all grade or high-grade AKI between the two groups. There was no publication bias and the trials were of high quality per Jadad scoring.

Preventive treatment with oral sirolimus and aspirin in a newborn with severe Sturge-Weber syndrome

Sturge-Weber syndrome (SWS) is characterized by facial capillary malformation, leptomeningeal capillary malformations, and choroidal and episcleral vascular malformations. These malformations produce neurologic and ophthalmological symptoms including seizures and glaucoma. A premature male newborn without prenatal diagnosis presented with severe bilateral SWS and was started on systemic sirolimus and aspirin. The patient has remained seizure-free for 23 months and demonstrated an excellent response to pulsed dye laser treatment.

mTOR Signaling Pathway in Cancer Targets Photodynamic Therapy In Vitro

The Mechanistic or Mammalian Target of Rapamycin (mTOR) is a major signaling pathway in eukaryotic cells belonging to the P13K-related kinase family of the serine/threonine protein kinase. It has been established that mTOR plays a central role in cellular processes and implicated in various cancers, diabetes, and in the aging process with very poor prognosis. Inhibition of the mTOR pathway in the cells may improve the therapeutic index in cancer treatment. Photodynamic therapy (PDT) has been established to selectively eradicate neoplasia at clearly delineated malignant lesions. This review highlights recent advances in understanding the role or regulation of mTOR in cancer therapy. It also discusses how mTOR currently contributes to cancer as well as future perspectives on targeting mTOR therapeutically in cancer in vitro.

Tuberous sclerosis complex: new insights into clinical and therapeutic approach

Tuberous sclerosis complex (TSC) is a complex disease with many different clinical manifestations. Despite the common opinion that TSC is a rare condition, with a mean incidence of 1/6000 live births and a prevalence of 1/20,000, it is increasingly evident that in reality this is not true. Its clinical sequelae span a range of multiple organ systems, in particular the central nervous system, kidneys, skin and lungs. The management of TSC patients is heavily burdensome in terms of time and healthcare costs both for the families and for the healthcare system. Management options include conservative approaches, surgery, pharmacotherapy with mammalian target of rapamycin inhibitors and recently proposed options such as therapy with anti-EGFR antibody and ultrasound-guided percutaneous microwaves. So far, however, no systematically accepted strategy has been found that is both clinically and economically efficient. Thus, decisions are tailored to patients' characteristics, resource availability and clinical and technical expertise of each single center. This paper reviews the pathophysiology and the clinical (diagnostic-therapeutic) management of TSC.

The use of rapamycin in patients with tuberous sclerosis complex: Long-term results

PURPOSE

The purpose of this study was to evaluate the long-term results of eight cases diagnosed with tuberous sclerosis complex (TSC) and receiving rapamycin therapy because of epileptic seizures and/or accompanying TSC findings.

METHOD

Rapamycin therapy was initiated at a dose of 1.5 mg/m². Seizure frequency, electroencephalographic (EEG) findings, renal and cranial imaging findings, and cutaneous lesions over 3- to 6-month periods during follow-up and treatment were evaluated.

RESULTS

Four girls and four boys aged 4-16 years at the start of rapamycin therapy and now aged 9-24 years were evaluated. Duration of rapamycin therapy was 1-5 years, and the monitoring period after commencement of rapamycin therapy lasted 5-8 years. Positive effects were observed at 9-12 months in three out of six cases of renal angiomyolipoma (AML) and in the second year of treatment in one. An increase in AML dimensions was observed in three cases after treatment was stopped. Seizure control was established in the first year of rapamycin therapy in all cases. An increased frequency of seizures was observed in three cases after the second year of treatment. No seizure recurrence was determined in the second year of treatment with rapamycin in five out of eight cases. Recurrence of seizure was observed in 6-12 months after the discontinuation of rapamycin in three cases.

CONCLUSION

Rapamycin therapy exhibits positive effects on epileptic seizures in cases of TSC in 1-2 years but these positive effects on seizure control of rapamycin therapy decline after the second year. Larger case series are still needed to determine the duration and effectiveness of treatment in childhood.

New Mammalian Target of Rapamycin (mTOR) Modulators Derived from Natural Product Databases and Marine Extracts by Using Molecular Docking Techniques

Mammalian target of rapamycin (mTOR) is a PI3K-related serine/threonine protein kinase that functions as a master regulator of cellular growth and metabolism, in response to nutrient and hormonal stimuli. mTOR functions in two distinct complexes—mTORC1 is sensitive to rapamycin, while, mTORC2 is insensitive to this drug. Deregulation of mTOR’s enzymatic activity has roles in cancer, obesity, and aging. Rapamycin and its chemical derivatives are the only drugs that inhibit the hyperactivity of mTOR, but numerous side effects have been described due to its therapeutic use. The purpose of this study was to identify new compounds of natural origin that can lead to drugs with fewer side effects. We have used computational techniques (molecular docking and calculated ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) parameters) that have enabled the selection of candidate compounds, derived from marine natural products, SuperNatural II, and ZINC natural products, for inhibitors targeting, both, the ATP and the rapamycin binding sites of mTOR. We have shown experimental evidence of the inhibitory activity of eleven selected compounds against mTOR. We have also discovered the inhibitory activity of a new marine extract against this enzyme. The results have been discussed concerning the necessity to identify new molecules for therapeutic use, especially against aging, and with fewer side effects.

Bioreducible Poly(Amino Ethers) Based mTOR siRNA Delivery for Lung Cancer

PURPOSE

Lung cancer is one of the leading causes of deaths in the United States, but currently available therapies for lung cancer are associated with reduced efficacy and adverse side effects. Small interfering RNA (siRNA) can knock down the expression of specific genes and result in therapeutic efficacy in lung cancer. Recently, mTOR siRNA has been shown to induce apoptosis in NSCLC cell lines but its use is limited due to poor stability in biological conditions.

METHODS

In this study, we modified an aminoglyocisde-derived cationic poly (amino-ether) by introducing a thiol group using Traut's reagent to generate a bio-reducible modified-poly (amino-ether) (mPAE). The mPAE polymer was used to encapsulate mTOR siRNA by nanoprecipitation method, resulting in the formation of stable and bio-reducible nanoparticles (NPs) which possessed an average diameter of 114 nm and a surface charge of approximately +27 mV.

RESULTS

The mTOR siRNA showed increased release from the mTS-mPAE NPs in the presence of 10 mM glutathione (GSH). The polymeric mTS-mPAE-NPs were also capable of efficient gene knockdown (60 and 64%) in A549 and H460 lung cancer cells, respectively without significant cytotoxicity at 30 μg/ml concentrations. The NPs also showed time-dependent cellular uptake for up to 24 h as determined using flow cytometry. Delivery of the siRNA using these NPs also resulted in significant inhibition of A549 and H460 cell proliferation in vitro, respectively.

CONCLUSIONS

The results demonstrate that the mPAE polymer based NPs show strong potential for siRNA delivery to lung cancer cells. It is anticipated that future modification can help improve the efficacy of nucleic acid delivery, leading to higher inhibition of lung cancer growth in vitro and in vivo.

Consequences of delay in screening, monitoring, and treatment of angiomyolipoma and tuberous sclerosis: A case report

BACKGROUND

Tuberous sclerosis complex (TSC) is a multisystem disorder that results in tumor growth in various organs. TSC can affect the kidneys in the form of renal angiomyolipomas and cysts that can lead to chronic kidney disease.

CASE PRESENTATION

A 38-year-old woman was referred to Kennedy Krieger Institute for comprehensive TSC management. Before referral, the patient had gone most of her life without a definite diagnosis of TSC despite visually-prominent signs such as forehead plaques, facial angiofibromas, and ungual fibromas. Eventually, complications of the disease led to the patient requiring hemodialysis at age 34 and a complete bilateral nephrectomy at age 36. However, the patient was not diagnosed with TSC until an evaluation at the National Institutes of Health at age 37. After becoming a patient at our clinic, a multidisciplinary approach was taken to provide comprehensive care by including various disciplines such as nephrology, neurology, pulmonology, ophthalmology, dentistry, dermatology, and cardiology.

DISCUSSION AND CONCLUSION

TSC consensus recommendations aid in diagnosis, monitoring, and treatment of TSC and its associated manifestations, including those involving the kidneys. Our case underscores the importance of early identification of TSC to prevent future complications and promotes use of a multidisciplinary team to provide comprehensive care.
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Sirolimus as an alternative treatment in patients with granulomatous-lymphocytic lung disease and humoral immunodeficiency with impaired regulatory T cells

BACKGROUND

One of the most frequent non-infectious complications of humoral immunodeficiencies with a CVID-like pattern is a particular form of inflammatory lung disease which is called granulomatous-lymphocytic interstitial lung disease (GLILD). Its development worsens patient prognosis, with a significant decrease in survival. Currently, there are no unified guidelines regarding its management, and different combinations of immunosuppressants have been used with variable success.

METHODS

Clinical and radiological data were collected from patient's medical charts. Flow cytometry was performed to characterize the immunological features with special focus in regulatory T cells (Tregs).

RESULTS

A 16-year-old girl with Kabuki syndrome and a 12-year-old boy, both with a CVID-like humoral immunodeficiency on immunoglobulin replacement treatment, developed during follow-up an inflammatory complication radiologically, clinically, and histologically compatible with GLILD. They required treatment, and sirolimus was started, with very good response and no serious side effects.

CONCLUSIONS

These 2 cases provide insight into the underlying local and systemic immune anomalies involved in the development of GLILD, including the possible role of Tregs. Combined chemotherapy is commonly used as treatment for GLILD when steroids fail, but there have been some reports of successful monotherapy. As far as we know, these are the first 2 GLILD patients treated successfully with sirolimus, suggesting the advisability of further study of mTOR inhibitors as a more targeted treatment for GLILD, if impairment in Tregs is demonstrated.

Efficacy and Safety of Mammalian Target of Rapamycin Inhibitor Use-Long-term Follow-up of First Tuberous Sclerosis Complex Patient Treated De Novo With Sirolimus After Kidney Transplantation: A Case Report

Mammalian target of rapamycin inhibitors (mTORI) are increasingly used in the treatment of tuberous sclerosis complex (TSC) and as immunosuppressants after organ transplantation. In TSC patients, mTORI are the treatment of choice after kidney transplantation. It is still under debate if benefits from long-term mTORI use will not be limited by side effects.

MATERIALS AND METHODS

We report long-term follow-up data of the first TSC patient after kidney transplantation treated with sirolimus de novo. In 2005, a female patient was transplanted with a kidney graft after bilateral nephrectomy due to angiomyolipoma. Initial immunosuppressive treatment consisted of antithymocyte globulin, methylprednisolone, tacrolimus, and, due to TSC diagnosis, sirolimus. Creatinine level at discharge was 1.2 mg/dL.

RESULTS

Long-term mTORI use resulted in skin lesion regression (angiofibromas, "confetti" skin lesions, shagreen patch) and disease stabilization in brain, abdominal, and chest magnetic resonance imaging/computed tomography scans. Pulmonary function tests showed improvement in restriction and slow deterioration in obstruction and diffusion parameters. Sirolimus related adverse reactions were hyperlipidemia and hypertriglyceridemia and respiratory and urinary tract infections. No gastrointestinal or hematologic symptoms occurred. Sirolimus concentrations ranged between 1.7 and 8.2 ng/mL (mean 4.01 ± 2.09 ng/mL). Since 2009 proteinuria and slow increase in creatinine level have been observed. No biopsy was performed to establish etiology and potential association with mTORI. In 2017 creatinine level was 2.2 mg/dL.

CONCLUSION

The case of the patient confirms clinical effectiveness and acceptable safety of long-term mTORI treatment. Long-term mTORI use requires meticulous patient observation to optimize dosage, achieve immunosuppressive effect, and improve TSC manifestations with minimal side effects.

Disulfide bond disrupting agents activate the unfolded protein response in EGFR- and HER2-positive breast tumor cells

Many breast cancer deaths result from tumors acquiring resistance to available therapies. Thus, new therapeutic agents are needed for targeting drug-resistant breast cancers. Drug-refractory breast cancers include HER2+ tumors that have acquired resistance to HER2-targeted antibodies and kinase inhibitors, and “Triple-Negative” Breast Cancers (TNBCs) that lack the therapeutic targets Estrogen Receptor, Progesterone Receptor, and HER2. A significant fraction of TNBCs overexpress the HER2 family member Epidermal Growth Factor Receptor (EGFR). Thus agents that selectively kill EGFR+ and HER2+ tumors would provide new options for breast cancer therapy. We previously identified a class of compounds we termed Disulfide bond Disrupting Agents (DDAs) that selectively kill EGFR+ and HER2+ breast cancer cells in vitro and blocked the growth of HER2+ breast tumors in an animal model. DDA-dependent cytotoxicity was found to correlate with downregulation of HER1-3 and Akt dephosphorylation. Here we demonstrate that DDAs activate the Unfolded Protein Response (UPR) and that this plays a role in their ability to kill EGFR+ and HER2+ cancer cells. The use of breast cancer cell lines ectopically expressing EGFR or HER2 and pharmacological probes of UPR revealed all three DDA responses: HER1-3 downregulation, Akt dephosphorylation, and UPR activation, contribute to DDA-mediated cytotoxicity. Significantly, EGFR overexpression potentiates each of these responses. Combination studies with DDAs suggest that they may be complementary with EGFR/HER2-specific receptor tyrosine kinase inhibitors and mTORC1 inhibitors to overcome drug resistance.

TFEB activation restores migration ability to Tsc1-deficient adult neural stem/progenitor cells

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder caused by mutations in either of two genes, TSC1 or TSC2, resulting in the constitutive activation of the mammalian target of rapamycin complex 1 (mTORC1). mTOR inhibitors are now considered the treatment of choice for TSC disease. A major pathological feature of TSC is the development of subependymal giant cell astrocytomas (SEGAs) in the brain. Nowadays, it is thought that SEGAs could be a consequence of aberrant aggregation and migration of neural stem/progenitor cells (NSPCs). Therefore, reactivation of cell migration of NSPCs might be the crucial step for the treatment of patients. In order to identify potential in vitro targets activating migration, we generated Tsc1-deficient NSPCs. These cells summarize most of the biochemical and morphological characteristics of TSC neural cells, such as the mTORC1 activation, the formation of abnormally enlarged astrocytes-like cells, the reduction of autophagy flux and the impairment of cell migration. Moreover, nuclear translocation, namely activation of the transcription factor EB (TFEB) was markedly impaired. Herein, we show that compounds such as everolimus, ionomycin and curcumin, which directly or indirectly stimulate TFEB nuclear translocation, restore Tsc1-deficient NSPC migration. Our data suggest that reduction of TFEB activation, caused by mTORC1 hyperactivation, contributes to the migration deficit characterizing Tsc1-deficient NSPCs. The present work highlights TFEB as a druggable protein target for SEGAs therapy, which can be additionally or alternatively exploited for the mTORC1-directed inhibitory approach.

Improvement in Renal Cystic Disease of Tuberous Sclerosis Complex After Treatment with Mammalian Target of Rapamycin Inhibitor

Renal cysts occur in approximately 50% of patients with tuberous sclerosis complex, but their clinical significance and response to treatment are unknown. Abdominal imaging of 15 patients with tuberous sclerosis complex-associated renal cystic disease who had received mammalian target of rapamycin inhibitor therapy for other tuberous sclerosis complex-related indications was evaluated. Reductions in cyst number, sum diameter, and volume were observed.

Management of everolimus-associated adverse events in patients with tuberous sclerosis complex: a practical guide

Tuberous sclerosis complex (TSC) is a genetic disorder characterised by highly variable comorbid dysfunction and subsequent morbidity. The mTOR inhibitor everolimus is indicated for the treatment of adult TSC patients with renal angiomyolipomas (AMLs) and for subependymal giant astrocytoma (SEGA) in both adults and children, based on data from the EXIST-1 and EXIST-2 trials. However, due to the historical predominance of everolimus in the oncology setting, some physicians who treat TSC patients may be unfamiliar with everolimus-associated adverse events (AEs) and appropriate management strategies. This article aims to serve as a resource for specialists including nephrologists, paediatricians, neurologists and geneticists who require practical guidance on the management of events such as non-infectious pneumonitis, rash, stomatitis, infections, and renal AEs. Additional consideration is given to drug interactions, hepatic impairment, fertility, and sexual maturation. Since patients with TSC receive clinical benefit from continued therapy, it is important that everolimus-related events are dealt with appropriately through strategies such as dose modification, interruption, the provision of supportive care, regular monitoring, and patient education.

Resistance to mTORC1 Inhibitors in Cancer Therapy: From Kinase Mutations to Intratumoral Heterogeneity of Kinase Activity

Targeting mTORC1 has been thoroughly explored in cancer therapy. Following encouraging preclinical studies, mTORC1 inhibitors however failed to provide substantial benefits in cancer patients. Several resistance mechanisms have been identified including mutations of mTOR and activation of alternate proliferation pathways. Moreover, emerging evidence discloses intratumoral heterogeneity of mTORC1 activity that further contributes to a reduced anticancer efficacy of mTORC1 inhibitors. Genetic heterogeneity as well as heterogeneous conditions of the tumor environment such as hypoxia profoundly modifies mTORC1 activity in tumors and hence influences the response of tumors to mTORC1 inhibitors. Intriguingly, the heterogeneity of mTORC1 activity also occurs towards its substrates at the single cell level, as mutually exclusive pattern of activation of mTORC1 downstream effectors has been reported in tumors. After briefly describing mTORC1 biology and the use of mTORC1 inhibitors in patients, this review will give an overview on concepts of resistance to mTORC1 inhibition in cancer with a particular focus on intratumoral heterogeneity of mTORC1 activity.

Somatic overgrowth disorders of the PI3K/AKT/mTOR pathway & therapeutic strategies

The phosphatidylinositol-3-kinase (PI3K)/AKT/mTOR signaling pathway plays an essential role in regulation of normal cell growth, metabolism, and survival. Somatic activating mutations in the PI3K/AKT/mTOR pathway are among the most common mutations identified in cancer, and have been shown to cause a spectrum of overgrowth syndromes including PIK3CA-Related Overgrowth Spectrum, Proteus syndrome, and brain overgrowth conditions. Clinical findings in these disorders may be isolated or multiple, including sporadic or mosaic overgrowth (adipose, skeletal, muscle, brain, vascular, or lymphatic), and skin abnormalities (including epidermal nevi, hyper-, and hypopigmented lesions), and have the potential risk of tumorigenesis. Key negative regulators of the PI3K-AKT signaling pathway include PTEN and TSC1/TSC2 and germline loss-of function mutations of these genes are established to cause PTEN Hamartoma Tumor Syndrome and Tuberous Sclerosis Complex. Mosaic forms of these conditions lead to increased activation of PI3K and mTOR at affected sites and there is phenotypic overlap between these conditions. All are associated with significant morbidity with limited options for treatment other than symptomatic therapies and surgeries. As dysregulation of the PI3K/AKT/mTOR pathway has been implicated in cancer, several small molecule inhibitors targeting different components of the PI3K/AKT/mTOR signaling pathway are under clinical investigation. The development of these therapies brings closer the prospect of targeting treatment for somatic PI3K/AKT/mTOR-related overgrowth syndromes. This review describes the clinical findings, gene function and pathogenesis of these mosaic overgrowth syndromes, and presents existing and future treatment strategies to reduce or prevent associated complications of these disorders. © 2016 Wiley Periodicals, Inc.

mTOR and MAPK: from localized translation control to epilepsy

Background

Epilepsy is one of the most common neurological diseases characterized by excessive hyperexcitability of neurons. Molecular mechanisms of epilepsy are diverse and not really understood. All in common is the misregulation of proteins that determine excitability such as potassium and sodium channels as well as GABA receptors; which are all known as biomarkers for epilepsy. Two recently identified key pathways involve the kinases mechanistic target of rapamycin (mTOR) and mitogen-activated protein kinases (MAPK). Interestingly, mRNAs coding for those biomarkers are found to be localized at or near synapses indicating a local misregulation of synthesis and activity.

Results

Research in the last decade indicates that RNA-binding proteins (RBPs) responsible for mRNA localization, stability and translation mediate local expression control. Among others, they are affected by mTOR and MAPK to guide expression of epileptic factors. These results suggest that mTOR/MAPK act on RBPs to regulate the fate of mRNAs, indicating a misregulation of protein expression at synapses in epilepsy.

Conclusion

We propose that mTOR and MAPK regulate RBPs, thereby guiding the local expression of their target-mRNAs encoding for markers of epilepsy. Thus, misregulated mTOR/MAPK-RBP interplay may result in excessive local synthesis of ion channels and receptors thereby leading to hyperexcitability. Continuous stimulation of synapses further activates mTOR/MAPK pathway reinforcing their effect on RBP-mediated expression control establishing the basis for epilepsy. Here, we highlight findings showing the tight interplay between mTOR as well as MAPK with RBPs to control expression for epileptic biomarkers.

Tuberous sclerosis complex: From molecular biology to novel therapeutic approaches

Tuberous sclerosis complex (TSC) is a rare multi-system disorder, primary manifestations of which are benign tumors and lesions in various organs of the body, including the brain. TSC patients often suffer from epilepsy, mental retardation, and autism spectrum disorder (ASD). Therefore, TSC serves as a model of epilepsy, ASD, and tumorigenesis. TSC is caused by the lack of functional Tsc1-Tsc2 complex, which serves as a major cellular inhibitor of mammalian Target of Rapamycin Complex 1 (mTORC1). mTORC1 is a kinase controlling most of anabolic processes in eukaryotic cells. Consequently, mTORC1 inhibitors, such as rapamycin, serve as experimental or already approved drugs for several TSC symptoms. However, rapalogs, although quite effective, need to be administered chronically and likely for a lifetime, since therapy discontinuation results in tumor regrowth and epilepsy recurrence. Recent studies revealed that metabolism and excitability (in the case of neurons) of cells lacking Tsc1-Tsc2 complex are changed, and these features may potentially be used to treat some of TSC symptoms. In this review, we first provide basic facts about TSC and its molecular background, to next discuss the newest findings in TSC cell biology that can be used to improve existing therapies of TSC and other diseases linked to mTORC1 hyperactivation. © 2016 IUBMB Life, 68(12):955-962, 2016.

Targeting mTOR to reduce Alzheimer-related cognitive decline: from current hits to future therapies

INTRODUCTION

The mTOR pathway is involved in the regulation of a wide repertoire of cellular functions in the brain and its dysregulation is emerging as a leitmotif in a large number of neurological disorders. In AD, altered mTOR signaling contributes to the inhibition of autophagy deposition of Aβ and tau aggregates and to the alteration of several neuronal metabolic pathways. Areas covered: In this review, we report all the current findings on the use of mTOR inhibitors (rapamycin, rapalogues) in the treatment of AD. These results support the role of mTOR inhibitors as potential therapeutic agents able to reduce AD hallmarks and recover cognitive performances. Expert commentary: Despite mTOR inhibitors appearing to be ideal compounds to counteract AD, further studies are needed in order to gain knowledge on the involvement of aberrant mTOR in AD, and to standardize a valuable therapeutic approach that can be translated to humans.

Normalizing translation through 4E-BP prevents mTOR-driven cortical mislamination and ameliorates aberrant neuron integration

Hyperactive mammalian target of rapamycin complex 1 (mTORC1) is a shared molecular hallmark in several neurodevelopmental disorders characterized by abnormal brain cytoarchitecture. The mechanisms downstream of mTORC1 that are responsible for these defects remain unclear. We show that focally increasing mTORC1 activity during late corticogenesis leads to ectopic placement of upper-layer cortical neurons that does not require altered signaling in radial glia and is accompanied by changes in layer-specific molecular identity. Importantly, we found that decreasing cap-dependent translation by expressing a constitutively active mutant of the translational repressor eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) prevents neuronal misplacement and soma enlargement, while partially rescuing dendritic hypertrophy induced by hyperactive mTORC1. Furthermore, overactivation of translation alone through knockdown of 4E-BP2 was sufficient to induce neuronal misplacement. These data show that many aspects of abnormal brain cytoarchitecture can be prevented by manipulating a single intracellular process downstream of mTORC1, cap-dependent translation.

Everolimus treatment among patients with tuberous sclerosis affects serum lipid profile

BACKGROUND

The purpose of the study was to evaluate lipid homeostasis before and after treatment of everolimus, the mammalian target of the rapamycin (mTOR) inhibitor, among patients with tuberous sclerosis complex (TSC).

METHODS

The study group consisted of 15 patients with a diagnosis of subependymal giant cell astrocytoma (SEGA) related to TSC. The following lipid parameters were determined: total serum cholesterol (TCh), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), total serum triglyceride (TG) concentration at baseline, then after three and 12 months of observation. The values were compared with those of age-matched healthy controls.

RESULTS

In the study group TCh, LDL and HDL levels at baseline were significantly higher than in the control group. TCh and LDL levels were positively correlated with baseline SDS-BMI in TSC patients. Everolimus treatment resulted in significant increases of TCh (from 192.04±40.51mg/dl to 210.74±51.12mg/dl and to 216.69±45.43mg/dl; p=0.0273) and LDL (from 113.21±38.72mg/dl to 133.88±50.71mg/dl and to 141.58±40.67mg/dl; p=0.0006) after three and 12 months respectively. The differences between the TCh and LDL levels at baseline and after 12 months of therapy were negatively correlated with baseline SDS-BMI. The observed increase of BMI after 12 months was correlated with increases in TCh and LDL levels.

CONCLUSIONS

Patients with TSC have disrupted lipid homeostasis before and during treatment with everolimus, which might be partially connected to the mTOR-dependent nutritional status of the patients. There is a need to develop strategies for children with TSC treated with everolimus, who experience hyperlipidemia.