Erik Jung, Matthias Osswald, Jonas Blaes, Benedikt Wiestler, Felix Sahm, Torsten Schmenger, Gergely Solecki, Katrin Deumelandt, Felix T. Kurz, Ruifan Xie, Sophie Weil, Oliver Heil, Carina Thomé, Miriam Gömmel, Mustafa Syed, Peter Häring, Peter E. Huber, Sabine Heiland, Michael Platten, Andreas von Deimling, Wolfgang Wick, Frank Winkler

Early and progressive colonization of the healthy brain is one hallmark of diffuse gliomas, including glioblastomas. Recently we have discovered ultra-long (> ten to hundreds of microns) membrane protrusions (tumor microtubes, TMs) that are extended by glioma cells. TMs were associated with the capacity of glioma cells to effectively invade the brain, and proliferate. Moreover, TMs were also used by some tumor cells to interconnect to one large, resistant multicellular network. Here, we performed a correlative gene expression microarray and in vivo imaging analysis, and identified novel molecular candidates for TM formation and function. Interestingly, these genes were previously linked to normal central nervous system development. Among the highest scoring genes was tweety-homologue 1 (TTYH1), which was highly expressed in a fraction of TMs in mice and patients. Ttyh1 was confirmed to be a potent regulator of normal TM morphology, TM-mediated tumor cell invasion and proliferation. Glioma cells with one or two TMs were mainly responsible for effective brain colonization, and Ttyh1 downregulation particularly affected this cellular subtype, resulting in reduced tumor progression and prolonged survival of mice. The remaining Ttyh1 deficient tumor cells, however, had more interconnecting TMs, which were associated with increased radioresistance of those small tumors. These findings imply a cellular and molecular heterogeneity in gliomas regarding formation and function of distinct TM subtypes, with multiple parallels to neuronal development, and suggest that Ttyh1 might be a promising target to specifically reduce TM-associated brain colonization by glioma cells in patients.SIGNIFICANCE STATEMENTIn this report, we identify tweety-homologue 1 (Ttyh1), a membrane protein linked to neuronal development, as a potent driver of tumor microtube (TM)-mediated brain colonization by glioma cells. Targeting of Ttyh1 effectively inhibited the formation of invasive TMs and glioma growth, but increased network formation by intercellular TMs, suggesting a functional and molecular heterogeneity of the recently discovered TMs with potential implications for future TM-targeting strategies.