Extracellular matrix of small round cell tumors of childhood: an immunohistochemical study of 67 cases

Cancer-Associated Fibroblast-Like Tumor Cells Remodel the Ewing Sarcoma Tumor Microenvironment

PURPOSE

Despite limited genetic and histologic heterogeneity, Ewing sarcoma (EwS) tumor cells are transcriptionally heterogeneous and display varying degrees of mesenchymal lineage specification in vitro. In this study, we investigated if and how transcriptional heterogeneity of EwS cells contributes to heterogeneity of tumor phenotypes in vivo.

EXPERIMENTAL DESIGN

Single-cell proteogenomic-sequencing of EwS cell lines was performed and integrated with patient tumor transcriptomic data. Cell subpopulations were isolated by FACS for assessment of gene expression and phenotype. Digital spatial profiling and human whole transcriptome analysis interrogated transcriptomic heterogeneity in EwS xenografts. Tumor cell subpopulations and matrix protein deposition were evaluated in xenografts and patient tumors using multiplex immunofluorescence staining.

RESULTS

We identified CD73 as a biomarker of highly mesenchymal EwS cell subpopulations in tumor models and patient biopsies. CD73+ tumor cells displayed distinct transcriptional and phenotypic properties, including selective upregulation of genes that are repressed by EWS::FLI1, and increased migratory potential. CD73+ cells were distinguished in vitro and in vivo by increased expression of matrisomal genes and abundant deposition of extracellular matrix (ECM) proteins. In epithelial-derived malignancies, ECM is largely deposited by cancer-associated fibroblasts (CAF), and we thus labeled CD73+ EwS cells, CAF-like tumor cells. Marked heterogeneity of CD73+ EwS cell frequency and distribution was detected in tumors in situ, and CAF-like tumor cells and associated ECM were observed in peri-necrotic regions and invasive foci.

CONCLUSIONS

EwS tumor cells can adopt CAF-like properties, and these distinct cell subpopulations contribute to tumor heterogeneity by remodeling the tumor microenvironment. See related commentary by Kuo and Amatruda, p. 5002.

Carcinoma-associated fibroblast-like tumor cells remodel the Ewing sarcoma tumor microenvironment

Tumor heterogeneity is a major driver of cancer progression. In epithelial-derived malignancies, carcinoma-associated fibroblasts (CAFs) contribute to tumor heterogeneity by depositing extracellular matrix (ECM) proteins that dynamically remodel the tumor microenvironment (TME). Ewing sarcomas (EwS) are histologically monomorphous, mesenchyme-derived tumors that are devoid of CAFs. Here we identify a previously uncharacterized subpopulation of transcriptionally distinct EwS tumor cells that deposit pro-tumorigenic ECM. Single cell analyses revealed that these CAF-like cells differ from bulk EwS cells by their upregulation of a matrisome-rich gene signature that is normally repressed by EWS::FLI1, the oncogenic fusion transcription factor that underlies EwS pathogenesis. Further, our studies showed that ECM-depositing tumor cells express the cell surface marker CD73, allowing for their isolation ex vivo and detection in situ. Spatial profiling of tumor xenografts and patient biopsies demonstrated that CD73 ⁺ EwS cells and tumor cell-derived ECM are prevalent along tumor borders and invasive fronts. Importantly, despite loss of EWS::FLI1-mediated gene repression, CD73 ⁺ EwS cells retain expression of EWS::FLI1 and the fusion-activated gene signature, as well as tumorigenic and proliferative capacities. Thus, EwS tumor cells can be reprogrammed to adopt CAF-like properties and these transcriptionally and phenotypically distinct cell subpopulations contribute to tumor heterogeneity by remodeling the TME.

A bioengineering method for modeling alveolar Rhabdomyosarcoma and assessing chemotherapy responses

Rhabdomyosarcoma (RMS) is the most common pediatric soft-tissue malignant tumor. Treatment of RMS usually includes primary tumor resection along with systemic chemotherapy. Two-dimensional (2D) cell culture systems and animal models have been extensively used for investigating the potential efficacy of new RMS treatments. However, RMS cells behave differently in 2D culture than in vivo, which has recently inspired the adoption of three-dimensional (3D) culture environments. In the current paper, we will describe the detailed methodology we have developed for fabricating a 3D engineered model to study alveolar RMS (ARMS) in vitro. This model consists of a thermally cross-linked collagen disk laden with RMS cells that mimics the structural and bio-chemical aspects of the tumor extracellular matrix (ECM). This process is highly reproducible and produces a 3D engineered model that can be used to analyze the cytotoxicity and autophagy induction of drugs on ARMS cells. The most improtant bullet points are as following:•

We fabricated 3D model of ARMS.

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The current ARMS 3D model can be used for screening of chemotherapy drugs.

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We developed methods to detect apoptosis and autophagy in ARMS 3D model to detect the mechansims of chemotherapy agents.

Clarifying prognostic factors of small cell osteosarcoma: A pooled analysis of 20 cases and the literature

Introduction

Small cell osteosarcoma (SCOS) is a rare subtype of osteosarcoma, with limited studies mainly focusing on histological features. Our study aims to analyze our own patients and those reported in the literature to increase the recognition of this rare disease, to evaluate patient survival and to further determine potential prognostic factors.

Material and methods

Twenty patients with SCOS were treated in our hospital between 2010 and 2019. Their follow-up data were collected retrospectively. A total of 336 literature cases from 58 manuscripts were retrieved by means of a PubMed search with the key word “small cell osteosarcoma”. Data pertaining to treatment and follow-up were extracted. We performed a pooled analysis for the survival of patients and the risk factors for local recurrence (LR), as well as metastatic disease (MD), in a total of 160 patients using the Kaplan-Meier method and Cox regression method.

Results

We reported our experience in diagnosing and treating SCOS. In our cases, elevated alkaline phosphatase (P = 0.013) and lactate dehydrogenase (P = 0.001) significantly impaired overall survival. In the pooled analysis, SCOS was diagnosed at the median age of 17 years and affected both sexes almost equally. The median follow-up duration was 19.5 months. In the pooled analysis cases, the 5-year overall survival rate was 38.6%, and 36.4% of patients survived 10 years. However, an increasing trend was detected, indicating recent improvements in management. The surgical margin status (P = 0.024) and metastases (P = 0.008) significantly impaired overall survival, and the response to chemotherapy was related to disease-free survival (P = 0.012). LR and MD were significantly correlated (P = 0.002) and could be observed after 5 years of follow-up. LR was significantly dependent on response to chemotherapy (P = 0.020). The development of MD seemed to be affected by response to chemotherapy (P = 0.060). Correlations between imaging features and prognosis were not detected.

Conclusions

This study suggested that positive margins, poor response to chemotherapy and MD are negative prognostic factors for SCOS, implied the potential role of laboratory examinations in the survival prediction and supported the need for prolonged or more intensive surveillance in patients with MD or LR. More well-documented literatures are encouraged to allow further confirmations.

3D tissue-engineered model of Ewing's sarcoma

Despite longstanding reliance upon monolayer culture for studying cancer cells, and numerous advantages from both a practical and experimental standpoint, a growing body of evidence suggests that more complex three-dimensional (3D) models are necessary to properly mimic many of the critical hallmarks associated with the oncogenesis, maintenance and spread of Ewing's sarcoma (ES), the second most common pediatric bone tumor. And as clinicians increasingly turn to biologically-targeted therapies that exert their effects not only on the tumor cells themselves, but also on the surrounding extracellular matrix, it is especially important that preclinical models evolve in parallel to reliably measure antineoplastic effects and possible mechanisms of de novo and acquired drug resistance. Herein, we highlight a number of innovative methods used to fabricate biomimetic ES tumors, encompassing both the surrounding cellular milieu and the extracellular matrix (ECM), and suggest potential applications to advance our understanding of ES biology, preclinical drug testing, and personalized medicine.

Patched haploinsufficient mouse rhabdomyosarcoma overexpress secreted phosphoprotein 1 and matrix metalloproteinases

Rhabdomyosarcoma is the most common soft tissue sarcoma of childhood. Improving the management of rhabdomyosarcoma requires a better understanding of growth regulation. Patched haploinsufficient (Ptch+/-) mice spontaneously develop soft tissue sarcomas that resemble human rhabdomyosarcomas. Using microarray profiling and quantitative real-time reverse transcriptase polymerase chain reaction, we identified candidate genes differentially expressed in Ptch+/- mouse rhabdomyosarcoma relative to mature muscle. Overexpressed genes include Secreted Phosphoprotein 1 (Spp1, Osteopontin), and Matrix Metalloproteinases-2 and -14 (Mmp2 and Mmp14). Spp1 is an integrin-binding phosphoglycoprotein upregulated in carcinomas, and Mmps regulate tumour invasion. Immunochemical analyses of murine and human rhabdomyosarcoma specimens confirmed increased expression of Spp1, Mmp2, Mmp14, nuclear factor-kappa B (NF-kappaB) p65 and its phosphorylated active isoform. Neutralising Spp1 antibody decreased Mmp14 RNA in murine rhabdomyosarcoma cultures, indicating a positive regulatory role for extracellular Spp1. Plasma from rhabdomyosarcoma patients display elevated levels of SPP1. These results implicate Spp1, NF-kappaB, and Mmp activation as a putative signalling pathway involved in rhabdomyosarcoma growth.

Small cell osteogenic sarcoma of the ribs: cytological, immunohistochemical, and ultrastructural study with literature review

Small cell osteosarcoma (OS) is a rare variant of OS that is composed of small cells resembling those of Ewing's sarcoma (ES) with recognizable osteoid. This type of tumor often creates difficulty in making a diagnosis when tissue samples do not include osteoid. The frequent sites are long bones and until now there have been no reported cases arising in the ribs. A case is reported here of small cell OS occurring in the ribs of a 37-year-old female with its aspiration cytologic and electron microscopic characteristics. In the cytologic smear, the small round neoplastic cells were individually scattered or arranged in small nests. The nuclei were hyperchromatic and oval with no visible nucleoli. Ultrastructurally, the nuclei had a round or oval euchromatic chromatin pattern and occasional nucleoli. The scanty cytoplasm contained a small quantity of organelles including either tubular or dilated cisternae of RER, a few mitochondria, and free or polyribosomes. Other organelles were absent. Although the electron microscope sample of this case did not include bone mineral (hydroxy apatite), the electron microscopic features of the tumor cells were unique and useful for exclusion of other small round cell neoplasms.