To understand the mechanisms underlying glioblastoma resistance to RT or RT+TMZ, we isolated treatment-resistant clonogenic cells from three established CD133+ GSC cultures [7], [42] by treating them with fractionated RT (4 Gy/fraction, 3 fractions per week for 1 wk) or concomitant RT plus TMZ (5 μM) followed by adjuvant TMZ (10 μM) as described in Materials and Methods and Figure S1. Here, PROM1 is linked to glioblastoma.