Rates Of Radionecrosis In Re-Irradiation Of Brain Metastases Using Hypofractionated Stereotactic Radiotherapy

Abstract

Transgelin-2 is known to induce actin polymerization, thereby playing a critical role in cytoskeletal reorganization leading to cell proliferation, migration/invasion, and therapeutic resistance in GBM and other malignancies. This study aims to establish Transgelin-2 as a potential therapeutic target in GBM and to demonstrate that targeting transgelin-2 by pharmacological inhibitors would provide a novel strategy for therapeutic intervention. Materials/Methods: RNAi-mediated TAGLN-2 knockdown (KD) approach was employed to assess the functions of Transgelin-2 in PDX GBM cell lines. A series of in-vitro functional assays was performed to assess the role of Transgelin-2 in these cell lines. Structure-based computational screening approach was employed to identify small-molecule inhibitors of Transgelin-2. Subsequently, the efficacy of these inhibitors to inhibit Transgelin-2-mediated cell proliferation/survival, invasion, and colony-formation was evaluated. Results: RNAi-mediated silencing Transgelin-2 significantly inhibited proliferation, survival, clonal expansion, and invasion of GBM 08-387 and 3359 PDX cell lines in vitro. In-silico virtual screenings identified potential Transgelin-2 binding candidates and were predicted to be able to permeate blood-brain barrier. In vitro binding study confirmed that these compounds inhibit the Transgelin-2-dependent actin-polymerization, and significantly compromised the proliferation invasion of GBM cells as assessed by proliferation, survival, clonal expansion, and invasion of GBM 08-387 and 3359 PDX cell lines. Furthermore, it is noteworthy that it is more likely that other pro-invasion pathways like MMP2/9-pathways may compensate for loss of function of transgelin-2 and needs to be addressed as well. MMP2 and MMP9 are important determinants in cell migration/invasion and found to be differentially upregulated in human GBM tissue compared to normal brain tissue Therefore, a combinatorial approach including Transgelin-2 inhibitor and MMP inhibitor may provide additive/synergistic outcome. Conclusion: Our data suggest that Transgelin-2 may serve as a potential therapeutically vulnerable target in GBM. Importantly, select small molecule inhibitors of Transgelin-2 that inhibit cell proliferation, invasion and therapeutic resistance may have potential preclinical trials.