2.3. IC50 Determination Assay

U251 or U251 TMZ-R cells were plated onto 96-well plates at a density of 2.5 × 10⁴ cells/well. Twenty-four hours later, cells were treated with TMZ at increasing concentrations (0.001–1000 μM). Following 5 days, cells were counted using Beckman Coulter counter (Beckman Coulter Life Sciences, Indianapolis, IN, USA). Results are presented as the percentage of confluence compared to untreated cells.