CK2 Enzyme Affinity Against c-myc424-434 Substrate in Human Lung Cancer Tissue

CK2 is a serine threonine kinase that participates in a variety of cellular processes with more than 300defined substrates. This critical enzyme is known to be upregulated in cancers, but the role of this upregulationin carcinogenesis is not yet fully understood but c-myc, one of the defined CK2 substrates, is a well-known protooncogenethat is normally essential in developmental process but is also involved in tumor development. Weevaluated the optimal enzyme and substrate concentrations for CK2 activity in both neoplastic and non-neoplastichuman lung tissues using the c-myc424-434 peptide (EQKLISEEDL) as a substrate. The activities measured forthe neoplastic tissue were 600-750 U/mg protein while those for the control tissue was in the range of 650-800 U/mg. Km value for c-myc peptide was determined as 0.33 μM in non-neoplastic tissue and 0.18 μM in neoplastictissue. In this study, we did not observe an increased activity in the neoplastic tissue when compared with thenon-neoplastic lung tissue, but we recorded two times higher affinity for c-myc424-434 in cancer tissue. Consideringthe metabolic position of c-myc424-434, our results suggest that phosphorylation by CK2 may be important indimerization and thus it might affect the regulation of c-myc in cancer tissues.