Synergistic Rescue of Nonsense Mutant Tumor Suppressor p53 by Combination Treatment with Aminoglycosides and Mdm2 Inhibitors

Abstract

The tumor suppressor gene TP53 is inactivated by mutation in a large fraction of human tumors. Around 10% of TP53 mutations are nonsense mutations that lead to premature termination of translation and expression of truncated unstable and non-functional p53 protein. Aminoglycosides G418 (geneticin) and gentamicin have been shown to induce translational readthrough and expression of full-length p53. However, aminoglycosides have severe side effects that limit their clinical use. Here, we show that combination treatment with a proteasome inhibitor or compounds that disrupt p53-Mdm2 binding can synergistically enhance levels of full-length p53 upon aminoglycoside-induced readthrough of R213X nonsense mutant p53. Full-length p53 expressed upon combination treatment is functionally active as assessed by upregulation of p53 target genes, suppression of cell growth, and induction of cell death. Thus, our results demonstrate that combination treatment with aminoglycosides and compounds that inhibit p53 degradation is synergistic and can provide significantly improved efficacy of readthrough when compared with aminoglycosides alone. This may have implications for future cancer therapy based on reactivation of nonsense mutant TP53.

40 Years of Research Put p53 in Translation

“…While only few studies have been dedicated to understanding the role of p53-mediated translational regulation in the fine modulation of gene expression driven by p53, the relationship between p53 and translation has been largely reviewed to illustrate different facets of p53 biology since: (i) an increase in p53 mRNA translation contributes to p53 activation in response to stress [ 23 ]; (ii) alteration of ribosome biogenesis corresponds to one of the stresses able to activate a p53-dependent response (i.e., nucleolar or ribosomal stress) [ 24 , 25 ]; (iii) usage of alternative translation start sites allow expression of different p53 isoforms modulating p53 transcriptional activity [ 23 , 26 , 27 ]; and (iv) antibiotics targeting the translational machinery could restore wild-type p53 transcriptional activity from nonsense p53 mutant [ 28 , 29 , 30 ]. In a previous review, we discussed how translation contributes to tumor suppressive of p53 [ 31 ].…”

Loss of p53 function at late stages of tumorigenesis confers ARF-dependent vulnerability to p53 reactivation therapy

“…Based on the results in the p53ER TAM model, it can be speculated that a p53 loss-of-function mutant might not be sufficiently stabilized if ARF is deleted, mutated, or irreversibly silenced and that Mdm2 inhibitors could serve as ARF mimics to boost the effect of mutant p53 reactivating drugs in this scenario. Consistent with this concept, it was shown that Mdm2 inhibitors synergistically enhance the activity of small-molecule stabilizers of conformationally unstable p53 mutants and readthrough-promoting drugs for p53 nonsense mutants (39, 40). For p53 reactivation to be therapeutically effective, it therefore does not seem to be critical whether p53 was inactivated at the onset of malignant transformation or at later stages, as long as strong oncogenic signals are present and transmitted via ARF to stabilize p53.…”

Resorting the function of the colorectal cancer gatekeeper adenomatous polyposis coli

“…There have been a number of previous clinical and translational studies that examined the applicability of the read‐through approach to a clinical setting . Though some of these studies focused on the cancer arena, none resulted in clinical trials . Therefore, the ability to induce read‐through of the APC full‐length protein by antibiotic treatment represents a new potential strategy to delay or even prevent cancer formation in FAP patients.…”

“…29 Though some of these studies focused on the cancer arena, none resulted in clinical trials. [30][31][32] Therefore, the ability to induce read-through of the APC fulllength protein by antibiotic treatment represents a new potential strategy to delay or even prevent cancer formation in FAP patients. Indeed, reports by our group have already demonstrated the efficacy of aminoglycosides and macrolide induced readthrough in a multiple intestinal neoplasm APC (Min/+) mouse model, 21 and of other macrolide compounds in vitro.…”