Each point represents the mean ± SD of triplicate experiments (p > 0.05). Irradiation-induced apoptosis in EC109/R cells The apoptosis induced by 12 Gy irradiation was detected with Annexin V-FITC staining in cell lines EC109 and EC109/R. A significant difference was recognized between EC109 and EC109/R. As shown in figure 3B, about 1%–2% apoptosis was found in the selleck screening library control groups. In the radiation-treatment groups, the rate of apoptosis in EC109/R cells compared with EC109 cells was 6.81% ± 0.78% compared with 11.24% ± 1.21% at 48 h after treatment with 12 Gy irradiation

(P < 0.05). Thus, the acquirement of radio-resistance was reflected in a reduced apoptotic rate. Figure 3 Irradiation-induced apoptosis in EC109 and EC109/R cells. Cells (1 × 106 each) were seeded GSK2879552 price in 60-mm dishes and Salubrinal cost incubated for 48 h after treatment with 12 Gy irradiation. (A)Annexin V-FITC and PI (propidium iodide) staining was performed, followed by FACS analysis. (B) The percentage of apoptotic cells was counted (Figure 3A, areas 2 and 3). Similar results were obtained in three independent experiments. Errors bar represent the standard error of the mean (p < 0.05). Cytotoxicity of cisplatin,

5-fluorouracil, doxorubicin, paclitaxel or etoposide on radio-resistant EC109/R cells To examine if cellular resistance to ionizing radiation also causes cross-resistance to the chemotherapeutic agents, the effects of cisplatin, 5-fluorouracil, doxorubicin, paclitaxel and etoposide on the growth of EC109 or EC109/R cells were evaluated by determining cell viability using MTT assay. The dose-effect curves and IC50s to different treatment are shown in figure 4 and table 2. Compared with the parent cell line EC109, the IC50 value of EC109/R cells was 1.75-fold for cisplatin, 0.324-fold

for 5-fluorouracil, 0.44-fold for doxorubicin, 0.64-fold for paclitaxel and 0.81-fold for etoposide. EC109/R GPX6 cells were more sensitive than parental cells to 5-fluorouracil, doxorubicin, paclitaxel and etoposide. But the sensitivity of EC109/R to cisplatin decreased. In addition, the numbers of apoptotic cells were also determined by Annexin V staining followed by FACS analysis, which showed the same results (Figure 5). Radio-resistance increased sensitivity to chemotherapeutic drugs of 5-fluorouracil, doxorubicin, paclitaxel and etoposide significantly. But the radio-resistant subline was more resistant to cisplatin than the parent cell line EC109. Figure 4 Sensitivity of EC109 and EC109/R cells to cisplatin, 5-fluorouracil, doxorubicin, paclitaxel or etoposide. EC109 or EC109/R Cells were exposed to various concentrations of cisplatin, 5-fluorouracil, doxorubicin, paclitaxel or etoposide for 48 h, and then the viability was calculated using MTT assay. Each point represents the mean ± SD of triplicate experiments (p < 0.05). Figure 5 Apoptotic changes in EC109 and EC109/R cells treated with different drugs.