ORIGINAL RESEARCH COMMUNICATION A Distinct Reactive Oxygen Species Profile Confers Chemoresistance in Glioma-Propagating Cells and Associates with Patient Survival Outcome Lynnette Wei-Hsien Koh, 1, * Geraldene Rong-Hui Koh, 1, * Felicia Soo-Lee Ng, 2,3 Tan Boon Toh, 1,4 Edwin Sandanaraj, 2 Yuk Kien Chong, 2,4 Mark Phong, 3 Greg Tucker-Kellogg, 3,4,5 Oi Lian Kon, 6,7 Wai Hoe Ng, 8,9 Ivan Hua-Bak Ng, 8,9 Marie-Veronique Clement, 7,10 Shazib Pervaiz, 4,9–12 Beng Ti Ang, 2,4,8,9 and Carol Soo-Leng Tang 1,6,9 Abstract Aims: We explore the role of an elevated O 2 - :H 2 O 2 ratio as a prosurvival signal in glioma-propagating cells (GPCs). We hypothesize that depleting this ratio sensitizes GPCs to apoptotic triggers. Results: We observed that an elevated O 2 - :H 2 O 2 ratio conferred enhanced resistance in GPCs, and depletion of this ratio by pharmaco- logical and genetic methods sensitized cells to apoptotic triggers. We established the reactive oxygen species (ROS) Index as a quantitative measure of a normalized O 2 - :H 2 O 2 ratio and determined its utility in predicting chemosensitivity. Importantly, mice implanted with GPCs of a reduced ROS Index demonstrated extended survival. Analysis of tumor sections revealed effective targeting of complementarity determinant 133 (CD133)- and nestin-expressing neural precursors. Further, we established the Connectivity Map to interrogate a gene signature derived from a varied ROS Index for the patterns of association with individual patient gene ex- pression in four clinical databases. We showed that patients with a reduced ROS Index demonstrate better survival. These data provide clinical evidence for the viability of our O 2 - :H 2 O 2 -mediated chemosensitivity profiles. Innovation and Conclusion: Gliomas are notoriously recurrent and highly infiltrative, and have been shown to arise from stem-like cells. We implicate an elevated O 2 - :H 2 O 2 ratio as a prosurvival signal in GPC self- renewal and proliferation. The ROS Index provides quantification of O 2 - :H 2 O 2 -mediated chemosensitivity, an advancement in a previously qualitative field. Intriguingly, glioma patients with a reduced ROS Index correlate with longer survival and the Proneural molecular classification, a feature frequently associated with tumors of better prognosis. These data emphasize the feasibility of manipulating the O 2 - :H 2 O 2 ratio as a therapeutic strategy. Antioxid. Redox Signal. 00, 000–000. 1 Department of Research, National Neuroscience Institute, Singapore, Singapore. 2 Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore. 3 Lilly-Singapore Centre for Drug Discovery (Eli Lilly and Company), Singapore, Singapore. 4 Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. 5 Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore. 6 National Cancer Centre, Humphrey Oei Institute of Cancer Research, Singapore, Singapore. 7 Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. 8 Department of Neurosurgery, National Neuroscience Institute, Singapore, Singapore. 9 Duke-NUS Graduate Medical School, Singapore, Singapore. 10 NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore. 11 Singapore-MIT Alliance, Singapore, Singapore. 12 Cancer Science Institute, National University of Singapore, Singapore, Singapore. *Authors contributed equally to this work. ANTIOXIDANTS & REDOX SIGNALING Volume 00, Number 00, 2013 ª Mary Ann Liebert, Inc. DOI: 10.1089/ars.2012.4999 1