Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Karolinska Institutet Background/Introduction Proteasome inhibitors (PI) have contributed to longer survival in multiple myeloma although PI related cardiovascular adverse events are common. Associated to carfilzomib hypertension, coronary ischemic events and heart failure (both with reduced and preserved left ventricular ejection fraction). Here we explore the effect of PIs on endothelial gene expression. Methods Human aortic endothelial cells (HAEC) were incubated for 24 h with carfilzomib or bortezomib at different concentrations. Gene expression determined using using bcl2fastq (v2.20.0), and read quality was assessed using FastQC (v0.11.8). For each group the 100 genes with highest ratio were used for analysis of gene ontology (GO), biological processes using ClusterProfiler. The carfilzomib / bortezomib >1.5 was determined in the relevant GO groups. Results PIs induce gene expression related to inflammatory response and oxidative stress, more pronounced for carfilzomib. 44 / 31 genes related to "cytokine-mediated signaling pathway" and "response to oxidative stress pathway. NR4A3 was 15.5 fold above control while its increase with bortezomib was modest. Discussion Both carfilzomib and bortezomib induce genes related in inflammation and oxidative stress. Carfilzomib induced more pronounced upregulations in several genes, that stimulates expression of increased cellular respiration. Our result show a differentiated effect on endothelial cell gene expression by carfilzomib and bortezomib -a possible explanation to the differences in cardiovascular toxicity profile. Figure 1. Selected GO, Biological function characteristics calculated on the top 100 fold-change genes in each group. C2 high dose carfilzomib, B1 and B2 low and high dose bortezomib. C1 did not converge to any GO characteristics.