Suberoylanilide Hydroxamic Acid, an Inhibitor of Histone Deacetylase, Enhances Radiosensitivity and Suppresses Lung Metastasis in Breast Cancer In Vitro and In Vivo

Hui-Wen Chiu,Wei-Jan Huang,Ying-Jan Wang,Ya-Ling Yeh,Pinpin Lin,Sheng-Yow Ho,Yi-An Chen,Yi-Shiou Chiou,Yi-Ching Wang,Irina U Agoulnik

doi:10.1371/journal.pone.0076340

Abstract

Triple-negative breast cancer (TNBC), defined by the absence of an estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 expression, is associated with an early recurrence of disease and poor outcome. Furthermore, the majority of deaths in breast cancer patients are from metastases instead of from primary tumors. In this study, MCF-7 (an estrogen receptor-positive human breast cancer cell line), MDA-MB-231 (a human TNBC cell line) and 4T1 (a mouse TNBC cell line) were used to investigate the anti-cancer effects of ionizing radiation (IR) combined with suberoylanilide hydroxamic acid (SAHA, an inhibitor of histone deacetylase (HDAC)) and to determine the underlying mechanisms of these effects in vitro and in vivo. We also evaluated the ability of SAHA to inhibit the metastasis of 4T1 cells. We found that IR combined with SAHA showed increased therapeutic efficacy when compared with either treatment alone in MCF-7, MDA-MB-231 and 4T1 cells. Moreover, the combined treatment enhanced DNA damage through the inhibition of DNA repair proteins. The combined treatment was induced primarily through autophagy and ER stress. In an orthotopic breast cancer mouse model, the combination treatment showed a greater inhibition of tumor growth. In addition, SAHA inhibited the migration and invasion abilities of 4T1 cells and inhibited breast cancer cell migration by inhibiting the activity of MMP-9. In an in vivo experimental metastasis mouse model, SAHA significantly inhibited lung metastasis. SAHA not only enhances radiosensitivity but also suppresses lung metastasis in breast cancer. These novel findings suggest that SAHA alone or combined with IR could serve as a potential therapeutic strategy for breast cancer.

Highlights

Histone acetylation, controlled by histone acetylases and histone deacetylases (HDACs), modifies nucleosome and chromatin structures and regulates gene expression [1,2]
The viability of the cells was observed at different concentrations of suberoylanilide hydroxamic acid (SAHA) or ionizing radiation (IR) for 24 hrs in MCF-7, MDA-MB-231 and 4T1 cells (Figs. 1B&1C)
Enhanced toxicity in breast cancer cells was found for the combined treatment compared with SAHA or IR treatment alone for 24, 36 and 48 hrs

Summary

Introduction

Histone acetylation, controlled by histone acetylases and histone deacetylases (HDACs), modifies nucleosome and chromatin structures and regulates gene expression [1,2]. HDAC inhibitors have been shown to induce tumor cell differentiation, apoptosis, and/or growth arrest in several in vitro and in vivo experimental models [2]. One of these HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA), has been Food and Drug Administration approved for patients with cutaneous T-cell lymphoma who have failed prior therapies [6]. It was reported that SAHA inhibits brain metastatic colonization in a model of triple-negative breast cancer and induces DNA double-strand breaks (DSBs) [12]. Previous studies have demonstrated that the expression of matrix metalloproteinase-9 (MMP-9) has been associated with a high potential of metastasis in several human carcinomas including breast cancer [13]. Our group has shown that HTPB, a novel HDAC inhibitor, inhibits lung cancer cell migration via reduced activities of MMPs, RhoA, and focal adhesion complex [14]

Methods

Results

Conclusion