The role of apoptotic cell death in the radiosensitising effect of gemcitabine.
BACKGROUND
The aim of this study was to evaluate the radiosensitising effect of gemcitabine, in terms of cell-cycle progression, induction of apoptosis, and to investigate the molecular events regulating apoptosis.


METHODS
Tumour cells were treated with gemcitabine, radiation, or the combination. 0-72 h after treatment, cells were collected for cell-cycle analysis and apoptosis determination. Caspase 8 and 9, Bid and tBid expression were determined by western blot. The mitochondrial membrane potential was determined using flow cytometry. An RT(2) Profiler PCR Array for human apoptotic genes was performed after the combination or TRAIL treatment.


RESULTS
Gemcitabine and radiation resulted in an early S-phase block immediately after treatment, after which the cells moved synchronously through the cell cycle. When cell-cycle distribution returned to pre-treatment levels, an increased induction of apoptosis was observed with activation of caspase 8 and 9 and a reduction of the mitochondrial membrane potential. Gene expression after treatment with radiosensitising conditions was comparable with expression after the TRAIL treatment.


CONCLUSIONS
A role for the cell-cycle perturbations and the induction of apoptosis could be attributed to the radiosensitising effect of gemcitabine. Apoptosis induction was comparable with the apoptotic pathway observed after the TRAIL treatment, that is the involvement of the extrinsic apoptosis pathway.
Pauwels
B
B
Laboratory of Cancer Research and Clinical Oncology, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium. bea.pauwels@ua.ac.be
Vermorken
J B
JB
Wouters
A
A
Ides
J
J
Van Laere
S
S
Lambrechts
H A J
HA
Pattyn
G G O
GG
Vermeulen
K
K
Meijnders
P
P
Lardon
F
F
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D051023:BH3 Interacting Domain Death Agonist Protein / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D015153:Blotting, Western; D053181:Caspase 8 / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D053453:Caspase 9 / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D045744:Cell Line, Tumor; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D005434:Flow Cytometry; D006801:Humans; D020287:In Situ Nick-End Labeling; D053078:Membrane Potential, Mitochondrial; D016133:Polymerase Chain Reaction; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D000093542:Gemcitabine
D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D011838:Radiation-Sensitizing Agents; D003841:Deoxycytidine; D053181:Caspase 8; D053453:Caspase 9; D000093542:Gemcitabine