Nitric oxide-releasing derivatives of brefeldin A as potent and highly selective anticancer agents

A series of NO-donating mono- or diester derivatives of brefeldin A were designed, synthesized and biologically evaluated. Some derivatives exhibited potent antiproliferative activity with low IC₅₀ values. The most potent NO-donating hybrid 13b exhibited stronger cytotoxicity against human prostate cancer PC-3 cells, human colon carcinoma HT-29 cells and human liver cancer HepG-2 cells than BFA with IC₅₀ values of 25 nM, 160 nM and 180 nM, respectively. More importantly, compound 13b showed good selectivity between human normal and tumor liver cells with selectivity index of 33. Additionally, 13b released higher levels of NO in HepG-2 cells than L-02 cells. Further mechanism concerning cellular apoptosis showed that 13b induced apoptosis and S phase cell cycle arrest in HepG-2 cells. Incubation with 13b increased the number of HepG-2 cells with collapsed mitochondrial membrane at low concentrations in dose-dependent manner. In addition, by using the Human Apoptosis Protein Array kit, several apoptosis-related proteins, including HO-1, HO-2 and survivin, were found to be markedly downregulated by 13b in HepG-2 cells. Furthermore, in western blot assay, 13b increased the expression of Bax, Cyt c and caspase 3, and reduced the relative levels of Bcl-2, Bcl-xl and pro-caspase 3 in HepG-2 cells.