This past summer saw a revolution in melanoma therapy. Patients whose melanoma lesions contain a mutation in the BRAF gene were successfully treated with a BRAF-specific inhibitor, PLX4032. Reports of the drug trial described shrinking tumors and improved health. Yet seven months after therapy began the tumors returned and resumed growing. Now, scientists at The Wistar Institute explain why: the tumor learns to signal around the blocked gene by adjusting its molecular wiring. They also show how to overcome resistance by simultaneously targeting multiple signaling pathways.
The researchers see this as further evidence that some cancers must be treated with multiple targeted drugs at the outset of treatment. Their findings are published in the December 14 issue of the journal Cancer Cell.
"The evidence suggests that targeting mutant BRAF can kill cancer cells, but it is not enough by itself to finish off melanoma," said Meenhard Herlyn, D.V.M., D.Sc., director of The Wistar Institute Melanoma Research Center and leader of Wistar's Molecular and Cellular Oncogenesis program. "The good news is that drugs are being developed to work in combination with BRAF inhibitors, which our data clearly shows is our best option if we intend to beat advanced melanoma."
Melanoma is the deadliest, most aggressive form of skin cancer. While surgical treatment of early melanoma leads to 90 percent cure rates, advanced melanoma is notoriously resistant to chemotherapy and has a tendency to metastasize, or spread, throughout the body. According to the World Health Organization, cases of the disease continue to rise, which has helped spur research into therapies such as BRAF inhibitors.
To study how melanoma responds to BRAF inhibitors, the Herlyn lab took melanoma cells with the BRAF mutation and tested them against a variety of anti-mutant BRAF drugs. When exposed to the drugs, the cells died off dramatically only to grow back again. In fact,
|Contact: Greg Lester|
The Wistar Institute