PTEN and acute promyelocytic leukemia: PTEN mRNA level was measured using quantitative RT-PCR in 42 APL patients (mean value 1.5 ± 0.8), and compared to that of 42 AML patients (mean value 2.6±1.2) and 6 normal bone marrow (NBM) (mean 3.5±2.5) (Figure 1a).