Pediatric Malignant Rhabdoid Tumors Research Articles

Imaging-Guided Metabolic Radiosensitization of Pediatric Rhabdoid Tumors.

Tumor hypoxia leads to increased resistance to radiation therapy (RT), resulting in markedly worse clinical outcomes in the treatment and management of pediatric malignant rhabdoid tumors (MRT). To alleviate hypoxia in MRT, we repurposed an FDA approved, mitochondrial oxidative phosphorylation (OXPHOS) inhibitor, Atovaquone (AVO), to inhibit oxygen consumption and thereby enhance the sensitivity of tumor cells to low dose RT in MRT by hypoxia alleviation. Additionally, to better understand the tumor response induced by AVO and optimize the combination with RT, we employed an emerging, noninvasive imaging modality, known as multispectral optoacoustic tomography (MSOT), to monitor and evaluate real-time dynamic changes in tumor hypoxia and vascular perfusion. Oxygen-Enhanced (OE)-MSOT could measure the change of tumor oxygenation in the MRT xenograft models after AVO and RT treatments, indicating its potential as a response biomarker. OE-MSOT showed that treating MRT mouse models with AVO resulted in a transient increase in oxygen saturation (ΔsO 2 ) in tumors when the mice were subjected to oxygen challenge, while RT or saline treated groups produced no change. In AVO+RT combination groups, the tumors showed an increase in ΔsO 2 after AVO administration followed by a significant decrease after RT, that correlated with a strong anti-tumor response, demarcated by complete regression of tumors, with no relapse on long-term monitoring. These observations were histologically validated. In MRT models of acquired AVO resistance, combination therapy failed to alleviate tumoral hypoxia and elicit any therapeutic benefit. Together, our data highlights the utility of repurposing anti-malarial AVO as an anticancer adjuvant for enabling low dose RT for pediatric patients.

Abstract C096: Targeting the p53 pathway to treat pediatric Malignant Rhabdoid and Atypical Teratoid Rhabdoid Tumors

Abstract Background: Pediatric rhabdoid tumors, namely Malignant Rhabdoid Tumors (MRTs) and Atypical Teratoid Rhabdoid Tumors (ATRTs) in the central nervous system (CNS), are aggressive pediatric malignancies characterized by the loss of functional INI1 protein due to SMARCB1 gene mutations. Current treatment options for these tumors are limited and ineffective, necessitating the exploration of novel therapeutic strategies. Rhabdoid cells retain an intact p53 pathway, a critical tumor suppressor pathway involved in regulating cell cycle and apoptosis. Previous studies have shown that the MDM2 inhibitor, Idasanutlin, effectively eliminates flanked rhabdoid tumors, suggesting that targeting the p53 pathway holds promise for developing effective therapies against MRTs and ATRTs. Methods: In this study, we employed a combination approach using the MDM2 inhibitor, Idasanutlin, and the XPO1 inhibitor, Selinexor, to activate the p53 pathway. The impact of this combination treatment on tumor cell viability, proliferation, and apoptosis was assessed both in vitro and in vivo using MRT and ATRT models. Additionally, CRISPR screening and proteomic studies were conducted to identify specific dependencies in refractory models and investigate their influence on treatment response. Results: Treatment with the combination of Idasanutlin and Selinexor activated the p53 signaling pathway, leading to increased levels of MDM2 and p21 proteins, two direct targets of p53, and resulting in apoptosis in MRT and ATRT models. In vitro experiments demonstrated a significant reduction in cell viability and proliferation upon treatment. In vivo studies using MRT and ATRT xenograft models showed a remarkable decrease in tumor growth following the combination treatment. However, variable responses were observed among different models, indicating the presence of dependency patterns influencing treatment sensitivity. Proteomic studies and genetic manipulation provided further insights into the potential dependencies Conclusions: Our findings highlight the potential of the combination of Idasanutlin and Selinexor to activate the p53 pathway and induce apoptosis in MRT and ATRT models. Although the treatment strategy effectively activated p53, we identified dependencies that may contribute to incomplete treatment sensitivity. Further investigation into these dependency patterns is necessary to optimize the therapeutic approach. Overall, targeting the p53 pathway using combination therapies shows promise for the development of effective treatments for pediatric MRTs and ATRTs, warranting further preclinical and clinical investigations. Citation Format: Alaa Refaat, Hyekyung Cho, Jennifer Stripay, Charles Roberts, Christopher Tinkle, Anang Shelat, Martine Roussel. Targeting the p53 pathway to treat pediatric Malignant Rhabdoid and Atypical Teratoid Rhabdoid Tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C096.

Multidisciplinary management of pediatric malignant rhabdoid tumor based on 5 years of experience at a tertiary care center

Malignant rhabdoid tumor (MRT) is a highly aggressive tumor that occurs mostly in young children with extremely poor prognosis. Standardized and effective treatment strategies for MRT have yet to be established because of its rarity. Here, we report our single-institutional experience involving MRT treatment. Patients with newly diagnosed MRT between March 2016 and October 2021 were included. The clinical characteristic, treatment-related toxicities, clinical outcomes, and prognostic factor were retrospectively analyzed. A total of 18 patients with MRT were enrolled during the 5years. The median age was 42.8months (range 10 to 82years). Among the 18 patients, 9 patients died after a median of follow-up 26months (range 3 to 42months). The 1-year event-free survival (EFS) and 3-year overall survival (OS) rates of the entire cohort were 63% (95% CI 46% to 74%) and 67% (95% CI 49% to 82%), respectively. Univariate analysis of patients who underwent gross or total resection followed by adjuvant chemotherapy and radiotherapy demonstrated an improvement in 1-year EFS. However, only gross resection and total resection predicted a better 3-year OS. Surgical excision is still the mainstream treatment for MRT. Postoperative adjuvant treatments including chemotherapy and radiotherapy contribute to improved disease control rate. Our single-institute experience may provide insights into the multimodal treatment of MRT.

Clinical and prognostic analysis of 42 children with malignant rhabdoid tumor of the kidney: a 7-year retrospective multi-center study

ObjectiveTo discuss the clinical and prognostic indicators of pediatric malignant rhabdoid tumor of the kidney (MRTK), and to increase the understanding of the occurrence and development of MRTK.MethodsFrom July 2014 to September 2021, all cases were confirmed by postoperative pathological examination. Among the 42 patients, there were 25 males and 17 females, with a median age of 10 (1–84) months. Abdominal mass or hematuria were the main clinical manifestations. Preoperative chemotherapy was performed in 9 cases (VC). The tumor stages were stage I-IV. Preoperative metastasis was found in 9 cases; the most common site was the lung. Postoperative patients received conventional chemotherapy, including VDACE regimen and UH-1 regimen. Among the 42 children in this group, survival at follow-up in this study was 26.2%(11/42).ResultsPreoperative anemia was found by univariate analysis, hypertension and hypercalcemia had shorter survival time. In addition, tumor-related factors had a significant impact on survival, with incomplete tumor resection, lymph node metastasis, stage III-IV had a lower survival rate. The impact of postoperative factors on survival included postoperative complications had a lower survival rate. The children were younger than 12 months, preoperative metastasis, no chemotherapy was performed after surgery was an independent risk factor for the prognosis of MRTK.ConclusionThe main clinical manifestations about MRTK were abdominal mass and hematuria. Preoperative chemotherapy did not significantly improve the prognosis. Postoperative chemotherapy can significantly improve the survival rate. Diagnosis depends on clinical manifestations, imaging, histopathology, immunohistochemistry and other comprehensive judgment. Age less than 12 months, preoperative metastasis, and no postoperative chemotherapy were independent risk factors for prognosis.

Molecular Heterogeneity in Pediatric Malignant Rhabdoid Tumors in Patients With Multi-Organ Involvement

Rhabdoid tumors (RTs) of the brain (atypical teratoid/rhabdoid tumor; AT/RT) and extracranial sites (most often the kidney; RTK) are malignant tumors predominantly occurring in children, frequently those with SMARCB1 germline alterations. Here we present data from seven RTs from three pediatric patients who all had multi-organ involvement. The tumors were analyzed using a multimodal molecular approach, which included exome sequencing of tumor and germline comparator and RNA sequencing and DNA array-based methylation profiling of tumors. SMARCB1 germline alterations were identified in all patients and in all tumors. We observed a second hit in SMARCB1 via chr22 loss of heterozygosity. By methylation profiling, all tumors were classified as rhabdoid tumors with a corresponding subclassification within the MYC, TYR, or SHH AT/RT subgroups. Using RNA-seq gene expression clustering, we recapitulated the classification of known AT/RT subgroups. Synchronous brain and kidney tumors from the same patient showed different patterns of either copy number variants, single-nucleotide variants, and/or genome-wide DNA methylation, suggestive of non-clonal origin. Furthermore, we demonstrated that a lung and abdominal metastasis from two patients shared overlapping molecular features with the patient’s primary kidney tumor, indicating the likely origin of the metastasis. In addition to the SMARCB1 events, we identified other whole-chromosome events and single-nucleotide variants in tumors, but none were found to be prognostic, diagnostic, or offer therapeutic potential for rhabdoid tumors. While our findings are of biological interest, there may also be clinical value in comprehensive molecular profiling in patients with multiple rhabdoid tumors, particularly given the potential prognostic and therapeutic implications for different rhabdoid tumor subgroups demonstrated in recent clinical trials and other large cohort studies.

SMARCB1(INI1)-deficient renal cell carcinoma: medullary and beyond : Evolving concepts

During the last decades, the SWI/SNF chromatin-remodeling complex has received enormous recognition as amajor player in the molecular pathogenesis of diverse neoplasms. Accordingly, SWI/SNF defects affecting different subunits of the complex became defining genetic features in the nosology of different neoplastic entities. In the kidney, loss of SMARCB1(INI1) as amajor component of the SWI/SNF complex has emerged as the defining genetic marker for renal medullary carcinoma and pediatric malignant rhabdoid tumor. Diagnosis of these two rare entities is based on aset of defined demographic, clinicopathological, immunophenotypic, and genetic (SMARCB1 loss) criteria. Moreover, the sickle cell trait is considered aprerequisite for renal medullary carcinoma. Current knowledge illustrates that SMARCB1 loss is encountered in three major tumor categories in the kidney: (1)histologically defined neoplasms that are primarily driven by de novo SMARCB1 loss (renal medullary carcinoma and malignant rhabdoid tumor); (2)SMRACB1-deficient renal cell carcinoma (RCC) with variable non-specific histology ranging from collecting duct-like, papillary high-grade (papillary type2), or medullary-like (lacking sickle cell trait), to fully undifferentiated; and (3)biphasic (dedifferentiated) RCC showing a variable SMARCB1-deficient undifferentiated component. The latter variant most frequently originates from pre-existing clear cell RCC but may rarely superimpose on papillary or chromophobe RCC. This review summarizes the major defining features of the emerging SMARCB1-deficient renal neoplasms. All SMARCB1-deficient carcinomas have apoor prognosis in common. Therefore, exact diagnosis of these tumors is aprerequisite for studies investigating new therapies.

Characteristics and Outcomes in Pediatric Non-Central Nervous System Malignant Rhabdoid Tumors: A Report from the National Cancer Database

Pediatric non-central nervous system (CNS) malignant rhabdoid tumors (MRTs) are rare and aggressive malignancies without standard treatment strategies. The National Cancer Database (NCDB) was utilized to describe the incidence, characteristics, treatment strategies, and outcomes in pediatric patients. Patients <18 years of age and diagnosed with non-CNS MRTs were analyzed from the NCDB from 2004 to 2014. Log-rank tests compared differences in Kaplan-Meier survival distributions. Univariate and multivariable Cox proportional hazard regression models identified predictors of mortality. Overall, 202 patients were identified. Soft tissue tumors were most common and metastatic disease was present at diagnosis in 34.2% of patients. The 1- and 5-year overall survival (OS) rates were 48.8% and 35.9%, respectively. Multivariable analysis revealed that age <1 year and the presence of metastasis were negative prognostic indicators (p=0.058). The 1- and 5-year OS rates were 59.9% and 46.5%, respectively, for patients who received surgical intervention (n=143) compared with 12.3% and 7.4%, respectively, for those treated nonoperatively (n=59; p<0.01). Surgical resection was associated with improved outcomes on univariate analysis, although it was no longer an independent predictor of survival on multivariate analysis (p=0.18). In the cohort of surgical patients, the presence of residual disease trended towards clinically significant worse outcomes (p=0.13). Patients with non-CNS MRTs who were diagnosed in infancy and had metastatic disease had worse survival outcomes. Although surgical resection was associated with improved survival in non-CNS MRTs, it was not independently associated with survival on multivariate analysis. Efforts to improve survival may instead depend on improving chemotherapeutic strategies and developing targeted therapies.

SWI/SNF deficient central nervous system neoplasms

The SWItch/Sucrose Non-Fermentable (SWI/SNF) complexes are ubiquitous ATP dependent chromatin remodeling complexes that provide epigenetic regulation of gene expressions across the genome. Different combination of SWI/SNF subunits allow tissue specific regulation of critical cellular processes. The identification of SMARCB1 inactivation in pediatric malignant rhabdoid tumors provided the first example that the SWI/SNF complex may act as a tumor suppressor. It is now estimated at least 20% of all human tumors contain mutations in the subunits of the SWI/SNF complex. This review summarizes the central nervous system tumors with alterations in the SWI/SNF complex genes. Atypical teratoid/rabdoid tumor (AT/RT) is a highly aggressive embryonal tumor genetically characterized by bi-allelic inactivation of SMARCB1, and immunohistochemically shows complete absence of nuclear expression of its protein product INI1. A small subset of AT/RT show retained INI1 expression but defects in another SWI/SNF complex gene SMARCA4. Embryonal tumors with medulloblastoma, pineoblastoma, or primitive neuroectodermal morphology but loss of INI1 expression are now classified as AT/RT. Cribriform neuroepithelial tumor (CRINET) is an intra or para-ventricular tumor that has similar SMARCB1 alterations as AT/RT but generally has a benign clinical course. Besides AT/RT and CRINET, compete loss of nuclear INI1 expression has also been reported in poorly differentiated chordoma and intracranial myxoid sarcoma within the central nervous system. Families with non-truncating SMARCB1 mutations are prone to develop schwannomatosis and a range of developmental syndromes. The schwannomas in these patients usually demonstrate a mosaic INI1 staining pattern suggestive of partial residual protein function. Finally, clear cell meningioma is a WHO grade II variant meningioma characterized by bi-allelic inactivation of the SMARCE1 gene and immunohistochemically show loss of its protein product BAF57 expression in tumor cell nuclei.

In vivo evaluation of the EZH2 inhibitor (EPZ011989) alone or in combination with standard of care cytotoxic agents against pediatric malignant rhabdoid tumor preclinical models-A report from the Pediatric Preclinical Testing Consortium.

The Pediatric Preclinical Testing Program (PPTP) previously reported the activity of the EZH2 inhibitor tazemetostat (EPZ6438) against xenograft models of rhabdoid tumors. Here, we determined whether an inhibitor of EZH2 enhanced the effect of standard of care chemotherapeutic agents: irinotecan, vincristine, and cyclophosphamide. EPZ011989 significantly prolonged time to event in all the six rhabdoid models studied but did not induce tumor regression. The addition of EPZ011989 to standard of care agents significantly improved time to event in at least one model for each of the agents studied, although this effect was observed in only a minority of the combination testing experiments.

Atypical Teratoid/Rhabdoid Tumor of the Sellar Region: A Case Report and Review of the Literature

Atypical teratoid/rhabdoid tumors (AT/RTs) are rare and aggressive pediatric malignant rhabdoid tumors (MRTs) that occur within the brain. The majority of these tumors occur in the cerebellum. Only 45 cases of adults with AT/RTs have been reported in the literature to date. We present a case of sellar and suprasellar AT/RT in a 40-year-old female patient with this rare entity. To our knowledge, this is the 14th case of an adult-onset AT/RT in the sellar and suprasellar region. J Neurol Res. 2020;10(1):13-16 doi: https://doi.org/10.14740/jnr556

Atypical Teratoid/Rhabdoid Tumor of the Sellar Region: A Case Report and Review of the Literature

Atypical teratoid/rhabdoid tumors (AT/RTs) are rare and aggressive pediatric malignant rhabdoid tumors (MRTs) that occur within the brain. The majority of these tumors occur in the cerebellum. Only 45 cases of adults with AT/RTs have been reported in the literature to date. We present a case of sellar and suprasellar AT/RT in a 40-year-old female patient with this rare entity. To our knowledge, this is the 14th case of an adult-onset AT/RT in the sellar and suprasellar region. J Neurol Res. 2020;10(1):13-16 doi: https://doi.org/10.14740/jnr556

Isolated Pure Malignant Rhabdoid Tumor (MRT) of the Bladder: Case Report and Lessons Learned

Pediatric extrarenal malignant rhabdoid tumors (MRTs) are rare, aggressive tumors with a poor prognosis (20% 5-year survival). There are currently fewer than 10 published case reports of primary MRT of the bladder. We report the case of an 18-month-old female with an isolated MRT of the bladder which was initially misdiagnosed as an inflammatory myofibroblastic tumor on biopsy. We review the history, tumor biology, histology, and current management of extrarenal MRT, along with lessons learned from the difficulty with the patient's initial diagnosis.

BRD9 defines a SWI/SNF sub-complex and constitutes a specific vulnerability in malignant rhabdoid tumors

Bromodomain-containing protein 9 (BRD9) is a recently identified subunit of SWI/SNF(BAF) chromatin remodeling complexes, yet its function is poorly understood. Here, using a genome-wide CRISPR-Cas9 screen, we show that BRD9 is a specific vulnerability in pediatric malignant rhabdoid tumors (RTs), which are driven by inactivation of the SMARCB1 subunit of SWI/SNF. We find that BRD9 exists in a unique SWI/SNF sub-complex that lacks SMARCB1, which has been considered a core subunit. While SMARCB1-containing SWI/SNF complexes are bound preferentially at enhancers, we show that BRD9-containing complexes exist at both promoters and enhancers. Mechanistically, we show that SMARCB1 loss causes increased BRD9 incorporation into SWI/SNF thus providing insight into BRD9 vulnerability in RTs. Underlying the dependency, while its bromodomain is dispensable, the DUF3512 domain of BRD9 is essential for SWI/SNF integrity in the absence of SMARCB1. Collectively, our results reveal a BRD9-containing SWI/SNF subcomplex is required for the survival of SMARCB1-mutant RTs.

An Antenatally Detected Pure Malignant Rhabdoid Tumor of the Bladder

Pediatric malignant rhabdoid tumors are a rare entity with poor prognosis. The extrarenal variants of this disease are sparsely presented within the literature. Our case represents, to our knowledge, the first antenatally detected bladder-variant. At 19 months of age, this patient has benefited from early detection and intervention and remains disease free following partial cystectomy and chemotherapy.

Abstract B40: Perturbation of proteostasis is lethal in SMARCB1-deficient tumors

Abstract Alterations in the SWI/SNF chromatin remodeling complex have been implicated in human malignancies. Biallelic inactivation of the core subunits SMARCB1 and SMARCA4 are associated with particularly aggressive forms of pediatric cancer known as malignant rhabdoid tumors (MRTs) and atypical theratoid/rhabdoid tumors (AT/RTs). MRTs and AT/RTs are characterized by simple genomes and lack of somatic events, suggesting that dysregulation of SWI/SNF machinery is sufficient to induce a highly malignant state. However, the lack of a conditional genetic model of MRT has precluded the investigation of the molecular bases and dependencies associated with SMARCB1 loss. To this aim, we have developed a novel embryonic mosaic mouse model of MRTs of the liver. Using this mouse model, we performed a systematic functional investigation of vulnerabilities in the context of SMARCB1 loss in order to identify novel treatments for these diseases. Embryonic mosaic models of MRTs of the liver were generated by transuterine delivery of adenoviral vectors carrying the Cre recombinase under a tissue-specific promoter (Adx-Alb-Cre) to target SMARCB1LoxP/LoxP embryos at embryonic day E12-14 in order to study the effect of SMARCB1 ablation on development and tumorigenesis. Such an approach allowed us to target the developing liver epithelial compartment and to bypass the perinatal lethality observed with tissue-specific Cre deleter strains. This approach results in postnatal expansion of the epithelial compartment and in the emergence of rhabdoid tumors in a subset of cases. Upon investigation of the early effects of SMARCB1 ablation during mouse development and tumorigenesis, we found that livers in these embryonic mosaic murine models undergo profound metabolic changes resulting in a dramatic activation of cellular programs involved in the maintenance of proteostasis in response to ER stress and autophagy. To functionally validate the hypothesis that SMARCB1 loss confers sensitivity to proteotoxic agents, embryonic mosaic murine models of MRTs of the liver were treated with combinations of bortezomib and chloroquine, resulting in suppression of tumor growth and prolonged survival. Murine transplantation models of MRT treated with combinations of bortezomib and chloroquine also resulted in a significant increase in survival. Additionally, immunohistochemical studies of pediatric MRTs showed significant accumulation of markers of ER stress, and autophagy in comparison to normal tissue. The use of a novel embryonic mosaic models of MRT demonstrated that SMARCB1 disruption during liver embryogenesis caused activation of anabolic pathways and an increase in UPR, ER stress response, and autophagy. Overall, our preclinical study provides the rationale for a novel therapeutic approach aimed at exploiting a “collateral proteopathy” characteristic of SMARCB1-deficient malignancies and at the repositioning of existing drugs that have already shown acceptable toxicity profiles. Citation Format: Melinda Soeung, Alessandro Carugo, Frederick Scott Robinson, Rosalba Minelli, Federica Carbone, Anirban Maitra, Andrea Viale, Charles W.M. Roberts, Nizar Tannir, Giulio F. Draetta, Giannicola Genovese. Perturbation of proteostasis is lethal in SMARCB1-deficient tumors [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr B40.

Olaratumab Exerts Antitumor Activity in Preclinical Models of Pediatric Bone and Soft Tissue Tumors through Inhibition of Platelet-Derived Growth Factor Receptor α.

Purpose: Platelet-derived growth factor receptor α (PDGFRα) is implicated in several adult and pediatric malignancies, where activated signaling in tumor cells and/or cells within the microenvironment drive tumorigenesis and disease progression. Olaratumab (LY3012207/IMC-3G3) is a human mAb that exclusively binds to PDGFRα and recently received accelerated FDA approval and conditional EMA approval for treatment of advanced adult sarcoma patients in combination with doxorubicin. In this study, we investigated olaratumab in preclinical models of pediatric bone and soft tissue tumors.Experimental Design: PDGFRα expression was evaluated by qPCR and Western blot analysis. Olaratumab was investigated in in vitro cell proliferation and invasion assays using pediatric osteosarcoma and rhabdoid tumor cell lines. In vivo activity of olaratumab was assessed in preclinical mouse models of pediatric osteosarcoma and malignant rhabdoid tumor.Results:In vitro olaratumab treatment of osteosarcoma and rhabdoid tumor cell lines reduced proliferation and inhibited invasion driven by individual platelet-derived growth factors (PDGFs) or serum. Furthermore, olaratumab delayed primary tumor growth in mouse models of pediatric osteosarcoma and malignant rhabdoid tumor, and this activity was enhanced by combination with either doxorubicin or cisplatin.Conclusions: Overall, these data indicate that olaratumab, alone and in combination with standard of care, blocks the growth of some preclinical PDGFRα-expressing pediatric bone and soft tissue tumor models. Clin Cancer Res; 24(4); 847-57. ©2017 AACR.

Hereditary SWI/SNF complex deficiency syndromes.

The SWItch Sucrose non-fermentable (SWI/SNF) complex is a highly conserved multi-subunit complex of proteins encoded by numerous genes mapped to different chromosomal regions. The complex regulates the process of chromatin remodelling and hence plays a central role in the epigenetic regulation of gene expression, cell proliferation and differentiation. During the last three decades, the SWI/SNF complex has been increasingly recognized as a central molecular event driving the initiation and/or progression of several benign and malignant neoplasms of different anatomic origin and having diverse histomorphological appearance. Atypical teratoid/rhabdoid tumors (AT/RT) and renal/extrarenal malignant rhabdoid tumors of childhood, epithelioid sarcoma and small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) represent the most commonly recognized SWI/SNF-driven neoplasms. Approximately one-third of pediatric malignant rhabdoid tumors are linked to germline SWI/SNF alterations (SMARCB1/INI1, rarely SMARCA4) resulting in occasional familial clustering of these highly aggressive malignancies (so-called rhabdoid tumor predisposition syndrome, RTPS, types 1 and 2, respectively). However, more recently, inherited SWI/SNF-deficiency has been linked to several benign syndromic tumors including a subset of familial schwannomatosis (linked to SMARCB1) and multiple meningiomas (linked to SMARCE1) as well as others. Beyond neoplasms, several congenital developmental functional disorders such as Coffin-Siris syndrome and intellectual disability are now known to be SWI/SNF-related. The latter are essentially not associated with SWI/SNF-driven neoplasms, although at least anecdotal cases have documented concurrence of both neoplastic and developmental disorders. This review summarizes the most important SWI/SNF-driven diseases with a main focus on neoplasms.

Abstract A29: Balanced translocations disrupting SMARCB1 are hallmark recurrent genetic alterations in renal medullary carcinomas

Abstract Renal medullary carcinoma (RMC) is a rare and highly aggressive neoplasm that most often occurs in young patients or children with sickle cell trait or disease (SCD). Although BAF47 staining is constantly negative in these tumors, the genetic mechanism underlying this phenotype remains unknown, since all cases reported so far show SMARCB1 hemizygous deletion only. By investigating a series of five RMC by gene expression profiling, array-CGH, and RNA and whole-exome sequencing, we demonstrated that SMARCB1 inactivation is related to an original mechanism of inter-chromosomal balanced translocations that disrupt SMARCB1 sequence and thus contribute to its inactivation. RMC were also characterised by a simple genome, with a low mutation rate and a lack of recurrent molecular alterations other than SMARCB1 deficiency, emphasizing its potency as single genetic event to drive oncogenesis. Finally, gene expression profiling revealed that RMC share common oncogenic pathways with pediatric malignant rhabdoid tumors, another lethal tumor subtype characterised by SMARCB1 deficiency Citation Format: Julien Calderaro, Julien Masliah-Planchon, Wilfrid Richer, Laetitia Planque, Pascale Maille, Alexandre de la Taille, Helene Boussion, Olivier Delattre, Yves Allory, Franck Bourdeaut. Balanced translocations disrupting SMARCB1 are hallmark recurrent genetic alterations in renal medullary carcinomas. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr A29.

Balanced Translocations Disrupting SMARCB1 Are Hallmark Recurrent Genetic Alterations in Renal Medullary Carcinomas

BackgroundRenal medullary carcinoma (RMC) is a rare and highly aggressive neoplasm that most often occurs in the setting of sickle cell trait or sickle cell disease (SCD). Most patients present with metastatic disease resistant to conventional chemotherapy, and therefore there is an urgent need for molecular insight to propose new therapies. ObjectiveTo determine the molecular alterations and oncogenic pathways that drive RMC development. Design, setting, and participantsA series of five frozen samples of patients with RMC was investigated by means of gene expression profiling, array comparative genomic hybridization, and RNA and whole exome sequencing (WES). Outcome measurements and statistical analysisRNA and DNA sequencing read data were analyzed to detect gene fusions and somatic mutations. Gene fusions mutations were validated by real-time polymerase chain reaction and fluorescence in situ hybridization. Gene expression profiling was analyzed by unsupervised hierarchical clustering and Gene Set Enrichment Analysis (Broad Institute, Cambridge, MA, USA). Results and limitationsWe observed inactivation of the tumor suppressor gene SMARCB1 in all tumors. In all four cases developed in patients with SCD, we identified an original mechanism of interchromosomal balanced translocations that disrupt the SMARCB1 sequence and thus contribute to its inactivation. Gene expression profiling revealed that RMC shares common oncogenic pathways with pediatric malignant rhabdoid tumors, another tumor subtype characterized by SMARCB1 deficiency. ConclusionsRMCs are characterized by an original mechanism of interchromosomal balanced translocations that disrupt the SMARCB1 sequence. WES reveals that RMCs show no other recurrent genetic alteration and an overall stable genome, underscoring the oncogenic potency of SMARCB1 inactivation. Patient summaryOur comprehensive molecular study supports a pivotal role of the tumor suppressor gene SMARCB1 in the development of renal medullary carcinoma. The use of therapeutic strategies based on the biologic effects of its inactivation should now open new perspectives for this typically lethal malignancy.

SMARCB1-deficient Vulvar Neoplasms: A Clinicopathologic, Immunohistochemical, and Molecular Genetic Study of 14 Cases.

Loss of expression of the SMARCB1 (INI1/BAF47/SNF5) tumor-suppressor protein, originally identified in pediatric malignant rhabdoid tumors, has been noted in significant percentages of epithelioid sarcomas of classical and proximal-type and in myoepithelial carcinomas. Epithelioid sarcoma and myoepithelial carcinoma are very rare in the vulvar region, and few of these cases have been evaluated for SMARCB1 protein loss by immunohistochemistry (IHC) or for SMARCB1 gene alterations by molecular genetic techniques. We studied the clinicopathologic, IHC, and molecular genetic features of 14 SMARCB1-deficient vulvar neoplasms. All available routinely stained sections were reexamined, and IHC analysis for wide-spectrum cytokeratins, high-molecular weight cytokeratins, epithelial membrane antigen, S100 protein, CD34, smooth muscle actin, desmin, and SMARCB1 was performed. Multiplex ligation-dependent probe amplification and DNA sequencing of the SMARCB1 gene was performed on 12 cases with sufficient available tissue. The 14 vulvar tumors occurred in adult women (mean age 46 y, range 22 to 62 y) and measured 1.1 to 8.8 cm in size (mean 4.7 cm). Tumors were classified as classical-type epithelioid sarcoma (N=1), proximal-type epithelioid sarcoma (N=6), myoepithelial carcinoma (N=4), and "SMARCB1-deficient vulvar sarcoma, not otherwise specified" (N=3) on the basis of combined histopathologic and IHC findings. One myoepithelial carcinoma showed divergent rhabdomyoblastic differentiation. All tested cases showed partial or complete SMARCB1 deletions (homozygous: 9 cases; heterozygous: 3 cases). One case with a heterozygous deletion also showed a c.528delC mutation in exon 5. Fluorescence in situ hybridization for EWSR1 rearrangement was performed for 3 cases classified as myoepithelial carcinoma and was negative. Follow-up (13 patients, range 5 to 72 mo, mean 31 mo) data showed 3 patients dead of disease, 1 alive with unresectable metastatic disease, 1 alive with radiographic evidence of extensive lymph nodal disease, and 8 alive without disease. We conclude that SMARCB1-deficient vulvar neoplasms chiefly comprise epithelioid sarcoma and myoepithelial carcinoma, although some defy easy classification. No association was seen between clinical behavior and the type of SMARCB1 alteration.