Moreover, the Herlyn laboratory confirmed in tissue samples from patients in the PLX4032 trialtaken both before treatment and after they developed resistancethat an increased expression of the IGF-1 receptor is associated with resistance to BRAF inhibitors. None of the laboratory-generated cell lines or the post-relapse patient's tumor samples analyzed had new mutations in the BRAF, NRAS, or c-Kit genes.
Additionally, the researchers noted an association between the loss of a tumor suppressor called PTEN, and resistance to BRAF inhibitors in melanoma cell lines. The scientists found that the relapsed tumor of one patient included in the study lost the PTEN gene, even though it was present before treatment. These findings suggest that loss of PTEN could be an additional way that melanoma cells gain resistance to BRAF inhibitors. The Wistar group continues to investigate these and other mechanisms of resistance, as they expect that several will likely arise given the heterogeneous nature of melanoma.
"Tumors are efficient engines of evolutionthey are going to find a way around most treatments, so we want to kill all the malignant cells from the very beginning," said Villanueva. "By targeting both pathways simultaneously you hit these cells with two punches from which they cannot recover."
"If you do this at the outset of treatment, we reason, it will prevent melanoma survival and hopefully improve patient outcomes," Villanueva added.
|Contact: Greg Lester|
The Wistar Institute