Fig. 6.

Curcumin-mediated radiosensitization occurs as a result of sustained ERK1/2 activation, which is further dependent on increased ROS production. A, HeLa cells were serum starved for 24 h, pretreated with DMSO, 10 μM curcumin, N-acetylcysteine, or a combination of NAC and curcumin, followed by mock irradiation or irradiation with a 6-Gy radiation dose. Pretreatment with PD98059 was used as a control for ERK1/2 phosphorylation. Cell lysates were analyzed by Western blot using antibodies against pERK1/2 and ERK1/2. B, HeLa cells were serum starved for 24 h, cotreated with increasing doses of PD98059 and DMSO or 10 μM curcumin for 8 h, followed by irradiation at 6 Gy, and the cells were harvested 6 h after radiation. Cell lysates analyzed by Western blot using antibodies against pERK1/2 and ERK1/2. C, HeLa cells treated with DMSO, 10 μM curcumin (8 h), 50 μM PD98059 (2 h), or PD98059 treatment during the last 2 h of curcumin treatment. The cells were mock-irradiated or irradiated at 6 Gy. The drugs were washed off 1 h after radiation and replated for clonogenic survival assays. Results represent the averages of three independent experiments (±S.E.).