Article

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: 15.93). 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.

0 Bookmarks
 · 
190 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cancer genomic studies support the idea that a cell becomes cancerous through the progressive acquisition of mutations that together confer the cancer phenotype. These mutations that promote cancer are commonly referred to as “driver genes” (Stratton et al., 2009). It is not well understood how the presence of one mutation influences the selection of subsequent mutations through an evolutionary process (Yates and Campbell, 2012). A statistical lack of co-occurrence between “canonical” mutations within the same pathway is well established (Thomas et al., 2007 and Yates and Campbell, 2012). The lack of co-occurrence is typically attributed to the assumption that there would be no selective benefit to accumulating multiple mutations within the same molecular pathway (Yeang et al., 2008). Such arguments implicitly assume that each mutation is sufficiently strong to confer a selective advantage alone (e.g., the canonical KRAS and BRAF mutations). However, there are a number of weakly activating RAS and BRAF mutations that have been observed in cancer (Wan et al., 2004), although less commonly than the canonical mutations.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Melanoma is the deadliest form of skin cancer and has an incidence that is rising faster than any other solid tumor. Metastatic melanoma treatment has considerably progressed in the past five years with the introduction of targeted therapy (BRAF and MEK inhibitors) and immune checkpoint blockade (anti-CTLA4, anti-PD-1, and anti-PD-L1). However, each treatment modality has limitations. Treatment with targeted therapy has been associated with a high response rate, but with short-term responses. Conversely, treatment with immune checkpoint blockade has a lower response rate, but with long-term responses. Targeted therapy affects antitumor immunity, and synergy may exist when targeted therapy is combined with immunotherapy. This article presents a brief review of the rationale and evidence for the potential synergy between targeted therapy and immune checkpoint blockade. Challenges and directions for future studies are also proposed.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Functional genomics attempts to understand the genome by perturbing the flow of information from DNA to RNA to protein in order to learn how gene dysfunction leads to disease. CRISPR/Cas9 technology represents the newest tool in the geneticist's toolbox, both allowing researchers to edit DNA with unprecedented ease, speed, and accuracy, and representing a novel means to conduct genome-wide genetic screens to discover gene function. In this review we first briefly summarize the discovery and characterization of CRISPR/Cas9, and then compare it to other genome engineering technologies. We discuss its initial use in screening applications with a focus on optimizing on-target activity and minimizing off-target effects. Finally, we comment on future challenges and opportunities with this technology. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    FEBS Journal 02/2015; DOI:10.1111/febs.13248 · 3.99 Impact Factor

Full-text

Download
72 Downloads
Available from
Jun 1, 2014