ID #1162 Oncogenic ALK and ROS1 fusions converge on STAT3 activation and stall neural differentiation in infant-type hemispheric glioma

Abstract

ALK and ROS1 rearrangements are key drivers of infant-type hemispheric gliomas (IHG). With more than 40 known fusion partners, the impact of ALK and ROS1 oncoprotein heterogeneity on glioma biology remains largely unknown. We developed cellular models of five IHG-associated fusions: CCDC88A::ALK, PPP1CB::ALK, GOPC::ROS1, CLIP1::ROS1, and KIF21A::ROS1. Using an integrative phospho-proteomic and transcriptomic approach, we identified fusion-specific oncogenic functions, in part conferred by the 5’ fusion partner. Fusions involving proteins known to interact with the cytoskeleton, CCDC88A::ALK and CLIP1::ROS1, upregulated gene expression programs related to motility and locomotion. Live cell imaging and extracellular matrix invasion assays confirmed a significant increase cell motility and invasion phenotypes, which were impaired by abrogation of the microtubule-interacting domain and ALK/ROS1 pharmacological inhibition. All investigated fusions showed increased STAT3 activity, with heterogeneous activation of SHP2 and MAPK signaling. Disruption of STAT3 activity reduced tumor formation in vivo murine models. Multiplex immunofluorescence confirmed increased STAT3 nuclear localization and activity in murine IHG tumor models generated by in utero electroporation, as well as in primary tumor samples. ALK/ROS1-expressing tumor cells showed increased expression of early neural lineage markers. Transcriptomic analyses further revealed downregulation of neural development pathways, an effect that was reversed by ALK/ROS1 inhibition, pointing to stalled neural development programs underlying IHG formation. Our findings identify both fusion-specific and shared ALK/ROS1-driven dependencies, including common STAT3 pathway activation, which offer opportunities to develop new treatment strategies for IHG.