Resistance of human melanoma cells against the death ligand TRAIL is reversed by ultraviolet-B radiation via downregulation of FLIP
Abstract
Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) is a potential anticancer drug since it induces apoptosis preferentially in malignant but not in normal cells. Not all cancer cells, however, are TRAIL susceptible. Chemotherapeutic drugs and ionizing radiation have been found to be able to sensitize resistant tumor cells for TRAIL-induced apoptosis. Since ultraviolet B radiation (UVB) is a potent inducer of apoptosis but exhibits much less adverse effects, we studied whether UVB sensitizes TRAIL-resistant melanoma cells. Therefore, we analyzed the TRAIL-sensitive human cell line A-375 in comparison to the resistant cell line IGR-37. Both cell lines showed expression of the long form of the antiapoptotic FLICE inhibitory protein FLIP(L) which, however, was partially cleaved into the 43 kDa form in A-375 cells. In addition, only IGR-37 cells expressed the short splicing variant FLIP(S), which exerts high antiapoptotic activity. Accordingly, transient overexpression of FLIP(S) rendered A-375 cells resistant to TRAIL. Upon exposure to low UVB doses, TRAIL-treated IGR-37 cells underwent pronounced apoptosis and TRAIL sensitivity of A-375 cells was dramatically increased. In both cases, UVB caused an inhibition of flip ...Continue Reading
References
Chemotherapeutic agents augment TRAIL-induced apoptosis in human hepatocellular carcinoma cell lines
Sensitization of resistant lymphoma cells to irradiation-induced apoptosis by the death ligand TRAIL
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