Andrographolide radiosensitizes human esophageal cancer cell line ECA109 to radiation in vitro

Summary To explore the radiosensitivity of andrographolide on esophageal cancer cell line ECA109. The inhibition effects of andrographolide were measured using 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium (MTT) assay. Clonogenic survival assay was used to evaluate the effects of andrographolide on the radiosensitivity of esophageal cancer cells. Immunofluorescence was employed to examine Bax expression. The changes in cell cycle distribution and apoptosis were assayed using flow cytometry. The expression of NF‐κb/Cleaved‐Caspase3/Bax/Bcl‐2 was measured using Western blot analysis. DNA damage was detected via γ‐H2AX foci counting. With a clear dose and time effects, andrographolide was found to inhibit the proliferation of esophageal cell line ECA109. The results of the clonogenic survival assay show that andrographolide could markedly enhance radiosensitivity (P < 0.05) with a sensitizing enhancement ratio of 1.28. Andrographolide caused a dose‐dependent increase in Cleaved‐Caspase3/Bax protein expression and a decrease in Bcl‐2/NF‐κb expression. Apoptosis in andrographolide‐treated ECA‐109 increased significantly compared with the apoptosis in the simple drug and radiation combined with drug groups (P < 0.001; P < 0.05). Moreover, compared with the independent radiation group, the andrographolide combined with radiation group increased the number of DNA double chain breaks. Andrographolide can increase the radiosensitivity of esophageal cell line ECA109. This result may be associated with the decrease in the NF‐κb level and the induced apoptosis of esophageal cancer cells.