Interferon-α induces sensitization of cells to inhibition of protein synthesis by tumour necrosis factor-related apoptosis-inducing ligand

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Tumour cells are often sensitized by interferons to the effects of tumour necrosis factor-α-related apoptosis-inducing ligand (TRAIL). We have demonstrated previously that TRAIL has an inhibitory effect on protein synthesis [Jeffrey IW, Bushell M, Tilleray VJ, Morley S & Clemens MJ (2002) Cancer Res62, 2272–2280] and we have therefore examined the consequences of prior interferon-α treatment for the sensitivity of translation to inhibition by TRAIL. Interferon treatment alone has only a minor effect on protein synthesis but it sensitizes both MCF-7 cells and HeLa cells to the downregulation of translation by TRAIL. The inhibition of translation is characterized by increased phosphorylation of the α subunit of eukaryotic initiation factor eIF2 and dephosphorylation of the eIF4E-binding protein 4E-BP1. Both of these effects, as well as the decrease in overall protein synthesis, require caspase-8 activity, although they precede overt apoptosis by several hours. Interferon-α enhances the level and/or the extent of activation of caspase-8 by TRAIL, thus providing a likely explanation for the sensitization of cells to the inhibition of translation.

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