Abstract 3495: The novel phospholipid ether analog CLR1404 decreases glioblastoma stem cell proliferation, suppresses GBM growth, and improves survival

Abstract

Abstract Most patients treated for glioblastoma multiforme (GBM), the most common primary brain malignancy, have less than 2 years survival due to rapid recurrence. The GBM stem cell (GSC) sub-population exhibits therapeutic resistance and is hypothesized to drive tumor recurrence. Therefore, GSC-specific targeting is likely critical for improving outcome. Phospholipid ether analog, CLR1404 and its radioiodinated isosteres, exhibit cancer cell-specific uptake and prolonged retention in 57/61 cancer cell lines and xenografts (including GBM) due to affinity for cancer cell lipid rafts. In this study, we investigated the therapeutic potential of CLR1404 against GBM and its GSC subpopulation. Multiple sphere-forming GSC lines were isolated from patient specimens with IRB approval, and rigorously validated for self-renewal, multi-lineage potential, and high efficiency orthotopic tumor initiation in NOD-SCID mice. Proliferation assays were performed by addition of CLR1404 in serum-free medium for 24 hours. To test effects on stem cell properties, GSCs were treated with CLR1404, dissociated to single cells, plated at 500 cells in a 96-well plate, and allowed to form spheres (≥2-4 weeks). CLR1404 inhibition of the AKT oncogenic signaling pathway in GSCs was assayed with immunoblot analysis. In vivo, GSCs were pre-treated for 24 hours with CLR1404 prior to orthotopic injection of 200,000 live cells into immunodeficient mice. Subsequent survival curves were then constructed. CLR1404 anti-proliferative effects were seen on all 7 different GSC and GBM lines tested with IC50 values ranging between 5-10 µM using MTS assay; control normal differentiated neural cells exhibited an IC50 of approximately 40 µM. CLR1404 treatment also decreased sphere-forming ability of multiple GSC lines with IC50 values between 5-10 µM. CLR1404 inhibition of AKT activation was observed using immunoblot analysis. CLR1404 pre-treatment of GSCs significantly increased survival time in an orthotopic mouse model (Control: 59±6.1 days; CLR1404: 94±4.4 days), suggesting CLR1404 treatment of the GSC tumor initiating cells improves outcome. This data of CLR1404's therapeutic potential against GBM and its GSCs, combined with previously demonstrated tumor cell targeting specificity of CLR1404 and its radioactive isosteres, provides strong evidence for the potential of novel CLR1404-based therapies to improve GBM outcomes. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3495. doi:1538-7445.AM2012-3495