Murine double minute 2 as a therapeutic target for radiation sensitization of lung cancer

Abstract

Murine double minute 2 (MDM2) inhibits p53-mediated functions, which are essential for therapies using DNAdamaging agents. The purpose of this study was to determine whether MDM2 inhibition enhances the radiosensitivity of a lung cancer model. The effects of MDM2 inhibition on tumor vasculature were also studied. Transient transfection of H460 lung cancer cells and human umbilical vascular endothelial cells (HUVEC) with antisense oligonucleotides (ASODN) against MDM2 resulted in a reduced level of MDM2 and increased levels of p21 and p53. Clonogenic assays showed that inhibition of MDM2 greatly decreased cell survival following irradiation. Quantification of apoptotic cells by 7-aminoactinomycin D staining and of senescent cells by X-gal staining showed that both processes were significantly increased in H460 cells treated with MDM2-specific ASODN and radiation. H460 xenografts that were treated with MDM2 ASODN plus radiotherapy also showed significant growth delay (P < 0.001) and increased apoptosis by terminal deoxynucleotidyl transferase -mediated nick end labeling staining. HUVECs transfected with MDM2-specific ASODN showed impaired viability and migration with decreased tube formation. Doppler studies showed that tumor blood flow was compromised when H460 xenografts were treated with MDM2-specific ASODN and radiation. A combination of radiotherapy and inhibition of MDM2 through the antisense approach results in improved tumor control in the H460 lung cancer model. This implies that a similar strategy should be investigated among patients with locally advanced lung cancer, receiving thoracic radiotherapy. [Mol Cancer Ther 2005;4(8):1137 -45]

Radiosensitization of lung cancer by nutlin, an inhibitor of murine double minute 2

“…The present study is the first to look at the effects of nutlin on normal endothelial cells, which is p53 competent, and how nutlin 3a effects on vascular endothelium may be augmented by radiation. This is consistent with our study using antisense approach (42). MDM2 inhibition may have antiangiogenic effects because of its induction of p53 expression, which has been shown to induce the expression of angiogenesis inhibitors, such as thrombospondin-1, and to decrease the expression of vascular endothelial growth factor (43 -47).…”

Hypoxia-regulated p53 and its effect on radiosensitivity in cancer cells

“…The activity of Mdm2 to negatively regulate p53 suggests a role of Mdm2 in modifying the resistance of tumor cells to p53-mediated cell death induced by stimuli such as ionizing radiation and hyperthermia. Consistently, it has been reported that decreased levels of Mdm2 sensitize tumor cells to ionizing radiation (Perry 2004, Cao et al 2005.…”

Clinical Significance of the p53 Pathway and Associated Gene Therapy in Non-Small Cell Lung Cancers

“…However, an experimental study demonstrated that the inhibition of MDM2 using antisense oligonucleotides increased the expression of p53 and p21 and decreased the survival of lung cancer cells following irradiation [56]. This result suggested the possibility of MDM2 being a therapeutic target for radiation sensitization against lung cancer.…”