Melanoma adapts to RAF/MEK inhibitors through FOXD3-mediated upregulation of ERBB3
Ethan V. Abel, … , Paolo Fortina, Andrew E. Aplin
Ethan V. Abel, … , Paolo Fortina, Andrew E. Aplin
Published April 1, 2013
Citation Information: J Clin Invest. 2013;123(5):2155-2168. https://doi.org/10.1172/JCI65780.
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Research Article Oncology

Melanoma adapts to RAF/MEK inhibitors through FOXD3-mediated upregulation of ERBB3

Abstract

The mechanisms underlying adaptive resistance of melanoma to targeted therapies remain unclear. By combining ChIP sequencing with microarray-based gene profiling, we determined that ERBB3 is upregulated by FOXD3, a transcription factor that promotes resistance to RAF inhibitors in melanoma. Enhanced ERBB3 signaling promoted resistance to RAF pathway inhibitors in cultured melanoma cell lines and in mouse xenograft models. ERBB3 signaling was dependent on ERBB2; targeting ERBB2 with lapatinib in combination with the RAF inhibitor PLX4720 reduced tumor burden and extended latency of tumor regrowth in vivo versus PLX4720 alone. These results suggest that enhanced ERBB3 signaling may serve as a mechanism of adaptive resistance to RAF and MEK inhibitors in melanoma and that cotargeting this pathway may enhance the clinical efficacy and extend the therapeutic duration of RAF inhibitors.

Authors

Ethan V. Abel, Kevin J. Basile, Curtis H. Kugel III, Agnieszka K. Witkiewicz, Kaitlyn Le, Ravi K. Amaravadi, Giorgos C. Karakousis, Xiaowei Xu, Wei Xu, Lynn M. Schuchter, Jason B. Lee, Adam Ertel, Paolo Fortina, Andrew E. Aplin

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Figure 6

NRG1β/ERBB3 signaling promotes resistance to RAF/MEK inhibitors.

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NRG1β/ERBB3 signaling promotes resistance to RAF/MEK inhibitors. (A) A37...
(A) A375 cells were plated at clonal density and treated with either DMSO, DMSO with NRG1β (10 ng/ml), PLX4032 (1 μM), PLX4032 with NRG1β, AZD6244 (3.3 μM), or AZD6244 with NRG1β. Medium and drugs were replenished every 3 days for 7 days, after which cells were fixed and stained with crystal violet. (B) Magnification of colonies in A (×40). (C) WM115, WM239A, and WM266-4 cells were treated with DMSO, PLX4032 (1 μM), or AZD6244 (3.3 μM) with or without NRG1β (10 ng/ml) for 72 hours, after which AlamarBlue was added to medium for 2 hours. Reduced AlamarBlue as analyzed by spectrophotometer to determine cell viability. DMSO-treated cell groups were set to 100% viable, and all other groups were normalized to these groups. Mean ± SEM (n = 4) and P values are shown. (D) 1205LuTR cells stably expressing Dox-inducible LacZ-targeting (LacZ 2.1) or 2 distinct ERBB3-targeting shRNAs were treated with or without Dox for 5 days, followed by treatment with PLX4032 (+) or DMSO (–) for 24 hours, and finally stimulated with 10 ng/ml NRG1β for 1 hour prior to lysis. Lysates were immunoblotted as indicated. (E) Mean fold change of tumor volume in 1205LuTR xenografts (n = 16 per condition) in nude mice fed either PLX4720 or vehicle-laced chow, expressing either LacZ-targeting or ERBB3-targeting shRNAs. Statistically significant comparisons of the LacZ-targeting and ERBB3-targeting shRNA xenografts are indicated by blue P values (LacZ vs. ERBB3 shRNA#10) or green P values (LacZ vs. ERBB3 shRNA#12).