Figure 2

Forced SPARC expression protects against temozolomide (TMZ) and suppresses the ability of HSP27 inhibition to sensitize cells to lower concentrations of TMZ. A. Average colony forming efficiency ± SD of C1.1 and H2 plating 750 cells/60-mm dish. B. Average surviving fraction ± SD of C1.1 GFP- and H2 SPARC-GFP-expressing cells in 0 (0.1% DMSO), 1, 10, or 100 μM TMZ plating 750 cells/60-mm dish. TMZ (100 μM) suppressed survival of both clones relative to 0 drug; p ≤ 0.0048. However, SPARC-expressing cells survived better than control cells in 100 μM TMZ; * p = 0.0022. Plating 375 and 1500 cells gave similar results. C. Average colony forming efficiency ± SD of C1.1 and H2 cells transfected with control (Csi) or HSP27 siRNA (HSP27si), plating 750 cells/60-mm dish. *** p = 0.0001. D. Average surviving fraction ± SD of C1.1 and H2 cells transfected with Csi or HSP27si in the absence (0) or presence of increasing concentrations of TMZ, plating 750 cells/60-mm dish. * H2 + Csi vs. H2 + HSP27si: 100 μM TMZ; p = 0.0020. ** C1.1 + Csi vs. C1.1 + HSP27si: 20 μM TMZ; p = 0.022, 40 μM TMZ; p = 0.0026, 60 μM and 80 μM TMZ; p = 0.0001. *** H2 + Csi vs. C1.1 + Csi: 20 μM TMZ; p = 0.015, 40-100 μM TMZ; p = 0.0001. **** H2 + HSP27si vs. C1.1 + HSP27si: 20-60 μM TMZ; p ≤ 0.0055, 80 μM and 100 μM TMZ; p = 0.0002. B, C. Plating 1500 cells gave similar results.