Nicholas Beazley Long
Novel mechanisms of resistance to vemurafenib in melanoma – V600E B-Raf reversion and switching VEGF-A splice isoform expression
Beazley Long, Nicholas; Gaston, Kevin; Harper, Steven J.; Orlando, Antonio; Bates, David O.
Authors
Professor KEVIN GASTON Kevin.Gaston@nottingham.ac.uk
Professor of Cancer Studies
Steven J. Harper
Antonio Orlando
David O. Bates
Abstract
Targeting activating mutations in the proto-oncogene B-Raf, in melanoma, has led to increases in progression free survival. Treatment with vemurafenib, which inhibits the most common activating-mutated form of B-Raf (B-RafV600E), eventually results in resistance to therapy. VEGF-A is the principal driver of angiogenesis in primary and metastatic lesions. The bioactivity of VEGF-A is dependent upon alternative RNA splicing and pro-angiogenic isoforms of VEGF-A are upregulated in many disease states dependent upon angiogenesis, including cancers. Using techniques including RT-PCR, Western blotting, ELISA and luciferase reporter assays, the effect of vemurafenib on proliferation, ERK1/2 phosphorylation and the levels of pro- and anti-angiogenic VEGF-A isoforms was investigated in melanoma cell types expressing either wild-type B-Raf or B-RafV600E, including a primary melanoma culture derived from a highly vascularised and active nodule taken from a patient with a V600E mutant melanoma. The primary melanoma culture was characterised and found to have reverted to wild-type B-Raf. In B-RafV600E A375 cells ERK1/2 phosphorylation, pro-angiogenic VEGF-A mRNA, total VEGF-A protein expression and VEGF-A 3’UTR activity were all decreased in a concentration-dependent manner by vemurafenib. Conversely vemurafenib treatment of wild-type B-Raf cells significantly increased ERK1/2 phosphorylation, pro-angiogenic VEGF-A mRNA and total VEGF-A expression in a concentration-dependent manner. A switch to pro-angiogenic VEGF-A isoforms, with a concomitant upregulation of expression by increasing VEGF-A mRNA stability, may be an additional oncogenic and pathological mechanism in B-RafV600E melanomas, which promotes tumor-associated angiogenesis and melanoma-genesis. We have also identified the genetic reversal of B-RafV600E to wild-type in an active melanoma nodule taken from a V600E-positive patient and continued vemurafenib treatment for this patient is likely to have had a detrimental effect by promoting B-RafWT activity.
Citation
Beazley Long, N., Gaston, K., Harper, S. J., Orlando, A., & Bates, D. O. (2015). Novel mechanisms of resistance to vemurafenib in melanoma – V600E B-Raf reversion and switching VEGF-A splice isoform expression. American Journal of Cancer Research, 5(1), 433--441
Journal Article Type | Article |
---|---|
Acceptance Date | Nov 28, 2014 |
Online Publication Date | Dec 15, 2014 |
Publication Date | Jan 1, 2015 |
Deposit Date | Oct 30, 2018 |
Publicly Available Date | Oct 30, 2018 |
Journal | American Journal of Cancer Research |
Electronic ISSN | 2156-6976 |
Publisher | e-Century Publishing |
Peer Reviewed | Peer Reviewed |
Volume | 5 |
Issue | 1 |
Pages | 433--441 |
Keywords | Melanoma, vemurafenib, A375, 92.1, VEGF-A, VEGF-Axxxb, mechanism of resistance |
Public URL | https://nottingham-repository.worktribe.com/output/1037589 |
Publisher URL | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4300704/ |
Files
ajcr0005-0433
(1.1 Mb)
PDF
Publisher Licence URL
https://creativecommons.org/licenses/by-nc/4.0/
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