Halofuginone and artemisinin synergistically arrest cancer cells at the G1/G0 phase by upregulating p21Cip1 and p27Kip1

// Guoqing Chen 1, 2, * , Ruihong Gong 1, * , Xianli Shi 3 , Dajian Yang 2 , Ge Zhang 1 , Aiping Lu 1 , Jianbo Yue 3 , Zhaoxiang Bian 1 1 School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China 2 Chongqing Academy of Chinese Materia Medica, Chongqing, China 3 Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China * These authors have contributed equally to this work Correspondence to: Jianbo Yue, email: jianbyue@cityu.edu.hk Zhaoxiang Bian, email: bzxiang@hkbu.edu.hk Keywords: halofuginone, artemisinin, synergy, cell proliferation, cell cycle Received: February 24, 2016     Accepted: June 9, 2016     Published: July 1, 2016 ABSTRACT Combinational drug therapy is one of the most promising strategies in modern anticancer research. Traditional Chinese medicine (TCM) formulas represent a wealth of complex combinations proven successful over centuries of clinical application. One such formula used to treat a variety of diseases, including cancer, contains two herbs, whose main active components are Halofuginone (HF) and Artemisinin (ATS). Here we studied the anticancer synergism of HF and ATS in various cancer cell lines and in a xenograft nude mice model. We found that the HF-ATS combination arrested more cells at the G1/G0 phase than either one alone, with the concomitant increased levels of CDK2 inhibitors, p21 Cip1 and p27 Kip1 . By knocking down p21 Cip1 and p27 Kip1 separately or simultaneously in HCT116 cells and MCF-7 cells, we found that p21 Cip1 was required for HF induced G1/G0 arrest, whereas p21 Cip1 and p27 Kip1 were both required for ATS or HF-ATS combination-mediated cell cycle arrest. Moreover, HF-ATS combination synergistically inhibited tumor growth in xenograft nude mice, and this was associated with the increased levels of p21 Cip1 and p27 Kip1 . Collectively, these data indicate that the upregulation of p21 Cip1 and p27 Kip1 contributes to the synergistic anticancer effect of the HF-ATS combination.