Dottorato in BIOLOGIA CELLULARE E DELLO SVILUPPO

Titolo della tesi: Molecular expression and characterisation of non-coding RNA in tumor growth and invasiveness of glioblastoma stem-like cells

Glioblastoma (GBM) is an aggressive form of glioma in adults that owes its worse characteristics, like recurrence and resistance to therapy, mainly to GBM stem-like cells (GSCs). In vitro studies employ GSCs to generate self-renewing cell lines that can mimic the original tumor. We performed analyses on our collection of patient-derived GSC lines to study long non-coding RNAs (lncRNAs) and micro RNAs (miRNAs), important oncogenic drivers and tumor suppressors in many tumors. Our work revealed that the microRNA miR-370-3p is significantly down-regulated in GSCs compared to a normal control and, when restored, the proliferation, migration and clonogenic abilities of GSCs are impaired. Another effect of miR-370-3p restoration became clear after gene expression analyses, which identified several transcripts involved in Epithelial to Mesenchymal Transition (EMT), and Hypoxia signalling pathways. Surprisingly, among the genes down-regulated as a result of miR-370-3p restored expression, we found more genes correlated to GBM, like the EMT-inducer high-mobility group AT-hook 2 (HMGA2), the master transcriptional regulator of the adaptive response to hypoxia, Hypoxia-inducible factor (HIF)1A, and the long non-coding RNA (lncRNA) Nuclear Enriched Abundant Transcript (NEAT1). In particular, NEAT1 is an oncogenic lncRNA, associated to worse prognosis for several cancers: we found by luciferase assay that miR-370-3p directly binds NEAT1, so that the expression levels of these ncRNAs are inversely correlated in GSCs. Our results suggest that a complex “cascade” interplaying among different ncRNAs is partially responsible for GBM’s most malignant features. Indeed, miR-370-3p shows a prominent tumor-suppressor function by targeting mRNAs involved in EMT, in hypoxia pathways, and cell growth and the invasiveness enhancer NEAT1, making this microRNA another promising candidate for novel GBM treatments.