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The role of autophagy and Beclin-1 in radiotherapy-induced apoptosis in thyroid carcinoma cells.

BACKGROUND/OBJECTIVES
Thyroid cancer (TC), especially primary squamous cell carcinoma (SCC), is an aggressive malignant tumor which usually resists radiotherapy (RT). We wanted to understand the mechanism of incomplete response of RT in TC cells.


METHODS
SCC cell line SW579 cells were exposed to X-rays. Apoptosis and autophagy were measured by FACS; 3MA, inhibitor of autophagy, and Beclin-1 siRNA were used to investigate the effect of autophagy on radiation-induced TC cell apoptosis.


RESULTS
RT could induce TC cell apoptosis through death receptor as well as mitochondrial pathway. Radiotherapy also induces autophagy and increases expression of autophagy-associated proteins Beclin-1 and LC3. Moreover, inhibition of autophagy by 3MA and Beclin-1 siRNA enhanced radiation-induced apoptosis, through up-regulation of the expression of p53.


CONCLUSION
RT-induced autophagy resists apoptosis by the p53 pathway and an incomplete response to RT may be associated with autophagy in TC patients.