Figure 3. EGFR inhibition cooperates with temozolomide to inhibit glioma cell growth.

(A) LN229, U251 and HS683 cells were left untreated or were treated for 24 h with erlotinib and subsequently exposed to vehicle or TMZ for 3 h, plated and after 7–10 days the remaining colonies were stained and counted as indicated in Materials and Methods. The mean ± SD values from three independent experiments, each conducted in duplicate, are shown in the graph, representing the number of clones relative to untreated cells. The differences between combined treatment and either treatment alone are statistically significant (Student's t-test: *P<0.05 and **P<0.01, respectively). (B) U251 and U87MG cells were plated in 96-well plates, left untreated or treated as indicated for 48 h and cell viability monitored as described in Materials and Methods. The mean ± SD values from three independent experiments, each conducted in duplicate, are shown in the graph, representing the percentage of viable cells relative to untreated cells. The differences between combined treatment and either treatment alone are statistically significant (Student's t-test: **P<0.01). (C) Representative phase-contrast micrographs of U87MG cells treated as indicated and left for 4–6 days to allow formation of MCTS. The graph indicates the mean ± SD values of MCTS formation from three independent experiments, each conducted in duplicate, expressed as the percentage of MCTS relative to untreated cells. The differences between combined treatment and either treatment alone are statistically significant (Student's t-test: ***P<0.001).