Diversity Supplement Project Summary The most common and aggressive malignant brain tumor, glioblastoma multiforme (GBM), demonstrates a 5- year survival rate of only 5.6%. Difficulties arising in the treatment of GBM include the inability of large molecular agents to permeate through the blood-brain barrier (BBB); migration of highly invasive GBM cells beyond the solid/visible tumor margin; and gross, microscopic, and genetic intratumor heterogeneity. To circumvent issues associated with standard of care and to improve the versatility of electroporation-based therapies for intracranial applications, our group has developed a novel tumor ablation strategy which utilizes bursts of bipolar PEFs to nonthermally ablate tumors. This second-generation strategy, termed high-frequency IRE (H-FIRE), demonstrates focal tissue ablation with a surrounding zone of BBB disruption (BBBD) that extends centimeters beyond the nonthermal lesion. Despite major progress in development of electroporation-based nonthermal ablation therapies, several challenges and gaps in knowledge exist. The determination of an ablation/pulsing endpoint is not currently defined and is reliant on postoperative imaging with MRI and ultrasound techniques. Therefore, building off the parent P01 grant, this Diversity Supplement proposal seeks to conduct a preliminary investigation of H-FIRE and the proposed Fourier Analysis SpecTroscopy to ablate neoplastic tissue in an orthotopic rodent GBM tumor model and determine a pulsing endpoint. This project proposal has 2 specific aims: Specific Aim 1: Preliminary investigation of FAST impedance measurements to determine a pulsing endpoint for H-FIRE ablation. H-FIRE therapy will be applied to ablate GBM tumor tissue in an orthotopic rodent GBM tumor model. It is known that the H-FIRE ablation volume reaches a saturation following a set number of bursts applied. Therefore, we will utilize the newly developed Fourier Analysis SpecTroscopy, a rapid electrical impedance spectroscopy technique, to continually monitor changes in tissue impedance throughout H- FIRE therapy. Specific Aim 2: Preliminary investigation of combinatorial H-FIRE therapy with QUAD-CTX. This pilot study will elucidate the effects of a molecular adjuvant to enhance glioma treatment with H-FIRE. H- FIRE-mediated BBB disruption facilitates enhanced drug delivery to infiltrative glioma cells invading healthy brain parenchyma. An F98 rodent glioma model, similar to that of Aim 2, will be employed. H-FIRE therapy will be administered and bioluminescent imaging used to quantify the tumor bioluminescence follow stand-alone H- FIRE therapy and combinatorial H-FIRE with newly developed QUAD-CTX.