Compared to healthy individuals, proteasome levels were significantly higher in CML patients (mean ± standard deviation: CML 12.2 ± 7.6 μg/mL vs. healthy subjects 3.3 ± 2.0 μg/mL, P < 0.01), in patients with BCR/ABL-negative MPN (14.6 ± 6.7 μg/mL, P < 0.001 vs. healthy controls), as well as in MDS individuals (17.5 ± 14.3 μg/mL, P < 0.01 vs. healthy controls). Here, BCR is linked to myeloproliferative disorder.