A broad range of dexamethasone concentrations has been used for in vitro studies,17 (link) and the concentration we used (50 µM) falls within this range.18 (link) Single cell suspension of GSCs after 3 minutes exposure to Accutase cell detachment solution (EMD Millipore) were exposed for 6 days to GSC medium containing dexamethasone 50 µM (Sigma) or GSC medium alone as control. Medium was exchanged daily. To validate the in silico prediction in vitro, GSC 3 and 6 were exposed to 0, 25, 50 and 100 µM dexamethasone over three days under stress of concomitant treatment with 500 µM of the alkylating chemotherapeutic agent temozolomide (Sigma, St Louis, MO). Medium was exchanged daily. Total proteins were extracted and analyzed with Western blotting as described above. GSCs exposed to dexamethasone for five days were co-exposed to 10 µM camtothecin19 (link) for 24 hours and cells were harvested for total RNA isolation followed by reverse transcriptase and quantitative PCR.