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Mol Cell Biochem. 2016 May;416(1-2):141-55. doi: 10.1007/s11010-016-2703-4. Epub 2016 Apr 15.

Thymoquinone inhibits growth of human medulloblastoma cells by inducing oxidative stress and caspase-dependent apoptosis while suppressing NF-κB signaling and IL-8 expression.

Author information

1
Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh, 11451, Kingdom of Saudi Arabia. aeashour@yahoo.com.
2
Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Kingdom of Saudi Arabia.
3
Vitiligo Research Chair, College of Medicine, King Saud University, Riyadh, Kingdom of Saudi Arabia.
4
Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh, 11451, Kingdom of Saudi Arabia.
5
Cell Biology Department, National Research Centre, Cairo, Egypt.
6
Medical and Molecular Genetics Research Chair, Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Kingdom of Saudi Arabia.
7
Biochemistry Department, Faculty of Agriculture, Cairo University, Giza, Egypt.
8
Department of Pharmacology and Toxicology, College of Pharmacy, Al-Azhar University, Cairo, Egypt.
9
Department of Oncology, Karmanos Cancer Institute, Wayne State University, Detroit, MI, USA.
10
John D. Dingell Veterans Affairs Medical Center, Detroit, MI, USA.

Abstract

Medulloblastoma (MB) is the most common malignant brain tumor of childhood. The transcription factor NF-κB is overexpressed in human MB and is a critical factor for MB tumor growth. NF-κB is known to regulate the expression of interleukin-8 (IL-8), the chemokine that enhances cancer cell growth and resistance to chemotherapy. We have recently shown that thymoquinone (TQ) suppresses growth of hepatocellular carcinoma cells in part by inhibiting NF-κB signaling. Here we sought to extend these studies in MB cells and show that TQ suppresses growth of MB cells in a dose- and time-dependent manner, causes G2M cell cycle arrest, and induces apoptosis. TQ significantly increased generation of reactive oxygen species (ROS), while pretreatment of MB cells with the ROS scavenger N-acetylcysteine (NAC) abrogated TQ-induced cell death and apoptosis, suggesting that TQ-induced cell death and apoptosis are oxidative stress-mediated. TQ inhibitory effects were associated with inhibition of NF-κB and altered expression of its downstream effectors IL-8 and its receptors, the anti-apoptotic Bcl-2, Bcl-xL, X-IAP, and FLIP, as well as the pro-apoptotic TRAIL-R1, caspase-8, caspase-9, Bcl-xS, and cytochrome c. TQ-triggered apoptosis was substantiated by up-regulation of the executioner caspase-3 and caspase-7, as well as cleavage of the death substrate poly(ADP-ribose)polymerase. Interestingly, pretreatment of MB cells with NAC or the pan-caspase inhibitor zVAD-fmk abrogated TQ-induced apoptosis, loss of cyclin B1 and NF-κB activity, suggesting that these TQ-mediated effects are oxidative stress- and caspase-dependent. These findings reveal that TQ induces both extrinsic and intrinsic pathways of apoptosis in MB cells, and suggest its potential usefulness in the treatment of MB.

KEYWORDS:

Apoptosis; Cancer; Daoy cells; Medulloblastoma; NF-κB; Thymoquinone

PMID:
27084536
DOI:
10.1007/s11010-016-2703-4
[Indexed for MEDLINE]

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