Isoalantolactone enhances the sensitivity of UMSCC-10A cells to radiation.

<p>(A) Representative images of the clonogenic survival assay. A colony formation assay was performed on UMSCC-10A cells treated with 2.5 or 5 μM isoalantolactone for 4 hours prior to radiation treatment with 0, 2, 4, 6, 8 Gy. After incubation for 14 days, the cells were stained with coomassie blue, and the colonies with more than 50 cells were counted. (B) The chemical structure of isoalantolactone. (C) Cell viability was measured using live/dead cells counted method. UMSCC-10A cells were pretreated with isoalantolactone and then following radiated 4 Gy at 0, 7, 15 days. The data are expressed as the mean±SEM from three independent experiments. *<i>P</i><0.01compared with the control. (D) Radiosensitization by isoalantolactone on UMSCC-10A cells, other HNSCC cell lines (UMSCC-12 cell (radiation resistant) and Cal-27 cell), other tumor cell line (HepG2 cell) and normal cells (FRT cell). SER was calculated as the ratio of the mean inactivation dose under control conditions divided by the mean inactivation dose after isoalantolactone treated (mean ± SEM, n = 4).