Mechanisms of antiprostate cancer by gum mastic: NF-κB signal as target

Aim: To study the effect of gum mastic, a natural resin, on the proliferation of androgen-independent prostate cancer PC-3 cells, and further investigate the mechanisms involved in this regulatory system, taking nuclear factor κB (NF-κB) signal as the target. Methods: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and a flow cytometer were used to detect the effect of gum mastic on the proliferation of PC-3 cells. Then, reporter gene assay, RT-PCR, and Western blotting were carried out to study the effects of gum mastic on the NF-κB protein level and the NF-κB signal pathway. The expression of genes involved in the NF-κB signal pathway, including cyclin D1, inhibitors of κBs (IκBα), and phosphorylated Akt (p-AKT), were measured. In addition, transient transfection assays with the 5× NF-κB consensus sequence promoter was also used to test the effects of gum mastic. Results: Gum mastic inhibited PC-3 cell growth and blocked the PC-3 cell cycle in the G1 phase. Gum mastic also suppressed NF-κB activity in the PC-3 cells. The expression of cyclin D1, a crucial cell cycle regulator and an NF-κB downstream target gene, was reduced as well. Moreover, gum mastic decreased the p-AKT protein level and increased the IκBα protein level. Conclusion: Gum mastic inhibited the proliferation and blocked the cell cycle progression in PC-3 cells by suppressing NF-κB activity and the NF-κB signal pathway.