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Updated: Dec 21, 2025
Employing Digital Droplet PCR to Detect BRAF V600E Mutations in Formalin-fixed Paraffin-embedded Reference Standard Cell Lines
Published on: October 8, 2015
Differential responsiveness to BRAF inhibitors of melanoma cell lines BRAF V600E-mutated
Muna Al Hashmi1, Konduru S Sastry1, Lee Silcock1
1Research Branch, Sidra Medical and Research Center, 26999, Doha, Qatar.
Background:
Most mutations in melanoma affect one critical amino acid on BRAF gene, resulting in the V600E substitution. Patient management is often based on the use of specific inhibitors targeting this mutation.
Methods:
DNA and RNA mutation status was assessed in 15 melanoma cell lines by Sanger sequencing and RNA-seq. We tested the cell lines responsiveness to BRAF inhibitors (vemurafenib and PLX4720, BRAF-specific and sorafenib, BRAF non-specific). Cell proliferation was assessed by MTT colorimetric assay. BRAF V600E RNA expression was assessed by qPCR. Expression level of phosphorylated-ERK protein was assessed by Western Blotting as marker of BRAF activation.
Results:
Three cell lines were discordant in the mutation detection (BRAF V600E at DNA level/Sanger sequencing and BRAF WT on RNA-seq). We initially postulated that those cell lines may express only the WT allele at the RNA level although mutated at the DNA level. A more careful analysis showed that they express low level of BRAF RNA and the expression may be in favor of the WT allele. We tested whether the discordant cell lines responded differently to BRAF-specific inhibitors. Their proliferation rate decreased after treatment with vemurafenib and PLX4720 but was not affected by sorafenib, suggesting a BRAF V600E biological behavior. Yet, responsiveness to the BRAF specific inhibitors was lower as compared to the control. Western Blot analysis revealed a decreased expression of p-ERK protein in the BRAF V600E control cell line and in the discordant cell lines upon treatment with BRAF-specific inhibitors. The discordant cell lines showed a lower responsiveness to BRAF inhibitors when compared to the BRAF V600E control cell line. The results obtained from the inhibition experiment and molecular analyses were also confirmed in three additional cell lines.
Conclusion:
Cell lines carrying V600E mutation at the DNA level may respond differently to BRAF targeted treatment potentially due to a lower V600E RNA expression.
Insights
Melanoma cell lines with BRAF V600E DNA mutations may show varied responses to targeted therapies. This difference in BRAF inhibitor effectiveness could be linked to lower V600E RNA expression levels.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Most melanoma cases involve a BRAF gene mutation leading to the V600E substitution.
- Patient treatment often relies on targeted therapies directed at this specific mutation.
Purpose of the Study:
- To investigate the response of melanoma cell lines with BRAF V600E mutations to BRAF inhibitors.
- To explore potential discrepancies between DNA mutation status and RNA expression in predicting treatment response.
Main Methods:
- Assessed DNA and RNA mutation status in 15 melanoma cell lines using Sanger sequencing and RNA-seq.
- Tested cell line responsiveness to BRAF inhibitors (vemurafenib, PLX4720, sorafenib) via proliferation assays (MTT).
- Quantified BRAF V600E RNA expression (qPCR) and p-ERK protein levels (Western Blotting).
Main Results:
- Identified three cell lines with discordant BRAF mutation detection between DNA and RNA levels.
- Discordant cell lines, despite having BRAF V600E DNA mutation, exhibited lower RNA expression and reduced sensitivity to BRAF-specific inhibitors compared to controls.
- Western Blotting confirmed decreased p-ERK protein levels in discordant cell lines upon inhibitor treatment, indicating BRAF pathway inhibition.
Conclusions:
- Melanoma cell lines with BRAF V600E mutations may display differential responses to targeted treatments.
- Lower BRAF V600E RNA expression could be a factor influencing treatment efficacy in these cell lines.
