492 Novel BH3 Mimetic Bcl-2 Inhibitor Promotes Autophagic Cell Death and Reduces in Vivo Glioblastoma Tumor Growth

Abstract

INTRODUCTION: Anti-apoptotic members of the Bcl-2 family proteins play central roles in the regulation of cell death in glioblastoma, the most malignant type of brain tumor. Despite the advances in GBM treatment, there is still an urgent need for new therapeutic approaches. METHODS: In silico studies resulted in 500,000 molecules being screened with computer-aided drug design methods and the molecule with the highest binding affinity was selected and named BAU-243. Cell viability, IC50 value, tumor formation potential, tumor spheroid formation potential, tumor invasion studies were investigated following BAU-243 application. The molecular changes caused by Bcl-2 inhibition were demonstrated by quantitative PCR, western blot and immunofluorescence methods. In in vivo studies, glioma tumors were transplanted intracranially into Nod Scid Gamma(NSG) mice using the mouse xenograft model. RESULTS: Here, we report a novel 4-thiazolidinone derivative BH3 mimetic, BAU-243 that binds to Bcl-2 with a high affinity. BAU-243 effectively reduced overall glioblastoma cell proliferation including a subpopulation of cancer-initiating cells in contrast to the selective Bcl-2 inhibitor ABT-199. While ABT-199 successfully induces apoptosis in high BCL2-expressing neuroblastoma SHSY-5Y cells, BAU-243 triggered autophagic cell death rather than apoptosis in A172 cells, indicated by the upregulation of BECN1, ATG5, and MAP1LC3B expression. Lc3b-II, a potent autophagy marker, was significantly upregulated following BAU-243 treatment. Moreover, BAU-243 significantly reduced tumor growth in vivo in orthotopic brain tumor models when compared to the vehicle group, and ABT-199 treated animals. To elucidate the molecular mechanisms of action of BAU-243, we performed computational modeling simulations that were consistent with in vitro results. CONCLUSIONS: Results indicated that BAU-243 activates autophagic cell death by disrupting Beclin 1:Bcl-2 complex, and may serve as a potential small molecule for the treatment of glioblastoma.