Abstract 5598: Interaction between BRAF inhibitor PLX-4720 and CDK inhibitors can sensitize melanoma cells with BRAF V600E mutation

Abstract

Abstract BRAF V600E mutation happens in 60% of all melanomas cases and this mutation is responsible to poor prognosis of the disease. BRAF is part of the MAPK signaling pathway and the V600E mutation of BRAF confers full activation of this survival pathway. Several clinical trials are being conducted using mutated BRAF as a target but so far, all this trials works during a certain moment but soon, melanoma cells becomes resistant to treatment by activating some survival pathways that can continues the signal initialized in the MAPK pathway. Our objective is to evaluate if the combination of BRAF inhibitors and CDKs inhibitors can suppress the acquired resistance of V600E melanoma cells to BRAF inhibitors. Two melanoma cell lines were used in this study. The SKMel 28 cell line, which has BRAF V600E mutation, and the SKMel 02, which is wild type to BRAF. Olomoucine and Roscovitine were the CDKs inhibitors used in this study, while PLX-4720 was BRAF inhibitor. Western blot and Real time PCR were used to verify some survival pathways, like the MAP3K8 and the PRKD3 pathway, that are overexpressed after BRAF inhibition and MTT assay was used to verify cell viability with both treatments combined. The combination of Olomoucine and PLX-4720 or Roscovitine and PLX-4720 could sensitize the BRAF V600E mutated melanoma cell line SKMel 28, but not the BRAF wild type melanoma cell line SKMel 02. Two survival pathways (MAP3K8 and PRKD3) which are activated after BRAF inhibition by PLX-4720 were downregulated in the presence of the CDKs inhibitors in the SKMel 28 melanoma cell line. Also, the retinoblastoma protein was not phosphorylated when the SKMel28 melanoma cell line was treated with the BRAF inhibitor together with the CDKs. The treatment with the BRAF inhibitor and the CDKs inhibitors can sensitize BRAF V600E melanoma cells by decreasing cell viability, downregulation of survival pathways induced by the BRAF inhibitor and preventing Rb phosphorylation. This strategy may overcome the acquired resistance of BRAF-mutated melanoma after treatment with its inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5598. doi:1538-7445.AM2012-5598