Overexpression of Nuclear Protein Kinase CK2 a Catalytic Subunit (CK2a) as a Poor Prognosticator in Human Colorectal Cancer

Background: Colorectal cancer (CRC) is one of the most common malignancies but the current therapeutic approaches for advanced CRC are less efficient. Thus, novel therapeutic approaches are badly needed. The purpose of this study is to investigate the involvement of nuclear protein kinase CK2 a subunit (CK2a) in tumor progression, and in the prognosis of human CRC. Methodology/Principal Findings: Expression levels of nuclear CK2a were analyzed in 245 colorectal tissues from patients with CRC by immunohistochemistry, quantitative real-time PCR and Western blot. We correlated the expression levels with clinicopathologic parameters and prognosis in human CRC patients. Overexpression of nuclear CK2a was significantly correlated with depth of invasion, nodal status, American Joint Committee on Cancer (AJCC) staging, degree of differentiation, and perineural invasion. Patients with high expression levels of nuclear CK2a had a significantly poorer overall survival rate compared with patients with low expression levels of nuclear CK2a. In multi-variate Cox regression analysis, overexpression of nuclear CK2a was proven to be an independent prognostic marker for CRC. In addition, DLD-1 human colon cancer cells were employed as a cellular model to study the role of CK2a on cell growth, and the expression of CK2a in DLD-1 cells was inhibited by using siRNA technology. The data indicated that CK2a-specific siRNA treatment resulted in growth inhibition