Immunohistochemistry with a mutation-specific monoclonal antibody as a screening tool for the BRAFV600E mutational status in primary cutaneous malignant melanoma

Abstract

The V600E mutation of BRAF has emerged as both an effective biomarker and therapeutic target for select benign and malignant cutaneous and non-cutaneous human tumors and is typically determined using DNAbased techniques that include allele-specific PCR and direct DNA sequencing. Recently however, the development of new antibodies directed against the V600E protein has opened the door for an easier and more efficient strategy for identifying this mutation. Our present aim was to determine the efficacy of one such antibody, anti-B-Raf (V600E), a mouse monoclonal antibody in which the immunogen is a synthetic peptide derived from the internal region of BRAFV600E. A total of 35 cases of primary cutaneous melanoma were evaluated using a combination of DNA-based techniques that included allele-specific PCR and/or direct DNA sequencing and immunohistochemistry. Cases of papillary thyroid carcinomas (n ¼ 5) and colorectal carcinomas (n ¼ 5), known to harbor the BRAFV600E mutation, served as positive controls for the study. DNA analyses revealed that 6 of 35 (17%) cases of the primary cutaneous malignant melanoma possessed the BRAFV600E mutation. For immunohistochemical analyses, cytoplasmic positivity with anti-B-Raf was noted in 7 of 35 (20%) cases of primary melanoma and in all 10 positive controls. Statistical analyses of the data demonstrated that the sensitivity of the immunohistochemistry was 100% and specificity was 97%. Findings from the current study support the potential use of immunohistochemistry as an ancillary screening tool to assess the BRAFV600E mutation status in primary cutaneous melanoma.

Assessment of BRAF V600E Status in Colorectal Carcinoma: Tissue-Specific Discordances between Immunohistochemistry and Sequencing

“…Our findings show that in colorectal carcinoma, VE1 IHC is not a reliable method for determining the BRAF V600E mutational status. In contrast, our results in melanoma and papillary thyroid carcinoma are in keeping with previously published data showing excellent concordance between molecular analysis and VE1 IHC (36)(37)(38)(39)(40)(41).…”

Immunohistochemistry is highly sensitive and specific for the detection of NRASQ61R mutation in melanoma

“…Previous immunohistochemical analyses using BRAFV600E antibody have shown that intratumoral heterogeneity of BRAF mutation is not generally observed [23][24][25] and up to 100% concordance between matched primary and metastatic melanomas has been reported. 24 These results support the routine use of immunohistochemistry with the anti-BRAFV600E antibody as an ancillary screening tool to assess the BRAFV600E mutation status in melanoma patients 26 for treatment planning.…”

Utility of BRAF V600E Immunohistochemistry Expression Pattern as a Surrogate of BRAF Mutation Status in 154 Patients with Advanced Melanoma

“…This antibody provides highly sensitive (97–100%) and specific (97–100%) insight into the BRAF V600E mutation status of patients with melanoma [7–12]. Homogeneous BRAF V600E IHC expression in melanoma highly correlates with the presence of BRAF V600E mutation when compared with sequencing methods as the gold standard.…”