Development of a reversible quiescence model to identify signals enabling glioblastoma cancer stem cell transition between active and quiescent states

Abstract

Gliomas are the most common primary brain tumour in adults with only limited therapies available. Glioma stem cells (GSCs) are a subpopulation with tumorigenic capacity associated with increased glioma malignancy, particularly in glioblastoma (GBM), the most frequent and aggressive adult glioma (1). GSCs can enter a non-proliferative reversible quiescent state, in which they evade conventional therapies, and can re-enter the cell cycle to re-initiate tumour growth (1, 2). Quiescence is a heterogenous state with different depths, defined as ‘shallow’ and ‘deep’, depending on the rate at which cells re-enter the cell cycle (3, 4). This PhD project aims to develop a reversible GSC quiescence model using Bone Morphogenetic Protein 4 (BMP4) in combination with Fibroblast Growth Factor 2 (FGF2) for different durations (3, 4), to model different depths of quiescence. BMP4 plus FGF2 treatment results in cell cycle exit, downregulation of protein synthesis, a key hallmark of quiescence (5) and impaired tumourigenic potential. Intensity of stemness marker expression is reversibly downregulated but GSCs do not undergo neuronal differentiation, however, glial marker levels increase. Reactivation of quiescent-like GSCs by withdrawal of BMP4 and re-exposure to growth factors reverses the majority of these characteristics. A longer period of BMP4 plus FGF2 treatment induces a deeper quiescent-like state, shown by an extended period until reactivation. Proteome profiling of proliferating, quiescent-like and reactivated GSCs identified expected as well as novel changes in protein expression and overrepresented biological processes and pathways, including cell cycle, metabolic and cell adhesion-associated, which may play a role in maintaining GSCs quiescence and regulating transition between quiescent-like and reactivated states. Expression analysis of cell adhesion molecules further validates the data and points to regulatory roles. The established model and findings described in this project contribute to expose molecules and pathways that could be targeted in the future to prevent GSCs entering a quiescent state or lock them in dormancy, which in combination with conventional chemotherapy, has the potential to eradicate whole tumours and prevent recurrence.

Date of Award	2026
Original language	English
Awarding Institution	University of Plymouth
Supervisor	Claudia Barros (Director of Studies (First Supervisor)), Torsten Bossing (Other Supervisor), Jon Gil Ranedo (Other Supervisor) & Florian Siebzehnrubl (Other Supervisor)