Differential gene expression analysis of leukemia-associated non-classical monocytes and their healthy counterpart show a leukemia-associated upregulation of genes involved in monocyte interactions with vascular endothelium during inflammation and vascular endothelial repair, such as PECAM1, CD44, ITGA4, CX3CR1, and TNFSF10, as well as significant downregulation of genes encoding subunits of HLA-DR. The gene discussed is PECAM1; the disease is leukemia.