Oncotarget

Research Papers:

Ophiopogonin B sensitizes TRAIL-induced apoptosis through activation of autophagy flux and downregulates cellular FLICE-like inhibitory protein

Uddin MD. Nazim, Jae-Kyo Jeong and Sang-Youel Park _

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Oncotarget. 2018; 9:4161-4172. https://doi.org/10.18632/oncotarget.23647

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Abstract

Uddin MD. Nazim1,*, Jae-Kyo Jeong1,* and Sang-Youel Park1

1Biosafety Research Institute, College of Veterinary Medicine, Chonbuk National University, Iksan, Jeonbuk 54596, South Korea

*These authors are equal contribution to this work

Correspondence to:

Sang-Youel Park, email: sypark@chonbuk.ac.kr

Keywords: ophiopogonin; autophagy; TRAIL; apoptosis; lung cancer cells

Received: September 19, 2017     Accepted: December 15, 2017     Published: December 23, 2017

ABSTRACT

Tumor necrosis factor related apoptosis-inducing ligand (TRAIL), a type II transmembrane protein, belongs to the TNF superfamily. Compared to other family members, TRAIL is a promising anti-cancer agent that can selectively induce apoptosis of various types of transformed cells and xenografts, with negligible cytotoxicity against normal tissues. Ophiopogonin B is a bioactive ingredient of Radix Ophiopogon japonicus, which is frequently used in traditional Chinese medicine to treat cancer. In this study, we report that Cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein (c-FLIP) is the key determinant mediating TRAIL resistance in A549 cells and Ophiopogonin B downregulates c-FLIP and enhances TRAIL-induced apoptosis by activating autophagy flux. In addition, treatment with Ophiopogonin B resulted in a slight increase in the conversion of LC3-I to LC3-II and significantly decreased p62 expression levels in a dose-dependent manner. This indicates that Ophiopogonin B induces autophagy flux activation in human lung cancer cells. Inhibiting autophagy flux by applying a specific inhibitor ATG5 siRNA with Ophiopogonin B mediated enhancement of TRAIL effects. These data demonstrate that downregulation of c-FLIP by Ophiopogonin B enhances TRAIL-induced tumor cell death by activating autophagy flux in TRAIL-resistant A549 cells, and also suggests that Ophiopogonin B combined with TRAIL may be a successful therapeutic strategy for TRAIL-resistant lung cancer cells.


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