The
Wilms' tumor 1 (WT1) gene is overexpressed in human
glioblastoma and correlates with wild-type p53 status. In other cell types, WT1 inhibits p53-mediated apoptosis in response to
DNA damaging agents. However, neither this interaction nor the relationship between WT1 and radiosensitivity has been studied in
glioblastoma. To study this interaction, we generated LN-229
glioma cell lines (p53 mutant) stably expressing WT1
isoforms and induced apoptosis by transfecting with different doses of wild-type p53 plasmid expression vector. Constitutive expression of WT1 did not protect against exogenous p53-mediated apoptosis. Likewise, WT1 expression did not protect against endogenous p53-mediated cell death induced by
radiotherapy in U87MG cells, which contain functional wild-type p53. We then tested the efficacy of WT1
siRNA in inhibiting WT1 expression and its effect on radiosensitivity. In T98G and LN-18
glioma cells, which possess p53 mutations, WT1
siRNA decreased
WT1 protein to almost undetectable levels by 96-h post-transfection. Furthermore, WT1
siRNA transfection caused a significantly larger decrease in viability following irradiation than was seen in untransfected cells in both cell lines
after treatment with ED50 of ionizing radiation. In conclusion, WT1 overexpression did not protect against p53-mediated apoptosis or ionizing radiation induced cell death. WT1
siRNA increased the radiosensitivity of two human
glioma cell lines independently of p53. Anti-WT1 strategies may, therefore, prove useful in improving the response of
glioblastoma to
radiotherapy, thus potentially improving patient survival.