Figure 2. Expression of multidrug resistance-associated protein 1 (MRP1) messenger RNA (mRNA) in peripheral blood of healthy individuals and the HL-60 cell line. The copy number of MRP1 is expressed as the ratio of MRP1 to β2M copy number (each circle represents a sample). In accordance with MRP1 expression in healthy individuals, the cutoff is defined as mean ± 2 standard deviations (SD). The HL-60 resistant cell line showed MRP1 expression levels higher than the cutoff.