Dysregulated Expression of Protein Kinase CK2 in Renal Cancer

Renal cell carcinomas (RCCs) have notoriously been shown to be refractory to traditional therapies including radiation and cytokine therapies. The use of molecularly targeted therapies against mTOR, VEGF, and other angiogenic factors has significantly improved the standards of care of this disease. Yet, improvements are still required as many of the current therapies are limited by acquired resistance. However, the recent development of molecular targeted therapies involving kinase inhibitors has changed the clinical management of RCCs. Protein kinase CK2 is critical for the activation of multiple pro-survival signaling pathways, and its catalytic activity is invariably elevated in various types of tumors. However, the precise role of CK2 has never been addressed in RCCs. In this study, we have analyzed the activity of CK2 and the expression of its subunits in a small cohort of RCC tumors. This analysis revealed, in the majority of tumor samples, an upregulation of the CK2 catalytic subunits that was not correlated with mRNA abundance in the majority of tumor samples. Moreover, relative levels of the three CK2 subunits varied significantly between tumor samples, and a positive correlation was observed between low CK2β expression and an upregulation of the ZEB2 mesenchymal marker in a subset of tumor samples. Using the CK2 inhibitor CX-4945 to downregulate the CK2 catalytic activity in 786-O cells as a model of VHL-deficient renal cancer cell line, we showed that CK2 represents a potential promising therapeutic target in RCCs.