Chinese Herbal Mixture, Tien-Hsien Liquid, Induces G2/M Cycle Arrest and Radiosensitivity in MCF-7 Human Breast Cancer Cells through Mechanisms Involving DNMT1 and Rad51 Downregulation.

Chih-Jung Yao,I-Chun Lai,Hui-Ching Kuo,Jyh-Ming Chow,Chia-Lun Chang,Shuang-En Chuang,Gi-Ming Lai,Hsin-Lun Lee,Chia-Ming Yang

doi:10.1155/2016/3251046

Abstract

The Chinese herbal mixture, Tien-Hsien Liquid (THL), has been proven to suppress the growth and invasiveness of cancer cells and is currently regarded as a complementary medicine for the treatment of cancer. Our previous study using acute promyelocytic leukemia cells uncovered its effect on the downregulation of DNA methyltransferase 1 (DNMT1) which is often overexpressed in cancer cells resulting in the repression of tumor suppressors via hypermethylation. Herein, we explored the effects of THL in MCF-7 breast cancer cells that also demonstrate elevated DNMT1. The results show that THL dose-dependently downregulated DNMT1 accompanied by the induction of tumor suppressors such as p21 and p15. THL arrested cell cycle in G2/M phase and decreased the protein levels of cyclin A, cyclin B1, phospho-pRb, and AKT. DNMT1 inhibition was previously reported to exert a radiosensitizing effect in cancer cells through the repression of DNA repair. We found that THL enhanced radiation-induced clonogenic cell death in MCF-7 cells and decreased the level of DNA double-strand break repair protein, Rad51. Our observations may be the result of DNMT1 downregulation. Due to the fact that DNMT1 inhibition is now a mainstream strategy for anticancer therapy, further clinical trials of THL to confirm its clinical efficacy are warranted.

Highlights

The current mainstream modalities for cancer therapy, such as surgery, chemotherapy, and radiotherapy, often result in unsatisfactory efficacy and adverse side effects
Our results showed that Tien-Hsien Liquid (THL) diminished the expression of DNA methyltransferase 1 (DNMT1) in MCF-7 cells, and this was accompanied by the induction of p21 and cell cycle arrest in the G2/M phase
Flow cytometric analysis of the MCF-7 cell cycle revealed a dose-dependent increase in the G2/M fraction after treatment with THL compared to the phosphate-buffered saline (PBS)-treated control (Figure 2)

Summary

Introduction

The current mainstream modalities for cancer therapy, such as surgery, chemotherapy, and radiotherapy, often result in unsatisfactory efficacy and adverse side effects. Patients resort to complementary and alternative medicines for improving clinical outcomes. In this regard, Chinese herbal medicine represents a viable resource. One potential candidate is the Chinese herbal mixture, Tien-Hsien Liquid (THL), which has been used as a complementary and alternative herbal medicine for cancer for over twenty years [1]. The herbal mixture consists of extracts from 14 Chinese medicinal herbs: Cordyceps sinensis (CS), Oldenlandia diffusa (OD), Indigo Pulverata Levis (IPL, known as indigo naturalis), Polyporus. Evidence-Based Complementary and Alternative Medicine umbellatus (PU), Radix Astragali (RA), Panax ginseng (PG), Solanum nigrum L. In 2012, the safety and efficacy of THL in immune system augmentation were demonstrated in a randomized, doubleblind, placebo-controlled, parallel-group, phase IIa clinical trial for patients with refractory metastatic breast cancer [1]

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