Poster abstracts
Poster number 176 submitted by Himanshu Dashora
Translational reprogramming in hypoxic glioma stem-like cells
Himanshu R. Dashora (Department of Pathology and Medical Scientist Training Program, School of Medicine, Case Western Reserve University; Department of Cancer Sciences, Cleveland Clinic Research), Haidong Huang, Molly Guthrie, Dalya Khalife, Kayleigh R. Bauer, Shideng Bao (Department of Cancer Sciences, Cleveland Clinic Research), Gao Zhou, Frank Tedeschi (Advanced RNA Profiling Core, School of Medicine, Case Western Reserve University), Eckhard Jankowsky (Center for RNA Science and Therapeutics, School of Medicine, Case Western Reserve University), Jennifer S. Yu (Department of Cancer Sciences, Cleveland Clinic Research; Department of Radiation Oncology, Cleveland Clinic Cancer Institute)
Abstract:
Glioblastoma (GBM) is driven by therapy-resistant glioma stem-like cells (GSCs). Hypoxia defines the GBM niche and reinforces GSC self-renewal, but how translational control sustains hypoxic GSCs is poorly understood. GSCs display elevated global translation rates relative to differentiated glioma cells, implying heightened reliance on protein synthesis. To find hypoxia-responsive dependencies, we integrated ribosome profiling and RNA-sequencing on patient-derived GSCs under hypoxia and normoxia with published CPTAC-GBM proteomics. This revealed extensive translational reprogramming and 125 mRNAs with increased translation efficiency in hypoxic GSCs, prioritizing the embryonic transcription factor HOXC10 as the most strongly induced candidate. Because HOXC10 protein accumulates under hypoxia while its transcript does not, we looked to the mRNA itself. Its 5' untranslated region opens immediately after the cap with an unbroken 26-nucleotide pyrimidine tract characteristic of terminal oligopyrimidine (5'TOP) mRNAs, rare transcriptome-wide and absent from other HOX genes. mRNAs with longer such 5'TOP tracts were more strongly translated under hypoxia. Engineering this leader upstream of a luciferase reporter, we found that it conferred higher reporter protein under hypoxia than leaders in which the tract was mutated or repositioned, or HOX leaders lacking it entirely. HOXC10 knockdown reduced GSC viability, stemness, and tumorsphere formation under both oxygen conditions. These effects were significantly amplified under hypoxia, where silencing reduced S-phase and G2/M-phase fractions and suppressed G2M and E2F transcriptional programs. In orthotopic xenograft models, HOXC10 depletion significantly increased median overall survival in all four patient-derived GSC lines tested. Together, these findings place a 5' untranslated region element at the center of a translational dependency of hypoxic GSCs.
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Keywords: translational control, ribosome profiling, 5UTR