TSC2 Research Articles

E2F7 promotes mammalian target of rapamycin inhibitor resistance in hepatocellular carcinoma after liver transplantation

The mammalian target of rapamycin (mTOR) pathway is frequently deregulated and has critical roles in cancer progression. mTOR inhibitor has been widely used in several kinds of cancers and is strongly recommended in patients with hepatocellular carcinoma (HCC) after liver transplantation (LT). However, the poor response to mTOR inhibitors due to resistance remains a challenge. Hypoxia-associated resistance limits the therapeutic efficacy of targeted drugs. The present study established models of HCC clinical samples and cell lines resistance to mTOR inhibitor sirolimus and screened out E2F7 as a candidate gene induced by hypoxia and promoting sirolimus resistance. E2F7 suppressed mTOR complex 1 via directly binding to the promoter of the TSC1 gene and stabilizes hypoxia-inducible factor-1α activating its downstream genes, which are responsible for E2F7-dependent mTOR inhibitor resistance. Clinically, low E2F7 expression could be an effective biomarker for recommending patients with HCC for anti-mTOR-based therapies after LT. Targeting E2F7 synergistically inhibited HCC growth with sirolimus in vivo. E2F7 is a promising target to reverse mTOR inhibition resistance. Collectively, our study points to a role for E2F7 in promoting mTOR inhibitor resistance in HCC and emphasizes its potential clinical significance in patients with HCC after LT.

73 (PB063) - Results from the NCI-MATCH ECOG-ACRIN Trial (EAY131) - Phase 2 Study of MLN0128 (TAK-228) in Patients with Tumors with TSC1 or TSC2 Mutations: Sub-protocol EAY131-M

Background: The NCI-MATCH trial was designed to assess the clinical efficacy of select targeted therapies in pts with specific mutations in a tumor agnostic fashion. Loss of function mutations in the tumor suppressor genes TSC1 and TSC2 have been shown to activate the mTORC1 pathway constitutively. TAK-228 is an orally available potent inhibitor of both TORC1 and TORC2 complexes. Subprotocol M is a phase 2 study to determine the effects of TAK-228 on pts whose tumors harbor TSC1 or TSC2 alterations. Materials and Methods: Patients with advanced metastatic solid tumors or lymphomas who progressed following at least 1 prior systemic therapy were accrued to NCI-MATCH for tumor molecular profiling, and those with functionally curated somatic TSC1 or TSC2 alterations were offered participation in sub-protocol M. Patients received TAK-228 3 mg daily for 28-day cycles until progression or intolerable toxicity. Results: 49 pts were enrolled on arm M with 4 pts deemed ineligible or never starting treatment, leaving 45 evaluable pts. The primary analysis includes 34 pts with centrally confirmed mutations (CM), 7 from the MATCH screening cohort assay and 27 from approved outside laboratories. Of the 34 CM pts, 17 were female (50%), median age 62 (22–87), 21 had received 3 or more lines of prior therapy (61.7%), all had ECOG PS 0-1. Tumor types included urothelial (4), renal (2), prostate (2), colorectal (6), pancreas (1), HCC (1), ovary (3), endometrial stromal sarcoma (2), cervical adenocarcinoma (1), TNBC (1), squamous lung (2), PEComa (2), spindle cell sarcoma (1), PNET (1), angiosarcoma of spleen (1), osteosarcoma (1), melanoma (1), and undifferentiated carcinoma (2). TSC2 alterations made up 17 of the CM pts and 25 of the evaluable pts. Of the 34 CM pts, there were 5 PR for a 14.7% ORR (90% CI 6.0%- 28.5%), 13 SD, 12 PD and 4 were unevaluable. The estimated 6-month PFS rate is 28.7% (90% CI 17.3%–47.5%) in CM pts. The five responders were endometrial stromal sarcoma (1), high grade angiosarcoma of the spleen (1), PNET (1), HCC (1), and renal clear cell carcinoma (1). 4/5 responders had TSC2 alterations. Two pts with squamous NSCLC had clinical benefit for greater than 6 mo. Most common emergent adverse events among the 45 evaluable pts included hyperglycemia, fatigue, nausea, anemia and diarrhea. Grade 3–4 treatment-related adverse events (TRAE) included creatinine increase (4), TTP (4), dysphagia (4), pruritis (4). No grade 5 TRAE were reported. Six pts came off study due to adverse events. Conclusions: While the primary endpoint of 6/34 (17.6% ORR) CM responses was not met, TAK-228 therapy had modest clinical activity in pts with various solid tumors exhibiting TSC1 or TSC2 alterations. The observation that 4/17 (23.5%) tumors harboring confirmed TSC2 alterations responded in this heavily pretreated population merits further investigation. NCT02465060. No conflict of interest.

Hyperactivation of mTORC1 in a double hit mutant zebrafish model of tuberous sclerosis complex causes increased seizure susceptibility and neurodevelopmental abnormalities.

Tuberous sclerosis complex (TSC) is a multisystem genetic disorder caused by pathogenic variants in TSC1 and TSC2 genes. TSC patients present with seizures and brain abnormalities such as tubers and subependymal giant cells astrocytoma (SEGA). Despite common molecular and clinical features, the severity of the disease varies greatly, even intrafamilially. The second hit hypothesis suggests that an additional, inactivating mutation in the remaining functional allele causes a more severe phenotype and therefore explains the phenotypic variability. Recently, second hit mutations have been detected frequently in mTORopathies. To investigate the pathophysiological effects of second hit mutations, several mouse models have been developed. Here, we opted for a double mutant zebrafish model that carries a LOF mutation both in the tsc2 and the depdc5 gene. To the best of our knowledge, this is the first time a second-hit model has been studied in zebrafish. Significantly, the DEP domain-containing protein 5 (DEPDC5) gene has an important role in the regulation of mTORC1, and the combination of a germline TSC2 and somatic DEPDC5 mutation has been described in a TSC patient with intractable epilepsy. Our depdc5 −/− x tsc2 −/− double mutant zebrafish line displayed greatly increased levels of mammalian target of rapamycin (mTORC1) activity, augmented seizure susceptibility, and early lethality which could be rescued by rapamycin. Histological analysis of the brain revealed ventricular dilatation in the tsc2 and double homozygotes. RNA-sequencing showed a linear relation between the number of differentially expressed genes (DEGs) and the degree of mTORC1 hyperactivity. Enrichment analysis of their transcriptomes revealed that many genes associated with neurological developmental processes were downregulated and mitochondrial genes were upregulated. In particular, the transcriptome of human SEGA lesions overlapped strongly with the double homozygous zebrafish larvae. The data highlight the clinical relevance of the depdc5 −/− x tsc2 −/− double mutant zebrafish larvae that showed a more severe phenotype compared to the single mutants. Finally, analysis of gene-drug interactions identified interesting pharmacological targets for SEGA, underscoring the value of our small zebrafish vertebrate model for future drug discovery efforts.

LysM-positive neurons drive Tuberous Sclerosis Complex (TSC)-associated brain lesions

Mutations of Tsc1 or Tsc2 can lead to excessive activation of mTORC1 and cause Tuberous Sclerosis Complex (TSC), which is an autosomal dominant genetic disease prominently characterized by seizures, mental retardation and multiorgan hamartoma. In TSC, pathological changes in the central nervous system are the leading cause of death and disability. In decades, series of rodent models have been established by mutating Tsc1 or Tsc2 genes in diverse neural cell lineages to investigate the underlying cellular and molecular mechanisms, however, the cellular origin triggering neural pathological changes in TSC is undetermined. In this study, we generated a novel mouse model involving conditional deletion of Tsc1 in lysozyme 2 (Lyz2)-positive cells which replicated several features of brain lesions including epileptic seizures, megalencephaly, highly enlarged pS6-positive neurons and astrogliosis. In addition, we confirmed that bone marrow-derived myeloid cells including microglia with Tsc1 deficiency are not the decisive lineage in the cerebral pathologies in TSC. These histological assays in our murine model indicate an essential contribution of Lyz2-positive neurons to TSC progression. The Lyz2-positive neural population-specific onset of Tsc1 loss in murine postnatal brain might be the key to pathological phenotypes. Our findings thus provided evidences supporting new insights into the role of Lyz2-positive neurons in TSC events.

Renal Transcriptome and Metabolome in Mice with Principal Cell-Specific Ablation of the Tsc1 Gene: Derangements in Pathways Associated with Cell Metabolism, Growth and Acid Secretion.

Tuberous sclerosis complex (TSC) is caused by mutations in the hamartin (TSC1) or tuberin (TSC2) genes. Using a mouse model of TSC renal cystogenesis that we have previously described, the current studies delineate the metabolic changes in the kidney and their relation to alterations in renal gene expression. To accomplish this, we compared the metabolome and transcriptome of kidneys from 28-day-old wildtype (Wt) and principal cell-specific Tsc1 KO (Tsc1 KO) mice using targeted 1H nuclear magnetic resonance targeted metabolomic and RNA-seq analyses. The significant changes in the kidney metabolome of Tsc1 KO mice included reductions in the level of several amino acids and significant decreases in creatine, NADH, inosine, UDP-galactose, GTP and myo-inositol levels. These derangements may affect energy production and storage, signal transduction and synthetic pathways. The pertinent derangement in the transcriptome of Tsc1 KO mice was associated with increased collecting duct acid secretion, active cell division and the up-regulation of signaling pathways (e.g., MAPK and AKT/PI3K) that suppress the TSC2 GTPase-activating function. The combined renal metabolome and transcriptome alterations observed in these studies correlate with the unregulated growth and predominance of genotypically normal A-intercalated cells in the epithelium of renal cysts in Tsc1 KO mice.

KRAS Pathway Alterations in Malignant Pleural Mesothelioma: An Underestimated Player.

Simple SummaryMalignant pleural mesothelioma (MPM) is a rare, incurable cancer. KRAS pathway alterations are frequent in human MPM but have been likely underestimated by next generation sequencing studies.Malignant pleural mesothelioma (MPM) is a rare, incurable cancer of the mesothelial cells lining the lungs and the chest wall that is mainly caused by asbestos inhalation. The molecular mechanisms of mesothelial carcinogenesis are still unclear despite comprehensive studies of the mutational landscape of MPM, and the most frequently mutated genes BAP1, NF2, CDKN2A, TP53, and TSC1 cannot cause MPM in mice in a standalone fashion. Although KRAS pathway alterations were sporadically detected in older studies employing targeted sequencing, they have been largely undetected by next generation sequencing. We recently identified KRAS mutations and copy number alterations in a significant proportion of MPM patients. Here, we review and analyze multiple human datasets and the published literature to show that, in addition to KRAS, multiple other genes of the KRAS pathway are perturbed in a significant proportion of patients with MPM.

Dissecting the roles of the Tuberin protein in the subcellular localization of the G2/M Cyclin, Cyclin B1.

Tuberin is a major component of the protein regulatory complex known as the Tuberous Sclerosis Complex and plays a crucial role in cell cycle progression and protein synthesis. Mutations in the Tuberin gene, TSC2, lead to the formation of benign tumors in many organ systems and causes the Tuberous Sclerosis Complex disorder. Genotypes ranging from point mutations to large deletions in the TSC2 gene have been clinically characterized with a wide range of phenotypes from skin tumors to large brain tumors. Our lab has previously demonstrated that Tuberin can directly bind and regulate the timing of nuclear transport of the G2/M cyclin, Cyclin B1. Herein we study the consequence of one clinically relevant truncation in the Tuberin protein on cell cycle function. We demonstrate that exogenous expression of a fragment of the N-term region of Tuberin alters the subcellular localization of Cyclin B1 and increases cell proliferation. This adds to our body of information about the residues within Tuberin responsible for regulating the cytoplasmic retention of Cyclin B1 and supports the phenotypic data seen in the clinic with Tuberous Sclerosis Complex patients harbouring similar large deletions in Tuberin.

A Clinical Challenge Case of Bilateral Giant Renal Angiomyolipoma Associated With Tuberous Sclerosis Complex

A 27-year-old female was referred to the urology clinic because of an incidentally found bilateral giant renal angiomyolipoma associated with tuberous sclerosis complex (TSC-RAML) discovered during workup for menorrhagia. Six years ago, she began to develop a bulging belly, which she thought was due to obesity. She had multiple angiofibromas on her face, multiple toenail fibromas on her toes (Fig. 1). Whole-genome sequencing analysis of plasma revealed pathogenic mutation of TSC2 gene (base change: C.1513C >T;amino acid change: p.R505X; Mutation abundance: heterozygous; GloriousMed Technology, China).

Raptor downregulation rescues neuronal phenotypes in mouse models of Tuberous Sclerosis Complex

Tuberous Sclerosis Complex (TSC) is a neurodevelopmental disorder caused by mutations in the TSC1 or TSC2 genes, which encode proteins that negatively regulate mTOR complex 1 (mTORC1) signaling. Current treatment strategies focus on mTOR inhibition with rapamycin and its derivatives. While effective at improving some aspects of TSC, chronic rapamycin inhibits both mTORC1 and mTORC2 and is associated with systemic side-effects. It is currently unknown which mTOR complex is most relevant for TSC-related brain phenotypes. Here we used genetic strategies to selectively reduce neuronal mTORC1 or mTORC2 activity in mouse models of TSC. We find that reduction of the mTORC1 component Raptor, but not the mTORC2 component Rictor, rebalanced mTOR signaling in Tsc1 knock-out neurons. Raptor reduction was sufficient to improve several TSC-related phenotypes including neuronal hypertrophy, macrocephaly, impaired myelination, network hyperactivity, and premature mortality. Raptor downregulation represents a promising potential therapeutic intervention for the neurological manifestations of TSC.

Generation of TSC1 knockout induced pluripotent stem cell (iPSC) line

The TSC1 gene is a tumor suppressor gene that encodes for the growth inhibitory protein hamartin. It was founded clinically relevant to tuberous sclerosis complex (TSC) and related epilepsy. Variants in TSC1 resulted in tuberous sclerosis, focal cortical dysplasia (FCD) Type II, pulmonary lymphangioleiomyomatosis and change in everolimus sensitivity. Here, we generated induced pluripotent stem cells (iPSC) from a normal individual by electroporation of peripheral blood mononuclear cells (PBMC), and further generated TSC1-knockout human iPSC line via CRISPR/Cas9 gene editing. The resulting iPSCs had normal karyotype, free of genomically integrated epitomal plasmids, expressed pluripotency markers, and maintained trilineage differentiation potential.

Radiological Characteristics of Renal Lesions During Tuberous Sclerosis Complex: Impact of Mechanistic Target of Rapamycin Inhibitor Treatment

Tuberous sclerosis complex (TSC) is an autosomal dominant multisystemic disorder.1 Pathogenic variants in TSC1 or TSC2 gene lead to hyperactivation of the mammalian target of rapamycin (mTOR) signaling pathway, with a consequent deregulation of cell growth and the development of hamartomas. This tumors are benign, but they can cause life-threatening hemorrhage or organ failure in vital organs, such as the kidney, with angiomyolipoma (AML).1 AML found in 60% to 80% of patients with TSC are tumors composed of smooth muscle-like cells, adipocyte-like cells, and epithelioid cells.

MTOR Modulates the Endoplasmic Reticulum Stress-Induced CD4+ T Cell Apoptosis Mediated by ROS in Septic Immunosuppression.

Introduction When sepsis attacks the body, the excessive reactive oxygen species (ROS) production can result to endoplasmic reticulum stress (ERS) and eventually cause lymphocyte apoptosis. The mammalian target of rapamycin (mTOR) is essential for regulating lymphocyte apoptosis; we hypothesized that it mediates CD4+ T cell apoptosis during ROS-related ERS. Method We, respectively, used ROS and ERS blockers to intervene septic mice and then detected ERS protein expression levels to verify the relationship between them. Additionally, we constructed T cell-specific mTOR and TSC1 gene knockout mice to determine the role of mTOR in ROS-mediated, ERS-induced CD4+ T cell apoptosis. Results Blocking ROS significantly suppressed the CD4+ T cell apoptosis associated with the reduction in ERS, as revealed by lower levels of GRP78 and CHOP. ERS rapidly induced mTOR activation, leading to the induction of CD4+ T cell apoptosis. However, mTOR knockout mice displayed reduced expression of apoptotic proteins and less ER vesiculation and expansion than what was observed in the wild-type sepsis controls. Conclusion By working to alleviate ROS-mediated, ERS-induced CD4+ T cell apoptosis, the mTOR pathway is vital for CD4+ T cell survival in sepsis mouse model.

Characterization of Pyrenophora tritici-repentis (tan spot of wheat) races in Kazakhstan

Tan spot, caused by Pyrenophora tritici-repentis, is an economically important foliar disease of wheat in Kazakhstan. Population structure of the pathogen changes every year due to climate change. This study aimed to characterize the race structure of P. tritici-repentis isolates recovered from wheat in south and north Kazakhstan, and identify tan spot resistance in host genotypes based on disease phenotypes and molecular screening. Virulence profiles were determined within 40 isolates of the pathogen from wheat crops during the 2020 growing season. Seven races, (1, 3, 4, 5, 6, 7 and 8) were identified. A collection of 80 wheat accessions, including promising lines and cultivars from Kazakhstan and Russia, were evaluated for their reactions to races 1 and 5 of the pathogen, and to Ptr ToxA and Ptr ToxB, using greenhouse assessments and molecular markers diagnostic for the Tsn1 and Tsc2 genes. From a practical viewpoint, 18 wheat genotypes were insensitive to the two races and the two Ptr toxins. This resistant germplasm can be used in breeding programmes aiming to develop wheat varieties resistant to P. tritici-repentis.

Synaptic hyperexcitability of cytomegalic pyramidal neurons contributes to epileptogenesis in tuberous sclerosis complex.

SUMMARYTuberous sclerosis complex (TSC) is a developmental disorder associated with epilepsy, autism, and cognitive impairment. Despite inactivating mutations in the TSC1 or TSC2 genes and hyperactive mechanistic target of rapamycin (mTOR) signaling, the mechanisms underlying TSC-associated neurological symptoms remain incompletely understood. Here we generate a Tsc1 conditional knockout (CKO) mouse model in which Tsc1 inactivation in late embryonic radial glia causes social and cognitive impairment and spontaneous seizures. Tsc1 depletion occurs in a subset of layer 2/3 cortical pyramidal neurons, leading to development of cytomegalic pyramidal neurons (CPNs) that mimic dysplastic neurons in human TSC, featuring abnormal dendritic and axonal overgrowth, enhanced glutamatergic synaptic transmission, and increased susceptibility to seizure-like activities. We provide evidence that enhanced synaptic excitation in CPNs contributes to cortical hyperexcitability and epileptogenesis. In contrast, astrocytic regulation of synapse formation and synaptic transmission remains unchanged after late embryonic radial glial Tsc1 inactivation, and astrogliosis evolves secondary to seizures.

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.

Systematic review of mTOR inhibitor treatment, biomarkers and prophylaxis for tuberous sclerosis complex-associated seizures

Tuberous sclerosis complex (TSC) is a major genetic cause of epilepsy, characterised by benign multi-system tumours (eg brain, kidney and skin) and neurological disorders (eg epilepsy, autism and learning impairment). Mutations in TSC1 and TSC2 genes result in hyperactivation of mammalian target of

Modeling tuberous sclerosis complex with human induced pluripotent stem cells.

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder with a birth incidence of 1:6000 in the United States that is characterized by the growth of non-cancerous tumors in multiple organ systems including the brain, kidneys, lungs, and skin. Importantly, TSC is also associated with significant neurological manifestations including epilepsy, TSC-associated neuropsychiatric disorders, intellectual disabilities, and autism spectrum disorder. Mutations in the TSC1 or TSC2 genes are well-established causes of TSC, which lead to TSC1/TSC2 deficiency in organs and hyper-activation of the mammalian target of rapamycin signaling pathway. Animal models have been widely used to study the effect of TSC1/2 genes on the development and function of the brain. Despite considerable progress in understanding the molecular mechanisms underlying TSC in animal models, a human-specific model is urgently needed to investigate the effects of TSC1/2 mutations that are unique to human neurodevelopment. Literature reviews and research articles were published in PubMed-indexed journals. Human-induced pluripotent stem cells (iPSCs), which capture risk alleles that are identical to their donors and have the capacity to differentiate into virtually any cell type in the human body, pave the way for the empirical study of previously inaccessible biological systems such as the developing human brain. In this review, we present an overview of the recent progress in modeling TSC with human iPSC models, the existing limitations, and potential directions for future research.

Tuberous sclerosis and risk of skin cancer: A nationwide cohort study in the United States

To the Editor: Tuberous sclerosis (TSC) is an autosomal dominant genetic syndrome affecting 1 in 6000 individuals.1 Patients with TSC can develop benign tumors of the kidney, heart, skin, and brain.1 TSC is caused by loss of function mutations in the tumor suppressor genes TSC1 or TSC2, leading to hyperactivation of the mammalian target of rapamycin (mTOR) signaling pathways and uninhibited cell cycle progression.1 Although patients with TSC often present to dermatology clinics for skin concerns, the risk of skin cancer in individuals with TSC has not been systematically quantified.

IMG-15. Radiomic Profiling of Pediatric Low-Grade Glioma Improves Risk Stratification Beyond Clinical Measures

Abstract PURPOSE: Treatment response is heterogeneous among patients with pediatric low-grade glioma (pLGG), the most frequent childhood brain tumor. Upfront prediction of progression-free survival (PFS) may facilitate more personalized treatment planning and improve outcomes for the pLGG patients. In this work, we explored the additive value of radiomics to clinical measures for prediction of PFS in pLGGs. We further sought associations between the derived risk groups and underlying alterations in key genomic and transcriptomic variables. METHODS: Quantitative radiomic features were extracted from pre-operative multi-parametric MRI scans (T1, T1-post, T2, T2-FLAIR) of 96 patients with newly diagnosed pLGG (median age, 8.59, range, 0.35-18.87 years; median PFS, 25.23, range, 3.03-124.83 months). Multivariate Cox proportional hazard’s (Cox-PH) regression models were fitted using 5-fold cross-validation on a training cohort of 68 subjects and tested on 28 patients. Three models were generated using (1) only clinical variables (age, sex, and extent of tumor resection), (2) radiomic features, and (3) clinical and radiomic variables. The dimensionality of radiomic features in Cox-PH models was reduced by applying Elastic Net regularization penalty to identify a subset of variables that are most predictive of PFS. The patients were then stratified into three groups of high, medium, and low-risk based on model predictions. RESULTS: Cox-PH modeling resulted in a concordance index (c-index) of 0.55 for clinical data, 0.65 for radiomics, and 0.73 for a combination of clinical and radiomic variables, highlighting the additive value of radiomics to the readily available clinical information in prediction of PFS. Radiogenomic assessments revealed significant differences in expression of BRAF, NF1, TSC1, ALK (p<0.01), and RB1 (p<0.05) genes in the high-risk group, compared to the medium and low-risk groups. CONCLUSION: Our results demonstrate the value of integrating radiomics with clinical measures to improve risk assessment of patients with pLGG through improved pretreatment prediction of PFS.

LGG-49. Subependymal giant cell astrocytoma associated with a cortical tuber: A case report

Subependymal giant cell astrocytomas (SEGAs) are circumscribed gliomas strongly associated with tuberous sclerosis (TS). TS, a rare genetic disorder caused by inactivating mutations in either of the TSC genes (TSC1/2), leads to upregulation of the mTOR pathway and consecutive cell growth. CNS manifestations other than SEGAs include cortical tubers, white matter glioneuronal hamartomas and subependymal nodules (SENs), which, although regarded as distinct morphological phenotypes, share certain histological characteristics including ballooned astrocytes and giant ganglion-like cells. SEGAs, thought to develop from the median ganglionic eminence (MGE), are most commonly located periventricularly. However, rare cases of extraventricular SEGAs have been reported. We report a case of a cortico-subcortically located SEGA in a TS patient. A two-month-old female TS patient with multiple cortical tubers presented with treatment-resistant epilepsy. A 4cm sized tuber located in the right temporal lobe, showing a transmantle sign on MRI but no typical imaging appearance of SEGA, was surgically resected. Histological evaluation revealed typical morphological characteristics of a tuber with dysmorphic neurons, balloon cells and calcifications in the cortex and adjacent white matter. Focally, a cortico-subcortically located, well delineated area with increased cellularity and morphological features of a SEGA was found. Single mitotic figures were detectable. Immunhistochemically, these cells were strongly positive for GFAP, vimentin, and nestin. Scattered S100-, NeuN-, MAP2- and SMI32-positive cells were present. No expression of class-III-b-tubulin and TTF1a was found. pS6 was expressed in a small fraction of cells. CD34 showed a dense capillary network within the lesion. This case is consistent with prior case reports of SEGA-tissue in tubers of TS patients. However, the SEGA tissue of this case did not display TTF1a-expression, characteristic for SEGAs and considered as a marker for cells originating from the MGE, thus implying a different cellular lineage.