Synergistic tumor-killing effect of radiation and berberine combined treatment in lung cancer: the contribution of autophagic cell death.

PURPOSE: Radiotherapy is the most efficacious strategies for lung cancer. The radiation-enhancing effects and the underlying mechanisms of berberine were investigated both in vitro and in vivo.

METHODS AND MATERIALS: Clonogenic survival assays were used to evaluate the radio-sensitivity of berberine on non-small-cell lung cancer. Electron microscopic observation of the features of cell death, flow cytometry of acidic vascular organelles formation, mitochondria membrane potential and cell-cycle progression, and Western blotting of caspase 3, PARP, and LC3 were performed to identify the mechanisms underlying the enhancing effects. Lewis lung carcinoma model in mice was conducted to evaluate the possible application of berberine in synergistic treatment with irradiation.

RESULTS: Compared with radiation alone (SF2 = 0.423; D(0) = 5.29 Gy), berberine at 5 and 10 muM concentrations in combination with radiation showed significant enhancement on radiation-induced clonogenic inhibition (SF2 = 0.215: D(0) = 2.70 Gy and SF2 = 0.099: D(0) = 1.24 Gy) on A549 cells. The cellular ultrastructure showed the presence of autophagosome and an increased proportion of acridine orange stain-positive cells, demonstrating that berberine enhanced radiosensitivity via autophagy. The process involved LC3 modification and mitochondrial disruption. The animal model verified the synergistic cytotoxic effect of berberine and irradiation resulting in a substantial shrinkage of tumor volume.

CONCLUSION: Supplement of berberine enhanced the cytotoxicity of radiation in both in vivo and in vitro models of lung cancer. The mechanisms underlying this synergistic effect involved the induction of autophagy. It suggests that berberine could be used as adjuvant therapy to treat lung cancer.