Abstract 5348: Targeting MEK, alone and in combination with BRAF, in metastatic BRAFK601E-mutated melanoma

Abstract Mitogen-activated protein kinase/ERK signaling pathway has been one of the major mechanisms underlying melanoma haboring BRAF mutation. Of these, K601E mutation belongs to a rare mutation sub-type, comprising only 3% of the BRAF mutations in melanoma. Although patients with BRAF V600E/K mutation respond to MEK inhibitor, whether it also applies to those with BRAF K601E mutation remains elusive. Here, we examined the effects of MEK and BRAF/MEK inhibition on BRAFK601E-expressing melanoma cells. Melanoma cell line (MeWo) was transfected with doxycycline-inducible vector encoding wild-type or K601E-mutant BRAF. Subsequently, cells or xenograft-bearing mice were treated with trametinib, dabrafenib plus trametinib or sorafenib plus trametinib. Compared with BRAFWT, MTT assay demonstrated that BRAFK601E cells were more sensitive towards drug treatment. The effects of combined treatment were more profound. Tumorigenicity assay showed that trametinib treatment inhibited tumor growth of BRAFK601E xenografts. Our preliminary results demonstrated the therapeutic values of MEK and BRAF/MEK inhibitors against BRAFK601E-mutated melanoma. As previous studies report the superior therapeutic effects of BRAF/MEK inhibitors over MEK inhibitor alone, phenotype characterization of the cells, as well as underlying mechanisms behind such response, worth further investigation. Citation Format: Sze Man Chan, Sin Ting Chow, Sai Fung Yeung, Kwok Wing Stephen Tsui. Targeting MEK, alone and in combination with BRAF, in metastatic BRAFK601E-mutated melanoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5348.