Open Access

Flavia W. de Faria, Nicole C. Riedel, Daniel Münter, Marta Interlandi, Carolin Göbel, Lea Altendorf, Mathis Richter, Viktoria Melcher, Christian Thomas, Rajanya Roy, Melanie Schoof, Ivan Bedzhov, Natalia Moreno, Monika Graf, Marc Hotfilder, Dörthe Holdhof, Wolfgang Hartmann, Ann-Katrin Bruns, Angela Brentrup, Friederike Liesche-Starnecker, Bruno Maerkl, Sarah Sandmann, Julian Varghese, Martin Dugas, Pedro H. Pinto, Sebastian T. Balbach, I.-Na Lu, Claudia Rossig, Oliver Soehnlein, Aysegül Canak, Martin Ebinger, Martin Schuhmann, Jens Schittenhelm, Michael C. Frühwald, Ulrich Schüller, Thomas K. Albert, Carolin Walter, Jan M. Bruder, Kornelius Kerl

• Embryonal tumor with multilayered rosettes (ETMR) is a lethal embryonal brain tumor entity. To investigate the intratumoral heterogeneity and cellular communication in the tumor microenvironment (TME), we analyze in this work single-cell RNA sequencing of about 250,000 cells of primary human and murine ETMR, in vitro cultures, and a 3D forebrain organoid model of ETMR, supporting the main findings with immunohistochemistry and spatial transcriptomics of human tumors. We characterize three distinct malignant ETMR subpopulations - RG-like, NProg-like and NB-like - positioned within a putative neurodevelopmental hierarchy. We reveal PDGFRβ+ pericytes as key communication partners in the TME, contributing to stem cell signaling through extracellular matrix-mediated interactions with tumor cells. PDGF signaling is upregulated in chemoresistant RG-like cells in vivo and plays a role in recruiting pericytes to ETMR TME by finalizing a signaling cascade which promotes the differentiation ofEmbryonal tumor with multilayered rosettes (ETMR) is a lethal embryonal brain tumor entity. To investigate the intratumoral heterogeneity and cellular communication in the tumor microenvironment (TME), we analyze in this work single-cell RNA sequencing of about 250,000 cells of primary human and murine ETMR, in vitro cultures, and a 3D forebrain organoid model of ETMR, supporting the main findings with immunohistochemistry and spatial transcriptomics of human tumors. We characterize three distinct malignant ETMR subpopulations - RG-like, NProg-like and NB-like - positioned within a putative neurodevelopmental hierarchy. We reveal PDGFRβ+ pericytes as key communication partners in the TME, contributing to stem cell signaling through extracellular matrix-mediated interactions with tumor cells. PDGF signaling is upregulated in chemoresistant RG-like cells in vivo and plays a role in recruiting pericytes to ETMR TME by finalizing a signaling cascade which promotes the differentiation of non-malignant radial glia cells, derived from our 3D model, into pericyte-like cells. Selective PDGFR-inhibition blocked the lineage differentiation into pericytes in vitro and reduced the tumor cell population in vivo. Targeting ETMR-pericyte interactions in the TME presents a promising therapeutic approach.…