346 GENERATION OF A CONDITIONALLY REPLICATING ADENOVIRUS HARBORING A P53-DEPENDENT SELF-DESTRUCTION SWITCH FOR TREATMENT OF P53-ALTERED TUMORS

Abstract

several gastrointestinal tumors, e.g. pancreas or colon carcinoma. In hepatocellular carcinoma (HCC) CK2 expression or activity, as well as its contribution to cell survival have not been investigated so far. We compared expression and activity of CK2 in human HCC as well as in a mouse xenotransplant model of HCC to the respective non-tumorous liver tissue. Additionally we investigated the effect of CK2 inhibition by 2-Dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT) or by small interfering RNA (siCK2) on human hepatoma cell survival. Methods: CK2 expression and activity in tumor and liver tissue was measured by Western Blot analysis and by kinase activity assay. Using the human hepatoma cell lines HepG2 and HUH7, effects of CK2 inhibition on cellular proliferation were measured by MTT incorporation assay, cell counting and real time RT-PCR for cyclin D1 expression. Apoptosis induction was measured by caspase-3 activity assay and trypan blue staining. Inhibition of CK2 expression by siRNA as well as NFkB activity was measured by luciferase assay. Activity of the tumor relevant wnt signaling pathway was measured by conductin real time RT-PCR. Results: CK2 is significantly more active in about 50% of the investigated human HCC samples, as well as in the experimental HCC in mice. Inhibition of CK2 in human hepatoma cells reduced proliferation and induced cell death in a dose dependent manner. Inhibition of CK2 activity as well as expression of the CK2 beta subunit interfered with NFuB activation and enhanced TNF-induced cytotoxicity. Inhibition of CK2 activity interfered with the wnt signaling pathway as well as with cyclinD1 expression. Conclusions: CK2, which is over expressed and more active in HCC, seems to contribute to carcinoma cell survival and proliferation by triggering the wnt signalling pathway and CyclinD1 expression. Inhibition of CK2, either by application of inhibitors, such as DMAT, or by specific expressional down modulation, might represent a promising therapeutic approach in future HCC therapy.