B-Cell Lymphoma-2 Over-Expression Protects δ-Elemene-Induced Apoptosis in Human Lung Carcinoma Mucoepidermoid Cells via a Nuclear Factor Kappa B-Related Pathway

delta-Elemene, an antitumor component, is a chemical compound isolated from Curcuma wenyujin, a Chinese traditional herb. We examined whether delta-elemene could affect apoptosis in human lung carcinoma mucoepidermoid NCI-11292 cells, and test whether and how the over-expression of B-cell lymphoma-2 (Bcl-2) and B-cell lymphoma extra large (Bcl-xL) could off-set the effect of delta-elemene on cell growth. The result demonstrated that delta-elemene significantly induced apoptosis of NCI-H292, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, DNA fragmentation measurement, Annexin V (AnV) binding of externalized phosphatidylserine and the mitochondrial probe JC-1 using flow cytometry. Treatment of NCI-H292 with delta-elemene increased both p38 mitogen-activated protein kinase (MAPK) and inducible nitric oxide synthese (iNOS) levels, suggesting these two molecules maybe relate to the apoptotic effect of delta-elemene. The cells with Bcl-2 or Bcl-xL over-expression showed an elevation of nuclear factor kappa B (NF-kappa B) activity, accompanying a significant reduction of delta-elemene-induced apoptosis. Furthermore, inhibition of NF-kappa B by IkB alpha SR, which is a powerful inhibitor of NF-kappa B, restored the ability of delta-elemene to induce apoptosis in the cells transfected with Bcl-2. These data strongly indicated that the apoptotic effect of delta-elemene on NCI-H292 was closely associated with the activity of NF-kappa B, which was up-regulated by Bcl-2 and Bcl-xL. In conclusion, delta-elemene induced apoptosis in NCI-H292 cells. The apoptotic effect of delta-elemene could be significantly offset by over-expression of either Bcl-2 or Bcl-xL. Bcl-2 and Bcl-xL were able to increase the activity of NF-kappa B, which was a known anti-apoptotic molecule in human lung cancer cells.