br Introduction br Breast cancer is
Breast cancer is one of the major common cancers and main causes of cancer death in women worldwide (Torre et al., 2015). Among the early breast cancer cases, 30%–40% of women can develop advanced breast cancer (Gonzalezangulo et al., 2007). Surgery, radiation and chemotherapies are the three main therapies for local disease control and metastatic breast cancer (Chen and Emens, 2013). Breast cancer is difficult to cure and drug resistance is the major problem for che-motherapies (Akar et al., 2008), so new therapeutic drugs need to be developed to relieve patients' clinical symptoms, and extend their sur-vival time.
Chinese traditional medicinal herbs are recently considered as new sources of therapeutic regimens. Artemisinin is a sesquiterpene lactone drug with peroxy group extracted from the stems and leaves of Artemisia annua L (Paddon et al., 2013). Artemisinin has been widely applied as a first-line antimalarial drug for around fifty years for the outstanding antimalarial activity. Moreover, current researches prove that derivatives of Artemisinin have effects on tumor inhibition (Galal et al., 2009; Hua et al., 2009). SM934, also known as β-aminoarteether maleate, is a novel water-soluble artemisinin analog. It has been re-ported that SM934 shows the significant effects on multiple auto-immune diseases. However, there are few studies which have shown its ability of anti-cancer (Hou et al., 2012). In this study, SM934 was linked
∗ Corresponding authors. State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, China. ∗∗ Corresponding authors.
∗∗∗ Corresponding authors.State Key Laboratory of Bioreactor Engineering, School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, China. E-mail addresses: [email protected] (X. Liang), [email protected] (Y. Tang), [email protected] (J. Liu).
1 These authors contributed equally to this work.
with Testosterone by covalent bonds. Testosterone (T) is a 19-carbon steroidal Trichostatin A (TSA) (Meikle et al., 1992). It has been widely reported that the level of Testosterone is related to prostate cancer (Harper et al., 1984; Pollard, 1998; Ribeiro et al., 1997). So, it attracted our attention whether the synthesis of SM934 and Testosterone, Testosterone and SM934 themselves have effects on breast cancer cells and offer new potential treatment choices for breast cancer.
Human cysteine cathepsins are lysosomal proteases and often found to be over-expressed in bone remodeling, breast cancer, and other diseases (Brix et al., 2008), composed of cathepsin B, C, F, H, K, L, O, S, V, X, and W (Fonoviä‡ and Turk, 2014). Cathepsin K is the most sig-nificant because it is a cysteine protease related to bone remodeling and breast cancer (Chen and Platt, 2011; Lindeman et al., 2004; Podgorski et al., 2007). Le Gallet previously reported that Cathepsin K was highly expressed in breast cancers and the expression level could be further increased if breast cancer cells metastasize to bone (Brubaker et al., 2010; Céline et al., 2007). Bcl-xL is frequently highly expressed in various cancers (Placzek and Al, 2010; Walensky, 2012). Recently some researches showed that overexpression of Bcl-xL also affects the meta-static potential of some breast cancer cells (Choi et al., 2016; Kamath et al., 2016).
In this study, we assessed the toxicity of SM934, Testosterone, the combination of SM934 and Testosterone, and SM934-Testosterone on breast cancer cells, and found SM934-Testosterone inhibited the pro-liferation and metastasis of cells. Then, the bSDTNBI (balanced sub-structure-drug-target network-based inference) method (Wu et al., 2016, 2017) was used to predict the potential targets of SM934, Tes-tosterone and SM934-Testosterone, which indicated that Cathepsin K was only targeted by SM934-Testosterone. Molecular docking also re-vealed the proper binding poses between SM934-Testosterone and Ca-thepsin K. The prediction was further verified by qPCR and western blot, which showed the mRNA and protein level of Cathepsin K was suppressed by SM934-Testosterone. We also found that suppressed Cathepsin K expression could result in the decrease of expression of Bcl-xL, suggesting that SM934-Testosterone inhibited proliferation and metastasis ability of breast cancer cells via inhibiting the expression of Cathepsin K followed by the suppressed expression of Bcl-xL. Also, a xenotransplantation model of breast cancer was established in this study, and showed that SM934-Testosterone had nearly no effects on the growth of breast cancer in this model, which indicate that the structure of the twin drug needs to be optimized in the future study.