p53 Reactivation by PRIMA-1Met (APR-246) sensitises V600E/KBRAF melanoma to vemurafenib

• Published in: European journal of cancer (1990) 2016-03, Vol.55, p.98-110
• Main Authors: Krayem, Mohammad, Journe, Fabrice, Wiedig, Murielle, Morandini, Renato, Najem, Ahmad, Salès, François, van Kempen, Leon C., Sibille, Catherine, Awada, Ahmad, Marine, Jean-Christophe, Ghanem, Ghanem
• Format: Article
• Language: English
• Subjects: Drug resistance; Melanoma; p53; PRIMA-1Met; V600E/KBRAF; Vemurafenib
• ISSN: 0959-8049; 1879-0852
• DOI: 10.1016/j.ejca.2015.12.002

Intrinsic and acquired resistance of metastatic melanoma to V600E/KBRAF and/or MEK inhibitors, which is often caused by activation of the PI3K/AKT survival pathway, represents a major clinical challenge. Given that p53 is capable of antagonising PI3K/AKT activation we hypothesised that pharmacological restoration of p53 activity may increase the sensitivity of BRAF-mutant melanoma to MAPK-targeted therapy and eventually delay and/or prevent acquisition of drug resistance. To test this possibility we exposed a panel of vemurafenib-sensitive and resistant (innate and acquired) V600E/KBRAF melanomas to a V600E/KBRAF inhibitor (vemurafenib) alone or in combination with a direct p53 activator (PRIMA-1Met/APR-246). Strikingly, PRIMA-1Met synergised with vemurafenib to induce apoptosis and suppress proliferation of V600E/KBRAF melanoma cells in vitro and to inhibit tumour growth in vivo. Importantly, this drug combination decreased the viability of both vemurafenib-sensitive and resistant melanoma cells irrespectively of the TP53 status. Notably, p53 reactivation was invariably accompanied by PI3K/AKT pathway inhibition, the activity of which was found as a dominant resistance mechanism to BRAF inhibition in our lines. From all various combinatorial modalities tested, targeting the MAPK and PI3K signalling pathways through p53 reactivation or not, the PRIMA-1Met/vemurafenib combination was the most cytotoxic. We conclude that PRIMA-1Met through its ability to directly reactivate p53 regardless of the mechanism causing its deactivation, and thereby dampen PI3K signalling, sensitises V600E/KBRAF-positive melanoma to BRAF inhibitors. •This study evaluates and proposes an original drug combination not yet explored to break resistance to MAPK inhibitors in melanoma. Indeed, p53 is largely inactivated in melanoma and up-to-now very few studies are dedicated to reactivate this key pathway along with MAPK inhibition. Actually, one has been proposed and made its way to the clinic exploiting MDM2 inhibition (negative regulator of p53) with Nutlin-3.•In the present work, we evaluated a direct p53 activator, PRIMA-1Met that is able to act whatever the mechanism of p53 deactivation, including TP53 mutations in combination with a clinically effective oncogenic BRAF inhibitor vemurafenib and showed very significant synergies both on intrinsic (innate) and acquired resistance to mutBRAF inhibitors. We also described an additional mechanism by which p53 can moderated the activati