Similar trends in serum VEGF-D levels and kidney angiomyolipoma responses with longer duration sirolimus treatment in adults with tuberous sclerosis

Tuberous Sclerosis Complex and the kidneys: what nephrologists need to know

Tuberous sclerosis complex (TSC) is an autosomal dominant disease characterized by the development of hamartomas in the central nervous system, heart, skin, lungs, and kidneys and other manifestations including seizures, cortical tubers, radial migration lines, autism and cognitive disability. The disease is associated with pathogenic variants in the TSC1 or TSC2 genes, resulting in the hyperactivation of the mTOR pathway, a key regulator of cell growth and metabolism. Consequently, the hyperactivation of the mTOR pathway leads to abnormal tissue proliferation and the development of solid tumors. Kidney involvement in TSC is characterized by the development of cystic lesions, renal cell carcinoma and renal angiomyolipomas, which may progress and cause pain, bleeding, and loss of kidney function. Over the past years, there has been a notable shift in the therapeutic approach to TSC, particularly in addressing renal manifestations. mTOR inhibitors have emerged as the primary therapeutic option, whereas surgical interventions like nephrectomy and embolization being reserved primarily for complications unresponsive to clinical treatment, such as severe renal hemorrhage. This review focuses on the main clinical characteristics of TSC, the mechanisms underlying kidney involvement, the recent advances in therapy for kidney lesions, and the future perspectives.

Cerebral vascular and blood brain-barrier abnormalities in a mouse model of epilepsy and tuberous sclerosis complex

OBJECTIVE

Tuberous sclerosis complex (TSC) is a genetic disorder, characterized by tumor formation in the brain and other organs, and severe neurological symptoms, such as epilepsy. Abnormal vascular endothelial growth factor (VEGF) expression may promote angiogenesis in kidney and lung tumors in TSC and has been identified in brain specimens from TSC patients, but the role of VEGF and vascular abnormalities in neurological manifestations of TSC is poorly defined. In this study, we investigated abnormalities in brain VEGF expression, cerebral blood vessel anatomy, and blood-brain barrier (BBB) structure and function in a mouse model of TSC.

METHODS

Tsc1GFAP CKO mice were used to investigate VEGF expression and vascular abnormalities in the brain by Western blotting and immunohistochemical analysis of vascular and BBB markers. In vivo two-photon imaging was used to assess BBB permeability to normally impenetrable fluorescently labeled compounds. The effect of mechanistic target of rapamycin (mTOR) pathway inhibitors, VEGF receptor antagonists (apatinib), or BBB stabilizers (RepSox) was assessed in some of these assays, as well as on seizures by video-electroencephalography.

RESULTS

VEGF expression was elevated in cortex of Tsc1GFAP CKO mice, which was reversed by the mTOR inhibitor rapamycin. Tsc1GFAP CKO mice exhibited increased cerebral angiogenesis and vascular complexity in cortex and hippocampus, which were reversed by the VEGF receptor antagonist apatinib. BBB permeability was abnormally increased and BBB-related tight junction proteins occludin and claudin-5 were decreased in Tsc1GFAP CKO mice, also in an apatinib- and RepSox-dependent manner. The BBB stabilizer (RepSox), but not the VEGF receptor antagonist (apatinib), decreased seizures and improved survival in Tsc1GFAP CKO mice.

SIGNIFICANCE

Increased brain VEGF expression is dependent on mTOR pathway activation and promotes cerebral vascular abnormalities and increased BBB permeability in a mouse model of TSC. BBB modulation may affect epileptogenesis and represent a rational treatment for epilepsy in TSC.

UPLC-MS based integrated plasma proteomic and metabolomic profiling of TSC-RAML and its relationship with everolimus treatment

Aim: To profile the plasma proteomics and metabolomics of patients with renal cysts, sporadic angiomyolipoma (S-AML) and tuberous sclerosis complex related angiomyolipoma (TSC-RAML) before and after everolimus treatment, and to find potential diagnostic and prognostic biomarkers as well as reveal the underlying mechanism of TSC tumorigenesis. Materials and Methods: We retrospectively measured the plasma proteins and metabolites from November 2016 to November 2017 in a cohort of pre-treatment and post-treatment TSC-RAML patients and compared them with renal cyst and S-AML patients by ultra-performance liquid chromatography-mass spectrometer (UPLC-MS). The tumor reduction rates of TSC-RAML were assessed and correlated with the plasma protein and metabolite levels. In addition, functional analysis based on differentially expressed molecules was performed to reveal the underlying mechanisms. Results: Eighty-five patients with one hundred and ten plasma samples were enrolled in our study. Multiple proteins and metabolites, such as pre-melanosome protein (PMEL) and S-adenosylmethionine (SAM), demonstrated both diagnostic and prognostic effects. Functional analysis revealed many dysregulated pathways, including angiogenesis synthesis, smooth muscle proliferation and migration, amino acid metabolism and glycerophospholipid metabolism. Conclusion: The plasma proteomics and metabolomics pattern of TSC-RAML was clearly different from that of other renal tumors, and the differentially expressed plasma molecules could be used as prognostic and diagnostic biomarkers. The dysregulated pathways, such as angiogenesis and amino acid metabolism, may shed new light on the treatment of TSC-RAML.

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.

Improvement in Impaired Social Cognition but Not Seizures by Everolimus in a Child with Tuberous Sclerosis-Associated Autism through Increased Serum Antioxidant Proteins and Oxidant/Antioxidant Status

We investigated the effect of the mammalian target of rapamycin (mTOR) inhibitor everolimus on tuberous sclerosis complex- (TSC-) associated autistic symptoms and focal seizures with impaired awareness in a female child with TSC. We further evaluated the relationship between improved autistic symptoms and seizures and increased the serum levels of the antioxidant proteins, ceruloplasmin (Cp) and transferrin (Tf), and oxidant-antioxidant status indicated by the oxidant marker oxidized low-density lipoprotein (ox-LDL) and the antioxidant marker total antioxidant power (TAP). Everolimus treatment improved impaired social cognition and autistic behaviors; however, seizure and epileptic activity persisted. Serum Cp and Tf levels gradually increased in response to improved autistic symptoms. Serum TAP levels gradually decreased from baseline to the lowest value at 16 weeks and then increased at 24 weeks, showing a trend toward decreased total score of the Aberrant Behavior Checklist. This study revealed that everolimus treatment improved impaired social cognition with increased serum levels of the copper mediator (Cp) and iron mediator (Tf) via homeostatic control of mTOR activity accompanied by overlap of the oxidant-antioxidant system. Everolimus had no effect on TSC-related epileptiform discharges, and thus, the autistic symptoms and epileptic activity may be two independent end results of a common central nervous system disorder including mTOR hyperactivity. This trial is registered with JMAS-IIA00258.

CT characteristics predict the response to everolimus or sirolimus of renal angiomyolipomas in patients with tuberous sclerosis complex

OBJECTIVE

To investigate factors influencing the volume response of everolimus and sirolimus in tuberous sclerosis complex (TSC) associated-angiomyolipomas (AML).

METHODS

A retrospective analysis of 30 cases of TSC-AML treated by mTOR inhibitors (everolimus 18 cases, and sirolimus 12 cases) between April 2014 and November 2017 at our center was carried out. Epidemiological data, therapeutic response and influence factors were reviewed and analyzed. Age, sex, associated with SEGA and/or LAM or not, plasma rapamycin concentration, AML volume at baseline, and mean CT value of AML in the maximum cross-section at baseline were analyzed as potential influencing factors.

RESULTS

Eighteen patients with 32 lesions in everolimus group and 12 patients with 15 lesions in sirolimus group were included. There was no statistically significant difference of baseline characteristics except for involved side (P = 0.008) between two groups. The mean volume of AML was 1000 ± 1276 cm³ at baseline and 633 ± 1121 cm³ at 6 months after treatment (P < 0.001) in everolimus group, and 1984 ± 2861 cm³ at baseline and 1733 ± 2533 cm³ at 6 months after treatment (P = 0.001) in sirolimus group, respectively. The mean volume reduction of the AML in everolimus and sirolimus groups were 55.56% ± 23.79% and 30.5% ± 22.8% (P = 0.001). Stepwise multiple linear regression analysis revealed that factors influencing the short-term volume response of everolimus and sirolimus for TSC-associated AML were AML volume at baseline (P < 0.001 and 0.038, respectively) and mean CT value at baseline (P < 0.001 and 0.020, respectively). The rates of ≥ 50% volume reduction in high CT value group was much higher than that in low CT value group (90.5% vs. 18.2%, P < 0.001).

CONCLUSIONS

Everolimus at 10 mg daily might be more effective than sirolimus at 2 mg daily in treatment of patients with TSC-AML. AML volume and mean CT value at baseline were factors influencing the short-term volume response of everolimus or sirolimus for TSC-AML.

Tsc2 disruption in mesenchymal progenitors results in tumors with vascular anomalies overexpressing Lgals3

Increased mTORC1 signaling from TSC1/TSC2 inactivation is found in cancer and causes tuberous sclerosis complex (TSC). The role of mesenchymal-derived cells in TSC tumorigenesis was investigated through disruption of Tsc2 in craniofacial and limb bud mesenchymal progenitors. Tsc2cKO^Prrx1-cre mice had shortened lifespans and extensive hamartomas containing abnormal tortuous, dilated vessels prominent in the forelimbs. Abnormalities were blocked by the mTORC1 inhibitor sirolimus. A Tsc2/mTORC1 expression signature identified in Tsc2-deficient fibroblasts was also increased in bladder cancers with TSC1/TSC2 mutations in the TCGA database. Signature component Lgals3 encoding galectin-3 was increased in Tsc2-deficient cells and serum of Tsc2cKO^Prrx1-cre mice. Galectin-3 was increased in TSC-related skin tumors, angiomyolipomas, and lymphangioleiomyomatosis with serum levels in patients with lymphangioleiomyomatosis correlating with impaired lung function and angiomyolipoma presence. Our results demonstrate Tsc2-deficient mesenchymal progenitors cause aberrant morphogenic signals, and identify an expression signature including Lgals3 relevant for human disease of TSC1/TSC2 inactivation and mTORC1 hyperactivity.

DOI:http://dx.doi.org/10.7554/eLife.23202.001

Tuberous sclerosis complex is a genetic condition that causes non-cancerous tumours with lots of blood vessels. It is caused by mutations that inactivate either of two genes known as TSC1 and TSC2. A signalling molecule called mTOR also contributes to the disease, and drugs that block its activity provide some relief for patients. However, mTOR regulates a wide variety of molecules and so researchers are looking for which ones are responsible for the formation of the tumours.

Mesenchymal cells produce bone, muscle and other structural tissues in the body. They also support the formation of blood vessels. Mice – which are often used as model animals in health research – also have mesenchymal cells and a gene that is very similar to the human TSC2 gene (known as Tsc2). Klover et al. hypothesized that disrupting the Tsc2 gene specifically in the mesenchymal cells of mice may mimic aspects of tuberous sclerosis complex in humans.

The experiments show that disrupting Tsc2 in mesenchymal cells does indeed mimic features of the human disease; the mice had shorter lifespans and they developed many tumours with dilated and winding blood vessels. Treating the mice with a drug that inhibits mTOR caused the tumours to shrink. Further experiments show that the loss of Tsc2 alters the production of many proteins involved metabolism, cell growth and sensing the levels of oxygen. For example, mouse cells that lack Tsc2 produce more of a protein called galectin-3, which appears to help blood vessels and tumours to grow in cancers.

Klover et al. also studied tumours from patients with tuberous sclerosis complex and a lung disease that is caused by mutations in TSC2 (called lymphangioleiomyomatosis). The experiments found that many tumours produce higher levels of galactin-3 than normal cells. Bladder cancers with mutations in TSC1 or TSC2 also had higher levels of galectin-3, suggesting that other diseases linked with mutations in these genes may also result in increased production of galectin-3.

The findings of Klover et al. suggest that galectin-3 may be a useful marker to assess the severity of tuberous sclerosis complex, lymphangioleiomyomatosis and to detect cancers with mutations in TSC1 or TSC2. The next step is to investigate whether galectin-3 alters blood vessels and tumour growth in these conditions.

DOI:http://dx.doi.org/10.7554/eLife.23202.002

Optimal treatment of tuberous sclerosis complex associated renal angiomyolipomata: a systematic review

Renal angiomyolipomata associated with tuberous sclerosis complex are often bilateral, multiple and progressive. They cause significant morbidity and mortality in older children and adults. Surveillance and pre-emptive treatment reduce this risk. Recent research suggests treatment with mammalian target of rapamycin inhibitors is better at preventing bleeding, recurrence, and preserving renal function than percutaneous embolization.

Regulation of expression level of fms-like tyrosine kinase-4 is related to osteoclast differentiation

INTRODUCTION

The aim of this study is to determine whether regulation of the expression level of fms-like tyrosine kinase-4 (Flt-4) is related to osteoclast differentiation.

MATERIAL AND METHODS

Osteoclast formation and differentiation of mouse bone marrow cells and RAW264.7 cells were performed. To induce osteoclast differentiation, RANKL (50 ng/ml) with or without vascular endothelial growth factor-C (VEGF-C) and vascular endothelial growth factor-D (VEGF-D) was added to mouse bone marrow cells and RAW264.7 cells. Then cells were examined under a microscope. TRAP-positive cells with 3 nuclei or more were considered as osteoclasts and counted. The Flt-4 gene was knocked down by transfection of siRNAs against Flt-4. Immunoblot analyses were performed.

RESULTS

The osteoclast formation assay indicated that VEGF-C resulted in 500 or 450 vs. 100 (p < 0.05) of osteoclasts in mouse bone marrow cells and RAW264.7 cells, respectively. Vascular endothelial growth factor-D resulted in about 600 or 630 vs. 100 (p < 0.05) of osteoclasts for both mouse bone marrow cells and RAW264.7 cells. The knock-down of Flt-4 expression abolished the induction by VEGF-C or VEGF-D, resulting in induction similar to that of the negative control PBS.

CONCLUSIONS

Both VEGF-C and VEGF-D can induce osteoclast differentiation in the presence of the receptor activator of nuclear factor κB ligand. Down-regulation of expression level of Flt-4 protein abolishes osteoclast differentiation induced by VEGF-C or VEGF-D.

Pharmacokinetics and pharmacodynamics of everolimus in patients with renal angiomyolipoma and tuberous sclerosis complex or lymphangioleiomyomatosis

AIMS

The purpose was to determine the exposure-response relationship of everolimus in patients with angiomyolipoma from the EXIST-2 trial and to analyze the correlation between exposure and plasma concentrations of angiogenic biomarkers in these patients.

METHODS

One hundred and eighteen patients with angiomyolipoma associated with tuberous sclerosis complex (TSC) or sporadic lymphangioleiomyomatosis (sLAM) were randomly assigned 2 : 1 to receive everolimus 10 mg (n = 79) or placebo (n = 39) once daily. Blood samples for determining everolimus concentration were collected at weeks 2, 4, 12, 24 and 48 during double-blind treatment. Plasma samples for biomarker analysis were collected at baseline and weeks 4, 12, 24, 36, 48 and at the end of treatment. Concentrations of eight angiogenic biomarkers associated with tumour growth were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Peak and trough concentrations of everolimus in blood remained stable over time and similar to those reported in other indications. Substantial pharmacodynamic effects were observed in the everolimus, but not placebo, arm for three biomarkers: After 24 weeks of treatment, reduction of vascular endothelial growth factor D (VEGF-D) and collagen type IV (COL-IV) (mean fold-changes with 95% confidence intervals [CI] were 0.36 [0.33, 0.40], and 0.54 [0.51, 0.57], respectively, P < 0.001 for both), along with increased VEGF-A (mean fold-change of 1.59 [1.39, 1.80], P < 0.001), were seen. Furthermore, baseline VEGF-D and COL-IV levels were associated with angiomyolipoma size at baseline and with angiomyolipoma response to everolimus.

CONCLUSIONS

These findings suggest that plasma angiogenic markers may provide an objective measure of patient response to everolimus.

Gene-expression profiling elucidates molecular signaling networks that can be therapeutically targeted in vestibular schwannoma

OBJECT

Vestibular schwannomas (VS) are common benign tumors of the vestibular nerve that cause significant morbidity. The current treatment strategies for VS include surgery or radiation, with each treatment option having associated complications and side effects. The transcriptional landscape of schwannoma remains largely unknown.

METHODS

In this study the authors performed gene-expression profiling of 49 schwannomas and 7 normal control vestibular nerves to identify tumor-specific gene-expression patterns. They also interrogated whether schwannomas comprise several molecular subtypes using several transcription-based clustering strategies. The authors also performed in vitro experiments testing therapeutic inhibitors of over-activated pathways in a schwannoma cell line, namely the PI3K/AKT/mTOR pathway.

RESULTS

The authors identified over 4000 differentially expressed genes between controls and schwannomas with network analysis, uncovering proliferation and anti-apoptotic pathways previously not implicated in VS. Furthermore, using several distinct clustering technologies, they could not reproducibly identify distinct VS subtypes or significant differences between sporadic and germline NF2-associated schwannomas, suggesting that they are highly similar entities. The authors identified overexpression of PI3K/AKT/mTOR signaling networks in their gene-expression study and evaluated this pathway for therapeutic targeting. Testing the compounds BEZ235 and PKI-587, both novel dual inhibitors of PI3K and mTOR, attenuated tumor growth in a preclinical cell line model of schwannoma (HEI-293). In vitro findings demonstrated that pharmacological inhibition of the PI3K/AKT/mTOR pathway with next-generation compounds led to decreased cell viability and increased cell death.

CONCLUSIONS

These findings implicate aberrant activation of the PI3K/AKT/mTOR pathway as a molecular mechanism of pathogenesis in VS and suggest inhibition of this pathway as a potential treatment strategy.