HHEX and chronic myelogenous leukemia, BCR-ABL1 positive: Our previous work has shown that in chronic myeloid leukaemia cells PRH activity is controlled by Protein Kinase CK2 (Casein Kinase 2).12, 13, 14 CK2 is a ubiquitously expressed serine/threonine kinase important in the regulation of cell proliferation and cell stress responses.15 CK2 activity is increased markedly in benign prostatic hyperplasia (BPH) and prostatic adenocarcinoma.16 The CK2 tetramer comprises two regulatory β-subunits and two catalytic α-subunits.