Figure 2 - Identification of potent NPC-specific compounds.

(a–f) Dose-response curves and chemical structures of controls: cycloheximide (a), etoposide (b) and carboplatin (c), and of selected newly identified compounds: dihydrocapsaicin (d), apomorphine (e) and PAPP (f). Each plot shows the fitted sigmoidal logistic curve to MTT proliferation assay readings of both astrocytes (- -- -) and neurosphere cultures (––). Values represent the mean and s.e.m. of three independent experiments. (g) Replating colony forming efficiency of pretreated neurosphere cultures. Values represent the number of progeny neurospheres arising from 2,000 or 1,000 cells plated in fresh medium after a 7-d pretreatment of NPCs with the indicated inhibitor at the estimated EC₇₅ value. As the EC₇₅ of apomorphine did not allow the recovery of sufficient cells, an EC₅₀ pretreatment was used for this agent. Sphere counts for vehicle-treated cells represent the mean and s.d. of six separate replicates conducted during two independent experiments. All other values represent the mean of two independent experiments. Asterisks indicate a reproduced statistically significant (P < 0.05) reduction in replating efficiency when compared to vehicle control. The larger P value (of the two experiments) is reported. These differences (at both 2,000 and 1,000 cells per well) were confirmed (two-tailed paired t-test) for cultures treated with PAPP (P_2,000 = 0.02; P_1,000 = 0.008) and apomorphine (P_2,000 = 0.01; P_1,000 = 0.02) in three independent trials.