A new approach against cancer: translational readthrough inducing drugs rescuing nonsense mutated TP53

Stop mutations (nonsense) are gene mutations characterized by the substitution of a single nucleotide in the coding sequence of a gene, which causes the onset of a premature stop codon (PTC) within the reading frame of the mRNA, resulting in the formation of a truncated and non-functional protein. Stop mutations are the cause of approximately 11% of genetic diseases (Cystic Fibrosis and Duchenne Muscular Dystrophy) [1] and can also be present in the coding sequence of tumor suppressor genes such as TP53; in fact, 10% of TP53 mutations are stop mutations [2]. The TP53 gene encodes the transcriptional factor p53, which regulates numerous pathways such as cell cycle arrest and DNA damage repair when cells are under certain stress conditions [3]. Mutations of TP53 can lead to the formation of tumors; in fact, it is the most frequently mutated gene in human tumors [4]. Today there is no therapy for the pathologies caused by this type of mutation, but an approach that has proven to be particularly effective is represented by molecules with readthrough activity (TRIDs; Translational Readthrough Inducing Drugs) which intervene on the ribosome allowing the overcoming of the PTC and the restoration of the synthesis and subsequent functionality of the protein [5]. This work evaluated the readthrough potential of these molecules and the recovery of p53 expression, following the induction of DNA damage on cells presenting the PTC UGA in the TP53 cDNA. The cellular localization of p53 was evaluated by immunofluorescence assay, the transcript of p53 and two of its target genes, p21, and GADD45, by Real-Time RT PCR, and the protein levels of p53 by Western blot. Treatment with TRIDs involves a partial localization of p53 in the nucleus following the induction of damage and the recovery of its expression in cells presenting the stop mutation and treated with the molecules. Through these results, we can, therefore, conclude that the molecules have a readthrough potential that allows the recovery of p53 expression and its correct localization at the nuclear level.