Vitexin induces apoptosis and ferroptosis and suppresses malignant proliferation and invasion of bladder urothelial carcinoma through PI3K/AKT-Nrf2 axis

Abstract

Bladder urothelial carcinoma (BUC) is a type of malignant urinary system. Although several strategies have been applied in the treatment of BUC, its survival remains unsatisfactory, especially in the patients with advanced BUC. Vitexin, a natural flavonoid has exhibited the inhibitory effect on various tumors, however, its effect on BUC is still unclear. This study aimed to explore the effect of vitexin on the progression of BUC. The toxicity of vitexin on T24 and 5637 cells was detected by cell counting kit-8 (CCK-8). The effects of vitexin on proliferation, apoptosis, invasion, epithelial-mesenchymal transition (EMT) and ferroptosis in BUC cells were determined by CCK-8, flow cytometry, western blot, transwell and immunofluorescence assays. Additionally, the related mechanism was explored by examining the expression of the phosphatidylinositol-3 kinase (PI3K)/protein kinase B (AKT)-nuclear factor-erythroid 2 related factor 2 (Nrf2) pathway. Besides, in vivo validation was performed in the xenografted mice. Vitexin reduced the BUC cell viability and enhanced the apoptosis rate and the relative protein expression of p53 and cleaved-caspase3. Also, vitexin decreased the invasion number, and increased the relative protein expression of E-cadherin with the decreased N-cadherin protein level in T24 and 5637 cells. Besides, vitexin promoted the levels of ROS and MDA, while reduced the GSH level. Vitexin also increased the level of iron, but decreased the relative protein expression of xCT and GPX4. Erastin further increased the vitexin-induced iron levels, whereas inverse outcomes were observed in the application of ferrostatin-1. Additionally, vitexin decreased the relative protein levels of PI3K, p-AKT/AKT, and nuclear Nrf2, while increased the relative protein level of cytoplasmic Nrf2. Overexpression of PI3K notably inverted the effect of vitexin on cell viability, apoptosis, invasion, level of ROS and iron. Furthermore, vitexin reduced the tumor volume and weight of xenografted mice. Vitexin decreased the protein level of N-cadherin, while increased apoptosis rate of xenografted mice. In addition, vitexin reduced the relative protein levels of PI3K, p-AKT/AKT, and nuclear Nrf2 with the enhanced relative protein expression of cytoplasmic Nrf2 in xenografted mice. Moreover, vitexin decreased the relative protein expression of xCT and GPX4 and the GSH level, whereas increased the MDA level in xenografted mice. Vitexin suppressed malignant proliferation and invasion and induced apoptosis and ferroptosis of BUC involving in PI3K/AKT-Nrf2 pathway.