Sensitizing TRAIL­resistant A549 lung cancer cells and enhancing TRAIL­induced apoptosis with the antidepressant amitriptyline.

Tumor necrosis factor­related apoptosis­inducing ligand (TRAIL) is a cytokine with the potential to induce cancer cell­specific apoptosis with minimal toxicity to normal cells. Therefore, the resistance of certain cancer cells to TRAIL is a major concern and agents that can either enhance TRAIL capabilities or overcome TRAIL resistance are necessary for the development of cancer treatments. The present study investigated whether the antidepressant drug amitriptyline could sensitize TRAIL­resistant A549 lung cancer cells and enhance TRAIL­induced apoptosis. Antidepressants are usually prescribed to cancer patients to relieve emotional distress, such as depression or dysthymia. The present study revealed for the first time, to the best of our knowledge, that amitriptyline increased death receptor (DR) 4 and 5 expression, a requirement for TRAIL­induced cell death. Genetic inhibitors of DR4 and DR5 significantly reduced amitriptyline­enhanced TRAIL­mediated apoptosis. Additionally, the present study explored whether blocking autophagy increased DR4 and DR5 expression. Blocking autophagy flux with the final stage autophagy inhibitor chloroquine (CQ) also upregulated DR4 and DR5 expression. TRAIL in combination with amitriptyline or CQ significantly increased the expression of apoptosis­indicator proteins cleaved caspase­8 and caspase­3. The expression levels of LC3­II and p62 were significantly higher in amitriptyline­treated cells, which confirmed that amitriptyline blocks autophagy by inhibiting the fusion of autophagosomes with lysosomes. Overall, the present results contributed to understanding the mechanism responsible for the synergistic anticancer effect of amitriptyline and TRAIL and also presented a novel mechanism involved in DR4 and DR5 upregulation.

Duloxetine Enhances TRAIL-mediated Apoptosis via AMPK-mediated Inhibition of Autophagy Flux in Lung Cancer Cells.

BACKGROUND/AIM: The antidepressant duloxetine is known as a serotonin-norepinephrine reuptake inhibitor, used for treating depression and anxiety. TRAIL selectively induces cell death in a variety of tumor cells by binding to its membrane death receptor (DR). The aim of the study was to examine whether duloxetine affects TRAIL-mediated apoptosis. MATERIALS AND METHODS: Cell viability and apoptosis was measured by morphological image, crystal violet staining, MTT and LDH assay. Immunocytochemistry and western blotting techniques were applied to detect autophagy and apoptosis indicator proteins. TEM assay was used to determine the autophagy. RESULTS: Duloxetine treatment considerably sensitizes human lung adenocarcinoma cells to TRAIL-mediated apoptosis by targeting TRAIL-DR5. Treatment with duloxetine inhibited AMPK phosphorylation and resulted in increased p62 and microtubule-associated protein 1A/1B light chain 3B-II levels, indicating inhibition of autophagy flux. Blockade of DR5 with DR5-specific small-interfering RNA negatively regulated the apoptotic effect. CONCLUSION: Clinical administration of TRAIL in combination with duloxetine may serve as a therapeutic approach for the treatment of TRAIL-resistant lung cancer cells.