towards improved death receptor targeted therapy for ... - TI Pharma

Chapter 5
RESULTS
Synergistic activity of 17‐AAG and TRAIL in NSCLC cells
H460 and A549 cells were treated for 24 h with increasing concentrations of 17‐AAG. Both
cell lines showed similar sensitivities for this compound (Fig. 1A). The IC50 values of 17‐
AAG were not reached after 24 h incubation. Next, the effect of 17‐AAG on TRAIL
sensitivity was determined in TRAIL sensitive H460 cells and resistant A549 cells by using
MTT assays. TRAIL treatment alone for 24 h effectively killed H460 cells with an IC50 value
of 5.7 ng/ml, whereas A549 cells were resistant for TRAIL having an IC50 of more than 500
ng/ml (Fig. 1). Next, different concentrations of TRAIL and a fixed concentration of 100 nM
17‐AAG, representing the IC20, (Fig. 1A) were applied to the cells and the percentage of
growth inhibition was determined. The simultaneous administration of 17‐AAG and TRAIL
showed synergistic activity in A549 and H460 cells, with a CI of 0.28 ± 16 and 0.44 ± 0.23,
respectively (Fig. 1B and C).
Figure 1. The Hsp inhibitor 17‐AAG synergistically enhances cytotoxicity of TRAIL. (A) Dose‐response
curve of 17‐AAG in A549 and H460 cells. Cell growth was measured with the MTT assay. Growth
inhibition curves of A549 (B) and H460 (C) cells after 24 h exposure to increasing concentrations of
TRAIL alone or in combination with 100 nM 17‐AAG. The average CI values were calculated from
fraction affected (FA) data points above 0.5. CI’s below 0.9 indicate synergy, CIs between 0.9 and 1
indicates additive effects and higher CI values represent antagonism. The CI values ±SEM are
averages of three independent experiments.
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