BRAF, a target in melanoma: implications for solid tumor drug development

The successful translation of therapies targeting signal-transduction pathways that are activated by oncogenes has provided a model for molecularly targeted therapy, and the identification of mutations in v-raf murine sarcoma viral oncogene homolog B1 (BRAF), a serine/threonine kinase, has turned the attention of the melanoma field toward this concept. The current review indicated that BRAF represents an important target in cancer, in part because it is present in 7% of all cancers and also because it represents the first intracellular signaling molecule that is activated by point mutations for which single-agent therapy appears to have efficacy. Therapy for advanced melanoma has progressed slowly over the past 3 decades, although significant advances have been made in other cancers with the application of cytotoxic chemotherapy and targeted therapies. However, in melanoma, cytotoxic chemotherapies have severe limits, chemotherapy does not convincingly improve on the natural history of metastatic disease and has no role in the adjuvant setting, and cytokine therapy may have a niche in both the adjuvant and metastatic settings but confers only a modest benefit to a small proportion of patients at the cost of severe toxicity. Thus, there are few other cancers in which completely novel therapies are so highly prioritized in clinical research. Understanding network of signal-transduction pathways and how that network may adapt to BRAF inhibition or mitogen-activated protein kinase kinase inhibition will point to the next generation of clinical trials investigating rational combination regimens. The current investigations in melanoma will create a set of hypotheses to be tested in each cancer that harbors BRAF mutations.