Protein kinase CK2 in hematologic malignancies: reliance on a pivotal cell survival regulator by oncogenic signaling pathways

CK2 is a multitask kinase whose role is essential for a countless number of cellular processes, many of which are critical for blood cell development. A prevailing task for this kinase rests on counteracting programmed cell death triggered by multiple stimuli. CK2 is overexpressed in many solid tumors and in vivo mouse models have proven its tumorigenic potential. Recent data have suggested that CK2 may also have a significant role in the pathogenesis of hematopoietic tumors, such as multiple myeloma, chronic lymphocytic leukemia, acute myelogenous leukemia, acute lymphoblastic leukemia and chronic myeloproliferative neoplasms. CK2 regulates hematopoiesis-associated signaling pathways and seems to reinforce biochemical cascades indispensable for tumor growth, proliferation and resistance to conventional and novel cytotoxic agents. Although its activity is multifold, recent evidence supports the rationale of CK2 inhibition as a therapeutic strategy in solid and hematological tumors and phase-I clinical trials are in progress to test the efficacy of this innovative therapeutic approach. In this review, we will summarize the data supporting CK2 as an oncogenic kinase in blood tumors and we will describe some critical signaling pathways, whose regulation by this protein kinase may be implicated in tumorigenesis.