STEM-18. A HIGH THROUGHPUT NEUROSPHERE BASED COLONY FORMATION ASSAY TO VALIDATE DRUG AND RADIATION EFFECTIVENESS IN PATIENT DERIVED XENOLINES

Abstract Glioblastoma (GBM) is a primary malignant brain tumor developed from normal astrocytes. GBM patients’ median survival is less than 2 years despite safe surgical resection, fractionated conventional radiation, and temozolomide (TMZ) therapy. Few currently used drugs are successful in GBM although there are many FDA approved blood-brain barrier (BBB) penetrant drugs, for other uses that have not been screened in GBM. We utilized a panel of 734 of these BBB penetrant drugs in different GBM patient derived xenolines (PDX) along with acquired radio-resistant derivatives (-RT) including X1441, JX14P, JX14P-RT, JX39P, JX39P-RT and normal human astrocytes (NHA) as control and screened for viability with Cell Titer-Glo. We identified multiple candidate drugs that preferentially killed GBM PDX cells at 10 µM relative to NHA control. As we used stem cell media (serum free) in our drug screening study, it indicates that the potent drugs are also effective in killing cancer stem cells or brain tumor initiating cells. These drugs had targets ranging from PDGFR, DNA/RNA synthesis, as well as other kinase inhibitors. We developed a high throughput (HT), neurosphere based colony formation assay (CFA) in 96-well plate to screen multiple drugs and doses in combination with radiation. For visualizing the colonies, we use a Cytation 5 imager at 4X resolution and count the colonies based on parameters including object size, width, intensity and others. We plan on validating our drug screen and HT-CFA assay with high throughput PamChip kinase activity assays and with in vivo orthotopic tumor PDX models.