Subcellular immunolocalization of protein kinase CK2 in normal and carcinoma cells

CK2 is a messenger-independent protein serine/threonine kinase that has bee n implicated in cell growth and proliferation. Our recent analysis of squam ous cell carcinomas of the head and neck (SCCHN) revealed a significant ele vation in CK2 activity in these tumor cells relative to normal mucosa of th e upper aerodigestive tract and suggested a correlation with aggressive tum or behavior and poor clinical outcome. In order to further define the distr ibution of CK2 in these tissues, we have examined the immunohistochemical s taining pattern of surgical specimens of both SCCHN tumors and normal upper aerodigestive tract mucosa using a monoclonal antibody directed against th e catalytic subunit CK2-alpha of the kinase, and have compared these data w ith the subcellular distribution of CK2 activity in these same tissues. The se measurements showed that CK2 is predominantly localized to the nuclei of the tumor cells, which agreed closely with the immunohistochemical stainin g pattern of CK2-alpha in tumor cells. The chiefly nuclear distribution of CK2-alpha immunostaining found consistently in SCCHN tumor cells and tumor- infiltrating lymphocytes contrasted with a relatively more predominant cyto solic staining pattern exhibited by various cellular constituents of normal oropharyngeal mucosa. The immunostaining pattern of CK2-alpha revealed tha t staining was observed in the cells stained for the proliferation-marker K i-67; however, strong distinct immunostaining for CK2-alpha was also observ ed in large numbers of other cells in these same tumors, suggesting that CK 2 elevation in these tumors is not a reflection of proliferative activity a lone, but may also relate to the pathobiological behavior of the tumor. (C) 1999 Elsevier Science Ltd. All rights reserved.