Protein kinase CK2: Signaling and tumorigenesis in the mammary gland

Breast cancer is a major cause of cancer death in women, and the genetic abnormalities leading to the common sporadic forms of the disease are still under active investigation. CK2 has been reported to be upregulated in human breast cancer, which these studies confirm; CK2 is also upregulated in rat carcinogen-induced breast tumors. Transgenic mice overexpressing CK2 alpha in the mammary gland develop mammary hyperplasia, dysplasia, and eventually adenocarcinomas, demonstrating that dysregulated expression of CK2 can contribute to transformation of the mammary epithelium. These mammary tumors have evidence of activation of the Wnt and NF kappaB pathways and upregulation of c-Myc. CK2 is capable of phosphorylating the key signaling molecule in the Wnt pathway, the transcriptional cofactor beta -catenin, and regulating its turnover. CK2 is known to phosphorylate I kappaB and thereby regulate basal NF kappaB levels; in the mammary cell lines and tumors, CK2 activity correlates with NF kappaB levels and inhibition of CK2 downregulates NF kappaB. Thus, CK2 may promote breast cancer through dysregulation of key pathways of transcriptional control in the mammary epithelium, and inhibition of CK2 has a potential role in the treatment of breast and other cancers.