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Function-blocking ERBB3 antibody inhibits the adaptive response to RAF inhibitor.

ABSTRACT: ERBB3/HER3 expression and signaling are upregulated in mutant BRAF melanoma as an adaptive, prosurvival response to FDA-approved RAF inhibitors. Because compensatory ERBB3 signaling counteracts the effects of RAF inhibitors, cotargeting ERBB3 may increase the efficacy of RAF inhibitors in mutant BRAF models of melanoma. Here, we corroborate this concept by showing that the ERBB3 function-blocking monoclonal antibody huHER3-8 can inhibit neuregulin-1 activation of ERBB3 and downstream signaling in RAF-inhibited melanoma cells. Targeting mutant BRAF in combination with huHER3-8 decreased cell proliferation and increased cell death in vitro, and decreased tumor burden in vivo, compared with targeting either mutant BRAF or ERBB3 alone. Furthermore, the likelihood of a durable tumor response in vivo was increased when huHER3-8 was combined with RAF inhibitor PLX4720. Together, these results offer a preclinical proof of concept for the application of ERBB3-neutralizing antibodies to enhance the efficacy of RAF inhibitors in melanoma to delay or prevent tumor regrowth. As ERBB3 is often upregulated in response to other kinase-targeted therapeutics, these findings may have implications for other cancers as well.

SUBMITTER: Kugel CH

PROVIDER: S-EPMC4120074 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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Function-blocking ERBB3 antibody inhibits the adaptive response to RAF inhibitor.

Kugel Curtis H CH Hartsough Edward J EJ Davies Michael A MA Setiady Yulius Y YY Aplin Andrew E AE

Cancer research 20140717 15

ERBB3/HER3 expression and signaling are upregulated in mutant BRAF melanoma as an adaptive, prosurvival response to FDA-approved RAF inhibitors. Because compensatory ERBB3 signaling counteracts the effects of RAF inhibitors, cotargeting ERBB3 may increase the efficacy of RAF inhibitors in mutant BRAF models of melanoma. Here, we corroborate this concept by showing that the ERBB3 function-blocking monoclonal antibody huHER3-8 can inhibit neuregulin-1 activation of ERBB3 and downstream signaling i ...[more]

PMID: 25035390

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Project description:BackgroundTreatment of advanced melanoma has been improved with the advent of the BRAF inhibitors. However, a limitation to such treatment is the occurrence of resistance. Several mechanisms have been identified to be responsible for the development of resistance, either MEK-dependent or MEK-independent. In order to overcome resistance due to reactivation of MEK signaling, MEK inhibitors are being clinically developed with promising results. However, also in this case resistance inevitably occurs. It has been recently reported that ErbB3, a member of the EGFR receptor family, may be involved in the establishment of drug resistance.MethodsThree melanoma cell lines were tested: LOX IMVI (BRAF V600E), MST-L (BRAF V600R) and WM266 (BRAF V600D). Phosphorylation of Receptor Tyrosine Kinases (RTKs) was assessed by an RTK array. Western blot analysis was performed on total protein extracts using anti-ErbB3, anti-AKT and anti-ERK 1/2 antibodies. The expression of neuregulin after vemurafenib treatment was assessed by Real Time PCR and Western blotting. The growth inhibitory effects of vemurafenib, GSK1120212b and/or anti-ErbB3 mAbs were evaluated by in vitro colony formation assays.ResultsIn the present study we demonstrate that ErbB3 is the main RTK undergoing rapidly hyperphosphorylation upon either treatment with a BRAF inhibitor or with a MEK inhibitor in a panel of melanoma cell lines harboring a variety of V600BRAF mutations and that this results in a strong activation of phospho-AKT. Importantly, ErbB3 activation is fully abrogated by the simultaneous use of anti-ErbB3 monoclonal antibodies, which are also shown to potently synergize with BRAF inhibitors in the inactivation of both AKT and ERK pathways and in the inhibition of melanoma cell growth. We show that upregulation of phospho-ErbB3 is due to an autocrine loop involving increased transcription and production of neuregulin by melanoma cells.ConclusionsOn the basis of these results, we propose that initial co-treatment with BRAF and/or MEK inhibitors and anti-ErbB3 antibodies should be pursued as a strategy to reduce the ErbB3-dependent feedback survival mechanism and enhance duration of clinical response.

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Function-blocking ERBB3 antibody inhibits the adaptive response to RAF inhibitor.

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Function-blocking ERBB3 antibody inhibits the adaptive response to RAF inhibitor.

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