Steroidal Saponins from Paris Polyphylla Suppress Malignancy of Human Lung Cancer A549 Cells

Lung cancer is the leading causes of cancer death worldwide (Siegel et al., 2014), mainly due to the difficulty of early diagnosis and the highly metastatic potential, which has being the hotspot of lung cancer research (Li et al., 2014). In fact, the metastasis has already developed before the diagnosis of lung cancer in most cases, for example, approximately 30 to 40% of patients with advanced lung cancer will develop bone metastases (Sone and Yano, 2007; Al Husaini et al., 2009). More than 90% of lethality in cancer patients is caused by metastasis and the occurrence of distant metastases resulting in a significant poor prognosis of lung cancer patients (Cheng et al., 2014). For metastasis, tumor cells invade through the basement membrane, enter the vasculature, survive without adhesion, disseminate into the circulation, and finally establish a new tumor in another organ. For migration, the cell body must modify its shape and stiffness to interact with the surrounding tissue structures. Hereby, the extracellular matrix (ECM) provides the substrate, as well as a barrier towards the advancing cell body (Friedl and Wolf, 2003; Yilmaz et al., 2007; Al Husaini et al., 2009). Depending on the tumor type and the surrounding