LC Capilliposide Increases Sensitivity To Irradiation In Non-small Cell Lung Cancer Cells

Objective Lung cancer is the most common malignant tumor and the leading cause of human cancer-related deaths. In tremendous efforts to improve local control of the disease and to increase survival, concurrent chemoradiotherapy has been explored as a standard therapy, producing the highest cure rates but with an increased level of toxicity. New nontoxic or low toxic chemotherapy regimens to be given with radiation are thus urgently needed to improve survival with reducing treatment morbidity for non-small-cell lung cancer patients.Methods In the first part proliferation inhibition by LC capilliposide was assessed by MTS assay. Apoptotic cells were measured by flow cytometric analysis. To investigate the potential radiosensitization effect of LC capilliposide, we determined SER values with clonogenic survival assay. To test the combination index values we determined LD50 values for LC capilliposide and IR in H460 and PC-9 cells. With pretreatment of increasing doses of LC capilliposide for 48 hours followed by increasing doses IR at constant ratio of doses. We determined the expression of apoptotic proteins used Western blot analysis.In the second part we examined the effects of LC capilliposide on DNA damage repairs activities using U2OS reporter cells and in vivo end-joining assay. We determined the expression of the proteins relevant non-homologous end-joining DNA repair used Western blot analysis. And to verify the role of NHEJ on LC capilliposide-induced radiosensitization, we further determined the changes of radiosensitivity in H460 and PC-9 cells with silencing of DNA-pKcs protein and percentage of cells with residual y-H2A.X foci in cells after irradiation.Lastly, we investigated the potential inhibition of LC capilliposide on cancer cell invasion.Results In the first part LC capilliposide inhibited cell proliferation in a dose-and time-dependent fashion. The combination of LC capilliposide and radiotherapy could elicit a greater inhibition of growth and apoptosis than radiotherapy alone in lung cancer cells. We found that pretreatment of LC capilliposide at 1μg/mL for 48 hours resulted in SER value of 1.67±0.22in H460,2.07±0.34 in PC-9 and 1.43±0.21 in H1299 cells, respectively. The result of median effect analysis showed the combination index values of< 1.0 in H460 cells with the combination of 4.84±0.13μg/mL of LC capilliposide and 4.99±0.05 Gy of IR and below, and in PC-9 cells with the combination of 0.128±0.012μg/mL of LC capilliposide and 0.168±0.03 Gy of and above, indicating that LC capilliposide can induce synergistic radiosensitization in human lung cancer cells. Western blot analysis showed LC capilliposide decreased expression of irradiation-induced-apoptotic proteins.In the second part, the result of Flow Cytometer demonstrated that LC capilliposide could affect non-homologous end-joining DNA repair machinery in lung cancer cells in response to radiotherapy treatment, and induce synergistic radiosensitization of human lung cancer cells. With western blot analysis, we found that treatment with 1μg/mL of LC capilliposide could decrease expressions of DNA-pKcs and Rad50 proteins in lung cancer cells. LC capilliposide could also reduce protein levels of Ku80 and Ku70, which are key elements for NHEJ pathway. Knocking-down of DNA-pKcs expression with targeting siRNA eliminated inhibitory effects of LC capilliposide on cell survival after irradiation treatment. Pretreatments with LC capilliposide resulted in the significantly higher percentage of cells with residual γ-H2A.X foci in cells after irradiation, indicating that LC capilliposide could reduce the cellular capabilities to repair IR-induced DNA damage.In addition, our data showed that LC capilliposide decreased the invasion/migration capabilities of cancer cells.Conclusion Our results suggest a potential clinical impact for LC capilliposide as a radiosensitizer and as a part of chemoradiotherapy regimen for non-small-cell lung cancer. LC capilliposide also decreased the invasion/migration capabilities of cancer cells for non-small-cell lung cancer.