Narrowing the critical region for a rhabdoid tumor locus in 22q11

Insights into brain tumor diagnosis: exploring in situ hybridization techniques

Objectives

Diagnosing brain tumors is critical due to their complex nature. This review explores the potential of in situ hybridization for diagnosing brain neoplasms, examining their attributes and applications in neurology and oncology.

Methods

The review surveys literature and cross-references findings with the OMIM database, examining 513 records. It pinpoints mutations suitable for in situ hybridization and identifies common chromosomal and gene anomalies in brain tumors. Emphasis is placed on mutations' clinical implications, including prognosis and drug sensitivity.

Results

Amplifications in EGFR, MDM2, and MDM4, along with Y chromosome loss, chromosome 7 polysomy, and deletions of PTEN, CDKN2/p16, TP53, and DMBT1, correlate with poor prognosis in glioma patients. Protective genetic changes in glioma include increased expression of ADGRB3/1, IL12B, DYRKA1, VEGFC, LRRC4, and BMP4. Elevated MMP24 expression worsens prognosis in glioma, oligodendroglioma, and meningioma patients. Meningioma exhibits common chromosomal anomalies like loss of chromosomes 1, 9, 17, and 22, with specific genes implicated in their development. Main occurrences in medulloblastoma include the formation of isochromosome 17q and SHH signaling pathway disruption. Increased expression of BARHL1 is associated with prolonged survival. Adenomas mutations were reviewed with a focus on adenoma-carcinoma transition and different subtypes, with MMP9 identified as the main metalloprotease implicated in tumor progression.

Discussion

Molecular-genetic diagnostics for common brain tumors involve diverse genetic anomalies. In situ hybridization shows promise for diagnosing and prognosticating tumors. Detecting tumor-specific alterations is vital for prognosis and treatment. However, many mutations require other methods, hindering in situ hybridization from becoming the primary diagnostic method.

SMARCB1 Gene Therapy Using a Novel Tumor-Targeted Nanomedicine Enhances Anti-Cancer Efficacy in a Mouse Model of Atypical Teratoid Rhabdoid Tumors

Purpose

Atypical teratoid rhabdoid tumor (ATRT) is a deadly, fast-growing form of pediatric brain cancer with poor prognosis. Most ATRTs are associated with inactivation of SMARCB1, a subunit of the chromatin remodeling complex, which is involved in developmental processes. The recent identification of SMARCB1 as a tumor suppressor gene suggests that restoration of SMARCB1 could be an effective therapeutic approach.

Methods

We tested SMARCB1 gene therapy in SMARCB1-deficient rhabdoid tumor cells using a novel tumor-targeted nanomedicine (termed scL-SMARCB1) to deliver wild-type SMARCB1. Our nanomedicine is a systemically administered immuno-lipid nanoparticle that can actively cross the blood-brain barrier via transferrin receptor-mediated transcytosis and selectively target tumor cells via transferrin receptor-mediated endocytosis. We studied the antitumor activity of the scL-SMARCB1 nanocomplex either as a single agent or in combination with traditional treatment modalities in preclinical models of SMARCB1-deficient ATRT.

Results

Restoration of SMARCB1 expression by the scL-SMARCB1 nanocomplex blocked proliferation, and induced senescence and apoptosis in ATRT cells. Systemic administration of the scL-SMARCB1 nanocomplex demonstrated antitumor efficacy as monotherapy in mice bearing ATRT xenografts, where the expression of exogenous SMARCB1 modulates MYC-target genes. scL-SMARCB1 demonstrated even greater antitumor efficacy when combined with either cisplatin-based chemotherapy or radiation therapy, resulting in significantly improved survival of ATRT-bearing mice.

Conclusion

Collectively, our data suggest that restoring SMARCB1 function via the scL-SMARCB1 nanocomplex may lead to therapeutic benefits in ATRT patients when combined with traditional chemoradiation therapies.

Constitutional balanced translocations involving SMARCB1: A rare cause of rhabdoid tumor predisposition syndrome

Rhabdoid Tumor Predisposition Syndrome 1 (RTPS1) confers an increased risk of developing rhabdoid tumors and is caused by germline mutations in SMARCB1. RTPS1 should be evaluated in all individuals with rhabdoid tumor and is more likely in those with a young age at presentation (occasionally congenital presentation), multiple primary tumors, or a family history of rhabdoid tumor or RTPS1. Proband genetic testing is the standard method for diagnosing RTPS1. Most known RTPS1-related SMARCB1 gene mutations are copy number variants (CNVs) or single nucleotide variants/indels, but structural variant analysis (SVA) is not usually included in the molecular evaluation. Here, we report two children with RTPS1 presenting with atypical teratoid/rhabdoid tumor (ATRT) who had constitutional testing showing balanced chromosome translocations involving SMARCB1. Patient 1 is a 23-year-old female diagnosed with pineal region ATRT at 7 months who was found to have a de novo, constitutional t(16;22)(p13.3;q11.2). Patient 2 is a 24-month-old male diagnosed with a posterior fossa ATRT at 14 months, with subsequent testing showing a constitutional t(5;22)(q14.1;q11.23). These structural rearrangements have not been previously reported in RTPS1. While rare, these cases suggest that structural variants should be considered in the evaluation of children with rhabdoid tumors to provide more accurate genetic counseling on the risks of developing tumors, the need for surveillance, and the risks of passing the disorder on to future children. Further research is needed to understand the prevalence, clinical features, and tumor risks associated with RTPS1-related constitutional balanced translocations.

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.

Malignant Rhabdoid Tumor, an Aggressive Tumor Often Misclassified as Small Cell Variant of Hepatoblastoma

The clinical management of pediatric liver tumors involves stratification into risk groups. One previously defined, high-risk group of hepatoblastomas is the small cell undifferentiated variant. In light of molecular studies showing SMARCB1 deletion in these tumors, it is now recognized that most small cell, undifferentiated liver tumors represent an aggressive unrelated tumor—the malignant rhabdoid tumor (MRT). SMARCB1 is a member of the chromatin remodeling SWI/SNF complex and encodes the INI1 protein. The histologic diagnosis of MRT is currently based on INI1 negative immunoreactivity and the presence of rhabdoid morphology. INI1-negative small cell liver tumors lacking classic rhabdoid morphology are often misclassified as small cell undifferentiated hepatoblastomas (SCUD-HB), according to the current classification. Pediatric liver tumors diagnosed between 2003–2017 as SCUD-HB (four cases) or MRT (two cases) were identified from the Columbia University Pathology Department Archives. All tumors were associated with normal or low serum alpha fetoprotein levels, and showed an absence of immunohistochemical staining of hepatocellular markers (Hep-par1, Arginase) and loss of INI1 staining. Two cases were initially diagnosed as MRT, one with prominent rhabdoid morphology, the other with predominant small cell morphology. The remaining four cases with small cell morphology were classified as SCUD-HB. Ancillary molecular studies confirmed the loss of SMARCB1, supporting the diagnosis of MRT in all cases, proving morphology an unreliable criterion. It is critical to eliminate the term INI1-negative hepatoblastoma from the current classification scheme, and classify INI1-negative tumors as MRT, particularly since high-risk HB-chemotherapy regimens are not effective for treating MRT.

Case-based review: atypical teratoid/rhabdoid tumor

Atypical teratoid/rhabdoid tumor (AT/RT) is a rare CNS cancer that typically occurs in children younger than 3 years of age. Histologically, AT/RTs are embryonal tumors that contain a rhabdoid component as well as areas with primitive neuroectodermal, mesenchymal, and epithelial features. Compared to other CNS tumors of childhood, AT/RTs are characterized by their rapid growth, short symptomatic prodrome, and large size upon presentation, often leading to brain compression and intracranial hypertension requiring urgent intervention. For decades, the mainstay of care has been a combination of maximal safe surgical resection followed by adjuvant chemotherapy and radiotherapy. Despite advances in each of these modalities, the relative paucity of data on these tumors, their inherently aggressive course, and a lack of molecular data have limited advances in treatment over the past 3 decades. Recent large-scale, multicenter interdisciplinary studies, however, have significantly advanced our understanding of the molecular pathogenesis of these tumors. Multiple clinical trials testing molecularly targeted therapies are underway, offering hope for patients with AT/RT and their families.

SMARCB1-deficient Tumors of Childhood: A Practical Guide

The SMARCB1 gene ( INI1, BAF47) is a member of the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex, involved in the epigenetic regulation of gene transcription. SMARCB1 acts as a tumor suppressor gene, and loss of function of both alleles gives rise to SMARCB1-deficient tumors. The prototypical SMARCB1-deficient tumor is the malignant rhabdoid tumor (MRT) which was first described in the kidney but also occurs in soft tissue, viscera, and the brain (where it is referred to as atypical teratoid rhabdoid tumor or AT/RT). These are overwhelmingly tumors of the very young, and most follow an aggressive and ultimately lethal course. Morphologically, most but not all contain a population of "rhabdoid" cells, which are large cells with abundant cytoplasm, perinuclear spherical inclusions, and eccentric vesicular nuclei with large inclusion-like nucleoli. MRT immunohistochemistry reveals complete loss of SMARCB1 nuclear expression, and molecular analysis confirms biallelic SMARCB1 inactivation in the vast majority. Rare AT/RTs have loss of SMARCA4, another SWI/SNF member, rather than SMARCB1. With the widespread adoption of SMARCB1 immunohistochemistry, an increasing number of SMARCB1-deficient tumors outside of the MRT-AT/RT spectrum have been described. In addition to MRT and AT/RT, pediatric tumors with complete loss of SMARCB1 expression include cribriform neuroepithelial tumor, renal medullary carcinoma, and epithelioid sarcoma. Tumors with variable loss of SMARCB1 expression include subsets of epithelioid malignant peripheral nerve sheath tumor, schwannomas arising in schwannomatosis, subsets of chordomas, myoepithelial carcinomas, and sinonasal carcinomas. Variable and reduced expression of SMARCB1 is characteristic of synovial sarcoma. In this review, the historical background, clinical characteristics, morphology, immunohistochemical features, and molecular genetics most germane to these tumors are summarized. In addition, familial occurrence of these tumors (the rhabdoid tumor predisposition syndrome) is discussed. It is hoped that this review may provide practical guidance to pathologists encountering tumors that have altered expression of SMARCB1.

Atypical teratoid rhabdoid tumors: a population-based clinical outcomes study involving 174 patients from the Surveillance, Epidemiology, and End Results database (1973-2010)

Introduction

Atypical teratoid rhabdoid tumors (ATRTs) are rare, highly malignant embryonal tumors of the central nervous system (CNS) accounting for 20% of CNS tumors in children under the age of 3. This study examines a large cohort of ATRT patients to determine demographic, clinical, and pathologic factors which impact prognosis and survival.

Methods

Demographic and clinical data were abstracted on 174 ATRT patients (171 pediatric patients age <20 and 3 adult patients age ≥20) from the Surveillance, Epidemiology, and End Results database (1973–2010). Standard statistical methodology was used.

Results

A total of 174 ATRT cases (mean age of 2.84 years) were identified. ATRT had a higher incidence in males (56.3%), Caucasians (59.1%), and children <3 years of age (80.5%), P<0.001. The most common primary sites were the cerebellum (17.8%), ventricles (16.1%), and frontal lobe (12.6%). Mean overall survival was 3.2±0.4 years, while overall and cancer-specific mortality were 63.2% and 56.3%, respectively, P=0.005. Most ATRT cases were treated with surgery alone (58.0%), followed by a combination of surgery and radiation (34.3%), no treatment (6.5%), and radiation alone (1.2%). The use of combination therapy has increased significantly (16.1%) since 2005 (P<0.001), while primary surgical resection and radiation therapy rates remain relatively unchanged. The longest survival was observed among ATRT patients receiving combination therapy (5.9±0.7 years), followed by radiation alone (2.8±1.2 years), and surgery alone (1.9±0.4 years), P<0.001. Multivariable analysis identified only distant metastases (OR =4.6) as independently associated with increased mortality, whereas combination therapy (OR =0.4) was associated with reduced mortality, P<0.005.

Conclusion

ATRT is a rare and highly aggressive embryonal malignancy of the CNS that presents more often as locoregional tumors >4 cm in male Caucasian children of age <3 years, involving the cerebellum, ventricles, or frontal lobe. Combination therapy significantly improves survival, and its use has been increasing since 2005.

Rhabdoid tumor predisposition syndrome

Rhabdoid tumors (RT), or malignant rhabdoid tumors, are among the most aggressive and lethal forms of human cancer. They can arise in any location in the body but are most commonly observed in the brain, where they are called atypical teratoid/rhabdoid tumors (AT/RT), and in the kidneys, where they are called rhabdoid tumors of the kidney. The vast majority of rhabdoid tumors present with a loss of function in the SMARCB1 gene, also known as INI1, BAF47, and hSNF5, a core member of the SWI/SNF chromatin-remodeling complex. Recently, mutations in a 2nd locus of the SWI/SNF complex, the SMARCA4 gene, also known as BRG1, were found in rhabdoid tumors with retention of SMARCB1 expression. Familial cases may occur in a condition known as rhabdoid tumor predisposition syndrome (RTPS). In RTPS, germline inactivation of 1 allele of a gene occurs. When the mutation occurs in the SMARCB1 gene, the syndrome is called RTPS1, and when the mutation occurs in the SMARCA4 gene it is called RTPS2. Children presenting with RTPS tend to develop tumors at a younger age, but the impact that germline mutation has on survival remains unclear. Adults who carry the mutation tend to develop multiple schwannomas. The diagnosis of RTPS should be considered in patients with RT, especially if they have multiple primary tumors, and/or in individuals with a family history of RT. Because germline mutations result in an increased risk of carriers developing RT, genetic counseling for families with this condition is recommended.

SMARCB1 deletion by a complex three-way chromosomal translocation in an extrarenal malignant rhabdoid tumor

Rhabdoid tumors (RTs) are highly aggressive malignant neoplasms of early childhood that arise in the kidney, brain, and extrarenal sites. The disease is genetically defined by biallelic disruption of the SMARCB1/INI1/SNF5 tumor suppressor gene, a core component of the ATP-dependent chromatin remodeling SWI/SNF complex. The molecular changes leading to SMARCB1 alterations in RTs are heterogeneous, including germline or constitutional inactivating mutations, partial or total gene deletions, copy number neutral loss of heterozygosity, and, less commonly, reciprocal translocations. We report a novel three-way chromosomal rearrangement, which was identified by conventional cytogenetic and sequential fluorescence in situ hybridization studies as the underlying molecular mechanism of the loss of SMARCB1 in an extrarenal RT. This case highlights the heterogeneity of genetic events that may lead to the loss of SMARCB1 and the development of RTs.

Atypical teratoid/rhabdoid tumor with ganglioglioma-like differentiation: case report and review of the literature

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly aggressive embryonal tumor of the central nervous system, which typically affects young children. A characteristic feature of AT/RT is a polyphenotypic immunoprofile and ultrastructural diversity. The morphologic and antigenic heterogeneity of AT/RT give it the potential to mimic other embryonal central nervous system tumors, epithelial neoplasms or mesenchymal tumors. Alternatively, "collision-type" tumors have been published, in which AT/RT coexists with a separate low-grade central nervous system tumor. Here, we report a case of AT/RT with morphologic and immunohistochemical evidence of extensive ganglioglioma-like differentiation with only a small focal primitive component and minimal rhabdoid cytology. Fluorescence in situ hybridization and immunohistochemistry demonstrated INI1/BAF47 gene/protein losses in both histologic components. To the best of our knowledge, this is the first reported case of AT/RT with extensive ganglioglioma-like differentiation. This unique case supports the notion that routine application of INI1 stains/in situ hybridization can capture AT/RT with unexpected patterns of differentiation.

Embryonal tumor with abundant neuropil and true rosettes: an autopsy case-based update and review of the literature

INTRODUCTION

Embryonal tumor with abundant neuropil and true rosettes (ETANTR) is a rare subtype of primitive neuroectodermal tumors first reported in 2000. It is rare among the group of embryonal central nervous system tumors with approximately 50 reported cases. ETANTR has been suggested to be a separate entity among this group of tumors.

CASE REPORT

Herein, we present only the second autopsy case of ETANTR, which occurred in a 17-month-old boy, and was located in the brainstem. The tumor was inoperable, and despite chemotherapy, the child died 3 months after initial hospitalization. A brain only autopsy was performed.

DISCUSSION

Neuropathological and neuroimaging examinations suggest ETANTR grew by expansion rather than invasion distorting anatomical structures of the posterior fossa. We suggest that the characteristic histopathological picture of the tumor is the result of multifocal and dispersed germinative activity surrounded by mature neuropil-like areas.

CONCLUSION

ETANTR is a pediatric tumor occurring in children under 4 with a significantly poor prognosis with more cases and research required to characterize this rare embryonal tumor.

The challenging diagnosis of the rhabdoid carcinoma of the pelvis: a case report with literature review

Rhabdoid tumor is an uncommon neoplasia characterized by a monotonous population of large, noncohesive cells with vesicular nuclei and large nucleoli. The misleading name was originally suggested because of the striking morphologic resemblance to other skeletal muscle tumors, but neither ultrastructural nor immunohistochemical features support a myogenic origin for this tumor. The rhabdoid tumors of the kidney in pediatric age are characterized by mutation or deletion of 22q11. In adults, tumors with rhabdoid features are uncommon neoplasia reported in different anatomic sites, but their histogenesis is still unclear. We focused on the literature data regarding the rhabdoid features in pelvic and renal tumors, and we describe a carcinoma involving the pelvis and the kidney with exclusive rhabdoid features, which make the anatomical allocation of the tumor difficult. The tumor did not exhibit any similarities to conventional histologic types of renal cell cancer, not even of the sarcomatous type. Tumor cells showed a strong positivity for epithelial markers (AE1/AE3 and CK 8) and for vimentin, whereas they were negative for skeletal and smooth muscle markers. The nuclei of the tumor cells demonstrated a INI1-positive immunohistochemical stain, indicating the lack of mutation or deletion of the 22q11 chromosome. The appropriate diagnosis is that of an extrarenal high-grade rhabdoid carcinoma originating from the urothelium of the renal pelvis. The decision as to whether the tumor arose primarily in the renal parenchyma or in the renal pelvis could be of therapeutic importance. Appropriate immunohistochemical markers can help in the difficult differential diagnosis.

INI1-deficient tumors: diagnostic features and molecular genetics

Significant progress has been made in understanding the molecular genetic alterations involved in sarcomagenesis. Cytogenetic and molecular studies have identified nonrandom genetic abnormalities, including tumor suppressor gene inactivation. Mutations, deletions, and other somatic alterations in the tumor suppressor gene INI1 (hSNF5; SMARCB1), which encodes a subunit of the SWI/SNF chromatin remodeling complex, were first described in the malignant rhabdoid tumor of infancy. Since then, INI1 has also been implicated in the pathogenesis of additional tumor types including renal medullary carcinomas and epithelioid sarcomas and a subset of epithelioid malignant peripheral nerve sheath tumors, myoepithelial carcinomas, and extraskeletal myxoid chondrosarcomas. As varied as this group appears, they all show loss of INI1 protein expression, a propensity for rhabdoid cytomorphology, and sometimes other overlapping immunohistochemical and histologic findings. We will review the clinicopathologic features of these tumor types and emphasize the clinical utility of INI1 immunohistochemistry in differential diagnosis.

p16INK4A and p14ARF tumor suppressor pathways are deregulated in malignant rhabdoid tumors

Malignant rhabdoid tumors (MRTs) are aggressive tumors associated with mutations in the SMARCB1 gene. In experimental systems, the loss of SMARCB1 is hypothesized to alter p16(INK4A) pathways resulting in the repression of tumor suppressors. To determine whether these pathways are deregulated in human MRT, we used immunohistochemistry on tissue microarrays to evaluate p16(INK4A)/E2F1/RB and p14(ARF)/MDM2/p53 pathways in 25 atypical teratoid/rhabdoid tumors (AT/RT) and 11 non-CNS MRT. p16(INK4A) was negative or showed focal weak expression. p16(INK4A) downstream targets CDK4/cyclin D1/ppRB were variably expressed at moderate to low levels; E2F1 was negative. Unexpectedly, p14(ARF) expression was seen in many cases, which correlated positively with p53 and inversely with MDM2 immunostaining in AT/RT. TP53 mutational analysis in 19 of 25 AT/RT and in 8 of 11 non-CNS MRT cases showed point mutations in only 3 AT/RT cases, suggesting that p53 expression was driven mainly by p14(ARF). Finally, nucleophosmin, a protein that stabilizes p53, was positive in most cases and colocalized with p53. Together, these data suggest that, in MRT, there is deregulation not only of p16(INK4A) but also of the p14(ARF) pathway. These results provide insights into cell cycle deregulation in the pathogenesis of human MRT and may aid in the design and evaluation of potential therapies for these tumors.

Molecular Diagnostics of Soft Tissue Tumors

Context.—Soft tissue pathology encompasses a remarkably diverse assortment of benign and malignant soft tissue tumors. Rendering a definitive diagnosis is complicated not only by the large volume of existing histologic subtypes (&gt;100) but also frequently by the presence of overlapping clinical, histologic, immunohistochemical, and/or radiographic features. During the past 3 decades, mesenchymal tumor–specific, cytogenetic and molecular genetic abnormalities have demonstrated an increasingly important, ancillary role in mesenchymal tumor diagnostics.

Objectives.—To review molecular diagnostic tools available to the pathologist to further classify specific soft tissue tumor types and recurrent aberrations frequently examined. Advantages and limitations of individual approaches will also be highlighted.

Data Sources.—Previously published review articles, peer-reviewed research publications, and the extensive cytogenetic and molecular diagnostic experience of the authors to include case files of The University of Nebraska Medical Center.

Conclusions.—Cytogenetic and molecular genetic assays are used routinely for diagnostic purposes in soft tissue pathology and represent a powerful adjunct to complement conventional microscopy and clinicoradiographic evaluation in the formulation of an accurate diagnosis. Care should be taken, however, to recognize the limitations of these approaches. Ideally, more than one technical approach should be available to a diagnostic laboratory to compensate for the shortcomings of each approach in the assessment of individual specimens.

Embryonal tumors with abundant neuropil and true rosettes: 2 illustrative cases and a review of the literature

Embryonal tumor with abundant neuropil and true rosettes (ETANTR) is a recently identified variant of primitive neuroectodermal tumor, with fewer than 50 cases reported in the literature to date. Histologically, this tumor has features of ependymoblastoma and neuroblastoma, demonstrating areas of fine fibrillary neuropil intermingled with ependymoblastic rosettes and zones of undifferentiated neuroepithelial cells. However, ETANTR is distinguished pathologically from other embryonal tumors by the striking abundance of neuropil. Clinically, ETANTRs have shown high malignant potential and poor clinical outcome despite aggressive treatment. The authors describe 2 illustrative surgical cases of ETANTR, one involving the longest reported survival in the literature to date. The other had a poor outcome despite high-dose adjuvant chemotherapy with sequential autologous hematopoietic stem cell rescue. The authors review the natural history and treatment strategies available for this unusual malignant pediatric brain tumor.

Differential expression profiling between atypical teratoid/rhabdoid and medulloblastoma tumor in vitro and in vivo using microarray analysis

OBJECTIVES

Atypical teratoid/rhabdoid tumor (AT/RT) and medulloblastoma (MB) are the most malignant primary brain tumors in early childhood. AT/RT is frequently misdiagnosed as primitive neuroectodermal tumor/medulloblastoma. The biological features and clinical outcomes of AT/RT and MB are extremely different. In this study, we used microarray as a platform to distinguish these two tumors with the definitive diagnostic marker as well as the profiling of expression genes.

METHODS

In order to clarify the pathogenesis and find the biological markers for AT/RT, we established a derivative AT/RT primary cell culture. The differential profiling between AT/RT and MB were analyzed by using microarray method.

RESULTS

With the use of the microarray method, we demonstrated that 15 genes were significantly changed (at least 5-fold in upregulation and 1/5-fold in downregulation) between AT/RT and MB in tissues and cell lines. The quantitative reverse transcription-polymerase chain reaction analyses further confirmed that mRNA expression levels of SERPINI1 and osteopontin were highly expressed in AT/RT cells and tissues than those in MB. Importantly, our microarray result suggested that AT/RT presents the stemness-like pattern and expression profiling of embryonic stem cells as well as high mRNA expressions of Oct-4, Nanog, Sox-2, and c-Myc.

CONCLUSIONS

Our study demonstrated the differential gene expression profiling between AT/RT and MB. Based on the microarray findings, AT/RTs present embryonic stem-like gene recapitulation and further provide novel insights into their underlying biology.

Mixed epithelial and stromal tumors of the kidney: an overview

Mixed epithelial and stromal tumor of the kidney is a recently recognized distinct neoplasm that should be distinguished from other renal neoplasms. These tumors are relatively rare with a female preponderance. Imaging studies are not diagnostic but reveal a solid or solid and cystic mass in most cases. Histopathologically, these tumors reveal biphasic growth pattern comprising mesenchymal and epithelial elements with characteristic estrogen and progesterone receptor immunoreactive mesenchyme reminiscent of ovarian stroma. Malignant transformation, recurrence, and metastasis are rare; however, recently a few cases of malignant mixed epithelial and stromal tumors have been reported in the literature. Recently a case with translocation t(1;19) has been described. This article provides a brief overview of the current knowledge of mixed epithelial and stromal tumor of the kidney.

Imprinted CDKN1C is a tumor suppressor in rhabdoid tumor and activated by restoration of SMARCB1 and histone deacetylase inhibitors

SMARCB1 is deleted in rhabdoid tumor, an aggressive paediatric malignancy affecting the kidney and CNS. We hypothesized that the oncogenic pathway in rhabdoid tumors involved epigenetic silencing of key cell cycle regulators as a consequence of altered chromatin-remodelling, attributable to loss of SMARCB1, and that this hypothesis if proven could provide a biological rationale for testing epigenetic therapies in this disease. We used an inducible expression system to show that the imprinted cell cycle inhibitor CDKN1C is a downstream target for SMARCB1 and is transcriptionally activated by increased histone H3 and H4 acetylation at the promoter. We also show that CDKN1C expression induces cell cycle arrest, CDKN1C knockdown with siRNA is associated with increased proliferation, and is able to compete against the anti-proliferative effect of restored SMARCB1 expression. The histone deacetylase inhibitor (HDACi), Romidepsin, specifically restored CDKN1C expression in rhabdoid tumor cells through promoter histone H3 and H4 acetylation, recapitulating the effect of SMARCB1 on CDKNIC allelic expression, and induced cell cycle arrest in G401 and STM91-01 rhabdoid tumor cell lines. CDKN1C expression was also shown to be generally absent in clinical specimens of rhabdoid tumor, however CDKN1A and CDKN1B expression persisted. Our observations suggest that maintenance of CDKN1C expression plays a critical role in preventing rhabdoid tumor growth. Significantly, we report for the first time, parallels between the molecular pathways of SMARCB1 restoration and Romidepsin treatment, and demonstrate a biological basis for the further exploration of histone deacetylase inhibitors as relevant therapeutic reagents in the treatment of rhabdoid tumor.

Loss of INI1 expression defines a unique subset of pediatric undifferentiated soft tissue sarcomas

Malignant rhabdoid tumor has traditionally been defined by its histologic phenotype. However, genetic investigations of malignant rhabdoid tumor have revealed a characteristic loss of or mutation in the INI1 gene on chromosome 22q. The occurrence and significance of soft tissue tumors meeting genetic criteria for malignant rhabdoid tumor but with an undifferentiated non-rhabdoid histology is poorly characterized. Seventeen undifferentiated sarcomas, lacking rhabdoid histology were identified either through the surgical pathology files of The Children's Hospital of Philadelphia (1980-2005) or in consultation. Immunohistochemistry for the INI1 protein showed a loss of nuclear expression within tumor cells in five of these cases. On histologic review, these five tumors had a featureless sheet-like architecture; four were small round blue cell tumors, and one showed focal spindling. Although they had variably prominent nucleoli, classic rhabdoid morphologic features were not identified in any of these cases at primary presentation. Additional immunohistochemistry showed a polyphenotypic profile. Four of the five tumors showed genetic abnormalities involving the INI1 gene by a combination of fluorescent in situ hybridization, reverse transcription-polymerase chain reaction, and/or mutational analysis. Patient ages ranged from 1 week to 5 years. Four patients were male, and one was female. Sites included two neck tumors, two extremity tumors, and one paraspinal tumor. Two patients are alive and well over 15 years from the time of diagnosis; the remaining four are alive and well but with less than 2 years follow-up. Thus, alterations of the INI1 gene with consequent loss of expression identified a population of undifferentiated sarcomas lacking classic rhabdoid morphology in young patients, with evidence of favorable survival. Whether these undifferentiated sarcomas represent a clinicopathologic entity distinct from classic malignant rhabdoid tumor requires further investigation.

Dependence on PI3K/Akt signaling for malignant rhabdoid tumor cell survival

PURPOSE

Malignant rhabdoid tumors (MRT), although rare, are one of the most aggressive pediatric malignancies. Loss of INI1, a tumor suppressor gene and member of the SWI/SNF chromatin remodeling complex, is a recurrent genetic characteristic of these tumors and an important diagnostic marker. We have previously demonstrated a novel interaction between the serine/threonine kinase Akt and INI1, as well as other SWI/SNF subunits. This, coupled with experiments in the literature suggesting that the PI3K/Akt pathway is dysregulated in MRT cells, caused us to investigate the activation and importance of this pathway in this tumor type.

METHODS

In this study, we used MTT assays to evaluate the sensitivity of MRT cell lines to PI3K inhibition. Western blot analysis and Raf pulldown assays were used to examine potential mechanisms of PI3K/Akt dysregulation.

RESULTS

Inhibition of the PI3K/Akt pathway caused a significant reduction in the survival of the four MRT cell lines tested, and three cell lines demonstrated constitutively active Akt. Two of these constitutively active Akt cell lines abundantly expressed IGF-1R and an inhibitor of IGF-1R, NVP-AEW541, reduced Akt phosphorylation in one of them. The third constitutively active Akt cell line appeared to express a mutant IGF-1R.

CONCLUSIONS

Our data suggests that the PI3K/Akt pathway is a crucial means of maintaining the survival and growth of MRT cells. The cells therefore employ various mechanisms to stimulate this pathway, and growth factor receptor dysregulation appears to be a common method. Drugs that inhibit the PI3K pathway or interfere with IGF autocrine loops may be of great value in treating MRT, which is largely resistant to conventional chemotherapeutic approaches.

Identification of CD133-positive radioresistant cells in atypical teratoid/rhabdoid tumor

Atypical teratoid/rhabdoid tumor (AT/RT) is an extremely malignant neoplasm in the central nervous system (CNS) which occurs in infancy and childhood. Recent studies suggested that CD133 could be considered a marker for brain cancer stem-like cells (CSCs). However, the role of CD133 in AT/RT has never been investigated. Herein we report the isolation of CD133-positive cells (CD133⁺), found to have the potential to differentiate into three germ layer tissues, from tissues of nine AT/RT patients. The migration/invasion/malignancy and radioresistant capabilities of CD133⁺ were significantly augmented when compared to CD133⁻. The clinical data showed that the amount of CD133⁺ in AT/RTs correlated positively with the degree of resistance to radiation therapy. Using cDNA microarray analysis, the genotoxic–response profiles of CD133⁺ and CD133⁻ irradiated with 10 Gy ionizing radiation (IR) were analyzed 0.5, 2, 6, 12 and 24 h post-IR. We then validated these microarray data and showed increased phosphorylation after IR of p-ATM, p-RAD17, and p-CHX2 as well as increased expression of BCL-2 protein in CD133⁺ compared to CD133⁻. Furthermore, we found that CD133⁺ can effectively resist IR with cisplatin- and/or TRAIL-induced apoptosis. Immunohistochemical analysis confirmed the up-regulated expression of p-ATM and BCL-2 proteins in IR-treated CD133⁺ xenotransgrafts in SCID mice but not in IR-treated CD133⁻. Importantly, the effect of IR in CD133⁺ transplanted mice can be significantly improved by a combination of BCL-2 siRNA with debromohymenialdisine, an inhibitor of checkpoint kinases. In sum, this is the first report indicating that CD133⁺ AT/RT cells demonstrate the characteristics of CSCs. The IR-resistant and anti-apoptotic properties in CD133⁺ may reflect the clinical refractory malignancy of AT/RTs and thus the activated p-ATM pathway and BCL-2 expression in CD133⁺ could be possible targets to improve future treatment of deadly diseases like AT/RT.

Malignant mixed epithelial and stromal tumor of the kidney with rhabdoid features: report of a case including immunohistochemical, molecular genetic studies and comparison to morphologically similar renal tumors

Mixed epithelial stromal tumor of the kidney (MEST)/adult cystic nephroma (CN) is a lesion characterized by epithelial lined tubular or cystic structures interspersed within a variably prominent, distinctive spindle-cell stroma. Although typically benign, cases with malignant features have been reported. Herein, we report a MEST/CN with malignant stromal features and rhabdoid differentiation arising in the left kidney of an 84-year-old woman. Histologically, the tumor displayed multiple tubules and variably sized cystic structures lined by benign epithelium with an intervening malignant-appearing spindle-cell stroma. The malignant stroma displayed condensation in the regions surrounding the epithelial component consistent with the ovarian-like stroma typically observed in MEST/CN. In addition, the stromal cells displayed extensive rhabdoid differentiation. Immunohistochemical analysis revealed strong expression of cytokeratin 7, CAM 5.2, AE1/AE3, wide-spectrum keratin, and epithelial membrane antigen by the epithelial component. The stromal component displayed strong immunohistochemical expression of WT-1, CD-99, CD-56, INI1, and estrogen receptor; focal actin positivity; and was negative for desmin, myogenin, and progesterone receptor. Analysis by reverse transcriptase polymerase chain reaction failed to identify the SYT-SSX1 or SYT-SSX2 fusion transcripts characteristic of synovial sarcoma. To our knowledge, this represents the first report in the literature of malignant MEST with rhabdoid features and suggests that this entity should be considered in the diagnosis of renal stromal malignancies with prominent rhabdoid features.

Congenital renal rhabdoid tumor with placental metastases: immunohistochemistry, cytogenetic, and ultrastructural findings

Malignant congenital tumors of fetal origin are rare lesions, the most common type being congenital neuroblastoma. Although prenatal diagnosis is possible in large tumors, occasionally the tumor will be diagnosed first by its metastatic involvement of the placenta. Placental metastases can reflect either maternal or fetal primary sites, and each has relatively specific patterns of placental involvement. We describe the clinical and pathologic features of a widely metastatic congenital renal rhabdoid tumor with its placental and autopsy findings, and include the immunohistochemical, cytogenetic, and ultrastructural features. The pathologic features of the placenta in congenital renal rhabdoid tumor with placental metastasis have not been previously described. The examination of the placenta in this case led to the initial diagnosis and obviated the need for additional diagnostic procedures.

Imaging findings in primary intracranial atypical teratoid/rhabdoid tumors

BACKGROUND

Intracranial atypical teratoid/rhabdoid tumors (AT/RT) are rare and extremely aggressive neoplasms seen primarily in childhood. Imaging features are often considered non-specific. However, correct diagnosis of AT/RT is important because these tumors have a markedly different clinical prognosis and require more aggressive therapy.

OBJECTIVE

To determine the imaging features of AT/RT.

MATERIALS AND METHODS

We retrospectively analyzed imaging findings in 11 patients with primary intracranial AT/RT presenting over a period of 5 years. CT (n=11), MR (n=7), clinical (n=11) and pathological (n=11) features were evaluated. FISH analysis showing monosomy of chromosome 22 (absence of bcr 22q11 locus) was available for three patients. Immunohistochemical staining for INI-1 (BAF47) was performed on all tumors.

RESULTS

There were 11 patients, 6 boys and 5 girls. The age of presentation varied from 1 month to 15 years (average age 3 years 8 months). Six tumors were located in the posterior fossa and five in the supratentorial compartment. The tumors showed a hyperdense solid component (64%) that showed moderate to marked enhancement with contrast medium. On MR imaging, the predominant signal pattern was isointensity on T1-weighted images (57%) and T2 shortening with heterogeneity on T2-weighted images (86%). All tumors were large in size (average 4.2 x 3.7 cm), and there was a tendency for calcification (36%), hemorrhage (46%), necrosis (46%) and perifocal edema (100%). There was also a high tendency for subarachnoid dissemination, with five patients (46%) demonstrating brain and/or spinal metastasis. At follow-up (n=7), six patients showed local recurrence. At the time of recurrence, all these patients showed extensive leptomeningeal spread of the disease in both intracranial and intraspinal compartments.

CONCLUSION

There are no specific imaging features for intracranial AT/RT. But a high tendency toward large size, a hyperdense solid component on CT scan with calcification, hemorrhage, necrosis and subarachnoid spread suggest that this tumor should be considered in the differential diagnosis of large pediatric intracranial tumors.

Molecular genetic alterations and gene expression profile of a malignant rhabdoid tumor of the kidney

Malignant rhabdoid tumor of the kidney (MRTK) is a rare but highly aggressive tumor in children, and knowledge about the molecular signature of this tumor is limited. We report the molecular genetic alterations and gene expression profile of an MRTK tumor that arose in a 4-month-old Japanese girl. Fluorescence in situ hybridization and Southern blot analyses revealed a homozygous deletion of an approximately 0.29-Mb genomic region bordered by the Rgr and DDT genes in these tumor cells. This deleted region encodes SMARCB1, a candidate tumor suppressor gene for MRTK. Using a high-density oligonucleotide DNA array, we found increased expression of 25 genes, including genes involved in the cell cycle (10 genes), DNA replication (3 genes), cell growth (5 genes), and cell proliferation (5 genes), in this MRTK tumor sample, compared with a noncancerous kidney (NK) sample. On the other hand, 64 genes, including 4 genes regulating apoptosis, were found to show decreased expression in this MRTK tumor sample, compared with the NK sample. Among these alterations, we found alterations of expression of some genes, such as IGF2, MDK, TP53, and TNFSF10, in this MRTK tumor, as described previously. The molecular genetic alterations and altered pattern of gene expression found in this case may have contributed to the biological characteristics of the MRTK tumor that arose in our patient.

Genetic ablation of Cyclin D1 abrogates genesis of rhabdoid tumors resulting from Ini1 loss

Rhabdoid tumors are aggressive pediatric malignancies for which, currently, there are no effective or standard treatment strategies. Rhabdoid tumors arise because of the loss of the tumor suppressor gene INI1. We have previously demonstrated that INI1 represses Cyclin D1 transcription in rhabdoid cells by directly recruiting histone deacetylase 1 complex to its promoter, leading to G(0)-G(1) arrest. Expression of Cyclin D1 overcomes cell cycle arrest mediated by INI1 and Cyclin D1 overexpression in human rhabdoid tumors is a common phenomenon. However, it is not clear whether Cyclin D1 is a critical downstream target of INI1 in vivo and whether the derepression of this gene is essential for rhabdoid tumorigenesis. To determine the requirement of Cyclin D1 for genesis of rhabdoid tumors in vivo, we developed Ini1 heterozygous mice by targeted disruption. We found that the tumors developed in these Ini1+/- mice are rhabdoid, defective for Ini1 protein, and like the human tumors, express Cyclin D1. We crossed Ini1+/- mice to Cyclin D1-/- mice and found that Ini1+/- mice with Cyclin D1 deficiency did not develop any spontaneous tumors, in contrast to the parental Ini1+/- mice. These results strongly support the hypothesis that Cyclin D1 is a key mediator in the genesis of rhabdoid tumors. Our results provide an in vivo proof of concept that drugs that target Cyclin D1 expression or activity could be potentially effective as novel therapeutic agents for rhabdoid tumors.

Molecular diagnostics in central nervous system tumors

Central nervous system (CNS) neoplasms can be diagnostically challenging, due to remarkably wide ranges in histologic appearance, biologic behavior, and therapeutic approach. Nevertheless, accurate diagnosis is the critical first step in providing optimal patient care. As with other oncology-based specialties, there is a rapidly expanding interest and enthusiasm for identifying and utilizing new biomarkers to enhance the day-to-day practice of surgical neuropathology. In this regard, the field is primed by recent advances in basic research, elucidating the molecular mechanisms of tumorigenesis and progression in the most common adult and pediatric brain tumors. Thus far, few have made the transition into routine clinical practice, the most notable example being 1p and 19q testing in oligodendroglial tumors. However, the field is rapidly evolving and many other biomarkers are likely to emerge as useful ancillary diagnostic, prognostic, or therapeutic aids. The goal of this article is to highlight the most common genetic alterations currently implicated in CNS tumors, focusing most on those that are either already in common use in ancillary molecular diagnostics testing or are likely to become so in the near future.

Increased expression of osteopontin gene in atypical teratoid/rhabdoid tumor of the central nervous system

The atypical teratoid/rhabdoid tumor, primary to the central nervous system, is a highly malignant and aggressive neoplasm of infancy and childhood. Although having distinct biological features and clinical outcomes, it is frequently misdiagnosed as primitive neuroectodermal tumor/medulloblastoma. To further distinguish the underlying pathogenesis and to identify biological markers for clinical use, an atypical teratoid/rhabdoid tumor-derived cell line was established and its gene expression pattern analyzed in comparison to the human astrocyte SVG12 cell line and the human DAOY medulloblastoma cell line using a complementary DNA microarray method. The osteopontin gene was found specifically upregulated in atypical teratoid/rhabdoid tumor cells. This specificity was confirmed by immunohistochemistry in pathological sections of tissues from atypical teratoid/rhabdoid tumor patients. Even though the role of osteopontin in the cytopathogenesis of atypical teratoid/rhabdoid tumor still needs to be determined, our data support that overexpressed osteopontin is a potential diagnostic marker for atypical teratoid/rhabdoid tumor.

Chromosome mechanisms and INI1 inactivation in human and mouse rhabdoid tumors

The human rhabdoid tumorigenesis orchestrated by INI1 inactivation is associated with specific rearrangements of chromosome 22 that correlate with preferential anatomic tumor locations. A literature review revealed significant correlations between an apparently normal karyotype and kidney tumors, monosomy 22 and cerebral tumors, and chromosome 22 translocations and tumors at other anatomic sites. In the mouse rhabdoid tumor model, specifically in the four tumors that we tested for loss of heterozygosity, neither partial deletion nor monosomy of chromosome 10 could be detected. In contrast to the human data, the only chromosome mechanism involved in the 18 mouse tumors studied appears to be a mitotic recombination or a nondisjunction-duplication. Additionally, and despite mouse tumor incidence across a variety of sites, no rhabdoid tumor could be observed in the mouse kidney. These data suggest that the chromosome mechanisms for INI1 inactivation and the selective cell survival pressure differ in human and mouse.

Atypical Teratoid/Rhabdoid Tumors (ATRT): Improved Survival in Children 3 Years of Age and Older With Radiation Therapy and High-Dose Alkylator-Based Chemotherapy

Purpose

To describe clinical features, therapeutic approaches, and prognostic factors in pediatric patients with atypical teratoid/rhabdoid tumors (ATRT) treated at St Jude Children's Research Hospital (SJCRH).

Patients and Methods

Primary tumor samples from patients diagnosed with ATRT at SJCRH between July 1984 and June 2003 were identified. Pathology review included histologic, immunohistochemical analysis, and fluorescence in situ hybridization for SMARCB1 (also known as hSNF5/INI1) deletion. Clinical records of patients with pathologic confirmation of ATRT were reviewed.

Results

Thirty-seven patients were diagnosed with ATRT at SJCRH during the 19-year study interval. Six patients were excluded from this clinical review based on pathologic or clinical criteria. Of the remaining 31 patients, 22 were younger than 3 years. Posterior fossa primary lesions and metastatic disease at diagnosis were more common in younger patients with ATRT. All patients underwent surgical resection; 30 received subsequent chemotherapy. The majority of patients aged 3 years or older received postoperative craniospinal radiation. Two-year event-free (EFS) and overall survival (OS) of children aged 3 years or older (EFS, 78% + 14%; OS, 89% ± 11%) were significantly better than those for younger patients (EFS, 11% ± 6%; OS, 17% ± 8%); EFS, P = .009 and OS, P = .0001. No other clinical characteristics were predictive of survival. Three of four patients 3 years or older with progressive disease were successfully rescued with ifosfamide, carboplatin, and etoposide therapy.

Conclusion

Children presenting with ATRT before the age of 3 years have a dismal prognosis. ATRT presenting in older patients can be cured using a combination of radiation and high-dose alkylating therapy. Older patients with relapsed ATRT can have salvage treatment using ICE chemotherapy.

Malignant rhabdoid tumor of the liver: case report and literature review

A case of malignant rhabdoid tumor (MRT) occurring as a primary hepatic neoplasm in a 12-month-old Japanese female infant is presented. The patient had a slight fever for 2 weeks and presented with a palpable mass in her left hypochondrial region. After admission, the hepatic artery was embolized due to intra-abdominal hemorrhage arising from the tumor. The patient received chemotherapy with cisplatin, cyclophosphamide and adriacin. Despite treatment, the patient developed dyspnea, pancytopenia and disseminated intravascular coagulation. Rupture of the tumor resulted in death within 3 weeks. A limited abdominal autopsy revealed that the liver weighed 1240 g and was occupied by multiple hemorrhagic and/or necrotic tumor nodules. Histologically, neoplastic cells had an abundant eosinophilic cytoplasm containing paranuclear inclusions, and vesicular nuclei with a centrally located prominent nucleolus. Ultrastructurally, the cytoplasmic inclusions were composed of whorled filaments measuring 10 nm. Immunohistochemically, almost all of the neoplastic cells were positive for vimentin and cytokeratins (CK) 8 and 18, some were positive for CK 7 and 19, while none were positive for CK 1, 10, 13-17 and 20. The tumor cells did not express desmin, myoglobin, and alpha-fetoprotein. We found 18 cases of MRT of the liver published in English language literature and then, adding the present case, we summarized the 19 cases. Hepatic MRT is an uncommon neoplasm. However, it should be considered in the differential diagnosis of an aggressive liver neoplasm in childhood.

Molecular pathogenesis of childhood brain tumors

In the last decade, the molecular biology revolution has advanced considerably. These advances have enhanced our understanding of the genetic underpinnings of human brain tumors in general, and pediatric brain tumors in particular. We now know that many pediatric brain tumors arise from disturbances in developmentally regulated signaling pathways. The medulloblastoma, a tumor in which the developmental Hedgehog and WNT pathways have gone awry, is a prime example of this. New techniques in genetic engineering have allowed for the creation of sophisticated mouse models of brain tumors that recapitulate the human disease. Many laboratories are now using cDNA microarrays to study the expression level of thousands of genes that may be aberrantly expressed in brain tumors when compared to normal control cells. In the next decade, the use of several new molecular techniques to establish brain tumor diagnoses will likely become standard tools in the diagnostics and treatment stratification of children with central nervous system tumors.

Central nervous system atypical teratoid/rhabdoid tumor: results of therapy in children enrolled in a registry

PURPOSE

Atypical teratoid/rhabdoid tumor (AT/RT) of the CNS is an extremely rare and aggressive tumor of early childhood. The poor outcome with conventional infant brain tumor therapy has resulted in a lack of clear treatment guidelines. A registry has been established to create an outcomes database and to facilitate biology studies for this tumor.

MATERIALS AND METHODS

A standardized data sheet was provided to treating physicians listing the reports that were to be sent to the registry for abstraction. Follow-up information was sought twice yearly.

RESULTS

Information was complete for 42 patients. Median age at diagnosis was 24 months. Nine patients (21%) had disseminated disease at diagnosis. Sixteen tumors were infratentorial; 26 were supratentorial. Twenty patients (48%) received a primary complete resection. Primary therapy included chemotherapy in all patients, radiotherapy in 13 patients (31%), stem-cell rescue in 13 patients (31%), and intrathecal chemotherapy in 16 patients (38%). Recurrent or progressive disease was reported in nine and 19 patients, respectively. Twenty-seven patients (64%) are dead of disease (3 to 62 months from diagnosis) and one patient died of toxicity. Fourteen patients (33%) show no evidence of disease (9.5 to 96 months from diagnosis). The median survival is 16.75 months and the median event-free survival is 10 months.

CONCLUSION

Aggressive therapy has prolonged the natural history in a subset of children. Prospective multi-institutional and national clinical trials designed specifically for AT/RT are needed. Enrollment onto the AT/RT registry should be continued.

Novel germ-line deletion ofSNF5/INI1/SMARCB1 gene in neonate presenting with congenital malignant rhabdoid tumor of kidney and brain primitive neuroectodermal tumor

We describe a neonate who had a rare tumor combination of a malignant rhabdoid tumor of the kidney (MRTK) and a brain primitive neuroectodermal tumor (PNET). Genetic alterations of the SNF5/INI1/SMARCB1 gene were investigated by PCR-single-strand conformation polymorphism (SSCP), loss of heterozygosity (LOH), sequence, and karyotyping analyses, and the gene expression level was determined by real-time quantitative RT-PCR analysis. PCR band signals of each exon of the hSNF5/INI1 were weak or nearly undetectable in both MRTK and PNET, whereas those of the corresponding normal kidney were clearly detected. Aberrantly migrating SSCP bands led to identification of a nucleotide change in intron 8. Although this was regarded as a polymorphism, only the changed nucleotide was observed in the normal kidney of the patient. Allelic states in the parents were heterozygous for the polymorphism in the father and homozygous for the normal sequence in the mother. Thus, it was evident that a substantial genetic part of the maternal normal allele including SNF5/INI1 was deleted as a de novo germ-line mutation. In both tumors, LOH at microsatellite loci on the long arm of chromosome 22 was evident, and expression of SNF5/INI1 mRNA was drastically decreased compared to that in control tissues (0.7-3.9 vs. 123.6-153.5). Deletion of a substantial genetic part demonstrated in our patient is the novel appearance of a germ-line deletion of the SNF5/INI1 gene. Additional large somatic deletions resulted in total inactivation of the gene in both tumors. Our patient provides evidence for an important role of SNF5/INI1germ-line mutation in predisposing patients to multiple rhabdoid tumors.

Expression of pericyte, mesangium and muscle markers in malignant rhabdoid tumor cell lines: differentiation-induction using 5-azacytidine

Malignant rhabdoid tumor (MRT) has been considered to have multiphenotypic diversity characteristics. Some MRTs exhibit a neural phenotype. However, it is still unclear whether MRT cells can display a skeletal muscle, smooth muscle or smooth muscle-like cell phenotype, like those of pericytes and mesangial cells. To determine if MRTs exhibit skeletal muscle cell or smooth muscle-like cell phenotypes, six MRT cell lines (TM87-16, STM91-01, TTC549, TTC642, YAM-RTK1 and TTC1240) were examined for markers of skeletal muscle (MyoD, myogenin, myf-5, myf-6, acetylcholine receptor-alpha, -beta and -gamma), smooth muscle (alpha-smooth muscle actin, SM-1 and SM22), and smooth muscle-like cells, such as pericytes (angiopoietin-1 and -2) and mesangial cells (megsin), using conventional RT-PCR, semi-quantitative PCR, western blotting and immunocytochemistry before and after differentiation-induction with 5-azacytidine. alpha-Smooth muscle actin and SM22 were detected in all six MRT cell lines, while MyoD and myf-5, crucial markers for skeletal myogenic determination, were not. The TM87-16 cell line expressed SM-1 and angiopoietin-1. TTC1240 also expressed angiopoietin-1. Interestingly, STM91-01 expressed megsin, a novel marker for mesangial cells, in addition to angiopoietin-1. Our results indicated that some MRTs exhibited smooth muscle and/or smooth muscle-like cell phenotypes and some renal MRTs might be of mesangial origin. Recently, smooth muscle and also smooth muscle-like cells have been considered to be of neuroectodermal origin. MRT can thus considered to belong to the category of primitive neuroectodermal tumors (PNETs) in the broad sense.

Molecular cytogenetics in solid tumors: laboratorial tool for diagnosis, prognosis, and therapy

The remarkable progress in the understanding of leukemogenesis was soundly sustained by methodological developments in the cytogenetic field. Nonrandom chromosomal abnormalities frequently associated with specific types of hematological disease play a major role in their diagnosis and have been demonstrated as independent prognostic indicators. Molecular pathways altered by chimeric or deregulated proteins as a consequence of chromosomal abnormalities have also significantly contributed to the development of targeted therapies, and cytogenetic assays are valuable for selecting patients for treatment and monitoring outcome. In solid tumors, significantly high levels of chromosome abnormalities have been detected, but distinction between critical and irrelevant events has been a major challenge. Consequently, the application of cytogenetic technology as diagnostic, prognostic, or therapeutic tools for these malignancies remains largely under appreciated. The emergence of molecular-based techniques such as fluorescence in situ hybridization was particularly useful for solid malignancies, and the spectrum of their application is rapidly expanding to improve efficiency and sensitivity in cancer prevention, diagnosis, prognosis, and therapy selection, alone or in combination with other diagnostic methods. This overview illustrates current uses and outlines potential applications for molecular cytogenetics in clinical oncology.

A unique occurrence of a cerebral atypical teratoid/rhabdoid tumor in an infant and a spinal canal primitive neuroectodermal tumor in her father

This report describes the clinical, pathological, immunohistochemical and genetic data of two rare malignant neoplasms of the central nervous system (CNS)--a cerebral atypical teratoid/rhabdoid tumor (AT/RT) in a 5-month-old girl and a spinal canal primitive neuroectodermal tumor (PNET) in her father. Despite aggressive treatment, both tumors were fatal, displaying extensive local recurrence and diffuse neoplastic dissemination. The paraffin-embedded tumor tissue samples were analyzed using a dual-color FISH with a locus specific LSI22q (BCR) probe. In the AT/RT tissue, a loss of BCR locus was observed in a significant proportion of the cells in contrast to the PNET specimen where the majority of nuclei did not reveal any loss of the BCR region. No mutations in exon 5 and no changes in SNP of intron 5 of hSNF/INI1 gene were found. In addition, analysis of loss of heterozygosity (LOH) was performed using a panel of 15 microsatellite markers of chromosome 22. No LOH were found in both tumor tissues. In both cases no constitutional mutations of gene TP53 were found. Analysis of the TP53 mutations in the tumor tissues revealed that the PNET, not the AT/RT tumor, was homozygous for a missense mutation at codon 175 (CGC ==> CAC). Thus, our findings emphasize the genetic differences between the two specimens and suggest that the occurrence of these two aggressive tumors of CNS in one family could be coincidental.

Renal cell carcinoma with rhabdoid features: an aggressive neoplasm

AIMS

Only a few reports on renal cell carcinoma with rhabdoid features have been published. This study was performed to investigate the clinicopathological characteristics of renal cell carcinomas with rhabdoid features.

METHODS AND RESULTS

Among 253 cases of renal cell carcinoma in adults, eight cases with rhabdoid features were detected. Rhabdoid areas ranged from 10% to 90% of each of the cases. Seven of the eight cases were TNM stage III or IV, and four of the eight cases died within 8 months of surgery. Immunohistochemically, the rhabdoid areas were positive for CAM 5.2 (4/8), AE1/AE3 (6/8), epithelial membrane antigen (6/8) and vimentin (8/8), and negative for myogenetic markers (0/8). The mean MIB-1 labelling index in the rhabdoid areas was higher than that in the definite carcinomatous areas. Ultrastructurally, perinuclear whorls of intermediate filaments were demonstrated in three of the eight cases using paraffin-embedded blocks.

CONCLUSIONS

The rhabdoid areas in renal cell carcinoma have histological, immunohistochemical and ultrastructural similarities to malignant rhabdoid tumours. Renal cell carcinoma with rhabdoid features is a highly aggressive neoplasm and its malignant behaviour may be due to the high cell-proliferative activity of the rhabdoid areas. Rhabdoid features in renal cell carcinoma may represent the endpoint of clonal evolution of renal cell carcinoma (especially in clear cell type cases).

Cell cycle arrest and repression of cyclin D1 transcription by INI1/hSNF5

INI1/hSNF5 is a component of the ATP-dependent chromatin remodeling hSWI/SNF complex and a tumor suppressor gene of aggressive pediatric atypical teratoid and malignant rhabdoid tumors (AT/RT). To understand the molecular mechanisms underlying its tumor suppressor function, we studied the effect of reintroduction of INI1/hSNF5 into AT/RT-derived cell lines such as MON that carry biallelic deletions of the INI1/hSNF5 locus. We demonstrate that expression of INI1/hSNF5 causes G(0)-G(1) arrest and flat cell formation in these cells. In addition, INI1/hSNF5 repressed transcription of cyclin D1 gene in MON, in a histone deacetylase (HDAC)-dependent manner. Chromatin immunoprecipitation studies revealed that INI1/hSNF5 was directly recruited to the cyclin D1 promoter and that its binding correlated with recruitment of HDAC1 and deacetylation of histones at the promoter. Analysis of INI1/hSNF5 truncations indicated that cyclin D1 repression and flat cell formation are tightly correlated. Coexpression of cyclin D1 from a heterologous promoter in MON was sufficient to eliminate the INI1-mediated flat cell formation and cell cycle arrest. Furthermore, cyclin D1 was overexpressed in AT/RT tumors. Our data suggest that one of the mechanisms by which INI1/hSNF5 exerts its tumor suppressor function is by mediating the cell cycle arrest due to the direct recruitment of HDAC activity to the cyclin D1 promoter thereby causing its repression and G(0)-G(1) arrest. Repression of cyclin D1 gene expression may serve as a useful strategy to treat AT/RT.

Treatment of metastatic rhabdoid tumor of the kidney

Metastatic rhabdoid tumor of the kidney (RTK) is a highly lethal malignancy; only one survivor with stage 4 disease has been reported. The authors reviewed the cases of two patients with metastatic RTK who had excellent responses to therapy. Both patients were treated with radiation therapy and alternating courses of ifosfamide, carboplatin, and etoposide (ICE) and vincristine, doxorubicin, and cyclophosphamide (VDC). The patients are without evidence of disease at 24 months and 12 months from the detection of metastasis. Alternating courses of ICE and VDC have activity against metastatic RTK. This combination of agents warrants prospective investigation in clinical trials.

Aberrations of the hSNF5/INI1 gene are restricted to malignant rhabdoid tumors or atypical teratoid/rhabdoid tumors in pediatric solid tumors

The hSNF5/INI1 gene, which encodes a subunit of the SWI/SNF family of chromatin-remodeling complexes and is located at 22q11.2, has been reported as a tumor suppressor gene inactivated in malignant rhabdoid tumors (MRTs). We analyzed this gene in varieties of pediatric solid tumors including MRTs, using the reverse transcription-polymerase chain reaction (PCR) and PCR-single strand conformation polymorphism method. We found 5 homozygous deletions, 2 truncated mutations, one missense mutation, and one silent mutation of the hSNF5/INI1 gene in 7 MRT cell lines, and one homozygous deletion, one microdeletion, one splicing acceptor site mutation, and one absence of expression in 7 fresh tumor tissues of MRT and atypical teratoid (AT)/rhabdoid tumors (RTs). Homozygous deletions were also found in one (KYM-1) of 8 rhabdomyosarcoma (RMS) cell lines. To investigate characteristics of the KYM-1 cell line, we have established KYM-1 tumors in nude mice into which KYM-1 cells were transplanted. Notably, we found that MyoD1, known as a marker for RMS, was not expressed in the KYM-1 cell line as well as MRT cell lines and fresh tumors. Histopathologic, cytogenetic, and molecular studies of the KYM-1 cell line and KYM-1 tumors in nude mice have revealed that this RMS cell line should be MRT rather than RMS. RMS-carrying aberrations of the hSNF5/INI1 gene should be reevaluated. No aberrations of this gene were found in the other 34 cell lines or 80 fresh tumor specimens except the single nucleotide polymorphisms in the 3' noncoding region. These results suggest that alterations of the hSNF5/INI1 gene were restricted to MRTs or AT/RTs in pediatric solid tumors.