Induced apoptosis by quercetin in human colon cancer HT-29 cells through Traf6/TAK1 signaling pathway

Abstract

Objective To study the effect of quercetin on the apoptosis of human colon cancer HT-29 cells and observe the possible mechanism. Methods Human colon cancer HT-29 cells were cultured in vitro and divided into four groups, including the control group, the 16 μg/ml quercetin group, the Traf6 inhibitor group and the 16 μg/ml quercetin + inhibitor group. The cells in control group were cultured with complete medium and other groups were treated with quercetin or/and Traf6 inhibitor. Flow cytometry was used to observe the impact of quercetin on the apoptosis of HT-29 cells; Western Blot technology was used to detect the expression levels of Traf6, TAK1, p-TAK1, caspase-3, Bax and Bcl-2; RT-PCR was used to investigate the expression level of Traf6 mRNA after treating for 24 h. Results Compared with the 16 μg/ml quercetin group, the expression levels of Traf6 (0.59 ± 0.03 vs. 0.96 ± 0.04), p-TAK1 (0.43 ± 0.02 vs. 0.72 ± 0.04), caspase-3 (0.59 ± 0.03 vs. 0.70 ± 0.04), and Bax (0.48 ± 0.03 vs. 0.67 ± 0.04) were significantly decreased in 16 μg/ml quercetin + inhibitor group(P<0.05). while the expression levels of Bcl-2 (0.54 ± 0.03 vs. 0.44 ± 0.02) was significantly increased (P<0.05). Conclusions Quercetin can induce the apoptosis of human colon cancer HT-29 cells and the effective mechanism may relate to the activation of Traf6/TAK1 signaling pathway. Key words: Apoptosis; Quercetin; Human colon cancer cells; Signaling pathway