Green tea (Camellia sinensis) extract inhibits both the metastasis and osteolytic components of mammary cancer 4T1 lesions in mice

Green tea (Camellia sinensis, CS), a kind of Chinese tea commonly consumed as a healthy beverage, has been demonstrated to have various biological activities, including antioxidation, antiobesity and anticancer. Our study aims to investigate the antitumor, antimetastasis and antiosteolytic effects of CS aqueous extract both in vitro and in vivo using metastasis-specific mouse mammary carcinoma 4T1 cells. Our results showed that treatment of 4T1 cells with CS aqueous extract resulted in significant inhibition of 4T1 cell proliferation. CS extract induced 4T1 apoptosis in a dose-dependent manner as assessed by annexin-V and propidium iodide staining and caspase-3 activity. Western blot analysis showed that CS increased the expression of Bax-to-Bcl-2 ratio and activated caspase-8 and caspase-3 to induce apoptosis. CS also inhibited 4T1 cell migration and invasion at 0.06–0.125 mg/ml. In addition, CS extract (0.6 g/kg, orally fed daily for 4 weeks) was effective in decreasing the tumor weight by 34.8% in female BALB/c mice against water treatment control (100%). Apart from the antitumor effect, CS extract significantly decreased lung and liver metastasis in BALB/c mice bearing 4T1 tumors by 54.5% and 72.6%, respectively. Furthermore, micro-computed tomography and in vitro osteoclast staining analysis suggested that CS extract was effective in bone protection against breast cancer-induced bone destruction. In conclusion, the present study demonstrated that the CS aqueous extract, which closely mimics green tea beverage, has potent antitumor and antimetastasis effects in breast cancer and could protect the bone from breast cancer-induced bone destruction.