Protein kinase CK2alpha as an unfavorable prognostic marker and novel therapeutic target in acute myeloid leukemia.
BACKGROUND
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).


METHODS
We evaluated the biological significances of catalytic subunit of CK2 (CK2alpha) expression in leukemia cell lines and primary leukemic blasts obtained from AML patients.


RESULTS
In this study, the expression of CK2alpha 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 CK2alpha-high compared with the CK2alpha-low AML cases (P=0.0252 and P=0.0392, respectively). An induced overexpression of CK2alpha increased the levels of Ser473 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. CK2alpha 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 CK2alpha-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 CK2alpha potentially enhanced the sensitivity of U937 cells to the apigenin-induced cell death. Apigenin-induced cell death was significantly higher in CK2alpha-high AML compared with CK2alpha-low AML (P<0.0001) or normal bone marrow samples (P<0.0001).


CONCLUSIONS
These findings strongly suggest protein kinase CK2alpha as an unfavorable prognostic marker and novel therapeutic target in AML.
Kim
Jin Seok
JS
Department of Internal Medicine, Brain Korea 21 Research Team of Nanobiomaterials for the Cell-Based Implants, Medical Research Center, Yonsei University College of Medicine, Seoul, Korea.
Eom
Ju In
JI
Cheong
June-Won
JW
Choi
Ae Jin
AJ
Lee
Jin Koo
JK
Yang
Woo Ick
WI
Min
Yoo Hong
YH
D000293:Adolescent; D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000494:pharmacology*; D047310:Apigenin / Q000494:pharmacology; D047390:Casein Kinase II / Q000502:physiology*; D020169:Caspases / Q000378:metabolism; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D018572:Disease-Free Survival; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007621:Karyotyping; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D020298:U937 Cells
D000970:Antineoplastic Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D047310:Apigenin; D047390:Casein Kinase II; D051057:Proto-Oncogene Proteins c-akt; D020169:Caspases