Targeted Apoptotic Effects of Thymoquinone and Tamoxifen on XIAP Mediated Akt Regulation in Breast Cancer

Authors

Shashi Rajput, Indian Institute of Technology Kharagpur
B. N. P. Kumar, Indian Institute of Technology Kharagpur
Siddik Sarkar, Virginia Commonwealth University
Subhasis Das, Indian Institute of Technology Kharagpur
Belal Azab, Virginia Commonwealth University
Prasanna K. Santhekadur, Virginia Commonwealth University
Swadesh K. Das, Virginia Commonwealth UniversityFollow
Luni Emdad, Virginia Commonwealth UniversityFollow
Devanand Sarkar, Virginia Commonwealth UniversityFollow
Paul B. Fisher, Virginia Commonwealth UniversityFollow
Mahitosh Mandal, Indian Institute of Technology Kharagpur

Document Type

Article

Original Publication Date

2013

Journal/Book/Conference Title

PLOS ONE

Volume

8

DOI of Original Publication

10.1371/journal.pone.0061342

Comments

Originally Published at http://dx.doi.org/10.1371/journal.pone.0061342

Date of Submission

November 2014

Abstract

X-linked inhibitor of apoptosis protein (XIAP) is constitutively expressed endogenous inhibitor of apoptosis, exhibit its antiapoptotic effect by inactivating key caspases such as caspase-3, caspase-7 and caspase-9 and also play pivotal role in rendering cancer chemoresistance. Our studies showed the coadministration of TQ and TAM resulting in a substantial increase in breast cancer cell apoptosis and marked inhibition of cell growth both in vitro and in vivo. Anti-angiogenic and anti-invasive potential of TQ and TAM was assessed through in vitro studies. This novel combinatorial regimen leads to regulation of multiple cell signaling targets including inactivation of Akt and XIAP degradation. At molecular level, TQ and TAM synergistically lowers XIAP expression resulting in binding and activation of caspase-9 in apoptotic cascade, and interfere with cell survival through PI3-K/Akt pathway by inhibiting Akt phosphorylation. Cleaved caspase-9 further processes other intracellular death substrates such as PARP thereby shifting the balance from survival to apoptosis, indicated by rise in the sub-G1 cell population. This combination also downregulates the expression of Akt-regulated downstream effectors such as Bcl-xL, Bcl-2 and induce expression of Bax, AIF, cytochrome C and p-27. Consistent with these results, overexpression studies further confirmed the involvement of XIAP and its regulatory action on Akt phosphorylation along with procaspase-9 and PARP cleavage in TQ-TAM coadministrated induced apoptosis. The ability of TQ and TAM in inhibiting XIAP was confirmed through siRNA-XIAP cotransfection studies. This novel modality may be a promising tool in breast cancer treatment.

Rights

Copyright: © 2013 Rajput et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Is Part Of

VCU Human and Molecular Genetics Publications