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

Epigenetic regulation in cancer

Epigenetic modifications are defined as heritable changes in gene activity that do not involve changes in the underlying DNA sequence. The oncogenic process is driven by the accumulation of alterations that impact genome's structure and function. Genetic mutations, which directly disrupt the DNA sequence, are complemented by epigenetic modifications that modulate gene expression, thereby facilitating the acquisition of malignant characteristics. Principals among these epigenetic changes are shifts in DNA methylation and histone mark patterns, which promote tumor development and metastasis. Notably, the reversible nature of epigenetic alterations, as opposed to the permanence of genetic changes, positions the epigenetic machinery as a prime target in the discovery of novel therapeutics. Our review delves into the complexities of epigenetic regulation, exploring its profound effects on tumor initiation, metastatic behavior, metabolic pathways, and the tumor microenvironment. We place a particular emphasis on the dysregulation at each level of epigenetic modulation, including but not limited to, the aberrations in enzymes responsible for DNA methylation and histone modification, subunit loss or fusions in chromatin remodeling complexes, and the disturbances in higher-order chromatin structure. Finally, we also evaluate therapeutic approaches that leverage the growing understanding of chromatin dysregulation, offering new avenues for cancer treatment.

Sellar Suprasellar Surprise: A Rare Case of Atypical Teratoid/Rhabdoid Tumor in an Infant

We present a case of a 10-month-old male infant who initially presented with polyuria, polydipsia, drowsiness, and fever. Neuroimaging using non-contrast computed tomography (NCCT) demonstrated obstructive hydrocephalus associated with a suprasellar mass, for which emergency neurosurgical intervention was performed with right parietal medium pressure ventriculoperitoneal (MPVP) shunting. For fever, no cause was found with sterile cerebrospinal fluid (CSF) analysis, and empirical antibiotics were administered. The patient exhibited polyuria with hypernatremia and was diagnosed with arginine vasopressin (AVP) deficiency, further complicated by visual impairment due to left optic atrophy. Hormonal workup revealed secondary hypothyroidism and hypocortisolism. Imaging by contrast-enhanced magnetic resonance imaging (CEMR) revealed a lobulated solid-cystic suprasellar mass with flow void, suggestive of adamantinomatous craniopharyngioma initially. However, despite multiple neurosurgical interventions, the patient's condition deteriorated with recurrent fever and seizures, leading to a revision of ventriculoperitoneal shunts. Repeat CEMR showed an increase in the size of the lesion with spinal leptomeningeal metastasis, suggesting a different pathology. Transventricular biopsy confirmed an atypical teratoid and rhabdoid tumor (AT/RT), World Health Organization Classification of Tumors of the Central Nervous System (CNS WHO) grade 4, characterized by diffuse growth pattern, moderate nuclear pleomorphism, clear cytoplasm, and prominent nucleoli. Immunohistochemistry revealed positive vimentin staining and loss of integrase interactor 1 (INI1) expression, consistent with AT/RT. The patient's parents were counseled on the need for multimodal management, including surgery and chemotherapy. However, due to socioeconomic constraints and a guarded prognosis, they chose to leave against medical advice. This case illustrates the diagnostic challenges in distinguishing AT/RT from other suprasellar masses and emphasizes the importance of a multidisciplinary approach in managing complex pediatric cases.

Targeting Chromatin-Remodeling Factors in Cancer Cells: Promising Molecules in Cancer Therapy

ATP-dependent chromatin-remodeling complexes can reorganize and remodel chromatin and thereby act as important regulator in various cellular processes. Based on considerable studies over the past two decades, it has been confirmed that the abnormal function of chromatin remodeling plays a pivotal role in genome reprogramming for oncogenesis in cancer development and/or resistance to cancer therapy. Recently, exciting progress has been made in the identification of genetic alteration in the genes encoding the chromatin-remodeling complexes associated with tumorigenesis, as well as in our understanding of chromatin-remodeling mechanisms in cancer biology. Here, we present preclinical evidence explaining the signaling mechanisms involving the chromatin-remodeling misregulation-induced cancer cellular processes, including DNA damage signaling, metastasis, angiogenesis, immune signaling, etc. However, even though the cumulative evidence in this field provides promising emerging molecules for therapeutic explorations in cancer, more research is needed to assess the clinical roles of these genetic cancer targets.

SWI/SNF Complex-deficient Undifferentiated Carcinoma of the Gastrointestinal Tract: Clinicopathologic Study of 30 Cases With an Emphasis on Variable Morphology, Immune Features, and the Prognostic Significance of Different SMARCA4 and SMARCA2 Subunit Deficiencies

Undifferentiated carcinoma of the gastrointestinal tract has variable rhabdoid features. Expression of switch/sucrose nonfermenting (SWI/SNF) complex subunits is reportedly lost in a portion of cases; however, the prognostic significance of this loss remains unknown. Herein, 30 undifferentiated carcinoma cases were assessed for the expression of 4 SWI/SNF complex subunits (SMARCB1, SMARCA2, SMARCA4, and ARID1A). Tumor origin sites comprised stomach (40.0%), large intestine (20.0%), small intestine (16.7%), lower esophagus and stomach fundus (13.3%), ileocecal junction (3.3%), rectum (3.3%), and pancreas (3.3%). The tumors were composed of epithelioid neoplastic cells arranged in diffuse solid or discohesive sheets, nests, cords, poor cohesive pseudoglandular, and trabecular patterns. Rhabdoid tumor cells were identified in 66.7% (20/30) of cases. In total, 29/30 (96.7%) showed complete loss of at least 1 SWI/SNF subunit: SMARCA4-/SMARCA2- (11), isolated SMARCA4- (2), SMARCA4-/SMARCA2 unknown (6), isolated SMARCA2- (7), SMARCA2-/ARID1A- (1), and isolated ARID1A- (2). Negative or decreased expression (≤10% positive) of pan-cytokeratin was observed in 58.6% (17/29) of cases. In addition, 66.7% (20/30) of patients were late-stage (III or IV), and 65.2% (15/23) of stage IIB to IV patients succumbed to the disease at a mean clinical follow-up of 12.7 months. Specifically, patients with loss of SMARCA4 expression had the worst overall survival (P=0.028) and disease-free survival (P=0.006) rates, compared with those with SMARCA4 expression. The loss or decreased expression of epithelial markers is thus common in SWI/SNF complex-deficient undifferentiated carcinoma of the gastrointestinal tract, and loss of SMARCA4 correlates with poor prognosis.

Attenuated expression of SNF5 facilitates progression of bladder cancer via STAT3 activation

BACKGROUND

SWI/SNF, a well-known ATP-dependent chromatin-remodeling complex, plays an essential role in several biological processes. SNF5, the core subunit of the SWI/SNF remodeling complex, inactivated in 95% of malignant rhabdoid tumors (MRT), highlighting its significance in tumorigenesis. However, the role of SNF5 in bladder cancer (BC) remains unknown. In this study, we aimed to investigate the function and potential clinical applicability of SNF5 in BC.

METHODS

Data from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) and Cancer Cell Line Encyclopedia (CCLE) databases were used to evaluate the clinical significance of SNF5 in BC. We performed Gene Set Enrichment Analysis (GSEA) and functional assays to investigate the role of SNF5 in BC. Genomics of Drug Sensitivity in Cancer (GDSC) and drug-susceptibility tests were performed to identify the potential value of SNF5 in the treatment of BC.

RESULTS

Low SNF5 expression conferred a poor prognosis and was significantly associated with the N-stage in BC. ROC curves indicated that SNF5 could distinguish BC from the normal tissues. In vitro and in vivo functional assays demonstrated that attenuated SNF5 expression could promote cell proliferation and enhance migration by STAT3 activation. We imputed that low SNF5 expression could confer greater resistance against conventional first-line drugs, including cisplatin and gemcitabine in BC. GDSC and drug-resistance assays suggested that low SNF5 expression renders T24 and 5637 cells high sensitivity to EGFR inhibitor gefitinib, and combination of EZH2 inhibitor GSK126 and cisplatin.

CONCLUSIONS

To the best of our knowledge, the present study, for the first time, showed that low SNF5 expression could promote cell proliferation and migration by activating STAT3 and confer poor prognosis in BC. Importantly, SNF5 expression may be a promising candidate for identifying BC patients who could benefit from EGFR-targeted chemotherapy or cisplatin in combination with EZH2 inhibitor treatment regimens.

Myxoepithelioid tumour with chordoid features: a clinicopathological, immunohistochemical and genetic study of 14 cases of SMARCB1/INI1-deficient soft-tissue neoplasm

AIMS

Complete loss of SMARCB1/INI1 in soft-tissue tumours such as malignant rhabdoid tumour, epithelioid sarcoma, myoepithelial tumour of soft tissue and extraskeletal myxoid chondrosarcoma is often associated with high-grade malignancy and poor prognosis. The diagnosis is sometimes challenging, owing to histological similarities, so careful differential diagnosis is required. Therefore, soft-tissue tumours with complete SMARCB1/INI1 loss could potentially include an unknown entity.

METHODS AND RESULTS

We analysed 160 cases of SMARCB1/INI1-deficient soft-tissue tumour, and found 14 cases that were not classifiable into already existing categories and had common clinical and histological features. These involved two male and 12 female patients, ranging in age from 20 years to 61 years. The tumours were located in the the puboinguinal region (n = 13) and pelvic cavity (n = 1). Histologically, the tumours showed relatively uniform epithelioid to spindle-shaped cells with myxoid stroma. All tumours showed immunoreactivity for brachyury, epithelial membrane antigen, and progesterone receptor, and 12 of 14 cases did so for oestrogen receptor. Variable positive staining for α-smooth muscle actin, S100 and glial fibrillary acidic protein (GFAP) was seen. NR4A3 and EWSR1 gene rearrangements were not detected in 13 and 11 examined cases, respectively. Clinical follow-up data for the 14 patients showed that 13 were alive without disease and one had been lost to follow-up; four patients developed local recurrence and/or metastases.

CONCLUSION

The designation 'myxoepithelioid tumour with choroid features' (METC) was proposed as a tumour with intermediate malignancy controllable with appropriate treatment, including the entity of myoepithelioma-like tumour of the vulvar region. METC represents a novel and independent subset that is histologically, biologically and clinically distinct from already existing SMARCB1/INI1-deficient soft-tissue tumours.

Clinical and Molecular Differentiation Between Malignant Rhabdoid Tumor of the Kidney and Normal Tissue: A Two-Case Report

BACKGROUND

Malignant rhabdoid tumor of the kidney (MRTK) is a rare type of tumor that lacks typical clinical manifestations. Herein, we presented clinical data of 2 children with MRTK. In addition, we used a high-throughput RNA-sequencing (RNA-seq), GO analysis, and KEGG signaling pathway analysis to examine gene expression differences at the transcripts level between 2 patients with MRTK and 3 patients with non-tumor diseases without other symptoms.

CASE REPORT

Preoperative B-scan ultrasonography and computed tomography (CT) examination in 2 cases suggested nephroblastoma. Both patients were treated with radical nephrectomy. After the operation, MRTK was confirmed by pathological examination. Child 1 and Child 2 then received 7 courses and 12 courses of regular chemotherapy, respectively. Child 1 was followed up for 2 years, and Child 2 for 3.1 years without showing symptoms. RNA-seq results showed 2203 differential genes (DEGs) in the kidney tissue of children with MRTK compared to normal tissue (p <0.01). GO analysis suggested that most DEGs participate in protein binding. KEGG results showed that the DEGs were mainly involved in the PI3K-Akt signaling pathway and microRNA-related proteins.

CONCLUSION

The PI3K-Akt signaling pathway and microRNA-related proteins as targets have extremely high potential value for the diagnosis and treatment of MRTK.

A Coil-to-Helix Transition Serves as a Binding Motif for hSNF5 and BAF155 Interaction

Human SNF5 and BAF155 constitute the core subunit of multi-protein SWI/SNF chromatin-remodeling complexes that are required for ATP-dependent nucleosome mobility and transcriptional control. Human SNF5 (hSNF5) utilizes its repeat 1 (RPT1) domain to associate with the SWIRM domain of BAF155. Here, we employed X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, and various biophysical methods in order to investigate the detailed binding mechanism between hSNF5 and BAF155. Multi-angle light scattering data clearly indicate that hSNF5171-258 and BAF155SWIRM are both monomeric in solution and they form a heterodimer. NMR data and crystal structure of the hSNF5171-258/BAF155SWIRM complex further reveal a unique binding interface, which involves a coil-to-helix transition upon protein binding. The newly formed αN helix of hSNF5171-258 interacts with the β2-α1 loop of hSNF5 via hydrogen bonds and it also displays a hydrophobic interaction with BAF155SWIRM. Therefore, the N-terminal region of hSNF5171-258 plays an important role in tumorigenesis and our data will provide a structural clue for the pathogenesis of Rhabdoid tumors and malignant melanomas that originate from mutations in the N-terminal loop region of hSNF5.

Atypical Teratoid/Rhabdoid Tumor of the Sellar Region in an Adult With Long Survival: Case Report and Review of the Literature

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly malignant central nervous system neoplasm usually diagnosed in young children, although it can occur in adults. Prognosis for AT/RT is poor, with a median survival of 10 - 11 months. We report a rare case of adult sellar and suprasellar AT/RT in a 36-year-old female patient. She was treated with multi-modalities including surgery, chemotherapy and radiation. She markedly improved following treatment with no recurrence in 3 years follow-up. To our knowledge, this is the 11th case of an adult-onset AT/RT in the sellar or suprasellar region with favorable long-term outcome.

The molecular pathogenesis of schwannomatosis, a paradigm for the co-involvement of multiple tumour suppressor genes in tumorigenesis

Schwannomatosis is characterized by the predisposition to develop multiple schwannomas and, less commonly, meningiomas. Despite the clinical overlap with neurofibromatosis type 2 (NF2), schwannomatosis is not caused by germline NF2 gene mutations. Instead, germline mutations of either the SMARCB1 or LZTR1 tumour suppressor genes have been identified in 86% of familial and 40% of sporadic schwannomatosis patients. In contrast to patients with rhabdoid tumours, which are due to complete loss-of-function SMARCB1 mutations, individuals with schwannomatosis harbour predominantly hypomorphic SMARCB1 mutations which give rise to the synthesis of mutant proteins with residual function that do not cause rhabdoid tumours. Although biallelic mutations of SMARCB1 or LZTR1 have been detected in the tumours of patients with schwannomatosis, the classical two-hit model of tumorigenesis is insufficient to account for schwannoma growth, since NF2 is also frequently inactivated in these tumours. Consequently, tumorigenesis in schwannomatosis must involve the mutation of at least two different tumour suppressor genes, an occurrence frequently mediated by loss of heterozygosity of large parts of chromosome 22q harbouring not only SMARCB1 and LZTR1 but also NF2. Thus, schwannomatosis is paradigmatic for a tumour predisposition syndrome caused by the concomitant mutational inactivation of two or more tumour suppressor genes. This review provides an overview of current models of tumorigenesis and mutational patterns underlying schwannomatosis that will ultimately help to explain the complex clinical presentation of this rare disease.

Cancer Stem Cells: Dynamic Entities in an Ever-Evolving Paradigm

The cancer stem cell (CSC) hypothesis postulates that there is a hierarchy of cellular differentiation within cancers and that the bulk population of tumor cells is derived from a relatively small population of multi-potent neoplastic stem-like cells (CSCs). This tumor-initiating cell population plays an important role in maintaining tumor growth through their unlimited self-renewal, therapeutic resistance, and capacity to propagate tumors through asymmetric cell division. Recent findings from multiple laboratories show that cancer progenitor cells have the capacity to de-differentiate and acquire a stem-like phenotype in response to either genetic manipulation or environmental cues. These findings suggest that CSCs and relatively differentiated progenitors coexist in dynamic equilibrium and are subject to bidirectional conversion. In this review, we discuss emerging concepts regarding the stem-like phenotype, its acquisition by cancer progenitor cells, and the molecular mechanisms involved. Understanding the dynamic equilibrium between CSCs and cancer progenitor cells is critical for the development of novel therapeutic strategies that focus on depleting tumors of their tumor-propagating cell population.

Genome-wide approach to identify second gene targets for malignant rhabdoid tumors using high-density oligonucleotide microarrays

Malignant rhabdoid tumor (MRT) is a rare and highly lethal cancer that mainly affects infants and young children. The majority of MRT are characterized by loss of function of SMARCB1 on chromosome 22q11.2. However, little is known about genetic changes other than SMARCB1 alterations that are responsible for the development and/or progression of MRT. To explore additional gene targets in MRT, we analyzed 21 MRT specimens (12 fresh tumors and 9 MRT-derived cell lines) using high-density single nucleotide polymorphism genotyping microarrays. Although MRT genomes are characterized by common 22q11.2 deletions, affecting the SMARCB1 locus with a frequency of 95.2% (20/21 specimens), other genetic changes have been less frequent. Of the 20 specimens with deletions of 22q11.2, eight specimens showed uniparental disomy of the SMARCB1 locus with homozygous deletions or gene mutations. High-resolution analysis also disclosed the recurrent hemizygous/homozygous deletions of 7q35–q36.1, involving the CNTNAP2 locus in three specimens. Mutations analysis of CNTNAP2 showed a novel R157C missense mutation in a primary case, and methylation analysis showed recurrent hypermethylation of CNTNAP2 in three of nine cell lines. These results demonstrated that CNTNAP2 is one of the additional gene targets, other than SMARCB1, in MRT.

Sella turcica atypical teratoid/rhabdoid tumor complicated with lung metastasis in an adult female

Here we present the case of a 60-year-old woman with a rare sellar region atypical teratoid/rhabdoid tumor (AT/RT), complicated by lung metastasis and treated with neurosurgery, radiotherapy, and chemotherapy. The patient had recurrent headache associated with left cavernous sinus syndrome after a previous endonasal transsphenoidal resection for a presumptive pituitary macroadenoma. Pituitary magnetic resonance imaging showed a tumor regrowth in the original location with a haemorrhagic component involving the left cavernous sinus. A near complete transsphenoidal resection of the sellar mass was performed followed by 3 months of stereotactic radiotherapy. Because of a worsening of the general clinical conditions, respiratory failure, and asthenia, the patient underwent a contrast enhanced computer tomography of the whole body which showed the presence of lung metastasis. The histopathological diagnosis on samples from pituitary and lung tissues was AT/RT. The patient survived 30 months after diagnosis regardless chemotherapy. In the adult, the AT/RT should be considered as a possible rare, aggressive, and malignant neoplasm localized in the sella turcica.

The histone methyltransferase SUV39H1 suppresses embryonal rhabdomyosarcoma formation in zebrafish

Epigenetics, or the reversible and heritable marks of gene regulation not including DNA sequence, encompasses chromatin modifications on both the DNA and histones and is as important as the DNA sequence itself. Chromatin-modifying factors are playing an increasingly important role in tumorigenesis, particularly among pediatric rhabdomyosarcomas (RMS), revealing potential novel therapeutic targets. We performed an overexpression screen of chromatin-modifying factors in a KRAS(G12D)-driven zebrafish model for RMS. Here, we describe the identification of a histone H3 lysine 9 histone methyltransferase, SUV39H1, as a suppressor of embryonal RMS formation in zebrafish. This suppression is specific to the histone methyltransferase activity of SUV39H1, as point mutations in the SET domain lacked the effect. SUV39H1-overexpressing and control tumors have a similar proliferation rate, muscle differentiation state, and tumor growth rate. Strikingly, SUV39H1-overexpressing fish initiate fewer tumors, which results in the observed suppressive phenotype. We demonstrate that the delayed tumor onset occurs between 5 and 7 days post fertilization. Gene expression profiling at these stages revealed that in the context of KRAS(G12D) overexpression, SUV39H1 may suppress cell cycle progression. Our studies provide evidence for the role of SUV39H1 as a tumor suppressor.

Proteomic and bioinformatic analysis of mammalian SWI/SNF complexes identifies extensive roles in human malignancy

Subunits of mammalian SWI/SNF (mSWI/SNF or BAF) complexes have recently been implicated as tumor suppressors in human malignancies. To understand the full extent of their involvement, we conducted a proteomic analysis of endogenous mSWI/SNF complexes, which identified several new dedicated, stable subunits not found in yeast SWI/SNF complexes, including BCL7A, BCL7B and BCL7C, BCL11A and BCL11B, BRD9 and SS18. Incorporating these new members, we determined mSWI/SNF subunit mutation frequency in exome and whole-genome sequencing studies of primary human tumors. Notably, mSWI/SNF subunits are mutated in 19.6% of all human tumors reported in 44 studies. Our analysis suggests that specific subunits protect against cancer in specific tissues. In addition, mutations affecting more than one subunit, defined here as compound heterozygosity, are prevalent in certain cancers. Our studies demonstrate that mSWI/SNF is the most frequently mutated chromatin-regulatory complex (CRC) in human cancer, exhibiting a broad mutation pattern, similar to that of TP53. Thus, proper functioning of polymorphic BAF complexes may constitute a major mechanism of tumor suppression.

The mutational landscape of chromatin regulatory factors across 4,623 tumor samples

BACKGROUND

Chromatin regulatory factors are emerging as important genes in cancer development and are regarded as interesting candidates for novel targets for cancer treatment. However, we lack a comprehensive understanding of the role of this group of genes in different cancer types.

RESULTS

We have analyzed 4,623 tumor samples from thirteen anatomical sites to determine which chromatin regulatory factors are candidate drivers in these different sites. We identify 34 chromatin regulatory factors that are likely drivers in tumors from at least one site, all with relatively low mutational frequency. We also analyze the relative importance of mutations in this group of genes for the development of tumorigenesis in each site, and indifferent tumor types from the same site.

CONCLUSIONS

We find that, although tumors from all thirteen sites show mutations in likely driver chromatin regulatory factors, these are more prevalent in tumors arising from certain tissues. With the exception of hematopoietic, liver and kidney tumors, as a median, the mutated factors are less than one fifth of all mutated drivers across all sites analyzed. We also show that mutations in two of these genes, MLL and EP300, correlate with broad expression changes across cancer cell lines, thus presenting at least one mechanism through which these mutations could contribute to tumorigenesis in cells of the corresponding tissues.

Ossifying fibromyxoid tumor of soft parts: a clinicopathologic, proteomic, and genomic study

Ossifying fibromyxoid tumor (OFMTs) of soft parts is a rare soft tissue and bone tumor of borderline malignancy displaying an uncertain line of differentiation. The existence of fully malignant OFMT is controversial. To better understand the natural history and line of differentiation taken by OFMT, we studied 46 cases by light microscopic, immunohistochemical (IHC), genomic, proteomic, and fluorescence in situ hybridization (FISH) methods. Cases were classified according to the 2003 Folpe and Weiss system. Clinical and follow-up information was obtained. IHC for S-100 protein, desmin, epithelial membrane antigen (EMA), cytokeratins, smooth muscle actin (SMA), INI-1, neurofilament protein (NFP), CD56d excitatory amino acid transporter-4 (EAAT4), and MUC4 was performed on formalin-fixed, paraffin-embedded (FFPE) tissues. Gene expression profiling and proteomic studies were conducted on FFPE tissues from 13 and 5 cases, respectively. FISH for INI-1 was performed on 10 cases. The 46 tumors arose in 29 men and 17 women (median age, 52 y; range 39 to 63 y) and involved the proximal (N=17) and distal extremities (N=13), head and neck (N=9), and trunk (N=5). Median tumor size was 5.4 cm (range, 1.0 to 21.0 cm). Cases were classified as typical OFMT (26 of 46, 57%), atypical OFMT (5 of 46, 11%), and malignant OFMT (15 of 46 cases, 32%). Clinical follow-up (27 cases, median 55 months' duration) showed all patients with typical and atypical OFMT to be alive without disease. Adverse events, including 3 local recurrences, 3 metastases, and 3 deaths, were seen only in malignant OFMT. IHC results were as follows: S-100 protein (30 of 41, 73%), desmin (15 of 39, 38%), cytokeratin (4 of 35, 11%), EMA (5 of 32, 16%), SMA (2 of 34, 6%), INI-1 (lost in mosaic pattern in 14 of 19, 74%), EAAT4 (31 of 39, 80%), MUC4 (3 of 14, 21%), NFP (8 of 10, 80%) and CD56 (6 of 14, 43%). Gene expression profiling showed typical and malignant OFMTs to cluster together, distinct from schwannian tumors. Proteomic study showed expression of various collagens, S-100 protein, and neuron-related proteins. FISH showed INI-1 deletion in 5 of 7 (71%) cases. We conclude that malignant OFMTs exist and may be recognized by the previously proposed criteria of Folpe and Weiss. Expression of neuron-related markers, in addition to Schwann cell and cartilage-associated markers, suggests a "scrambled" phenotype in OFMTs. Loss of INI-1 or other genes on 22q is likely important in the pathogenesis of these rare tumors.

A decade of exploring the cancer epigenome - biological and translational implications

The past decade has highlighted the central role of epigenetic processes in cancer causation, progression and treatment. Next-generation sequencing is providing a window for visualizing the human epigenome and how it is altered in cancer. This view provides many surprises, including linking epigenetic abnormalities to mutations in genes that control DNA methylation, the packaging and the function of DNA in chromatin, and metabolism. Epigenetic alterations are leading candidates for the development of specific markers for cancer detection, diagnosis and prognosis. The enzymatic processes that control the epigenome present new opportunities for deriving therapeutic strategies designed to reverse transcriptional abnormalities that are inherent to the cancer epigenome.

Fetal and placental malignancies: prenatal diagnosis and management

Fetal and placental malignancies are rare complications during pregnancy, but when they occur they may present significant challenges for the perinatology team. Owing to their rarity, there is limited information on many of these entities, with much data derived from individual case reports or small case series. Prenatal diagnosis of these entities is rare and inconsistent, usually in the form of isolated case reports. In the majority of fetal tumors, prenatal features are those of a mass lesion, with or without other non-specific features of fetal compromise such as polyhydramnios, fetal hydrops or intrauterine death, the final diagnosis in most cases being based on postnatal pathological examination.Expectant management is almost always indicated antenatally, with serial ultrasound examinations performed to detect rapid enlargement, metastasis or secondary fetal complications, such as non-immune hydrops, which may require intervention. Delivery should be planned in a specialist center in conjunction with pediatric surgeons and oncologists to allow appropriate neonatal management. Placental malignancy is most commonly in the form of gestatational trophoblastic disease, which requires assessment and management in specialist centers.

Induction of autophagy in malignant rhabdoid tumor cells by the histone deacetylase inhibitor FK228 through AIF translocation

Malignant rhabdoid tumors (MRT) exhibit a very poor prognosis because of their resistance to chemotherapeutic agents and new therapies are needed for the treatment of this cancer. Here, we show that the histone deacetylase (HDAC) inhibitor FK228 (depsipeptide) has an antitumor effect on MRT cells both in vitro and in vivo. FK228 is a unique cyclic peptide and is among the most potent inhibitors of both Class I and Class II HDACs. FK228 inhibited proliferation and induced apoptosis in all MRT cell lines tested. Preincubation with the pancaspase inhibitor zVAD-fmk did not completely rescue FK228-induced cell death, although it did inhibit apoptosis. Transmission electron microscopy (TEM) showed that FK228 could stimulate MRT cells to undergo apoptosis, necrosis or autophagy. FK228 converted unconjugated microtubule-associated protein light chain 3 (LC3-I) to conjugated light chain 3 (LC3-II) and induced localization of LC3 to autophagosomes. Apoptosis inducing factor (AIF), which plays a role in caspase-independent cell death, translocated to the nucleus in response to FK228 treatment. Moreover, small interfering RNA (siRNA) targeting of AIF prevented the morphological changes associated with autophagy and redistribution of LC3 to autophagosomes. Disrupting autophagy with chloroquine treatment enhanced FK228-induced cell death. In vivo, FK228 caused a reduction in tumor size and induced autophagy in tumor tissues. Using immunoelectron microscopy, we confirmed AIF translocation into the nucleus of FK228-induced autophagic cells in vivo. Thus, FK228 is a novel candidate for an antitumor agent for MRT cells.

Evidence of a four-hit mechanism involving SMARCB1 and NF2 in schwannomatosis-associated schwannomas

Schwannomatosis is characterized by the onset of multiple intracranial, spinal, or peripheral schwannomas, without involvement of the vestibular nerve, which is instead pathognomonic of neurofibromatosis type 2 (NF2). Recently, a schwannomatosis family with a germline mutation of the SMARCB1 gene on chromosome 22 has been described. We report on the molecular analysis of the SMARCB1 and NF2 genes in a series of 21 patients with schwannomatosis and in eight schwannomatosis-associated tumors from four different patients. A novel germline SMARCB1 mutation was found in one patient; inactivating somatic mutations of NF2, associated with loss of heterozygosity (LOH) of 22q, were found in two schwannomas of this patient. This is the second report of a germline SMARCB1 mutation in patients affected by schwannomatosis and the first report of SMARCB1 mutations associated with somatic NF2 mutations in schwannomatosis-associated tumors. The latter observation suggests that a four-hit mechanism involving the SMARCB1 and NF2 genes may be implicated in schwannomatosis-related tumorigenesis.

Identification of side population cells (stem-like cell population) in pediatric solid tumor cell lines

PURPOSE

Recent evidence has supported the cancer stem cell theory that cancer contains a small number of cancer stem cells (CSC) as a reservoir of cancer cells. Only the CSC, but not most of the remaining constituent cancer cells, are thought to be responsible for tumorigenesis, progression, and metastasis as well as cancer relapse, suggesting that the CSC should be targeted to eradicate the cancer. Side population (SP) cells isolated by fluorescence-activated cell sorting (FACS) using Hoechst dye are known to be enriched in stem cells in various normal tissues as well as cancers. The authors investigated whether such stem-like SP cells may exist in pediatric solid tumors (PSTs).

MATERIALS AND METHODS

Sixteen pediatric tumor cell lines including 7 neuroblastomas, 4 rhabdomyosarcomas, and 5 Ewing's sarcomas were used for FACS analysis. Analysis of SP cells based on the exclusion of the DNA binding dye, Hoechst 33342, with and without verapamil using FACS was performed.

RESULTS

One Ewing's sarcoma cell line did not show an SP fraction, and only a small fraction of SP cells (0.12%-14.6%) was detected in the other 15 cell lines. These SP cells were all sensitive to verapamil.

CONCLUSIONS

This study suggested that most PSTs would contain a small fraction of SP cells (possible stem-like population). Targeting the CSC will provide a novel treatment strategy to eradicate refractory PSTs.

Malignant rhabdoid tumor mimicking hepatoblastoma: a case report and literature review

Hepatoblastoma accounts for the vast majority of malignant primary liver tumors in infancy. In contrast, rhabdoid tumors arising in the liver are extremely rare, but they can share clinical and histologic features with hepatoblastoma and can create diagnostic confusion, especially when one is dealing with small biopsies. In this case report we demonstrate that immunohistochemical and molecular techniques can identify the characteristic loss of INI1 and facilitate making the correct diagnosis of primary hepatic malignant rhabdoid tumor. Important similarities and differences between hepatoblastoma and rhabdoid tumors are reviewed, and suggestions are offered to help distinguish these 2 tumor types.

Mutation and expression analyses of the MET and CDKN2A genes in rhabdomyosarcoma with emphasis on MET overexpression

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of childhood. The simultaneous loss of Ink4a/Arf function and disruption of Met signaling in Ink4a/Arf-/- mice transgenic for hepatocyte growth factor/scatter factor (HGF/SF) induces RMS with extremely high penetrance and short latency. To address the roles of MET and CDKN2A (p16INK4A/p14ARF) in human RMS, we performed mutational analyses in 39 samples of RMS by PCR-SSCP. No mutations were detected in exons 14-21 of MET whereas a nonsense mutation at codon 80 of p16(INK4A) was identified in an alveolar RMS cell line. We also quantified the relative expression levels and DNA copy numbers of these genes in seven cell lines and 17 fresh tumors by real-time quantitative PCR. Expression of MET was detected in all samples; however, more than 10-fold difference was found in the samples with higher or lower expression level, despite a normal DNA copy number. The protein expression level was consistent with that of mRNA, and in cell lines with a higher expression level, MET was constitutively activated. Notably, the expression level of MET was significantly higher in patients who died (P = 0.02), in patients with stage IV (P = 0.04), as well as in patients with PAX3-FKHR chimeric transcript (P = 0.04). On the other hand, reduced or absent expression of p16INK4A and/or p14(ARF) showed no significant correlation with the clinicopathological parameters, except for the age at diagnosis. Our data suggest that MET plays a role in the progression of RMS.

Mutations of the PTPN11 and RAS genes in rhabdomyosarcoma and pediatric hematological malignancies

PTPN11 has been identified as a causative gene in Noonan syndrome (NS), responsible for about 50% of cases of NS. Given the association between NS and an increased risk of some malignancies, notably leukemia and probably some solid tumors including neuroblastoma (NB) and rhabdomyosarcoma (RMS), recent studies have reported that gain-of-function somatic mutations in PTPN11 occur in some hematological malignancies, especially de novo juvenile myelomonocytic leukemia (JMML) and in some solid tumors such as NB, although at a low frequency. In a screen for mutations of PTPN11 in 7 cell lines and 30 fresh tumors of RMS and in 25 cell lines and 40 fresh tumors of NB, we identified a missense mutation (A72T) in an embryonal RMS patient. In the RMS samples, we also detected mutations of NRAS in 1 cell line and 1 patient; both mutations were in embryonal RMSs and had no PTPN11 mutations. No mutations of PTPN11 were detected in NB. In 95 leukemia cell lines and 261 fresh leukemia samples including 22 JMMLs, 9 kinds of missense mutations were detected in 17 leukemia samples, which included 11 (50.0%) mutations in JMML samples and lower frequencies in other hematological malignancies. Furthermore, we identified 4 (18.2%) NRAS mutations and 1 (4.5%) KRAS mutation in 5 JMML samples, 1 of which had a concomitant PTPN11 mutation. Our data suggest that mutations of PTPN11 as well as RAS play a role in the pathogenesis of not only myeloid hematological malignancies but also a subset of RMS malignancies.

Mesothelioma with rhabdoid features: an ultrastructural and immunohistochemical study of 10 cases

Mesotheliomas with rhabdoid morphology are rare and only two individual case reports have been documented in the literature. This author reports a series of 10 cases of mesotheliomas with rhabdoid features, nine of which originated in the pleura and one in the peritoneum. Eight of the patients were men and two were women. Six patients had a history of asbestos exposure. Histologically, seven of the mesotheliomas were epithelioid, two sarcomatoid, and one biphasic. The proportion of the rhabdoid cells seen in these cases constituted 15-75% of the individual tumors. Cytoplasmic staining in the rhabdoid cells was seen for pan-keratin and vimentin in all 10 cases, for keratin 7 in eight of eight, for calretinin in nine of 10, and for keratin 5/6 in seven of nine. Nuclear positivity for WT1 was observed in the rhabdoid cells of four of seven cases and membranous reactivity for mesothelin in four of six, and for podoplanin in two of six. Only one case showed desmin positivity in sparse cells in the nonrhabdoid component of the tumor. All of the cases were negative for CEA, MOC-31, TAG-72, CD15, CD34, bcl2, muscle-specific actin, and TTF-1. Ultrastructural studies revealed paranuclear collections of intermediate filaments, but no evidence of rhabdomyoblastic differentiation was seen. The mean survival of five of the six patients for whom this information was available was 3.8 months. The remaining patient had a survival time of 1 year. It is important for pathologists to be aware that mesotheliomas can present rhabdoid features, not only because they can be confused with other malignancies that can exhibit a similar morphology, but also because of their apparently unusually aggressive behavior. The value of immunohistochemistry and electron microscopy in the differential diagnosis of these tumors is discussed.

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.

The p270 (ARID1A/SMARCF1) subunit of mammalian SWI/SNF-related complexes is essential for normal cell cycle arrest

Mammalian SWI/SNF-related complexes are ATPase-powered nucleosome remodeling assemblies crucial for proper development and tissue-specific gene expression. The ATPase activity of the complexes is also critical for tumor suppression. The complexes contain seven or more noncatalytic subunits; only one of which, hSNF5/Ini1/BAF47, has been individually identified as a tumor suppressor thus far. The noncatalytic subunits include p270/ARID1A, which is of particular interest because tissue array analysis corroborated by screening of tumor cell lines indicates that p270 may be deficient in as many as 30% of renal carcinomas and 10% of breast carcinomas. The complexes can also include an alternative ARID1B subunit, which is closely related to p270, but the product of an independent gene. The respective importance of p270 and ARID1B in the control of cell proliferation was explored here using a short interfering RNA approach and a cell system that permits analysis of differentiation-associated cell cycle arrest. The p270-depleted cells fail to undergo normal cell cycle arrest on induction, as evidenced by continued synthesis of DNA. These lines fail to show other characteristics typical of arrested cells, including up-regulation of p21 and down-regulation of cyclins. The requirement for p270 is evident separately in both the up-regulation of p21 and the down-regulation of E2F-responsive products. In contrast, the ARID1B-depleted lines behaved like the parental cells in these assays. Thus, p270-containing complexes are functionally distinct from ARID1B-containing complexes. These results provide a direct biological basis to support the implication from tumor tissue screens that deficiency of p270 plays a causative role in carcinogenesis.

Malignant rhabdoid tumor in a pregnant adult female: literature review of central nervous system rhabdoid tumors

Rhabdoid tumors of the central nervous system are uncommon, aggressive childhood malignancies. The 13 described adult cases comprise both primary CNS tumors and malignant transformation of previously existing gliomas, meningiomas, and astrocytomas. Central nervous system rhabdoid lesions of adults have been diagnosed as primary malignant rhabdoid tumors, atypical teratoid/rhabdoid tumors, and more recently, rhabdoid glioblastomas. We report a case of a 20-year-old woman in her 30th week of pregnancy who presented with headache, nausea and blurry vision. MRI revealed a large rim-enhancing mass of the right occipital lobe. Gross total resection was achieved via a right parietal-occipital craniotomy. Pathologic evaluation revealed histology, electron microscopy and immunohistochemistry consistent with the diagnosis of malignant rhabdoid tumor. FISH studies were negative for the INI-1 genetic mutations and chromosome 22q deletion associated with childhood atypical rhabdoid/rhabdoid tumor in 75% of cases. The patient delivered her infant via caesarian section prior to initiating further therapy. We briefly describe the characteristics and current understanding of rhabdoid tumors, and review the literature comparing the 12 other cases of central nervous system rhabdoid tumors in adults. Furthermore, we consider and discuss the implications of this case being the second presentation of MRT during pregnancy in only six adult female patients.

Monoclonal antibodies reactive with the BAF155 (SMARCC1) and BAF170 (SMARCC2) components of human SWI/SNF-related complexes

Mammalian SWI/SNF-related chromatin remodeling complexes are required for transcription controls that underlie differentiation, development, and tumor suppression. The complexes each consist of an ATPase of the SWI2/SNF2 family and approximately seven stably associated non-catalytic subunits. In spite of the importance of these complexes to biological processes, monoclonal antibodies to the various subunits have not been readily available. Mammalian complexes can vary in subunit composition, but the BAF155 (SMARCC1) subunit and a closely related protein, BAF170 (SMARCC2), appear to be ubiquitous components. Here we report the development of antibodies raised against a BAF155-derived peptide. The antibodies were raised against a single peptide of 18 amino acids. However, hybridomas expressing antibodies of two different specificities were isolated. One, designated DXD7, is specific for BAF155. The other, designated DXD12, is reactive with both BAF155 and BAF170. The antibodies are reactive against both native and denatured proteins, and are suitable for immunoprecipitation and Western blots. The DXD7 antibody is suitable additionally for immunofluorescence assays.

SMARCB1/INI1Tumor Suppressor Gene Is Frequently Inactivated in Epithelioid Sarcomas

Epithelioid sarcoma is a rare soft tissue neoplasm of uncertain lineage that usually arises in the distal extremities of adults, presents a high rate of recurrences and metastases and frequently poses diagnostic dilemmas. The recently reported large-cell "proximal-type" variant is characterized by increased aggressiveness, deep location, preferential occurrence in proximal/axial regions of older patients, and rhabdoid features. Previous cytogenetic studies indicated that the most frequent alterations associated with this tumor entity affect chromosome 22. In this study, combined spectral karyotyping, fluorescence in situ hybridization, and array-based comparative genomic hybridization analyses of two proximal-type cases harboring a rearrangement involving 10q26 and 22q11 revealed that the 22q11 breakpoints were located in a 150-kb region containing the SMARCB1/INI1 gene, and that homozygous deletion of the gene was present in the tumor tissue. The SMARCB1/INI1 gene encodes for an invariant subunit of SWI/SNF chromatin remodeling complex and has been previously reported to act as a tumor suppressor gene frequently inactivated in infantile malignant rhabdoid tumors. We analyzed SMARCB1/INI1 gene status in nine additional epithelioid sarcoma cases (four proximal types and five conventional types) and altogether we identified deletions of SMARCB1/INI1 gene in 5 of 11 cases, all proximal types. We confirmed and further extended the number of cases with SMARCB1/INI1 inactivation to 6 of 11 cases, by real-time quantitative PCR analysis of mRNA expression and by SMARCB1/INI1 immunohistochemistry. Overall, these results point to SMARCB1/INI1 gene involvement in the genesis and/or progression of epithelioid sarcomas. Analysis of larger series of epithelioid sarcomas will be necessary to highlight putative clinically relevant features related to SMARCB1/INI1 inactivation.

Establishment of a cell line from a malignant rhabdoid tumor of the liver lacking the function of two tumor suppressor genes, hSNF5/INI1 and p16

Malignant rhabdoid tumors (MRT) of the liver are rare. A few liver MRT cell lines have been established but none has been characterized in detail. Here we describe a new MRT cell line from the liver, which is designated MP-MRT-AN, and describe it in detail. Immunohistochemical assays detected the expression of vimentin and cytokeratin but they were negative for neurofilament, desmin, alpha-smooth muscle actin, alpha-sarcomeric actin, and smooth muscle myosin heavy chains SM1 and SM2. RT-PCR assays revealed that this cell line did not express smooth muscle myosin heavy chain isoforms or MyoD1. No aberration was identified in 22q by G-banded analysis; however, the hSNF5/INI1 gene, a suppressor gene of MRT that maps to 22q11.2, was homozygously deleted from exons 1 to 5 in this cell line. Furthermore, the expression of another tumor suppressor gene, p16 (CDKN2A), was not detected by RT-PCR. This raises the possibility that the aggressive phenotype of malignant rhabdoid tumors is caused by the loss of two or more tumor suppressor genes.

Differentiation of classic medulloblastoma into metastatic large cell medulloblastoma with focal rhabdoid differentiation in the absence of posterior fossa recurrence

A case of classic medulloblastoma that metastasized, despite the absence of local recurrence, to extraneural sites 7 years after treatment is reported. The metastases were, in contrast to the primary tumor, of large cell type and displayed abortive myogenic and, in one site, also rhabdoid differentiation. The primary tumor expressed microtubule-associated protein 1B and neuron-specific nuclear protein (NeuN), and was desmin negative. The metastases were also positive for microtubule-associated protein 1B and NeuN, although the expression of the latter marker was weak and/or focal in two of four metastases and absent in the rhabdoid metastasis. They were, in contrast with the primary tumor, all strongly positive for desmin. The hSNF5/INI1 was expressed in the nuclei of all cells of the primary tumor and the metastases, including the one with rhabdoid differentiation. Two metastases were studied by cytogenetics. The composite karyotype of a large cell metastasis was 45~46,XY,add(1)(p36.1),t(2;8)(p21;q24.1),add(3)(q25),t(9;15)(q22;q13),add(12)(p11.2), +1approximately2mar,inc[cp12]/46,XY[12], while the rhabdoid metastasis contained additional changes including monosomy 22. These findings indicate that some rhabdoid (atypical teratoid/rhabdoid) tumors of the cerebellum and medulloblastoma may be histogenetically related.

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.

Pediatric embryonal tumor with epithelial immunophenotype showing absence of hSNF5/INI1 expression

CASE REPORT

A case of a histologically unclassified brain tumor in a 32-month-old boy is reported. He presented with vomiting, appetite loss, and right motor weakness. MR images revealed a huge mass in the left frontoparietal region that was enhanced after the administration of Gd-DTPA. The mass was removed three times because of its recurrence.

RESULTS

Histologically, the tumor was composed largely of small-undifferentiated round cells without any patterns of differentiation. Immunohistochemically, the tumor cells were positive for cytokeratin and focally for epithelial membrane antigen (EMA). Glial fibrillary acidic protein (GFAP), S-100 protein and neuronal markers were negative. Electron microscopic investigations demonstrated no evidence of specific differentiation. MIB-1 staining index was 10-40%. The origin of the tumor was not detected. Expression of the hSNF5/INI1 of this tumor was not detected by reverse transcription-polymerase chain reaction (RT-PCR). The patient has been in a good condition for 7 years after the first operation.

CONCLUSIONS

Based on the immunohistochemical findings, the tumor was descriptively diagnosed as an embryonal tumor with an epithelial immunophenotype. The hSNF5/INI1 gene has recently been reported to act as a tumor suppressor in atypical teratoid/rhabdoid tumors. The hSNF5/INI1 gene may lead to tumorigenesis in this case.

Malignant rhabdoid tumor arising from a pleomorphic adenoma

Malignant transformation of pleomorphic adenomas often occurs in long-standing tumors or tumors with multiple local recurrences. The malignant component is usually a carcinoma. The case reported herein concerns a 60-year-old man who had a malignant rhabdoid tumor arising in a painless parotid mass that remained untreated for 25 years. Malignant rhabdoid tumors are clinically aggressive neoplasms with phenotypic features that resemble rhabdomyomatous differentiation but lack genuine skeletal muscle differentiation. The salient features of rhabdoid tumor cell include large, pleomorphic, and eccentric nucleus and a solitary and prominent intracytoplasmic inclusion that is strongly immunoreactive for vimentin. It is our understanding that this is the first reported case of malignant rhabdoid tumor arising in the parotid gland in the English literature. The pathologic features of our case will be discussed in context with malignant rhabdoid tumors from other parts of the body.

Genetic and epigenetic screening for gene alterations of the chromatin-remodeling factor, SMARCA4/BRG1, in lung tumors

The SMARCA4/BRG1 gene product is a component of the SWI-SNF chromatin-remodeling complex and regulates gene expression by disrupting histone-DNA contacts in an ATP-dependent manner. Inactivating mutations of the SMARCA4 gene, on chromosome arm 19p, are present in several human cancer cell lines, including cell lines derived from lung cancers. Interestingly, loss of heterozygosity (LOH) at 19p and absence of the SMARCA4 protein have been reported in lung tumors. To evaluate further the possible contribution of SMARCA4 gene inactivation to lung carcinogenesis, we performed a complete analysis of the SMARCA4 gene to search for (a) point mutations in all 35 coding exons, including an existing splicing variant and the intron-exon boundaries, and (b) abrogation of gene expression through promoter hypermethylation by using the methylation-specific polymerase chain reaction (MSP) assay. We selected genomic DNA from 20 lung primary tumors with LOH on 19p for the screening of point mutations and 10 lung cancer cell lines and 52 lung primary tumors for the MSP analysis. Through our mutational screening, we identified an in-frame and germ-line insertion of 24 bp in exon 4 whose biological relevance is unknown. This variant was not detected in the germ line of the 62 additional individuals analyzed, indicating it is not a common polymorphism. Moreover, two missense alterations were identified in the tumors of 2 patients, a somatic Gly1160Arg mutation and a Ser1176Cys mutation. Neither was present in the germ line of the 51 additional lung cancer individuals tested. Because these mutations lead to substitution of highly conserved amino acids, they may affect the ATPase function of the protein. Finally, no promoter hypermethylation was observed in any lung primary tumor or cancer cell line, indicating that this is not a major mechanism for SMARCA4 inactivation during lung carcinogenesis. In conclusion, our data revealed that somatic point mutations of the SMARCA4 gene are present in a small subset of lung tumors, although mutations affecting the ATPase domain may be a hot-spot for SMARCA4 gene inactivation. We cannot rule out that other mechanisms, such as complete or partial deletions of the SMARCA4 gene, are contributing to the loss of the SMARCA4 protein in lung cancer.

Translocation (1;22)(p36;q11.2) with concurrent del(22)(q11.2) resulted in homozygous deletion of SNF5/INI1 in a newly established cell line derived from extrarenal rhabdoid tumor

Malignant rhabdoid tumor (MRT) is a highly malignant pediatric cancer, which arises in various sites such as the kidney, brain, and soft tissues. Cytogenetic studies have revealed alterations of 22q11 in MRT. Recently, deletions and mutations of the SNF5/INI1 locus in 22q11.2 have been reported in MRT, suggesting that SNF5/INI1 is a tumor suppressor gene for MRT. Here we report our molecular cytogenetic study for a newly established cell line from extrarenal MRT with t(1;22)(p36;q11.2). Consequently, the reciprocal translocation was associated with the interstitial deletion of a small segment including SNF5/INI1, and another, chromosome 22, showed terminal deletion, the breakpoint of which was located 70-80 kb centromeric to SNF5/INI1, resulting in homozygous deletion of SNF5/INI1 in this cell line.

Antitumor Activity of Gefitinib in Malignant Rhabdoid Tumor Cells In vitro and In vivo

PURPOSE

Malignant rhabdoid tumor (MRT) is a rare and highly aggressive neoplasm of young children. Current treatments have had only limited success. Epidermal growth factor receptor (EGFR) was found recently to be expressed on MRT cell lines. Gefitinib (trade name Iressa) is an oral and selective EGFR-tyrosine kinase inhibitor and has been demonstrated to be effective in inhibiting the proliferation of cancer cells in vivo as well as in clinical trials. This encouraged us to examine the antitumor effects of gefitinib on MRT cells in vitro and in vivo.

EXPERIMENTAL DESIGN

The expression of EGFR in two MRT tumors and two MRT cell lines (MP-MRT-AN and KP-MRT-NS), established from these two tumor tissues, was examined by immunohistochemistry, immunofluorescence, and immunoblot. The effect of gefitinib on EGFR phosphorylation was examined by immunoblot. The effects of gefitinib on cell growth and apoptosis were examined by cell growth assay and terminal deoxynucleotidyl transferase-mediated nick end labeling assay. The in vivo effect of gefitinib was assessed in athymic mice that had been xenografted with MRT cells.

RESULTS

The expression of EGFR was detected in both tumor tissues and cell lines. Gefitinib inhibited EGFR-phosphorylation (IC(50) < 0.1 micromol/L) and in vitro cell growth (IC(50) = approximately 10-12 micromol/L), and a high concentration of gefitinib (20 micromol/L) induced apoptosis in vitro (MP-MRT-AN, 42.9% and KP-MRT-NS, 47.2%). Furthermore, gefitinib at 150 mg/kg had a cytostatic effect on established MRT xenografts (MP-MRT-AN, P = 0.039 and 0.0014; and KP-MRT-NS, P = 0.048 and 0.0086).

CONCLUSIONS

Our results demonstrate that gefitinib has antitumor effects in MRT cells in vitro and in vivo and, thus, has promise as a novel and therapeutic strategy for MRT.

Gene expression profiling and identification of novel prognostic marker genes in neuroblastoma

To investigate the various genetic characteristics of and differences between early- and advanced-stage neuroblastoma (NB) and to identify candidate genes involved in NB progression, we performed DNA microarray analysis on 20 primary tumors. Two-way clustering analysis based on the expression pattern of approximately 500 of 1,700 genes revealed genetic subgroups in these NB tumors. Although 9 of the 13 early-stage tumors (69%) and 4 of the 6 advanced-stage tumors (67%) were classified as being in the same cluster, the remaining tumors showed different expression profiles. This indicates that both the early- and advanced-stage tumors were heterogeneous. Based on the microarray data, we identified the BIRC, CDKN2D, and SMARCD3 genes as those that are predominantly expressed in either the early or the advanced stage of NB. These genes have been reported to be associated with apoptosis, cell cycles, and the transcriptional activator, respectively. To better assess the prognostic value of the expression of these genes in NB, real-time polymerase chain reaction was carried out on 50 primary tumors. The expression of both the BIRC3 and CDKN2D genes was significantly higher in the early-stage group than in the advanced-stage group (P = 0.002 and 0.003, respectively), whereas the expression of the SMARCD3 gene was significantly reduced in the early-stage group (P = 0.02). Therefore, the BIRC, CDKN2D, and SMARCD3 genes are possible candidates for being novel prognostic markers for NB.