In vitro efficacy of P276-00 caused by G1 arrest in HNSCC cells (a) Anti-proliferative effect of P276-00 on HNSCC cells using CCK-8 assay. Cells (Detroite-562, filled circles; SCC25, filled triangles, and FaDu, filled boxes) were treated to 5 different concentrations of P276-00 (range: 0.1-10 μM) and measured after 48 hours. Here data is expressed in % cytotoxicity mean ± S.E.M. (n = 3). The IC50 of each cell line was calculated. (b) Flow cytometric analysis of asynchronous population of FaDu cells exposed to either P276-00 (1 and 3 μM) or DMSO for different time points (12, 16, 24, 48 and 72 hours). Histograms of cellular DNA content obtained by flow cytometry have been represented. The (%) DNA content for each phase of the cell cycle is indicated, which was determined by ModFit analysis.