Oncotarget

Research Papers:

Tamoxifen synergizes with 4-(E)-{(4-hydroxyphenylimino)-methylbenzene, 1,2-diol} and 4-(E)-{(p-tolylimino)-methylbenzene-1,2-diol}, novel azaresveratrol analogs, in inhibiting the proliferation of breast cancer cells

Amruta Ronghe _, Anwesha Chatterjee, Nimee K. Bhat, Subhash Padhye and Hari K. Bhat

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Oncotarget. 2016; 7:51747-51762. https://doi.org/10.18632/oncotarget.10106

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Abstract

Amruta Ronghe1, Anwesha Chatterjee1, Nimee K. Bhat1, Subhash Padhye2, Hari K. Bhat1

1Division of Pharmacology and Toxicology, School of Pharmacy, University of Missouri-Kansas City, Kansas City, Missouri, USA

2Interdisciplinary Science and Technology Research Academy, Abeda Inamdar Senior College, Department of Chemistry, University of Pune, Pune, India

Correspondence to:

Hari K. Bhat, email: [email protected]

Keywords: breast cancer, tamoxifen, resveratrol analogs, synergistic inhibition, combination therapy

Received: December 20, 2015    Accepted: May 22, 2016    Published: June 16, 2016

ABSTRACT

We have recently shown that 4-(E)-{(4-hydroxyphenylimino)-methylbenzene, 1,2-diol} (HPIMBD) and 4-(E)-{(p-tolylimino)-methylbenzene-1,2-diol} (TIMBD), novel analogs of resveratrol (Res), selectively inhibited the proliferation of breast cancer cells. In the current study, we tested HPIMBD and TIMBD individually in combination with tamoxifen (Tam) for inhibition of growth of breast cancer cells. Tamoxifen was first tested on non-neoplastic breast epithelial cell lines and its dose that does not inhibit their growth was determined. A combination of this low dose of Tam with either of the Res analogs HPIMBD or TIMBD, resulted in synergistic inhibition of proliferation of breast cancer cells. Both estrogen receptor (ER)-positive and negative breast cancer cell lines responded to the combination. The combination resulted in a substantial decrease in IC50 values of Res analogs in all breast cancer cell lines tested. Mechanistic studies showed a synergistic increase in apoptosis and autophagy genes (beclin-1 and LC3BII/I) with the combination in ER-negative MDA-MB-231 cells. In ER-positive MCF-7 and T47D cells, the mechanism of synergy was found to be inhibition of expression of ERα and oncogene c-Myc. The combination treatment had a synergistic effect in inhibiting the colony forming and spheroid forming ability of cancer cells. Taken together, our findings indicate that a combination of Tam and Res analogs HPIMBD or TIMBD represents a novel approach to enhancing the use of Tam in therapy for breast cancers. Considering the urgent need for novel therapeutic strategies to treat ER-negative breast cancers and overcoming resistance in ER-positive cancers, this combinatorial approach is worthy of continued investigation.


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