The role of autophagy in TRAIL-induced apoptosis of medullary thyroid cancer TT cells / 中华内分泌外科杂志

ABSTRACT

Objective To observe the level of autophagy induced by TRAIL in TT cell line and identify the role of autophagy in TRAIL-inducing apoptosis of TT cell line.Methods The growth inhibition of TT cells was measured by MTT assay.MDC staining was used to identify the happening of autophagy.Annexin V/PI double staining was used to analyze the apoptosis rate of TT cells by flowcytometry.The protein expression of caspase-8 and Beclin1 was detected by Western blot.Results ① The growth inhibition ratio of TT cells induced by TRAIL at the concentration of 250,500,1000 and 2000 ng/ml was (3.02 ± 1.82)％,(4.87 ± 1.45)％,(7.51 ± 1.57) ％,(12.76 ± 3.23) ％ respectively,which suggested significant resistance of TT cells to TRAIL.② MDC-labeled green light vesicles was significantly increased after the treatment of TRAIL for 48 h.③ The apoptosis rate of TT cells induced by TRAIL at the concentration of 500 ng/ml and 1000 ng/ml after the pretreat ment of 3-MA for 4 h was(17.83 ± 1.54) ％ and(27.81 ± 1.79) ％ respectively,which was significantly higher than the apoptosis rate induced by TRAIL(3.70 ± 0.34) ％,(6.55 ± 0.59) ％ alone and that induced by 3-MA(7.71 ± 0.64) ％ (t =3.282,P ＜ 0.05 ; t =7.830,P ＜ 0.01).④ The combination treatment of TRAIL and 3-MA increased the cleavage of caspase-8 and down-regulated the expression of Beclin 1.Conclusion Autophagy induced by TRAIL may contributes to the resistance of TT cells to TRAIL,which can be reversed by the inhibition of autophagy.