NPM1 and cancer: These cell-free miRNAs are probably released by cancer cells, necrotic cells, and/or apoptotic cells along with their associated proteins or lipids, such as the RNA-binding protein NPM1 (nucleophosmin), AGO proteins (argonaute 1/2), and high-density lipoprotein (HDL), to avoid RNase degradation in blood circulation (15, 16, 54).