Mechanistic Elucidation of an Anti-Epileptic for the Treatment of Glioblastoma.

Glioblastoma multiforme (GBM) is a highly proliferative grade IV malignant astrocytoma with a 5-year survival rate of ~5%. The current treatment strategies for GBM including surgery, radiation, and chemotherapy face multiple challenges such as resistance to standard chemotherapeutic temozolomide (TMZ), sensitive location, and presence of blood-brain barrier that hinders permeation of various chemotherapeutics. The dire need and urgency to develop a new therapeutic for the treatment of GBM led us to explore metabolic vulnerabilities of cancer. Stiripentol (STP) is an FDA approved drug used for the treatment of Dravet's syndrome (a rare type of epilepsy) and a putative LDH inhibitor that we screened out of many metabolic inhibitors for GBM. STP showed efficacy in cytotoxicity and proliferation assay on U87 and U138 GBM cells. STP also showed efficacy in clonogenic assay and wound healing assay in GBM cells. To further explore and discover the mechanistic target of STP for the treatment of GBM, we performed apoptosis assay, cell cycle assay, and studied the expression of proteins involved in apoptosis, metastasis, and cell signaling. In addition, 3D spheroid study was performed to mimic the tumor microenvironment and the effect of STP was assessed on the same. Next, synergy studies of STP with standard of care TMZ was performed on U87 cells. Cellular toxicity studies were performed to evaluate the safety profile of STP and the combination treatment with TMZ on normal human cells. We will elucidate mechanistic basis of STP anticancer activity in GBM cells and test preclinical potential of STP in tumor xenograft model. Therefore, STP is an effective compound that can augment TMZ for GBM treatment and merits further investigation.