Activation of FOXO3 pathway is involved in polyphyllin I-induced apoptosis and cell cycle arrest in human bladder cancer cells

Polyphyllin I (PPI), an extract from Paris polyphylla, has been demonstrated to possess antitumor activity against multiple cancers. However, whether PPI can inhibit bladder cancer (BCa) and the underlying mechanisms have never been researched. In this study, we initially found that PPI could induce BCa cell apoptosis and cell cycle arrest, as well as inhibit cell proliferation in vitro. Additionally, PPI could effectively suppress the in vivo growth of BCa in the xenograft mice model. Furthermore, we found that forkhead box O3 (FOXO3) and its targets including BIM or NOXA were significantly upregulated in BCa cells following PPI treatment. Interestingly, we observed that FOXO3 knockdown partly reversed the effects of PPI on BCa cells. Taken together, our findings suggested that PPI exerted a cytotoxic effect in vitro and an antitumor activity in vivo against BCa partly by activating FOXO3 signaling pathway. Therefore, PPI may serve as a promising chemotherapy agent for BCa treatment.