MPO and juvenile myelomonocytic leukemia: Using this definition, 34 of 44 JMML cases (77 %) showed hypermethylation of the cAMP-responsive element-binding protein-binding protein (CREBBP) gene (the assay was uninformative in one case), 20 of 45 (44 %) were hypermethylated in the MPO gene, and 19 of 45 (42 %) carried a hypermethylated SLC12A8 gene (Fig. 1b).