Wingless promotes JNK/MMPs positive feedback loop mediate tumour microtubes expansion, glioma progression and neurodegeneration

Glial cells display a network of projections (cytonemes) which mediate cell to cell communication. Under pathological conditions like glioblastoma (GB), cytonemes transform into ultra-long tumour microtubes (TMs). These filopodia infiltrate through the brain, enwrap neurons and deplete wingless (Wg)/WNT, as a consequence GB progress and neurons undergo synapse loss and degeneration. Thus TMs emerge as a central cellular feature of GB which correlates with a poor prognosis in patients and animal models. Here we describe in a Drosophila model for GB the molecular mechanisms behind TMs production, infiltration and maintenance. Glial cells are initially transformed into malignant GB upon EGFR and PI3K pathways constitutive activation, afterwards GB cells establish a positive feedback loop including Wg signalling, JNK and matrix metalloproteases (MMP). In order, Frizzled1 mediates Wg signalling upregulation which activates JNK in GB. As a consequence, MMPs are upregulated and facilitate TMs infiltration in the brain, hence GB TMs network expands and mediate further wingless depletion to close the loop.