We have studied aminoglycosides antibiotics known to induce readthrough of nonsense mutations. We have confirmed results from others showing that they can induce full length active p53 protein, leading to upregulation of p53 target genes and induction of tumor cell death. Moreover, we have demonstrated that the Mdm2 inhibitor Nutlin3a synergizes with G418 in inducing tumor cell death. This suggests that combination treatment with Mdm2 inhibitors could allow lower doses of aminoglycosides and therefore reduced toxicity. However, since aminoglycosides have severe side effects that make them less attractive for clinical use as anti-cancer agents, we have focused on the identification and characterization of novel molecules with higher potency and lower toxicity.
We have screened chemical libraries and analyzed available data in a major database to identify novel molecules that can induce efficient translational readthrough of nonsense mutant TP53 including R213X, the most common nonsense mutation in TP53 in human tumors. We have identified several candidate molecules and have characterized these further with the aim of in vivo studies in mice to confirm readthrough and anti-tumor effect. One compound has also shown potent activity on nonsense mutant PTEN. Furthermore, we have found that the chemotherapeutic drug 5-fluorouracil (5-FU) can induce readthrough of nonsense mutant TP53 via one of its metabolites. This produces full-length p53 that retains wild type activity as transcription factor as assessed by upregulation of p53 target genes and induction of tumor cell death. In addition, we have generated a new mouse model with a Trp53 R210X nonsense mutant knock-in allele (mouse R210X corresponds to human R213X) that will allow further in vivo studies with selected compounds. Since 5-FU is used for treatment of colon cancer and other types of cancer, our results may have important clinical implications.
