Synergistic effect and its possible mechanisms of lidamycin in combination with TRAIL in NSCLC

This study is to investigate the effect and its possible mechanisms of lidamycin (LDM) combined with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in human non-small cell lung cancer (NSCLC) cells.  MTT assay was used to determine the growth inhibition of the two ingredients on H460 cells.  Apoptosis was examined by Annexin V-FITC/PI staining, flow cytometry assay and DNA-specific dye Hoechst 33342 staining. The level of TRAIL receptor and apoptosis-associated protein expression was detected by  Western blotting analysis.  The results showed that the IC₅₀ value of LDM and TRAIL for H460 cells was 4.603×10⁻¹⁰ mol·L⁻¹ and 915.3 ng·mL⁻¹ respectively, but the IC₅₀ value of LDM was 3.064×10⁻¹¹ mol·L⁻¹ and 1.611×10⁻¹¹ mol·L⁻¹ when different concentrations of LDM was combined with 50 and 100 ng·mL⁻¹ TRAIL   respectively.  And the CDI value was less than 1.  The apoptosis ratios also increased in the combination group relative to the single-agent treatment and the untreated control.  Furthermore, the induction of the cleavage of PARP and the activation of Caspase-3 and Caspase-8 by the combination were more effective than LDM or TRAIL alone.  At last, the level of death receptor 5 (DR5) expressions increased in a dose-dependent manner and time-related pattern.  The data indicate that LDM inhibits the growth of H460 cells in vitro.  DR5 induction contributes to enhancement of TRAIL-induced apoptosis by LDM in human non-small lung cancer cells.