Evaluation of Collection and Processing Conditions for Gene Expression Analysis Using Human Myeloid Cells

The population of blast cells among peripheral blood mononuclear cells (PBMCs) obtained from patients is a desirable specimen for analyzing gene expression in diseases including acute myeloid leukemia. Although the enrichment of blast cells often needs to be performed at a central laboratory, acceptable conditions for sample transport from clinical sites remain to be established. We evaluated storage temperature, duration, and tube type before initiating sample processing for the analysis of cluster of differentiation (CD)33⁺ myeloid cells among PBMCs as an alternative to CD34⁺/CD33⁺ blast cells. CD33⁺ myeloid cells were successfully purified by MACS. The cell viability and the RNA integrity were sustained during storage up to 48 hours before sample processing. Storage at 4°C had minimal effects on gene expression, whereas storage at room temperature induced the senescence pathway, characterized by the expression of stress-inducible genes. A CPT tube was also better than an ethylenediaminetetraacetic acid tube for minimizing gene expression change. Our study provided important clues for establishing a sample handling approach for gene expression analysis with purified cell fractions from human PBMCs. To keep the variation of gene expression to a minimum, samples should be delivered at 4°C within 48 hours before processing.