Cytodifferentiation and clinical outcome after chemotherapy and radiation therapy for rhabdomyosarcoma (RMS)

Single Nuclear RNA Sequencing Highlights Intra-Tumoral Heterogeneity and Tumor Microenvironment Complexity in Testicular Embryonic Rhabdomyosarcoma

Background

Testicular embryonic rhabdomyosarcoma (ERMS) is a rare soft tissue tumor in children featured with high intra-tumoral heterogeneity. In this study, we aimed to comprehensively delineate the testicular ERMS intra-tumoral heterogeneity and tumor microenvironment.

Methods

Cell types and the corresponding marker genes were identified by single-nuclear RNA sequencing (snRNA-seq). Functional states of different clusters were evaluated by uniform manifold approximation and projection and differentially expressed genes. Kaplan–Meier curve analysis was constructed according to the gene expression profile to determine the correlation between candidate marker genes and the overall survival and disease-free survival of patients with osteosarcoma from TCGA.

Results

A total of 8868 tumor cells and 10,147 normal cells were obtained from testicular ERMS tissues. The heterogeneous malignant subtype was composed of six subgroups (C1–C6) with differential proliferative and migratory potentials. Cell trajectory analysis revealed the C1 subgroup might be the starting cells of the tumor and transform into two different types of malignant cells, C2 and C5/6, during the development of RMS. The differentially expressed genes were closely related to cell adhesion and extracellular matrix signaling pathways. Furthermore, the interaction analysis between cell subgroups (macrophages and tumor cells, endothelial cells and tumor cells) demonstrated that collagen-related gene COL6A1 plays a key role from the initiation of ERMS to the entire process of malignant transformation.

Conclusion

Our findings provide a new insight in the understanding of the initiation and progression of testicular ERMS and have potential value in the development of markers for the diagnosis and stratification of testicular ERMS.

Embryonal Rhabdomyosarcoma with Posttherapy Cytodifferentiation and Aggressive Clinical Course

Rhabdomyosarcoma is the most common soft tissue sarcoma in children and adolescents. Embryonal rhabdomyosarcoma (ERMS), its most common subtype, is a malignant soft tissue tumor with morphologic and immunophenotypic features of embryonic skeletal muscle. The histologic findings in ERMS typically include a range of differentiation in rhabdomyoblasts from primitive to terminally differentiated forms, and the latter become more prominent after chemotherapy-induced cytodifferentiation. Several reports have shown therapy-related cytodifferentiation to portend a good prognosis in ERMS. We discuss the case of a pediatric patient who presented with ERMS of the orbit. Although her tumor showed extensive posttreatment cytodifferentiation and several other good prognostic clinicopathologic factors, it pursued an aggressive course, resulting in early metastasis and death. This case represents an unusual course and may be instructive as to the clinicopathologic features impacting prognostication, and ultimately the biology, of this aggressive family of tumors.

FOXF1 is required for the oncogenic properties of PAX3-FOXO1 in rhabdomyosarcoma

The PAX3-FOXO1 fusion protein is the key oncogenic driver in fusion positive rhabdomyosarcoma (FP-RMS), an aggressive soft tissue malignancy with a particularly poor prognosis. Identifying key downstream targets of PAX3-FOXO1 will provide new therapeutic opportunities for treatment of FP-RMS. Herein, we demonstrate that Forkhead Box F1 (FOXF1) transcription factor is uniquely expressed in FP-RMS and is required for FP-RMS tumorigenesis. The PAX3-FOXO1 directly binds to FOXF1 enhancers and induces FOXF1 gene expression. CRISPR/Cas9 mediated inactivation of either FOXF1 coding sequence or FOXF1 enhancers suppresses FP-RMS tumorigenesis even in the presence of PAX3-FOXO1 oncogene. Knockdown or genetic knockout of FOXF1 induces myogenic differentiation in PAX3-FOXO1-positive FP-RMS. Over-expression of FOXF1 decreases myogenic differentiation in primary human myoblasts. In FP-RMS tumor cells, FOXF1 protein binds chromatin near enhancers associated with FP-RMS gene signature. FOXF1 cooperates with PAX3-FOXO1 and E-box transcription factors MYOD1 and MYOG to regulate FP-RMS-specific gene expression. Altogether, FOXF1 functions downstream of PAX3-FOXO1 to promote FP-RMS tumorigenesis.

Chemoradiotherapy-induced Cytodifferentiation in Bladder/Prostate Rhabdomyosarcoma With Genetic Downregulation of Myogenin and MyoD1 Gene Expression: A Case Study and Review of the Literature

Rhabdomyosarcoma is the most common sarcoma diagnosed in childhood and adolescence, arising from the bladder/prostate in only 5%-10% of cases. Treatment-induced cytodifferention of tumor cells into mature rhabdomyoblasts has been reported following chemoradiation and is thought to suggest a more favorable outcome. We report a case of embryonal rhabdomyosarcoma of the bladder/prostate that exhibited extensive cytodifferentiation with downregulation of myogenin and MyoD1 gene expression in rhabdomyoblasts following treatment with chemoradiation therapy. The downregulation of myogenin and MyoD1 expression in rhabdomyoblasts following chemoradiation treatment has not previously been described in the literature and its significant remains uncertain.

Maturation toward neuronal tissue in a Ewing sarcoma of bone after chemotherapy

Background

Ewing sarcoma is the second most common bone tumor, occurring mainly in children and young adults. It shows a typical primitive, small round cell morphology and a characteristic fusion oncogene involving EWSR1 and members of the ETS family in most of the cases. Neuronal maturation after chemotherapy is a rare phenomenon and we herein describe such an exceptional case.

Case presentation

An 8-year old boy was diagnosed with a Ewing sarcoma in the left femur. On biopsy the morphology was typical and there was an EWSR1-FLI1 gene fusion. He underwent neo-adjuvant chemotherapy and resection of the tumor. On microscopic evaluation, part of the tumor showed ganglioneuroblastoma-like differentiation with expression of neuronal markers. The continued presence of EWSR1 rearrangement in both the blue round cell component and the ganglioneuroblastoma-like component was shown by FISH analysis.

Conclusions

In conclusion, this case describes the possibility of a Ewing sarcoma to differentiate into a ganglioneuroblastoma-like lesion after neo-adjuvant chemotherapy treatment; the prognostic value of this phenomenon remains questionable.

Electronic supplementary material

The online version of this article (doi:10.1186/s13000-016-0516-0) contains supplementary material, which is available to authorized users.

Adipocyte-Like Differentiation in a Posttreatment Embryonal Rhabdomyosarcoma

We describe a 16-year-old boy with rhabdomyosarcoma, consistent with embryonal subtype, of the lower extremity who received systemic neoadjuvant chemotherapy and subsequent excision. Microscopic sections of the postchemotherapy excision demonstrated diffuse, prominent, and immature adipocyte-like differentiation, in addition to skeletal muscle differentiation. Adipocyte-like differentiation was confirmed by a combination of positive Oil Red O and adipophilin immunohistochemical staining. To our knowledge, this represents the first report of an unusual phenomenon of differentiation of a soft tissue rhabdomyosarcoma into adipocyte-like cells after chemotherapy.

Rhabdomyosarcoma: current challenges and their implications for developing therapies

Rhabdomyosarcoma (RMS) represents a rare, heterogeneous group of mesodermal malignancies with skeletal muscle differentiation. One major subgroup of RMS tumors (so-called "fusion-positive" tumors) carries exclusive chromosomal translocations that join the DNA-binding domain of the PAX3 or PAX7 gene to the transactivation domain of the FOXO1 (previously known as FKHR) gene. Fusion-negative RMS represents a heterogeneous spectrum of tumors with frequent RAS pathway activation. Overtly metastatic disease at diagnosis is more frequently found in individuals with fusion-positive than in those with fusion-negative tumors. RMS is the most common pediatric soft-tissue sarcoma, and approximately 60% of all children and adolescents diagnosed with RMS are cured by currently available multimodal therapies. However, a curative outcome is achieved in <30% of high-risk individuals with RMS, including all those diagnosed as adults, those diagnosed with fusion-positive tumors during childhood (including metastatic and nonmetastatic tumors), and those diagnosed with metastatic disease during childhood (including fusion-positive and fusion-negative tumors). This white paper outlines current challenges in RMS research and their implications for developing more effective therapies. Urgent clinical problems include local control, systemic disease, need for improved risk stratification, and characterization of differences in disease course in children and adults. Biological challenges include definition of the cellular functions of PAX-FOXO1 fusion proteins, clarification of disease heterogeneity, elucidation of the cellular origins of RMS, delineation of the tumor microenvironment, and identification of means for rational selection and testing of new combination therapies. To streamline future therapeutic developments, it will be critical to improve access to fresh tumor tissue for research purposes, consider alternative trial designs to optimize early clinical testing of candidate drugs, coalesce advocacy efforts to garner public and industry support, and facilitate collaborative efforts between academia and industry.

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.

RAGE signaling deficiency in rhabdomyosarcoma cells causes upregulation of PAX7 and uncontrolled proliferation

Embryonal rhabdomyosarcomas (ERMSs) show elevated levels of PAX7, a transcription factor that marks quiescent adult muscle stem (satellite) cells and is important for proliferation and survival of activated satellite cells and whose timely repression is required for myogenic differentiation. However, the mechanism of PAX7 accumulation in ERMSs and whether high PAX7 causes uncontrolled proliferation in ERMS remains to be elucidated. The receptor for advanced glycation end-products (RAGE, encoded by AGER) transduces a myogenic and anti-proliferative signal in myoblasts, and stable transfection of the ERMS cell line TE671, which does not express RAGE, with AGER results in reduced proliferation and formation of tumor masses in vivo, and enhanced apoptosis and myogenic differentiation. Herein, we show that RAGE expression is low or absent in human ERMSs. We also show that in ERMS cells (1) PAX7 accumulates owing to absent or low RAGE signaling; (2) elevated PAX7 levels reduce RAGE expression and levels of MyoD and myogenin, muscle-specific transcription factors required for myoblast proliferation arrest and differentiation, respectively; (3) PAX7 supports myoblast proliferation by reducing the levels of MyoD, primarily by promoting its degradation; and (4), when ectopically expressed in ERMS cells, that RAGE upregulates myogenin which upregulates MyoD and downregulates PAX7, with consequent inhibition of proliferation and stimulation of differentiation. Thus, failure to express RAGE and, hence, MyoD and myogenin above a critical level in ERMS cells might result in deregulated PAX7 expression leading to uncontrolled proliferation and, potentially, to rhabdomyosarcomagenesis.

Extensive adipocytic maturation can be seen in myxoid liposarcomas treated with neoadjuvant doxorubicin and ifosfamide and pre-operative radiation therapy

BACKGROUND

Trabectedin and thioglitazones have been documented to induce adipocytic maturation in myxoid liposarcoma; we have noted this in our experience as well. Intriguingly, we have also encountered this same phenomenon in myxoid liposarcomas exposed to various combinations of neoadjuvant doxorubicin and ifosfamide systemic chemotherapy with preoperative radiation, where the pathological effects have been less characterized. We examined the histological changes, including adipocytic maturation, associated with this treatment in patients with myxoid liposarcoma and evaluated for prognostic significance.

METHODS

Twenty-two patients were identified with histologically confirmed myxoid liposarcomas (9 with variable hypercellular areas) who were treated with neoadjuvant doxorubicin (75-90 mg/m2/continous infusion over 72h every 3 week) and ifosfamide (2.5 g/m2 daily x 4 every 3 weeks) for 4-6 cycles. Twenty-one patients received pre-operative radiation including 5 with concurrent gemcitabine. Pre- and post-treatment MRI studies were compared for changes in tumor area, fat content and contrast uptake, with the latter two estimated as: none, <25%, 25-49% and >50%. Post-treatment specimens were evaluated for hyalinization, necrosis and adipocytic maturation. Clinical follow-up was obtained.

RESULTS

Median age was 45 (26-72) years with a median tumor size of 11 (2-18) cm. All occurred in the lower extremities except for one case in the neck. As is common in myxoid liposarcoma, all had extensive treatment changes (>90%) with extensive hyalinization (n = 16; >90%) or prominent adipocytic maturation (n = 6; >50%) including 2 cases composed almost entirely of mature-appearing adipose tissue. Variable necrosis was identified (5-30%). MRI revealed a decrease in tumor area in all but one tumor (median, 65%), an increase in fat content in 7 tumors (n = 2, >50%;n = 2, 25-50%;n = 3,<25%), and a decrease in contrast enhancement in most tumors (n = 5, >50%; n = 9, 25-49%; n = 7, <25%). Median follow-up was 57 (12-96) months with 17 alive with no disease/metastases, 3 alive with disease and 2 dead of disease. Six patients developed metastases with median interval of 26 (22-51) months post resection. Four of 6 tumors with increased adipocytic maturation >50% on histology had increased fat detected by MRI (>25%). All 6 are alive but 2 developed metastases. In the remaining patients, 4 developed metastases with 14 alive and 2 dead of disease.

CONCLUSION

Myxoid liposarcoma exposed to neoadjuvant doxorubicin and ifosfamide and pre-operative radiation can have prominent adipocytic maturation similar to trabectedin treatment. Myxoid liposarcomas exhibit extensive treatment changes with prominent hyalinization being the most common histological change. Despite this, patients develop metastases regardless of adipocytic maturation. While of unclear significance, no patient with fatty maturation died of disease.

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.

Evidence for an unanticipated relationship between undifferentiated pleomorphic sarcoma and embryonal rhabdomyosarcoma

Embryonal rhabdomyosarcoma (eRMS) shows the most myodifferentiation among sarcomas, yet the precise cell of origin remains undefined. Using Ptch1, p53 and/or Rb1 conditional mouse models and controlling prenatal or postnatal myogenic cell of origin, we demonstrate that eRMS and undifferentiated pleomorphic sarcoma (UPS) lie in a continuum, with satellite cells predisposed to giving rise to UPS. Conversely, p53 loss in maturing myoblasts gives rise to eRMS, which have the highest myodifferentiation potential. Regardless of origin, Rb1 loss modifies tumor phenotype to mimic UPS. In human sarcomas that lack pathognomic chromosomal translocations, p53 loss of function is prevalent, whereas Shh or Rb1 alterations likely act primarily as modifiers. Thus, sarcoma phenotype is strongly influenced by cell of origin and mutational profile.

Effects of neoadjuvant chemotherapy on hepatoblastoma: a morphologic and immunohistochemical study

Neoadjuvant chemotherapy followed by resection has become the mainstay in the treatment of hepatoblastoma (HB). The changes after chemotherapy typically result in tumor necrosis and a fibrohistiocytic response. We have observed that treated HBs undergo additional morphologic changes that have not been described. Herein, we report a 15-year retrospective study of HBs in 22 children who received neoadjuvant chemotherapy according to the Children's Oncology Group protocols. The medical records, diagnostic imaging, and histopathology were reviewed. Besides treated HBs having characteristic necrosis and fibrohistiocytic response, two-thirds had areas of cytoarchitectural differentiation ("maturation") mimicking non-neoplastic liver, and a quarter had alterations mimicking hepatocellular carcinoma. Nuclear expression of beta-catenin and keratin profiles were useful in distinguishing residual tumor with "maturation" from non-neoplastic liver and therefore in the assessment of surgical margins. Statistical analysis revealed that larger pretreatment and posttreatment imaged tumor size, larger tumor size at pathologic examination, and vascular invasion were significant univariate predictors of metastatic disease, whereas pretreatment imaged tumor size and vascular invasion were also significant independent predictors (multivariate logistic regression analysis). Multifocality, greater posttreatment necrosis and hepatocellular carcinoma-like morphology were more often associated with metastatic disease, but did not reach statistical significance.

A human recombinant autoantibody-based immunotoxin specific for the fetal acetylcholine receptor inhibits rhabdomyosarcoma growth in vitro and in a murine transplantation model

Rhabdomyosarcoma (RMS) is the most common malignant soft tissue tumor in children and is highly resistant to all forms of treatment currently available once metastasis or relapse has commenced. As it has recently been determined that the acetylcholine receptor (AChR) gamma-subunit, which defines the fetal AChR (fAChR) isoform, is almost exclusively expressed in RMS post partum, we recombinantly fused a single chain variable fragment (scFv) derived from a fully human anti-fAChR Fab-fragment to Pseudomonas exotoxin A to generate an anti-fAChR immunotoxin (scFv35-ETA). While scFv35-ETA had no damaging effect on fAChR-negative control cell lines, it killed human embryonic and alveolar RMS cell lines in vitro and delayed RMS development in a murine transplantation model. These results indicate that scFv35-ETA may be a valuable new therapeutic tool as well as a relevant step towards the development of a fully human immunotoxin directed against RMS. Moreover, as approximately 20% of metastatic malignant melanomas (MMs) display rhabdoid features including the expression of fAChR, the immunotoxin we developed may also prove to be of significant use in the treatment of these more common and most often fatal neoplasms.

Differentiated rhabdomyomatous tumors after chemotherapy for metastatic testicular germ-cell tumors: a clinicopathological study of seven cases mandating separation from rhabdomyosarcoma

To gain insight concerning prognosis, we investigated seven cases of post-chemotherapy retroperitoneal lymph-node dissections from patients with testicular germ-cell tumors that contained sizable nodules of differentiated skeletal muscle, but that lacked both a primitive cellular component and mitotic activity. The patients were 18-28 years old at the time of retroperitoneal lymph-node dissection. All had a previous non-seminomatous germ-cell tumor of the testis, five of which had a teratoma component. In one the testicular tumor had foci of embryonal rhabdomyosarcoma. The retroperitoneal lymph-node dissections were performed 0.2-4.7 years after orchiectomy, all following cisplatin-based chemotherapy, and contained rhabdomyomatous tumors that ranged from 0.8-5 cm. These consisted of nodular to diffuse aggregates of fetal-type rhabdomyocytes with central to peripheral nuclei and abundant, eosinophilic, fibrillary cytoplasm with occasional cross striations. Elongated myotubes with multiple nuclei in a common sarcoplasm occurred at least focally in all cases. Mild to moderate nuclear atypia, including nuclear enlargement and nucleolar prominence, was present, but mitotic activity, necrosis, and a primitive cellular component were absent. All but one retroperitoneal lymph-node dissection also contained other teratomatous elements. Follow-up in six patients showed three were disease free at 2.2-3.4 years; two developed recurrent teratoma at 1.3-3.7 years; and a sixth developed recurrent teratoma at 0.5 and 2 years, followed at 17 years by progressive tumor with elevated alpha-fetoprotein. No patient with available follow-up developed progressive sarcoma. We conclude that rhabdomyomatous tumors in retroperitoneal lymph-node dissection specimens after chemotherapy for metastatic testicular germ-cell tumors show clinical behavior similar to teratoma rather than rhabdomyosarcoma. We believe the most likely explanation for the finding of pure rhabdomyomatous tumors in this setting, a phenomenon sometimes termed 'cytodifferentiation,' is selective persistence of differentiated tumor cells because of chemotherapy.

Rhabdomyosarcomas in adults and children: an update

CONTEXT

Rhabdomyosarcomas comprise a relatively common diagnostic entity among childhood cancers and a relatively rare one among adult tumors. They may possess a variety of histologies that generally differ among age groups. These lesions appear to be separate biologic entities as well as morphologic categories, with embryonal tumors having genetic lesions related to loss of heterozygosity and aberrant parental imprinting, alveolar tumors containing genetic fusions between PAX and forkhead genes, and pleomorphic tumors showing an accumulation of genetic lesions similar to other adult high-grade sarcomas.

OBJECTIVE

To present guidelines for diagnosis of rhabdomyosarcoma and recent finding concerning the biology and classification of these lesions.

DATA SOURCES

Review of recent and older published literature and distillation of the authors' experience.

CONCLUSIONS

Infants and young children tend to have embryonal rhabdomyosarcomas, adolescents and young adults tend to have alveolar rhabdomyosarcomas, and older adults tend to have pleomorphic rhabdomyosarcomas, although there is some overlap. Newer rare entities, including spindle cell rhabdomyosarcoma and sclerosing rhabdomyosarcoma, have been described in children and adults. Fusion-positive tumors have a distinct molecular signature with downstream activation of a number of myogenic and tumorigenic factors. Genetic testing may be successfully used for diagnosis and may guide therapy in future clinical trials. Differential diagnosis has become simpler than in previous years, because of use of myogenic factors in immunohistochemistry, but classification based solely on histologic features remains challenging.

Treatment effects in pediatric soft tissue and bone tumors: practical considerations for the pathologist

Dramatic improvements in survival for children with cancer have led to increased numbers of posttreatment pathologic specimens, particularly in bone and soft tissue sarcomas. Current therapeutic protocols in North America require specific pathologic classification and stratify patients based on clinical, biologic, and pathologic features. For osteosarcoma, the pathologic response to therapy predicts prognosis and modifies the treatment regimen. Ongoing studies aim to assess the response to therapy and outcome in other types of soft tissue and bone tumors. The pathologic evaluation of pretreatment and posttreatment specimens is critical for therapeutic decisions and prognostic assessment. A standardized approach to posttherapy pathologic specimens, with attention to appropriate use of ancillary tests, and assessment of clinical and biologic significance of therapy-induced pathologic changes has significance for patient management and treatment protocols.

Evidence of neural differentiation in a case of post-therapy primitive neuroectodermal tumor/Ewing sarcoma of bone

Neural differentiation with the appearance of ganglion-like cells has been reported in untreated primitive neuroectodermal tumor/Ewing sarcoma (PNET/EWS) at peculiar sites, such as the cauda equina, and following treatment. The case is presented here of a 17-year-old girl with a tumor in the iliac bone. An open biopsy was diagnosed as PNET/EWS of the bone. The tumor had the typical morphology of this tumor type and showed diffuse membranous immunoreactivity for CD99, intense immunoreactivity for synaptophysin, and focal immunoreactivity for neuron-specific enolase and S-100 protein. Occasional reactivity for vimentin was evident, while no immunoreactivity for NB84a, Hu, chromogranins A and B, neurofilaments, cytokeratins, and desmin was present. The patient underwent chemotherapy and radiotherapy, followed by right internal hemipelvectomy. The post-treatment residual viable tumor showed a morphologic appearance resembling a neuroblastoma, with immunoreactivity for NB84a, Hu, synaptophysin, and chromogranins A and B, but not for CD99. RT-PCR performed on tumor tissue before and after therapy showed the presence of the EWS-FLI1 fusion transcript, type I in both samples. This case of PNET/EWS is unique in the sense of showing the typical fusion transcript associated with this tumor both in the morphologically typical pretherapy tumor and in the sample from the post-therapy specimen showing neuroblastoma-like features.

Pediatric genitourinary tumors

Advances continue to be made in the evaluation and treatment of genitourinary tumors in children. Continued research on the cellular, molecular, and genetic process in tumorigenesis is rapidly evolving. We review the 2002 literature on pediatric genitourinary tumors. Molecular and cellular biology research continues to identify markers that may predict a worse prognosis. This identification will allow a more tailored approach with intensified treatment of aggressive tumors.