Abstract A63: Identification of small molecules for GBM study

Abstract

Abstract Glioblastoma Multiforme (GBM) is the most frequent of malignant tumors of the brain. It is fatal usually within fifteen months after diagnosis. The Cancer Genome Atlas (TCGA) has surveyed the genomes of hundreds of human GBMs for presence of mutations in genes previously associated with cancer. Among those identified, three of the five most frequently mutated genes encode the well-known tumor suppressors: P53, NF1, and Pten (TCGA, 2008). We have generated genetic mouse models of GBM based on mutation in these same three tumor suppressors and they develop GBM with 100% incidence. These mouse GBMs resemble the human counterparts by all commonly used criteria for diagnosis. Extensive study of these mice and tumors has provided novel insights into the natural history of GBM development and moreover pointed at the adult neural stem cell/progenitor compartment as the most likely and frequent source of these tumors (Kwon CH, et al., 2008). We have thus isolated a cancer stem cell and demonstrated a hierarchical growth for these tumors in vivo. (Chen J, et al., 2012) In an effort to identify novel GBM specific molecular pathways that might serve as therapeutic targets, we undertook a 200,000 small compound high throughput screen using primary low passage GBM cells generated by pooling cells from multiple mouse tumors (Mut6 cells). A critical counter screen was designed to minimize compounds that targeted the cell division and DNA replication machinery of cells since many normal cells divide and this property is not unique to cancer cells. We therefore ruled out all compounds that displayed toxicity to primary mouse embryo fibroblasts (MEFs) or to primary astrocytes. At the end of the screen, we selected three lead compounds with amenable physical-chemical properties for further evaluation and development as research discovery reagents and possible translational tools for drug development. We verified the activity of one of these compounds, termed Compound X, on mouse and human GBM primary cells as well as on a subset of established cancer cell lines, but not on MEFs or primary astrocytes. We identified a rapid cellular stress response accompanied by the robust activation of a transcription factor and eventual apoptotic response that can be mimicked by glucose deprivation. Through intensive structure-activity relationship study, analogs were successfully developed for in vivo activity and also for biochemical pull-down assay. Another compound (Compound Y) also induced apoptosis, however displaying response through completely different pathway, which indicates our screen identified multiple vulnerabilities in GBM tumor cells. Citation Format: Sang Kyun Lim, Yufeng Shi, Qiren Liang, Inga Nazarenko, Shuguang Wei, Maya Palnitkar, Yanjiao Li, Woosung Cho, Noelle Williams, Bruce Posner, Jef De Brabander, Luis F. Parada. Identification of small molecules for GBM study. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr A63.