Diffuse myogenin expression by immunohistochemistry is an independent marker of poor survival in pediatric rhabdomyosarcoma: a tissue microarray study of 71 primary tumors including correlation with molecular phenotype

Comparing the efficacy of concomitant treatment of resistance exercise and creatine monohydrate versus multiple individual therapies in age related sarcopenia

Aging-related sarcopenia is a degenerative loss of strength and skeletal muscle mass that impairs quality of life. Evaluating NUDT3 gene and myogenin expression as new diagnostic tools in sarcopenia. Also, comparing the concomitant treatment of resistance exercise (EX) and creatine monohydrate (CrM) versus single therapy by EX, coenzyme Q10 (CoQ10), and CrM using aged rats. Sixty male rats were equally divided into groups. The control group, aging group, EX-treated group, the CoQ10 group were administered (500 mg/kg) of CoQ10, the CrM group supplied (0.3 mg/kg of CrM), and a group of CrM concomitant with resistance exercise. Serum lipid profiles, certain antioxidant markers, electromyography (EMG), nudix hydrolase 3 (NUDT3) expression, creatine kinase (CK), and sarcopenic index markers were measured after 12 weeks. The gastrocnemius muscle was stained with hematoxylin-eosin (H&E) and myogenin. The EX-CrM combination showed significant improvement in serum lipid profile, antioxidant markers, EMG, NUDT3 gene, myogenin expression, CK, and sarcopenic index markers from other groups. The NUDT3 gene and myogenin expression have proven efficient as diagnostic tools for sarcopenia. Concomitant treatment of CrM and EX is preferable to individual therapy because it reduces inflammation, improves the lipid serum profile, promotes muscle regeneration, and thus has the potential to improve sarcopenia.

Cancer Stem Cell Markers in Rhabdomyosarcoma in Children

(1) Background: The aim of the present study was to assess the cancer stem cell (CSC) markers CD24, CD44, CD133, and ALDH1A1 in rhabdomyosarcoma (RMS) in children and to define their prognostic role in this group of patients. (2) Methods: The study material was archival tissue specimens collected from 49 patients under 18 years of age and who had been diagnosed with RMS. Immunohistochemistry (IHC) was used to evaluate the expression of the selected CSC markers in the tumor tissue. Expression was evaluated using a semiquantitative IRS scale based on the one developed by Remmele and Stenger and was correlated with the clinical and pathomorphological parameters of prognostic importance in RMS. (3) Results: Expression of the selected CSC markers CD24, CD44, CD133, and ALDH1A1 was demonstrated in 83.7%, 55.1%, 81.6%, and 100% of the RMS patients, respectively. The expression of all of the assessed CSC markers was statistically significantly higher in the study group versus the control group. No significant correlation was found between the expression of the selected CSC markers and clinical and pathological prognostic factors that were analyzed. The expression of the CSC markers did not have a significant influence on RMS survival rates. (4) Conclusions: The results of the conducted study confirm the expression of selected CSC markers in rhabdomyosarcoma tissue in children. The study did not support the prognostic relevance of the expression of any of the assessed CSC markers. However, further studies are needed to fully understand the relevance of the selected CSC markers in RMS carcinogenesis.

Mesenchymal tumor organoid models recapitulate rhabdomyosarcoma subtypes

Rhabdomyosarcomas (RMS) are mesenchyme-derived tumors and the most common childhood soft tissue sarcomas. Treatment is intense, with a nevertheless poor prognosis for high-risk patients. Discovery of new therapies would benefit from additional preclinical models. Here, we describe the generation of a collection of 19 pediatric RMS tumor organoid (tumoroid) models (success rate of 41%) comprising all major subtypes. For aggressive tumors, tumoroid models can often be established within 4-8 weeks, indicating the feasibility of personalized drug screening. Molecular, genetic, and histological characterization show that the models closely resemble the original tumors, with genetic stability over extended culture periods of up to 6 months. Importantly, drug screening reflects established sensitivities and the models can be modified by CRISPR/Cas9 with TP53 knockout in an embryonal RMS model resulting in replicative stress drug sensitivity. Tumors of mesenchymal origin can therefore be used to generate organoid models, relevant for a variety of preclinical and clinical research questions.

When a stuffy nose won't go away: Rhabdomyosarcoma masquerading as adenoiditis

Embryonal Rhabdomyosarcoma is a malignant mesenchymal proliferation of immature skeletal muscle and may arise in children in the orbit, middle ear, nasal cavity, paranasal sinuses, or nasopharynx. Clinical diagnosis may be difficult in a subset of patients who have no significant deformities or irregularities upon visual inspection of the oropharynx. Rhabdomyosarcoma in this setting may be mistaken for a more common underlying etiology such as an upper respiratory infection. We report a case of a 7-year-old male with embryonal variant rhabdomyosarcoma previously misdiagnosed by 3 different physicians to be adenoiditis based on clinical exam and laryngoscopy. This case highlights the capacity for rhabdomyosarcoma to mimic commonly encountered adenoiditis. It also serves as a reminder to maintain a high level of diagnostic vigilance and clinical suspicion of noninfectious etiologies when symptoms persist and are refractory to standard treatment.

Non-target genetic manipulation induces rhabdomyosarcoma in KrasPten-driven mouse model of ovarian cancer

Background

Genetically engineered mice are ideal models to advance our understanding the tumorigenesis of ovarian cancer. Our original objective was to establish an ovarian cancer model induced by Kras activation and Pten deletion. However, proficiently establishing the model remains a technical problem, which limits its application.

Methods

We established the Kras activation/Pten deletion-induced mouse model of ovarian cancer by injecting Cre recombinase-expressing adenovirus in the ovarian bursa. PCR analysis, Western blotting, and immunohistochemistry staining were performed to verify the alteration of conditional genes. We detected expression of canonical molecular markers in order to examine the origin of the tumors.

Results

Subcutaneous lumps developed accidentally in mice with ovarian cancer, as early as 2 weeks post in vivo genetic manipulation, far before the destructive growth of ovarian cancer. PCR analysis confirmed the efficient Cre-mediated recombination of Kras and Pten in tumor tissues, which are consistent with the activation of the MAPK and PI3K/Akt/mTOR pathways. Histomorphological and histological analysis showed that the lumps were actually rhabdomyosarcoma (RMS). We confirmed that the leakage of adenovirus transformed healthy adjacent tissues into RMS.

Conclusions

Avoiding accidental exposure of non-target tissues to adenovirus is crucial to successfully establish the ovarian cancer mouse model. Moreover, non-specific genetic manipulations can induce the development of RMS.

The PAX-FOXO1s trigger fast trans-differentiation of chick embryonic neural cells into alveolar rhabdomyosarcoma with tissue invasive properties limited by S phase entry inhibition

The chromosome translocations generating PAX3-FOXO1 and PAX7-FOXO1 chimeric proteins are the primary hallmarks of the paediatric fusion-positive alveolar subtype of Rhabdomyosarcoma (FP-RMS). Despite the ability of these transcription factors to remodel chromatin landscapes and promote the expression of tumour driver genes, they only inefficiently promote malignant transformation in vivo. The reason for this is unclear. To address this, we developed an in ovo model to follow the response of spinal cord progenitors to PAX-FOXO1s. Our data demonstrate that PAX-FOXO1s, but not wild-type PAX3 or PAX7, trigger the trans-differentiation of neural cells into FP-RMS-like cells with myogenic characteristics. In parallel, PAX-FOXO1s remodel the neural pseudo-stratified epithelium into a cohesive mesenchyme capable of tissue invasion. Surprisingly, expression of PAX-FOXO1s, similar to wild-type PAX3/7, reduce the levels of CDK-CYCLIN activity and increase the fraction of cells in G1. Introduction of CYCLIN D1 or MYCN overcomes this PAX-FOXO1-mediated cell cycle inhibition and promotes tumour growth. Together, our findings reveal a mechanism that can explain the apparent limited oncogenicity of PAX-FOXO1 fusion transcription factors. They are also consistent with certain clinical reports indicative of a neural origin of FP-RMS.

The fusion-positive subtype of rhabdomyosarcoma (FP-RMS) is a rare malignant paediatric cancer, whose induction and evolution still remain to be deciphered. Out of the gross genetic aberrations found in these cancers, t(2:13) and t(1,13) chromosome translocations are the first to appear and lead to the expression of fusion proteins made of the DNA binding domains of either PAX3 or PAX7 and the transactivation domain of FOXO1. Both PAX3-FOXO1 and PAX7-FOXO1 have a strong impact on gene transcription, yet they only inefficiently promote the transformation of healthy cells into tumorigenic cells. To address this issue, we have used chick embryos to monitor in vivo the early response of cells to PAX-FOXO1 chimeric proteins. We showed that both proteins, but not the normal PAX3 and PAX7, transform neural cells into cells with FP-RMS molecular features. The PAX-FOXO1s also force polarized epithelial neural cells to adopt a mesenchymal phenotype with tissue invasive properties. However, the PAX-FOXO1s inhibit cell division and hence tumour growth. Genetically re-activating core cell cycle regulators rescues PAX-FOXO1 mediated cell cycle inhibition. Together, our findings bring further support to the idea that the PAX-FOXO1s are stricto sensu oncoproteins, whose oncogenicity is limited by negative effects on cell cycle.

c-Myb regulates tumorigenic potential of embryonal rhabdomyosarcoma cells

Rhabdomyosarcomas (RMS) are a heterogeneous group of mesodermal tumors, the most common sub-types are embryonal (eRMS) and alveolar (aRMS) rhabdomyosarcoma. Immunohistochemical analysis revealed c-Myb expression in both eRMS and aRMS. c-Myb has been reported to be often associated with malignant human cancers. We therefore investigated the c-Myb role in RMS using cellular models of RMS. Specific suppression of c-Myb by a lentiviral vector expressing doxycycline (Dox)-inducible c-Myb shRNA inhibited proliferation, colony formation, and migration of the eRMS cell line (RD), but not of the aRMS cell line (RH30). Upon c-Myb knockdown in eRMS cells, cells accumulated in G0/G1 phase, the invasive behaviour of cells was repressed, and elevated levels of myosin heavy chain, marker of muscle differentiation, was detected. Next, we used an RD-based xenograft model to investigate the role of c-Myb in eRMS tumorigenesis in vivo. We found that Dox administration did not result in efficient suppression of c-Myb in growing tumors. However, when c-Myb-deficient RD cells were implanted into SCID mice, we observed inefficient tumor grafting and attenuation of tumor growth during the initial stages of tumor expansion. The presented study suggests that c-Myb could be a therapeutic target in embryonal rhabdomyosarcoma assuming that its expression is ablated.

Clinicopathologic features of 300 rhabdomyosarcomas with emphasis upon differential expression of skeletal muscle specific markers in the various subtypes: A single institutional experience

The present study was aimed at evaluating clinicopathologic and immunohistochemical (IHC) features of 300 rhabdomyosarcomas (RMSs), including differential IHC expression and prognostic value of myogenin and MyoD1 across various subtypes of RMSs. IHC expression of myogenin and MyoD1 was graded on the basis of percentage of tumor cells displaying positive intranuclear immunostaining i.e. grade 1 (1-25%); grade 2 (26-50%); grade 3 (51-76%) and grade 4 (76-100%).Clinical follow-up was available in 238 (79.3%) patients. Various clinicopathologic parameters were correlated with 3-year disease free survival (DFS) and overall survival (OS). There were 140 cases (46.7%) of alveolar RMS (ARMS), 90 of embryonal RMS (ERMS) (30%), 61 (20.3%) of spindle cell/sclerosing RMS and 9 cases (3%) of pleomorphic RMS. Most cases, barring pleomorphic RMSs, occurred in the first two decades (228 cases) (76%), frequently in males, in the head and neck region (126) (42%). By immunohistochemistry, desmin was positive in 292/299 (97.6%) tumors; myogenin in 238/267 (89.1%) and MyoD1 in 192/266 (72.2%) tumors. High myogenin expression (in ≥51% positive tumor cells) was significantly associated with ARMSs (95/121, 78.5%), as compared to other subtypes (48/117, 41%) (p value < 0.001). High MyoD1 expression (≥51% tumor cells) was seen in more cases of pure sclerosing, combined with spindle cell/sclerosing RMSs (10/10, 100%), as compared to the other subtypes (91/141, 67.4%) (p = 0.032). There was no significant difference between high myogenin expression and clinical outcomes. Patients without metastasis and harbouring tumors, measuring ≤5 cm showed a significant increase in OS, with p values = 0.01 and <0.001, respectively. ARMS was the most frequent subtype. There was a significant association between high myogenin expression and ARMSs and high MyoD1 expression and spindle cell/sclerosing RMSs. High myogenin expression did not correlate with clinical outcomes. Patients with smaller sized tumors and without metastasis had significantly better clinical outcomes.

PAX7 Expression in Rhabdomyosarcoma, Related Soft Tissue Tumors, and Small Round Blue Cell Neoplasms

Rhabdomyosarcoma, the most common soft tissue malignancy of childhood, is a morphologically variable tumor defined by its phenotype of skeletal muscle differentiation. The diagnosis of rhabdomyosarcoma often relies in part on the identification of myogenic gene expression using immunohistochemical or molecular techniques. However, these techniques show imperfect sensitivity and specificity, particularly in scant tissue biopsies. Here, we expand the toolkit for rhabdomyosarcoma diagnosis by studying the expression of PAX7, a transcriptional regulator of mammalian muscle progenitor cells implicated in the pathogenesis of rhabdomyosarcoma. Immunohistochemical analysis of tissue microarrays using a monoclonal anti-PAX7 antibody was used to characterize PAX7 expression in 25 non-neoplastic tissues, 109 rhabdomyosarcomas, and 697 small round blue cell or other soft tissue tumors. Among non-neoplastic tissues, PAX7 was specifically expressed in adult muscle progenitor cells (satellite cells). In embryonal rhabdomyosarcoma, PAX7 expression was positive in 52 of 63 cases (83%), negative in 9 of 63 cases (14%), and focal in 2 of 63 cases (3%). PAX7-positive embryonal rhabdomyosarcoma cases included several showing focal or negative myogenin expression. PAX7 expression in alveolar rhabdomyosarcoma was positive in 6 of 31 cases (19%), negative in 14 of 31 cases (45%), and focal in 11 of 31 cases (36%). In addition, PAX7 was expressed in 5 of 7 pleomorphic rhabdomyosarcomas (71%) and 6 of 8 spindle cell rhabdomyosarcomas (75%). Among histologic mimics, only Ewing sarcoma showed PAX7 expression (7/7 cases, 100%). In contrast, expression of PAX7 was not seen in the large majority (688/690, 99.7%) of examined cases of other soft tissue tumors, small round blue cell neoplasms, and leukemias/lymphomas. In summary, immunohistochemical analysis of PAX7 expression may be a useful diagnostic tool in the assessment of skeletal muscle differentiation in human tumors.

Immunohistochemical Profile of MYC Protein in Pediatric Small Round Blue Cell Tumors

Deregulation of MYC oncoprotein in cancers can result from multiple oncogenic mechanisms. Although MYC translocations define Burkitt lymphoma and MYC protein expression is a poor prognostic factor in undifferentiated neuroblastomas, the distribution of MYC protein (c-MYC) across other pediatric small round blue cell tumors (SRBCT) has not been well characterized. We undertook this study to assess MYC protein expression in a large cohort of pediatric lymphomas, sarcomas, and other SRBCT. Tissue microarrays containing 302 SRBCT were successfully evaluated by immunohistochemistry using anti-MYC clone Y69, with nuclear positivity scored as 0%, 1%-25%, 26%-50%, 51%-75%, or 76%-100%. MYC protein staining of >50% of lesional cells was identified in 60% of Burkitt lymphomas, 50% of B lymphoblastic lymphomas, 33% of T lymphoblastic lymphomas, 31% of rhabdomyosarcomas, 33% of Ewing sarcomas, and 25% of soft tissue sarcomas, not otherwise specified. Only 14% of neuroblastomas showed >50% staining, and of these, if known, MYCN was not amplified. No cases of Wilms tumor, synovial sarcoma, or desmoplastic small round cell tumor had >50% staining. Recurrences and metastases often had the same percentage of MYC staining (15/30). In conclusion, MYC protein exhibited variable expression across and within pediatric SRBCT subtypes. Overall, these findings provide a baseline for MYC expression in pediatric SRBCT and suggest that there may be multiple mechanisms of MYC upregulation in these different neoplasms.

Discovering novel oncogenic pathways and new therapies using zebrafish models of sarcoma

Sarcoma is a type of cancer affecting connective, supportive, or soft tissue of mesenchymal origin. Despite rare incidence in adults (<1%), over 15% of pediatric cancers are sarcoma. Sadly, both adults and children with relapsed or metastatic disease have devastatingly high rates of mortality. Current treatment options for sarcoma include surgery, radiation, and/or chemotherapy; however, significant limitations exist with respect to the efficacy of these strategies. Strong impetus has been placed on the development of novel therapies and preclinical models for uncovering mechanisms involved in the development, progression, and therapy resistance of sarcoma. Over the past 15 years, the zebrafish has emerged as a powerful genetic model of human cancer. High genetic conservation when combined with a unique susceptibility to develop sarcoma has made the zebrafish an effective tool for studying these diseases. Transgenic and gene-activation strategies have been employed to develop zebrafish models of rhabdomyosarcoma, malignant peripheral nerve sheath tumors, Ewing's sarcoma, chordoma, hemangiosarcoma, and liposarcoma. These models all display remarkable molecular and histopathological conservation with their human cancer counterparts and have offered excellent platforms for understanding disease progression in vivo. Short tumor latency and the amenability of zebrafish for ex vivo manipulation, live imaging studies, and tumor cell transplantation have allowed for efficient study of sarcoma initiation, growth, self-renewal, and maintenance. When coupled with facile chemical genetic approaches, zebrafish models of sarcoma have provided a strong translational tool to uncover novel drug pathways and new therapeutic strategies.

Molecular Markers in Bone and Soft-Tissue Tumors

Many sarcomas such as osteosarcoma have complex molecular compositions and behaviors that make standardized treatment difficult for patients with these tumors. Chromosomal translocations are noted in specific bone and soft-tissue sarcomas, and there are molecular tests (polymerase chain reaction [PCR] and fluorescence in situ hybridization [FISH]) used for accurate diagnosis. The translocations noted in sarcomas may allow future therapeutic targeting.

Genetics of Bladder Malignant Tumors in Childhood

Bladder masses are represented by either benign or malignant entities. Malignant bladder tumors are frequent causes of disease and death in western countries. However, in children they are less common. Additionally, different features are found in childhood, in which non epithelial tumors are more common than epithelial ones. Rhabdomyosarcoma is the most common pediatric bladder tumor, but many other types of lesions may be found, such as malignant rhabdoid tumor (MRT), inflammatory myofibroblastic tumor and neuroblastoma. Other rarer tumors described in literature include urothelial carcinoma and other epithelial neoplasms. Rhabdomyosarcoma is associated to a variety of genetic syndromes and many genes are involved in tumor development. PAX3-FKHR and PAX7-FKHR (P-F) fusion state has important implications in the pathogenesis and biology of RMS, and different genes alterations are involved in the pathogenesis of P-F negative and embryonal RMS, which are the subsets of tumors most frequently affecting the bladder. These genes include p53, MEF2, MYOG, Ptch1, Gli1, Gli3, Myf5, MyoD1, NF1, NRAS, KRAS, HRAS, FGFR4, PIK3CA, CTNNB1, FBXW7, IGF1R, PDGFRA, ERBB2/4, MET, BCOR. Malignant rhabdoid tumor (MRT) usually shows SMARCB1/INI1 alterations. Anaplastic lymphoma kinase (ALK) gene translocations are the most frequently associated alterations in inflammatory myofibroblastic tumor (IMT). Few genes alterations in urothelial neoplasms have been reported in the paediatric population, which are mainly related to deletion of p16/lnk4, overexpression of CK20 and overexpression of p53. Here, we reviewed available literature to identify genes associated to bladder malignancies in children and discussed their possible relationships with these tumors.

The Expression of c-Myb Correlates with the Levels of Rhabdomyosarcoma-specific Marker Myogenin

The transcription factor c-Myb is required for modulation of progenitor cells in several tissues, including skeletal muscle and its upregulation is observed in many human malignancies. Rhabdomyosarcomas (RMS) are a heterogeneous group of mesodermal tumors with features of developing skeletal muscle. Several miRNAs are downregulated in RMS, including miR-150, a negative regulator of c-Myb expression. Using the C2C12 myoblast cell line, a cellular model of skeletal muscle differentiation, we showed that miR-150 controls c-Myb expression mainly at the level of translation. We hypothesized that a similar mechanism of c-Myb regulation operates in RMS tumors. We examined expression of c-Myb by immunohistochemistry and revealed c-Myb positivity in alveolar and embryonal tumors, the two most common subgroups of RMS. Furthermore, we showed direct correlation between c-Myb production and myogenin expression. Interestingly, high myogenin levels indicate poor prognosis in RMS patients. c-Myb could, therefore, contribute to the tumor phenotype by executing its inhibitory role in skeletal muscle differentiation. We also showed that c-Myb protein is abundant in migratory C2C12 myoblasts and its ectopic expression potentiates cell motility. In summary, our results implicate that metastatic properties of some RMS subtypes might be linked to c-Myb function.

Probing for a deeper understanding of rhabdomyosarcoma: insights from complementary model systems

Rhabdomyosarcoma (RMS) is a mesenchymal malignancy composed of neoplastic primitive precursor cells that exhibit histological features of myogenic differentiation. Despite intensive conventional multimodal therapy, patients with high-risk RMS typically suffer from aggressive disease. The lack of directed therapies against RMS emphasizes the need to further uncover the molecular underpinnings of the disease. In this Review, we discuss the notable advances in the model systems now available to probe for new RMS-targetable pathogenetic mechanisms, and the possibilities for enhanced RMS therapeutics and improved clinical outcomes.

The Role of Immunohistochemistry in Rhabdomyosarcoma Diagnosis Using Tissue Microarray Technology and a Xenograft Model

Rhabdomyosarcomas (RMS) may resemble other non-myogenic sarcomas and malignant rhabdoid tumor (MRT). Alveolar rhabdomyosarcoma (ARMS) often harbors a typical translocation, but embryonal rhabdomyosarcoma (ERMS) lacks any specific rearrangement. Histopathology is not always sufficient for an unequivocal diagnosis, necessitating ancillary studies, including immunohistochemistry (IHC). Sixteen genetically tested RMS and two MRT were xenografted and followed in successive passages. Tissue microarrays were constructed including samples from original and xenograft tumors. Desmin, myogenin, CK, EMA, INI1, LSD1, AP2β, fibrillin-2, HMGA2, nestin, and SIRT1 were tested using immunohistochemical staining. Desmin and myogenin were positive in all RMS, and the epithelial markers were negative in almost all RMS. New markers (LSD1, AP2β, HMGA2, Nestin, and SIRT1) were positive in all RMS and MRT. There were no differences in IHC expression between the three RMS subtypes tested except fibrillin-2, which was negative in ARMS. Applying new IHC markers can contribute to RMS diagnosis. Nevertheless, most markers are also expressed in MRT, and further studies are needed to confirm their value against this and other small round cell tumors.

The Application of Immunohistochemical Biomarkers in Urologic Surgical Pathology

Context

Tumors of the genitourinary tract can be diagnostically challenging, particularly in core biopsies and cystoscopic biopsies with limited material. Immunohistochemistry is a valuable tool to use when morphology alone is insufficient for diagnosis.

Objectives

To review tumors and benign lesions of the kidney, urinary bladder, prostate gland, testis, and paratesticular structures with an emphasis on difficult differential diagnoses, as well as staining patterns in normal tissue. Recommended immunohistochemical stain panels are discussed that can assist in the diagnostic workup.

Data Sources

Review of current literature.

Conclusions

Immunohistochemistry is a valuable tool, assisting in the diagnosis of problematic tumors and benign lesions of the genitourinary tract.

Myogenin, AP2β, NOS-1, and HMGA2 are surrogate markers of fusion status in rhabdomyosarcoma: a report from the soft tissue sarcoma committee of the children's oncology group

Pediatric rhabdomyosarcoma (RMS) is traditionally classified on the basis of the histologic appearance into alveolar (ARMS) and embryonal (ERMS) subtypes. The majority of ARMS contain a PAX3-FOXO1 or PAX7-FOXO1 gene fusion, but about 20% do not. Intergroup Rhabdomyosarcoma Study stage-matched and group-matched ARMS typically behaves more aggressively than ERMS, but recent studies have shown that it is, in fact, the fusion status that drives the outcome for RMS. Gene expression microarray data indicate that several genes discriminate between fusion-positive and fusion-negative RMS with high specificity. Using tissue microarrays containing a series of both ARMS and ERMS, we identified a panel of 4 immunohistochemical markers-myogenin, AP2β, NOS-1, and HMGA2-which can be used as surrogate markers of fusion status in RMS. These antibodies provide an alternative to molecular methods for identification of fusion-positive RMS, particularly in cases in which there is scant or poor-quality material. In addition, these antibodies may be useful in fusion-negative ARMS as an indicator that a variant gene fusion may be present.

Therapeutic cytodifferentiation in alveolar rhabdomyosarcoma without genetic change of the PAX3-FKHR chimeric fusion gene: a case study

Alveolar rhabdomyosarcoma (ARMS) is a subtype of rhabdomyosarcoma and usually occurs in childhood and adolescence. ARMS is characterized by its aggressive behavior and poor prognosis. To improve the unfavorable prognosis, new therapeutic developments and the establishment of methods for precise prognostic prediction are required. We describe a case of ARMS, solid variant, which occurred in a 10-year-old boy. After chemotherapy and radiotherapy, the tumor morphologically and immunohistochemically showed marked cytodifferentiation, whereas the exact same PAX3-FKHR chimeric fusion gene transcript was detected in samples before and after treatment. The result of this study seems to indicate that therapeutic cytodifferentiation does not always correlate with genetic change and favorable prognosis in ARMS.

Anaplastic rhabdomyosarcoma in TP53 germline mutation carriers

BACKGROUND

Rhabdomyosarcoma (RMS) represents a diverse category of myogenic malignancies with marked differences in molecular alterations and histology. This study examines the question if RMS predisposition due to germline TP53 mutations correlates with certain RMS histologies.

METHODS

The histology of RMS tumors diagnosed in 8 consecutive children with TP53 germline mutations was reviewed retrospectively. In addition, germline TP53 mutation analysis was performed in 7 children with anaplastic RMS (anRMS) and previously unknown TP53 status.

RESULTS

RMS tumors diagnosed in 11 TP53 germline mutation carriers all exhibited nonalveolar, anaplastic histology as evidenced by the presence of enlarged hyperchromatic nuclei with or without atypical mitotic figures. Anaplastic RMS was the first malignant diagnosis for all TP53 germline mutation carriers in this cohort, and median age at diagnosis was 40 months (mean, 40 months ± 15 months; range, 19-67 months). The overall frequency of TP53 germline mutations was 73% (11 of 15 children) in pediatric patients with anRMS. The frequency of TP53 germline mutations in children with anRMS was 100% (5 of 5 children) for those with a family cancer history consistent with Li-Fraumeni syndrome (LFS), and 80% (4 of 5 children) for those without an LFS cancer phenotype.

CONCLUSIONS

Individuals harboring germline TP53 mutations are predisposed to develop anRMS at a young age. If future studies in larger anRMS cohorts confirm the findings of this study, the current Chompret criteria for LFS should be extended to include children with anRMS irrespective of family history.

Zebrafish rhabdomyosarcoma reflects the developmental stage of oncogene expression during myogenesis

Rhabdomyosarcoma is a pediatric malignancy thought to arise from the uncontrolled proliferation of myogenic cells. Here, we have generated models of rhabdomyosarcoma in the zebrafish by inducing oncogenic KRAS(G12D) expression at different stages during muscle development. Several zebrafish promoters were used, including the cdh15 and rag2 promoters, which drive gene expression in early muscle progenitors, and the mylz2 promoter, which is expressed in differentiating myoblasts. The tumors that developed differed in their ability to recapitulate normal myogenesis. cdh15:KRAS(G12D) and rag2:KRAS(G12D) fish developed tumors that displayed an inability to complete muscle differentiation as determined by histological appearance and gene expression analyses. By contrast, mylz2:KRAS(G12D) tumors more closely resembled mature skeletal muscle and were most similar to well-differentiated human rhabdomyosarcoma in terms of gene expression. mylz2:KRAS(G12D) fish showed significantly improved survival compared with cdh15:KRAS(G12D) and rag2:KRAS(G12D) fish. Tumor-propagating activity was enriched in myf5-expressing cell populations within all of the tumor types. Our results demonstrate that oncogenic KRAS(G12D) expression at different stages during muscle development has profound effects on the ability of tumor cells to recapitulate normal myogenesis, altering the tumorigenic capability of these cells.

A novel algorithm for simplification of complex gene classifiers in cancer

The clinical application of complex molecular classifiers as diagnostic or prognostic tools has been limited by the time and cost needed to apply them to patients. Using an existing 50-gene expression signature known to separate two molecular subtypes of the pediatric cancer rhabdomyosarcoma, we show that an exhaustive iterative search algorithm can distill this complex classifier down to two or three features with equal discrimination. We validated the two-gene signatures using three separate and distinct datasets, including one that uses degraded RNA extracted from formalin-fixed, paraffin-embedded material. Finally, to show the generalizability of our algorithm, we applied it to a lung cancer dataset to find minimal gene signatures that can distinguish survival. Our approach can easily be generalized and coupled to existing technical platforms to facilitate the discovery of simplified signatures that are ready for routine clinical use.

Mesenchymal tumours of the bladder and prostate: an update

Mesenchymal tumours of the urinary bladder and prostate are infrequent neoplasms. The body of literature is growing with isolated case reports and short series, and the majority of cases are benign neoplasms. Other than stromal tumour of uncertain malignant potential and prostatic stromal sarcoma, both neoplasms derived from the specific prostatic stroma, the mesenchymal neoplasms in these locations are identical to their counterparts seen in other organs. However, the limited amount of tissue generated by biopsy and rarity of mesenchymal lesions in these sites create unique diagnostic difficulties, while correct classification of the neoplasm often bears significant impact on prognosis and therapeutic strategy. In this review we summarise the diagnostic features, focus on the differential diagnosis, and highlight the potential diagnostic pitfalls of mesenchymal tumours of the bladder and prostate.

Cell-based small-molecule compound screen identifies fenretinide as potential therapeutic for translocation-positive rhabdomyosarcoma

A subset of paediatric sarcomas are characterized by chromosomal translocations encoding specific oncogenic transcription factors. Such fusion proteins represent tumor specific therapeutic targets although so far it has not been possible to directly inhibit their activity by small-molecule compounds. In this study, we hypothesized that screening a small-molecule library might identify already existing drugs that are able to modulate the transcriptional activity of PAX3/FOXO1, the fusion protein specifically found in the pediatric tumor alveolar rhabdomyosarcoma (aRMS). Towards this end, we established a reporter cell line based on the well characterized PAX3/FOXO1 target gene AP2ß. A library enriched in mostly FDA approved drugs was screened using specific luciferase activity as read-out and normalized for cell viability. The most effective inhibitor identified from this screen was Fenretinide. Treatment with this compound resulted in down-regulation of PAX3/FOXO1 mRNA and protein levels as well as in reduced expression of several of its direct target genes, but not of wild-type FOXO1, in a dose- and time-dependent manner. Moreover, fenretinide induced reactive oxygen species and apoptosis as shown by caspase 9 and PARP cleavage and upregulated miR-9. Importantly, it demonstrated a significant anti-tumor effect in vivo. These results are similar to earlier reports for two other pediatric tumors, namely neuroblastoma and Ewing sarcoma, where fenretinide is under clinical development. Our results suggest that fenretinide might represent a novel treatment option also for translocation-positive rhabdomyosarcoma.

Alveolar rhabdomyosarcoma - The molecular drivers of PAX3/7-FOXO1-induced tumorigenesis

Rhabdomyosarcoma is a soft tissue sarcoma arising from cells of a mesenchymal or skeletal muscle lineage. Alveolar rhabdomyosarcoma (ARMS) is more aggressive than the more common embryonal (ERMS) subtype. ARMS is more prone to metastasis and carries a poorer prognosis. In contrast to ERMS, the majority of ARMS tumors carry one of several characteristic chromosomal translocations, such as t(2;13)(q35;q14), which results in the expression of a PAX3-FOXO1 fusion transcription factor. In this review we discuss the genes that cooperate with PAX3-FOXO1, as well as the target genes of the fusion transcription factor that contribute to various aspects of ARMS tumorigenesis. The characterization of these pathways will lead to a better understanding of ARMS tumorigenesis and will allow the design of novel targeted therapies that will lead to better treatment for this aggressive pediatric tumor.

Myogenic tumors in children and adolescents

Neoplasms of striated and smooth muscle in children are a diverse group of neoplasms that have some unique aspects in contrast to these tumors in adults. Rhabdomyosarcoma is the most common soft tissue sarcoma of infancy and childhood and is relatively common in adolescents. In contrast, smooth muscle tumors are relatively rare, and the various types of rhabdomyoma and smooth and skeletal muscle hamartomas are very uncommon. In recent years, the understanding of the pathologic and genetic aspects of rhabdomyosarcoma has been enhanced by adjunct techniques, such as immunohistochemistry and cytogenetic or molecular genetic analysis. The current classification of rhabdomyosarcoma emphasizes the histologic-prognostic correlations. This article reviews the clinicopathologic features of striated and smooth muscle tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents and the differential diagnosis.

In vivo imaging of tumor-propagating cells, regional tumor heterogeneity, and dynamic cell movements in embryonal rhabdomyosarcoma

Embryonal rhabdomyosarcoma (ERMS) is an aggressive pediatric sarcoma of muscle. Here, we show that ERMS-propagating potential is confined to myf5+ cells and can be visualized in live, fluorescent transgenic zebrafish. During early tumor growth, myf5+ ERMS cells reside adjacent normal muscle fibers. By late-stage ERMS, myf5+ cells are reorganized into distinct regions separated from differentiated tumor cells. Time-lapse imaging of late-stage ERMS revealed that myf5+ cells populate newly formed tumor only after seeding by highly migratory myogenin+ ERMS cells. Moreover, myogenin+ ERMS cells can enter the vasculature, whereas myf5+ ERMS-propagating cells do not. Our data suggest that non-tumor-propagating cells likely have important supportive roles in cancer progression and facilitate metastasis.

MicroRNAs in rhabdomyosarcoma: pathogenetic implications and translational potentiality

There is growing evidence that interconnections among molecular pathways governing tissue differentiation are nodal points for malignant transformation. In this scenario, microRNAs appear as crucial players. This class of non-coding small regulatory RNA molecules controls developmental programs by modulating gene expression through post-transcriptional silencing of target mRNAs. During myogenesis, muscle-specific and ubiquitously-expressed microRNAs tightly control muscle tissue differentiation. In recent years, microRNAs have emerged as prominent players in cancer as well. Rhabdomyosarcoma is a pediatric skeletal muscle-derived soft-tissue sarcoma that originates from myogenic precursors arrested at different stages of differentiation and that continue to proliferate indefinitely. MicroRNAs involved in muscle cell fate determination appear down-regulated in rhabdomyosarcoma primary tumors and cell lines compared to their normal counterparts. More importantly, they behave as tumor suppressors in this malignancy, as their re-expression is sufficient to restore the differentiation capability of tumor cells and to prevent tumor growth in vivo. In addition, up-regulation of pro-oncogenic microRNAs has also been recently detected in rhabdomyosarcoma.

In this review, we provide an overview of current knowledge on microRNAs de-regulation in rhabdomyosarcoma. Additionally, we examine the potential of microRNAs as prognostic and diagnostic markers in this soft-tissue sarcoma, and discuss possible therapeutic applications and challenges of a "microRNA therapy".

Immunohistochemical expression and cluster analysis of mesenchymal and neural stem cell-associated proteins in pediatric soft tissue sarcomas

Pediatric undifferentiated soft tissue sarcomas (USTSs) are a group of malignancies composed predominantly of primitive round cell sarcomas, the histogenesis of which is uncertain. Thus, diagnosis and therapy remain a challenge. The aims of the current study were to determine whether differential expression of stem cell-associated proteins could be used to aid in determining the histogenesis of pediatric USTSs and to determine whether pediatric USTSs expressed a unique panel of stem cell-associated proteins to aid diagnosis. Tumors included 28 Ewing sarcoma/primitive neuroectodermal tumors (ESs), 22 embryonal rhabdomyosarcomas (ERMSs), 8 alveolar rhabdomyosarcomas (ARMSs), 5 synovial sarcomas (SSs), 5 malignant peripheral nerve sheath tumors (MPNSTs), and 13 USTSs. Stem cell antibodies included 3 mesenchymal stem cell markers (CD44, CD105, and CD166) and 5 neural stem cell markers (CD15, CD29, CD56, CD133, and nestin). Sections were scored followed by statistical analysis, clustering analysis, and visualizations using Partek Genomic Suite Software. The Euclidean clustering divided the tumors into 2 major groups. ESs and USTSs formed the majority of the 1st group, whereas ERMSs, ARMSs, MPNSTs, and SSs formed the 2nd group. Reduced expression of CD56 was strongly associated with the ES/USTS cluster (P < 0.0001). ESs and USTSs were further separated by CD166 staining, wherein increased expression was associated with ES (P < 0.0001). The 2nd group included the majority of other sarcomas, with no consistent separation between subtypes. The current study demonstrates the usefulness of applying stem cell markers to pediatric sarcomas and indicates that USTSs and ESs are closely related and may share a common histogenesis.

Optimising the management of soft tissue tumours

The Royal College of Pathologists of Australasia is developing a series of protocols as an educational tool to assist pathologists in the reporting of relevant information for specific cancer specimens. The protocol for the management of soft tissue tumour resections has recently been released, and this document elaborates the relevant literature on which that protocol drew. Sarcoma is uncommon but is associated with significant morbidity and mortality, and its management is complex. Diagnostic errors are not uncommon and these can have disastrous effects on patient outcome. Sophisticated ancillary testing is often an important adjunct to diagnosis and prognostication. Referral to a specialist sarcoma unit is indicated for both adult and paediatric sarcoma.

Immunohistochemical Markers of Value in the Diagnosis of Mesenchymal Lesions of the Female Genital Tract

Pure mesenchymal tumors may occur anywhere in the female genital tract, but they are most common in the uterine corpus, leiomyoma being by far the most prevalent. These tumors, and other uncommon mesenchymal lesions within the uterine corpus and elsewhere in the female genital tract, may result in several diagnostic problems. Morphology remains paramount and, in most cases, an unequivocal diagnosis can be made based on examination of the hematoxylin and eosin stained sections, combined with an appreciation of the clinical and gross pathologic features. In difficult cases, immunohistochemistry can significantly contribute to the final diagnosis. In this article, the immunohistochemistry of neoplastic and nonneoplastic mesenchymal lesions of the female genital tract is discussed site by site, concentrating on markers that are of value in diagnosis and in differential diagnosis. The immunophenotype of mixed epithelial and mesenchymal neoplasms and pure epithelial neoplasms with a component of spindle cells is discussed, where appropriate, because these can enter into the differential diagnosis of a pure mesenchymal lesion.

Molecular and cellular biology of rhabdomyosarcoma

Rhabdomyosarcoma is a group of soft-tissue sarcomas that share features of skeletal myogenesis, but show extensive heterogeneity in histology, age and site of onset, and prognosis. This review matches recent molecular data with biological features of rhabdomyosarcoma. Alterations in molecular pathways, animal models, cell of origin and potential new therapeutic targets are discussed.

Pediatric urologic rhabdomyosarcoma

PURPOSE OF REVIEW

To review on the most significant and recent developments in basic research, diagnostic, and therapeutic aspects of genitourinary rhabdomyosarcomas (RMS) in children.

RECENT FINDINGS

Collaborative studies have dramatically improved therapy of genitourinary RMS with a remarkable improvement of survival. However, refractory or relapsed disease is still the most demanding challenge. Advances in our understanding of RMS molecular biology evolve new risk stratification and new therapeutic targets such as growth factors and their receptors. High-quality imaging is crucial and integrated fluorodeoxyglucose positron emission tomography/computed tomography significantly increased sensitivity. Alternative chemotherapeutical strategies were proven. Mutilating primary surgery should be avoided. Modern irradiation modalities with decrease of local radiation dose and, therefore, less long-term effects are new tools in the therapeutic arsenal of therapists.

SUMMARY

Therapy-associated morbidity after current RMS treatment can be significantly decreased by including modern strategies, especially in the field of irradiation. However, the follow-up is too short so far to make a distinct decision. The advances in understanding tumor biology may give rise to clinically relevant new therapeutic targets in the near future.

Pediatric genitourinary tumors

PURPOSE OF REVIEW

We will review the 2007/2008 literature on pediatric genitourinary tumors.

RECENT FINDINGS

Newly identified constitutional epigenetic defects in Wilms tumor genes extend the understanding of Wilms tumor risk in children lacking syndromic features, and add to the complexity of the pathogenesis of these tumor suppressor genes. Pediatric renal cell carcinoma has distinct molecular characteristics and clinical associations from the adult counterpart. The pathway from PAX3-FKHR translocation to the development of rhabdomyosarcoma tumors has been further elucidated.

SUMMARY

Therapeutic strategies continue to be driven by developments in molecular diagnostics in pediatric genitourinary tumors.

Genomic imbalances in rhabdomyosarcoma cell lines affect expression of genes frequently altered in primary tumors: an approach to identify candidate genes involved in tumor development

Rhabdomyosarcomas (RMS) are the most common pediatric soft tissue sarcomas. They resemble developing skeletal muscle and are histologically divided into two main subtypes; alveolar and embryonal RMS. Characteristic genomic aberrations, including the PAX3- and PAX7-FOXO1 fusion genes in alveolar cases, have led to increased understanding of their molecular biology. Here, we determined the effect of genomic copy number on gene expression levels through array comparative genomic hybridization (CGH) analysis of 13 RMS cell lines, confirmed by multiplex ligation-dependent probe amplification copy number analyses, combined with their corresponding expression profiles. Genes altered at the transcriptional level by genomic imbalances were identified and the effect on expression was proportional to the level of genomic imbalance. Extrapolating to a public expression profiling dataset for 132 primary RMS identified features common to the cell lines and primary samples and associations with subtypes and fusion gene status. Genes identified such as CDK4 and MYCN are known to be amplified, overexpressed, and involved in RMS tumorigenesis. Of the many genes identified, those with likely functional relevance included CENPF, DTL, MYC, EYA2, and FGFR1. Copy number and expression of FGFR1 was validated in additional primary material and found amplified in 6 out of 196 cases and overexpressed relative to skeletal muscle and myoblasts, with significantly higher expression levels in the embryonal compared with alveolar subtypes. This illustrates the ability to identify genes of potential significance in tumor development through combining genomic and transcriptomic profiles from representative cell lines with publicly available expression profiling data from primary tumors.