MedicalResearch.com Interview with:
Russel E. Kaufman, MD President Emeritus
Professor, Molecular and Cellular Oncogenesis Program
Molecular and Cellular Oncogenesis Program
The Wistar Institute
Medical Research: What is the background for this study? What are the main findings?
Response: Targeted therapies in cancer were hailed as a “magic bullet” because of their ability to act upon the mutations responsible for cancer while leaving nearby healthy cells alone. Using an approach like this, it would make sense that therapies designed to target mutations of BRAF
V600E/K could be effective for melanoma, since that gene is mutated in about half of all cases of the disease.
However, we’ve learned over time that these targeted therapies simply aren’t as effective as we had hoped they would be. In the case of these BRAF inhibitors, while patients do live slightly longer, they eventually relapse within months of treatment. We wanted to know why this was happening.
We decided to look at macrophages, which are the most abundant inflammatory cells in
melanoma. The more macrophages present in a patient with melanoma, the worse his or her outcome will be. They’ve been linked to cancer progression, but before this study, no one had really looked at the role they may play in the resistance to treatment with BRAF inhibitors.
We found that BRAF inhibitors activate the mitogen-activated protein kinase (MAPK) pathway in macrophages. When this pathway is activated, it leads to the production of vascular endothelial growth factor (VEGF), a signaling protein closely associated with angiogenesis. The VEGF produced in the macrophages is able to activate the MAPK pathway in melanoma cells, thereby stimulating the growth of cancer cells.
Taking these findings one step further, we discovered that when we blocked the MAPK pathway or VEGF signaling, we appeared to reverse macrophage-mediated resistance. When we targeted macrophages, we were able to increase the antitumor activity of BRAF inhibitors in mouse and human models.
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