Direct detection of a BRAF mutation in total RNA from melanoma cells using cantilever arrays

Malignant melanoma, the deadliest form of skin cancer, is characterized by a predominant mutation in the BRAF gene1,2,3. Drugs that target tumours carrying this mutation have recently entered the clinic4,5,6,7. Accordingly, patients are routinely screened for mutations in this gene to determine whether they can benefit from this type of treatment. The current gold standard for mutation screening uses real-time polymerase chain reaction and sequencing methods8. Here we show that an assay based on microcantilever arrays can detect the mutation nanomechanically without amplification in total RNA samples isolated from melanoma cells. The assay is based on a BRAF-specific oligonucleotide probe. We detected mutant BRAF at a concentration of 500 pM in a 50-fold excess of the wild-type sequence. The method was able to distinguish melanoma cells carrying the mutation from wild-type cells using as little as 20 ng µl–1 of RNA material, without prior PCR amplification and use of labels. Microcantilever arrays are used to detect individual point mutations in a gene associated with melanoma cancer, offering a rapid test for deciding whether or not patients are eligible to receive drug treatment.