When cultured HUVECs with different serum concentrations (5, 1, and 0%) for 8 and 16 h, the precursor miR-101-3p level was inversely proportional to serum concentration, without changing the expression of its host gene RNA 3′-terminal phosphate cyclase-like 1 (RCL1); however, the level of mature miR-101-3p decreased significantly (Figure 1a), and similar results were also observed in several tumor cell lines (Supplementary Figure S1a). This evidence concerns the gene RCL1 and neoplasm.