Oncotarget

Research Papers:

TRIP-Br1 oncoprotein inhibits autophagy, apoptosis, and necroptosis under nutrient/serum-deprived condition

Samil Jung _, Chengping Li, Jingjing Duan, Soonduck Lee, Kyeri Kim, Yeonji Park, Young Yang, Keun-Il Kim, Jong-Seok Lim, Chung-Il Cheon, Young-Sook Kang and Myeong-Sok Lee

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Oncotarget. 2015; 6:29060-29075. https://doi.org/10.18632/oncotarget.5072

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Abstract

Samil Jung1,*, Chengping Li1,*, Jingjing Duan1, Soonduck Lee1, Kyeri Kim1, Yeonji Park1, Young Yang1, Keun-Il Kim1, Jong-Seok Lim1, Chung-Il Cheon1, Young-Sook Kang2, Myeong-Sok Lee1

1Department of Life Systems, Sookmyung Women’s University, Seoul, 140-742, South Korea

2College of Pharmacy, Sookmyung Women’s University, Seoul, 140-742, South Korea

*These authors have contributed equally to this work

Correspondence to:

Myeong-Sok Lee, e-mail: mslee@sookmyung.ac.kr

Keywords: TRIP-Br1, autophagy, apoptosis, necroptosis, nutrient/serum starvation

Abbreviations: TRIP-Br1, Transcriptional regulator interacting with the PHD-bromodomain 1; ROS, Reactive Oxygen Species; XIAP, X-linked inhibitor of apoptosis protein; PCD, Programed cell death

Received: May 28, 2015     Accepted: August 10, 2015     Published: August 21, 2015

ABSTRACT

TRIP-Br1 oncogenic protein has been shown to have multiple biological functions in cells. In this study, we demonstrate that TRIP-Br1 functions as an oncoprotein by inhibiting autophagy, apoptosis, and necroptosis of cancer cells and eventually helping them to survive under the nutrient/serum starved condition. TRIP-Br1 expression level was significantly increased in conditions with low levels of nutrients. Nutrient depleted conditions were induced by culturing cancer cells until they were overcrowded with high cell density or in media deprived of glucose, amino acids, or serum. Among them, serum starvation significantly enhanced the expression of TRIP-Br1 only in all tested breast cancer cell lines (MCF7, MDA-MB-231, T47D, MDA-MB-435, Hs578D, BT549, and MDA-MB-435) but not in the three normal cell lines (MCF10A, HfCH8, and NIH3T3). As compared with the control cells, the introduction of TRIP-Br1 silencing siRNA into MCF7 and MDA-MB-231 cells accelerated cell death by inducing apoptosis and necroptosis. In this process, TRIP-Br1 confers resistance to serum starvation-induced cell deaths by stabilizing the XIAP protein and inhibiting cellular ROS production. Moreover, our data also show that the intracellular increase of TRIP-Br1 protein resulting from serum starvation seems to occur in part through the blockage of PI3K/AKT signaling pathway.


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