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PAK signalling drives acquired drug resistance to MAPK inhibitors in BRAF-mutant melanomas.


ABSTRACT: Targeted BRAF inhibition (BRAFi) and combined BRAF and MEK inhibition (BRAFi and MEKi) therapies have markedly improved the clinical outcomes of patients with metastatic melanoma. Unfortunately, the efficacy of these treatments is often countered by the acquisition of drug resistance. Here we investigated the molecular mechanisms that underlie acquired resistance to BRAFi and to the combined therapy. Consistent with previous studies, we show that resistance to BRAFi is mediated by ERK pathway reactivation. Resistance to the combined therapy, however, is mediated by mechanisms independent of reactivation of ERK in many resistant cell lines and clinical samples. p21-activated kinases (PAKs) become activated in cells with acquired drug resistance and have a pivotal role in mediating resistance. Our screening, using a reverse-phase protein array, revealed distinct mechanisms by which PAKs mediate resistance to BRAFi and the combined therapy. In BRAFi-resistant cells, PAKs phosphorylate CRAF and MEK to reactivate ERK. In cells that are resistant to the combined therapy, PAKs regulate JNK and ?-catenin phosphorylation and mTOR pathway activation, and inhibit apoptosis, thereby bypassing ERK. Together, our results provide insights into the molecular mechanisms underlying acquired drug resistance to current targeted therapies, and may help to direct novel drug development efforts to overcome acquired drug resistance.

SUBMITTER: Lu H 

PROVIDER: S-EPMC5891348 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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PAK signalling drives acquired drug resistance to MAPK inhibitors in BRAF-mutant melanomas.

Lu Hezhe H   Liu Shujing S   Zhang Gao G   Bin Wu   Zhu Yueyao Y   Frederick Dennie T DT   Hu Yi Y   Zhong Wenqun W   Randell Sergio S   Sadek Norah N   Zhang Wei W   Chen Gang G   Cheng Chaoran C   Zeng Jingwen J   Wu Lawrence W LW   Zhang Jie J   Liu Xiaoming X   Xu Wei W   Krepler Clemens C   Sproesser Katrin K   Xiao Min M   Miao Benchun B   Liu Jianglan J   Song Claire D CD   Liu Jephrey Y JY   Karakousis Giorgos C GC   Schuchter Lynn M LM   Lu Yiling Y   Mills Gordon G   Cong Yusheng Y   Chernoff Jonathan J   Guo Jun J   Boland Genevieve M GM   Sullivan Ryan J RJ   Wei Zhi Z   Field Jeffrey J   Amaravadi Ravi K RK   Flaherty Keith T KT   Herlyn Meenhard M   Xu Xiaowei X   Guo Wei W  

Nature 20170927 7674


Targeted BRAF inhibition (BRAFi) and combined BRAF and MEK inhibition (BRAFi and MEKi) therapies have markedly improved the clinical outcomes of patients with metastatic melanoma. Unfortunately, the efficacy of these treatments is often countered by the acquisition of drug resistance. Here we investigated the molecular mechanisms that underlie acquired resistance to BRAFi and to the combined therapy. Consistent with previous studies, we show that resistance to BRAFi is mediated by ERK pathway re  ...[more]

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