Abstract
BackgroundThe determination of NRAS and BRAF mutation status is a major requirement in the treatment of patients with metastatic melanoma. Mutation specific antibodies against NRASQ61R and BRAFV600E proteins could offer additional data on tumor heterogeneity. The specificity and sensitivity of NRASQ61R immunohistochemistry have recently been reported excellent. We aimed to determine the utility of immunohistochemistry using SP174 anti-NRASQ61R and VE1 anti-BRAFV600E antibodies in the theranostic mutation screening of melanomas.Methods142 formalin-fixed paraffin-embedded melanoma samples from 79 patients were analyzed using pyrosequencing and immunohistochemistry.Results23 and 26 patients were concluded to have a NRAS-mutated or a BRAF-mutated melanoma respectively. The 23 NRASQ61R and 23 BRAFV600E-mutant samples with pyrosequencing were all positive in immunohistochemistry with SP174 antibody and VE1 antibody respectively, without any false negative. Proportions and intensities of staining were varied. Other NRASQ61L, NRASQ61K, BRAFV600K and BRAFV600R mutants were negative in immunohistochemistry. 6 single cases were immunostained but identified as wild-type using pyrosequencing (1 with SP174 and 5 with VE1). 4/38 patients with multiple samples presented molecular discordant data. Technical limitations are discussed to explain those discrepancies. Anyway we could not rule out real tumor heterogeneity.ConclusionsIn our study, we showed that combining immunohistochemistry analysis targeting NRASQ61R and BRAFV600E proteins with molecular analysis was a reliable theranostic tool to face challenging samples of melanoma.Electronic supplementary materialThe online version of this article (doi:10.1186/s13000-015-0359-0) contains supplementary material, which is available to authorized users.
Highlights
The determination of NRAS and BRAF mutation status is a major requirement in the treatment of patients with metastatic melanoma
As BRAF inhibition became the reference treatment of BRAFV600-mutant metastatic melanomas, screening for BRAFV600 mutations was a major requirement for an optimal treatment with targeted therapies [44]
We evaluated the combination of novel NRASQ61R and BRAFV600E immunohistochemistry as well as pyrosequencing for mutation status profiling
Summary
The determination of NRAS and BRAF mutation status is a major requirement in the treatment of patients with metastatic melanoma. Mutation specific antibodies against NRASQ61R and BRAFV600E proteins could offer additional data on tumor heterogeneity. We aimed to determine the utility of immunohistochemistry using SP174 anti-NRASQ61R and VE1 anti-BRAFV600E antibodies in the theranostic mutation screening of melanomas. The mitogen-activated protein kinase (MAPK) pathway represents a major signaling cascade driving cell proliferation, differentiation and. The vast majority of these serine/threonine protein-kinase mutations are characterized by the substitution of valine at amino acid position 600, referred to as BRAFV600. This substitution leads to a conformational change resulting in constitutive kinase activity and phosphorylation of downstream targets. Concerning BRAFV600 mutations, about 85–90 % result in a substitution of a valine by a glutamic acid (BRAFV600E)
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