PBK/TOPK Is a Novel Mitotic Kinase Which Is Upregulated in Burkittʹs Lymphoma and Other Highly Proliferative Malignant Cells

PBK/TOPK is a recently cloned serine/threonine kinase which is phosphorylated during mitosis. Earlier work indicated that this kinase is upregulated in a Burkittʹs lymphoma cell line (GA-10). To determine whether PBK/TOPK is upregulated in other mitotically active neoplastic cell lines and tissues, Northern analysis was performed on a panel of malignant cell lines and on clinical samples from patients with leukemia or lymphoma. While PBK/TOPK mRNA was not detectable in normal peripheral blood cells and was weakly expressed in hyperplastic tonsillar B-cells, significantly higher levels of mRNA were detected in 8 Burkittʹs lymphoma cell lines, 10 other neoplastic cell lines, and 2 clinical samples—one derived from a patient with ALL and a second derived from a patient with relapsed myeloma. In addition, Northern analysis of fetal tissues showed upregulated expression of PBK/TOPK in fetal kidney, lung, spleen, brain, and testis. These data suggest that PBK/TOPK expression is increased in highly proliferative malignant cells and during normal fetal development.