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Breast cancer is the most common female cancer with considerable metastatic potential, explaining the need for new candidates that inhibit tumor metastasis. In our study, betulinic acid (BA), a kind of pentacyclic triterpenoid compound derived from birch trees, was evaluated for its anti-metastasis activity in vitro and in vivo. BA decreased the viability of three breast cancer cell lines and markedly impaired cell migration and invasion. In addition, BA could inhibit the activation of stat3 and FAK which resulted in a reduction of matrix metalloproteinases (MMPs), and increase of the MMPs inhibitor (TIMP-2) expression. Moreover, in our animal experiment, intraperitoneal administration of 10 mg/kg/day BA suppressed 4T1 tumor growth and blocked formation of pulmonary metastases without obvious side effects. Furthermore, histological and immunohistochemical analyses showed a decrease in MMP-9 positive cells, MMP-2 positive cells and Ki-67 positive cells and an increase in cleaved caspase-3 positive cells upon BA administration. Notably, BA reduced the number of myeloid-derived suppressor cells (MDSCs) in the lungs and tumors. Interestingly, in our caudal vein model, BA also obviously suppressed 4T1 tumor pulmonary metastases. These findings suggested that BA might be a potential agent for inhibiting the growth and metastasis of breast cancer.

Osteosarcoma is the most common primary malignancy of bone and characterized by an appendicular primary tumor with a high rate of metastasis to the lungs. Unfortunately, there is no effective strategy to treat osteosarcoma in current clinical practice. In this study, the anticancer effects and potential mechanisms of nifuroxazide, an oral nitrofuran antibiotic, on two osteosarcoma cell lines were investigated. The results of the antiproliferative activity in vitro showed that nifuroxazide inhibited cell proliferation of UMR106 and MG63 cells in a dose- and time-dependent manner. Interestingly, nifuroxazide showed low toxicity to non-tumor cells (HEK 293 T). In addition, ROS-mitochondrial mediated apoptosis was observed after treatment of nifuroxazide. Moreover, nifuroxazide could significantly inhibit osteosarcoma cells migration and invasion via p-Stat3, MMP-2 and MMP-9 mediated signaling pathway. Taken together, our results suggested that nifuroxazide could be a promising agent for osteosarcoma treatment by inhibiting cell proliferation, inducing cell apoptosis and impairing cell migration and invasion.