U. Grunbaum et al., Transfection with mdm2-antisense or wtp53 results in radio sensitization and an increased apoptosis of a soft tissue sarcoma cell line, ANTICANC R, 21(3B), 2001, pp. 2065-2071
Soft tissue,sarcomas (STS) are mostly resistant after radiation treatment a
nd are characterized by a rather low rate of apoptosis. The aim of this stu
dy was to test, in the p53 mutant STS cell line US8-93, the effect of a com
bined treatment with DNA transfection - either with mdm2 antisense oligodes
oxynucleotides (mdm2 AS) or with a wild-type p53 plasmid (wtp53) - and the
effects of irradiation on radiosensitivity. Mdm2-sense oligodesoxynucleotid
es (mdm2-SE) and a GFP-plasmid (GFP) were applied as controls. In order to
evaluate the treatment radiation sensitization (clonogenic survival), apopt
otic cell death and P53/MDM2 protein expression were determined. A moderate
ly increased radiation sensitization was observed when comparing clonogenic
survival after 2 Gy irradiation between cells transfected either with the
control mdm2-SE (48%) or with mdm-2AS-(30%). At the same irradiation dose,
clonogenic survival of wtp53 plasmid transfected cells (32%) was about 2-fo
ld less than in the cells transfected with the control GFP plasmid (61%). T
his enhancement factor of radiation sensitization was increased by about 3-
fold at 4 Gy irradiation. Furthermore, an increase in apoptotic cells was a
lready detectable by up to 7.7% (mdm2 AS) in comparison to 3.1% (mdm2-SE co
ntrol) 72 hours after transfection. In parallel, the percentage of apoptoti
c cells could be further elevated after subsequent irradiation with 12 Gy b
y up to 15% (mdm2-AS) compared to 5.7% (mdm2-SE control). A striking result
was obtained with the combined treatment of a wtp53 and 12 Gy irradiation
which produced in 25% and 38.9 % of apoptotic cells 48 hours and 72 hours a
fter transfection, respectively. We can therefore conclude that the sensiti
vity of radiation therapy is enhanced by DNA transfection with wtp53 or mdm
-2 AS ODNs for the correction of the p53-mdm2 balance in STS in vitro.