Thymoquinone Inhibits Bone Metastasis of Breast Cancer Cells Through Abrogation of the CXCR4 Signaling Axis.

Muthu K Shanmugam,Arunachalam Chinnathambi,Lina H K Lim,Kwang Seok Ahn,Chern Chiuh Woo,Annie Hsu,Kwong Huat Benny Tan,Frank Arfuso,Tahani Awad Alahmadi,Gautam Sethi,Yi Yuan,Alan Prem Kumar,Ruby Yun-Ju Huang,Sulaiman Ali Alharbi,Angele Pei Fern Koh

doi:10.3389/fphar.2018.01294

Abstract

Overexpression of chemokine receptor type 4 (CXCR4) has been found to be associated with increased cell proliferation, metastasis and also act as an indicator of poor prognosis in patients with breast cancer. Therefore, new agents that can abrogate CXCR4 expression have potential against breast cancer metastasis. In this study, we examined the potential effect of thymoquinone (TQ), derived from the seeds of Nigella sativa, on the expression and regulation of CXCR4 in breast cancer cells. TQ was found to inhibit the expression of CXCR4 in MDA-MB-231 triple negative breast cancer (TNBC) cells in a dose- and time-dependent manner. It was noted that suppression of CXCR4 by TQ was possibly transcriptionally regulated, as treatment with this drug caused down-regulation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation and suppression of NF-κB binding to the CXCR4 promoter. Pretreatment with a proteasome inhibitor and/or lysosomal stabilization did not affect TQ induced suppression of CXCR4. Down-regulation of CXCR4 was further correlated with the inhibition of CXCL12-mediated migration and invasion of MDA-MB-231 cells. Interestingly, it was observed that the deletion of p65 could reverse the observed anti-invasive/anti-migratory effects of TQ in breast cancer cells. TQ also dose-dependently inhibited MDA-MB-231 tumor growth and tumor vascularity in a chick chorioallantoic membrane assay model. We also observed TQ (2 and 4 mg/kg) treatment significantly suppressed multiple lung, brain, and bone metastases in a dose-dependent manner in a metastasis breast cancer mouse model. Interestingly, H&E and immunohistochemical analysis of bone isolated from TQ treated mice indicated a reduction in number of osteolytic lesions and the expression of metastatic biomarkers. In conclusion, the results indicate that TQ primarily exerts its anti-metastatic effects by down-regulation of NF-κB regulated CXCR4 expression and thus has potential for the treatment of breast cancer.

Highlights

Breast cancer is the second most common cancer that afflicts women, with an estimated 1.67 million women diagnosed with breast cancer in 2012 (Bray et al, 2012; Torre et al, 2015)
The present study was designed to investigate the effect of TQ on both CXCR4 expression and function in BT-549 and MDA-MB-231 triple negative breast cancer (TNBC) cells and in a metastatic murine model
Previous studies have shown that CXCR4 undergoes ubiquitination at its lysine residue, followed by degradation (Kukreja et al, 2005; Shanmugam et al, 2011b); we examined the likelihood that TQ may augment the rate of CXCR4 degradation through the stimulation of proteasomes

Summary

Introduction

Breast cancer is the second most common cancer that afflicts women, with an estimated 1.67 million women diagnosed with breast cancer in 2012 (Bray et al, 2012; Torre et al, 2015). Breast cancer ranked fifth in cancer-associated deaths among all cancers globally in 2012 (Bray et al, 2012; Torre et al, 2015). Interactions between chemokines and their cognate receptors play important roles in tumor metastasis. The interaction between chemokine receptor type 4 (CXCR4) and its cognate ligand stromal-derived factor-1 (SDF1 or CXCL12) plays a crucial role in the regulation of migration and metastasis in a variety of solid tumors including breast cancer (Balkwill, 2004a,b). In the present study, we investigated the effect of thymoquinone on the SDF1/CXCR4 signaling axis

Methods

Results

Conclusion