5-demethylnobiletin promotes the formation of polymerized tubulin, leads to G2/M phase arrest and induces autophagy via JNK activation in human lung cancer cells.

5-Demethylnobiletin is a hydroxylated polymethoxyflavone found in citrus plants that shows antiproliferative activities in several cancer cell lines. In this study, we investigated the effects and underlying molecular mechanisms of 5-demethylnobiletin on inhibition of cell growth, apoptosis, cell cycle and autophagy in A549 and CL1-5 lung cancer cells. The results of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay suggested that 5-demethylnobiletin inhibited cell growth in a dose- and time-dependent manner. Flow cytometry results suggested that 5-demethylnobiletin inhibited proliferation in lung cancer cells by inducing G2/M cell cycle phase arrest but predominantly not through apoptosis. Western blot results illustrated that the blockade of the cell cycle was associated with reduced levels of cdc25 and cdc2. Notably, our results indicated that 5-demethylnobiletin induced significant abnormal microtubule dynamics in A549 and CL1-5 cells, a novel finding. Studies conducted with isolated tubulin and docking models suggest that 5-demethylnobiletin promoted the polymerization of microtubules and bound to the taxol site. Additionally, 5-demethylnobiletin might also induce autophagy via activation of the JNK signaling pathway in A549 and CL1-5 cells. Pretreatment of the cells with the autophagy inhibitor 3-methyladenine significantly potentiated 5-demethylnobiletin-induced apoptosis, suggesting that 5-demethylnobiletin-induced autophagy mitigated cell apoptosis. Further investigation revealed that 5-demethylnobiletin inhibition of CL1-5 lung cancer cell growth was reproducible in a nude mouse model. Taken together, these studies suggest that 5-demethylnobiletin has anti-lung cancer efficacy both in vitro and in vivo possibly through induction of G2/M arrest, autophagy and apoptosis.

Induction of indoleamine 2,3-dioxygenase (IDO) enzymatic activity contributes to interferon-gamma induced apoptosis and death receptor 5 expression in human non-small cell lung cancer cells.

Interferon-gamma (IFN-γ) has been used to treat various malignant tumors. However, the molecular mechanisms underlying the direct anti-proliferative activity of IFN-γ are poorly understood. In the present study, we examined the in vitro antitumor activity of IFN-γ on two human non-small-cell lung carcinoma (NSCLC) cell lines, H322M and H226. Our findings indicated that IFN-γ treatment caused a time-dependent reduction in cell viability and induced apoptosis through a FADD-mediated caspase-8/tBid/mitochondria-dependent pathway in both cell lines. Notably, we also postulated that IFN-γ increased indoleamine 2,3-dioxygenase (IDO) expression and enzymatic activity in H322M and H226 cells. In addition, inhibition of IDO activity by the IDO inhibitor 1-MT or tryptophan significantly reduced IFN-γ-induced apoptosis and death receptor 5 (DR5) expression, which suggests that IDO enzymatic activity plays an important role in the anti-NSCLC cancer effect of IFN-γ. These results provide new mechanistic insights into interferon-γ antitumor activity and further support IFN-γ as a potential therapeutic adjuvant for the treatment of NCSLC.