Transgenic mice expressing PAX3-FKHR have multiple defects in muscle development, including ectopic skeletal myogenesis in the developing neural tube

The t(2;13) chromosomal translocation is found in the majority of human alveolar rhabdomyosarcomas (RMS). The resulting PAX3-FKHR fusion protein contains PAX3 DNA-binding domains fused to the potent transactivation domain of FKHR, suggesting that PAX3-FKHR functions to deregulate PAX3-specific target genes and signaling pathways. We previously developed transgenic mice expressing PAX3-FKHR under the control of mouse Pax3 regulatory sequences to test this hypothesis. We reported that PAX3-FKHR interferes with normal Pax3 developmental functions, with mice exhibiting neural tube and neural crest abnormalities that mimic those found in Pax3-deficient Splotch mice. Here we expanded those studies to show that developmental expression of PAX3-FKHR results in aberrant myogenesis in the developing somites and neural tube, leading to ectopic skeletal muscle formation in the mature spinal cord. Gene expression profiling indicated that PAX3-FKHR expression in the developing neural tube induces a myogenic pattern of gene expression at the expense of the normal neurogenic program. Somite defects in PAX3-FKHR transgenic animals resulted in skeletal malformations that included rib fusions and mis-attachments. As opposed to the neural tube defects, the severity of the rib phenotype was rescued by reducing Pax3 levels through mating with Splotch mice. Embryos from the transgenic line expressing the highest levels of PAX3-FKHR had severe neural tube defects, including exencephaly, and almost half of the embryos died between gestational ages E13.5-E15.5. Nearly all of the embryos that survived to term died after birth due to severe spina bifida, rather than the absence of a muscular diaphragm. These studies reveal a prominent role for PAX3-FKHR in disrupting Pax3 functions and in deregulating skeletal muscle development, suggesting that this fusion protein plays a critical role in the pathogenesis of␣alveolar RMS by influencing the commitment␣and differentiation of the myogenic cell lineage.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

Pax3-FKHR knock-in mice show developmental aberrations but do not develop tumors

Alveolar rhabdomyosarcoma is a pediatric disease specified by the recurrent chromosome translocations t(2;13) and t(1;13). These translocations result in the formation of the PAX3-FKHR and PAX7-FKHR fusion genes, which are thought to play a causal role in the genesis of this disease. Although PAX3-FKHR exhibits transforming activity in immortalized fibroblast cell lines, a direct role of this fusion protein in tumorigenesis in vivo has not been shown. We determined whether expression of Pax3-FKHR in the mouse germ line would render these animals prone to the development of rhabdomyosarcomas. By targeting FKHR cDNA sequences into the Pax3 locus of embryonic stem cells, we used these cells to generate mice carrying a Pax3-FKHR knock-in allele. Despite low expression of the knock-in allele, heterozygous offspring of Pax3-FKHR chimeric mice showed developmental abnormalities. These included intraventricular septum defects, tricuspid valve insufficiency, and diaphragm defects, which caused congestive heart failure leading to perinatal death. In addition, Pax3-FKHR heterozygous offspring displayed malformations of some but not all hypaxial muscles. However, neither newborn heterozygous pups nor their chimeric parents showed any signs of malignancy. We conclude that the Pax3-FKHR allele causes lethal developmental defects in knock-in mice but might be insufficient to cause muscle tumors.     

Malignant rhabdoid tumor of the kidney in a child: report of a case with recurrence in the contralateral kidney

BACKGROUND: Malignant rhabdoid tumor (MRT) of the kidney is a rare and aggressive neoplasm with a controversial histogenesis. Although their immunohistochemistry may be diverse, the rhabdoid phenotype and mutations of the INI1 gene are consistently exhibited by MRTs regardless of their location. CASE: MRT recurred in the contralateral kidney in a 12-month-old child within 6 months after the initial histologic diagnosis, nephrectomy and autologous stem cell transplant. The presence of widespread metastases at the time of the recurrence precluded any further chemical and surgical diagnostic or therapeutic intervention. CONCLUSION: To the best of our knowledge, only a few cases describing the cytologic diagnosis of MRT of the kidney in a child have been reported. This case illustrates the usefulness of cytologic diagnosis in an MRT recurrence.     

Fibroblast Growth Factor Receptors as Novel Therapeutic Targets in SNF5-Deleted Malignant Rhabdoid Tumors

Malignant rhabdoid tumors (MRTs) are aggressive pediatric cancers arising in brain, kidney and soft tissues, which are characterized by loss of the tumor suppressor SNF5/SMARCB1. MRTs are poorly responsive to chemotherapy and thus a high unmet clinical need exists for novel therapies for MRT patients. SNF5 is a core subunit of the SWI/SNF chromatin remodeling complex which affects gene expression by nucleosome remodeling. Here, we report that loss of SNF5 function correlates with increased expression of fibroblast growth factor receptors (FGFRs) in MRT cell lines and primary tumors and that re-expression of SNF5 in MRT cells causes a marked repression of FGFR expression. Conversely, siRNA-mediated impairment of SWI/SNF function leads to elevated levels of FGFR2 in human fibroblasts. In vivo, treatment with NVP-BGJ398, a selective FGFR inhibitor, blocks progression of a murine MRT model. Hence, we identify FGFR signaling as an aberrantly activated oncogenic pathway in MRTs and propose pharmacological inhibition of FGFRs as a potential novel clinical therapy for MRTs.     

Malignant rhabdoid tumor in the renal allograft of an adult transplant recipient: a unique case of a rare tumor

Background

Renal transplant recipients have increased risk for developing malignant diseases because of immunosuppression or donor-to-recipient transmission. Malignant rhabdoid tumor (MRT) is a rare, highly aggressive and lethal tumor primarily affecting the kidney of infants and young children. MRT has not been reported in the renal allograft of an adult recipient after kidney transplantation.

Case presentation

In this report, a 47-year-old woman who received a kidney transplantation from an infant donor and developed a mass in the transplanted kidney is presented. Pathological examinations revealed a malignant tumor with rhabdoid cells morphologically and the loss of INI1 expression immunohistochemically. The diagnosis of malignant rhabdoid tumor in the transplanted kidney was made. We confirmed that donor-to-recipient malignancy transmission was the cause of MRT in the transplanted kidney by fluorescence in situ hybridization (FISH) and short tandem repeat (STR) analysis.

Conclusion

To our knowledge, this is the first case of MRT in an adult renal allograft recipient. This report highlights the importance of the criteria for selection of donors to screen possible malignant tumors transmission.

     

Structural and Functional Studies of FKHR-PAX3, a Reciprocal Fusion Gene of the t(2;13) Chromosomal Translocation in Alveolar Rhabdomyosarcoma

Alveolar rhabdomyosarcoma (ARMS) is an aggressive pediatric cancer of skeletal muscle. More than 70% of ARMS tumors carry balanced t(2;13) chromosomal translocation that leads to the production of two novel fusion genes, PAX3-FKHR and FKHR-PAX3. While the PAX3-FKHR gene has been intensely studied, the reciprocal FKHR-PAX3 gene has rarely been described. We report here the cloning and functional characterization of the FKHR-PAX3 gene as the first step towards a better understanding of its potential impact on ARMS biology. From RH30 ARMS cells, we detected and isolated three versions of FKHR-PAX3 cDNAs whose C-terminal sequences corresponded to PAX3c, PAX3d, and PAX3e isoforms. Unlike the nuclear-specific localization of PAX3-FKHR, the reciprocal FKHR-PAX3 proteins stayed predominantly in the cytoplasm. FKHR-PAX3 potently inhibited myogenesis in both non-transformed myoblast cells and ARMS cells. We showed that FKHR-PAX3 was not a classic oncogene but could act as a facilitator in oncogenic pathways by stabilizing PAX3-FKHR expression, enhancing cell proliferation, clonogenicity, anchorage-independent growth, and matrix adhesion in vitro, and accelerating the onset of tumor formation in xenograft mouse model in vivo. In addition to these pro-oncogenic behaviors, FKHR-PAX3 also negatively affected cell migration and invasion in vitro and lung metastasis in vivo. Taken together, these functional characteristics suggested that FKHR-PAX3 might have a critical role in the early stage of ARMS development.     

Differential expression of miRNAs in rhabdomyosarcoma and malignant rhabdoid tumor

Alveolar rhabdomyosarcoma (RMA) and malignant rhabdoid tumor (MRT) have a frequent metastatic spread and a poor prognosis. Aberrant miRNA expression is often found in metastatic tumors. The aim of this study was to identify specific miRNA expression patterns in these tumors. We analyzed the expression of miRNAs in RMA and MRT in tissue samples and in the rhabdomyosarcoma (RMS) cell lines (Rh30 and RD). Selected target miRNAs were modulated with mimic or inhibitor oligonucleotides. Functional analysis was monitored by flow cytometry and migration assays. A set of 107 differentially expressed miRNAs showed tissue-specific clustering of RMA and MRT. Comparison with the Sarcoma microRNA Expression Database revealed RMA- and MRT-specific miRNAs. Metastatic invasion associated miRNA miR-9^? was overexpressed in RMA. miR-200c—inhibiting migration—was lower expressed in RMA than in MRT. Transient transfection of RMS cells with a miR-200c mimic and miR-9^* inhibitor did neither increase the expression of the known target E-cadherin nor decrease migration. Expression of E-cadherin could be induced in RD cells using decitabine, but demethylation did not influence cell migration. Despite a comparable high rate of metastatic invasion pediatric RMA and MRT show a different pattern of miRNA expression possibly allowing risk stratification.     

Hyper-Activation of Notch3 Amplifies the Proliferative Potential of Rhabdomyosarcoma Cells

Rhabdomyosarcoma (RMS) is a pediatric myogenic-derived soft tissue sarcoma that includes two major histopathological subtypes: embryonal and alveolar. The majority of alveolar RMS expresses PAX3-FOXO1 fusion oncoprotein, associated with the worst prognosis. RMS cells show myogenic markers expression but are unable to terminally differentiate. The Notch signaling pathway is a master player during myogenesis, with Notch1 activation sustaining myoblast expansion and Notch3 activation inhibiting myoblast fusion and differentiation. Accordingly, Notch1 signaling is up-regulated and activated in embryonal RMS samples and supports the proliferation of tumor cells. However, it is unable to control their differentiation properties. We previously reported that Notch3 is activated in RMS cell lines, of both alveolar and embryonal subtype, and acts by inhibiting differentiation. Moreover, Notch3 depletion reduces PAX3-FOXO1 alveolar RMS tumor growth in vivo. However, whether Notch3 activation also sustains the proliferation of RMS cells remained unclear. To address this question, we forced the expression of the activated form of Notch3, Notch3IC, in the RH30 and RH41 PAX3-FOXO1-positive alveolar and in the RD embryonal RMS cell lines and studied the proliferation of these cells. We show that, in all three cell lines tested, Notch3IC over-expression stimulates in vitro cell proliferation and prevents the effects of pharmacological Notch inhibition. Furthermore, Notch3IC further increases RH30 cell growth in vivo. Interestingly, knockdown of Notch canonical ligands JAG1 or DLL1 in RMS cell lines decreases Notch3 activity and reduces cell proliferation. Finally, the expression of Notch3IC and its target gene HES1 correlates with that of the proliferative marker Ki67 in a small cohort of primary PAX-FOXO1 alveolar RMS samples. These results strongly suggest that high levels of Notch3 activation increase the proliferative potential of RMS cells.     

膀胱尿路上皮肿瘤合并2型糖尿病患者临床和病理特点的比较性研究

目的:对比分析膀胱尿路上皮肿瘤合并2型糖尿病患者的临床和病理特点,为临床诊疗工作提供一定的参考。方法:回顾性分析2015年1月至2019年2月于我院泌尿外科手术治疗且经病理确诊为原发性膀胱尿路上皮肿瘤的患者资料,合并2型糖尿病的膀胱肿瘤患者59例设为糖尿病组(T2DM组),根据性别和年龄按照1:2的比例匹配同时期未合并2型糖尿病的膀胱肿瘤118例患者为非糖尿病组(NT2DM组),比较两组患者的临床特征和病理特点。结果:T2DM组的高血压患者比例和血肌酐值高于NT2DM组(P<0.05),而在教育程度、吸烟、饮酒、BMI、前列腺增生、泌尿系感染、血常规、肝功、尿常规、肿瘤大小、数量方面无明显统计学差异(P>0.05)。T2DM组和NT2DM组在膀胱尿路上皮肿瘤良恶性分类、肿瘤数量、肿瘤大小的构成比上无明显统计学差异(P>0.05);然而,对膀胱恶性肿瘤患者进行亚组分析显示,T2DM亚组中肌层浸润性癌的比例和高级别癌的比例明显高于NT2DM亚组,差异有统计学意义(P<0.05)。结论:2型糖尿病可能使膀胱癌的病理分级和分期更高,导致患者预后更差,临床上应更加关注膀胱恶性肿瘤合并2型糖尿病患者的诊治。     

Effects of PAX3-FKHR on malignant phenotypes in alveolar rhabdomyosarcoma

The malignancy of alveolar rhabdomyosarcoma (ARMS) has been linked to expression of the PAX3-FKHR chimeric gene. To understand the effect of this gene, we used RNAi to knock down its expression (without affecting the expressions of either PAX3 or FKHR) in human ARMS cell lines. Down-regulating PAX3-FKHR caused (a) tumor cells to accumulate in the G1 phase, inhibiting the rate of cellular proliferation, (b) a reduction in the levels of the MET, reducing cell motility stimulated by HGF, and (c) induction of the myogenic differentiation gene, myogenin, and muscle differentiation (morphologic change and the expression of muscle specific proteins, desmin, and myosin heavy chain). These results suggest that PAX3-FKHR in ARMS cells promotes malignant phenotypes such as proliferation, motility, and to suppress differentiation.     

Loss of the tumor suppressor Snf5 leads to aberrant activation of the Hedgehog-Gli pathway

Aberrant activation of the Hedgehog (Hh) pathway can drive tumorigenesis. To investigate the mechanism by which glioma-associated oncogene family zinc finger-1 (GLI1), a crucial effector of Hh signaling, regulates Hh pathway activation, we searched for GLI1-interacting proteins. We report that the chromatin remodeling protein SNF5 (encoded by SMARCB1, hereafter called SNF5), which is inactivated in human malignant rhabdoid tumors (MRTs), interacts with GLI1. We show that Snf5 localizes to Gli1-regulated promoters and that loss of Snf5 leads to activation of the Hh-Gli pathway. Conversely, re-expression of SNF5 in MRT cells represses GLI1. Consistent with this, we show the presence of a Hh-Gli-activated gene expression profile in primary MRTs and show that GLI1 drives the growth of SNF5-deficient MRT cells in vitro and in vivo. Therefore, our studies reveal that SNF5 is a key mediator of Hh signaling and that aberrant activation of GLI1 is a previously undescribed targetable mechanism contributing to the growth of MRT cells.     

Isolation of genes from the rhabdoid tumor deletion region in chromosome band 22q11.2

We employed exon trapping and large-scale genomic sequence analysis of two bacterial artificial chromosome clones to isolate genes from the region between the IGLC and BCR in chromosome 22q11.2. At the time these studies were initiated, one previously identified gene, GNAZ, was known to map to this region. Two genes, RTDR1 and RAB36, were cloned from this portion of 22q11, which is heterozygously or homozygously deleted in pediatric rhabdoid tumors of the brain, kidney and soft tissues. RTDR1 is a novel gene with a slight homology to a yeast vacuolar protein. RAB36 is a member of the Rab family of proteins. A series of primary rhabdoid tumors with chromosome 22q11 deletions were screened for mutations in the coding sequences of RTDR1, GNAZ and RAB36, but did not demonstrate any disease-specific alterations. Recently, INI1, which maps to the distal portion of the deletion region in 22q11, was identified as the candidate rhabdoid tumor suppressor gene. Further studies of RTDR1 and RAB36 are required to determine whether their absence contributes to the progression of rhabdoid tumors. Alternatively, these genes may be candidates for other diseases that map to human chromosome 22.