Bone sarcomas are rare cancers which often present with metastatic disease and are still associated with poor survival rates. Studies in the last decade have identified that exosomes, a type of extracellular vesicle released by cells, play an important role in tumour progression and dissemination. Through the transfer of their cargo (RNAs, proteins, and lipids) across cells, they are involved in cellular cross-talk and can induce changes in cellular behaviour. Exosomes have been shown to be important in metastasis organotropism, induction of angiogenesis and vascular permeability, the education of cells towards a pro-metastatic phenotype or the interaction between stromal and tumour cells. Due to the importance exosomes have in disease progression and the high incidence of metastasis in bone sarcomas, recent studies have evaluated the implications of these extracellular vesicles in bone sarcomas. In this review, we discuss the studies that evaluate the role of exosomes in osteosarcoma, Ewing sarcoma, and preliminary data on chondrosarcoma.
Purpose The development of biomarkers and molecularly targeted therapies for patients with Ewing sarcoma (ES) in order to minimise morbidity and improve outcome is urgently needed. Here, we set out to isolate and characterise patient-derived ES primary cell cultures and daughter cancer stem-like cells (CSCs) to identify biomarkers of high-risk disease and candidate therapeutic targets. Methods Thirty-two patient-derived primary cultures were established from treatment-naïve tumours and primary ES-CSCs isolated from these cultures using functional methods. By RNA-sequencing we analysed the transcriptome of ES patient-derived cells (n = 24) and ES-CSCs (n = 11) to identify the most abundant and differentially expressed genes (DEGs). Expression of the top DEG(s) in ES-CSCs compared to ES cells was validated at both RNA and protein levels. The functional and prognostic potential of the most significant gene (neurexin-1) was investigated using knock-down studies and immunohistochemistry of two independent tumour cohorts. Results ES-CSCs were isolated from all primary cell cultures, consistent with the premise that ES is a CSC driven cancer. Transcriptional profiling confirmed that these cells were of mesenchymal origin, revealed novel cell surface targets for therapy that regulate cell-extracellular matrix interactions and identified candidate drivers of progression and relapse. High expression of neurexin-1 and low levels of regulators of its activity, APBA1 and NLGN4X, were associated with poor event-free and overall survival rates. Knock-down of neurexin-1 decreased viable cell numbers and spheroid formation. Conclusions Genes that regulate extracellular interactions, including neurexin-1, are candidate therapeutic targets in ES. High levels of neurexin-1 at diagnosis are associated with poor outcome and identify patients with localised disease that will relapse. These patients could benefit from more intensive or novel treatment modalities. The prognostic significance of neurexin-1 should be validated independently.
Background: Rhabdomyosarcoma (RMS) is the most prevalent soft tissue sarcoma in children and adolescents. It is divided in two major histological subtypes, being the Alveolar (ARMS) the one associated to a poorer prognosis1. The cure rate for these tumors is up to 70% for children with localized disease, but this numbers decrease notably to a 20% 5-year survival rate for patients that show metastatic spreading. However, mechanisms leading to metastatic disease remain poorly understood. Hence, there is an urgent need to better understand this process, which will hopefully lead to novel targeted therapies and improved survival rates for these patients. Methods: ARMS cells (RH4) were injected in the gastrocnemius muscle of Athymic Nude-Foxn1nu mice2. Primary tumors (800mm3) and peritoneal metastases (visible by IVIS®) were collected, and RNA extracted. Xenograft-derived metastatic cell lines were obtained directly as a primary culture from mice metastases. Characterization of paired tumors and metastases was performed using Clariom™ D microarray (Applied Biosystems). After data normalization and comparative analyses (R; RMA and limma), a list of differentially expressed transcripts between sample groups was obtained. These are being validated by qPCR and Western Blot. Results: Transcriptomic profiling of tumors (n=3), paired metastases (n=3), xenograft-derived metastatic cell lines (n=3) and RH4 cell line (n=3) revealed 3420 differentially expressed transcripts (2747 increased in metastases, 673 in tumors). Several transcripts of interest are overexpressed in metastases samples compared to primary tumors as showed by microarray analysis and validated by qPCR. These targets are related in literature to metastasis in other cancers, as well as lymph nodes metastasis, which occurs to happen in our model and in ARMS clinics3. Additionally, some transcripts are overexpressed in tumor samples, which are linked to inhibition of proliferation and motility. Conclusions/Future Work: In vitro phenotypic characterization of the obtained targets will involve proliferation (MTT), migration (Transwell®) and clonogenic assays, including loss-of-function (siRNA and commercial inhibitors). Using stable knock-out and knock-in models of the genes of interest, their role in ARMS metastasis will be further studied in vitro and in vivo. The clinical relevance of these targets will be explored in several cohorts of patients by immunohistochemistry on Tissue Microarrays. Studying the profile of paired tumors and metastases provides a unique tool to decipher the mechanisms of tumor progression. Fully understanding the metastatic process will ultimately lead to the development of better targeted therapies and thus to improved outcomes for ARMS patients. Also, these same steps are being followed in our laboratory for Ewing Sarcoma, another developmental tumor with discouraging survival rates for metastatic patients (<30%)4. Citation Format: Sara Sanchez-Serra, Mariona Chicon-Bosch, Paola Monaco, Laura Santana-Viera, Susana Maqueda-Marcos, Manuel Gris-Lorente, Roser Lopez-Alemany, Oscar M. Tirado. Transcriptomic analysis to unveil alveolar rhabdomyosarcoma metastatic process [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1299.
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