Members of the
tumor necrosis factor (TNF) transmembrane
cytokine superfamily, such as TNFα and
Fas ligand (FasL), play crucial roles in
inflammation and immunity. TRAIL is a member of this superfamily with the ability to selectively trigger
cancer cell death but does not motive cytotoxicity to most normal cells.
Troglitazone are used in the cure of type II diabetes to reduce
blood glucose levels and improve the sensitivity of an amount of tissues to
insulin. In this study, we revealed that
troglitazone could trigger TRAIL-mediated apoptotic cell death in human
lung adenocarcinoma cells. Pretreatment of
troglitazone induced activation of PPARγ in a dose-dependent manner. In addition conversion of LC3-I to LC3-II and PPARγ was suppressed in the presence of
GW9662, a well-characterized PPARγ antagonist. Treatment with
troglitazone resulted in a slight increase in conversion rate of LC3-I to LC3-II and significantly decreased p62 expression levels in a dose-dependent manner. This indicates that
troglitazone induced autophagy flux activation in human
lung cancer cells. Inhibition of autophagy flux applying a specific inhibitor and genetically modified ATG5
siRNA enclosed
troglitazone-mediated enhancing effect of TRAIL. These data demonstrated that activation of PPARγ mediated by
troglitazone enhances human
lung cancer cells to TRAIL-induced apoptosis via autophagy flux and also suggest that
troglitazone may be a combination therapeutic target with
TRAIL protein in TRAIL-resistant
cancer cells.