Rhabdomyosarcoma (RMS) is an aggressive childhood soft-tissue tumor, with propensity for local invasion and distant metastasis. Exosomes are secreted vesicles that mediate paracrine signaling by delivering functional proteins and miRNA to recipient cells. The transmembrane protein CD147, also known as Basigin or EMMPRIN, is enriched in various tumor cells, as well as in tumor-derived exosomes, and has been correlated with poor prognosis in several types of cancer, but has not been previously investigated in RMS. We investigated the effects of CD147 on RMS cell biology and paracrine signaling, specifically its contribution to invasion and metastatic phenotype. CD147 downregulation diminishes RMS cell invasion and inhibits anchorage-independent growth in vitro. While treatment of normal fibroblasts with RMS-derived exosomes results in a significant increase in proliferation, migration, and invasion, these effects are reversed when using exosomes from CD147-downregulated RMS cells. In human RMS tissue, CD147 was expressed exclusively in metastatic tumors. Altogether, our results demonstrate that CD147 contributes to RMS tumor cell aggressiveness, and is involved in modulating the microenvironment through RMS-secreted exosomes. Targeted inhibition of CD147 reduces its expression levels within the isolated exosomes and reduces the capacity of these exosomes to enhance cellular invasive properties.

The oncogenic transcription factor ZNF217 orchestrates several molecular signaling networks to reprogram integrated circuits governing hallmark capabilities within cancer cells. High levels of ZNF217 expression provide advantages to a specific subset of cancer cells to reprogram tumor progression, drug resistance and cancer cell plasticity. ZNF217 expression level, thus, provides a powerful biomarker of poor prognosis and a predictive biomarker for anticancer therapies. Cancer epigenetic mechanisms are well known to support the acquisition of hallmark characteristics during oncogenesis. However, the complex interactions between ZNF217 and epigenetic processes have been poorly appreciated. Deregulated DNA methylation status at ZNF217 locus or an intricate cross-talk between ZNF217 and noncoding RNA networks could explain aberrant ZNF217 expression levels in a cancer cell context. On the other hand, the ZNF217 protein controls gene expression signatures and molecular signaling for tumor progression by tuning DNA methylation status at key promoters by interfering with noncoding RNAs or by refining the epitranscriptome. Altogether, this review focuses on the recent advances in the understanding of ZNF217 collaboration with epigenetics processes to orchestrate oncogenesis. We also discuss the exciting burgeoning translational medicine and candidate therapeutic strategies emerging from those recent findings connecting ZNF217 to epigenetic deregulation in cancer.

Rhabdomyosarcoma is a pediatric cancer associated with aggressiveness and a tendency to develop metastases. Fusion-negative rhabdomyosarcoma (FN-RMS) is the most commonly occurring subtype of RMS, where metastatic disease can hinder treatment success and decrease survival rates. RMS-derived exosomes were previously demonstrated to be enriched with miRNAs, including miR-1246, possibly contributing to disease aggressiveness. We aimed to decipher the functional impact of exosomal miR-1246 on recipient cells and its role in promoting aggressiveness. Treatment of normal fibroblasts with FN-RMS-derived exosomes resulted in a significant uptake of miR-1246 paired with an increase in cell proliferation, migration, and invasion. In turn, delivery of miR-1246-mimic lipoplexes promoted fibroblast proliferation, migration, and invasion in a similar manner. Conversely, when silencing miR-1246 in FN-RMS cells, the resulting derived exosomes demonstrated reversed effects on recipient cells’ phenotype. Delivery of exosomal miR-1246 targets GSK3β and promotes β-catenin nuclear accumulation, suggesting a deregulation of the Wnt pathway, known to be important in tumor progression. Finally, a pilot clinical study highlighted, for the first time, the presence of high exosomal miR-1246 levels in RMS patients’ sera. Altogether, our results demonstrate that exosomal miR-1246 has the potential to alter the tumor microenvironment of FN-RMS cells, suggesting its potential role in promoting oncogenesis.

Background: Breast cancer remains a major health issue, with bone metastases negatively impacting patient outcomes. The biochemical and biological functions of the exon 4-splice isoform (ZNF217-ΔE4) of the oncogenic transcription factor ZNF217 have been poorly investigated. Methods/Results: This study, for the first time, elucidates through advanced live-cell single-molecule tracking microscopy that the C-terminus of ZNF217 influences chromatin engagement and binding stability. ZNF217-ΔE4 retains its ability to be recruited and to promote positive transcriptional activity. CRISPR/Cas9-mediated silencing of the ZNF217 gene in MDA-MB-231 breast cancer cells impairs cell aggressiveness, while reintroduction of the ZNF217-ΔE4 isoform is sufficient to restore increased cell proliferation, migration, invasion, and stemness features. In vivo, ZNF217 ΔE4—although less potent than the wild-type isoform—accelerates the formation of bone marrow micrometastases. A retrospective analysis of primary breast tumors revealed that patients with high ZNF217-ΔE4 mRNA levels had a higher risk of developing bone metastases. Conclusions: Overall, this study identifies ZNF217-ΔE4 as a novel functional isoform that mediates breast cancer cell aggressiveness and bone marrow homing. It also highlights this isoform as a promising biomarker and potential therapeutic target for breast cancers at elevated risk of bone metastasis.

Étude du rôle de miR-1246 exosomal dans la signalisation paracrine et la progression tumorale du rhabdomyosarcome: Le rhabdomyosarcome (RMS) est un cancer pédiatrique agressif du muscle squelettique caractérisé par l'incapacité des myoblastes squelettiques mésenchymateux à se différencier en myocytes matures. Il est classé en 4 principaux sous-types histologiques : embryonnaire, alvéolaire, fusiforme et pléomorphe. La présence de métastases reste un défi pour un traitement efficace du RMS et contribue au faible taux de survie des patients atteints de cette maladie. Les exosomes sont de petites nanovésicules extracellulaires libérées en grande quantité par les cellules cancéreuses qui peuvent fournir des acides nucléiques et des protéines aux cellules réceptrices, modifiant ainsi leur comportement fonctionnel et favorisant la croissance et la progression tumorale. Plusieurs cargaisons exosomales ont été étudiées et leur rôle dans la progression tumorale et leur utilisation possible comme biomarqueurs pronostiques ou prédictifs de réponse au traitement ont été démontrés. Cette cargaison exosomale pourrait même servir de cible thérapeutique à des stratégies anticancéreuses. L’identification du contenu en microARN (miARN) des exosomes dérivés de cellules du RMS a révélé leur enrichissement en miARN impliqués dans la progression tumorale. MiR-1246 est l'un des miARN retrouvés enrichis dans les exosomes provenant de 2 différents sous-types de RMS. Il a été démontré dans d’autres cancers que miR-1246 favorise l'invasion tumorale et les métastases, et représente un biomarqueur de l’agressivité du cancer. Notre hypothèse est que miR-1246 pourrait jouer un rôle majeur dans la progression du RMS par le biais de la signalisation paracrine médiée par les exosomes, favorisant ainsi la prolifération, la migration et l'invasion des cellules réceptrices. Nos résultats démontrent que les exosomes isolés de cellules du RMS dans lesquelles le miR-1246 a été inhibé induisent la réversion des effets observés sur la prolifération, la migration et l’invasion de fibroblastes receveurs. Par ailleurs, lorsque des fibroblastes normaux sont exposés à des liposomes délivrant miR-1246, le phénotype observé est similaire à celui des cellules exposées aux exosomes dérivés du RMS. Ces résultats suggèrent que les changements fonctionnels obtenus dans les cellules exposées à des exosomes de RMS pourraient être dus à un effet direct du miR-1246. Des modifications de l’expression de certains ARNm cibles directes du miR-1246 ont révélé un rôle potentiel de ce miRNA dans l’activation de la voie de signalisation Wnt dans les cellules réceptrices, pouvant ainsi contribuer à l’agressivité et au développement de métastases dans le RMS. En conclusion, notre travail suggère que miR-1246 pourrait représenter un nouveau biomarqueur pronostique et/ou prédictif ou une future cible thérapeutique potentielle du RMS.