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Tocotrienol-rich mixture inhibits cell proliferation and induces apoptosis via down-regulation of the Notch-1/NF-κB pathways in NSCLC cells

Authors Rajasinghe LD, Gupta SV

Received 10 December 2016

Accepted for publication 23 February 2017

Published 15 December 2017 Volume 2017:9 Pages 103—114

DOI https://doi.org/10.2147/NDS.S129891

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Colin Mak

Peer reviewer comments 2

Editor who approved publication: Dr Chandrika Piyathilake


Lichchavi D Rajasinghe, Smiti V Gupta

Department of Nutrition and Food Science, Wayne State University, Detroit, MI, USA

Abstract: Lung cancer is one of the leading causes of cancer deaths. Non-small cell lung cancer (NSCLC), with a 5-year survival rate of 5% at stage IIIB, accounts for 80%–85% of all lung cancers. Aberrant Notch-1 expressions have been reported in lung cancer patients and could potentially be a beneficial molecular/therapeutic target against NSCLC. Tocotrienols, isomers of vitamin E, have been shown to exhibit antitumor activity via inhibition of different signaling pathways in tumor cells. Previously, we reported that delta-tocotrienol downregulates Notch-1 via NF-κB. However, the pure isomers are presently not available in quantities required for animal or clinical studies. Therefore, the objective of this study was to investigate the interactions and effects of commercially available tocotrienols (a mixture of isomers) on the Notch-1 pathway in NSCLC, adenocarcinoma (A549) and squamous cell lung cancer (H520) cell lines. A dose-dependent decrease in all growth, cell migration, and tumor invasiveness was observed in both cancer cell lines with the addition of tocotrienols. A significant induction of apoptosis was also observed using Annexin V stain in flow cytometry analysis. Since tocotrienols significantly affected proliferation, apoptosis, migration, and invasiveness, reverse transcription polymerase chain reaction and Western blot analysis were used to explore the molecular mechanisms responsible for the regulations by testing the expression of Notch-1 and its downstream genes. A dose-dependent decrease in expression of proteins was observed in Notch-1, Hes-1, Survivin, and Bcl-XL. In addition, we found a mechanism linking the NF-κB pathway and Notch-1 down-regulation from NF-κB DNA-binding activities. Thus, our data suggest that commercially available tocotrienols inhibits cell growth, migration, and tumor cell invasiveness via downregulation of Notch 1 and NF-κB while inducing apoptosis. Hence, these commercially available tocotrienol-rich mixture could potentially be an effective supplementation for lung cancer prevention.

Keywords: vitamin E, lung cancer, tocotrienol, NF-KB, apoptosis, proliferation, Notch
 

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