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BRAF - Gene Mutation Analysis

Key Facts

• BRAF is an important signalling intermediate in the EGFR pathway
• A single activating mutation of the BRAF gene, V600E is most common
• BRAF mutation is particularly common in melanoma
• BRAF mutations rarely occur, if ever, alongside KRAS mutations

In different cancer types, in particular those of colorectum and lung, certain subsets of patients have been shown to benefit from anti-EGFR therapies; however a significant proportion shows no benefit from these agents. The BRAF gene encodes a protein that plays a key role in transmitting the original signal from EGFR, via KRAS (another gene which is frequently mutated), downstream to activate important cell functions, in particular proliferation and survival. Acquired mutations of this gene commonly occur in melanoma, colorectal and lung tumours. These mutations are activating, leading to uncontrolled signalling. One mutation, the so-called V600E mutation, predominates. This mutation has been shown to make colorectal cancers resistant to antibody-based anti-EGFR therapies. Patients with this mutation in their tumours are therefore considered unlikely to benefit from anti-EGFR therapies.

Source BioScience offers BRAF mutation testing based on two alternative CE-marked technologies, both suitable for archival FFPE tissue samples: 

• The Qiagen Therascreen™ BRAF Mutation Test uses real-time PCR to detect the V600E activating mutation found in the BRAF gene
• Pyrosequencing using the Qiagen/Biotage PyroMark™ BRAF Test provides an alternative technique for evaluating the same mutation

This mutation is associated with resistance to the anti-EGFR monoclonal antibody therapeutics cetuximab (Erbitux™) and panitumumab (Vectibix™). The results of mutation tests are reported as positive or negative for the presence of a particular mutation, along with additional information about relative frequency of that mutation in colorectal and lung tumours.

Note that KRAS and BRAF mutations tend to be mutually exclusive and, as the effect of an activating mutation in either gene is similar, it may be beneficial to test for both mutations simultaneously. Source BioScience Healthcare offers a bundled price for both tests on the same sample.

 Reference:

Di Nicolantonio et al. (2008) Wild-type BRAF is required for response to panitumumab or cetuximab in metastatic colorectal cancer. J Clin Oncol 26:5705