Silencing of CEBPB-AS1 modulates CEBPB expression and resensitizes BRAF-inhibitor resistant melanoma cells to vemurafenib

Introduction of targeted therapy in the treatment of metastatic cutaneous malignant melanoma (CMM) has improved clinical outcome during the last years. However, only in a subset of the CMM patients, this will lead to long-term effects. CEBPB is a transcription factor that has been implicated in various physiological and pathological processes, including cancer development. We have investigated its prognostic impact on CMM and unexpectedly found that higherCEBPBmRNA levels correlated with a longer overall survival. Furthermore, in a small cohort of patients with metastatic CMM treated with BRAF-inhibitors, higher levels ofCEBPBmRNA expression in the tumor cells prior treatment correlated to a longer progression-free survival. We have characterized an overlapping antisense transcript,CEBPB-AS1, with the aim to investigate the regulation of CEBPB expression in CMM and its impact on BRAF-inhibitor sensitivity. We demonstrated that silencing ofCEBPB-AS1resulted in epigenetic modifications in the CEBPB promoter and in increasedCEBPBmRNA and protein levels, inhibited proliferation and partially resensitized BRAF-inhibitor resistant CMM cells to this drug-induced apoptosis. Our data suggest that targetingCEBPB-AS1may represent a valuable tool to sensitize CMM cells to the BRAF-inhibitor-based therapies.