Effect of an inhibitor of protein kinase CK2 on radiosensitivity of human lung cancer cells

Objective To evaluate the effect of an inhibitor of protein kinase CK2 on the radiosensitivity of human lung cancer cells. Methods The protein levels of CK2 α and β subunits in different lung cancer cell lines were measured by Western blot. Clonogenic assays were performed to assess the effect of a CK2 inhibitor, quinalizarin, on the radiosensitivity of lung adenocarcinoma A549 cells and large cell lung cancer H460 cells. The effects of the combination of quinalizarin and X-ray irradiation on the apoptosis and cell cycle of A549 and H460 cells were measured by flow cytometry. The differences between two groups were analyzed by analysis of variance and t-test. Results Western blot revealed that the α and β subunits of CK2 were overexpressed in non-small cell lung cancer cells (A549, H460, and H1650 cells), which were considered insensitive to X-ray irradiation, whereas a lower expression of these two subunits were found in small cell lung cancer cells (H446 cells), which were sensitive to X-ray irradiation. The clonogenic assays showed that A549 and H460 cells pre-exposed to quinalizarin had a significantly lower survival fraction compared with the control group and had a sensitization enhancement ratio greater than 1.0(D0 were 2.771 and 2.463 respectively). The combination of quinalizarin and X-ray irradiation did not increase the apoptosis of A549 and H460 cells (X-ray+ Quinalizarin vs. Quinalizarin, A549, P=0.487 and H460, P=0.254), but caused significant G2/M arrest compared with under X-ray irradiation only (X-ray+ Quinalizarin: X-ray, A549, P=0.000; H460, P=0.002 and X-ray+ Quinalizarin: Quinalizarin, A549, P=0.000; H460, P=0.000). Conclusions Quinalizarin, as a CK2 inhibitor, can increase the radiosensitivity of non-small cell lung cancer cells. Key words: Lung neoplasms cell line; Radiosensitivity; Protein Kinase CK2; Quinalizarin