CK2β Is Expressed in Endometrial Carcinoma and Has a Role in Apoptosis Resistance and Cell Proliferation

Protein kinase CK2 (CK2) is a serine/threonine kinase that participates in important cellular processes. We have recently demonstrated that CK2 plays a role in resistance to TRAIL/Fas-induced apoptosis in endometrial carcinoma (EC) by regulating FLIP. Here, we assessed the immunohistochemical expression of CK2β in EC and checked its role in cell proliferation and anchorage-independent cell growth. CK2β immunostaining was assessed in two tissue microarrays, one constructed from paraffin-embedded blocks of 95 ECs and another from 70 samples of normal endometrium. CK2β expression was correlated with histological type; grade and stage; cell proliferation (Ki-67) and apoptotic index; immunostaining for cyclin D1, PTEN, AKT, β-catenin, and FLIP. Moreover, the Ishikawa EC cell line was subjected to down-regulation of CK2 by shRNA. CK2β expression was frequent in EC (nuclear, 100%; cytoplasmic, 87.5%). The staining was more intense in EC than in normal endometrium (P = 0.000), and statistically correlated with AKT, PTEN, β-catenin, and FLIP. In EC, CK2β expression correlated with cell proliferation. Knock-down of CK2β blocked colony formation of EC in soft agar, and also resulted in decreased expression of cyclin D1 and ERK phosphorylation. The results confirm that CK2β is widely expressed in EC, and suggest a role in cell proliferation and anchorage-independent cell growth.