BRAF inhibitors suppress apoptosis through off-target inhibition of JNK signaling
Menée à l'aide de modèles murins de mélanome, cette étude met en évidence un mécanisme par lequel le vémurafenib supprime l'apoptose, ce qui permet de rendre compte du développement d'un carcinome épidermoïde cutané chez une proportion significative de patients traités à l'aide de vémurafenib
Vemurafenib and dabrafenib selectively inhibit the v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) kinase, resulting in high response rates and increased survival in melanoma. Approximately 22% of individuals treated with vemurafenib develop cutaneous squamous cell carcinoma (cSCC) during therapy. The prevailing explanation for this is drug-induced paradoxical ERK activation, resulting in hyperproliferation. Here we show an unexpected and novel effect of vemurafenib/PLX4720 in suppressing apoptosis through the inhibition of multiple off-target kinases upstream of c-Jun N-terminal kinase (JNK), principally ZAK. JNK signaling is suppressed in multiple contexts, including in cSCC of vemurafenib-treated patients, as well as in mice. Expression of a mutant ZAK that cannot be inhibited reverses the suppression of JNK activation and apoptosis. Our results implicate suppression of JNK-dependent apoptosis as a significant, independent mechanism that cooperates with paradoxical ERK activation to induce cSCC, suggesting broad implications for understanding toxicities associated with BRAF inhibitors and for their use in combination therapies. - See more at: http://elife.elifesciences.org/content/2/e00969?rss=1#sthash.OzHYorrr.dpuf