Emerging therapeutic targets for the treatment of malignant rhabdoid tumors

Malignant Rhabdoid Tumor and Related Pediatric Tumors: Multimodality Imaging Review with Pathologic Correlation

Malignant rhabdoid tumors (MRTs) are rare but lethal solid neoplasms that overwhelmingly affect infants and young children. While the central nervous system is the most common site of occurrence, tumors can develop at other sites, including the kidneys and soft tissues throughout the body. The anatomic site of involvement dictates tumor nomenclature and nosology. While the clinical and imaging manifestations of MRTs and other more common entities may overlap, there are some site-specific distinctive imaging characteristics. Irrespective of the site of occurrence, somatic and germline mutations in SMARCB1, and rarely in SMARCA4, underlie the entire spectrum of rhabdoid tumors. MRTs have a simple and remarkably stable genome but can demonstrate considerable molecular and biologic heterogeneity. Related neoplasms encompass an expanding category of phenotypically dissimilar (nonrhabdoid tumors driven by SMARC-related alterations) entities. US, CT, MRI, and fluorodeoxyglucose PET/CT or PET/MRI facilitate diagnosis, initial staging, and follow-up, thus informing therapeutic decision making. Multifocal synchronous or metachronous rhabdoid tumors occur predominantly in the context of underlying rhabdoid tumor predisposition syndromes (RTPSs). These autosomal dominant disorders are driven in most cases by pathogenic variants in SMARCB1 (RTPS type 1) and rarely by pathogenic variants in SMARCA4 (RTPS type 2). Genetic testing and counseling are imperative in RTPS. Guidelines for imaging surveillance in cases of RTPS are based on age at diagnosis. ©RSNA, 2024 Supplemental material is available for this article.

Successful multimodality management of extrarenal extracranial malignant rhabdoid tumour of the left sciatic nerve mimicking a neurofibroma

Extrarenal extracranial malignant rhabdoid tumour (MRT) is a rare and highly aggressive tumour representing <1% of paediatric soft tissue malignancies. Only a few cases of MRT of the thigh arising from the sciatic nerve have been reported in medical literature to date. A 5-year-old girl presented with progressively increasing painless lump in the posterior aspect of the left thigh. A contrast-enhanced magnetic resonance imaging (MRI) of the left thigh showed a 4.7 × 5 × 10.5 cm well-marginated, lobulated, homogeneously enhancing lesion in the posterior compartment of the left thigh along the course of the sciatic nerve. She underwent en bloc excision of the left sciatic nerve tumour and end-to-end anastomosis of the left sciatic nerve with a right sural nerve graft. Histopathological and immunohistochemical examination of the surgical specimen revealed a malignant rhabdoid tumour. INI-1 immunoexpression was lost in the tumour cells. The metastatic workup was essentially normal. Subsequently, she received post-operative radiotherapy to the tumour bed (50.4 Gray in 28 fractions over 5.5 weeks) followed by six cycles of multiagent chemotherapy with ICE (Ifosfamide, Carboplatin, and Etoposide) regimen. On the last follow-up visit, 20 months after surgery, she was in complete clinical and radiological response. Aggressive multimodality management comprising radical resection of tumour, post-operative radiotherapy to the tumour bed, and multiagent chemotherapy with ICE regimen can lead to favourable outcomes in patients with this rare tumour.

Review on Pediatric Malignant Focal Liver Lesions with Imaging Evaluation: Part II

Malignant focal liver lesions (FLLs) represent various kinds of epithelial and mesenchymal tumors. In pediatric patients, the understanding of pediatric liver diseases and associated imaging manifestations is essential for making accurate diagnosis and differential diagnosis. This paper will discuss the latest knowledge of the common pediatric malignant FLLs, including undifferentiated embryonal sarcoma, rhabdomyosarcoma, epithelioid hemangioendothelioma, angiosarcoma, and malignant rhabdoid tumor. Medical imaging features are not only helpful for clinical diagnosis, but can also be useful in the evaluation and follow-up of pre- and post-treatment. The future perspectives of contrast-enhanced ultrasound (CEUS) enhancement patterns of FLLs in pediatric patients are also mentioned.

Landscape of somatic mutated genes and inherited susceptibility genes in gynecological cancer

Traditionally, gynecological cancers have been classified based on histology. Since remarkable advancements in next-generation sequencing technology have enabled the exploration of somatic mutations in various cancer types, comprehensive sequencing efforts have revealed the genomic landscapes of some common forms of human cancer. The genomic features of various gynecological malignancies have been reported by several studies of large-scale genomic cohorts, including The Cancer Genome Atlas. Although recent comprehensive genomic profiling tests, which can detect hundreds of genetic mutations at a time from cancer tissues or blood samples, have been increasingly used as diagnostic clinical biomarkers and in therapeutic management decisions, germline pathogenic variants associated with hereditary cancers can also be detected using this test. Gynecological cancers are closely related to genetic factors, with approximately 5% of endometrial cancer cases and 20% of ovarian cancer cases being caused by germline pathogenic variants. Hereditary breast and ovarian cancer syndrome and Lynch syndrome are the two major cancer susceptibility syndromes among gynecological cancers. In addition, several other hereditary syndromes have been reported to be associated with gynecological cancers. In this review, we highlight the genes for somatic mutation and germline pathogenic variants commonly seen in gynecological cancers. We first describe the relationship between clinicopathological attributes and somatic mutated genes. Subsequently, we discuss the characteristics and clinical management of inherited cancer syndromes resulting from pathogenic germline variants in gynecological malignancies.

Targeting EZH2 in SMARCB1-deficient sarcomas: Advances and opportunities to potentiate the efficacy of EZH2 inhibitors

Soft tissue sarcomas (STSs) are rare mesechymal malignancies characterized by distintive molecular, histological and clinical features. Many STSs are considered as predominatly epigenetic diseases due to underlying chromatin deregulation. Discovery of deregulated functional antagonism between the chromatin remodeling BRG1/BRM-associated (BAFs) and the histone modifying Polycomb repressor complexes (PRCs) has provided novel actionable targets. In epithelioid sarcoma (ES), extracranial, extrarenal malignant rhabdoid tumors (eMRTs) and synovial sarcoma (SS), the total or partial loss of the BAF core subunit SMARCB1, driven by different alterations, is associated with PRC2 deregulation and dependency on its enzymatic subunit, EZH2. In these SMARCB1-deficient STSs, aberrant EZH2 expression and/or activity emerged as a druggable vulnerability. Although preclinical investigation supported EZH2 targeting as a promising therapeutic option, clinical studies demonstrated a variable response to EZH2 inhibitors. Actually, whereas the clinical benefit recorded in ES patients prompted the FDA approval of the EZH2 inhibitor tazemetostat, the modest and sporadic responses observed in eMRT and SS patients highlighted the need to deepen mechanistic as well as pharmacological investigations to improve drug effectiveness. We summarize the current knowledge of different mechanisms driving SMARCB1 deficiency and EZH2 deregulation in ES, eMRT and SS along with preclinical and clinical studies of EZH2-targeting agents. Possible implication of the PRC2- and enzymatic-independent functions of EZH2 and of its homolog, EZH1, in the response to anti-EZH2 agents will be discussed together with combinatorial strategies under investigation to improve the efficacy of EZH2 targeting in these tumors.

Malignant rhabdoid tumor of the omentum in an adult male: a case report and literature review

Malignant rhabdoid tumors (MRTs) are rare tumors with high mortality rates and poor prognoses. MRTs occur mainly in the central nervous system, kidneys, and soft tissues, but rarely in the omentum. MRTs occur more commonly in infants and children and less frequently in adults. Here, we report the first observed case of MRT in an adult omentum. A 35-year-old man with abdominal distension and pain was admitted to the emergency department. Previously, several hospitals considered patients with cirrhosis who had not received active treatment. Computed tomography and magnetic resonance imaging revealed diffuse omental thickening and massive ascites. The surgery was performed at our hospital, and the pathological diagnosis was MRT with a SMARCB1(INI-1) deletion. Postoperatively, his symptoms improved, and he underwent five cycles of chemotherapy. However, 6 months after surgery, the tumor developed liver metastases, and the patient subsequently died. Primary MRT of the greater omentum is rare, and its pathological diagnosis usually requires extensive clinicopathological evaluation of various differential diagnoses and an appropriate work-up to exclude other malignancies associated with SMARCB1 deletion. At the same time, the lack of specific signs of omental MRT and its rapid progression should alert clinicians.

The Swedish childhood tumor biobank: systematic collection and molecular characterization of all pediatric CNS and other solid tumors in Sweden

The Swedish Childhood Tumor Biobank (BTB) is a nonprofit national infrastructure for collecting tissue samples and genomic data from pediatric patients diagnosed with central nervous system (CNS) and other solid tumors. The BTB is built on a multidisciplinary network established to provide the scientific community with standardized biospecimens and genomic data, thereby improving knowledge of the biology, treatment and outcome of childhood tumors. As of 2022, over 1100 fresh-frozen tumor samples are available for researchers. We present the workflow of the BTB from sample collection and processing to the generation of genomic data and services offered. To determine the research and clinical utility of the data, we performed bioinformatics analyses on next-generation sequencing (NGS) data obtained from a subset of 82 brain tumors and patient blood-derived DNA combined with methylation profiling to enhance the diagnostic accuracy and identified germline and somatic alterations with potential biological or clinical significance. The BTB procedures for collection, processing, sequencing, and bioinformatics deliver high-quality data. We observed that the findings could impact patient management by confirming or clarifying the diagnosis in 79 of the 82 tumors and detecting known or likely driver mutations in 68 of 79 patients. In addition to revealing known mutations in a broad spectrum of genes implicated in pediatric cancer, we discovered numerous alterations that may represent novel driver events and specific tumor entities. In summary, these examples reveal the power of NGS to identify a wide number of actionable gene alterations. Making the power of NGS available in healthcare is a challenging task requiring the integration of the work of clinical specialists and cancer biologists; this approach requires a dedicated infrastructure, as exemplified here by the BTB.

BKM120 inhibits malignant rhabdoid tumor of the kidney through induction of apoptosis and G0/G1 phase arrest

Malignant rhabdomyosarcoma of the kidney (MRTK) has an inferior prognosis and is insensitive to radiotherapy and chemotherapy. Search for novel, potent medicinal agents is urgent. Herein, data on the gene expression and clinical characteristics of malignant rhabdoid tumors (MRT) were retrieved from the TARGET database. Prognosis-related genes were identified by differential analysis and one-way cox regression analysis, and prognosis-related signalling pathways were identified by enrichment analysis. The prognosis-related genes were imported into the Connectivity Map database for query, and BKM120 was predicted and screened as a potential therapeutic agent for MRTK. A combination of high-throughput RNA sequencing and Western blot verified that the PI3K/Akt signaling pathway is associated with MRTK prognosis and is overactivated in MRTK. Our results outlined that BKM120 inhibited the proliferation, migration, and invasion ability of G401 cells and induced apoptosis and cell cycle G0/G1 phase arrest. In vivo, BKM120 inhibited tumor growth and had no significant toxic side effects. Western blot and immunofluorescence results confirmed that BKM120 could reduce the expression of PI3K and p-AKT, critical proteins of the PI3K/Akt signaling pathway. BKM120 inhibits MRTK by inhibiting PI3K/Akt signalling pathway to induce apoptosis and cell cycle G0/G1 phase arrest, which is anticipated to give the clinical treatment of MRTK a new direction.

Commentary on: SMARCB1 as a novel diagnostic and prognostic biomarker for osteosarcoma

In the last couple of decades, biomarkers have been on the rise for diagnostic and predictive value. There has been a rush to identify new markers using new technologies and drug repurposing approaches. SMARCB1 acronym arises from the SWI/SNF (SWItch/Sucrose Non-Fermentable)-related Matrix-associated Actin-dependent Regulator of Chromatin subfamily B member 1 (SMARCB1). It is a molecule, whose role is associated with the sucrose metabolism. SMARCB1 is also called INI1 (Integrase Interactor 1). The molecule was discovered in the mid-1990s. Its role as a loss-of-function marker for malignant rhabdoid tumors (MRT) of renal and extrarenal origin has enormously expanded the spectrum of involved neoplasms since that time. Several tumors have been characterized by genetic aberrations in the SMARCB1 gene. They include reduction in expression, loss of expression, and mosaic expression. Most of the tumors are sarcomas, but a variegated group of tumors with mixed phenotypes has also been delineated. It is well known that the outcome of patients harboring genetic aberrations in the SMARCB1 gene has been poor. Guo et al. reported that reduced SMARCB1 expression occurred in 70% of osteosarcomas. Their data significantly correlated with poor neoadjuvant response. These authors emphasize a shorter progression-free and overall survival of the patients demonstrating an altered expression of this gene. Interestingly, mRNA in silico analysis established that SMARCB1 expression correlates with the response to chemotherapy of osteosarcoma patients, but there was no reliable correlation between SMARCB1 expression level and metastasis, response to neoadjuvant therapy, overall survival, and progression-free survival. The study involved a tissue microarray (TMA) on bone tumors that may limit the full evaluation of the gene expression. Nevertheless, Guo et al.’s study is remarkable. It expands the list of the tumors harboring an altered SMARCB1 gene expression and suggests that this marker should be investigated in every pathology workup for potential predictive value. On the other side, much work needs to be done if we hope that we strive to provide additional therapeutic strategies for osteosarcoma patients with altered SMARCB1 gene expression.

Therapeutic Targeting of EZH2 and BET BRD4 in Pediatric Rhabdoid Tumors

Aberrant activity of the H3K27 modifiers EZH2 and BRD4 is an important oncogenic driver for atypical teratoid/rhabdoid tumor (AT/RT), and each is potentially a possible therapeutic target for treating AT/RT. We, therefore, determined whether targeting distinct histone modifier activities was an effective approach for treating AT/RT. The effects of EZH2 and BRD4 inhibition on histone modification, cell proliferation, and cell invasion were analyzed by immunoblotting, MTS assay, colony formation assay, and cell invasion assay. RNA- and chromatin immunoprecipitation-sequencing were used to determine transcriptional and epigenetic changes in AT/RT cells treated with EZH2 and BRD4 inhibitors. We treated mice bearing human AT/RT xenografts with EZH2 and BRD4 inhibitors. Intracranial tumor growth was monitored by bioluminescence imaging, and the therapeutic response was evaluated by animal survival. AT/RT cells showed elevated levels of H3K27 trimethylation (H3K27me3) and H3K27 acetylation (H3K27ac), with expression of EZH2 and BRD4, and lack of SMARCB1 proteins. Targeted inhibition of EZH2 and BRD4 activities reduced cell proliferation and invasiveness of AT/RT in association with decreasing H3K27me3 and H3K27ac. Differential genomic occupancy of H3K27me3 and H3K27ac regulated specific gene expression in response to EZH2 and BRD4 inhibitions. A combination of EZH2 and BRD4 inhibition increased the therapeutic benefit in vitro and in vivo, outperforming either monotherapy. Overall, histones H3K27me3 and H3K27ac were elevated in AT/RT cells and distributed in distinct chromatin regions to regulate specific gene expression and to promote AT/RT growth. Targeting EZH2 and BRD4 activity is, therefore, a potential combination therapy for AT/RT.

Rare Hereditary Gynecological Cancer Syndromes

Hereditary cancer syndromes, which are characterized by onset at an early age and an increased risk of developing certain tumors, are caused by germline pathogenic variants in tumor suppressor genes and are mostly inherited in an autosomal dominant manner. Therefore, hereditary cancer syndromes have been used as powerful models to identify and characterize susceptibility genes associated with cancer. Furthermore, clarification of the association between genotypes and phenotypes in one disease has provided insights into the etiology of other seemingly different diseases. Molecular genetic discoveries from the study of hereditary cancer syndrome have not only changed the methods of diagnosis and management, but have also shed light on the molecular regulatory pathways that are important in the development and treatment of sporadic tumors. The main cancer susceptibility syndromes that involve gynecologic cancers include hereditary breast and ovarian cancer syndrome as well as Lynch syndrome. However, in addition to these two hereditary cancer syndromes, there are several other hereditary syndromes associated with gynecologic cancers. In the present review, we provide an overview of the clinical features, and discuss the molecular genetics, of four rare hereditary gynecological cancer syndromes; Cowden syndrome, Peutz-Jeghers syndrome, DICER1 syndrome and rhabdoid tumor predisposition syndrome 2.

Malignant rhabdoid tumor of the liver in a middle-aged woman: a case report and literature review

Background

Extrarenal malignant rhabdoid tumor (EMRT) is a rare and high-mortality malignant tumor, which is more common in infants and rarely seen in adults. We firstly report a case of liver malignant rhabdoid tumor (MRT) with a loss of SMARCB1 gene (alias INI1, SNF5, BAF47) expression in a middle-aged woman, and preliminarily summarize the clinical characteristics and discuss its potential treatment of liver MRT by reviewing 55 cases reported in the past.

Case presentation

We report a 40-year-old woman who was admitted to our hospital for right epigastric pain. Previously, the patient was treated with liver hematoma in another hospital until she came to our hospital for abdominal pain again. In our hospital, we performed surgical treatment on her and the pathology diagnosed EMRT with negative expression of SMARCB1. After surgery, the patient underwent genetic testing, but failed to screen for sensitive targeted or conventional chemotherapy drugs, and she did not receive further treatment. Due to lack of timely diagnosis and effective chemotherapy drugs, tumor recurrence and metastasis occurred one year after surgery. Then the patient chose traditional Chinese medicine for treatment. And the metastatic tumors had still progressed after one year of treatment, but the patient didn’t have obvious discomfort symptoms.

Conclusions

Liver MRT is a highly aggressive tumor with high metastatic potential and poor prognosis. It lacks specific symptoms and signs and is easy to be ignored and misdiagnosed. The mortality rate is extremely high as there is no effective treatment. But most tumors are accompanied by SMARCB1 deficiency, which may offer new research directions for cancer therapeutics. For the present, early detection, early diagnosis and early resection remain the key to improve the prognosis of patients.

A Systematic Review and Meta-Analysis of Malignant Rhabdoid and Small Cell Undifferentiated Liver Tumors: A Rational for a Uniform Classification

Simple Summary

Malignant rhabdoid tumors of the liver are very rare pediatric liver tumors with a devastating prognosis. It is currently unclear which histological subtypes of pediatric liver tumors belong to this entity and how these tumors should be treated. In this systematic review with meta-analysis, we analyzed all reports on pediatric patients with malignant rhabdoid liver tumors, but also with so-called small cell undifferentiated liver tumors. This is another rare liver tumor subtype that has recently been regarded to belong to the entity of rhabdoid tumors by some authors. The main result of this study is that these two tumor subtypes show large overlap on several levels and even mixtures of both histological patterns have been documented. Our meta-analysis provides an evidence base for the recommendation to classify these two tumor subtypes as one entity. We showed that treatment of these tumors with hepatoblastoma directed chemotherapy is ineffective and that a therapy with chemotherapy regimens initially applied for soft tissue sarcoma is associated with a significantly better survival. This study represents the highest level of evidence available for these rare liver tumors.

Abstract

Background: Rhabdoid liver tumors in children are rare and have a devastating prognosis. Reliable diagnosis and targeted treatment approaches are urgently needed. Immunohistochemical and genetic studies suggest that tumors formerly classified as small cell undifferentiated hepatoblastoma (SCUD) belong to the entity of malignant rhabdoid tumors of the liver (MRTL), in contrast to hepatoblastomas with focal small cell histology (F-SCHB). This may have relevant implications on therapeutic approaches. However, studies with larger cohorts investigating the clinical relevance of the histological and genetic similarities for patients are lacking. Purpose: To analyze possible similarities and differences in patient characteristics, tumor biology, response to treatment, and clinical course of patients with MRTL, SCUD and F-SCHB. Applied therapeutic regimens and prognostic factors are investigated. Methods: A systematic literature search of MEDLINE, Web of Science, and CENTRAL was performed for this PRISMA-compliant systematic review. All studies of patients with MRTL, SCUD and F-SCHB that provided individual patient data were included. Demographic, histological, and clinical characteristics of the three subgroups were compared. Overall survival (OS) was estimated with the Kaplan–Meier method and prognostic factors investigated in a multivariable Cox regression model. Protocol registered: PROSPERO 2021 CRD42021258760. Results: Fifty-six studies with a total of 118 patients were included. The two subgroups MRTL and SCUD did not differ significantly in baseline patient characteristics. However, heterogenous diagnostic and therapeutic algorithms were applied. Large histological and clinical overlap between SCUD and MRTL could be shown. Two-year OS was 22% for MRTL and 13% for SCUD, while it was significantly better in F-SCHD (86%). Chemotherapeutic regimens for hepatoblastoma proved to be ineffective for both SCUD and MRTL, but successful in F-SCHB. Soft tissue sarcoma chemotherapy was associated with significantly better survival for MRTL and SCUD, but was rarely applied in SCUD. Patients who did not undergo surgical tumor resection had a significantly higher risk of death. Conclusions: While F-SCHB is a subtype of HB, SCUD should be classified and treated as a type of MRTL. Surgical tumor resection in combination with intensive, multi-agent chemotherapy is the only chance for cure of these tumors. Targeted therapies are highly needed to improve prognosis. Currently, aggressive regimens including soft tissue sarcoma chemotherapy, extensive resection, radiotherapy or even liver transplantation are the only option for affected children.

Endogenous Retroviral Elements in Human Development and Central Nervous System Embryonal Tumors

Human endogenous retroviruses (HERVs), which are critical to normal embryologic development and downregulated during normal maturation, have been implicated in a variety of cancers. Abnormal persistent production of HERVs has been suggested to play a role in oncogenesis and to confer stem cell properties to cells. We recently demonstrated that the most recently incorporated HERV element (HERV-K HML-2) has been associated with the pathogenesis of the embryonal atypical teratoid rhabdoid tumor (AT/RT), shifting our understanding of embryonal tumor development. HML-2 expression is vital for proper human development and its expression is suppressed via methylation or chromatin remodeling as cells differentiate. We previously found that dysfunctional chromatin remodeling due to loss of SMARCB1 expression induces HML-2 envelope (env) expression, impairing cellular differentiation and migration, and facilitating tumor growth in AT/RT. Epigenetic dysregulation in other embryonal tumors with concomitant expression of stem-cell markers may facilitate HML-2 expression. Future studies could utilize HML-2 as potential diagnostic criteria, use its expression as a treatment biomarker, and investigate the efficacy of therapies targeting cells with high HML-2 expression.

Clinical evidence for a biological effect of epigenetically active decitabine in relapsed or progressive rhabdoid tumors

BACKGROUND

Refined therapy has helped to improve survival rates in rhabdoid tumors (RT). Prognosis for patients with chemoresistant, recurrent, or progressive RT remains dismal. Although decitabine, an epigenetically active agent, has mainly been evaluated in the management of hematologic malignancies in adults, safety in children has also been demonstrated repeatedly.

MATERIALS AND METHODS

A retrospective series of patients who received decitabine upon relapse or progression following therapy according to the EU-RHAB regimen is presented. Due to the retrospective nature of analyses, response was defined as measurable regression of at least one lesion on imaging. 850k methylation profiling was done whenever tumor tissue was available.

RESULTS

A total of 22 patients with RT of any anatomical localization were included. Most patients (19/22) presented with metastases. All received low-dose decitabine with or preceding conventional chemotherapy. Patients received a median of two (1-6) courses of decitabine; 27.3% (6/22) demonstrated a radiological response. Molecular analyses revealed increased methylation levels in tumors from responders. No excessive toxicity was observed. Clinical benefits for responders included eligibility for early phase trials or local therapy. Responders showed prolonged time to progression and overall survival. Due to small sample size, statistical correction for survivorship bias demonstrated no significant effect on survival for responders.

CONCLUSIONS

Patients with RT demonstrate promising signs of antitumor activity after multiagent relapse therapy including decitabine. Analyses of methylation data suggest a specific effect on an epigenetic level. We propose to consider decitabine and other epigenetic drugs as candidates for further clinical investigations in RT.

Methylation Drivers and Prognostic Implications in Sinonasal Poorly Differentiated Carcinomas

Simple Summary

Poorly differentiated sinonasal carcinomas (PDSNCs) are rare neoplasms that include a wide spectrum of malignancies characterized by alteration in different epigenetic mechanisms (SWI/SNF complex, IDH2, NUT). The aim of our study was to verify if the identification of specific genetic and epigenetic alterations can be useful to recognize different clinico-pathological subsets of PDSNCs to guide treatment decisions. In our cohort, 14 cases showed alterations in SWI/SNF complex or IDH2 genes, which were associated with a higher global DNA methylation level and worst prognosis. The integration of genetic and epigenetic features appears to be a good strategy to improve the clinico-pathological classification of these tumors and to recognize distinct prognostic entities that deserve tailored clinical management.

Abstract

Background: Poorly differentiated sinonasal carcinomas (PDSNCs) are rare and aggressive malignancies, which include squamous cell carcinoma (SCC), sinonasal undifferentiated carcinoma (SNUC), and neuroendocrine carcinomas (NEC). Several epigenetic markers have been suggested to support the histopathological classification, predict prognosis, and guide therapeutic decision. Indeed, molecularly distinct subtypes of sinonasal carcinomas, including SMARCB1-INI1 or SMARCA4 deficient sinonasal carcinoma, isocitrate dehydrogenase (IDH)-mutant SNUC, ARID1A mutant PDSNCs, and NUT carcinomas, have recently been proposed as separate entities. Identification of aberrant DNA methylation levels associated with these specific epigenetic driver genes could be useful for prognostic and therapeutic purpose. Methods: Histopathological review and immunohistochemical study was performed on 53 PDSNCs. Molecular analysis included mutational profile by NGS, Sanger sequencing, and MLPA analyses, and global DNA methylation profile using LINE-1 bisulfite-PCR and pyrosequencing analysis. Results: Nine SWI/SNF complex defective cases and five IDH2 p.Arg172x cases were identified. A significant correlation between INI-1 or IDH2 defects and LINE-1 hypermethylation was observed (p = 0.002 and p = 0.032, respectively), which were associated with a worse prognosis (p = 0.007). Conclusions: Genetic and epigenetic characterization of PDSNCs should be performed to identify distinct prognostic entities, which deserved a tailored clinical treatment.

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

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

Histone deacetylase inhibitor panobinostat induces antitumor activity in epithelioid sarcoma and rhabdoid tumor by growth factor receptor modulation

Background

Epithelioid sarcomas and rhabdoid tumors are rare, aggressive malignancies with poor prognosis. Both are characterized by INI1 alterations and deregulation of growth factor receptors albeit their interaction has not been elucidated.

Methods

In this study, we investigated the activity of a panel of epigenetic modulators and receptor tyrosine kinase inhibitors in vitro on respective cell lines as well as on primary patient-derived epithelioid sarcoma cells, and in vivo on xenografted mice. Focusing on histone deacetylase (HDAC) inhibitors, we studied the mechanism of action of this class of agents, its effect on growth factor receptor regulation, and changes in epithelial-to-mesenchymal transition by using cell- and RT-qPCR-based assays.

Results

Pan-HDAC inhibitor panobinostat exhibited potent anti-proliferative activity at low nanomolar concentrations in A204 rhabdoid tumor, and VAESBJ/GRU1 epithelioid sarcoma cell lines, strongly induced apoptosis, and resulted in significant tumor growth inhibition in VAESBJ xenografts. It differentially regulated EGFR, FGFR1 and FGFR2, leading to downregulation of EGFR in epithelioid sarcoma and to mesenchymal-to-epithelial transition whereas in rhabdoid tumor cells, EGFR was strongly upregulated and reinforced the mesenchymal phenotype. All three cell lines were rendered more susceptible towards combination with EGFF inhibitor erlotinib, further enhancing apoptosis.

Conclusions

HDAC inhibitors exhibit significant anticancer activity due to their multifaceted actions on cytotoxicity, differentiation and drug sensitization. Our data suggest that the tailored, tissue-specific combination of HDAC inhibitors with therapeutics which target cellular salvage mechanisms might increase their therapeutic relevance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08579-w.

Uncommon and peculiar soft tissue sarcomas: Multidisciplinary review and practical recommendations. Spanish Group for Sarcoma research (GEIS -GROUP). Part II

Among all Soft Tissue sarcomas there are some subtypes with low incidence and/or peculiar clinical behaviour, that need to be consider separately. Most of them are orphan diseases, whose biological characteristics imply a clearly different diagnostic and therapeutic approach from other more common sarcoma tumors. We present a brief and updated multidiciplinary review, focused on practical issues, aimed at helping clinicians in decision making. In this second part we review these subtypes: Alveolar Soft Part Sarcoma, Epithelioid Sarcoma, Clear Cell Sarcoma, Desmoplastic Small Round Cell Tumor, Rhabdoid Tumor, Phyllodes Tumor, Tenosynovial Giant Cell Tumors, Myoepithelial Tumor, Perivascular Epithelioid Cell Neoplasms (PEComas), Extraskeletal Myxoid Chondrosarcoma, NTRK-fusions Sarcomas. Most of them present their own radiological and histopathological feautures, that are essential to know in order to achieve early diagnosis. In some of them, molecular diagnosis is mandatory, not only in the diagnosis, but also to plan the treatment. On the other hand, and despite the low incidence, a great scientific research effort has been made to achieve new treatment opportunities for these patients even with approved indications. These include new treatments with targeted therapies and immunotherapy, which today represent possible therapeutic options. It is especially important to be attentive to new and potential avenues of research, and to promote the conduct of specific clinical trials for rare sarcomas.

SMARCB1 deletion in atypical teratoid rhabdoid tumors results in human endogenous retrovirus K (HML-2) expression

Atypical Teratoid Rhabdoid Tumor (AT/RT) is a rare pediatric central nervous system cancer often characterized by deletion or mutation of SMARCB1, a tumor suppressor gene. In this study, we found that SMARCB1 regulates Human Endogenous Retrovirus K (HERV-K, subtype HML-2) expression. HML-2 is a repetitive element scattered throughout the human genome, encoding several intact viral proteins that have been associated with stem cell maintenance and tumorigenesis. We found HML-2 env expression in both the intracellular and extracellular compartments in all AT/RT cell lines (n = 4) and in 95% of AT/RT patient tissues (n = 37) evaluated. SMARCB1 knock-down in neural stem cells (NSCs) led to an upregulation of HML-2 transcription. We found that SMARCB1 binds adjacent to the HML-2 promoter, repressing its transcription via chromatin immunoprecipitation; restoration of SMARCB1 expression in AT/RT cell lines significantly downregulated HML-2 expression. Further, targeted downregulation of HML-2 transcription via CRISPR-dCas9 coupled with suppressor proteins led to cellular dispersion, decreased proliferation, and cell death in vitro. HML-2 knock-down with shRNA, siRNA, and CRISPR-dCas9 significantly decreased Ras expression as measured by qRT-PCR, suggesting that HML-2 modulates MAPK/ERK signaling in AT/RT cells. Overexpression of NRAS was sufficient to restore cellular proliferation, and MYC, a transcription factor downstream of NRAS, was bound to the HERV-K LTR significantly more in the absence of SMARCB1 expression in AT/RT cells. We show a mechanism by which these undifferentiated tumors remain pluripotent, and we demonstrate that their formation is aided by aberrant HML-2 activation, which is dependent on SMARCB1 and its interaction with MYC.

Polo-Like Kinase 4's Critical Role in Cancer Development and Strategies for Plk4-Targeted Therapy

Polo-like kinases (Plks) are critical regulatory molecules during the cell cycle process. This family has five members: Plk1, 2, 3, 4, and 5. Plk4 has been identified as a master regulator of centriole replication, and its aberrant expression is closely associated with cancer development. In this review, we depict the DNA, mRNA, and protein structure of Plk4, and the regulation of Plk4 at a molecular level. Then we list the downstream targets of Plk4 and the hallmarks of cancer associated with these targets. The role of Plk4 in different cancers is also summarized. Finally, we review the inhibitors that target Plk4 in the hope of discovering effective anticancer drugs. From authors' perspective, Plk4 might represent a valuable tumor biomarker and critical target for cancer diagnosis and therapy.

Rhabdoid Tumor Predisposition Syndrome: From Clinical Suspicion to General Management

Rhabdoid tumors are rare aggressive malignancies in infants and young children with a poor prognosis. The most common anatomic localizations are the central nervous system, the kidneys, and other soft tissues. Rhabdoid tumors share germline and somatic mutations in SMARCB1 or, more rarely, SMARCA4, members of the SWI/SNF chromatin-remodeling complex. Rhabdoid tumor predisposition syndrome (RTPS) is a condition characterized by a high risk of developing rhabdoid tumors, among other features. RTPS1 is characterized by pathogenic variants in the SMARCB1 gene, while RTPS2 has variants in SMARCA4. Interestingly, germline variants of SMARCB1 and SMARCA4 have been identified also in patients with Coffin-Siris syndrome. Children with RTPS typically present with tumors before 1 year of age and in a high percentage of cases develop synchronous or multifocal tumors with aggressive clinical features. The diagnosis of RTPS should be considered in patients with rhabdoid tumors, especially if they have multiple primary tumors and/or in individuals with a family history. Because germline mutations result in an increased risk of carriers developing rhabdoid tumors, genetic counseling, and surveillance for all family members with this condition is recommended.

Potential of enhancer of zeste homolog 2 inhibitors for the treatment of SWI/SNF mutant cancers and tumor microenvironment modulation

Enhancer of zeste homolog 2 (EZH2), a catalytic component of polycomb repressive complex 2 (PRC2), is commonly overexpressed or mutated in many cancer types, both of hematological and solid nature. Till now, plenty of EZH2 small molecule inhibitors have been developed and some of them have already been tested in clinical trials. Most of these inhibitors, however, are effective only in limited cases in the context of EZH2 gain-of-function mutated tumors such as lymphomas. Other cancer types with aberrant EZH2 expression and function require alternative approaches for successful treatment. One possibility is to exploit synthetic lethal strategy, which is based on the phenomenon that concurrent loss of two genes is detrimental but the deletion of either of them leaves cell viable. In the context of EZH2/PRC2, the most promising synthetic lethal target seems to be SWItch/Sucrose Non-Fermentable chromatin remodeling complex (SWI/SNF), which is known to counteract PRC2 functions. SWI/SNF is heavily involved in carcinogenesis and its subunits have been found mutated in approximately 20% of tumors of different kinds. In the current review, we summarize the existing knowledge of synthetic lethal relationships between EZH2/PRC2 and components of the SWI/SNF complex and discuss in detail the potential application of existing EZH2 inhibitors in cancer patients harboring mutations in SWI/SNF proteins. We also highlight recent discoveries of EZH2 involvement in tumor microenvironment regulation and consequences for future therapies. Although clinical studies are limited, the fundamental research might help to understand which patients are most likely to benefit from therapies using EZH2 inhibitors.

Clinical and genetic risk factors define two risk groups of extracranial malignant rhabdoid tumours (eMRT/RTK)

INTRODUCTION

Extracranial rhabdoid tumours are rare, highly aggressive malignancies primarily affecting young children. The EU-RHAB registry was initiated in 2009 to prospectively collect data of rhabdoid tumour patients treated according to the EU-RHAB therapeutic framework.

METHODS

We evaluated 100 patients recruited within EU-RHAB (2009-2018). Tumours and matching blood samples were examined for SMARCB1 mutations by sequencing and cytogenetics.

RESULTS

A total of 70 patients presented with extracranial, extrarenal tumours (eMRT) and 30 with renal rhabdoid tumours (RTK). Nine patients demonstrated synchronous tumours. Distant metastases at diagnosis (M+) were present in 35% (35/100), localised disease (M0) with (LN+) and without (LN-) loco-regional lymph node involvement in 65% (65/100). SMARCB1 germline mutations (GLM) were detected in 21% (17/81 evaluable) of patients. The 5-year overall survival (OS) and event-free survival (EFS) rates were 45.8 ± 5.4% and 35.2 ± 5.1%, respectively. On univariate analyses, age at diagnosis (≥12 months), M0-stage, absence of synchronous tumours, absence of a GLM, gross total resection (GTR), radiotherapy and achieving a CR were significantly associated with favourable outcomes. In an adjusted multivariate model presence of a GLM, M+ and lack of a GTR were the strongest significant negative predictors of outcome.

CONCLUSIONS

We suggest to stratify patients with localised disease (M0), GTR+ and without proof of a GLM (5-year OS 72.2 ± 9.9%) as 'standard risk'. Patients presenting with one of the features M+ and/or GTR- and/or GLM+ belong to a high risk group (5-year, OS 32.5 ± 6.2%). These patients need novel therapeutic strategies such as combinations of targeted agents with conventional chemotherapy or novel experimental approaches ideally within international phase I/II trials.

Pediatric Renal Tumors: Updates in the Molecular Era

Molecular characterization has led to advances in the understanding of pediatric renal tumors, including the association of pediatric cystic nephromas with DICER1 tumor syndrome, the metanephric family of tumors with somatic BRAF mutations, the characterization of ETV6-NTRK3-negative congenital mesoblastic nephromas, the expanded spectrum of gene fusions in translocation renal cell carcinoma, the relationship of clear cell sarcoma of the kidney with other BCOR-altered tumors, and the pathways affected by SMARCB1 alterations in rhabdoid tumors of the kidney. These advances have implications for diagnosis, classification, and treatment of pediatric renal tumors.

Novel Biomarkers in Sinonasal Cancers: from Bench to Bedside

PURPOSE OF REVIEW

Sinonasal cancers are a heterogenous group of rare cancers for which histopathological diagnosis can be very challenging and treatment options are limited for advanced disease in particular. Here, we review the candidacy of novel diagnostic and prognostic biomarkers, and therapeutic targets for sinonasal cancers.

RECENT FINDINGS

Molecular multidimensional analyses of sinonasal cancers have been lagging behind other major cancers, but there are numerous publications describing the discovery of novel candidate biomarkers, e.g. the methylation classifier, originally developed for brain cancers, and gene expression panels for the prediction of response to induction chemotherapy in sinonasal undifferentiated carcinoma. The most promising biomarkers are summarized and discussed further with regard to their clinical applicability and future potential. Many of the described novel biomarkers for sinonasal cancers will eventually overcome the pitfalls associated with the frequently non-specific immunohistological tests. With comprehensive, multidimensional molecular testing of these tumours in collaborative consortia projects, our better understanding of the molecular mechanisms of sinonasal cancers and their carcinogenesis will determine the most useful diagnostic and prognostic biomarkers, allow stringent multi-institutional validation and guide trials on targeted therapies.

Survival of Patients With Non-Rhabdomyosarcoma Soft Tissue Sarcomas of the Head and Neck

OBJECTIVE

To evaluate factors associated with overall survival (OS) of patients with non-rhabdomyosarcoma soft tissue sarcomas of the head and neck.

STUDY DESIGN

Retrospective cohort study.

METHODS

The National Cancer Database was queried for cases of non-rhabdomyosarcoma soft tissue sarcomas of the head and neck between 2004 and 2014. Cases were categorized according to the World Health Organization classification of soft tissue tumors. A multivariable Cox proportional hazards model was used to evaluate associations with OS.

RESULTS

A total of 4,555 patients (63.6% male, 36.4% female, mean age 59.6 years) met inclusion criteria. The majority of tumors were classified as miscellaneous (35.9%), followed by vascular (20.1%), smooth muscle (13.5%), fibroblastic/myofibroblastic (12.1%), peripheral nerve (8.5%), adipocytic (7.4%), and undifferentiated (2.5%) sarcomas. The mean follow-up was 37.9 months, and overall mortality (MR) was 45.3%. The best prognosis was seen with fibroblastic/myofibroblastic sarcomas (MR = 20.6%, P < .001), whereas vascular sarcomas had the worst prognosis (MR = 67.6%, P < .001). Resection with clear margins had better OS than microscopically positive margins (hazard ratio [HR] = 1.43, P < .001) or grossly positive margins (HR = 2.97, P < .001). Radiation therapy was associated with better OS than no radiation (HR = 0.86, P = .001).

CONCLUSION

Non-rhabdomyosarcoma soft tissue sarcomas of the head and neck are associated with significant mortality. OS differs based on histologic subcategorization. Resection of the primary tumor with clear margins demonstrates improved OS for all histologies, suggesting this modality remains the preferred primary treatment when feasible.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:E500-E508, 2021.

Multimodal Management of Congenital Orbital Malignant Rhabdoid Tumor: Review of Literature and Report of a Rare Case

BACKGROUND

Malignant rhabdoid tumor (MRT) is a rare and aggressive tumor with a dismal prognosis. It commonly arises in the brain (65%), soft tissues (26%), and the kidney (9%). Primary orbital involvement is extremely rare. Although it has been mostly described in children below 2 years old, presentation at birth is sparsely reported.

OBSERVATION

We have described a case of congenital orbital MRT, who presented with rapidly progressive right-sided proptosis and was initially treated with subtotal resection and postoperative chemotherapy with ICE (Ifosfamide, Carboplatin, Etoposide) regimen. On local progression the child was treated with palliative radiotherapy (20 Gy) to the right orbit and second-line chemotherapy with VAC (Vincristine, Adriamycin, Cyclophosphamide) regimen. Unfortunately he died due to progressive disease 4 months after the initial diagnosis.

CONCLUSIONS

This report highlights the importance of awareness of orbital MRT as a differential diagnosis of rapidly progressing proptosis in the neonatal period. This tumor is often refractory to conventional multimodality treatment and more intensive and innovative treatment approaches are clearly needed in future.

Translational genomics of malignant rhabdoid tumours: Current impact and future possibilities

Malignant Rhabdoid Tumours (MRT) are the quintessential example of an epigenetic cancer. Mutation of a single gene, SMARCB1 or more rarely SMARCA4, is capable of causing one of the most aggressive and lethal cancers of early childhood and infancy. SMARCB1 encodes a core subunit of the SWI/SNF complex and its mutation evokes genome-wide downstream effects which may be counteracted therapeutically. Here we review and discuss the use of translational genomics in the study of MRT biology and the ways in which this has impacted clinical practice or may do so in the future. First, the diagnosis and definition of MRT and the transition from a histopathological to a molecular definition. Second, epigenetic and transcriptomic subgroups within MRT, their defining features and potential prognostic or therapeutic significance. Third, functional genomic studies of MRT by mouse modelling and forced re-expression of SMARCB1 in MRT cells. Fourth, studies of underlying epigenetic mechanisms (e.g. EZH2, HDACs) or deregulated kinases (e.g. PDGFR, FGFR1) and the potential therapeutic opportunities these provide. Finally, we discuss likely future directions and proffer opinion on how future translational genomics should be integrated into future biological/clinical studies to select and evaluate the best anti-MRT therapeutic agents.

B7-H3 as a Prognostic Biomarker and Therapeutic Target in Pediatric central nervous system Tumors

B7–H3 (CD276), a member of the B7 superfamily, is an important factor in downregulating immune responses against tumors. It is also aberrantly expressed in many human malignancies. Beyond immune regulatory roles, its overexpression has been linked to invasive metastatic potential and poor prognosis in patients with cancer. Antibody-dependent cell-mediated cytotoxicity strategies targeting B7–H3 are currently in development, and early-phase clinical trials have shown encouraging preliminary results.

To understand the role of B7–H3 in pediatric central nervous system (CNS) malignancies, a comprehensive panel of primary CNS tumors of childhood was examined by immunohistochemistry for levels and extent of B7–H3 expression. In addition, B7–H3 m-RNA expression status and association with overall survival in various pediatric CNS tumor types was accessed by curating publicly available patient gene expression data sets derived from bioinformatics analysis and visualization platforms (GlioVis).

We demonstrate that B7–H3 is broadly expressed in pediatric glial and nonglial CNS tumors, and its aberrant expression, as determined by immunohistochemical staining intensity, correlates with tumor grade. Moreover, high B7–H3 m-RNA expression is significantly associated with worse survival and could potentially improve prognostication in various brain tumor types of childhood. B7–H3 can be used as a therapeutic target, given its tumor selectivity and the availability of targeted therapeutic agents to this antigen.

Identification and Analyses of Extra-Cranial and Cranial Rhabdoid Tumor Molecular Subgroups Reveal Tumors with Cytotoxic T Cell Infiltration

Extra-cranial malignant rhabdoid tumors (MRTs) and cranial atypical teratoid RTs (ATRTs) are heterogeneous pediatric cancers driven primarily by SMARCB1 loss. To understand the genome-wide molecular relationships between MRTs and ATRTs, we analyze multi-omics data from 140 MRTs and 161 ATRTs. We detect similarities between the MYC subgroup of ATRTs (ATRT-MYC) and extra-cranial MRTs, including global DNA hypomethylation and overexpression of HOX genes and genes involved in mesenchymal development, distinguishing them from other ATRT subgroups that express neural-like features. We identify five DNA methylation subgroups associated with anatomical sites and SMARCB1 mutation patterns. Groups 1, 3, and 4 exhibit cytotoxic T cell infiltration and expression of immune checkpoint regulators, consistent with a potential role for immunotherapy in rhabdoid tumor patients.

Chromosomal Heterogeneity of the G-401 Rhabdoid Tumor Cell Line: Unusual Partial 7p Trisomy

Rhabdoid tumor is a very aggressive and hardly curable pediatric malignancy. It commonly starts in the kidneys but also can occur in the brain, liver, and other organs. The treatment of this tumor usually involves a combination of surgery, radiation, and chemotherapy. Because this tumor is rare, there is still limited experience with a defined standard of care. Cytogenetic analysis is an important routine method to monitor chromosomal aberrations. We have analyzed metaphases of the G-401 rhabdoid tumor cell line. In these cells we have observed metaphases with derivative chromosome 12 arising from partial trisomy 7p. With increasing passage number the numbers of metaphases having this derivative chromosome 12 were found to be higher. In passage number 2 only one metaphase had this pathological chromosome 12. By passage number 10 and passage number 15 about 25 and 95% of this derivative chromosome 12 were found, respectively. We were able to subclone G-401 cells by limiting dilutions and successfully separated cells having apparently normal karyotypes from cells having derivative chromosome 12. Using the cell proliferation assay we showed that clones possessing the derivative chromosome 12 grew more rapidly than clones with normal chromosomes. The cell cycle analysis confirmed this observation. Overall, in this study we describe for the first time a 7p triplication in a rare rhabdoid tumor of kidney. Both types of clones described in this study could be used as a preclinical model to study the involvement of partial chromosome 7 alterations in the development of rhabdoid tumors.

Remodeling the cancer epigenome: mutations in the SWI/SNF complex offer new therapeutic opportunities

INTRODUCTION

Cancer genome sequencing studies have discovered mutations in members of the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin-remodeling complex in nearly 25% of human cancers. The SWI/SNF complex, first discovered in S. cerevisiae, shows strong conservation from yeast to Drosophila to mammals, contains approximately 10-12 subunits and regulates nucleosome positioning through the energy generated by its ATPase subunits. The unexpected finding of frequent mutations in the complex has fueled studies to identify the mechanisms that drive tumor development and the accompanying therapeutic vulnerabilities. Areas covered: In the review, we focus upon the potential roles different SWI/SNF subunit mutations play in human oncogenesis, their common and unique mechanisms of transformation and the potential for translating these mechanisms into targeted therapies for SWI/SNF-mutant tumors. Expert opinion: We currently have limited insights into how mutations in different SWI/SNF subunits drive the development of human tumors. Because the SWI/SNF complex participates in a broad range of normal cellular functions, defining specific oncogenic pathways has proved difficult. In addition, therapeutic options for SWI/SNF-mutant cancers have mainly evolved from high-throughput screens of cell lines with mutations in different subunits. Future studies should follow a more coherent plan to pinpoint common vulnerabilities among these tumors.

Evaluation of Protein Kinase Inhibitors with PLK4 Cross-Over Potential in a Pre-Clinical Model of Cancer

Polo-like kinase 4 (PLK4) is a cell cycle-regulated protein kinase (PK) recruited at the centrosome in dividing cells. Its overexpression triggers centrosome amplification, which is associated with genetic instability and carcinogenesis. In previous work, we established that PLK4 is overexpressed in pediatric embryonal brain tumors (EBT). We also demonstrated that PLK4 inhibition exerted a cytostatic effect in EBT cells. Here, we examined an array of PK inhibitors (CFI-400945, CFI-400437, centrinone, centrinone-B, R-1530, axitinib, KW-2449, and alisertib) for their potential crossover to PLK4 by comparative structural docking and activity inhibition in multiple established embryonal tumor cell lines (MON, BT-12, BT-16, DAOY, D283). Our analyses demonstrated that: (1) CFI-400437 had the greatest impact overall, but similar to CFI-400945, it is not optimal for brain exposure. Also, their phenotypic anti-cancer impact may, in part, be a consequence of the inhibition of Aurora kinases (AURKs). (2) Centrinone and centrinone B are the most selective PLK4 inhibitors but they are the least likely to penetrate the brain. (3) KW-2449, R-1530 and axitinib are the ones predicted to have moderate-to-good brain penetration. In conclusion, a new selective PLK4 inhibitor with favorable physiochemical properties for optimal brain exposure can be beneficial for the treatment of EBT.

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.