Molecular requirements for the combined effects of TRAIL and ionising radiation.
OBJECTIVE
Previously it was shown that combination of death ligand TRAIL and irradiation strongly increases cell kill in several human tumour cell lines. Since Bcl-2 overexpression did not strongly interfere with the efficacy, components of the mitochondrial death pathway are not required for an effective combined treatment. In the present study the minimal molecular prerequisites for the efficacy of a combined treatment were determined.


METHODS
Apoptosis induction in control, caspase-8 and FADD negative Jurkat cells, BJAB control and FADD-DN cells was analysed by FACS. Activation of caspase-8, -10 and -3 and cleavage of PARP was determined by immunoblotting. TRAIL receptors were activated using recombinant human TRAIL. Surface expression of TRAIL receptors DR4 and DR5 was analysed by FACS.


RESULTS
Jurkat T-cells express the agonistic DR5 receptor but not DR4. Presence of FADD was found to be essential for TRAIL induced apoptosis. Caspase-8 negative cells show very low rates of apoptosis after prolonged stimulation with TRAIL. No combined effects of TRAIL with irradiation could be found in FADD-DN overexpressing and FADD deficient cells. However, the combination of TRAIL and irradiation clearly lead to a combined effect in caspase-8 negative Jurkat cells, albeit with reduced death rates. In these cells activation of the alternative initiator caspase-10 could be detected after combined treatment.


CONCLUSIONS
Our data show that a combined therapy with TRAIL and irradiation will only be effective in cells expressing at least one agonistic TRAIL receptor, FADD and caspase-8 or caspase-10.
Marini
Patrizia
P
Department of Radiation Oncology, University of Tübingen, Tübingen, Germany.
Jendrossek
Verena
V
Durand
Elise
E
Gruber
Charlotte
C
Budach
Wilfried
W
Belka
Claus
C
D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects*; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000378:metabolism; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D019169:Jurkat Cells; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D008562:Membrane Glycoproteins; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505639:TNFRSF10B protein, human; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases