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 5

Increased ERBB3 phosphorylation following RAF inhibitor treatment in vivo.

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Increased ERBB3 phosphorylation following RAF inhibitor treatment in viv...
(A) A375 xenografts taken from animals fed vehicle (n = 5) or PLX4720-laced chow (n = 4) for 5 days analyzed by IHC for phospho-ERBB3 (Y1289). Representative images are shown. Original magnification, ×20. The graph shows quantitation of phospho-ERBB3 intensity. Cells were scored by intensity of membrane-associated staining from 0 (no staining) to 3 (strong staining). *P = 0.016. (B) Biopsies from patient taken prior to vemurafenib treatment, on-treatment, or upon disease progression were stained for phospho-ERBB3. Representative images are shown from patient 1 (Pt_1). The graph shows quantitation of cellular staining. Tumor cells in each slide were scored in a blinded manner, and statistical differences among the 3 conditions were analyzed using the cumulative link model (i.e., proportional odds model). The level of phospho-ERBB3 in the on-treatment and progression samples is statistically different from the pretreatment sample (*P < 0.001). The on-treatment biopsies for patient 1 and melanoma patient_503 (MP_503) were taken after 15 days and 16 months, respectively. Original magnification, ×200. (C) ERBB3 phosphorylation was analyzed by immunohistochemical staining of paired pretreatment and progression samples. MP_20 and MP_6 progressed after 6 and 9 months, respectively, on RAF/MEK inhibitor. MP_47 progressed on RAF inhibitor after 7.5 months. Representative images are shown for MP_6. Graphs show quantitation of phospho-ERBB3 intensity staining on scale of 0–3. *P < 0.001. Original magnification, ×200. (D) Statistical analysis across samples from all 9 patients that displayed staining for phospho-ERBB3. Analysis was performed using an ordered logistic regression model with random intercept for each patient.