A Genome-Scale RNA Interference Screen Implicates NF1 Loss in Resistance to RAF Inhibition

1Cancer Program, The Broad Institute of Harvard and MIT.
Cancer Discovery (Impact Factor: 19.45). 01/2013; 3(3). DOI: 10.1158/2159-8290.CD-12-0470
Source: PubMed

ABSTRACT RAF inhibitors such as vemurafenib and dabrafenib block B-RAF-mediated cell proliferation and achieve meaningful clinical benefit in the vast majority of patients with B-RAFV600E-mutant melanoma. However, some patients do not respond to this regimen, and nearly all progress to therapeutic resistance. We employed a pooled RNA interference screen targeting >16,500 genes to discover loss of function events that could drive resistance to RAF inhibition. The highest-ranking gene was NF1, which encodes neurofibromin, a tumor suppressor that inhibits RAS activity. NF1 loss mediates resistance to RAF and MEK inhibitors through sustained MAPK pathway activation. However, cells lacking NF1 retained sensitivity to the irreversible RAF inhibitor AZ628 and an ERK inhibitor. NF1 mutations were observed in B-RAF-mutant tumor cells that are intrinsically resistant to RAF inhibition and in melanoma tumors obtained from patients exhibiting resistance to vemurafenib, thus demonstrating the clinical potential for NF1-driven resistance to RAF/MEK-targeted therapies.

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Available from: Dirk Schadendorf, Aug 17, 2015
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    • "To rule out that some of the known offtarget effects of RAF265 (Su et al., 2012) could contribute to explain its synergy with MEK inhibition, we repeated the cell proliferation assays with AZ628. This compound has been previously reported to be more selective for wild-type RAF kinases and has been widely used for in vitro studies (Montagut et al., 2008; Whittaker et al., 2013). The results obtained with AZ628 in combination with selumetinib are consistent with the observations made with RAF265 (Figure S4A). "
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