Sesquiterpene Alcohol Cedrol Chemosensitizes Human Cancer Cells and Suppresses Cell Proliferation by Destabilizing Plasma Membrane Lipid Rafts.

Siddhartha Kumar Mishra,Yong-Moon Lee,Seung Hyun Oh,Yun Soo Bae,Hwan Mook Kim,Jae-Sung Kim

doi:10.3389/fcell.2020.571676

Abstract

Chemosensitization of cancer cells with small molecules may improve the therapeutic index of antitumoral agents by making tumor cells sensitive to the drug regimen and thus overcome the treatment resistance and side effects of single therapy. Cell membrane lipid rafts are known to transduce various signaling events in cell proliferation. Sensitizing cancer cells may cause modulation of membrane lipid rafts which may potentially be used in improving anticancer drug response. Cedrol, a natural sesquiterpene alcohol, was used to treat human leukemia K562 and colon cancer HT-29 cell lines, and effects were observed. Cedrol decreased the cell viability by inducing apoptosis in both cell lines by activation of pro-apoptosis protein BID and inhibition of anti-apoptosis proteins Bcl-XL, Bcl-2, and XIAP. Cedrol activated the caspase-9-dependent mitochondrial intrinsic pathway of apoptosis. Furthermore, cedrol inhibited the levels of pAKT, pERK, and pmTOR proteins as well as nuclear and cytoplasmic levels of the p65 subunit of NF-κB. Cedrol caused redistribution of cholesterol and sphingomyelin contents from membrane lipid raft, which was confirmed by a combined additive effect with methyl-β-cyclodextrin (lipid raft-disrupting agent). Lipid raft destabilization by cedrol led to the increased production of ceramides and inhibition of membrane-bound NADPH oxidase 2 enzyme activity. Cholesterol/sphingomyelin-redistributing abilities of cedrol appear as a novel mechanism of growth inhibition of cancer cells. Cedrol can be classified as a natural lipid raft-disrupting agent with possibilities to be used in general studies involving membrane lipid raft modifications.

Highlights

Cancer is the result of a stepwise progressive disruption of cellular signaling cascades controlling cell proliferation, survival, and differentiation (Evan and Vousden, 2001)
In order to investigate the effect of cedrol on growth of human cancer cells, we treated a panel of human cancer cell lines and assayed the cell viability
Annexin V is a calcium-dependent phospholipid-binding protein with highaffinity phosphatidylserine, which makes it useful for analyzing apoptotic cells that are exposed with phosphatidylserine, while 7-AAD is a standard probe for cell viability that distinguishes between viable from non-viable cells, preferably used in combination with annexin V

Summary

Introduction

Cancer is the result of a stepwise progressive disruption of cellular signaling cascades controlling cell proliferation, survival, and differentiation (Evan and Vousden, 2001). Some of the commonly targeted cellular mechanisms include increased DNA repair activity (Kelley et al, 2014), regulating cell cycle checkpoints (Visconti et al, 2016), regulating redox balance (Helfinger and Schröder, 2018), modifying p53 activity (Ferreira et al, 1999), regulating the expression of the Bcl family (Hata et al, 2015), regulating drug efflux pumps, and altering drug target enzymes (Shabbits et al, 2003; Ughachukwu and Unekwe, 2012). High metabolic activity in cancer cells causes overproduction of reactive oxygen species (ROS) which further activates a variety of redox-sensitive transcription factors including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) (Gajate et al, 2009) Upon activation, it augments the pro-survival functions by activating ERK/MEK and the PI3K/AKT pathways. The intrigued role of lipid rafts in transducing cell survival and death processes indicates that alterations in the integrity of the membrane lipid rafts may directly interfere with the cell growth

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