Nutlin-3

Nutlin-3 potently inhibits the MDM2-p53 interaction, leading to the activation of the p53 pathway. Nutlin-3 treatment induces the expression of MDM2 and p21, and displays potent antiproliferative activity with IC50 of ~1.5 μM, only in cells with wild-type p53 such as HCT116, RKO and SJSA-1, but not in the mutant p53 cell lines SW480 and MDA-MB-435. In SJSA-1 cells, Nutlin-3 treatment at 10 μM for 48 hours significantly induces caspase-dependent cell apoptosis by ~45%. Although Nutlin-3 also inhibits the growth and viability of human skin (1043SK) and mouse embryo (NIH/3T3) with IC50 of 2.2 μM and 1.3 μM, respectively, cells remain viable 1 week post-treatment even at 10 μM of Nutlin-3, in contrast with the SJSA-1 cells with viability lost at 3 μM of Nutlin-3 treatment. ^[1] Nutlin-3 does not induce the phosphorylation of p53 on key serine residues and reveals no difference in their sequence-specific DNA binding and ability to transactivate p53 target genes compared with phosphorylated p53 induced by the genotoxic drugs doxorubicin, demonstrating that phosphorylation of p53 on key serines is dispensable for transcriptional activation and apoptosis. ^[2] Although binding less efficiently to MDMX than to MDM2, Nutlin-3 can block the MDMX–p53 interaction and induce the p53 pathway in retinoblastoma cells (Weri1) with IC50 of 0.7 μM. ^[3] Nutlin-3 at 30 μM also disrupts endogenous p73-HDM2 interaction and enhances the stability and proapoptotic activities of p73, leading to the dose-dependent cell growth inhibition and apoptosis induction in cells without wild-type p53. ^[4]

Oral administration of Nutlin-3 at 200 mg/kg twice daily for 3 weeks significantly inhibits the tumor growth of SJAS-1 xenografts by 90%, comparable with the effect of doxorubicin treatment with 81% inhibition of tumor growth. ^[1]

• Biacore study

  Competition assay is performed on a Biacore S51. A Series S Sensor chip CM5 is utilized for the immobilization of a PentaHis antibody for capture of the His-tagged p53. The level of capture is ~200 response units (1 response unit corresponds to 1 pg of protein per mm²). The concentration of MDM2 protein is kept constant at 300 nM. Nutlin-3 is dissolved in DMSO at 10 mM and further diluted to make a concentration series of Nutlin-3 in each MDM2 test sample. The assay is run at 25 °C in running buffer (10 mM Hepes, 0.15 M NaCl, 2% DMSO). MDM2-p53 binding in the presence of Nutlin-3 is calculated as a percentage of binding in the absence of Nutlin-3 and IC50 is calculate

• Cell lines

  HCT116, RKO, SJSA-1, SW480, and MDA-MB-435

• Concentrations

  Dissolved in DMSO, final concentrations ~ 30 μM

• Incubation Time

  8, 24, and 48 hours

• Method

  Cells are exposed to various concentrations of Nutlin-3 for 8, 24 and 48 hours. The transcriptional levels of p21 and MDM2 genes are analyzed by real-time PCR, and protein levels by western blotting. Cell viability is measured by the MTT assay. Cell apoptosis is determined by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) staining with flow cytometry and fluorescence microscopy.

• Animal Models

  Athymic female nude mice (Nu/Nu-nuBR) injected subcutaneously with SJSA-1 cells

• Dosages

  200 mg/kg

• Administration

  Orally, twice a day