Inhibition of urinary bladder cancer cell proliferation by silibinin.

Silibinin, a natural compound extracted from milk thistle, has demonstrated antitumor properties in urinary bladder cancer cells; however the role of TP53 gene in these effects is unclear. In order to better understand the molecular and antiproliferative mechanisms of this compound, urinary bladder cancer cells with different TP53 gene status, RT4 (low grade tumor, wild TP53 gene), 5,637 (high grade tumor, grade 2, mutated TP53 gene) and T24 (high grade tumor, grade 3, mutated TP53 gene), were treated with several concentrations of silibinin (1; 5; 10; 50; 100 and 150 μM). Cytotoxicity, pro-oxidant effect, morphological changes, cell migration, cell cycle progression, global methylation profile and relative expression of HOXB3, c-MYC, PLK1, SMAD4, SRC, HAT, HDAC and RASSF1A genes were evaluated. The silibinin presented cytotoxic and pro-oxidant effects in the three cell lines. In mutated TP53 cells, significant interference in cell migration and cell cycle arrest at the G2/M phase was observed. Additionally, silibinin induced global DNA hypomethylation in the highest grade tumor cells. For wild-type TP53 cells, a sub-G1 apoptotic population was present. Furthermore, there was modulation of gene expression responsible for cell growth (SMAD and c-MYC), migration (SRC), cell cycle kinetics (PLK1), angiogenesis (HOXB3) and of genes associated with epigenetic events such as DNA acetylation (HAT) and deacetylation (HDAC). In conclusion, the silibinin inhibited the urinary bladder tumor cell proliferation independently of TP53 status; however cell cycle effects, gene expression changes and alteration of cell migration are dependent on TP53 status. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.