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. (authors)