Authors: Tyburczy ME, Jozwiak S, Malinowska IA, Chekaluk Y, Pugh TJ, Wu CL, Nussbaum RL, Seepo S, Dzik
               T, Kotulska K, Kwiatkowski DJ.
Hum Mol Genet. 2015 24(7):1836-42. PMID:25432535

Tuberous sclerosis complex (TSC) is a genetic disorder characterized by seizures and tumor formation in multiple organs, mainly in the brain, skin, kidney, lung and heart. Renal cell carcinoma (RCC) occurs in ∼3% of TSC patients, and typically develops at age <50. Here we describe genetic findings in two TSC patients with multiple renal tumors, each of whom had the germline mutation TSC2 p.R905Q. The first (female) TSC patient had a left followed by a right nephrectomy at ages 24 and 27. Both kidneys showed multifocal TSC-associated papillary RCC (PRCC). Targeted, next-generation sequencing (NGS) analysis of TSC2 in five tumors (four from the left kidney, one from the right) showed loss of heterozygosity in one tumor, and four different TSC2 point mutations (p.E1351*, p.R1032*, p.R1713H, c.4178_4179delCT) in the other four samples. Only one of the 11 other tumors available from this patient had one of the TSC2 second hit mutations identified. Whole-exome analysis of the five tumors identified a very small number of additional mutated genes, with an average of 3.4 nonsilent coding, somatic mutations per tumor, none of which were seen in >1 tumor. The second (male) TSC patient had bilateral partial nephrectomies (both at age 36), with similar findings of multifocal PRCC. NGS analysis of TSC2 in two of these tumors identified a second hit mutation c.2355+1G>T in one sample that was not seen in other tumors. In conclusion, we report the first detailed genetic analysis of RCCs in TSC patients. Molecular studies indicate that tumors developed independently due to various second hit events, suggesting that these patients experienced a 'shower' of second hit mutations in TSC2 during kidney development leading to this severe phenotype.

Authors: Yang P, Cornejo KM, Sadow PM, Cheng L, Wang M, Xiao Y, Jiang Z, Oliva E, Jozwiak S, Nussbaum
               RL, Feldman AS, Paul E, Thiele EA, Yu JJ, Henske EP, Kwiatkowski DJ, Young RH, Wu CL.
Am J Surg Pathol. 2014 38:895-909. PMCID:PMC4139167

Renal cell carcinoma (RCC) occurs in 2% to 4% of patients with tuberous sclerosis complex (TSC). Previous reports have noted a variety of histologic appearances in these cancers, but the full spectrum of morphologic and molecular features has not been fully elucidated. We encountered 46 renal epithelial neoplasms from 19 TSC patients and analyzed their clinical, pathologic, and molecular features, enabling separation of these 46 tumors into 3 groups. The largest subset of tumors (n=24) had a distinct morphologic, immunologic, and molecular profile, including prominent papillary architecture and uniformly deficient succinate dehydrogenase subunit B (SDHB) expression prompting the novel term "TSC-associated papillary RCC (PRCC)." The second group (n=15) were morphologically similar to a hybrid oncocytic/chromophobe tumor (HOCT), whereas the last 7 renal epithelial neoplasms of group 3 remained unclassifiable. The TSC-associated PRCCs had prominent papillary architecture lined by clear cells with delicate eosinophilic cytoplasmic thread-like strands that occasionally appeared more prominent and aggregated to form eosinophilic globules. All 24 (100%) of these tumors were International Society of Urological Pathology (ISUP) nucleolar grade 2 or 3 with mostly basally located nuclei. Tumor cells from 17 of 24 TSC-associated PRCCs showed strong, diffuse labeling for carbonic anhydrase IX (100%), CK7 (94%), vimentin (88%), and CD10 (83%) and were uniformly negative for SDHB, TFE3, and AMACR. Gains of chromosomes 7 and 17 were found in 2 tumors, whereas chromosome 3p deletion and TFE3 translocations were not detected. In this study, we reported a sizable cohort of renal tumors seen in TSC and were able to identify them as different morphotypes, which may help to expand the morphologic spectrum of TSC-associated RCC.


Authors: Tyburczy ME, Wang JA, Li S, Thangapazham R, Chekaluk Y, Moss J, Kwiatkowski DJ, Darling TN.
Hum Mol Genet. 2014 23:2023-9. PMCID:PMC3959815 


Tuberous sclerosis complex (TSC) is characterized by the formation of tumors in multiple organs and is caused by germline mutation in one of two tumor suppressor genes, TSC1 and TSC2. As for other tumor suppressor gene syndromes, the mechanism of somatic second-hit events in TSC tumors is unknown. We grew fibroblast-like cells from 29 TSC skin tumors from 22 TSC subjects and identified germline and second-hit mutations in TSC1/TSC2 using next-generation sequencing. Eighteen of 22 (82%) subjects had a mutation identified, and 8 of the 18 (44%) subjects were mosaic with mutant allele frequencies of 0 to 19% in normal tissue DNA. Multiple tumors were available from four patients, and in each case, second-hit mutations in TSC2 were distinct indicating they arose independently. Most remarkably, 7 (50%) of the 14 somatic point mutations were CC>TT ultraviolet 'signature' mutations, never seen as a TSC germline mutation. These occurred exclusively in facial angiofibroma tumors from sun-exposed sites. These results implicate UV-induced DNA damage as a cause of second-hit mutations and development of TSC facial angiofibromas and suggest that measures to limit UV exposure in TSC children and adults should reduce the frequency and severity of these lesions.

Authors: Liesbeth De Waele, Lieven Lagae, Djalila Mekahli

Pediatr Nephrol; DOI 10.1007/s00467-014-3027-9


Renal lesions represent the second most significant cause of morbidity and mortality in patients with tuberous sclerosis complex (TSC). Recent advances in the understanding of the pathophysiology of TSC have led to the exploration of new potential therapeutic targets. Clinical trials with mammalian
target of rapamycin (mTOR) inhibitors have demonstrated promising results for several indications, such as renal angiomyolipoma, subependymal giant cell astrocytoma, lymphangioleiomyomatosis and facial angiofibromas. Currently, there is a scarcity of natural history data and randomized, placebo-controlled clinical trials on TSC. Recently, however, recommendations for the diagnostic criteria, surveillance,
and management of TSC patients have been updated. This review focuses on these novel recommendations and highlights the need for multidisciplinary follow-up of this multi-systemic disease.


Authors: Eleonora Aronica, Peter B. Crino

Neurotherapeutics. 2014 Apr;11(2):251-68. doi: 10.1007/s13311-013-0251-0.


Structural abnormalities of the brain are increasing-ly recognized in patients with neurodevelopmental delay andintractable focal epilepsies. The access to clinically well-characterized neurosurgical material has provided a uniqueopportunity to better define the neuropathological, neuro-chemical, and molecular features of epilepsy-associated focaldevelopmental lesions. These studies help to further under-stand the epileptogenic mechanisms of these lesions.Neuropathological evaluation of surgical specimens from pa-tients with epilepsy-associated developmental lesions revealstwo major pathologies: focal cortical dysplasia and low-gradedevelopmental tumors (glioneuronal tumors). In the last fewyears there have been major advances in the recognition of awide spectrum of developmental lesions associated with aintractable epilepsy, including cortical tubers in patients withtuberous sclerosis complex and hemimegalencephaly. As anincreasing number of entities are identified, the developmentof a unified and comprehensive classification represents agreat challenge and requires continuous updates. The presentarticle reviews current knowledge of molecular pathogenesisand the pathophysiological mechanisms of epileptogenesis inthis group of developmental disorders. Both emerging neuro-pathological and basic science evidence will be analyzed,highlighting the involvement of different, but often converg-ing, pathogenetic and epileptogenic mechanisms, which maycreate the basis for new therapeutic strategies in thesedisorders.