Figure 4. TMZ inhibits GBM progression via the TAp63-MYC pathway.

(a) Cell viability assay showing suppression of proliferation in cells treated with TMZ, 75 μM. (b) Cellular invasion was suppressed by day 5, at which point the treated and control cultures were adjusted to 5 × 10⁴ cells/500 μl and subjected to Boyden chamber invasion assays. *P < 0.05 (two-tailed t-test). (c) Percentage of U87MG cells invading the Matrigel relative to control migration, following TAp63 knockdown and TMZ treatment. Corresponding mRNA analysis. *P < 0.05 (two-tailed t-test). (d) Effect of TAp63 knockdown on the U87MG cells treated with TMZ treatment at 14 days after subcutaneous transplantation in nude mice. The end volumes were compared to the volumes at implantation. Tumour growth was measured with callipers and calculated by the formula: volume = length (A) × width (B) × width (B) × 0.5, where A and B are the long and short axes respectively. TMZ in PBS was administered intraperitoneally at 15 mg/kg once a week. Data are representative of five independent experiments (n = 4). *P < 0.05 by two-tailed t-test. Photographs in (d) are representative of n = 4 mice. Bar, 10 mm. (e) MYC downregulation in recurrent tumours after TMZ plus radiotherapy (n = 20; solid line: mean difference; dashed lines: 95% confidence interval. P value by paired t-test. (f) Overall survival according to MYC downregulation (≥1.5-fold decrease in primary/recurrent (p/r) MYC mRNA), post-TMZ treatment. MYC decrease: n = 11, mean p/r = 2.65 ± 0.31 s.d.; no change: n = 9, mean p/r = 0.9 ± 0.13 s.d. P value by log-rank test.