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Pilot Study of SOX3 SUMOylation in Glioblastoma: Exploring Post-Translational Modifications and Their Role in Tumor Biology

Drs. Dinah Qutob (Biological Sciences, Â鶹ÊÓƵ) and Adam Underwood (Math and Sciences, Walsh University)

Glioblastoma multiforme (GBM) is the most aggressive and lethal form of brain cancer, characterized by high invasiveness, and resistance to conventional therapies. The SOX (SRY HMG-Box) family of pioneer transcription factors (TF’s), regulate cellular differentiation across various tissues including the central nervous system. Recent studies have shown that SOX3 dysregulation is linked to promoting not only rapid tumor cell growth but also enhanced invasiveness. Stability, activity, and intracellular distribution of SOX proteins are shown to be modulated by mono or poly-SUMOylation, a post-translational modification (PTM) where small ubiquitin-like modifiers (SUMOs) are attached to lysine residues on target proteins by one of four SUMO isoforms. SUMOylation has been demonstrated to alter interactions between SOX proteins, DNA and other cellular proteins, influencing plasticity, a hallmark of cancer development and progression. In GBM, alterations in the SUMOylation of TF’s may help maintain cancer cell stemness and facilitate tumor cell adaptation and invasion. However, the specific role of SOX3 SUMOylation in GBM is poorly understood. This pilot study aims to characterize three predicted SUMO binding sites in SOX3. To assess the specificity of these binding sites, native and SUMO-site-mutated HaloTag-SOX3 proteins will be affinity-purified and SUMOylated in vitro followed by immunoblot analysis to determine if these PTMs occur. After confirmation, native and SUMO-mutated SOX3 will be transfected and overexpressed in heat-stressed and control U251MG glioblastoma cells. Proteins will then be isolated and immunoblotted to establish a baseline for SUMOylation. Additionally, nuclear localization of SOX3 will be examined with a live cell fluorescent HaloTag ligand (Oregon Green). Expected outcomes include identifying specific lysine residues in SOX3 that undergo SUMOylation, determining the modifying SUMO isoforms, and evaluating SUMOylation's role in SOX3 nuclear localization. These preliminary results will enhance understanding of SOX3 regulation and its implications in glioblastoma.