Mutations In Tuberous Sclerosis Complex Genes Research Articles

The Bi-Steric Inhibitor RMC-5552 Reduces mTORC1 Signaling and Growth in Lymphangioleiomyomatosis.

Mutations in the Tuberous Sclerosis Complex (TSC) genes result in the hyperactivation of the mechanistic/mammalian target of rapamycin 1 (mTORC1) growth pathway in mesenchymal pulmonary cells. Rapamycin (SirolimusTM), a naturally occurring macrolide, is the only therapeutic approved for women with lymphangioleiomyomatosis (LAM), a progressive, destructive lung disease caused by TSC gene mutations and mTORC1 hyperactivation. However, on cessation of the drug, lung function decline continues. We demonstrated here that pulmonary LAM cancer stem-like cells (SLS) most highly expressed the eukaryotic translation initiation factor 4E (eIF4E)-dependent translation initiation genes. We also showed that the eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) gene has the lowest expression in these cells, indicating that the 4E-BP1/eIF4E ratio in LAM SLS cells favors unrestrained eIF4E oncogenic mRNA translation. The bi-steric mTORC1-selective compound RMC-5552 prevented growth of LAM-associated fibroblasts (LAFs) and phosphorylation of proteins in the ribosomal protein S6K1/ribosomal protein S6 (S6K1/S6) and 4E-BP1/eIF4E translation mTORC1-driven pathways, whereas rapamycin only blocked the S6K/S6 axis. Rapamycin inhibition of LAF growth was rapidly reversed, but RMC-5552 inhibition was more durable. RMC-5552, through its potential to eradicate LAM cancer SLS cells, may have therapeutic benefit in LAM and other diseases with mTORC1 hyperactivity.

Analysis of renal lesions in Chinese tuberous sclerosis complex patients with different types of TSC gene mutations.

We sought to explore the relationship between renal lesion features and genetic mutations in tuberous sclerosis complex (TSC) patients. TSC patients with renal lesions were subjected to TSC1/2 gene next-generation sequencing (NGS). TSC1/2 mutation types and imaging examinations were screened for combined analysis of genetic and clinical features. Seventy-three probands among TSC patients with renal lesions were included. Twenty affected relatives were also included. In total, 93 patients were included. Eighty patients (86.0%) had bilateral renal angiomyolipomas (AMLs), and one had epithelioid AML. Two patients had polycystic kidney disease, one had renal cell carcinoma, and one had Wilms tumor. Among the 73 probands, four had TSC1 mutations, 53 had TSC2 mutations, and 16 had no mutations identified (NMI). There was no statistically significant difference between TSC1 mutation, TSC2 mutation and NMI group (P= 0.309), or between familial and sporadic groups (P= 0.775) when considering AML size. There was no statistically significant difference between pathogenic/likely pathogenic and benign/likely benign/NMI groups (P= 0.363) or among patients with different mutation types of TSC2 (P= 0.906). The relationship between the conditions of TSC gene mutations and the severity of renal lesions still needs more analysis. Patients with NMI, particularly those with familial disease, need more attention because the pathogenesis remains unknown.

The Correlation Between Tuberous Sclerosis Complex Genotype and Renal Angiomyolipoma Phenotype.

Tuberous sclerosis complex (TSC) is a rare multisystem autosomal dominant genetic disease that occurs between 1 in 6,000 and 1 in 10,000 live births. Additionally, renal angiomyolipoma is the most common form of renal disease in patients affected by TSC. Although a genetic mutation analysis of TSC is not rare, the correlation between the TSC gene mutation and renal angiomyolipoma phenotype is poorly understood. This study aims to analyze the mutation sites in 261 types of selected TSC patients. The results reveal that: (1) female patients develop more renal angiomyolipoma than male patients [p = 0.008, OR = 2.474, 95%CI (1.258–4.864)]; (2). The missense mutation of TSC1 led to a higher risk of renal angiomyolipoma [p < 0.01, OR = 15, 95%CI (2.859–78.691)], and in contrast, showed a reduced risk in patients with frameshift mutation [p = 0.03, OR = 0.252, 95%CI (0.07–0.912)]; (3). Patients with TSC2 mutations in the transcription activation domain 1 coding genes, had increased renal angiomyolipoma [p = 0.019, OR = 3.519, 95%CI (1.226–10.101)]. Therefore, our genotype-phenotype correlation study might shed light on the early monitoring and evaluation of renal angiomyolipoma in TSC patients.

Structural insights into TSC complex assembly and GAP activity on Rheb

Tuberous sclerosis complex (TSC) integrates upstream stimuli and regulates cell growth by controlling the activity of mTORC1. TSC complex functions as a GTPase-activating protein (GAP) towards small GTPase Rheb and inhibits Rheb-mediated activation of mTORC1. Mutations in TSC genes cause tuberous sclerosis. In this study, the near-atomic resolution structure of human TSC complex reveals an arch-shaped architecture, with a 2:2:1 stoichiometry of TSC1, TSC2, and TBC1D7. This asymmetric complex consists of two interweaved TSC1 coiled-coil and one TBC1D7 that spans over the tail-to-tail TSC2 dimer. The two TSC2 GAP domains are symmetrically cradled within the core module formed by TSC2 dimerization domain and central coiled-coil of TSC1. Structural and biochemical analyses reveal TSC2 GAP-Rheb complimentary interactions and suggest a catalytic mechanism, by which an asparagine thumb (N1643) stabilizes γ-phosphate of GTP and accelerate GTP hydrolysis of Rheb. Our study reveals mechanisms of TSC complex assembly and GAP activity.

A case report on malignant perivascular epithelioid cell neoplasm of the thigh, a rare presentation in the skin

Perivascular epithelioid cell neoplasms (PEComa) are a family of mesenchymal tumors characterized by perivascular epithelioid cells with co-expression of melanocytic and muscle markers and can occur in any part of the body. These tumors are almost always positive for HMB-45 and smooth muscle actin (SMA) immunochemistry. Perivascular epithelioid cell neoplasms tend to arise in middle age, and there is a marked female predominance. The tumors most commonly occur in the gynecologic tract, pelvis, and retroperitoneum. They are of varying malignant potential and are occasionally associated with tuberous sclerosis complex, a rare tumor driven by tuberous sclerosis complex gene mutations TSC1/2, causing up-regulation of mTOR. We present a case of malignant perivascular epithelioid cell neoplasm of the thigh, which is an exceedingly rare presentation in the skin.

The Neurodevelopmental Pathogenesis of Tuberous Sclerosis Complex (TSC).

Tuberous sclerosis complex (TSC) is a model disorder for understanding brain development because the genes that cause TSC are known, many downstream molecular pathways have been identified, and the resulting perturbations of cellular events are established. TSC, therefore, provides an intellectual framework to understand the molecular and biochemical pathways that orchestrate normal brain development. The TSC1 and TSC2 genes encode Hamartin and Tuberin which form a GTPase activating protein (GAP) complex. Inactivating mutations in TSC genes (TSC1/TSC2) cause sustained Ras homologue enriched in brain (RHEB) activation of the mammalian isoform of the target of rapamycin complex 1 (mTORC1). TOR is a protein kinase that regulates cell size in many organisms throughout nature. mTORC1 inhibits catabolic processes including autophagy and activates anabolic processes including mRNA translation. mTORC1 regulation is achieved through two main upstream mechanisms. The first mechanism is regulation by growth factor signaling. The second mechanism is regulation by amino acids. Gene mutations that cause too much or too little mTORC1 activity lead to a spectrum of neuroanatomical changes ranging from altered brain size (micro and macrocephaly) to cortical malformations to Type I neoplasias. Because somatic mutations often underlie these changes, the timing, and location of mutation results in focal brain malformations. These mutations, therefore, provide gain-of-function and loss-of-function changes that are a powerful tool to assess the events that have gone awry during development and to determine their functional physiological consequences. Knowledge about the TSC-mTORC1 pathway has allowed scientists to predict which upstream and downstream mutations should cause commensurate neuroanatomical changes. Indeed, many of these predictions have now been clinically validated. A description of clinical imaging and histochemical findings is provided in relation to laboratory models of TSC that will allow the reader to appreciate how human pathology can provide an understanding of the fundamental mechanisms of development.

MTOR pathway activation in focal cortical dysplasia

BackgroundFocal cortical dysplasia (FCD) is a localized cortical malformation and considerable morphological overlap exists between FCD IIB and neurological lesions associated with Tuberous sclerosis complex (TSC). Abnormal mTOR pathway secondary to somatic mTOR mutation and TSC gene mutation linked to PI3K/AKT/mTOR pathway have supported the hypothesis of common pathogenesis involved. Role of converging pathway, viz. Wnt/β-Catenin and mTOR is unknown in FCD. We aimed to analyse FCD IIB for TSC1/TSC2 mutations, immunoreactivity of hamartin, tuberin, mTOR and Wnt signalling cascades, and stem cell markers. Materials and methodsSixteen FCD IIB cases were retrieved along with 16 FCD IIA cases for comparison. Immunohistochemistry was performed for tuberin, hamartin, mTOR pathway markers, markers of stem cell phenotype, and Wnt pathway markers. Mutation analysis for TSC1 and TSC2 was performed by sequencing in 9 FCD cases. ResultsAll FCD cases showed preserved hamartin and tuberin immunoreactivity. Aberrant immunoreactivity of phospho-P70S6 kinase, S6 ribosomal, phospho-S6 ribosomal and Stat3 was noted in FCD IIB, with variable phospho-4E-BP1 (45%) and absent phospho-Stat3 expression. Immunoreactivity for phospho-P70S6 kinase (100%), S6 ribosomal protein (100%) and Stat3 (100%) was noted in FCD IIA, but not for phospho-S6 ribosomal, phospho-4E-BP1 and phospho-Stat3. c-Myc immunoreactivity was noted in all FCD cases. Nestin (81%) and Sox 2 (88%) stained balloon cells in FCD IIB (44%), while in FCD IIA cases were negative. All FCD cases were immunopositive for Wnt, but were negative for β-Catenin and cyclin-D1. TSC mutations were detected in two cases of FCD IIB. ConclusionAbnormal mTOR pathway activation exists in FCD IIB and IIA, however, shows differential immunoreactivity profile, indicating varying degrees of dysregulation. Labelling of neuronal stem cell markers in balloon cells suggests they are phenotypically immature. TSC1/2 mutation play role in the pathogenesis of FCD. Deep targeted sequencing is preferred diagnostic technique since conventional sanger sequencing often fails to detect low-allele frequency variants involved in mTOR/TSC pathway genes, commonly found in FCD.

Eosinophilic Renal Cell Tumors With a TSC and MTOR Gene Mutations Are Morphologically and Immunohistochemically Heterogenous

Eosinophilic renal neoplasms have a wide spectrum of histologic presentations, and several studies have demonstrated a subtype of renal cell carcinomas (RCCs) associated with the tuberous sclerosis complex (TSC)/mammalian target of rapamycin pathway. A review of our institutional archives led to the identification of 18 cases of renal eosinophilic tumors with unusual morphology. Immunohistochemical analysis demonstrated that these could be separated into 3 groups: group 1 had solid architecture and morphology similar to chromophobe RCC but was negative for CK20 and vimentin, and had weak focal staining for CK7 and P504S; group 2 had solid architecture and morphology similar to either renal oncocytoma or chromophobe RCC, eosinophilic variant and had diffuse staining of CK7 and P504S, absent to weak staining of CK20, and negative staining for vimentin; and group 3 had solid, cystic and papillary architecture and was negative for CK7, except for 1 case, along with moderate to strong staining of CK20, P504S, and vimentin. The cases were then sent for next-generation sequencing to determine whether molecular pathogenic variants were present. In group 1, all 3 cases had mutations in TSC2. In group 2, pathogenic variants were identified in 3 genes: TSC1, TSC2, and MTOR. In group 3, genetic alterations and pathogenic variants were identified in TSC1 and TSC2. Our results support TSC/MTOR-associated neoplasms as a distinct group that exhibits heterogenous morphology and immunohistochemical staining.

Analysis of genotypes, EEG and phenotypes of tuberous sclerosis complex patients

Objective: Tuberous sclerosis complex (TSC) is a multi-system disease with TSC1 and TSC2 genes as the pathogenic genes. The purpose of our study was to analyze the gene mutation in patients with TSC with epilepsy as the main clinical manifestation. The relationship between genotype and phenotype, scalp EEG in patients was analyzed. Methods: The peripheral blood was extracted from 43 patients and their families. TSC gene was detected by second-generation sequencing. Long-term video EEG monitoring and MRI examination were performed to determine the onset area, seizure type and location of nodules. Results: 39 patients had TSC gene mutation, 4 patients did not detect the gene mutation.11 had TSC1 mutations and 28 had TSC2 mutations. 22 mutations were de novo. Patients with TSC2 mutations had earlier seizure and more nodules than patients with TSC1 mutations, but no significant difference in intelligence and spasm were observed. 28 patients had focal origin of scalp EEG, of which 85.7% of TSC2 mutations patients had focal origin. Conclusions: Patients of TSC2 mutations always has an early onset age. Although MRI shows multiple nodules, the onset of EEG is mainly focal origin.

AN UNUSUAL CASE OF A SPONTANEOUS PNEUMOTHORAX

SESSION TITLE: Tuesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/22/2019 01:00 PM - 02:00 PM INTRODUCTION: Lymphangioleiomyomatosis (LAM) is a progressive, cystic lung disease that can either be sporadic or associated with Tuberous Sclerosis Complex (TSC) with many clinical, radiologic, and pathologic features identically represented between both variants. It predominantly affects young females and is characterized by proliferation of atypical smooth muscle cells, resulting in diffuse cysts throughout the pulmonary parenchyma. Due to the underlying damage, patients often present with a host of pulmonary complaints, including pneumothoraxes. CASE PRESENTATION: A 25-year-old female with a history of asthma, cerebral palsy, uncontrollable epilepsy, hydrocephalus with ventriculoperitoneal shunt and tuberous sclerosis presented to the emergency department for acute respiratory distress. The patient’s mother described the dyspnea as sudden-onset with worsening peripheral and central cyanosis. Paramedics were called and she was emergently intubated in the field. Initial chest x-ray revealed a large, left-sided pneumothorax with contralateral mediastinal shift. A chest tube was emergently placed with repeat imaging depicting lung expansion. The patient was admitted to the intensive care unit for monitoring. On day 2 of hospitalization, the patient underwent a computed tomography of the chest which depicted diffuse thin walled cysts with interlobular septal thickening, consistent with LAM. On day 7 of hospitalization she was extubated, with chest tube removed on day 10. Screening abdominal ultrasound revealed hepatic hemangiomas and renal angiomyolipomas. She was discharged in stable condition with close follow-up. DISCUSSION: LAM is a rare, multi-system disorder that is associated with mutations in TSC genes, particularly loss of function of the tuberous sclerosis protein TSC2. Furthermore, the predilection for females is supported by reports of disease exacerbation during menstruation, pregnancy and with estrogens. Common pulmonary presentations include exertional dyspnea, pleural effusions and recurrent spontaneous pneumothoraxes; however, as dyspnea is nonspecific, patients are often labeled as asthmatics. Evaluation consists of pulmonary function testing and high-resolution computed tomography (HRCT). LAM should be suspected in women presenting with spontaneous pneumothoraxes, and in those with TSC. Treatment of pulmonary LAM consists of targeting the mTOR protein with sirolimus and lung transplantation in severe disease. CONCLUSIONS: TSC associated LAM should be suspected in any female with a spontaneous pneumothorax. HRCT usually depicts diffuse cysts throughout the pulmonary parenchyma. Despite treatment with sirolimus, patients often require lung transplantation for long-term management. Reference #1: Johnson S. Lymphangioleiomyomatosis: clinical features, management and basic mechanisms. Thorax 1999;54:254-264 Reference #2: Lama A, Ferreiro L, Golpe A, et al. Characteristics of Patients with Lymphangioleiomyomatosis and Pleural Effusion: A Systematic Review. Respiration 2016; 91:256 DISCLOSURES: No relevant relationships by Sunil Chulani, source=Web Response No relevant relationships by Keith Guevarra, source=Web Response No relevant relationships by Amee Patrawalla, source=Web Response

Genotype-phenotype correlation of patients with tuberous sclerosis complex–associated renal angiomyolipoma: a descriptive study

TSC2 gene mutation was repeatedly reported to be associated with a more severe phenotype in patients with tuberous sclerosis complex (TSC). Our current study aims to further explore whether there is such a correlation in patients with TSC-associated renal angiomyolipoma (TSC-RAML). TSC1/TSC2 gene mutation was screened by high-throughput sequencing in 25 TSC-RAML patients from 2 medical centers. Clinical data were also carefully collected. Linear regression analysis and Student t-test were conducted by IBM SPSS Statistics Version 21.0 to analyze the genotypic-phenotypic relationship. The results indicated a high level of TSC gene mutation (80%; 20/25) in TSC-RAML patients, with higher frequency of TSC2 mutation (68%; 17/25) than TSC1 mutation (12%; 3/25). Seven novel mutation sites were detected in this study. In general, there were no significant correlations between tumor size and age (r = 0.134, P = .522), hemoglobin (r = 0.255, P = .219), and serum creatinine (r = 0.043, P = .839). Patients with larger tumor size have higher risk of bleeding. Specially, it was higher hemoglobin level in patients with TSC1 mutation than ones with TSC2 mutation and without TSC mutation (P < .05). However, no difference was found in either tumor size or serum creatinine by TSC mutation genes (P > .05). Furthermore, no difference was found in tumor size, hemoglobin, and serum creatinine by TSC mutation types (P > .05). In conclusion, TSC-RAML is TSC2 mutation dominant, with the individual differences varying greatly. No definite genotype-phenotype correlation exists in patients with TSC-RAML, and it needs to be further explored.

Analysis of TSC gene mutations in five patients with tuberous sclerosis complex

To identify pathogenic mutations of TSC1 and TSC2 genes in two familial and one sporadic cases with tuberous sclerosis complex (TSC). For five patients and their family members, potential mutations of the TSC1 and TSC2 genes were detected by direct sequencing. For one family, a novel missense mutation c.1964C>T (p.S655F) was detected in the exon 19 of the TSC2 gene. For the sporadic patient, a repeat substitution with deletion mutation c.5238-5255delCATCAAGCGGCTCCGCCA (p.His1746GlnfsX56) was detected in the exon 40 of the TSC2 gene, which led to a stop codon TGA after the 56th amino acids. No mutation was found in another family. The missense mutation c.1964C>T(P.S655F) and the substitution with deletion mutation 5238-5255delCATCAAGCGGCTCCGCCA(p.His1746GlnfsX56) of the TSC2 gene probably underlie the disease in the first family and the sporadic case.

Phenotypic and genotypic characterization of Chinese children diagnosed with tuberous sclerosis complex.

We investigated the clinical phenotypes and genetic mutations in Chinese children diagnosed with tuberous sclerosis complex (TSC). Sequencing of TSC1 and TSC2 genes was performed in 117 children with TSC and their parents. Association of TSC gene mutations with clinical manifestations was investigated. All gene mutations were heterozygous including in 16 patients (13.7%) with mutations in TSC1 gene and 101 patients (86.3%) with mutations in TSC2 gene. Among the 16 patients with TSC1 gene mutations, 15 different types of mutations were found, which included 5 novel mutations; all patients had skin manifestations and epilepsy. Among the 101 patients with TSC2 mutations, 85 different types of mutations were found, which included 25 novel mutations; 97 patients (96.0%) had skin manifestations; 97 (96.0%) had epilepsy; 74 (73.3%) had intellectual disability and 25 patients (24.8%) were autistic. The clinical phenotype of the 14 children with familial TSC was more severe than that of their parents.

Clinical application value of echocardiography combined with genetic testing in fetal cardiac rhabdomyoma

To investigate the clinical value of echocardiography combined with genetic testing in the fetal cardiac rhabdomyoma. Thirty-three fetal cardiac rhabdomyoma cases diagnosed by fetal echocardiogram in Beijing Anzhen Hospital from Jan. 2011 to Oct. 2015 were enrolled in a retrospective analysis. The results of other examination and pregnancy outcomes of them were followed up, the genetic characteristics of cardiac rhabdomyoma were summarized on the basis of pathology and genetics examination results. The pregnancy outcomes: 24 cases were terminated pregnancy, 4 cases were born and 5 cases were lost. The results of ultrasound, pathology and genetic examination were detailed in 8 cases. Pathological examination: the typical characteristics of cardiac rhabdomyoma were found in the 8 cases with cardiac rhabdomyoma. The tumor tissue was composed of irregular and swelling shape of cardiomyocytes, and the cytoplasm was vacuole like, which was characteristic of " spider like cells" through microscopic observation. The geneticdetection results: 7 cases had tuberous sclerosis complex (TSC) gene mutation, TSC gene abnormalities were not detected in 1 case. Among the 7 cases with TSC gene mutations, 6 cases were with TSC2 gene mutation and the other 1 case was with TSC1 gene mutation. The family gene was investigated in the 5 cases, which including 3 cases of TSC gene mutation in mother passed on to the fetus (1 case with family of three generations of genetic) and 2 cases of spontaneous TSC gene mutation in the fetus. Prenatal echocardiography combined with genetic detection have important clinical significance, which not only can clear if cardiac rhabdomyomas were associated with TSC, but also can clear the TSC gene mutation source. So as to further guide the perinatal management.

Early onset epileptic encephalopathy or genetically determined encephalopathy with early onset epilepsy? Lessons learned from TSC.

In tuberous sclerosis complex (TSC) a relationship has been shown between early and refractory seizures and intellectual disability. However, it is uncertain whether epilepsy in TSC is simply a marker in infants who are destined to develop an encephalopathic process or if seizures play a causal role in developing an encephalopathy. This paper summarizes the key points discussed during a European TSC workshop held in Rome, and reviews the experimental and clinical evidence in support of the two theories. There are many factors that influence the appearance of both early seizure onset and the encephalopathy resulting in neurodevelopmental deficits. Experimental studies show that as a consequence of the TSC genes mutation, mammalian target of Rapamycin (mTOR) overactivation determines an alteration in cellular morphology with cytomegalic neurons, altered synaptogenesis and an imbalance between excitation/inhibition, thus providing a likely neuroanatomical substrate for the early appearance of refractory seizures and for the encephalopathic process. At the clinical level, early signs of altered developmental trajectories are often unrecognized before 12 months of age. Evidence from experimental research shows that encephalopathy in TSC might have a genetic cause, and mTOR activation caused by TSC gene mutation can be directly responsible for the early appearance of seizures and encephalopathy.

Myocardial Fatty Foci in Adult Patients with Tuberous Sclerosis Complex: Association with Gene Mutation and Multiorgan Involvement

To estimate the association between myocardial fatty foci (MFF) on chest computed tomographic (CT) images and type of gene mutation or multiorgan involvement in patients with tuberous sclerosis complex (TSC). This retrospective case-control study was approved by the ethics committee, which waived the need for patient consent. Forty-eight patients with definite TSC (41 women; mean age, 35 years ± 11 [standard deviation]) and 96 age- and sex-matched patients without TSC who had undergone chest CT were evaluated. Two blinded readers independently scored MFF as low-attenuation areas within the myocardium. Patient history, gene mutation, and multiorgan involvement were obtained from clinical records. Cohen κ, Mann-Whitney U, χ(2) or Fisher exact, Kruskal-Wallis, and Spearman statistics were calculated. One or more MFF was detected in 50% (24 of 48) of patients with TSC; however, no MFF was detected in control patients (P < .001). MFFs were oval (62%, 15 of 24) or linear (38%, nine of 24) and involved the left ventricle in 13 patients and both ventricles in 24 patients (mostly the apical or midleft ventricle); median size was 127 mm(2). After four patients with TSC and unknown mutational status (two with MFF) were excluded, MFF was detected in 53% (10 of 19) of patients with TSC1 mutation, 65% (11 of 17) of patients with TSC2 mutation, and 12% (one of eight) of patients with TSC but without an identified mutation (P = .044). MFF presence was associated with brain (P = .011) and multiorgan (P = .008) involvement. The number of MFF per patient correlated with the degree of multiorgan involvement (P = .014). With MFF considered predictive of TSC, 50% (24of 48) sensitivity, 100% (96 of 96) specificity, 100% (24 of 24) positive predictive value, and 80% (96 of 120) negative predictive value were obtained. MFF was highly specific for TSC. MFF presence was associated with TSC gene mutations and with brain or multiorgan involvement; their number per patient was correlated with the degree of multiorgan involvement.

The neural crest lineage as a driver of disease heterogeneity in Tuberous Sclerosis Complex and Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease, best characterized by the formation of proliferative nodules that express smooth muscle and melanocytic antigens within the lung parenchyma, leading to progressive destruction of lung tissue and function. The pathological basis of LAM is associated with Tuberous Sclerosis Complex (TSC), a multi-system disorder marked by low-grade tumors in the brain, kidneys, heart, eyes, lung and skin, arising from inherited or spontaneous germ-line mutations in either of the TSC1 or TSC2 genes. LAM can develop either in a patient with TSC (TSC-LAM) or spontaneously (S-LAM), and it is clear that the majority of LAM lesions of both forms are characterized by an inactivating mutation in either TSC1 or TSC2, as in TSC. Despite this genetic commonality, there is considerable heterogeneity in the tumor spectrum of TSC and LAM patients, the basis for which is currently unknown. There is extensive clinical evidence to suggest that the cell of origin for LAM, as well as many of the TSC-associated tumors, is a neural crest cell, a highly migratory cell type with extensive multi-lineage potential. Here we explore the hypothesis that the types of tumors that develop and the tissues that are affected in TSC and LAM are dictated by the developmental timing of TSC gene mutations, which determines the identities of the affected cell types and the size of downstream populations that acquire a mutation. We further discuss the evidence to support a neural crest origin for LAM and TSC tumors, and propose approaches for generating humanized models of TSC and LAM that will allow cell of origin theories to be experimentally tested. Identifying the cell of origin and developing appropriate humanized models is necessary to truly understand LAM and TSC pathology and to establish effective and long-lasting therapeutic approaches for these patients.

The analysis of mutations and exon deletions at TSC2 gene in angiomyolipomas associated with tuberous sclerosis complex

Angiomyolipomas (AMLs) are relatively rare hamartomatous or benign tumors that occasionally occur as part of tuberous sclerosis complex (TSC). Mutations in either of the two genes, TSC1 and TSC2, have been attributed to the development of TSC.Between 1994 and January 2009, 83 patients were diagnosed with AML at the Samsung Medical Center. In that group of patients, 5 (6%) had AML with TSC (AML-TSC). Mutational analysis of the TSC2 gene was performed using 7 samples from the 5 AML-TSC patients and 14 samples from 14 patients with sporadic AML without TSC (AML-non-TSC). From this analysis, mutations in TSC genes were identified in 5 samples from the AML-TSC patients (mutation detection rate=71%) and 3 samples from AML-non-TSC patients (mutation detection rate=21%). In the case of AML-TSC, 6 mutations were found including 3 recurrent mutations and 3 novel mutations, while in the case of AML-non-TSC, 4 mutations were identified once, including 1 novel mutation. Also MLPA analysis of the TSC2 gene showed that TSC2 exon deletion is more frequently observed in AML-TSC patients than in AML-non-TSC patients.This is the first mutation and multiplex ligation-dependent probe amplification (MLPA) analyses of TSC2 in Korean AMLs that focus on TSC. This study provides data that are representative of the distribution of mutations and exon deletions at TSC genes in clinically diagnosed AML-TSC cases of the Korean population.

α-[ 11 C]-Methyl- l -tryptophan–PET in 191 patients with tuberous sclerosis complex

This was an observational study done on a large cohort of patients with tuberous sclerosis complex (TSC) to determine whether i) the presence of α-[(11)C]-methyl-l-tryptophan (AMT) hotspots is related to the duration of seizure intractability, ii) the presence of AMT hotspots is related to specific TSC gene mutations, and iii) there is concordance between areas with an AMT hotspot and seizure lateralization/localization on scalp EEG. One hundred ninety-one patients (mean age: 6.7 years; median: 5 years; range: 3 months to 37 years) with TSC and intractable epilepsy were included. All patients underwent AMT-PET scan. AMT uptake in each tuber and normal-appearing cortex was measured and correlated with clinical, scalp EEG, and, if available, electrocorticographic data. The longer the duration of seizure intractability, the greater the number of AMT hotspots (r = 0.2; p = 0.03). AMT hotspots were seen in both TSC1 and TSC2. There was excellent agreement in seizure focus lateralization between ictal scalp EEG and AMT-PET (Cohen κ 0.94) in 68 of 95 patients in whom both ictal video-EEG and AMT-PET showed lateralizing findings; in 28 of 68 patients (41%), AMT was more localizing. Furthermore, AMT-PET was localizing in 10 of 17 patients (58%) with nonlateralized ictal EEG. AMT-PET, when used together with video-EEG, provides additional lateralization/localization data, regardless of TSC mutation. The duration of seizure intractability may predict the multiplicity of areas with AMT hotspots.

Co-occurrence of giant cell carcinoma and adenocarcinoma of the lung accompanied by multifocal micronodular pneumocyte hyperplasia associated with tuberous sclerosis

Multifocal micronodular pneumocyte hyperplasia (MMPH) is a rare pulmonary manifestation of tuberous sclerosis complex (TSC). We report the case of a patient who developed lung giant cell carcinoma and adenocarcinoma accompanied by MMPH associated with TSC. Although she received chemotherapy postoperatively, she died of relapse of the pulmonary giant cell carcinoma 7 months after diagnosis of the lung carcinomas. This case indicates the possibility that MMPH, like atypical adenomatous hyperplasia, can occur as a preneoplastic lesion of lung adenocarcinoma and that a TSC gene mutation might be involved in the pathogenesis. In addition, co-occurrence of these two rare diseases, MMPH and giant cell carcinoma, may facilitate understanding of the pathogenesis of giant cell carcinoma, and suggests involvement of a TSC gene mutation.