fusion by insertion of 21q into 12p has been previously described, 6 we are the first to report the opposite phenomenon, namely insertion of 12p into 21q, producing the same result.

Introduction: Protein kinase CK2 is implicated in cellular proliferation and transformation. However, the clinical and biological significances of CK2 have not been elucidated in acute myeloid leukemia (AML). Experimental Design: We evaluated the biological significances of catalytic subunit of CK2 (CK2a) expression in leukemia cell lines and primary leukemic blasts obtained from AML patients. Results: In this study, the expression of CK2a was elevated in a substantial proportion of AML. In AML patients with normal karyotype, the disease-free survival and overall survival rates were significantly lower in the CK2a-high compared with the CK2a-low AML cases (P = 0.0252 and P = 0.0392, respectively). An induced overexpression of CK2a increased the levels of Ser 473 phosphorylated (p)-Akt/protein kinase B (PKB), p-PDK1, pFKHR, p-BAD, Bcl-2, Bcl-xL, Mcl-1, and XIAP. Treatment of U937 cell line and primary AML blasts with selective CK2 inhibitor, tetrabromobenzotriazole or apigenin, reduced the levels of these molecules in a dose-dependent manner. CK2a small interfering RNA treatment also resulted in a down-regulation of p-Akt/PKB and Bcl-2 in U937 cells. Apigenin-induced cell death was preferentially observed in the CK2a-high leukemia cell lines, HL-60 and NB4, which was accompanied by cytoplasmic release of SMAC/DIABLO and proteolytic cleavage of procaspase-9, procaspase-3, procaspase-8, and poly(ADP)ribose polymerase. An induced overexpression of CK2a potentially enhanced the sensitivity of U937 cells to the apigenin-induced cell death. Apigenin-induced cell death was significantly higher in CK2a-high AML compared with CK2a-low AML (P < 0.0001) or normal bone marrow samples (P < 0.0001).Conclusion: These findings strongly suggest protein kinase CK2a as an unfavorable prognostic marker and novel therapeutic target in AML.

Bromodomain and extraterminal domain (BET) inhibitors are promising epigenetic agents for the treatment of various subsets of acute myeloid leukemia (AML). However, the resistance of leukemia stem cells (LSC) to BET inhibitors remains a major challenge. In this study, we evaluated the mechanisms underlying LSC resistance to the BET inhibitor JQ1. We evaluated the levels of apoptosis and autophagy induced by JQ1 in LSC-like leukemia cell lines and primary CD34CD38 leukemic blasts obtained from AML cases with normal karyotype without recurrent mutations. JQ1 effectively induced apoptosis in a concentration-dependent manner in JQ1-sensitive AML cells. However, in JQ1-resistant AML LSCs, JQ1 induced little apoptosis and led to upregulation of beclin-1, increased LC3-II lipidation, formation of autophagosomes, and downregulation of p62/SQSTM1. Inhibition of autophagy by pharmacologic inhibitors or knockdown of beclin-1 using specific siRNA enhanced JQ1-induced apoptosis in resistant cells, indicating that prosurvival autophagy occurred in these cells. Independent of mTOR signaling, activation of the AMPK (pThr172)/ULK1 (pSer555) pathway was found to be associated with JQ1-induced autophagy in resistant cells. AMPK inhibition using the pharmacologic inhibitor compound C or by knockdown of AMPKα suppressed autophagy and promoted JQ1-induced apoptosis in AML LSCs. These findings revealed that prosurvival autophagy was one of the mechanisms involved in the resistance AML LSCs to JQ1. Targeting the AMPK/ULK1 pathway or inhibition of autophagy could be an effective therapeutic strategy for combating resistance to BET inhibitors in AML and other types of cancer. .

Cyclin-dependent kinase inhibitor p27Kip1 functions at the nuclear level by binding to cyclin E/cyclin-dependent kinase-2. It was shown that Akt or protein kinase B (Akt/PKB)-dependent phosphorylation of p27Kip1 led to the cytoplasmic mislocalization of p27Kip1, suggesting the potential abrogation of its activity. Here, we evaluated the localization of p27Kip1 protein in leukemic blasts in relation to Akt/PKB phosphorylation and clinical outcomes in acute myelogenous leukemia (AML). Western blot analysis of the nuclear and cytoplasmic fractions revealed a heterogenous localization pattern of p27Kip1 in AML. Cytoplasmic mislocalization of p27Kip1 was significantly associated with the constitutive serine 473 Akt/PKB phosphorylation in AML cells (P < 0.05). Transfection of U937 cells with an expression construct encoding the constitutively active form of Akt/PKB resulted in a remarkable increase in the levels of cytoplasmic p27Kip1. Whereas the transfection of U937 cells with a construct encoding dominant-negative Akt/PKB resulted in a recovery of nuclear localization of p27Kip1. Both the disease-free survival and overall survival are significantly shorter in AML cases with high cytoplasmic to nuclear ratio of p27Kip1 localization compared with the cases with low cytoplasmic to nuclear ratio (P ‫؍‬ 0.0353, P ‫؍‬ 0.0023, respectively). Multivariate analysis indicated that the cytoplasmic to nuclear ratio of p27Kip1 localization was an independent prognostic variable for both disease-free survival and overall survival (P ‫؍‬ 0.043, P ‫؍‬ 0.008, respectively). These findings additionally extend our understanding of the role of p27Kip1 in AML, and buttress the case of p27Kip1 mislocalization as a prognostic indicator and Akt/PKB/p27Kip1 pathway as a ready target for antileukemia therapy.

Summary. Phosphorylation of PTEN (phosphatase and tensin homologue) affects PTEN protein stability and function. In this study, phosphorylated PTEN (pPTEN) was observed in 45 (73AE8%) of 61 cases with acute myeloid leukaemia (AML). Phosphorylation of Akt and its downstream molecules [FKHR; Forkhead (Drosophila) homologue 1; and GSK-3b; glycogen synthase kinase 3 beta] was significantly associated with pPTEN (P < 0AE001). The complete remission rates were not different with respect to pPTEN, but overall survival was significantly shorter in patients with pPTEN (P < 0AE05). Constitutive PTEN phosphorylation may add insight into the molecular pathogenesis of AML, and may be a new parameter for an unfavourable outcome.